U.S. patent application number 10/136208 was filed with the patent office on 2002-12-05 for process for preparing polyether polyols.
Invention is credited to Mulhaupt, Rolf, Rexin, Ornulf.
Application Number | 20020183561 10/136208 |
Document ID | / |
Family ID | 7683680 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020183561 |
Kind Code |
A1 |
Rexin, Ornulf ; et
al. |
December 5, 2002 |
PROCESS FOR PREPARING POLYETHER POLYOLS
Abstract
The invention is directed to a process for preparing a polyether
polyol by the polyaddition of an alkylene oxide on to a starter
compound containing active hydrogen atoms under basic catalysis in
the presence of phosphonium cations.
Inventors: |
Rexin, Ornulf; (Freiburg,
DE) ; Mulhaupt, Rolf; (Freiburg, DE) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
7683680 |
Appl. No.: |
10/136208 |
Filed: |
May 1, 2002 |
Current U.S.
Class: |
568/679 ;
564/12 |
Current CPC
Class: |
C08G 65/105 20130101;
C08G 65/2675 20130101 |
Class at
Publication: |
568/679 ;
564/12 |
International
Class: |
C07C 041/03 |
Foreign Application Data
Date |
Code |
Application Number |
May 4, 2001 |
DE |
10121807.9 |
Claims
What is claimed is:
1. A process for preparing a polyether polyol by the polyaddition
of an alkylene oxide on to a starter compound containing active
hydrogen atoms under basic catalysis comprising converting from 0.1
to 90 mol % of the active hydrogen atoms of the starter compound to
phosphonium salts before the polyaddition of the alkylene oxide,
wherein the phosphonium cation is represented by the general
structure (I) 3wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 can be
identical or different and, independently of one another, can be
any hydrocarbon group having 1 to 30 carbon atoms, wherein no
double bond of the phosphorus to an uncharged nitrogen atom is
present.
2. The process of claim 1, wherein the phosphonium cation is
represented by the general structure (2) 4wherein R.sup.5 to
R.sup.12 can be identical or different and, independently of one
another, can be any hydrocarbon group having 1 to 30 carbon
atoms.
3. The process of claim 2, wherein the phosphonium cation is
tetrakis-[cyclohexyl(methyl)amino]-phosphonium ion.
4. A polyether polyol prepared by the process of claim 1.
5. A process for preparing a polyether polyol comprising the steps
of: (a) providing a starter compound containing active hydrogen
atoms; (b) adding phosphonium alcoholate to the starter compound
containing active hydrogen atoms to form a reaction mixture; (c)
reacting the reaction mixture with an alkylene oxide to form a
polyether polyol containing reactive mixture; (d) neutralizing the
polyether polyol containing reactive mixture; and (e) isolating the
polyether polyol from the polyether polyol containing reactive
mixture.
6. A polyether polyol prepared by the process of claim 5.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention is directed to a process for preparing
polyether polyols by polyaddition of alkylene oxides on to starter
compounds containing active hydrogen atoms under basic catalysis in
the presence of phosphonium cations.
BACKGROUND OF THE INVENTION
[0002] Polyether polyols are produced by polyaddition of alkylene
oxides, for example, ethylene oxide, propylene oxide and butylene
oxide, on to starter compounds containing active hydrogen atoms,
for example, alcohols, amines, acid amides and phenols. Polyether
polyols are used to prepare polyurethane plastics, surfactants and
lubricants.
[0003] Polyaddition of epoxides on to starter compounds is
typically carried out by alkali catalysis. Alkali metal hydroxides
are conventionally used in alkali catalysis. Producing polyether
polyols under alkali catalysis, however, has at least two
disadvantages: 1. long reaction times (greater than 5 hours); and
2. expensive working-up of the polyether polyols in order to
neutralize the alkaline polymers. See, for example, U.S. Pat. Nos.
4,129,718, 4,482,750, 4,029,879, and JP 7/326391, as well as
Encyclopedia of Polymer Science & Eng., Vol. 6, New York 1986,
pages 273-307).
[0004] Base-catalyzed re-arrangement of epoxides, for example,
propylene oxide, into allyl or propenyl alcohols, which proceeds as
a side reaction in the preparation of polyether polyols, leads to
undesirable mono-functional polyethers with terminal double bonds,
so-called "mono-ols".
[0005] EP 763 555, EP 791 600, EP 879 838 and EP 916 686 all
describe alkylene oxide polymerization by basic catalysis with
phosphazene or phosphonium bases. These systems are all
characterized by the presence of at least one P.dbd.N double bond.
Basic catalysis systems used to produce polyether polyols have
hiqher activities compared to alkali catalysis systems. As a
result, reaction times are shorter and reactions are more
selective, which leads to polyether polyols with low mono-ol
content and high head-tail content.
[0006] Basic catalysis systems are, however, expensive to use.
Additionally, the high cost of the catalysts used in basic
catalysis systems adds to the expense of using such systems. Also,
alkylene oxide polymerization by basic catalysis produces high
molecular weight polyether polyols having an undesirable high
double bond content. Furthermore, the stability of the phosphazene
bases of basic catalysis systems is too low for industrial use,
especially if the counter-ion is to be re-generated and re-used for
further polyaddition cycles.
SUMMARY OF THE INVENTION
[0007] The object of the present invention is to provide a process
for preparing polyether polyols by polyaddition of alkylene oxides
on to starter compounds containing active hydrogen atoms under
basic catalysis in the presence of phosphonium cations.
[0008] Compared with alkali metal hydroxides (e.g. KOH),
phosphonium ions have higher activities. Additionally, phosphonium
ions are more easily prepared and are therefore less expensive to
use than the phosphazene bases known to date. Furthermore,
phosphonium ions have a higher stability than the known phosphazene
bases, which is very important not only for polyaddition, but also
for re-generating and re-using the counter-ion.
DETAILED DESCRIPTION OF THE INVENTION
[0009] Compounds having molecular weights of 18 to 2,000 g/mol and
1 to 20 hydroxyl, thiol and/or amino groups are useful in the
present invention as starter compounds containing active hydrogen
atoms. Examples of such compounds are: methanol, ethanol, butanol,
phenol, ethylene glycol, diethylene glycol, polypropylene glycol,
1,4-butanediol, hexamethylene glycol, bisphenol A,
trimethylolpropane, glycerol, pentaerythritol, sorbitol, sucrose,
degraded starch, water, methylamine, ethylamine, propylamine,
butylamine, stearylamine, aniline, benzylamine, o- and p-toluidine,
.alpha.,.beta.-naphthylamine, ammonia, ethylenediamine,
propylenediamine, 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5- or
1,6-hexamethylenediamine, such as o-, m- and p-phenylenediamine,
2,4-toluylenediamine, 2,6-toluylenediamine,
2,2'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane and
4,4'-diaminodiphenylmethane and diethylenediamine, and compounds
which contain functionalizable starter groups, such as
allylglycerol, 10-undecenylamine, dibenzylamine, allyl alcohol and
10-undecenol.
[0010] Alkylene oxides preferably used in the present invention are
ethylene oxides, propylene oxides, butylene oxides, styrene oxides,
vinyloxiranes and mixtures thereof. The build-up of the polyether
chains by alkoxylation can be accomplished by using only one
monomeric epoxide, or randomly or blockwise with 2 or 3 different
monomeric epoxides. Further details in this regard can be found in
Ullmanns Encyclopdie der industriellen Chemie, Volume A21, 1992, p.
670 et seq.
[0011] The phosphonium cations useful in the present invention are
represented by the structure (I) 1
[0012] wherein
[0013] R.sup.1, R.sup.2, R.sup.3 and R.sup.4 can be identical or
different and, independently of one another, can be any hydrocarbon
group having 1 to 30 carbon atoms, such as, for example, alkyl,
aryl, arylalkyl, alkenyl or cycloalkyl, a thiol or thiophenol group
or a primary, secondary or cyclic amino group, wherein no double
bond of the phosphorus to an uncharged nitrogen atom may be
present. In each case, two radicals from R.sup.1, R.sup.2, R.sup.3
and R.sup.4 can be joined together to a ring structure.
[0014] R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are preferably primary
or secondary amino groups. The phosphonium cations preferably used
in the present invention are represented by the structure (2) 2
[0015] wherein
[0016] R.sup.5 to R.sup.12 can be identical or different and,
independently of one another, can be any hydrocarbon group having 1
to 30 carbon atoms, such as, for example, alkyl, aryl, arylalkyl,
alkenyl or cycloalkyl, a thiol or a thiophenol groups or a primary,
secondary or cyclic amino group. In each case, two radicals from
R.sup.5 to R.sup.12 can be joined together to a ring structure.
[0017] More preferably, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are
secondary amino groups, for example
tetrakis-[cyclohexyl(methyl)amino]-ph- osphonium counter-ions
wherein R.sup.5, R.sup.7, R.sup.9 and R.sup.11 are methyl and
R.sup.6, R.sup.8, R.sup.10 and R.sup.12 are cyclohexyl. The
phosphonium cations useful in the present invention can have any
organic or inorganic anions as the counter-ion.
[0018] Tetrakis[cyclohexyl(methyl)amino]phosphonium
tetrafluoroborate has a high stability with a half-life of 67
hours. This compound can be prepared in a simple synthesis
sequence. See P. Wenzel, Dissertation, University of Freiburg 1998,
163. Tetrakis-(cyclohexylamino)-phosphonium chloride is prepared by
first reacting cyclohexylamine with phosphorus pentachloride in
methylene chloride. The chloride formed is then converted with
sodium iodide into the iodide, which is then converted with aqueous
sodium tetrafluoroborate solution into the desired
tetrafluoroborate. Next, tetrakis-(cyclohexylamino)-phosphonium
tetrafluoroborate is permethylated with dimethyl sulfate under
phase transfer conditions to give
tetrakis-[cyclohexyl(methyl)amino]phosphonium tetrafluoroborate,
hereinafter abbreviated as N.sub.4P.sup.+BF.sub.4.sup.- -.
[0019] To prepare the cation, for example, any desired salt,
preferably tetrafluoroborate salts of the phosphonium compounds,
are reacted with alkali metals or alkaline earth metal alcoholates,
preferably potassium methylates. The poorly soluble alkali metal or
alkaline earth metal terafluoroborates, preferably potassium
tetrafluoroborates, precipitate out. Any reactive volatile reaction
products (for example water or alcohol) formed here are removed
(e.g., by distillation). Typically, 0.5 to 2 wt. % of the
phosphonium salt, based on the total weight of the polyether polyol
to be prepared, is used in the present invention.
[0020] Starter compounds containing active hydrogen atoms are
partly de-protonated by phosphonium alcoholates. Reactive volatile
reaction products (e.g. water or alcohol) formed here are removed,
for example, by distillation. The degree of de-protonation is from
0.1 mol % to 90 mol %, preferably 1 mol % to 20 mol % of the total
amount of active hydrogen atoms in the starter compound.
[0021] Polyaddition by the process of the present invention is
carried out by metering the alkylene oxide into the cation. The
speed of metering the alkylene oxide is chosen so that adequate
temperature control is ensured under reaction conditions, such as
reaction temperature and hydroxyl and catalyst concentration.
Polyaddition is typically carried out at temperatures in the range
of from 20 to 200.degree. C., preferably, 40 to 180.degree. C.,
more preferably, 50 to 150.degree. C. The reaction can be carried
out under an overall pressure of 0.0001 to 20 bar. The polyaddition
can be carried out in bulk or in an inert organic solvent, such as
e.g. toluene, xylene, ethylbenzene, tetrahydrofuran ("THF"), glyme
or diglyme. The amount of solvent is usually 10 to 30 wt. %, based
on the total weight of polyether polyol to be prepared. The
reaction times are in the range of from a few minutes to several
days, preferably, several hours.
[0022] The polyaddition can be carried out continuously or
discontinuously, e.g. in a batch or a semi-batch process.
[0023] All known techniques for working-up polyether polyols for
use in polyurethane production can, in principle, be used for
working-up the alkaline polymers. See H. R. Friedel, Reaction
Polymers, Hanser Verlag, Munich 1992, p. 79. Working-up the
polyether polyol is preferably carried out by neutralization. The
neutralization is preferably carried out by acidification with
dilute mineral acid (e.g. sulfuric acid or phosphoric acid) with
subsequent filtration or treatment with an adsorbent (e.g.
magnesium silicate) or by filtration over an acid ion exchanger.
Further purification by precipitation (e.g. from methanol in
acetone) can follow. Finally, the product is freed from readily
volatile contents under reduced pressure at temperatures of 20 to
200.degree. C.
[0024] The starting product N.sub.4P.sup.+BF.sub.4.sup.- can be
recovered from the acid ion exchanger with a mixture of
tetrafluoroboric acid and methanol. After purification of the salt,
e.g. by recrystallization, it can be used again for catalysis.
[0025] The number-average molecular weight of the polyether polyols
prepared by the process according to the present invention are in
the range of from 100 to 50,000 g/mol, preferably, 1,000 to 20,000
g/mol. The molecular weight can be determined by gel permeation
chromatography ("GPC"), MALDI-TOF (Matrix Assisted Laser Desorption
Ionisation--Time of Flight) mass spectrometry or, preferably, by
determination of the OH number. The polydispersities of the
polyether polyols are less than 1.2, preferably less than 1.1, and
can be determined with a GPC calibrated with polyethylene glycol
standards.
EXAMPLES
[0026] The commercially obtainable phosphazene bases
1-tert-butyl-4,4,4-tris-(dimethylamino)-2,2-bis-[tris-(dimethylamino)-pho-
sphoranylideneamino]-2.lambda..sup.5,4.lambda..sup.5-catenadi-(phosphazeni-
um) tetrafluoroborate, hereinafter abbreviated as
BuP.sub.4.sup.+BF.sub.4.- sup.-, and
1,1,1,3,3,3-hexakis-(dimethylamino)-diphosphazenium
tetrafluoroborate, hereinafter abbreviated as
P.sub.2.sup.+BF.sub.4.sup.-- , were used in the comparison
Examples.
Example 1
[0027] (long side heading)
[0028] Tetrakis[cyclohexyl(methyl)amino]phosphonium ion,
hereinafter abbreviated as N.sub.4P.sup.+, as the cation:
[0029] 780 mg of the phosphonium salt N.sub.4P.sup.+BF.sub.4.sup.-
was dissolved in methanol and the solution was stirred with a
stoichiometric amount of a 3.60 M solution of potassium methylate
in methanol at 25.degree. C. for 1 hour. The colorless precipitate
formed was filtered through a filter crucible (pore 4) and washed
with methanol. The solvent was removed under reduced pressure. The
N.sub.4P.sup.+OMe.sup.- obtained was initially introduced with 2.72
ml dipropylene glycol into a 250 ml glass reactor under inert gas
conditions (argon) and the mixture was stirred at 90.degree. C. for
1 hour. The methanol formed was removed in vacuo. 100 ml distilled
propylene oxide was metered in at an oil bath temperature of
130.degree. C. under reflux such that a small excess of monomer was
always present in the reactor. When the addition had ended the
reaction mixture was dissolved in 150 ml methanol and neutralized
with an acid ion exchanger (AMBERLITE.RTM. IR-120, Merck KGaA,
D-64295 Darmstadt). The ion exchanger was filtered off and the
filtrate was freed from the solvent under reduced pressure. 54 g of
a colorless, viscous liquid (.eta.=682 mPa.s/25.degree. C.) with a
molecular weight of 3,500 g/mol (degree of polymerization 58) and a
polydispersity of 1.05 was obtained. The OH number was 38.0 mg
KOH/g. The polyol contained 38 mmol/kg of unsaturated
compounds.
Example 2 (Comparison)
[0030] 1,1,1,3,3,3-Hexakis-(dimethylamino)-diphosphazenium,
hereinafter abbreviated as P.sub.2.sup.+, as the cation:
[0031] In a procedure analogous to Example 1, the cation was
prepared from 886 mg P.sub.2.sup.+BF.sub.4.sup.-, 0.58 ml potassium
methylate solution (3.60 M) and 2.72 ml dipropylene glycol. 100 ml
distilled propylene oxide was metered in. After working up, 75 g of
a colorless, viscous liquid (.eta.=553 mPa.s/25.degree. C.) with a
molecular weight of 3,300 g/mol (degree of polymerization 55) and a
polydispersity of 1.08 was obtained. The OH number was 36.3 mg
KOH/g. The polyol contained 55 mmol/kg of unsaturated
compounds.
Example 3 (Comparison)
[0032]
1-tert-Butyl-4,4,4-tris-(dimethylamino)-2,2-bis-[tris-(dimethylamin-
o)phosphoranylideneamino]-2.lambda.5,4.lambda.5-catenadi-(phosphazene),
hereinafter abbreviated as .sup.tBuP.sub.4H.sup.+, as the
cation:
[0033] In a procedure analogous to Example 1, the cation was
prepared from 1.50 g .sup.tBuP.sub.4.sup.+BF.sub.4.sup.-, 0.58 ml
potassium methylate solution (3.60 M) and 2.72 ml dipropylene
glycol. 100 ml distilled propylene oxide was metered in. After
working up, 79 g of a colorless, viscous liquid (.eta.=652
mPa.s/25.degree. C.) with a molecular weight of 3,300 g/mol (degree
of polymerization 58) and a polydispersity of 1.03 was obtained.
The OH number was 32.4 mg KOH/g. The polyol contained 60 mmol/kg of
unsaturated compounds.
Example 4
[0034] Regeneration of N.sub.4P.sup.+BF.sub.4.sup.-:
[0035] The ion exchanger containing the cation N.sub.4P.sup.+ is
stirred with a mixture of tetrafluoroboric acid and methanol in a
ratio of 1:8 at about 65.degree. C. for several hours. After the
ion exchanger has been filtered off, the
N.sub.4P.sup.+BF.sub.4.sup.- is precipitated out by the addition of
water. The salt can be re-crystallized from isopropanol.
Example 5
[0036] Determination of the Half-Lives of the Cations:
[0037] The stability of the phosphazene and phosphonium cations was
characterized by determination of the half-lives. See P. Wenzel,
Dissertation, University of Freiburg 1998, 163. For this, the
stability of the cation to the strongly basic and nucleophilic
hydroxide ion in the presence of water was measured. A defined
amount of the cation to be investigated was heated at 100.degree.
C. in the form of the chloride salt under phase transfer conditions
in a system of 50% aqueous sodium hydroxide solution and
chlorobenzene for up to 100 hours. The products were then extracted
with methylene chloride and isolated. The content of un-dissociated
cation was subjected to fractional crystallization from methanolic
solution with sodium tetraphenylborate. From the amount of cation
isolated, the half-life can be calculated by first order kinetics.
The results are summarized in Table 1.
1TABLE 1 Half-Life Of The Cations Cation Half-life 1.sub.1/2 [h]
N.sub.4P.sup.+ 67 P.sub.2.sup.+(Comparison) 8
.sup.tBuP.sub.4H.sup.+(Comparison) 45
* * * * *