Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-01-24
2003-04-15
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S671000, C568S672000, C568S689000
Reexamination Certificate
active
06548714
ABSTRACT:
This is the National Phase Application of PCT/EP99/0622, filed Aug. 25, 1999.
The present invention relates to a process for preparing polyether alcohols by ring-opening polymerization of alkylene oxides and to the use of the polyetherols.
Polyether alcohols are important starting materials in the production of polyurethanes. They are usually prepared by catalytic addition of lower alkylene oxides, in particular ethylene oxide and/or propylene oxide, onto H-functional initiator molecules.
At present, the preparation of polyether alcohols is carried out in batch processes in which the catalyst is suspended in the initiator substance.
Catalysts used are usually soluble basic metal hydroxides or salts, with potassium hydroxide having the greatest industrial importance. The major disadvantage of the use of potassium hydroxide as catalyst is that in the preparation of high molecular weight polyether alcohols it results in the formation of unsaturated by-products which reduce the functionality of the polyether alcohols and have a very adverse effect in the production of polyurethanes.
To lower the amount of unsaturated constituents in the product, EP-A 268 922 has proposed using cesium hydroxide as catalyst. However, the use of the expensive cesium hydroxide as catalyst makes the process less economical. Basic metal hydroxides which dissolve in the polyether polyols, e.g. potassium hydroxide and cesium hydroxide, have the further disadvantage that they have to be extracted from the polyetherol at great cost after the synthesis and the resulting waste has to be disposed of.
Another class of substances which are likewise suitable as catalysts for the preparation of polyether polyols is sparingly soluble basic oxides or hydroxides. Such basic oxides or hydroxides can be, for example, alkaline earth metal oxides or hydroxides. Thus, U.S. Pat. No. 5,679,764 describes the use of relatively coarse magnesium oxide powders as alkoxylation catalyst. The use of doped basic alkaline earth metal oxides or hydroxides, for example hydrotalcite, has also been described. A whole series of patents describes the preparation of fatty alcohol ethoxylates having a narrow molecular weight distribution using calcined or hydrophobicized hydrotalcite as catalyst. Representative examples of the large number of these patents are: DE-A 4 242 017, DE-A 4 137 317, DE-A 4 122 200, DE-A 4 115 149, DE-A 4 034 305, WO-A 94/11 331, WO-A 92/11 224, U.S. Pat. No. 4 962 237.
According to the patents cited, the alkoxylation of low molecular weight initiator substances is carried out using a suspension procedure. Use is made of more or less coarse powders which in most cases can be removed from the product only with great technical effort.
Catalysts comprising alkaline earth metal oxide/hydroxide can readily alkoxylate low molecular weight initiator substances and also readily ethoxylate high molecular weight initiator substances, but the reaction rate in the propoxylation of initiator substances having an intermediate molecular weight is very low.
To reduce the amount of unsaturated components in the polyether alcohols and to increase the reaction rate in the molecular addition of propylene oxide, the use of multimetal cyanide compounds, in particular zinc hexacyanometalates, as catalysts has been proposed. There is a large number of publications in which such compounds have been described. Thus, DD-A-203 734 and DD-A-203 735 describe a process for preparing polyether alcohols using zinc hexacyanocobaltate.
The preparation of the zinc hexacyanometalates is also known. It is usually carried out by reacting solutions of metal salts, usually zinc chloride, with solutions of alkali metal or alkaline earth metal cyanometalates, e.g. potassium hexacyanocobaltate. A water-miscible component containing one or more heteroatoms is normally added to the resulting precipitation suspension immediately after the precipitation procedure. This heteroatom-containing component can already be present in one or both starting solutions. The water-miscible, heteroatom-containing component is preferably an ether, polyether, alcohol, ketone or a mixture of at least two of the compounds mentioned. Such processes are described, for example, in U.S. Pat. Nos. 3,278,457, 3,278,458, 3,278,459, 3,427,256.
DD-A-148 957 describes the preparation of zinc hexacyanoiridate and its use as catalyst in the preparation of polyether alcohols. Here, hexacyanoiridic acid is used instead of the corresponding salt as one of the starting materials. The multimetal cyanide compounds prepared by means of an acid usually have a higher activity than those prepared from hexacyanometalate salts.
While multimetal cyano catalysts display high activities in the propoxylation of initiator molecules having molar masses greater than 400 dalton and can propoxylate them to give high molecular weight products, the reaction of low molecular weight initiator molecules is associated with considerable difficulties.
A particular disadvantage in the industrial use of multimetal cyanide catalysts is that the alkoxylation of low molecular weight initiator molecules is very difficult. There is often a delayed commencement of the reaction resulting in addition of too much alkylene oxide at the beginning. This can, apart from reducing the space-time yield, lead to serious safety problems in the production plants.
A further problem associated with the use of multimetal cyano catalysts is that the addition of ethylene oxide onto both high molecular weight and low molecular weight initiator molecules, for example to prepare polyetherols having ethylene oxide end blocks as are used, inter alia, for producing HR polyurethane foams, is not possible and the use of multimetal cyanide catalysts is therefore restricted to particular polyetherols.
A simple combination of both catalysts in one process by first reacting the initiator substance with alkylene oxide in the presence of a basic catalyst as far as a molecular weight at which a double metal cyanide catalyst can be used and then continuing the reaction using a double metal cyanide catalyst founders because, inter alia, the basic catalyst has to be removed virtually quantitatively since it acts as a catalyst poison for the multimetal cyanide catalysts. Even the alkali metal hydroxide contents remaining in the polyether alcohol after the customary work-up are too high for this purpose. When using insoluble catalysts suspended in the polyetherol, their removal is very difficult to carry out industrially if these catalysts have not been appropriately conditioned. In addition, the purification step during the preparation of polyetherols is an additional process step which leads to product losses, to a reduction in the space-time yield and to formation of waste materials which have to be disposed of.
It is an object of the present invention to develop a process for preparing polyether polyols which leads to polyetherols having a low content of unsaturated components, in which process the molecular addition of propylene oxide proceeds at a high reaction rate from reaction commencement to high molar masses and in which the incorporation of ethylene oxide end blocks can be carried out.
We have found that this object is achieved by a process for preparing polyetherols by ring-opening polymerization of alkylene oxides onto H-functional initiator molecules, which comprises at least one process step a) in which a compound of the formula (I)
M′
a
M″
b
(OH)
c
O
d
*A
e
*L
f
(I),
where
M′ is a metal ion selected from groups IA, IIA of the Periodic Table and Ni or Zn, and mixtures thereof,
M″ is a metal ion selected from groups IIIA, IVA, IB to VIIIB of the Periodic Table and As, Sb and Bi, and mixtures thereof,
A is at least one singly charged or multiply charged, inorganic or organic anion,
L is at least one inorganic or organic ligand,
where
a is a rational number greater than zero,
b, c, d, e, f are rational numbers greater than or equal to zero,
c and d must not simultaneously be zero,
a, b, c, d, e and f are selected such
Grosch Georg Heinrich
Harre Kathrin
Junge Dieter
Larbig Harald
Lorenz Reinhard
BASF - Aktiengesellschaft
Borrego Fernando A.
Price Elvis O.
Richter Johann
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