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Double-Metal Cyanide Catalysts Containing
Polyester for Preparing Polyether Polyols
Technical Field of the Invention
The invention relates to new improved double-metal cyanide (DMC) catalysts for
the preparation of po:lyether-polyols by polyaddition of alkylene oxides on to
starter compounds containing active hydrogen atoms.
Background of the Invention
Double-metal cyanide (DMC) catalysts for polyaddition of alkylene oxides on to
starter compounds containing active hydrogen atoms are known (see, for
example,
US 3 404 109, US 3 829 505, US 3 941 849 and US 5 158 922). The use of these
DMC catalysts for the preparation of polyether-polyols has the effect, in
particular, of a reduction in the proportion of monofunctional polyethers with
terminal double bonds, so-called monools, compared with the conventional
preparation of polyether-polyols by means of alkali catalysts, such as alkali
metal
hydroxides. The polyether-polyols thus obtained can be processed to high-grade
polyurethanes (e.g. elastomers, foams, coatings). DMC catalysts are usually
obtained by reacting an aqueous solution of a metal salt with an aqueous
solution
of a metal cyanide salt in the presence of a low molecular weight organic
complexing ligand, e.g. an ether. In a typical catalyst preparation, for
example,
aqueous solutions of zinc chloride (in excess) and potassium
hexacyanocobaltate
are mixed, and dimethoxyethane (glyme) is then added to the suspension formed.
After filtration and washing of the catalyst with aqueous glyme solution, an
active
catalyst of the general formula
Zn3[Co(CN)6]Z ~ x ZnCl2 ~ y H20 ~ z glyme
is obtained (see e.g. EP 700 949).
JP 4 145 123, US 5 470 813, EP 700 949, EP 743 093 and EP 761 708 disclose
improved DMC catalysts which, by the use of tert-butanol as the organic
complexing ligand (by itself or in combination with a polyether (EP 700 949,
EP
761 708)), are capable of further reducing the proportion of monofunctional
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polyethers with terminal double bonds in the preparation of polyether-polyols.
Furthermore, by using the improved DMC catalysts, the induction time for the
polyaddition reaction of the alkylene oxides on to corresponding starter
compounds is reduced and the catalyst activity is increased.
Summarv of the Invention
The object of the present invention is thus to provide DMC catalysts for the
polyaddition of alkylene oxides on to corresponding starter compounds which
are
improved further and which have an induction time which is reduced
considerably
with respect to the catalyst types known to date, and at the same time a
significantly increased catalyst activity. By shortening the total reaction
and cycle
times of the polyether-polyol preparation, this leads to an improved
profitability of
the process. Ideally, because of the increased activity, the catalyst can then
be
employed in such low concentrations that removal of the catalyst, which is
otherwise very expensive, is no longer necessary, and the product can be used
directly for polyurethane applications. Surprisingly, it has now been found
that
DMC catalysts which contain 5 - 80 wt.%, based on the amount of finished
catalyst, of a polyester have significantly shortened induction times and at
the
same time a greatly increased activity in polyether-polyol preparation.
Brief Description of the Drawings
Figure I is a powder X-ray diffraction pattern for the double-metal cyanide
catalyst prepared according to Example 2 of the invention.
Figure 2 is a powder X-ray diffraction pattern for the double-metal cyanide
catalyst prepared according to Example 3 of the invention.
Detailed Descrt_ption of the Invention
The present invention provides new improved double-metal cyanide (DMC)
catalysts comprising
a) a double-met<a cyanide compound and
b) an organic complexing ligand,
which are characterized in that they contain 5 to 80 wt.°1o, based on
the amount of
finished catalyst, of a polyester.
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The catalysts according to the - invention can optionally also comprise water,
preferably 1 to 10 wt.%, and/or a water-soluble metal salt, preferably 5 to 25
wt.%,
from the preparation of the double-metal cyanide compound.
The double-metal cyanide compounds a) which are suitable for the catalysts
according to 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 M(X)", wherein
M is
chosen from the metals 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).
Zn(II), Fe(II), Co(II) and Ni(II) are particularly preferred. X is an anion,
preferably
chosen from the group consisting of the halides, hydroxides, sulfates,
carbonates,
cyanates, thiocyanates, isocyanates, isothiocyanates, carboxylates, oxalates
or
nitrates. The value of n is 1, 2 or 3.
Examples of suitable metal salts are zinc chloride, zinc bromide, zinc
acetate, zinc
acetylacetonate, zinc benzoate, zinc nitrate, iron(II) sulfate, iron(II)
bromide, iron(II)
chloride, cobalt(II) chloride, cobalt(II) thiocyanate, nickel(II) chloride and
nickel(II)
nitrate. Mixtures of different metal salts can also be employed.
The water-soluble metal cyanide salt preferably has the general formula
(Y)aM'(CN)b(A)~, wherein M' is chosen from the metals 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(V). M' is particularly preferably chosen from the metals Co(II), Co(III),
Fe(II),
Fe(III), Cr(III), Ir(III) and Ni(II). The water-soluble metal cyanide salt can
contain
one or more of these metals. Y is an alkali metal ion or an alkaline earth
metal ion.
A is an anion chosen from the group consisting of the halides, hydroxides,
sulfates,
carbonates, cyanates, thiocyanates, isocyanates, isothiocyanates,
carboxylates,
oxalates or nitrates. Both a and b are integers (>_ 1 ), the values for a, b
and c being
chosen such that the electroneutrality of the metal cyanide salt is ensured; c
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preferably has the value 0. Examples of suitable water-soluble metal cyanide
salts
are potassium hexacyanocobaltate(III), potassium hexacyanoferrate(II),
potassium
hexacyanoferrate(III), calcium hexacyanocobaltate(III) and lithium
hexacyanocobaltate(III).
S
Examples of suitable double-metal cyanide compounds a) which can be used in
the
catalysts according to the invention are zinc hexacyanocobaltate(III), zinc
hexacyanoferrate(II), zinc hexacyanoferrate(III), nickel(II)
hexacyanoferrate(II) and
cobalt(II) hexacyanocobaltate(III). Further examples of suitable double-metal
cyanide compounds are to be found e.g. in US 5 158 922 (column 8, lines 29 -
66).
Zinc hexacyanocobaltate(III) is preferably used.
The DMC catalysts according to the invention contain an organic complexing
ligand
b), since this e.g. increases the catalysis activity. Suitable organic
complexing
ligands are known in principle and are described in detail in the prior art
mentioned
above (see e.g. column 6, lines 9 - 65 in US 5 158 922). The complexing ligand
is
added either during the preparation of the catalyst or immediately after
precipitation
of the catalyst. The complexing ligand is usually employed in excess.
Preferred
complexing ligands are water-soluble organic compounds with heteroatoms which
can form complexes with the double-metal cyanide compound. Suitable organic
complexing ligands are e.g. alcohols, aldehydes, ketones, ethers, esters,
amides,
areas, nitrites, sulfides and mixtures thereof. Preferred organic complexing
ligands
are water-soluble aliphatic alcohols, such as e.g. ethanol, isopropanol, n-
butanol, iso-
butanol, sec-butanol and tert-butanol. tert-Butanol is particularly preferred.
The DMC catalysts according to the invention contain the double-metal cyanide
compounds in amounts of 20 to 85 wt.%, preferably 25 to 80 wt.%, based on the
amount of finished catalyst, and the organic complexing ligands in amounts of
1 to
30, preferably 2 to 20 wt.%, again based on the amount of finished catalyst.
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The DMC catalysts according to the invention contain 5 - 80 wt.%, based on the
amount of finished catalyst, of a polyester. Preferred catalysts contain 10 to
60 wt.%
polyester.
Polyesters which are suitable for the preparation of the catalysts according
to the
invention are higher molecular weight substances which contain the ester group
-O-
CO- as a recurring unit in the chain. They are as a rule obtained by
polycondensation of polyfunctional carboxylic acids and hydroxy compounds.
Further customary preparation possibilities for polyesters comprise
polycondensation of hydroxycarboxylic acids, polymerization of cyclic esters
(lactones), polyaddition of polycarboxylic acid anhydrides with epoxides and
reaction of acid chlorides with alkali metal salts of hydroxy compounds.
Transesterification both with hydroxy and with carboxy compounds is also
possible.
Methods for the preparation of polyesters are generally well-known and are
described in detail, for example, in "Kunststoff Handbuch", volume 7,
Polyurethane,
3rd edition, 1993, p. 67 - 74, "High Polymers", volume 16, Polyurethanes:
Chemistry and Technology, I. Chemistry, 1st edition, 1962, p. 44 - 66,
"Ullmanns
Encyclopadie der Technischen Chemie", volume 19, 4th edition, 1982, p. 61 - 88
and "Houben-Weyl, Methoden der organsichen Chemie", volume E20,
Makromolekulare Stoffe, 4th edition, 1987, p. 1405 - 1457.
Polyesters which are preferably employed are linear or partly branched
polyesters
having average molecular weights below 10,000, which are in general obtained
by
polycondensation from saturated or unsaturated aliphatic or from
cycloaliphatic or
from aromatic dicarboxylic acids with difunctional or trifunctional or mixture
of di-
and trifunctional compounds containing hydroxyl groups, or by ring-opening
polymerization of lactones (e.g. caprolactone) with diols and/or triols as
starters.
Polyesters having average molecular weights of 400 to 6,000 and OH numbers of
28
to 300 mg KOH/g, which are suitable for the preparation of polyurethanes, are
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particularly preferably employed. These polyesters are in general prepared by
polycondensation of polyfunctional carboxylic acids and hydroxy compounds.
Possible polyfunctional hydroxy compounds for this are, in particular:
ethylene
glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol,
dipropylene
glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,12-dodecanediol,
neopentylglycol, trimethylolpropane, trimethylolethane, glycerol and, in rarer
cases, some longer-chain trihydroxy compounds.
Possible polyfunctional carboxylic acids are, in particular: adipic acid,
phthalic
acid, isophthalic acid, terephthalic acid, oxalic acid, succinic acid,
glutaric acid,
azelaic acid, sebacic acid, fumaric acid, malefic acid and, in rarer cases,
the so-
called "dimeric acids", which are obtainable by dimerization of unsaturated
plant
fatty acids.
Both the use of the organic complexing ligand and that of the polyester are
necessary for the preparation of a DMC catalyst with a reduced induction
period
and increased activity (see examples 7 - 8 and comparison examples 6 and 9).
The catalyst composition is usually analysed by means of elemental analysis
and
thermogravimetry.
The catalysts according to the invention can be crystalline, substantially
crystalline, partly crystalline or amorphous. The crystallinity is usually
analysed
by powder X-ray diffractometry.
Catalyst according to the invention which are preferred are those comprising
a) zinc hexacyanocobaltate(III) and
b) tent-butanol,
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which are characterized in that they comprise 5-80 wt.%, based on the amount
of
finished catalyst, of a polyester with an average molecular weight of 400 to
6,000
and an OH number of 28 to 300 mg KOH/g.
S The improved DMC catalysts according to the invention are usually prepared
in
aqueous solution by reaction of the metal salt (in excess) and metal cyanide
salt in
the presence of the organic complexing ligand and the polyester.
Preferably, in this preparation, the aqueous solutions of the metal salt (e.g.
zinc
chloride, employed in a stoichiometric excess (at least 50%, based on the
metal
cyanide salt)) and of the metal cyanide salt (e.g. potassium
hexacyanocobaltate) are
first reacted in the presence of the organic complexing ligand (e.g. tert-
butanol), a
suspension which comprises the double-metal cyanide compound (e.g. zinc
hexacyanocobaltate), excess metal salt, water and the organic complexing
ligand
being formed.
The organic complexing ligand can be present here either in one or in both of
the
aqueous solutions, or it is added to the suspension immediately after
precipitation of
the double-metal cyanide compound. It has proved advantageous to mix the
aqueous solutions and the organic complexing ligand with vigorous stirring.
The catalyst suspension formed is then treated with the polyester. The
polyester is
preferably employed in this procedure in a mixture with water and the organic
complexing ligand.
The catalyst containing the polyester is isolated from the suspension by known
techniques, such as e.g. centrifugation or filtration.
To increase the activity of the catalyst, it is advantageous for the catalyst
isolated to
be subsequently washed with an aqueous solution of the organic complexing
ligand
(e.g. by resuspension and subsequent renewed isolation by filtration or
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centrifugation). It is possible, for example, for water-soluble by-products,
such as
potassium chloride, which adversely influence the polyaddition reaction to be
removed from the catalyst according to the invention in this manner.
The amount of organic complexing ligand in the aqueous washing solution is
preferably between 40 and 80 wt.%. It is furthermore advantageous to add a
little
polyester, preferably in the range between 0.5 and 5 wt.%, to the aqueous
washing
solution.
It is moreover advantageous to wash the catalyst more than once. The first
washing
operation e.g. can be repeated for this. However, it is preferable to use non-
aqueous
solutions, e.g. a mixture of organic complexing ligand and polyester, for
further
washing operations.
The washed catalyst is finally dried at temperatures of 20 - 100°C and
under pressure
from 0.1 mbar to normal pressure ( 1013 mbar), optionally after pulverizing.
The invention also provides the use of the improved DMC catalysts according to
the
invention for the preparation of polyether-polyols by polyaddition of alkylene
oxides
on to starter compounds containing active hydrogen atoms.
Alkylene axides which are preferably employed are ethylene oxide, propylene
oxide,
butylene oxide and mixtures thereof. The polyether chains can be built up by
alkoxylation e.g. with only one monomeric epoxide, or also randomly or in
blocks
with 2 or 3 different monomeric epoxides. Further details can be found in
"Ullmanns Encyclopadie der industriellen Chemie", English language edition,
1992,
volume A21, pages 670 - 671.
Compounds having molecular weights of 18 to 2,000 and 1 to 8 hydroxyl groups
are
employed as the starter compounds containing active hydrogen atoms. Examples
which are mentioned are: ethylene glycol, diethylene glycol, triethylene
glycol, 1,2-
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propylene glycol, 1,4-butanediol, hexamethylene glycol, bisphenol A,
trimethylolpropane, glycerol, pentaerythritol, sorbitol, sucrose, degraded
starch and
water.
Those starter compounds containing active hydrogen atoms which have been
prepared e.g. by conventional alkali catalysis from the abovementioned low
molecular weight starters and are oligomeric alkoxylation products having
molecular
weights of 200 to 2,000 are advantageously employed.
The polyaddition of alkylene oxides on to starter compounds containing active
hydrogen which is catalysed by the catalysts according to the invention is in
general
carned out at temperatures of 20 to 200°C, preferably in the range from
40 to 180°C,
particularly preferably at temperatures from 50 to 150°C. The reaction
can be
carried out under overall pressures of 0 to 20 bar. The polyaddition can be
carned
out in bulk or an inert organic solvent, such as toluene and/or THF. The
amount of
solvent is usually 10 to 30 wt.%, based on the amount of polyether-polyol to
be
prepared.
The catalyst concentration is chosen such that good control of the
polyaddition
reaction under the given reaction conditions is possible. The catalyst
concentration
is in general in the range from 0.0005 wt.% to 1 wt.%, preferably in the range
from
0.001 wt.% to 0.1 wt.%, based-on the amount of polyether-polyol to be
prepared.
The molecular weights of the polyether-polyols prepared by the process
according to
the invention are in the range from 500 to 100,000 g/mol, preferably in the
range
from 1,000 to 50,000 g/mol, more preferably in the range from 2,000 to 20,000
g/mol.
The polyaddition can be carried out continuously, or in a batch or semibatch
process.
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The catalysts according to the invention in general require an induction time
of some
minutes up to several hours.
The induction times in the preparation of polyether-polyols are shortened
significantly with the aid of the new catalysts according to the invention,
compared
with the DMC catalysts known hitherto.
At the same time, the alkoxylation times are greatly reduced because of the
substantially increased activity.
This leads to a shortening of the total reaction times (sum of the induction
and
alkoxylation times) by typically 60 - 75% compared with the DMC catalysts
known
hitherto.
Because of their significantly increased activity, the catalysts according to
the
invention can be employed in such low concentrations (15 ppm and less, based
on
the amount of polyether-polyol to be prepared, see example 10), that removal
of the
catalyst from the polyol can generally be omitted for use in polyurethane
applications, without the product qualities being adversely influenced.
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Examples
Catalxst preparation
Comparison example 1
Preparation of a DMC catalyst with tent-butanol as the organic complexing
ligand
without using a polyester (catalyst A, synthesis according to JP 4 145 123).
A solution of 10 g (73.3 mmol) zinc chloride in 15 ml distilled water is added
to a
solution of 4 g (12 mmol) potassium hexacyanocobaltate in 75 ml distilled
water
with vigorous stirnng. Immediately thereafter, a mixture of 50 g tert-butanol
and 50
g distilled water is added to the suspension formed and the mixture is then
stirred
vigorously for 10 min. The solid is isolated by filtration, then stirred with
125 g of a
mixture of tent-butanol and distilled water (70/30; w/w) for 10 min and
filtered off
again. Finally, it is stirred once more with 125 g tert-butanol for 10 min.
After
filtration the catalyst is dried to constant weight at 50°C under
normal pressure.
Yield of dried pulverulent catalyst: 3.08 g
Elemental analysis: cobalt = 13.6%; zinc = 27.35%; tert-butanol = 14.2%;
(polyester
= 0%).
Example 2
Preparation of a DMC catalyst with tert-butanol as the organic complexing
ligand
and using a linear polyester (catalyst B).
A solution of 12.5 g (91.5 mmol) zinc chloride in 20 ml distilled water is
added to a
solution of 4 g (12 mmol) potassium hexacyanocobaltate in 70 ml distilled
water
with vigorous stirnng (24,000 rpm). Immediately thereafter, a mixture of 50 g
tert-
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butanol and 50 g distilled water is added to the suspension formed and the
mixture is
then stirred vigorously (24,000 rpm) for 10 min. A mixture of 1 g of a linear
polyester of adipic acid and ethylene glycol (poly(ethylene adipate)) having
an
average molecular weight of 2,000 (OH number = 55 mg KOH/g), 1 g tert-butanol
and 100 g distilled water is then added and the mixture is stirred (1,000 rpm)
for 3
min. The solid is isolated by filtration, then stirred (10,000 rpm) with a
mixture of
70 g tert-butanol, 30 g distilled water and 1 g of the above polyester and
filtered off
again. Finally, it is stirred (10,000 rpm) once more with a mixture of 100 g
tert-
butanol and 0.5 g of the above polyester for 10 min. After filtration, the
catalyst is
dried to constant weight at 50°C under normal pressure.
Yield of dried pulverulent catalyst: 4.87 g
Elemental analysis and thermogravimetric analysis:
cobalt = 10.0%, zinc = 20.9%, tert-butanol = 7.5%, polyester = 22.1%
Example 3
Preparation of a DMC catalyst with tert-butanol as the organic complexing
ligand
and using a partly branched polyester (catalyst C).
As example 2, but with:
use of a polyester, weakly branched by trimethylolpropane, of adipic acid and
diethylene glycol having an average molecular weight of 2,300 (OH number = 50
mg KOH/g) instead of the polyester from example 2.
Yield of dried pulverulent catalyst: 3.85 g
Elemental analysis and thermogravimetric analysis:
cobalt = 12.2%, zinc = 25.7%, tert-butanol = 7.1%, polyester = 12.3%
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Comparison example 4
Preparation of a DMC catalyst using a polyester without tent-butanol as the
organic
complexing ligand (catalyst D).
A solution of 12.5 g (91.5 mmol) zinc chloride in 20 ml distilled water is
added to a
solution of 4 g (12 mmol) potassium hexacyanocobaltate in 70 ml distilled
water
with vigorous stirring (24,000 rpm). Inunediately thereafter, a mixture of 1 g
of the
polyester from example 2 and 100 g distilled water is added to the suspension
formed and the mixture is then stirred vigorously (24,000 rpm) for 10 min. The
solid is isolated by filtration, then stirred (10,000 rprn) with a mixture of
1 g
polyester and 100 g distilled water for 10 min and filtered off again.
Finally, it is
stirred (10,000 rpm) once more with a mixture of 0.5 g polyester and 100 g
distilled
water for 10 min. After filtration, the catalyst is dried to constant weight
at 50°C
under normal pressure.
Yield of dried pulverulent catalyst: 5.27 g
Elemental analysis and thermogravimetric analysis:
cobalt = 9.5%, zinc = 16.6%, polyester = 25.0% (tert-butanol = 0%)
Comparison example 5
Preparation of a DMC catalyst with tert-butanol as the organic complexing
ligand
and using a polyether (catalyst E, synthesis according to EP 700 949).
A solution of 12.5 g (91.5 mmol) zinc chloride in 20 ml distilled water is
added to a
solution of 4 g (12 mmol) potassium hexacyanocobaltate in 70 ml distilled
water
with vigorous stirring (24,000 rpm). Immediately thereafter, a mixture of 50 g
tert-
butanol and 50 g distilled water is added to the suspension formed and the
mixture is
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then stirred vigorously (24,000 rpm) for 10 min. A mixture of 1 g
polypropylene
glycol having an average molecular weight of 2,000 (OH number = 56 mg KOH/g),
1 g tert-butanol and 100 g distilled water is then added and the mixture is
stirred
(1,000 rpm) for 3 min. The solid is isolated by filtration, then stirred
(10,000 rpm)
with a mixture of 70 g tent-butanol, 30 g distilled water and 1 g of the above
polyether for 10 min and filtered off again. Finally, it is stirred (10,000
rpm) once
more with a mixture of 100 g tert-butanol and 0.5 g of the above polyether for
10
min. After filtration, the catalyst is dried to constant weight at 50°C
under normal
pressure.
Yield of dried pulverulent catalyst: 6.23 g
Elemental analysis and thermogravimetric analysis:
cobalt = 11.6%, zinc = 24.6 %, tert-butanol = 3.0%, polyether = 25.8%
Preparation of polyether-polyols
General procedure
50 g polypropylene glycol starter (molecular weight = 1,000 glmol) and 3 - 20
mg
catalyst (15 - 100 ppm, based on the amount of polyether-polyol to be
prepared) are
initially introduced into a 500 ml pressure reactor under an inert gas (argon)
and are
heated up to 105°C, while stirnng. Propylene oxide (approx. 5 g) is
then metered in
all at once, until the overall pressure has risen to 2.5 bar. Further
propylene oxide is
metered in again only when an accelerated drop in pressure in the reactor is
observed. This accelerated drop in pressure indicates that the catalyst is
activated.
The remaining propylene oxide ( 145 g) is then metered in continuously under a
constant overall pressure of 2.5 bar. When metering of the propylene oxide is
complete and after an after-reaction time of 5 hours at 105°C, volatile
contents are
distilled off at 90°C (1 mbar) and the product is then cooled to room
temperature.
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The polyether-polyols obtained were characterized by determination of the OH
numbers, the double bond contents and the molecular weight distributions Mw/M"
(MALDI-TOF-MS).
The course of the reaction was monitored with the aid of time/conversion
curves
(propylene oxide consumption [g] v. reaction time [min]). The induction time
was
determined from the point of intersection of the tangent at the steepest point
of the
time/conversion curve with the extended base line of the time/conversion
curve.
The propoxylation times, which indicate the catalyst activity, correspond to
the
period between catalyst activation (end of the induction period) and the end
of the
propylene oxide metering.
The total reaction time is the sum of the induction and propoxylation time.
Comparison example 6
Preparation of polyether-polyol with catalyst A (100 ppm)
Induction time: 290 min
Propoxylation time: 165 min
Total reaction time: 455 min
Polyether-polyol: OH number (mg KOH/g): 28.5
double bond content (mmol/kg): 6
M~"/M": 1.12
Example 7
Preparation of polyether-polyol with catalyst B (100 ppm)
Induction time: 80 min
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Propoxylation time: SS min
Total reaction time: 135 min
Polyether-polyol: OH number (mg KOH/g): 29.7
double bond content (mmol/kg): 5
M,H/M": 1.04
Example 8
Preparation of polyether-polyol with catalyst C (100 ppm)
Induction time: 70 min
Propoxylation time: 50 min
Total reaction time: 120
min
Polyether-polyol: OH number (mg KOH/g): 29.6
double bond content (mmol/kg):S
M,~IM": 1.04
Comparison example 9
Preparation of polyether-polyol with catalyst D (100 ppm)
Induction time: > 700 min
Propoxylation time: no activity
A comparison between examples 7 - 8 and comparison example 6 illustrated that
in
the preparation of polyether-polyols with the DMC catalysts according to the
invention comprising an organic complexing ligand (tent-butanol) and a
polyester,
significantly reduced induction times occur compared with a DMC catalyst
comprising only an organic complexing ligand (tent-butanol), and that the
catalysts
according to the invention at the same time have a greatly increased activity
(detectable from the substantially shortened propoxylation times).
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Comparison example 9 shows that a DMC catalyst which comprises no organic
complexing ligand but only a polyester is inactive.
Example 10:
Preparation of polyether-polyol with catalyst C (15 ppm)
Total reaction time 335 min
Polyether-polyol: OH number (mg KOH/g): 27.4
double bond content (mmol/kg): 5
M~,,/M": 1.05
Without removal of the catalyst, the metal content in the polyol: Zn = 4 ppm,
Co = 2
ppm.
Example 10 shows that because of their significantly increased activity, the
new
DMC catalysts according to the invention can be employed in polyether-polyol
preparation in such low concentrations that separation of the catalyst from
the polyol
can be omitted.
Comparison example 11:
Preparation of polyether-polyol with catalyst E (15 ppm)
Total reaction time 895 min
Polyether-polyol: OH number (mg KOI-1/g): 29.8
double bond content (mmol/kg): 6
MW/M": 1.04
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A comparison between example 10 and comparison example 11 shows that the new
DMC catalysts according to the invention comprising an organic complexing
ligand
(tert-butanol) and a polyester are substantially more active than the highly
active
DMC catalysts known hitherto, which comprise an organic complexing ligand
(tert-
butanol) and a polyether (of comparable molecular weight and OH number to the
polyesters employed in the catalysts according to the invention). Polyether-
polyol
preparation with the new catalysts according to the invention is therefore
possible in
significantly shortened total reaction times.
