Note: Descriptions are shown in the official language in which they were submitted.
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HIGHLY ACTIVE DOUBLE METAL CYANIDE CATALYSTS
FIELD OF THE INVENTION
The invention relates to double metal cyanide (DMC) complex catalysts
useful for epoxide polymerization. In particular, the DMC catalysts of the
invention, which include a polyether, are easy to prepare and have exceptional
activity.
BACKGROUND OF THE INVENTION
Double metal cyanide (DMC) complexes are well-known catalysts for
epoxide polymerization. These active catalysts give polyether polyols that
have low unsaturation compared with similar polyols made using basic (KOH)
catalysis. The catalysts can be used to make many polymer products,
including polyether, polyester, and polyetherester polyols. The polyols can be
used in polyurethane coatings, elastomers, sealants, foams, and adhesives.
DMC catalysts are usually made by reacting aqueous solutions of
metal salts and metal cyanide salts to form a precipitate of the DMC
compound. A low molecular weight complexing agent, typically an ether or
an alcohol, is included in the catalyst preparation. Other known complexing
agents include ketones, esters, amides, ureas, and the like. See, for example,
U.S. Pat. Nos. 4,477,589, 3,829,505, and 5,158,922. The traditional favorite
complexing agent has been glyme (dimethoxyethane), which gives DMC
catalysts having activities within the range of about 0.1 to about 0.5 kg PO/g
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Co/min. at 100 ppm, based on the weight of finished polyether, at
105°C.
Recently, it was discovered (see U.S. Pat. No. 5,482,908, "the '908
patent") that the activity of DMC catalysts is greatly enhanced by
incorporating, in addition to the organic complexing agent, from about 5 to
about 80 wt. % of a polyether having a number average molecular weight
greater than about 500. Catalysts that contain both an organic complexing
agent (e.g., tert-butyl alcohol) and a polyether polyol can polymerize
propylene oxide at rates in excess of 2 kg PO/g Co/min. at 100 ppm catalyst,
based on the weight of finished polyether, at 105°C. In contrast, a
catalyst
containing polyol but no tert-butyl alcohol was inactive, and a catalyst made
with only tert-butyl alcohol was less active. Our initial work suggested that
polyethers having molecular weights lower than 500 and polyethylene glycols
were generally not suitable or gave much less active catalysts.
The ability to make very active DMC catalysts with low molecular
weight polyethers would be valuable because low molecular weight polyethers
are often cheaper or more readily available than those having molecular
weights greater than 500. Ideally, these DMC catalysts would offer the
advantages of the catalysts described in the '908 patent. For example, they
would give polyether polyols with very low unsaturation, and would be active
enough to allow their use at a very low concentrations, preferably at
concentrations low enough to overcome any need to remove the catalysts from
the polyol.
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SUMMARY OF THE INVENTION
The invention is a solid double metal cyanide (DMC) catalyst useful
for epoxide polymerizations. The catalyst comprises a DMC compound, an
organic complexing agent, and from about 5 to about 80 wt. %, based on the
amount of catalyst, of a polyether having a number average molecular weight
less than about 500. The catalyst is highly active: it polymerizes propylene
oxide at a rate in excess of about 1 kg PO/g Co/min. at 100 ppm catalyst,
based on the weight of finished polyether, at 105°C. Because the
catalyst is
so active, it can be used at very low concentrations, effectively eliminating
the
need for a catalyst removal step. In addition, the catalyst gives polyether
polyols with exceptionally low unsaturation levels. The invention includes
methods for making the catalyst.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 shows a plot of propylene oxide consumption versus time
during a polymerization reaction with one of the catalysts of the invention at
50 ppm catalyst. The activity of the catalyst (usually reported in this
application as kilograms of propylene oxide converted per gram of cobalt per
minute) is determined from the slope of the curve at its steepest point.
DETAILED DESCRIPTION OF THE INVENTION
Double metal cyanide (DMC) compounds useful in the invention are
the reaction products of a water-soluble metal salt and a water-soluble metal
cyanide salt. The water-soluble metal salt preferably has the general formula
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M(X)n in which M 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(V),
V(IV), Sr(II), W{IV), W(VI), Cu(II), and Cr(III). More preferably, M is
selected from the group consisting of Zn(II), Fe(II), Co(II), and Ni(II). In
the
formula, X is preferably an anion selected from the group consisting of
halide,
hydroxide, sulfate, carbonate, cyanide, oxalate, thiocyanate, isocyanate,
isothiocyanate, carboxylate, and nitrate. The value of n is from 1 to 3 and
satisfies the valency state of M. Examples of suitable metal salts include,
but
are not limited to, zinc chloride, zinc bromide, zinc acetate, zinc
acetonylacetonate, zinc benzoate, zinc nitrate, iron(II) sulfate, iron(II)
bromide, cobalt(II) chloride, cobalt(II) thiocyanate, nickel(II) formate,
nickel(II) nitrate, and the like, and mixtures thereof.
The water-soluble metal cyanide salts used to make the double metal
cyanide compounds preferably have the general formula (Y)aM'(CN)b(A)~ in
which M' is selected from the group consisting of Fe(II), Fe(III), Co(II),
Co(III), Cr(II), Cr(III), Mn(II), Mn(III), Ir(III), Ni(II), Rh{III), Ru(II),
V(IV),
and V(u). More preferably, M' is selected from the group consisting of
Co(II), Co(III), Fe(II), Fe(III), Cr(III), Ir(III), and Ni(II). The water-
soluble
metal cyanide salt can contain ane or more of these metals. In the formula, Y
is an alkali metal ion or alkaline earth metal ion. A is an ion selected from
the group consisting of halide, hydroxide, sulfate, carbonate, cyanide,
oxalate,
thiocyanate, isocyanate, isothiocyanate, carboxylate, and nitrate. Both a and
b
are integers greater than or equal to 1; the sum of the charges of a, b, and c
balances the charge of M'. Suitable water-soluble metal cyanide salts include,
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wo maooss Pcr~~roiszo
but are not limited to, potassium hexacyanocobahate(III), potassium
hexacyanoferrate(II), potassium hexacyanoferrate(III), calcium
hexacyanocobaltate(III), lithium hexacyanocobaltate(III), and the Iike.
Examples of double metal cyanide compounds that can be used in the
invention include, for example, zinc hexacyanocobaltate(III), zinc
hexacyanoferrate(III), nickel hexacyanoferrate(II), cobalt
hexacyanocobaltate(III), and the like. Further examples of suitable double
metal cyanide complexes are listed in U.S. Patent No. 5,158,922.,
Zinc hexacyanocobaltate(III) is preferred.
The solid DMC catalysts of the invention include an organic
complexing agent. Generally, the complexing agent must be relatively soluble
in water. Suitable complexing agents are those commonly known in the art,
as taught, for example, in U.S. Patent No. 5,158,922. The complexing agent
is added either during preparation or immediately following precipitation of
the catalyst. 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 complcxing agents are water-soluble aliphatic
alcohols selected from the group consisting of ethanol, isopropyl alcohol, n-
butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tent-butyl alcohol.
Tert-
butyl alcohol is particularly preferred.
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The solid DMC catalysts of the invention include from about 5 to
about 80 wt. %, based on amount of catalyst, of a polyether having a number
average molecular weight less than about 500. Preferred catalysts include
from about 10 to about 70 wt. % of the polyether; most preferred catalysts
include from about 15 to about 60 wt. % of the polyether. At least about 5
wt. % of the polyether is needed to significantly improve the catalyst
activity
compared with a catalyst made in the absence of the polyether. Catalysts that
contain more than about 80 wt. % of the polyether generally are no more
active, and they are impractical to isolate and use because they are typically
sticky pastes rather than powdery solids.
Polyethers suitable for use in making the catalysts of the invention
have number average molecular weights (Mn) less than about 500. Suitable
polyethers include those produced by ring-opening polymerization of cyclic
ethers, and include low-molecular-weight epoxide polymers, oxetane
polymers, tetrahydrofuran polymers, and the like. Any method of catalysis
can be used to make the poiyethers. The polyethers can have any desired end
groups, including, for example, hydroxyl, amine, ester, ether, or the like.
Preferred polyethers are polyether polyols having average hydroxyl
functionalities from about 1 to about 8 and number average molecular weights
within the range of about 150 to about 500, more preferably from about 200
to about 400. These can be made by polymerizing epoxides in the presence of
active hydrogen-containing initiators and basic, acidic, or organometallic
catalysts (including DMC catalysts). Useful polyether polyols include
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polypropylene glycol)s, polyethylene glycol)s, EO-capped
poly(oxypropylene) polyols, mixed EO-PO polyols, butylene oxide polymers,
butylene oxide copolymers with ethylene oxide and/or propylene oxide,
polytetramethylene ether glycols, and the like. Suitable polyethers also
include, for example, tripropylene glycol, triethylene glycol, tetrapropylene
glycol, tetraethylene glycol, dipropylene glycol monomethyl ether,
tripropylene glycol monomethyl ether, monoalkyl and dialkyl ethers of glycois
and poly(alkylene glycol)s, and the like. Most preferred are polypropylene
glycol)s and polyethylene glycol)s having number average molecular weights
within the range of about 150 to about 500. I found that both an organic
complexing agent and a polyether are needed in the double metal cyanide
catalyst. Including the polyether in addition to the organic complexing agent
surprisingly enhances catalyst activity compared with the activity of a
similar
catalyst prepared in the absence of the polyether (see Examples 1-5 and
Comparative Example 9). The organic complexing agent is also needed: a
catalyst made in the presence of the polyether, but without an organic
complexing agent such as tert-butyl alcohol, will not ordinarily polymerize
epoxides (see Comparative Examples 6-8).
The catalysts of the invention are characterized by any suitable means.
The polyether and organic complexing agent are conveniently identified and
quantified, for example, using thermogravimetric and mass spectral analyses.
Metals are easily quantified by elemental analysis.
The catalysts of the invention can also be characterized using powder
X-ray diffraction. The catalysts exhibit broad lines centered at
characteristic
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d-spacings. For example, a zinc hexacyanocobaltate catalyst made using tert-
butyl alcohol and a polyethylene glycol) of about 300 molecular weight has
two broad signals centered at d-spacings of about 5.75 and 4.82 angstroms,
and a somewhat narrower signal centered at a d-spacing of about 3.76
angstroms. (See Table 2). This diffraction pattern is further characterized by
the absence of sharp lines corresponding to highly crystalline zinc
hexacyanocobaltate at d-spacings of about 5.07, 3.59, 2.54, and 2.28
angstroms.
The invention includes a method for preparing solid DMC catalysts
useful for epoxide polymerization. The method comprises preparing a DMC
catalyst in the presence of a polyether having a number average molecular
weight less than about 500, wherein the solid DMC catalyst contains from
about 5 to about 80 wt. % of the polyether.
Generally, the method is performed by reacting, in an aqueous
solution, a metal salt (excess) and a metal cyanide salt in the presence of
the
polyether and an organic complexing agent. Enough of the polyether is used
to give a solid DMC catalyst that contains from about 5 to about 80 wt. % of
the polyether. Catalysts made using the method of the invention have
enhanced activity for epoxide polymerization compared with similar catalysts
prepared in the absence of the polyether.
In one method of the invention (illustrated by Examples 1-5 below),
aqueous solutions of a metal salt (such as zinc chloride) and a metal cyanide
salt (such as potassium hexacyanocobaltate) are first reacted in the presence
of
an organic complexing agent (such as tert-butyl alcohol) using efficient
mixing
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to produce a catalyst slurry. The metal salt is used in excess. The catalyst
slurry contains the reaction product of the metal salt and metal cyanide salt,
which is the double metal cyanide compound. Also present are excess metal
salt, water, and organic complexing agent; each is incorporated to some extent
in the catalyst structure.
The organic complexing agent can be included with either or both of
the aqueous 'salt solutions, or it can be added to the catalyst slurry
immediately following precipitation of the DMC compound. It is generally
preferred to pre-mix the complexing agent with either aqueous solution, or
both, before combining the reactants.
The aqueous metal salt and metal cyanide salt solutions (or their DMC
reaction product) need to be mixed efficiently with the complexing agent to
produce the most active form of the catalyst. A homogenizes or high-shear
stirrer is conveniently used to achieve efficient mixing.
The catalyst slurry produced in the first step is then combined with a
polyether having a number average molecular weight less than about 500.
This second step may be performed using low-shear mixing if desirable to
minimize foaming. When very efficient mixing is used in this step, the
mixture can thicken or coagulate, which complicates isolation of the catalyst.
In addition, the catalyst may lack the desired enhanced activity.
Third, a polyether-containing solid catalyst is isolated from the catalyst
slurry. This is accomplished by any convenient means, such as filtration,
centrifugation, or the like.
The isolated polyether-containing solid catalyst is then washed with an
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aqueous solution that contains additional organic complexing agent. Washing
is generally accomplished by reslurrying the catalyst in the aqueous solution
of
organic complexing agent, followed by a catalyst isolation step. This washing
step is used to remove impurities from the catalyst, for example KCI, that
will
render the catalyst inactive if they are not removed. Preferably, the amount
of organic complexing agent used in this aqueous solution is within the range
of about 40 wt. % to about 70 wt. % . It is also preferred to include some
polyether in the aqueous solution of organic complexing agent. The amount
of polyether in the wash solution is preferably within the range of about 0.1
wt. % to about 8 wt. % . Including a polyether in the wash step generally
enhances catalyst activity.
While a single washing step suffices to give a catalyst with enhanced
activity, it is preferred to wash the catalyst more than once. The subsequent
wash can be a repeat of the first wash. Preferably, the subsequent wash is
non-aqueous, i.e., it includes only the organic complexing agent or a mixture
of the organic complexing agent and polyether.
After the catalyst has been washed, it is usually preferred to dry it
under vacuum (88 to 102 KPa (26-30in. Hg}) until the catalyst reaches a
constant weight. The catalyst can be dried at temperatures within the range of
about 40°C to about 90°C.
In a second method of the invention, impurities are removed from the
catalyst during preparation by a dilution method that eliminates the need to
wash the isolated polyether-containing catalyst with an aqueous solution of
complexing agent.
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First, aqueous solutions of a metal salt (excess) and a metal cyanide
salt are reacted in the presence of an organic complexing agent using
efficient
mixing (as described above) to produce a catalyst slurry. Second, the catalyst
slurry is mixed efficiently with a diluent which comprises an aqueous solution
of additional organic complexing agent. The diiuent is used in an amount
effective to solubilize impurities (i.e., excess reactants, KCI, etc.) in the
aqueous phase.
After dilution with aqueous complexing agent, the catalyst slurry is
combined with a polyether having a number average molecular weight Iess
than about 500. It is generally preferred to use low-shear mixing in this
step.
The polyether-containing solid catalyst is then isolated from the slurry by
any
convenient means (as described earlier), including filtration, centrifugation,
or
the like. After isolation, the catalyst is preferably washed with additional
organic complexing agent or a mixture of additional polyether and organic
complexing agent. This washing step can be accomplished without the need to
reslurry or resuspend the solids in the wash solvent. Finally, a solid DMC
catalyst that contains from about 5 to about 80 wt. % of the polyether is
isolated.
The catalysts of the invention have significantly higher activity than
most DMC catalysts previously known in the art. For example, conventional
DMC catalysts made with glyme complexing agent and no polyether (as
described, for example, in U.S. Pat. Nos. 4,477,589, 3,829,505, and
5,158,922) have activities within the range of about 0.1 to about 0.5 kg PO/g
Co/min. at 100 ppm, based on the weight of finished polyether, at
105°C. In
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contrast, the catalysts of the invention polymerize propylene oxide at a rate
in
excess of 1 kg PO/g Co/min. at 100 ppm, based on the weight of finished
polyether, at 105°C. These catalysts have enhanced activity similar to
the
catalysts I previously disclosed in U.S. Pat. No. 5,482,908, which use
polyethers of higher molecular weight. While it was previously thought that
lower molecular weight polyethers would not be suitable for use, I have now
found that polyethers having molecular weights less than S00 can, in fact, be
used to produce polyether-containing DMC catalysts with high activity. As
Examples ~ 1-5 and Comparative Example 9 demonstrate, the catalysts of the
invention have activities greater than that of a zinc hexacyanocobaltate/ tert-
butyl alcohol complex made in the absence of a polyether.
The catalysts of the invention are active enough to allow their use at
very low catalyst concentrations, such as 25 ppm or less (see Example 10
below). At such low catalyst levels, the catalyst can often be left in the
polyether polyol product without an adverse impact on product quality. For
example, the amount of residual Zn and Co in the polyol from a zinc
hexacyanocobaltate catalyst of the invention can be within product
specifications ( < S ppm each) before any purification of the polyol. When
higher product purity is needed, a simple filtration is usually adequate to
remove the last traces of catalyst from the polyol product; the catalyst
appears
to be heterogeneous. The ability to leave these catalysts in the polyol is an
important advantage because at present, most commercial polyether polyols
(generally made with KOH) require a catalyst removal step.
The following examples merely illustrate the invention. Those skilled
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in the art will recognize many variations that are within the spirit of the
invention and scope of the claims.
EXAMPLE 1
Preparation of a Polyether-Containing DMC Catalyst (PEG-300)
Potassium hexacyanocobaltate (7.5 g) is dissolved in distilled water
(300 mL) and test-butyl alcohol (50 mL) in a beaker (Solution 1). Zinc
chloride (76 g) is dissolved in distilled water (76 mL) in a second beaker
(Solution 2). A third beaker contains Solution 3: a mixture of distilled water
(200 mL), test-butyl alcohol (2 mL), and polyol (8 g of PEG-300, a 300 mol.
wt. polyethylene glycol) obtained from Aldrich).
Solution 2 is added to solution 1 over 30 min. at 30°C with mixing
using a homogenizes set at 20% intensity. Mixing intensity is increased to
40°70 for 10 min. The homogenizes is removed. Solution 3 is added, and
the
mixture is stirred for 3 min. using a magnetic stirring bar. The mixture is
filtered under pressure (276Kpa gauge (40 psig)) through a 20 X10-6m (20-
micron) filter.
The catalyst solids are reslurried in test-butyl alcohol (130 mL) and
distilled water (56 mL) and homogenized at 40% intensity for 10 min. The
homogenizes is removed. PEG-300 (2 g) is added and mixed using magnetic
stirring for 3 min. The mixture is filtered under pressure as described above.
The catalyst solids are reslurred in test-butyl alcohol (18~ mL) and
homogenized as before. PEG-300 (1 g) is added and mixed using magnetic
stirring for 3 min. The mixture is filtered under pressure. The resulting
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catalyst cake is dried at 60°C under vacuum (102KPa (30 in. Hg)) to a
constant weight.
EXAMPLE 2
Preparation of a Polyether-Containing DMC Catalyst (PEG-300)
Zinc chloride (75 g) is dissolved in distilled water (275 mL) and tert-
butyl alcohol (50 mL) to make Solution 1. Potassium hexacyanocobaltate (7.~
g) is dissolved in distilled water (100 mL) in a second beaker (Solution 2). A
third beaker contains Solution 3: a mixture of distilled water {50 mL), tert-
butyl alcohol (2 mL), and polyol (8 g of PEG-300).
Solution 2 is added to solution 1 over 30 min. at 50°C with mixing
using a homogenizer set at 20% intensity. Mixing intensity is increased to
40% for 10 min. The homogenizer is removed. Solution 3 is added, and the
mixture is stirred for 3 min. using a magnetic stirring bar. The mixture is
filtered under pressure ((276 KPa gauge (40 psig)) through a 5 x 10-6m (5-
micron) filter.
The catalyst solids are reslurried in tert-butyl alcohol (130 mL) and
distilled water (55 mL) and homogenized at 40% intensity for 10 min. The
homogenizer is removed. PEG-300 (2 g) is added and mixed using magnetic
stirring for 3 min. The mixture is filtered under pressure as described above.
The catalyst solids are reslurred in tert-butyl alcohol (185 mL) and
homogenized as before. PEG-300 (1 g) is added and mixed using magnetic
stirring for 3 min. The mixture is filtered under pressure. The resulting
catalyst cake is dried at 60°C under vacuum (102KPa ({30 in. Hg)) to a
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constant weight.
EXAMPLE 3
Preparation of a Polyether-Containing DMC Catalyst (PPG-425)
The procedure of Example 1 is followed, except that PPG-425, a 400
mol. wt. polypropylene glycol) prepared by KOH catalysis, is used instead of
PEG-300, and the catalyst is prepared at SO°C instead of 30°C.
The resulting
catalyst is isolated and dried as described previously.
EXAMPLE 4
Preparation of a Polyether-Containing DMC Catalyst (PPG-425)
A solution (Solution 1) of zinc chloride (252 g), distilled water (924
mL), and tert-butyl alcohol (168 mL) is prepared in a one-gallon glass
reactor.
Potassium hexacyanocobaltate (25.2 g) is dissolved in distilled water (336 mL)
in a beaker (Solution 2). Another beaker contains Solution 3: a mixture of
distilled water (160 mL), tert-butyl alcohol (6.7 mL), and polyol (26.9 g of
PPG-425).
Solution 2 is added to solution 1 over 1 h at 50°C with 450 rpm
stirring. After the addition is complete, the stirring rate is increased to
900
rpm for 1 h under 10 psig nitrogen. The stirring rate is decreased to 200
rpm. Solution 3 is added, and the mixture is stirred for 3 min. at 200 rpm.
The mixture is filtered under pressure (276 KPa gauge (40 psig)) through a 10
x 10-bm (10-micron) filter.
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The catalyst solids are reslurried in the same reactor with test-butyl
alcohol (437 mL) and distilled water (186 mL) and mixed at 900 rpm for 1 h.
The stirring rate is decreased to 200 rpm. PPG-425 (6.7 g) is added, and the
mixture is stirred at 200 rpm for 3 min. The mixture is filtered under
pressure as described above. The catalyst solids are reslurred in test-butyl
alcohol (622 mL) and stirred as described above. The stirring rate is again
decreased to 200 rpm. PPG-425 (3.4 g) is added and mixed for 3 min. The
mixture is filtered under pressure. The resulting catalyst cake is dried at
60°C
under vacuum (102 KPa (30 in. Hg)) to a constant weight.
EXAMPLE 5
Preparation of a Polyether-Containing DMC Catalyst
{Tripropylene Glycol Monomethyl Ether)
The procedure of Example 2 is followed, except that tripropylene
glycol monomethyl ether (Aldrich) is used instead of PEG-300. The resulting
catalyst is isolated and dried as described previously.
COMPARATIVE EXAMPLE 6
Preparation of a Polyether-Containing DMC Catalyst:
PEG-300 Polyol; No test-Butyl Alcohol Complexing Agent (30°C)
Potassium hexacyanocobaltate (7.5 g) and PEG-300 (8.0 g) are
dissolved in distilled water (300 mL) in a beaker (Solution 1). Zinc chloride
(76 g) is dissolved in distilled water (76 mL) in a second beaker (Solution
2).
Solution 2 is added to solution 1 over 30 min. at 30°C with mixing
using a
homogenizes set at 20% intensity. Mixing intensity is increased to 40% for
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min. The mixture is filtered under pressure (276 KPa gauge (40 psig))
through a 5 x l0~bm (5-micron) filter.
The catalyst solids are reslurried in distilled water (200 mL) and
homogenized at 40%v intensity for 10 min. The mixture is filtered under
pressure as described above. The resulting catalyst cake is dried at
60°C
under vacuum (102 KPa (30 in. Hg)) to a constant weight.
COMPARATIVE EXAMPLE 7
Preparation of a Polyether-Containing DMC Catalyst:
PPG-425 Polyol; No test-Butyl Alcohol Complexing Agent
The procedure of Comparative Example 6 is followed, except that
PPG-425 polyol is used in place of PEG-300 polyol. The resulting catalyst is
isolated and dried as described previously.
COMPARATIVE EXAMPLE 8
Preparation of a Polyether-Containing DMC Catalyst:
PEG-300 Polyol; No test-Butyl Alcohol Complexing Agent (50°C)
Zinc chloride (75 g) and PEG-300 (39 g) are dissolved in distilled
water (275 mL) in a beaker (Solution 1). Potassium hexacyanocobaltate (7.5
g) is dissolved in distilled water (100 mL) in a beaker (Solution 2). PEG-300
(8 g) is dissolved in distilled water (50 mL) in a beaker (Solution 3).
Solution 2 is added to solution 1 over 30 min. at 50°C with mixing
using a homogenizes set at 20% intensity. Mixing intensity is increased to
40% for 10 min. The homogenizes is removed. Solution 3 is added, and the
mixture is stirred with a magnetic stirrer for 3 min. The mixture is filtered
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under pressure (276 KPa gauge (40 psig)) through a 5 x 10-bm (5-micron)
filter. The catalyst solids are reslurried in distilled water (75 mL) and PEG-
300 (75 g), and the mixture is homogenized at 40% intensity for 10 min. The
homogenizer is removed. PEG-300 (2 g) is added, and the mixture is stirred
magnetically for 3 min. The mixture is filtered under pressure as described
above. The resulting catalyst cake is dried at 60°C under vacuum (102
KPa
(30 in. Hg)) to a constant weight.
COMPARATIVE EXAMPLE 9
Preparation of a DMC Catalyst With tert-Butyl Alcohol (Complexing Agent)
and Without a Polyether Polyol
Potassium hexacyanocobaltate (24 g) is dissolved in distilled water (450
mL) in a beaker (Solution 1). Zinc chloride (60 g) is dissolved in distilled
water (90 mL) in a second beaker (Solution 2). Solutions 1 and 2 are
combined using a homogenizer for mixing. Immediately thereafter, a mixture
of tert-butyl alcohol and water (50/50 by volume, 600 mL) is slowly added,
and the resulting slurry is homogenized for 10 min. The slurry is centrifuged,
and the liquid portion is decanted. The solids are reslurried in a mixture of
tert-butyl alcohol and water (70/30 by volume, 600 mT.), and this mixture is
homogenized for 10 min., and then centrifuged and decanted as described
above to isolate the washed solids. The solids are reslurried in 100% tert-
butyl alcohol (600 mL), and the mixture is homogenized for 10 min.,
centrifuged, and decanted. The solid catalyst is dried in a vacuum oven
(50°C, 102 KPa (30 in. Hg)) to constant weight.
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Elemental, thermogravimetric, and mass spectral analyses of the solid
catalyst show: tert-butyl alcohol = 14.1 wt. %; cobalt = 12.5 wt. %; (polyol
= 0 wt. %).
EXAMPLE A
Measurement of Catalyst Activity and Polyether Polyol Synthesis
Catalysts prepared as described above are used to prepare polyether
triols having hydroxyl numbers of about 30 mg KOH/g as follows.
A one-liter stirred reactor is charged with 70 g of a 700 mol. wt. poly-
(oxypropylene) triol starter polyol and 0.014 g to 0.057 g of the zinc
hexacyanocobaltate/ tert-butyl alcohol/ polyether polyol catalyst (25 to 100
ppm of catalyst in the final polyol product, see Table 1 footnotes). The
mixture is vigorously stirred and heated to 105°C under vacuum for
about 30
min. to remove traces of residual water. Propylene oxide (PO) (about 10 to
11 g) is added to the reactor, and the pressure in the reactor is increased
from
vacuum to about 28 KPa gauge (4 psig). An accelerated drop in reactor
pressure soon occurs, indicating that the catalyst has become activated. After
initiation of the catalyst is verified, additional propylene oxide (a total of
500
g) is added slowly to the reactor to maintain the reactor pressure at about 69
KPa gauge (10 psig).
Catalyst activity is measured from the slope of a PO conversion vs.
time plot at its steepest point (see Figure 1 for a sample plot, and Table 1
for
polymerization rates). After the PO addition is complete, the reaction mixture
is held at 105°C until a constant pressure is obtained, which indicates
that PO
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CA 02252398 1998-10-16
WO 97140086 PCT/EP97/01820
conversion is complete. The mixture is vacuum stripped at 60 to 80°C
for 0.5
h to remove any traces of unreacted PO from the reactor. The product is
cooled and recovered. The product is a poly(oxypropylene) triol having a
hydroxyl number of about 30 mg KOH/g (see Table 1).
EXAMPLE B
Catalyst Characterization by Powder X-ray Diffraction
Table 2 shows typical powder X-ray diffraction results for a number of
zinc hexacyanocobaltate catalysts. The X-ray patterns for Comparative
Examples 6-9 (catalysts made in the presence of a polyol, but no tert-butyl
alcohol complexing agent) resemble the pattern for highly crystalline zinc
hexacyanocobaltate hydrate, which is made in the absence of any polyol or
organic complexing agent. All of these "catalysts" are inactive toward
epoxide polymerization.
Catalysts of the invention {Examples 1-5), which are made in the
presence of both tert-butyl alcohol and a polyol, exhibit a broad signal at a
d-
spacing of about 5.75 angstroms. This signal is absent from the catalyst made
with tert-butyl alcohol but no polyol (Comparative Example 9). While the
catalysts of Examples 1-5 and C9 actively polymerize propylene oxide, the
catalysts made with both tert-butyl alcohol and polyol (Examples 1-5) have
higher activities (see Table 1).
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CA 02252398 1998-10-16
WO 97/40086 PCT/EP97/01820
EXAMPLE 10
Preparation of a 8K Poly(oxypropylene) Diol Using 2~ ppm Catalyst
This example shows that catalysts of the invention are active enough to
enable the preparation of polyether polyols using low catalyst concentrations.
This effectively eliminates the need for catalyst removal for many polyol end
uses.
A sample of the catalyst prepared in Example 4 is used. A one-liter
stirred reactor is charged with catalyst (O.OI66 g, 25 ppm in the finished
polyol) and a 785 mol. wt. poly(oxypropylene) diol (65 g) prepared
conventionally from propylene glycol, KOH, and propylene oxide. The
mixture is well stirred and heated to 105°C under vacuum for about 30
min, to
remove traces of residual water. The mass temperature is increased to
130°C.
Propylene oxide (11 g) is added to the reactor, and the pressure in the
reactor
is increased from vacuum to about 14 KPa gauge (2 psig). An accelerated
pressure drop occurs, indicating that the catalyst has become active. After
catalyst initiation is verified, additional propylene oxide (600 g total) is
continuously added at 1.7 g/min. over 6 h. The reactor is held at 130°C
for
30 to 45 min. until a constant pressure is obtained, which indicates that
propylene oxide conversion is complete. The mixture is stripped under
vacuum at 60°C for 30 min. to remove traces of unreacted propylene
oxide.
The product is cooled and recovered. The resulting 8000 mol. wt. poly(PO)
diol) has a hydroxyl number of 14.9 mg KOH/g, an unsaturation of 0.005
meq/g, and a Mw/Mn = 1.22.
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WO 97/40086 PCT/EP97/01820
The preceding examples are meant only as illustrations. The following
claims define the scope of the invention.
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CA 02252398 1998-10-16
WO 97140086 PCT/EP97/01820
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-23-
CA 02252398 2002-03-27
WO 97140086 PCT/EP97/01820
Table
2.
DMC
Catalyst
Characterization
by
X-Ray
Diffraction
X-Ray
Diffraction
Pattern
(d-spacings,
angstroms)'
Catalyst
content
5.75 5.07 4.82 3.76 3.59 2.54 2.28
(br) (s) (br) (s) (s) (s)
--- Cryst. absentX absentabsentX X X
Zn-Coy
C6 Polyol,absentX absentabsentX X X
but
no
TBA2
C9 TBA, weak absentX X absent absent
but absent
no
polyol2
1 TBA X absentX X absentabsent absent
&
polyol'
X =
X-ray
diffraction
line
present;
(br)
=
broad
band;
(s)
=
sharp
line;
weak
=
weak
signal
present
Samples
were
analyzed
by
X-ray
diffraction
using
monochromatized
CuKa~
radiation
(
~1
=
1.54059
~).
A
Seimens
D500
KristallofleX
iiiffractometer
powered
at
40
kV
and
30
mA
was
operated
in
a
step
scan
mode
of
0.02
2B
with
a counting
time
of
2
seconds/step.
Divergence
slits
of
1
in
conjunction
with
monochrometer
and
deterxor
apertures
of
0.05
and
0.15
respectively.
Each
sample
was
run
from
to
70
2B.
' Water
of
hydration
can
cause
minor
variations
in
measured
d-spacings.
a Comparative
example.
' Catalyst
of
the
invention.
s
*trade-mark
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