Note: Descriptions are shown in the official language in which they were submitted.
CA 02385085 2002-03-15
1
METHOD FOR PRODUCING FLEXIBLE BLOCK FOAM POLYOLS
The present invention relates to a process for preparing
polyether alcohols, to the polyether alcohols prepared by this
process and to their use for producing polyurethanes.
Polyether alcohols are used in large quantities for producing
polyurethanes. They are usually prepared by catalytic addition of
lower alkylene oxides, in particular ethylene oxide and propylene
oxide, onto H-functional initiator substances. Catalysts used are
usually basic metal hydroxides or salts, with potassium hydraxide
having the greatest practical importance.
The alkylene oxides are usually added on as a block or as a
random mixture. In the blockwise molecular addition, only one
alkylene oxide at a time is added on, while in the random
molecular addition, a mixture of alkylene oxides is present in
the reaction mixture.
In the industry, ethylene oxide and propylene oxide axe usually
used as alkylene oxides, since they are readily available and
inexpensive. The reactivity of ethylene oxide is higher than that
of propylene oxide, so that the molecular addition of ethylene
oxide proceeds at a higher reaction rate. To increase the
space-time yield in the preparation of polyether alcohols it
would be desirable for the proportion of ethylene oxide in the
polyether alcohol to be as high as possible. Provision of
polyether alcohols which are intended for use in flexible foams
with terminal ethylene oxide blocks is known and customary. The
associated increase in the number of primary hydroxyl groups in
the polyether alcohols results in an increase in their reactivity
in the reaction with polyisocyanates. However, the increase in
the ethylene oxide content of the polyether alcohol also results
in an increase in the hydrophilicity of the polyether alcohol,
which can lead, inter alia, to undesirable gel formation in the
polyether alcohols.
Furthermore, in the synthesis of polyether alcohols having long
chains, as are used for producing flexible polyurethane foams,
increasing chain growth is associated with secondary reactions
which lead to defects in the chain structure. These by-products
are referred'to as unsaturated constituents and lead to a
deterioration in the properties of the resulting polyurethanes.
Many attempts have therefore been made in the past to prepare
polyether alcohols having a low content of unsaturated
constituents. In particular, the alkoxylation catalysts used have
, ~05~/50735 CA 02385085 2002-03-15
been altered in a targeted way in an attempt to achieve this.
Thus, EP-A-268 922 proposes using cesium hydroxide. Although this
enables the content of unsaturated constituents to be reduced,
cesium hydroxide is expensive and disposing of it is
problematical.
Furthermore, the use of multimetal cyanide complexes, usually
zinc hexacyanometalates, also known as DMG catalysts, for
preparing polyether alcohols having low contents of unsaturated
IO constituents is also known. There is a large number of documents
in which the preparation of such compounds is described. Thus,
DD-A-203 735 and DD-A-203 734 describe the preparation of
polyetherols using zinc hexacyanocobaltate.
I5 The preparation of the zinc hexacyanometalates is also known.
These catalysts are usually prepared by reacting solutions of
metal salts such as zinc chloride with solutions of alkali metal
or alkaline earth metal cyanometalates, e.g. potassium
hexacyanocobaltate. A water-miscible, heteroatom-containing
20 component is generally added to the resulting suspension
immediately after the precipitation step. This component can also
be present initially in one or both starting solutions. This
water-miscible, heteroatom-containing component can be, for
example, an ether, polyether, alcohol, ketone or a mixture
25 thereof. Such processes are described, for example, in US
3,278,457, US 3,278,458, US 3,278,459, US 3,427,256, US
3,427,334, US 3,404,109.
Polyether alcohols used fox producing flexible slabstock foams
30 generally have a complete propylene oxide inner block which can
make up as much as 40% by weight of the total polyol bound
directly to the initiator substance and on this propylene oxide
inner block have mixed blocks of propylene oxide and ethylene
oxide which make up at least 60% by weight of the total polyol
35 and contain at least 2% by weight of ethylene oxide. These
polyols are generally prepared using basic catalysts.
WO-A-97/27,236 describes the preparation of a flexible slabstock
foam~polyol in which at least one propylene oxide inner block is
added on using multimetal cyanides as catalyst. However, this
40 process does not permit a further increase in the ethylene oxide
content of the polyether alcohol without the abovementioned
disadvantages.
0050/50735 CA 02385085 2002-03-15
It is an object of the present invention to develop polyether
alcohols which have a high ethylene oxide content without there
being a significant increase in the hydrophilicity of the
product.
We have found that this object is achieved by a polyether alcohol
which can be prepared by ring-opening polymerization of ethylene
oxide and alkylene oxides having at least 3 carbon atoms, which
comprises an inner block of ethylene oxide or a mixture of
ethylene oxide and alkylene oxides having at least 3 carbon
atoms, and attached to this a block comprising at least one
alkylene oxide having at least 3 carbon atoms or a mixture of
ethylene oxide and alkylene oxides having at least 3 carbon
atoms, preferably propylene oxide, where the mixed blocks
preferably contain at least 2% by weight and not more than ZO% by
weight of ethylene oxide, based on the mixture.
The present invention accordingly provides polyether alcohols
which can be prepared by ring-opening polymerization of ethylene
oxide and propylene oxide onto H-functional initiator substances,
wherein not more than 40% by weight, based on the weight of the
polyether alcohol, of ethylene oxide or a mixture of ethylene
oxide and alkylene oxides having at least 3 carbon atoms, where
the mixture has an ethylene oxide content of at least 98% by
weight, based on the mixture, is added onto the initiator
substance and subsequently at least one alkylene oxide having at
least 3 carbon atoms or a mixture of ethylene oxide and at least
one alkylene oxide having at least 3 carbon atoms, where the
mixture has a maximum ethylene oxide content of 20% by weight,
based on the mixture, is added on.
If a mixture of ethylene oxide and at least one alkylene oxide
having at least 3 carbon atoms is added on, the content of
ethylene oxide should be at least 0.5% by weight, based on the
mixture.
As alkylene oxides having at least 3 carbon atoms in the
molecule, preference is given to using propylene oxide, butylene
oxide and isobutylene oxide and also any mixtures of at least two
of the alkylene oxides mentioned, particularly preferably
propylene oxide.
In a preferred embodiment of the present invention, ethylene
oxide can be added onto the polyether alcohol at the end of the
chain, i.e. after the molecular addition of the alkylene oxides
having at least 3 carbon atoms or of the mixture of ethylene
oxide and alkylene oxides having at least 3 carbon atoms. The
~~ 005/50735 CA 02385085 2002-03-15
4
amount of this ethylene oxide added onto the end of the chain is
preferably not more than 15% by weight, based on the weight of
the polyether alcohol. Such polyether alcohols are preferably
used for producing cold-cure polyurethane foams. Polyether
alcohols of the present invention without this ethylene oxide end
block are preferably used for producing flexible polyurethane
foams, in particular flexible slabstock foams.
It has surprisingly been found that the hydrophilicity of the
polyether alcohols of the present invention is significantly
lower than that of conventional polyether alcohols containing the
same amount of ethylene oxide in the polyether chain but having a
different distribution of alkylene oxides in the chain.
The present invention further provides a process for preparing
the above-described polyether alcohols. The polyether alcohols of
the present invention are prepared by ring-opening polymerization
of the alkylene oxides ethylene oxide and the alkylene oxides
having at least 3 carbon atoms onto H-functional initiator
substances in the presence of catalysts.
In a preferred embodiment of the process of the present
invention, the molecular addition of the total amount of alkylene
oxide is carried out in the presence of basic catalysts. Basic
catalysts which can be used are, for example, amines, basic
salts, metal oxides and metal hydroxides. Preference is given to
using alkali metal and/or alkaline earth metal hydroxides. In
industry, potassium hydroxide is usually used.
In a further preferred embodiment of the process of the present
invention, multimetal cyanides, frequently also referred to as
DMC catalysts, are used as catalyst for the molecular addition of
the alkylene oxides. The advantages of using these catalysts are
firstly the higher reaction rate in the molecular addition of the
alkylene oxides and secondly the fact that the polyether alcohols
prepared in this way have a lower content of unsaturated
constituents. However, this embodiment has the disadvantage that
there can be a delayed start of the reaction at the beginning
when using DMC catalysts.
In further preferred embodiments of the process of the present
invention, the various sections of the polyether chain are added
on using different catalysts. Thus, it is advantageous to add on
an ethylene oxide block at the beginning of the chain using basic
catalysts and to add on the subsequent block consisting entirely
or predominantly of alkylene oxides having at least 3 carbon
atoms using DMC catalysts. The ethylene oxide block which may, if
0050/50735 CA 02385085 2002-03-15
desired, be present at the end of the chain can likewise be added
on by means of DMC catalysts, but preferably by means of basic
catalysts. This procedure has the advantage that the delay which
frequently occurs at the start of the reaction when using
5 multimetal cyanide catalysts is avoided. This is balanced by
increased costs due to the additional purification step.
When using different catalysts, it may be necessary to purity the
polyether alcohol to remove catalyst prior to changing the
catalysts. Particularly when changing from basic catalysts to DMC
catalysts, a thorough purification is usually carried out because
traces of the basic catalyst, in particular the alkali metal
hydroxides customarily used, can poison the DMC catalyst.
The invention further provides polyurethanes which can be
produced by reacting polyisocyanates with compounds having at
least two hydrogen atoms which are reactive toward isocyanate
groups, wherein the polyether alcohols of the present invention
are used as compounds having at least two hydrogen atoms which
are reactive toward isocyanate groups. The polyether alcohols of
the present invention are preferably used for producing flexible
polyurethane foams, with the polyether alcohols without a
terminal ethylene oxide block being used, in particular, for
producing slabstock foams and not-cure molded foams and the
polyether alcohols having a terminal ethylene oxide block being
used, in particular, for producing cold-cure molded foams.
As initiator substances for preparing the polyetherols of the
present invention, use is made of the customary polyfunctional
alcohols having from 2 to 8 hydroxyl groups in the molecule. In
particular, 2- and/or 3-functional alcohols, for example ethylene
glycol, propylene glycol, glycerol or trimethylolpropane, are
used for preparing polyether alcohols as are customarily used for
producing flexible polyurethane foams.
The polyether alcohols of the present invention preferably have a
molecular weight in the range from 1000 to 100,000.
Alkylene oxides used are, as indicated above, ethylene oxide and
alkylene oxides having at least 3 carbon atoms, in the
abovementioned ratios.
The multimetal cyanides used as catalysts in the process of the
present invention usually have the formula (I)
MZa[P'IZ(CN)b(A)c~d ' fMlgXn ~ h(H2C?) ~ eL (I).
0050/50735 CA 02385085 2002-03-15
6
where
M1 is a metal ion selected from the group consisting of Znz+,
Fez+, Co3+, Niz+, Mnz+, Coz+, Snz+, Pbz+, Mo4+, Mo6+, A13+, V4+,
V5+, Srz+, W4+, W6+, Crz+, Cr3+, Cdz+, _.
M2 is a metal ion selected from the group consisting of Fez+,
Fe3+, Coz+, Co3+, Mnz+, Mn3+, V4+, VS+, Crz+, Cr3+, Rh3+, Ruz+,
Ir3+
and M1 and Mz are identical or different,
A is an anion selected from the group consisting of halide,
hydroxide, sulfate, carbonate, cyanide, thiocyanate,
isocyanate, cyanate, carboxylate, oxalate and nitrate,
X is an anion selected from the group consisting of halide,
hydroxide, sulfate, carbonate, cyanide, thiocyanate,
isocyanate, cyanate, carboxylate, oxalate and nitrate,
L is a water-miscible ligand selected from the group consisting
of alcohols, aldehydes, ketones, ethers, polyethers, esters,
ureas, amides, nitriles and sulfides,
and
a, b, c, d, g and n
are selected so that the compound is electrically neutral,
and
a is the coordination number of the ligand,
f is a fraction or integer greater than or equal to 0 and
h is a fraction or integer greater than or equal to 0.
These compounds are prepared by generally known methods by
combining the aqueous solution of a water-soluble metal salt with
the aqueous solution of a hexacyanometalate compound, in
particular a salt or an acid, and adding a water-soluble ligand
thereto during or after the mixing of the solutions.
Owing to their high activity, the multimetal cyanide compounds
are very well suited to the synthesis of the polyether alcohols
of the present invention. The catalyst concentrations used are
less than 1~ by weight, preferably less than 0.5~ by weight,
particularly preferably less than 1000 ppm, in particular less
.~ 0050/50735 CA 02385085 2002-03-15
_ 7
than 500 ppm, very particularly preferably less than 100 ppm,
based on the total mass of the polyether polyol prepared. The
preparation of the polyether alcohols by means of the multimetal
cyanide compounds can be carried out either continuously or
batchwise. The synthesis can be carried out in suspension, in a
fixed bed, in a moving bed or in a fluidized bed.
As far as the reaction conditions pressure and temperature are
concerned, there is no difference in principle between catalysis
by means of basic compounds and by means of multimetal cyanide
compounds. The molecular addition of the alkylene oxides is
carried out at from 50°C to 200°C, preferably from 90°C
to 150°C,
and at pressures in the range from 0.001 bar to 100 bar,
preferably from 0.001 bar to 20 bar for the molecular addition of
alkylene oxides having at least 3 carbon atoms in the molecule
and preferably from 1 to 40 bar for the molecular addition of
ethylene oxide. Before introducing the alkylene oxides, the
reaction vessel is usually made inert by flushing with an inert
gas, for example nitrogen.
The molecular addition of the alkylene oxides is usually followed
by an after-reaction phase in order to effect complete reaction
of the alkylene oxides.
After the reaction, the polyether alcohol farmed is worked up in
a customary fashion by firstly removing unreacted alkylene oxide
and other volatile constituents from the crude polyether alcohol
by stripping or distillation and, if necessary, removing
suspended material and/or mechanical contamination by means of
filtration.
If the last process step was base-catalyzed, the catalyst has to
be removed as usual from the polyether alcohol. Fox this purpose,
the basic catalyst is usually neutralized with an acid and the
salts formed are removed from the polyether alcohol by means of
filtration.
If the last process step has been catalyzed using multimetal
cyanide compounds, the catalyst can in principle remain in the
polyether alcohol, but it can also be removed if necessary, for
example by means of filtration.
The polyether alcohols of the present invention are very well
suited to the production of polyurethanes, in particular flexible
polyurethane foams. They are very readily compatible with the
other constituents of the polyurethane formulations and have,
despite their comparatively high content of ethylene oxide units
~~5~/50735 CA 02385085 2002-03-15
in the polyether chain, a low hydrophilicity. Owing to the higher
reaction rate of the polymerization of ethylene oxide compared to
propylene oxide, the space-time yield in the preparation of the
polyether alcohols of the present invention is higher than that
in the case of conventional polyether alcohols for the same
application areas. A further increase in the space-time yield can
be achieved when at least part of the alkylene oxides is added on
using multimetal cyanide compounds as catalyst.
The invention is illustrated by the following examples:
Examples 1 and 2
Addition of ethylene oxide onto an initiator substance
Example 1
1115 g of glycerol and 32.5 g of a 47% strength aqueous potassium
hydroxide solution were placed in a 10 1 reactor. The water was
removed at 95-I00°C under a reduced pressure of less than 1 mm of
mercury over a period of 1.5 hours. At 110°C and a nitrogen
prepressure of 3.5 bar abs., 3980 g of ethylene oxide were
metered in over a period of 6 hours. After reaction was complete,
a water pump vacuum was applied, 250 g of Ambosol~ magnesium
silicate and 50 g of water were subsequently added to remove the
catalyst and the polyether alcohol was subsequently filtered and
dewatered by means of distillation.
The polyether alcohol formed had the following properties:
hydroxyl number: 394 mg KOH/g, viscosity at 25°C: 240 mPa*s,
potassium content: 5 ppm.
Example 2
The procedure of Example 1 was repeated, but 612 g of glycerol,
31.7 g of a 47% strength aqueous potassium hydroxide solution and
4356 g of ethylene oxide were reacted.
The polyether alcohol formed had the following properties:
hydroxyl number: 27.9 mg KOH/g, viscosity at 25 °C: 222 mPa*s,
potassium content: 3 ppm.
- 0050/50?35 CA 02385085 2002-03-15
9
Examples 3 and 4
Preparation of the polyether alcohols
The syntheses were carried out in a 10 1 stirred reactor. This
was charged with the reaction products from Examples 1 and 2 at
50°C. The contents of the reactor were made inert by evacuating
three times and each time filling with nitrogen. Degassing was
carried out by evacuation at 105°C and a pressure of less than
1 mbar abs. for 1.5 hours. A double metal cyanide catalyst from
the reaction of zinc acetate with hexacyanocobaltic acid and
tert-butanol were then added. The reactor was again evacuated
three times and each time filled with nitrogen. This was followed
by evacuation to a pressure of less than 1 mbar abs. for about
half an hour with the temperature being increased to 125°C. At
this temperature, a mixture of propylene oxide and ethylene oxide
was added. After a further 30 minutes at 125°C, the polyether
alcohol formed was freed of volatile constituents under reduced
pressure. To remove the catalyst, the polyether alcohol was
filtered through a double layer of a Seitz deep filter (K 900).
The amounts of starting materials used and the properties of the
polyether alcohols prepared are shown in Table 1.
Result:
All polyether alcohols have an inner block of glycerol and
ethylene oxide. In Example 3, this is adjoined by a mixed block
of ethylene oxide and propylene oxide, in Example 4 by a block of
propylene oxide.
Polyether alcohols which have only a small proportion of
unsaturated constituents were obtained. Products having a very
low hydroxyl number can also be obtained by the process of the
present invention. The polyether alcohols have narrow molecular
weight distributions in all cases.
45
~~5~/50735 CA 02385085 2002-03-15
l~
'd
+i
N C
~ GS
ro
~
H +~ __
--
~ .1 o 00
O
~ +.~ o
w
ro o 0
m
tr
fp O O
G
G1
E
~ U o 0
~
M a
o~O
tT O o
'~', M M
'b n o~
O _ n a
S1 C G~ G7OD
ro ,'~ N N
.--.
N
p, ro
ro
N
~ U
O
U N N u1
r1 r1 N N
~f1
',~ n n
N
~
'' ,'i
\
xNx
ro
a ~ M
x
a~ a~
a
a~
O ,C n
~
~
.u o
x
o~
a~ w o ~
.r
N
N 'O
ri
,-1
>,
x
Ga aoo~
o
cd o ao0
1-I N O~
G)
~
'd Q1 d'f7
G~
~
i~
b N
r1 -~N
ro
,~,~ .~'1
...
ro
~
f!1 V .-, N N
W 1.1
O d
;.1 M
~i-~ .~.!
~ ~ n
.F, O r1 C1Ov
~
W
tr~ CL o
C
H
rd
.
GL
r,
o
ro
W o w
x
O W W -iN
W
r1 (17
N G
ro
M C
,. X050/50735 CA 02385085 2002-03-15
- 1 ~.
Examples 5 (comparative example) and 6
Production of foams
In Comparative Example 5 and Example 6, the polyol and isocyanate
components shown in Table 2 were reacted to produce flexible
polyurethane foams. The constituents of the polyol component were
intensively mixed. The isocyanate component was then added while
stirring and the reaction mixture was poured into an open mold in
which it foamed to form the polyurethane foam.
The product properties of the polyurethane foam of the present
invention are likewise summarized in Table 2. The testing
standards used are shown in Table 3.
Table 2:
Production and properties of flexible slabstock foams
Example Example
5 6
(C)
Polyol component Hydroxyl Amount [g] Amount
number [g]
[mgKOI-i/g]
5
Polyol A 48 1000
Polyol from Example 4 48 1000
Water 6233 38 38
BF 2370 10 10
Amine catalyst N 201 560 1,9 1.9
Amine catalyst N 206 426 0.6 0.6
Tin catalyst K 29 0 2.3 2.5
Total 1053 1053.0
Isocyanate component NCO [%] Amount [g) Amount
[g)
TDI80/20 48.3 488.0 488.0
Index 110 110
Test data Unit
Cream time [s] 15 10
Fiber time [s] 90 80
Rise time [s] 90 85
Rise height [mm] 275 265
0050/50735 CA 02385085 2002-03-15
12
Rise height after 5 min [mmJ 270 260
Air permeability [mmWsJ 10 10
Foam density [kg/m3J 25,3 26.4
Compressive strength at [kPaJ 4.7 4.1
40% com-
pression
Tensile strength [kPaJ 79,I 88
Elongation [%J 12I I46
l0 Compressive set at 50% [%J 2.4 2.4
compres-
sion
Polyol A: Glycerol-initiated polyether alcohol having an inner
block of 30 parts by weight of propylene oxide and an adjoining
mixed block of 57 parts by weight of propylene oxide and 10 parts
by weight of ethylene oxide.
Table 3: Testing standards
----.---
Test method Standard
Foarn density DIN 53420
Tensile test (tensile strength,DIN 53571
elongation)
Compressive set DIN 53572
Rebound resilience DIN 53573
Indentation hardness DIN 53576
Compressive strength DIN 53577
35
45
