Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-07-26
2002-08-27
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C528S066000, C568S624000
Reexamination Certificate
active
06441247
ABSTRACT:
The invention relates to a process for the preparation of polyoxyalkylene glycols by catalytic reaction of H-functional initiators with lower alkylene oxides.
Polyoxyalkylene glycols are used in large amounts for the preparation of polyurethanes. They are usually prepared by catalytic addition of lower alkylene oxides, in particular ethylene oxide and propylene oxide, to H-functional polymerization initiators. The catalysts used are mostly alkali metal hydroxides or salts, of which potassium hydroxide is of greatest industrial significance.
In the synthesis of polyoxyalkylene glycols having long chains and hydroxyl values of from ca 26 to ca 60 mg of KOH/g, such as are used, in particular, for the preparation of flexible polyurethane foams, chain growth is accompanied by side reactions which cause irregularities in the chain structure. These by-products are referred to as unsaturated components and lead to impairment of the properties of the resulting polyurethane materials. In particular, such unsaturated components exhibiting an OH functionality of 1, give rise to the following:
by reason of their low, in some cases very low, molecular weight, they are volatile and thus increase the total content of volatile matter in the polyoxyalkylene glycol and in the polyurethanes, in particular flexible polyurethane foams, prepared therefrom;
they act as chain stoppers during production of polyurethane, because they slow down or reduce the cross-linkage of polyurethane or the build-up of molecular weight of polyurethane;
they reduce the effective OH functionality of the synthesized polyoxyalkylene glycols; thus commercial polyether polyalcohols used for flexible foams and initiated with glycerol and catalyzed with potassium hydroxide have an effective OH functionality of only approximately 2.1 to 2.6, although the glycerol used is a trifunctional polymerization initiator.
It is therefore industrially very desirable to avoid unsaturated components as far as possible. On the other hand, many, in some cases complex, polyurethane formulations are set to accommodate polyoxyalkylene glycols having OH functionalities of from 2.1 to 2.6. It is therefore desirable to prepare polyoxyalkylene glycols having OH functionalities of from 2.1 to 2.6 but having only a minimum of unsaturated components.
Hitherto there has been no lack of attempts to provide polyoxyalkylene glycols having a low content of unsaturated components. Attempts to achieve this end particularly involve changing the alkoxylation catalysts used. Thus EP-A 268,922 proposes the use of caesium hydroxide. This makes it possible to lower the concentration of unsaturated portions, but caesium hydroxide is expensive and difficult to dispose of.
Furthermore, it is known to use multimetal cyanide catalysts, mainly zinc hexacyanometallates, for the preparation of polyoxyalkylene glycols having low contents of unsaturated components. A great many documents describe the preparation of such compounds. Thus DD-A 203,735 and DD-A 203,734 describe the preparation of polyoxyalkylene glycols using zinc hexacyanocobaltate. By using multimetal cyanide catalysts it is possible to lower the content of unsaturated components in the polyoxyalkylene glycol to from ca 0.003 to 0.009 meq/g; in the case of conventional catalysis using potassium hydroxide approximately 10 times this amount (from ca 0.03 to 0.08 meq/g) is found.
In addition, the preparation of zinc hexacyanometallates is known. Usually the preparation of these catalysts is carried out by causing solutions of metal salts, such as zinc chloride, to react with solutions of alkali metal or alkaline earth metal cyanometallates, such as potassium hexacyanocobaltate. To the resulting suspension of precipitated matter there is usually added, immediately after the precipitation process, a water-miscible component containing heteroatoms. This component may be present in one or both of the educt solutions. This water-miscible component containing heteroatoms can be, for example, an ether, a polyether, an alcohol, a ketone or a mixture thereof. Such processes are described for example in U.S. Pat. No. 3,278,457, U.S. Pat. No. 3,278,458, U.S. Pat. No. 3,278,459, U.S. Pat. No. 3,427,256, U.S. Pat. No. 3,427,334, U.S. Pat. No. 3,404,109, U.S. Pat. No. 3,829,505, U.S. Pat. No. 3,941,849, EP 283,148, EP 385,619, EP 654,302, EP 659,798, EP 665,254, EP 743,093, EP 755,716, U.S. Pat. No. 4,843,054, U.S. Pat. No. 4,877,906, U.S. Pat. No. 5,158,922, U.S. Pat. No. 5,426,081, U.S. Pat. No. 5,470,813, U.S. Pat. No. 5,482,908, U.S. Pat. No. 5,498,583, U.S. Pat. No. 5,523,386, U.S. Pat. No. 5,525,565, U.S. Pat. No. 5,545,601, JP 7,308,583, JP 6,248,068, JP 4,351,632 and U.S. Pat. No. 5,545,601.
DD-A 148,957 describes the preparation of zinc hexacyanoiridate and the use thereof as catalyst for polyether polyalcohol synthesis. Hexacyanoiridic acid is used as starting material. This acid is isolated as a solid and used in this form.
EP-A 862,947 describes the preparation of other double-metal cyanide complexes, in particular the use of cyanocobaltic acid or an aqueous solution thereof, as educt. The double-metal cyanides produced according to the teaching of EP-A 862,947 show high reactivity for ring-opening polymerization of alkylene oxides.
Multimetal cyanide catalysts show extremely high polymerization rates and make it possible to achieve high space-time polymerization yields. However, the use of multimetal cyanide catalysts involves considerable restrictions as regards the H-functional polymerization initiators that can be used. There are two types of initiators.
Some polymerization initiators are suitable for the so-called batch initiating method. These polymerization initiators, referred to below as batch starters, are placed in the reactor as the initial component of the batch and are freed from oxygen by repeated nitrogen purges and de-watered in vacuo at ≦1 mbar over a period of from 30 to 120 min at from 50° to 120° C., the de-watering time and de-watering temperature depending on the boiling point of the batch starter. The multimetal cyanide catalyst is then added and the nitrogen purge and de-watering are repeated, if necessary. Following the addition of the alkylene oxide, compounds that are suitable for use as batch starters cause, at reactor temperatures of from 90° to 140° C., commencement of the polymerization reaction, noticeable from a pressure drop in the reactor, after a time lapse of from a few minutes to, at most, 2 hours. If the reaction does not start within a period of 2 hours, the polymerization initiator is not suitable for use as a batch starter.
In practice it is found that the following polymerization initiators are especially suitable for use as batch starters: castor oil and fatty alcohols such as 1-dodecanol. However, polyetherols primed with fatty alcohols are unsuitable for the preparation of flexible PU foam. Castor oil is theoretically suitable for use as a polymerization initiator for polyetherols for the production of flexible foams, but it is not available in sufficient quantities or at consistent quality. Batch starters of particular significance are ethoxylates and propoxylates having molar masses ≦400 dalton. These polymerization initiators usually have to be prepared by alkoxylation of low-molecular initiators, such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, in particular glycerol and trimethylol propane, with alkaline catalysts such as KOH. Before these polymerization initiators can be used for polymerization using the multimetal cyanide catalysts, the alkaline catalyst must be removed quantitatively, which is economically disadvantageous.
When use is made of tripropylene glycol as the initiator it has been found that it itself and its alkoxylates having molar masses below 400 dalton are suitable for use as batch starters. However tripropylene glycol and its alkoxylates having molar masses of less than 400 dalton show less advantageous starting characteristics than eg a linear polypropylene glycol having a number-average molar mass of 4
Grosch Georg Heinrich
Harre Kathrin
Junge Dieter
Larbig Harald
Lorenz Reinhard
BASF - Aktiengesellschaft
Fernando A. Borrego
Shippen Michael L.
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