Double metal cyanide complex catalysts modified with Group IIA compounds

Highly active double metal cyanide complex catalysts useful for epoxide polymerization are prepared by reacting zinc chloride or other metal salt with potassium hexacyanocobaltate or other metal cyanide salt in the presence of a Group IIA compound such as calcium chloride.

FIELD OF INVENTION 
This invention relates to double metal cyanide complex catalysts which are 
modified by the incorporation of a cyanide-free Group IIA compound such as 
calcium chloride as well as to methods for the preparation of such 
catalysts. Epoxides may be polymerized using these modified catalysts to 
provide polyether polyols having low levels of unsaturation and/or high 
molecular weights. 
BACKGROUND OF THE INVENTION 
Double metal cyanide complex catalysts are known to be extremely useful and 
active catalysts for the ring-opening polymerization of heterocyclic 
monomers such as epoxides. In particular, catalysts of this type have been 
employed to prepare polyether polyols derived from propylene oxide as 
described, for example, in U.S. Pat. Nos. 3,404,109, 3,829,505, 3,900,518, 
3,941,849, 4,355,188, 5,032,671, and 4,472,560. Double metal cyanide 
complex catalysts are generally recognized as superior to the caustic 
catalysts traditionally used to produce polyether polyols for utilization 
in polyurethane foams, coatings, adhesives, sealants, and elastomers due 
to the reduced levels of unsaturation and higher functionality of the 
polyols obtained using such catalysts, as described in U.S. Pat. Nos. 
4,239,879, 4,242,490, and 4,985,491. 
The double metal cyanide complex catalysts are generally prepared by 
reacting a metal salt such as zinc chloride with an alkali metal 
hexacyanometallate such as potassium hexacyanocobaltate in aqueous 
solution. 
Workers in the field have generally believed that to obtain a double metal 
cyanide complex catalyst having satisfactory performance in epoxide 
polymerization it is necessary to use an amount of the metal salt which is 
greater than that required to completely react the alkali metal 
hexacyanometallate. For example, U.S. Pat. No. 5,158,922 (Hinney et al.), 
states the "t!o obtain a double metal cyanide complex catalyst having 
reproducibly high polymerization activity, it is critical that an excess 
of the water-soluble metal salt be employed relative to the amount of 
metal cyanide salt." According to this reference, a portion of the excess 
metal salt is retained in the catalyst upon isolation and appears to 
function as a promoter or co-catalyst. Later, as described in U.S. Pat. 
No. 5,627,122, it was found that catalysts containing a relatively small 
excess of metal salt, particularly those prepared using an alcohol such as 
tert-butyl alcohol as an organic complexing agent, offered certain 
advantages over catalysts containing a larger excess of metal salt. 
However, the metal salt still must be present in excess during the 
catalyst synthesis since double metal cyanide complex substances that 
contain no metal salt "are inactive as epoxide polymerization catalysts." 
While there has been considerable interest in further improving the 
performance of double metal cyanide complex catalysts by changing the 
identity of the organic complexing agent (see, for example, U.S. Pat. No. 
5,470,813) or by modifying the catalyst with a polyether (see, for 
example, U.S. Pat. No. 5,482,908) or zinc sulfate and/or acid (see, for 
example U.S. Pat. No. 4,472,560), the preparation of such catalysts using 
cyanide-free compounds of Group IIA elements such as calcium chloride has 
not heretofore been described. 
SUMMARY OF INVENTION 
This invention provides a double metal cyanide complex catalyst comprised 
of double metal cyanide and an organic complexing agent, wherein said 
double metal cyanide complex catalyst is modified with a Group IIA 
compound which is free of cyanide. Additionally, this invention provides a 
method of making a double metal cyanide complex catalyst comprising 
reacting a zinc salt with a metal cyanide salt in the presence of a Group 
IIA compound which is free of cyanide. 
The Group IIA compound must contain at least one element selected from 
Group IIA of the Periodic Table, is preferably water soluble and is 
characterized by the absence of cyanide. Thus, for example, alkaline earth 
metal hexacyanometallates are not suitable for use as the Group IIA 
compound component of this invention; such substances may, however, be 
utilized as the metal cyanide salt starting material in the methods for 
synthesizing the modified double metal cyanide complex catalysts described 
herein. The Group IIA compound may contain one or more of the Group IIA 
elements. Calcium is the most preferred Group IIA element. The identity of 
the portion of the Group IIA compound other than the Group IIA element is 
not thought to be critical and may be, for example, halide (e.g., 
chloride), nitrate, sulfate, hydroxide or the like. For convenience, as 
will be evident from the later discussion related to synthesis methods, 
the Group IIA compound will preferably be at least somewhat soluble in 
water or mixtures of water and the organic complexing agent. Calcium 
chloride is a particularly preferred Group IIA compound for use in the 
present invention. Combinations of Group IIA compounds may be used to 
advantage if so desired such as, for example, calcium chloride and calcium 
oxide. 
The synthesis of the modified double metal cyanide complex catalysts of 
this invention may be effected by reacting a metal salt with a metal 
cyanide salt in the presence of the Group IIA compound. 
The metal salt has the general empirical formula M.sup.1 (X).sub.n, wherein 
M.sup.1 is selected from the group consisting of Zn(II), Fe(II), Ni(II), 
Mn(II), Co(II), Sn(II), Pb(II), Fe(III), Mo(Iv), Mo(VI), Al(III), V(IV), 
Sr(II), W(VI), Cu(II), and Cr(III). Preferably M.sup.1 is either Zn(II), 
Fe(II), Co(II), or Ni(II), as double metal cyanide complex catalysts 
containing these metals tend to have the highest polymerization activity 
and yield polymeric products having relatively low polydispersity. Most 
preferably, M.sup.1 is Zn(II). The metal salt preferably has a solubility 
in water at 25.degree. C. of at least about 10 g per 100 g water. Mixtures 
of different water-soluble metal salts may be employed if desired. X is an 
anion selected from the group consisting of halide (e.g., fluoride, 
chloride, bromide, iodide), hydroxide (OH), sulphate (SO.sub.4), carbonate 
(CO.sub.3,CO.sub.3 H), cyanide (CN), thiocyanate (SCN), isocyanate (NCO), 
isothiocyanate (NCS), carboxylate (e.g., acetate, propionate), oxalate, or 
nitrate (NO.sub.3). The value of n is selected to satisfy the valency 
state of M.sup.1 and typically is 1, 2, or 3. The zinc halides, 
particularly zinc chloride, are particular preferred for use; zinc sulfate 
and zinc nitrate are specific examples of other suitable metal salts. 
The metal cyanide salt preferably is water--soluble as well and has the 
general formula (Y).sub.a M.sup.2 (CN).sub.b (A).sub.c wherein M.sub.2 is 
the same as or different from M.sup.1 and is selected from the group 
consisting of Fe(II), Fe(III), Co(III), Cr(III), Mn(II), Mn(III), Ir(III), 
Rh(III), Ru(II), V(IV), V(V), Co(II), and Cr(II). Preferably M.sup.2 is 
either Co(II), Co(III), Fe(II), Fe(III), Cr(III), Ir(lIl), or Ni(II) as 
catalysts containing these metals tend to have the highest polymerization 
activity and to yield polyether polyols having desirably narrow molecular 
weight distributions (e.g., low polydispersity). Most preferably M.sup.2 
is Co(II). More than one metal may be present in the metal cyanide salt, 
e.g., potassium hexacyanocobaltate (II) ferrate (II). Mixtures of 
different water-soluble metal cyanide salts may be employed, if desired. Y 
is an alkali metal (e.g., Li, Na, K) or alkaline earth metal (e.g., Ca, 
Ba). A is a second anion that may be the same as or different from X in 
the metal salt and may be selected from the group consisting of halide, 
hydroxide, sulfate, and the like. Both a and b are integers of 1 or 
greater, wherein a, b, and c are selected so as to provide the overall 
electroneutrality of the metal cyanide salt. Preferably, c is 0. In most 
instances, b corresponds to the coordination number of M.sup.2 and is 
usually 6. Examples of suitable water-soluble metal cyanide salts useable 
in the process of this invention include, but are not limited to, 
potassium hexacyanocobaltate (III) (the preferred metal cyanide salt), 
potassium hexacyanoferrate (ii), potassium hexacyanoferrate (III), 
potassium hexacyanocobalte (II) ferrate (II), sodium hexacyanocobaltate 
(III), sodium hexacyanoferrate (II), sodium hexacyanoferrate (III), 
potassium hexacyanoruthenate (II), calcium hexacyanocobaltate (III), 
potassium tetracyanonickelate (II), potassium hexacyanochromate (III), 
potassium hexacyanoiridate (III), calcium hexacyanoferrate (II), potassium 
hexacyanocobaltate (II), calcium hexacyanoferrate (III), and lithium 
hexacyanocobaltate (III). 
Although a stoichiometric excess of the metal salt relative to the metal 
cyanide salt could be utilized if so desired, a distinguishing feature of 
this invention is that double metal cyanide complex catalysts which have 
high epoxide polymerization activity and are capable of providing 
polyether polyols of low polydispersity and low unsaturation may be 
prepared using a stoichiometric amount of metal salt or less. When zinc 
chloride is the metal salt and potassium hexayanocobaltate is the metal 
cyanide salt, for example, the molar ratio of zinc chloride: potassium 
hexacycanocobaltate may be about 1.5:1 or lower (with the ratio of 1:1 
being the preferred lower limit) since the stoichiometric reaction of 
these reagents requires a 1.5:1 molar ratio. This was quite surprising in 
view of the widely held belief in the prior art that at least a minor 
excess of the metal salt was required in order to attain satisfactory 
catalyst performance. 
While the precise method by which the metal salt and the metal cyanide salt 
are reacted is not believed to be critical, it is important that the Group 
IIA compound be present during such reaction in order to favor 
incorporation of the Group IIA compound into the double metal cyanide 
complex catalyst which forms. Typically, it will be convenient to combine 
separate aqueous solutions of the metal salt and the metal cyanide salt 
with the Group IIA compound being additionally present in one or both of 
the aqueous solutions. 
The reactants are combined at any desired temperature. Preferably, the 
catalyst is prepared at a temperature within the range of about room 
temperature to about 80.degree. C.; a more preferred range is from 
35.degree. C. to about 60.degree. C. Generally speaking, the double metal 
cyanide complex catalyst which is formed precipitates from solution in 
particulate form. 
The organic complexing agent and optional functionalized polymer (both to 
be described later in more detail) can be included with either or both of 
the aqueous solutions, or they can be added to the catalyst slurry 
immediately following precipitation of the double metal cyanide complex. 
It is generally preferred to pre-mix the complexing agent with either 
aqueous solution, or both, before combining the reactants. If the 
complexing agent is added to the catalyst precipitate instead, then the 
reaction mixture should be mixed efficiently with a homogenizer or a 
high-shear stirrer to produce the most active form of the catalyst. It is 
generally preferred to add functionalized polymer following precipitation 
of the double metal cyanide complex catalysts. The catalyst is then 
usually isolated from the catalyst slurry by any convenient means, such as 
filtration, centrifugation, decanting, or the like. 
The isolated catalyst is preferably washed with an aqueous solution that 
contains additional organic complexing agent and/or additional 
functionalized polymer. After the catalyst has been washed, it is usually 
preferred to dry it under vacuum until the catalyst reaches a constant 
weight. 
Double metal cyanide complex catalysts made by the process of the invention 
include an organic complexing agent. Generally, the complexing agent is 
soluble in water. Suitable complexing agents are those commonly known in 
the art, as taught, for example, in U.S. Pat. No. 5,158,922. The 
complexing agent may be added either during preparation or immediately 
following precipitation of the catalysts. Usually, an excess amount of the 
complexing agent is used. Preferred complexing agents are water-soluble 
heteroatom-containing organic compounds that can complex with the double 
metal cyanide compound. Suitable complexing agents include, but are not 
limited to, alcohols, aldehydes, ketones, ethers, esters, amides, ureas, 
nitrites, sulfides, and mixtures thereof. Preferred complexing agents are 
water-soluble aliphatic alcohols, particularly those selected from the 
group consisting of ethanol, isopropyl alcohol, n-butyl alcohol, isobutyl 
alcohol, sec-butyl alcohol, and tert-butyl alcohol. Tert-butyl alcohol is 
most preferred. Another class of preferred organic complexing agents 
includes the water-soluble mono and di-alkyl ethers of glycols and glycol 
oligomers such as, for example, glyme, diglyme, and the like. 
Catalysts made by the process of the invention optionally include a 
functionalized polymer or its water-soluble salt. By "functionalized 
polymer" we mean a polymer that contains one or more functional groups 
containing oxygen, nitrogen, sulfur, phosphorus, or halogen, wherein the 
polymer, or a water-soluble salt derived from it, has relatively good 
water solubility, i.e., at least about 3 wt.% of the polymer or its salt 
dissolves at room temperature in water or mixtures of water with a 
water-miscible organic solvent. Examples of water-miscible organic 
solvents are tetrahydrofuran, acetone, acetonitrile, t-butyl alcohol, and 
the like. Water solubility is helpful for convenient incorporation of the 
functionalized polymer into the catalyst structure during formation and 
precipitation of the double metal cyanide compound. 
Functionalized polymers may have the general structure: 
##STR1## 
in which R' is hydrogen, --COOH, or a C.sub.1 -C.sub.5 alkyl group, and A 
is one or more functional groups selected from the group consisting of 
--OH, --NH.sub.2, --NHR, --NR.sub.2, --SH, --SR, --COR, --CN, --Cl, --Br, 
--C.sub.6 H.sub.4 --OH, --C.sub.6 H.sub.4 --C(CH.sub.3).sub.2 OH, 
--CONH.sub.2, --CONHR, --CO--NR.sub.2, --OR, --NO.sub.2, --NHCOR, --NRCOR, 
--COOH, --COOR, --CHO, --OCOR, --COO----OH, --SO.sub.3 H, --CONH--R--SOH, 
pyridinyl, and pyrrolidonyl, in which R is a C.sub.1 -C.sub.5 alkyl or 
alkylene group, and wherein n has a value within the range of about 5 to 
about 5,000. 
Optionally, the functionalized polymer also includes recurring units 
derived from a non-functionalized vinyl monomer such as an olefin or 
diene, e.g., ethylene, propylene, butylenes, butadiene, isoprene, styrene, 
or the like, provided that the polymer or a salt derived from it has 
relatively good solubility in water or mixtures of water and a 
water-miscible organic solvent. 
Suitable functionalized polymers include, for example, poly(acrylamide), 
poly(acrylamide-co-acrylic acid), poly(acrylic acid), 
poly(2-acrylamide-2-methyl-a-propanesulfonic acid), poly(acrylic 
acid-co-maleic acid), poly(acrylonitrile), poly(alkyl acrylate)s, 
poly(alkyl methacrylate)s, poly(vinyl methyl ether), poly(vinyl ethyl 
ether), poly(vinyl acetate), poly(vinyl alcohol), 
poly(N-vinylpyrrolidone), poly(N-vinylpyrrolidone-co-acrylic acid), 
poly(N,N-dimethylacrylamide), poly(vinyl methyl ketone), 
poly(4-vinylphenol), poly(4-vinylpyridine), poly(vinyl chloride), 
poly(acrylic acid-co-styrene), poly(vinyl sulfate), poly(vinyl sulfate) 
sodium salt, and the like. 
Suitable functionalized polymers also include polyethers. Catalysts that 
incorporate a polyether are taught in U.S. Pat. Nos. 5,482,908 and 
5,545,601, the teachings of which are incorporated herein by reference in 
their entirety. In one preferred embodiment of the invention, the 
functionalized polymer is a polyether polyol. Preferably, the polyether 
polyol has a number average molecular weight in excess of 500. 
Polypropylene glycols having a functionality of 2 or 3 are especially 
useful for this purpose. 
The catalyst obtained by the process of this invention may be used in any 
of the polymerization reactions known in the art wherein double metal 
cyanide complex catalysts have been employed. The catalysts are 
particularly suitable for use in catalyzing the polymerization of epoxides 
such as propylene oxide onto active hydrogen-containing initiators 
(telogens) to yield polyether polyols. Such reactions are described, for 
example, in U.S. Pat. Nos. 3,427,256, 3,427,334, 3,427,335, 3,301,796, 
3,442,876, 3,278,457, 3,278,458, 3,279,459, 3,404,109, 3,829,505, 
3,900,518, 3,941,849, 4,355,188, 3,538,043, 3,576,909, 4,279,798, 
5,032,671, 3,726,840, and 4,472,560 as well as EP 222,453, and East German 
Pat. Nos. 148,957, 203,734, and 203,735, the teachings of which are 
incorporated herein by reference in their entirety. 
The precise chemical structures and compositions of double metal cyanide 
complex catalysts ob tain ed by practice of this invention are not known, 
although by elemental analysis it appears that the Group IIA compound is 
incorporated in some form into the catalyst. Some reaction of the Group 
IIA compound with the other inorganic starting materials used in the 
process may also be taking place. Typically, the composition of the 
catalyst will be such that the Group IIA content (calculated as the 
element) will be in the range of from about 0.1 to 10 weight percent. 
Certain amounts of organic complexing agent, functionalized polymer, and 
water, will generally also be present in addition to the double metal 
cyanide itself, wherein the relative proportions of these components are 
typically similar to those found in double metal cyanide complex catalysts 
described in the prior art (including the patents referenced herein). As 
discussed earlier, variable amounts of metal salt (e.g., zinc chloride) 
may also be present.

Without further elaboration, it is believed that one skilled in the art 
can, using the preceding description, utilize the present invention to its 
fullest extent. The following examples therefore, are to be considered as 
merely illustrative and not limitative of the claims or remainder of the 
disclosure in any way whatsoever. 
EXAMPLES 
The relative activity of each of the double metal cyanide complex catalysts 
described herein was evaluated by calculation of an apparent rate constant 
(K.sub.app) for propylene oxide polymerization. The method used for the 
calculation involves monitoring the drop in propylene oxide partial 
pressure during the cookout or soak period of a batch polymerization run 
(i.e., the period after incremental propylene oxide addition to the 
reaction mixture has been completed) and assumes that there is rapid 
equilibration of the unreacted propylene oxide between the liquid and 
vapor phases relative to polymerization. When the natural logarithm of the 
propylene oxide concentration (partial pressure) is plotted as a function 
of time, a straight line is obtained. This indicates the propylene oxide 
consumption is first order with respect to propylene oxide concentration. 
The slope of the straight line is the apparent rate constant K.sub.app, 
which should be related to the time rate constant K by the equation 
K.sub.app =Kcat*!.sup.n. The expression cat* represents the actual 
concentration of active catalyst centers, which may not be equal to the 
catalyst concentration. 
Example 1 
This example demonstrates the preparation of a calcium chloride-modified 
zinc hexacyanocobaltate complex catalyst in accordance with the invention. 
A 3 L kettle equipped with baffles, impeller and heating mantle is charged 
with 472.77 g deionized water. The agitation rate of the impeller is set 
at 150 rpm. Calcium chloride dihydrate (163.74 g) obtained from Aldrich 
Chemical Company (98+% purity) is added, followed by 230.23 deionized 
water to wash the kettle walls free of any residual calcium chloride 
dihydrate. Zinc chloride (9.24 g) obtained from Aldrich Chemical Company 
(98+% purity) is then added and the kettle walls washed again with 346.02 
g deionized water. After raising the agitation rate to 200 rpm, 165.45 g 
tert-butyl alcohol is added to the kettle. 
The following mixture is prepared separately. A 1 L glass beaker is charged 
with 193.4 g deionized water. While the contents of the beaker are gently 
mixed using a poly(perfluoroethylene) coated stir bar, 160.0 g calcium 
chloride dihydrate is added causing the temperature of the water to 
increase to 47.degree. C. While heating to 50-60.degree. C., 0.3007 g 
calcium oxide (Aldrich, 99.9%) is added. The mixture is stirred for 80 
minutes while cooling to 31.degree. C. Thereafter, 232.2 g deionized water 
and 14.80 g potassium hexacyanocobaltate are added to yield a clear 
slightly yellow mixture. 
The contents of the 3 L kettle are heated to 50.degree. C. and agitated at 
a rate of 400 rpm. Addition of the potassium hexacyanocobaltate solution 
to the kettle is commenced using a syringe pump at a rate of ca. 5 g/min. 
After addition is completed, mixing of the kettle contents is continued 
for another 20 minutes. 
In a plastic beaker containing a poly(perfluoroethylene) coated stir bar, a 
solution of 15.80 g 1000 molecular weight polypropylene glycol diol, 4.00 
g tert-butyl alcohol and 62.00 g deionized water is prepared. After 
stirring vigorously for 3 minutes, this solution is added to the contents 
of the kettle. After stirring briefly, the contents of the kettle are 
transferred to a pressure filter having 5 micron filter paper and filtered 
at 20 psig. The solids removed from the filter (90.6 g) are resuspended in 
a premixed solution of 101 g tert-butyl alcohol and 55 g deionized water 
and mixed for about 10 minutes before placing the resulting suspension in 
a 1 L round bottom flask. The suspension is heated to 50.degree. C. and 
mixing continued for another 60 minutes thereafter before adding 2.05 g of 
the 1000 molecular weight polypropylene glycol diol. After mixing for 
another 3 minutes, the mixture is press-filtered at 20 psig for 3 minutes 
yielding 63.6 g colorless slightly pasty solids. The solids are 
re-suspended in 144.0 g tert-butyl alcohol, mixed for 10 minutes and 
heated at 50.degree. C. for 60 minutes before adding 1.01 g of the 
polypropylene glycol diol to the suspension. After stirring briefly, the 
suspension is filtered through 5 micron filter paper to provide 44.7 g of 
wet solids. The calcium chloride-modified zinc hexacyanocobaltate complex 
catalyst (12.8 g) is obtained in final form by drying the wet solids 35 
hours in a 55.degree. C. vacuum oven. 
The catalyst by elemental analysis contains 18.7 wt. % Zn, 8.80 wt. % Co, 
10.9 wt. % Cl, and 4.47 wt. % Ca. 
Example 2 
This example demonstrates an alternative method of preparing a calcium 
chloride-modified zinc hexacyanocobaltate complex catalyst in accordance 
with the invention. 
A 3 L kettle equipped with baffles, impeller and heating mantle is charged 
with 638.0 g deionized water. The agitation rate of the impeller is set at 
150 rpm. Calcium chloride dihydrate (163.7g) is added, followed by 65 g 
deionized water to wash the kettle walls free of any residual calcium 
chloride dihydrate. Zinc chloride (9.27 g) is then added and the kettle 
walls washed again with 346 g deionized water. After raising the agitation 
rate to 500 rpm and increasing the temperature to 44.degree. C., 165.4 g 
tert-butyl alcohol is added to the kettle. 
After again increasing the temperature of the contents of the kettle to 
44.degree. C., an aqueous solution of potassium hexacyanocobaltate (14.8 
g) in water (232.0 g) is added using a syringe pump at a rate of 4.94 
g/min. 
Separately, a 500 ml glass beaker is charged with 193.0 g deionized water. 
While stirring the beaker contents with a stir bar, 160.18 g calcium 
chloride dihydrate is added gradually. The temperature is increased to 
54.degree. C., then 0.6 g calcium oxide is added all at once. The beaker 
is heated to 60.degree. C. while covered until all of the calcium oxide 
goes into solution, then stirred for another 20 minutes while cooling to 
53.degree. C. 
The calcium chloride/calcium oxide solution is added to the kettle using a 
syringe pump at an addition rate of 2.94 g/min. Once addition is completed 
(100 minutes), mixing is continued for another 20 minutes at 50.degree. C. 
A solution of 15.88 g 1000 molecular weight polypropylene glycol diol, 4.00 
g tert-butyl alcohol and 62.2 g deionized water is thereafter added to the 
kettle contents. After mixing briefly, the kettle contents are filtered 
through 5 micron filter paper (20 psig N.sub.2). The filter cake thus 
obtained is resuspended in a solution of 101 g tert-butyl alcohol and 55 g 
deionized water and stirred for 10 minutes before transferring to a 1 L 
round bottom flask and mixing at 300 rpm while heating to 50.degree. C. 
After 60 minutes, 2.03 g 1000 molecular weight polypropylene glycol diol 
is added to the flask and mixed briefly before refiltering through 5 
micron filter paper (20 psig N.sub.2). The resulting filter cake (33.6 g) 
is resuspended in 144.0 g tert-butyl alcohol and mixed for 10 minutes 
before transferring to a 1 L round bottom flask. The suspension was heated 
at 50.degree. C. for 65 minutes while stirring at 300 rpm. After adding 
1.01 g of the polypropylene glycol diol and mixing briefly, the suspension 
is refiltered (5 micron filter paper, 20 psig N.sub.2). The filter cake is 
dried overnight in a 550 vacuum oven to yield 12.3 g of the final calcium 
chloride-modified zinc hexacyanocobaltate complex catalyst. The elemental 
composition of the catalyst by analysis is 24.4 wt % Zn, 11.40 wt % Co, 
2.80 wt % Cl and 0.62 wt % Ca. 
Example 3 
This example demonstrates the polymerization of propylene oxide using the 
calcium chloride-modified zinc hexacyanocobaltate complex catalyst 
prepared in Example 1. The polymerization is performed by charging 680 g 
of a propoxylated glycerin starter (hydroxyl number =240 mg KOH/g) and 
0.071 g of the catalyst to a stirred pressure reactor, heating to 
130.degree. C. under a nitrogen blanket, and adding a total of 5029 g 
propylene oxide at an average feed rate of 20.3 g/minute over about 4 
hours. The final concentration of catalyst is 12.4 ppm. The apparent rate 
of reaction (K.sub.app) is 1.19. The polyether polyol triol thereby 
obtained has a hydroxy number of 27.9 mg KOH/g, an unsaturation level of 
0.0081 meq/g, and a viscosity of 1600 cst at 25.degree. C. 
Example4 
The polymerization of Example 3 is repeated, but using 0.143 g (25.0 ppm 
final catalyst concentration) of the calcium chloride-modified zinc 
hexacyanocobaltate complex catalyst prepared in Example 2. A total of 5030 
g propylene oxide is added at an average feed rate of 19.2 g/min over 
about 4.5 hours to obtain a polyether polyol triol having a hydroxyl 
number of 27.9 mg KOH/g, an unsaturation level of 0.0045 meq/g, and a 
viscosity of 1509 cst at 25.degree. C. The apparent rate (K.sub.app) is 
1.779 min.sup.-1. 
Example 5 
The procedure of Example 4 is repeated, but using 0.071 g catalyst (final 
catalyst concentration=12.4 ppm). A total of 5031 g propylene oxide is 
added over 4 hours at an average feed rate of 21.5 g/minute to obtain a 
polyether polyol triol having an hydroxyl number of 27.9 mg KOH/g, a 
viscosity of 1746 cst at 25.degree. C. and an unsaturation value of 0.0063 
meq/g. The apparent rate (K.sub.app) is 1.210 min.sup.-1.