Direct polyoxyalkylation of glycerine with double metal cyanide catalysis

Acidification, neutralization, or removal of basic impurities from acid sensitive low molecular weight starter or acidification of a reactor heel prior to addition of acid sensitive low molecular weight starter allows direct oxyalkylation of continuously added acid sensitive low molecular weight starter to produce polyoxyalkylene acid sensitive low molecular weight starter-initiated or co-initiated polyols in the presence of a double metal cyanide catalyst. The preferred acid sensitive low molecular weight starter is glycerine.

TECHNICAL FIELD 
The present invention pertains to preparation of polyoxyalkylene polyols by 
the direct oxyalkylation of glycerine and other oxyalkylatable low 
molecular weight initiator molecules by means of double metal cyanide 
catalysis. 
BACKGROUND ART 
Base-catalyzed oxyalkylation has been used to prepare polyoxyalkylene 
polyols for many years. In base catalyzed oxyalkylation, a suitably hydric 
low molecular weight starter molecule such as propylene glycol or 
glycerine is oxyalkylated with alkylene oxide, for example ethylene oxide 
or propylene oxide, to form a polyoxyalkylene polyether polyol product. 
Because it is possible to employ a low molecular weight starter, the build 
ratio (polyol weight/starter weight) is relatively high, and thus the 
process effectively utilizes reactor capacity. Strongly basic catalysts 
such as sodium hydroxide or potassium hydroxide are used in these 
base-catalyzed oxyalkylations. 
However, the bulk of polyoxyalkylene polyols useful in synthesis of 
polyurethane polymers as well as those suitable for other uses, contain 
substantial amounts of oxypropylene moieties. During base-catalyzed 
oxypropylation, a competing rearrangement of propylene oxide to allyl 
alcohol generates monofunctional species which also become oxyalkylated, 
producing a wide range of polyoxyalkylene monols with molecular weights 
ranging from that of allyl alcohol itself or its low molecular weight 
oxyalkylated oligomers to polyether monols of very high molecular weight. 
In addition to broadening the molecular weight distribution of the 
product, the continuous generation of monols lowers the product 
functionality. For example, a polyoxypropylene diol or triol of 2000 Da 
equivalent weight may contain from 30 to 40 mol percent monol. The monol 
content lowers the functionality of the polyoxypropylene diols produced 
from their "nominal," or "theoretical" functionality of 2.0 to "actual" 
functionalities in the range of 1.6 to 1.7. In the case of triols, the 
functionality may range from 2.2 to 2.4. As the oxypropylation proceeds 
further, the functionality continues to decrease, and the molecular weight 
growth rate slows. For these reasons, the upper practical limit for 
base-catalyzed polyoxypropylene polyol equivalent weight is just above 
2000 Da. Even at these modest equivalent weights, the products are 
characterized by low actual functionality and broad molecular weight 
distribution. 
The monol content of polyoxyalkylene polyols is generally determined by 
measuring the unsaturation, for example by ASTM D-2849-69, "Testing of 
Urethane Foam Polyol Raw Materials", as each monol molecule contains 
allylic termination. Levels of unsaturation of about 0.060 meq/g to in 
excess of 0.10 meq/g for based-catalyzed polyols such as those just 
described are generally obtained. Numerous attempts have been made to 
lower unsaturation, and hence monol content, but few have been successful. 
In the early 1960's, double metal cyanide complexes such as the 
non-stoichiometric glyme complexes of zinc hexacyanocobaltate were found 
to be able to prepare polyoxypropylene polyols with low monol contents, as 
reflected by unsaturation in the range of 0.018 to 0.020 meq/g, a 
considerable improvement over the monol content obtainable by base 
catalysis. However, the catalyst activity, coupled with catalyst cost and 
the difficulty of removing catalyst residues from the polyol product, 
prevented commercialization. In the 1980's, interest in such catalysts 
resurfaced, and improved catalysts with higher activity coupled with 
improved methods of catalyst removal allowed commercialization for a short 
time. The polyols also exhibited somewhat lower monol content, as 
reflected by unsaturations in the range of 0.015 to 0.018 meq/g. However, 
the economics of the process were marginal, and in many cases, 
improvements expected in polymer products due to higher functionality and 
higher polyol molecular weight did not materialize. 
Recently, researchers at the ARCO Chemical Company developed double metal 
cyanide complex catalysts ("DMC" catalysts) with far greater activity than 
ever before. 
These catalysts, as disclosed in U.S. Pat. Nos. 5,470,813 and 5,482,908, 
incorporated herein, have again allowed commercialization under the 
tradename ACCLAIM.TM. polyether polyols. However, unlike the low 
unsaturation (0.015-0.018 meq/g) polyols prepared by prior DMC catalysts, 
the new, ultra-low unsaturation polyols often demonstrate dramatic 
improvements in polymer properties, although formulations are often 
different from the formulations useful with conventional polyols. These 
polyols typically have unsaturation in the range of 0.002 to 0.008 meq/g. 
One of the drawbacks of DMC catalyzed oxyalkylation is the difficulty of 
using low molecular weight starters in polyether synthesis. 
Polyoxyalkylation of low molecular weight starters is generally sluggish, 
and often accompanied by catalyst deactivation. Thus, rather than 
employing low molecular weight starter molecules directly, oligomeric 
starters are prepared in a separate process by base catalyzed 
oxypropylation of a low molecular weight starter to equivalent weights in 
the range of 200 Da to 700 Da or higher. Further oxyalkylation to the 
target molecular weight takes place in the presence of DMC catalysts 
However, strong bases deactivate DMC catalysts. Thus, the basic catalyst 
used in oligomeric starter preparation must be removed by methods such as 
neutralization, adsorption, ion exchange, and the like. Several such 
methods require prolonged filtration of viscous polyol. The additional 
steps associated with catalyst removal from the oligomeric starter add 
significant process time and cost to the overall process. Furthermore, the 
higher molecular weight of the starter lowers the build ratio of the 
process significantly, thus decreasing reactor utilization. 
A further observation connected with oxyalkylation with DMC catalysts is 
that a very high molecular weight component is generally observed. The 
bulk of DMC catalyzed polyol product molecules are contained in a 
relatively narrow molecular weight band, and thus DMC-catalyzed polyols 
exhibit very low polydispersities, generally 1.20 or less. However, it has 
recently been discovered that a very small fraction of molecules, i.e. 
less than 1000 ppm, have molecular weights in excess of 100,000 Da. This 
very small but very high molecular weight fraction is thought to be 
responsible for some of the anomalous properties observed with ultra-low 
unsaturation, high functionality polyols. These ultra high molecular 
weight molecules do not significantly alter the polydispersity, however, 
due to the extremely small amounts present. 
In copending U.S. patent application Ser. Nos. 08/597,781 and 08/683,356, 
herein incorporated by reference, it is disclosed that the high molecular 
weight "tail" in polyoxypropylene polyols may be minimized by continuous 
addition of starter during oxyalkylation. In batch and semi-batch 
processes, low molecular weight starter, e.g., propylene glycol or 
dipropylene glycol, is added continuously as the polyoxyalkylation 
proceeds rather than all being added at the onset. The continued presence 
of low molecular weight species has been found to lower the amount of high 
molecular weight tail produced, while also increasing the build ratio, 
since a large proportion of the final polyol product is derived from low 
molecular weight starter itself. Surprisingly, the polydispersity remains 
low, contrary to an expected large broadening of molecular weight 
distribution. In the continuous addition process, continuous addition of 
starter during continuous rather than batch production was found to also 
result in less low molecular weight tail, while allowing a build ratio 
which approaches that formerly obtainable only by traditional semi-batch 
processing employing base catalysis. 
Unfortunately, it has been observed that when glycerine, a widely used 
trifunctional starter, is employed in either the batch-type continuous 
addition of starter process, or the continuous-type continuous addition of 
starter process, the DMC catalyst gradually deactivates, and often a 
polyether of the desired molecular weight cannot be obtained, or when 
obtained, product characteristics such as amount of high molecular weight 
tail, polydispersity, etc., are less than optimal. This has been found to 
be the case even when the glycerine addition is relatively slow, but is 
exacerbated when the glycerine addition rate is increased, as may happen 
during commercial production by normal or abnormal process excursions, 
pump failure, and the like. 
It would be desirable to be able to utilize low molecular weight starter 
molecules for polyol production using DMC catalysis. It would further be 
desirable to prepare DMC-catalyzed polyols with minimal high molecular 
weight tail components. It would be further desirable to prepare 
polyoxyalkylation polyols in high build ratios. However, these objectives 
cannot be met if catalyst deactivation occurs. 
SUMMARY OF THE INVENTION 
The present invention pertains to a process for the preparation of 
polyoxyalkylene polyols by the DMC-catalyzed oxypropylation of glycerine 
and other low molecular weight initiator molecules by continuous addition 
of the low molecular weight initiator in either a continuous or batch 
process. It has been surprisingly and unexpectedly discovered that 
continuous and batch processes involving continuous addition of starter 
may be practiced without deactivation, if the low molecular weight 
starter, or alternatively, the reactor heel, as hereinafter defined, are 
treated so as to remove or deactivate traces of residual bases which 
accumulate during synthesis or handling of certain low molecular weight 
starters, particularly glycerine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The subject process involves the continuous addition of low molecular 
weight starter to an oxyalkylation employing double metal cyanide 
catalysts as the oxyalkylation catalyst. The process may be conducted as a 
semi-batch process or as a continuous addition process. In either case, 
either the low molecular weight starter feed, the process heel, or other 
process stream is acidified such that the level of basic impurities are 
less than an amount effective to decrease catalyst activity. The required 
amount of acid is generally in the low ppm range relative to the weight of 
low molecular weight starter. 
In the subject invention process, polyoxyalkylene polyols are prepared by 
oxyalkylation of one or more suitably hydric low molecular weight 
initiators, preferably glycerine, in the presence of a double metal 
cyanide complex catalyst (DMC catalyst) In conventional batch processes 
employing DMC catalysts, the entire initiator (starter) is added initially 
to the reactor, DMC catalyst added, and a small percentage of the alkylene 
oxide feed added. A significant pressure drop signifies that the catalyst 
has been activated. Alternatively, a preactivated master batch of catalyst 
mixed with initiator may be used. The reactor temperature is generally 
maintained at temperatures between 70.degree. C. and 150.degree. C., and 
the remainder of propylene oxide added at relatively low pressure, i.e. 
less than 10 psig. In the conventional process, oligomeric starters having 
an equivalent weights in the range of 200-700 Da or higher are generally 
used. For glycerine polyols, for example, molecular weights of 700 Da to 
1500 Da are preferred. Equivalent weights and molecular weights herein in 
Da (Daltons) are number average equivalent weights and molecular weights 
unless indicated otherwise. 
In the conventional process, by way of example, the preparation of a 3000 
Da molecular weight polyoxypropylated glycerine triol may be achieved 
through oxypropylation of a 1500 Da molecular weight oligomeric 
oxypropylated glycerine starter until a molecular weight of 3000 Da is 
achieved. The build ratio is 3000 Da/1500 Da or 2.0. This low build ratio 
cannot efficiently take advantage of reactor capacity, as some 40 percent 
of the total reactor capacity is used for starter alone. In addition, the 
product will have a small, but significant amount of a very high molecular 
weight (&gt;100,000 Da) fraction. This high molecular weight fraction 
("tail") is believed to contribute to foam collapse in some polyurethane 
systems. 
In the continuous addition of starter process, polyoxyalkylation is 
accomplished by addition of a smaller amount of oligomeric starter 
together with catalyst and initial alkylene oxide for activation as in the 
conventional process. However, in the continuous addition of starter 
process, low molecular weight starter is added in addition to alkylene 
oxide, preferably as a mixed reactor feed stream. The amount may be 1.8 
weight percent based on the weight of the combined low molecular weight 
starter/alkylene oxide stream, as a non-limiting example. As a result of 
the use of lesser amounts of oligomeric starter and continuous 
introduction of low molecular weight "monomeric" starter, a glycerine 
polyol of 3000 Da molecular weight may be prepared at higher build ratios, 
for example, a build ratio of 5. The process efficiency is increased by 
approximately 100 percent based on propylene oxide usage. The product also 
exhibits less high molecular weight tail. 
The continuous addition of starter process just described works well with 
low molecular weight starters such as propylene glycol and dipropylene 
glycol. However, when glycerine, a common trihydric starter, is used in 
the continuous addition of starter process, the catalyst often partially 
or fully deactivates, as shown by an increase in propylene oxide pressure 
in the reactor. The reaction slows or substantially ceases, and the 
product may not reach the desired molecular weight. Products are found to 
have broad polydispersities, and a relatively higher amount of high 
molecular weight tail. 
It has now been surprisingly discovered that addition of very small amounts 
of acid to the glycerine initiator prior to its introduction into the 
reactor as continuously added starter allows use of glycerine to produce 
polyols of high molecular weight without catalyst deactivation, without 
increasing the amount of high molecular weight tail or increasing polyol 
polydispersity. The same, or sometimes superior results may be obtained by 
acidifying the reactor heel rather than glycerine. Without wishing to be 
bound by any particular theory, it is believed that glycerine may contain 
basic impurities associated with its manner of production, which is 
generally by the base-catalyzed hydrolysis of triglycerides derived from 
animal fats or vegetable oils. It is known that bases deactivate DMC 
catalysts. Thus, addition of acid is a preferable manner of preventing 
deactivation of DMC catalysts during oxyalkylation of glycerine DMC 
catalysis. Other methods of elimination of basic substances or other 
acid-reactive substances from glycerine so as to prevent catalyst 
deactivation include adsorption by acid adsorbents, or by ion-exchange to 
either neutralize the impurities or to exchange them for acidic moieties. 
The preferred method of elimination of basic substances is by addition of 
acid. 
Low molecular weight starters useful in the present process include those 
having molecular weights below about 400 Da, preferably below 300 Da, 
which contain basic, DMC catalyst-deactivating impurities. Non-limiting 
examples of such low molecular weight starter molecules include glycerine, 
diglycerol, and polyglycerol, all of which are generally prepared through 
the use of strong bases. Glycerine is generally obtained by the 
hydrolysis, or "saponification" of triglycerides, while diglycerol and 
polyglycerol may be obtained by base-catalyzed condensation of glycerine. 
Further examples of suitable low molecular weight starter molecules 
include various methylolated phenols and similar products prepared by the 
base-catalyzed reaction of formaldehyde with urea, phenol, cresol, and the 
like. 
The suitability of a particular low molecular weight starter for use in the 
present invention may be ascertained by polyoxypropylating non-acidified 
(and "non-treated" as described below) starter employing DMC catalysis and 
normal polyoxyalkylation conditions, e.g., at 110-120.degree. C. and 10 
psig propylene oxide pressure. An oligomeric starter, preferably one which 
has been itself prepared by DMC catalysis, or which has been carefully 
refined to remove basic catalyst residues is introduced into the reactor, 
the DMC catalyst added and activated as described herein and in the 
aforementioned patents, and the proposed starter added slowly to the 
reactor as polyoxypropylation proceeds, either admixed with alkylene 
oxide, as a separate reactant stream, or admixed with another stream, for 
example, a product recycle stream. 
If the alkylene oxide pressure rises to a high level, indicating that 
catalyst deactivation has occurred, then the low molecular weight starter 
should be retested following base removal/neutralization of the low 
molecular weight starter. For example, the proposed starter may be 
acidified as described herein, or treated with an acidic ion exchange 
resin or other base removal method, i.e., contact with a base-reactive 
substance such as phosgene or thionyl chloride. Alternatively, the reactor 
"heel," i.e., the oligomeric starter mixture used to initiate the reaction 
may be acidified. If the same low molecular weight starter is the 
oxyalkylatable without premature catalyst deactivation after having been 
acidified or otherwise "treated" as described herein, then the low 
molecular weight starter is an "acid sensitive" starter as that term is 
used herein. 
Acids useful in neutralization include the mineral acids and the organic 
carboxylic acids, phosphonic acids, sulfonic acids, and other acids. 
Phosphoric acid is preferred as a mineral acid during oxyalkylation of 
glycerine, while citric acid and 1,3,5-benzene tricarboxylic acids may be 
useful as organic acids. Acid derivatives which are reactive with bases, 
such as acid chlorides and acid anhydrides and the like, are also useful. 
Organic acids such as phosphonic acids, sulfonic acids, e.g. 
p-toluenesulfonic acid, and the like, may also be used. Examples of 
mineral acids which are suitable include hydrochloric acid, hydrobromic 
acid, and sulfuric acid, among others, while useful carboxylic acids or 
their acidifying derivatives include formic acid, oxalic acid, citric 
acid, acetic acid, maleic acid, maleic anhydride, succinic acid, succinic 
anhydride, adipic acid, adipoyl chloride, adipic anhydride, and the like. 
Inorganic acid precursors such as thionyl chloride, phosphorous 
trichloride, carbonyl chloride, sulfur trioxide, thionyl chloride 
phosphorus pentoxide, phosphorous oxytrichloride, and the like are 
considered as mineral acids herein. These lists are illustrative and not 
limiting. 
Adsorbents which may be used are non-basic adsorbents, i.e. adsorbents 
which will adsorb basic substances and not leave appreciable residues 
derived from the adsorbent itself into the polyol. Examples of adsorbents 
include activated carbon, magnesium silicate, acid alumina, acid silica, 
and the like. Enough adsorbent must be used to remove the basic 
impurities. With some adsorbents, e.g. activated carbon, the amount 
required may be prohibitive, although lesser amounts can be utilized in 
conjunction with other treatments. Whether an amount consistent with the 
purpose of the invention has been used can be verified by the test for low 
molecular weight starter deactivating activity as herein described. 
Ion exchange resins suitable are preferably acid type ion exchange resins 
which are regenerated by washing the resin with strong acid between uses. 
For example, acrylic and styrenic resins with sulfonate, phosphonate, or 
carboxylate groups, preferably in their acid form, may be used. Suitable 
resins are commercially available, for example from Rohm and Haas and from 
Dow Chemical. The low molecular weight starter may be agitated with the 
adsorbent or ion exchange resin and filtered, or preferably may be passed 
through an adsorbent or resin packed column. 
Preferably, however, an acid, more preferably a common mineral acid, is 
simply added to the glycerine and stirred. The glycerine, following the 
addition, is preferably stripped to remove traces of water which may be 
introduced with the acid or generated as a result of neutralization by the 
acid. Addition of acid is a preferable means of operation as it is 
inexpensive and rapid, and does not use any special techniques. In 
general, less than 100 ppm acid based on total low molecular weight 
starter need be added, preferably about 5 ppm to 50 ppm, and most 
preferably about 10 ppm to 30 ppm. 
By "continuous addition of starter" relative to the subject process is 
meant oxyalkylation in the presence of a DMC catalyst where a low 
molecular weight starter or a low molecular weight oligomeric 
oxyalkylation product thereof having a molecular weight of less than about 
400 Da, preferably less than 300 Da, and most preferably less than 200 Da, 
is added substantially continuously throughout a substantial portion of 
the oxyalkylation such that the reaction mixture contains a small portion 
of low molecular weight starter throughout the bulk of the oxyalkylation. 
In general, about 30 weight percent of the final polyether product will 
have been derived from the low molecular weight initiator rather than the 
higher molecular weight oligomeric starter, more preferably in excess of 
50 weight percent, and most preferably 70 weight percent or more. 
The low molecular weight, "acid sensitive" starter may be mixed with 
non-acid sensitive starters as well, e.g. ethylene glycol, propylene 
glycol, dipropylene glycol, trimethylolpropane, pentaerythritol, sorbitol, 
sucrose, and the like, to produce co-initiated polyether polyols. 
Reactions where an acid sensitive starter or a lower oligomer are added 
all at once to the reactor is not a "continuous addition of starter" 
process. However, it must be understood that a final portion of 
oxyalkylation may, if desired, be conducted without addition of low 
molecular weight starter. This "finishing" step allows for reduction of 
moderate molecular weight oligomers by providing sufficient reaction time 
for the last added low molecular weight starter to be oxyalkylated to a 
high molecular weight, thus minimizing polydispersity. 
In the continuous version of the continuous addition of starter process, 
the reaction may be initiated by use of an oligomeric starter, but once 
begun is continuously initiated by further oligomeric starter, preferably 
by recycle of an oligomer or polymer from a later stage of the reaction. 
Alkylene oxide together with glycerine or low molecular weight 
oxyalkylation product is added at various points along the reactor which 
may, for example, be a tubular reactor ("multi-point addition"). A 
continuous stirred tank reactor (CSTR) may also be used. 
In either the batch or continuous versions of the continuous addition of 
starter process, a "heel" may be used to initiate the reaction. This heel, 
in the case of a batch reaction, may be an oligomeric product prepared 
separately by DMC catalysis or other catalytic methods, may be an 
intermediate molecular weight takeoff from a batch reactor which is stored 
for later use, or may be a portion of fully oxyalkylated product. The 
unique nature of the continuous addition of starter process allows use of 
target weight product polyols as the heel without appreciably broadening 
molecular weight distribution of the product. Apparently, the rate of 
oxyalkylation of oxyalkylatable species is inversely proportional to the 
molecular weight or degree of oxyalkylation of the oxyalkylatable species, 
and thus low molecular weight species are oxyalkylated much more rapidly 
than higher molecular weight species. 
For the continuous process, a heel may be used from a separate storage tank 
as in the batch process, but to take full advantage of the fully 
continuous process, the heel is provided by a recycle takeoff from an 
intermediate or final product stream. In this manner, build ratios 
approaching those of base catalyzed batch oxyalkylations employing 
monomeric starters such as glycerine may be achieved after continuous runs 
of several days duration. 
Rather than treat the glycerine to acidify it or to remove basic 
impurities, the heel used in the process may be acidified. In such case, 
to the heel should generally be added an amount of acid equivalent to that 
which would be added mixed with glycerine. In the batch process, the 
entire amount of acid may be added conveniently at the beginning of the 
reaction, although it may be added in increments as well. In the 
continuous process, the addition of acid and its frequency of addition may 
be adjusted depending upon the amount and type of recycle and the 
intermixing characteristics of the reactor. For example, with plug flow 
reactors, it may be most desirable to add acid continuously to the heel. 
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. 
Critical Foam Formulation Testing 
The presence or absence of a deleterious high molecular weight tail in a 
polyoxypropylene polyol used in polyurethane foams may be assessed by 
employing the polyol in a highly stressed hand-mixed foam formulation. In 
this test, a foam prepared from a given polyol is reported as "settled" if 
the foam surface appears convex after blow-off and is reported as 
collapsed if the foam surface is concave after blow-off. The amount of 
collapse can be reported in a relatively quantitative manner by 
calculating the percentage change in a cross-sectional area taken across 
the foam. The foam formulation is as follows: polyol, 100 parts; water, 
6.5 parts; methylene chloride, 15 parts; Niax.RTM. A-1 amine-type 
catalyst, 0.03 parts; T-9 tin catalyst, 0.4 parts; L-550 polysiloxane 
surfactant, 0.5 parts. The foam is reacted with a mixture of 2,4- and 
2,6-toluenediisocyanate at an index of 110. The foam may be conveniently 
poured into a standard 1 cubic foot cake box, or a standard 1 gallon ice 
cream container. In this formulation, conventionally prepared, i.e. base 
catalyzed polyols having high secondary hydroxyl cause the foam to settle 
approximately 5-10%, whereas polyols prepared from DMC catalysts 
exhibiting high molecular weight tails as disclosed in the present 
invention, cause the foam to "collapse", by settling approximately 40-70% 
or more. 
Analytical Procedure for Determining High Molecular Weight Tail 
The analytical procedure useful for obtaining the quantity of high 
molecular weight tail in a given DMC catalyzed polyol is a conventional 
HPLC technique, which can easily be developed by one skilled in the art. 
The molecular weight of the high molecular weight fraction may be 
estimated by comparing its elution time from the GPC column with that of a 
polystyrene standard of appropriate molecular weight. For example, a 
polystyrene of 100,000 molecular weight has been found appropriate for 
most analyses As is known, the high molecular weight fraction elutes from 
the column more rapidly than lower molecular weight fractions, and to aid 
in maintaining a stable baseline, it is appropriate following the elution 
of the high molecular weight fraction, to divert the remainder of the HPLC 
eluate to waste, rather than allowing it to pass through the detector, 
overloading the latter. Although many suitable detectors may be utilized, 
a convenient detector is an evaporative light scattering detector such as 
those commercially available. 
In the preferred analysis method, a Jordi Gel DVB 10.sup.3 angstrom column, 
10.times.250 mm, 5 micron particle size is employed together with a mobile 
phase which consists of tetrahydrofuran flowing at a rate of 1.0 
milliliters per minute. The detector used is a Varex Model IIA evaporative 
light scattering detector with a detector heater temperature set at 
100.degree. C. and exhaust temperature of 60.degree. C., with a nitrogen 
flow of 40 milliliters per minute. Polystyrene stock solutions are made of 
a 591,000 molecular weight polystyrene by weighing 20 milligrams into a 
100 milliliter volumetric flask and diluting to the mark with 
tetrahydrofuran. This stock solution was utilized to prepare quantitative 
standards containing 2, 5, and 10 mg/L of polystyrene. A molecular weight 
calibration standard was prepared by weighing out 2 milligrams of 100,000 
molecular weight polystyrene into a 100 milliliter volumetric flask and 
dissolving and diluting to the mark with tetrahydrofuran. 
Polyol samples were prepared by weighing 0.1 gram of polyether into a 1 
ounce bottle, and adding tetrahydrofuran to the sample to bring the total 
weight of sample and tetrahydrofuran to 10.0 grams. The peak areas for the 
polystyrene standards are electronically integrated, and peaks for each 
candidate polyol are averaged. The average peak areas are used to plot the 
log of peak areas versus log of peak concentrations. The concentration of 
greater than 100,000 Da molecular weight polymer in the polyol sample in 
ppm may be given by the equation: 
EQU Concentration.sub.ppm =[(Concentration.sub.mg/L) (W.sub.t /W.sub.s)]/0.888, 
where Concentration.sub.mg/L is equal to the concentration of polymer in 
milligrams per liter, W.sub.t equals the total weight of sample plus 
solvent, W.sub.s equals the weight of sample, and 0.888 is the density of 
tetrahydrofuran. For example, if the concentration of the greater than 
100,000 Da molecular weight polymer fraction determined by the analysis is 
1.8 mg/L, and the concentration factor (W.sub.t /W.sub.s) is 100, and the 
concentration.sub.ppm is 203 ppm. 
EXAMPLES 1, 2, AND 3, COMATIVE EXAMPLES C1 and C2 
A series of oxypropylations employing continuous addition of starter were 
performed in 10 gallon and 300 gallon reactors. In each case, an amount of 
1500 Da molecular weight oxypropylated glycerine starter sufficient to 
provide a build ration of 5 was introduced into the reactor together with 
an amount of zinc hexacyanocobaltate complex DMC catalyst sufficient to 
provide a final catalyst concentration of 30 ppm in the final product. The 
1500 Da oligomeric starters are identified as second or third generation 
starters (two or three runs removed from KOH refined starter). Commercial 
glycerine was utilized. 
Following addition of oligomeric starter and catalyst, the reactor was 
stripped with a nitrogen sparge at a pressure of 5-30 mm Hg for 30-40 
minutes and a reactor temperature of 130.degree. C. Propylene oxide or a 
mixture of propylene oxide and ethylene oxide was introduced in an amount 
equivalent to 4-6 weight percent of the starter charge and the reactor 
pressure monitored to ensure catalyst activation had occurred. 
Pressure was allowed to drop to below 500 torr prior to restarting 
propylene oxide feed. Following activation, propylene oxide in a "red hot" 
build ratio was added to the reactor The "red hot" build ratio is defined 
as the ratio of the amount of propylene oxide added plus the initial 
starter weight to the initial starter weight. 
The "red hot" build ratio is necessary to ensure the catalyst is fully 
activated. After completing addition to the "red hot", build ratio, the 
remaining propylene oxide, containing 2.3-2.6 weight percent glycerine, 
was added continuously over a 6-6.5 hour period. The mixed 
glycerine/propylene oxide feed was continued to the end of the reaction. 
In some examples, glycerine, propylene oxide and ethylene oxide were 
co-fed. 
The hydroxyl number, unsaturation, and viscosity of each polyol were 
measured in accordance with standard methods. The polyol molecular weight 
distribution and polydispersity were measured and calculated by standard 
gel permeation chromatography techniques. Results are presented in Table 1 
and 2. The amount of high molecular weight tail is measured by gel 
permeation chromatography as well. 
TABLE 1 
______________________________________ 
Example 1 C1 
______________________________________ 
Target Mol. Wt. (Da) 
3000 3000 
Target OH # 56 56 
Initial Starter Mol. Wt. 1500 1500 
(Da) 
Initial Starter 3rd 2nd 
Generation generation generation 
Continuous Starter glycerine glycerine 
Build Ratio 5 5 
Red Hot Build Ratio 1.5 1.5 
Glycerine Conc. % 2.6 2.6 
(glyc/(PO + glyc)) 
Final Catalyst in Product 30 30 
(ppm) 
Agitation (bhp/Mgal) 8 8 
Phosphoric Acid in 20 0 
Starter (ppm) 
Stripping Pressure (mmHg) 30 5 
Stripping Temperature 130 130 
(.degree. C.) 
Stripping Time (min) 40 36 
Catalyst Activation 
Charge (Oxide/Starter) 5.5 6 
wt. % 
Feed time (hr) 6.5 6 
Measured OH # 54.7 68.2 
HMW Tail (ppm) 444 568 
Critical Foam Test pass fail 
Unsaturation (meq/g) 0.0037 0.0035 
Viscosity (cst) 624 573 
Polydispersity 1.11 1.75 
______________________________________ 
TABLE 2 
______________________________________ 
Example 2 C3 C2 
______________________________________ 
Target Mol. wt. (Da) 
3200 3200 3200 
Target OH # 52 52 52 
Initial Starter Mol. 1500 1500 1500 
Wt. (Da) 
Initial Starter 3rd 3rd 2nd 
Generation generation generation generation 
Continuous Starter glycerine glycerine glycerine 
Build Ratio 5 5 5 
Red Hot Build Ratio 1.5 1.5 1.5 
Glycerine Conc. % 
(glyc/(PO + glyc)) 2.3 2.5 2.3 
Final Catalyst in 
Product (ppm) 30 30 30 
Agitation (bhp/Mgal) 8 8 8 
Phosphoric Acid in 20 20 0 
Starter (ppm) 
Stripping Pressure 30 30 10 
(mmHg) 
Stripping Temperature 
(.degree. C.) 130 130 130 
Stripping Time (min) 40 40 30 
Catalyst Activation 
Charge (Oxide/Starter) 5.5 PO/EO 5.5 PO/EO 4 PO 
wt. % 
Feed time (hr) 6.5 6.5 6 
Measured OH # 51.3 49.9 67.0 
Unsaturation (meq/g) 0.0029 0.0026 0.0032 
Viscosity (cst) 651 665 554 
Polydispersity 1.12 1.12 1.31 
% EO 12 12.3 12.4 
______________________________________ 
In Examples 1, 2 and 3, the glycerine co-fed with propylene oxide was 
acidified prior to its admixture with propylene oxide by addition of 20 
ppm phosphoric acid. In Comparative Examples C1 and C2, no acidification 
was performed. The propylene oxide pressure during the five runs were 
plotted against time, and the plots illustrated in FIGS. 1 and 2. 
In the Figures, the plots are labeled consistent with the Examples. In 
plots C1 (FIG. 1) and C2 (FIG. 2), using non-acidified glycerine, the 
propylene oxide pressure began to rise almost immediately following the 
beginning of glycerine addition. In Comparative Example C1, a pressure of 
48 psia was reached about five hours after glycerine addition was begun, 
indicating that catalyst was deactivated. In Comparative Example C2, the 
propylene oxide pressure reached 43 psia, again indicating that the 
catalyst had been deactivated. The oxide feed was stopped and the catalyst 
eventually consumed the oxide. The oxide feed in Comparative Example C2 
was reinitiated and oxide pressure rapidly reached 33 psia after only 30 
minutes at which point the run was aborted due to catalyst deactivation. 
In Examples 1, 2 and 3, the glycerine was acidified prior to being co-fed 
to the reactor. Note that the propylene oxide pressure remained constant 
within approximately 5 psia for the bulk of the reaction. The Figures 
illustrate the dramatic improvement made available by acidifying the 
glycerine feed. Note that the small jag in the plot occurring at about 
three and one-half hours into the reaction represents contact of the 
second reactor impeller with the reactor contents, increasing the level of 
agitation. 
In addition to these dramatic differences in the respective acidified and 
non-acidified process, the polyols themselves are also significantly 
different when the glycerine feed is acidified. The Example 1 polyol 
(acidified glycerine feed) had a polydispersity (M.sub.w /M.sub.n) of only 
1.11 and about 444 ppm (average of two measurements) high molecular weight 
tail. The hydroxyl number was 54.7, and the unsaturation typical of that 
generated employing highly active DMC catalysts at about 0.0037 meq/g. The 
polyol in Example 1 passes the critical foam test with acceptable foam 
settle. 
By contrast, in the non-acidified Comparative Example C1, results are quite 
different. In Comparative Example C1, the catalyst deactivation is so 
severe that the desired molecular weight could not be achieved, as 
reflected by the high hydroxyl number of 68.2. Even at this lower 
molecular weight as reflected by the high hydroxyl number, polydispersity 
was very high, at 1.75. Significantly, the amount of high molecular weight 
tail is greater than the level of Example 1, at about 573 ppm (average), a 
c.a. 30% increase. Further, the polyol fails the critical foam test, 
exhibiting excessive foam settling. 
The Example 2 and 3 polyols (acidified glycerine feed) are near duplicates 
in properties. Examples 2 and 3 had polydispersities (M.sub.w /M.sub.n) of 
only 1.12 and viscosities from 651-665 cst. The hydroxyl number for 
Example 2 was 51.3 and the hydroxyl number for Example 3 was 49.9 compared 
to the specified 52.0 hydroxyl number target. The unsaturation for 
Examples 2 and 3 were again typical of levels of unsaturation generated 
when using highly active DMC catalysts, at c.a. 0.0026-0.0029 meq/g. 
By contrast, in the non-acidified Comparative Example C2, results are quite 
different. In Comparative Example C2, the catalyst deactivation is so 
severe that the desired molecular weight could not be achieved, as 
reflected by the high hydroxyl number of 67.0. Even at the lower molecular 
weight, polydispersity was high, 1.31. The viscosity of Comparative 
Example C2 was lower for the lower molecular weight polyol as compared to 
Examples 2 and 3. 
The examples and comparative examples discussed above indicate that 
acidification of the glycerine feed creates an enormous difference in DMC 
catalyzed glycerine oxyalkylation employing continuous addition of low 
molecular weight starter. Both the amount of high molecular weight tail as 
well as the polydispersity are lowered considerably, and catalyst 
deactivation is substantially prevented. It should again be noted that the 
contribution of the high molecular weight tail to the total polydispersity 
is very minimal. The greatest part of the difference in polydispersity 
between Example 1 and Comparative Example C1 is related to the 
distribution of molecules in the lower molecular weight range, i.e., in 
the neighborhood of the number average target weight of c.a. 3000 Da. 
While the subject process has been described relative to glycerine per se, 
it is also applicable to other low molecular weight starters which are 
synthesized, treated, or stored such that basic impurities which can cause 
DMC catalyst deactivation are present in the polyol, preferably starters 
having molecular weights below 300 Da, more preferably below 200 Da. One 
non-limiting example is diglycerol. Identity of such "acid sensitive" 
starters can be performed as previously indicated. 
The term "establishing oxyalkylation conditions" in an oxyalkylation 
reactor is believed to be self-explanatory. Such conditions are 
established when the reactor temperature, alkylene oxide pressure, 
catalyst level, degree of catalyst activation, presence of oxyalkylatable 
compounds within the reactor, etc., are such that upon addition of 
unreacted alkylene oxide to the reactor, oxyalkylation takes place. As a 
non-limiting example, in the batch version of continuous addition of 
starter, oxyalkylation conditions are initially established by following 
the procedures detailed in the preceding examples. By the term 
"continuously introducing" with respect to addition of alkylene oxide and 
low molecular weight starter is meant truly continuous, or an incremental 
addition which provides substantially the same results as continuous 
addition of these components. By the term "oxyalkylated low molecular 
weight starter polyether" is meant a polyoxyalkylene polyether prepared by 
oxyalkylating the acid sensitive low molecular weight starter or a starter 
mixture containing the acid sensitive low molecular weight starter. For 
example, when the acid sensitive low molecular weight starter is 
glycerine, the oxyalkylated low molecular weight starter polyether will be 
a polyoxypropylated, glycerine-initiated triol. The terms "starter" and 
"initiator" as used herein are the same unless otherwise indicated. 
Having now fully described the invention, it will be apparent to one of 
ordinary skill in the art that many changes and modifications can be made 
thereto without departing from the spirit or scope of the invention as set 
forth herein.