DE19957105A1 - Process for the work up of polyether alcohols, useful for the production of polyurethanes, comprises removal of the multimetal cyanide compound catalyst after the reaction by sedimentation. - Google Patents

Abstract

A process for the work up of polyether alcohols, prepared by catalytic addition of alkylene oxides with H-functional initiator substances, comprises addition of a multimetal cyanide compound as the catalyst and removal of the catalyst after the reaction from the polyether alcohol by sedimentation.

Description

The invention relates to a method for working up Polyether alcohols caused by the addition of alkylene oxides on H-functional starter substances using multimetal cyanide catalysts were produced.

Polyurethanes are manufactured in large quantities. An essential Lich starting product for their production are polyethers alcohols. They are usually produced by catalytic ones Addition of lower alkylene oxides, especially ethylene oxide and propylene oxide, on H-functional starters. As catalysts mostly basic metal hydroxides or salts are used, the potassium hydroxide being of greatest practical importance.

In the synthesis of long chain and polyether polyols Hydroxyl numbers from about 26 to about 60 mg KOH / g, as they are particularly are used for the production of flexible polyurethane foams, there are side reactions as chain growth progresses, which lead to disruptions in the chain structure. The emerging By-products are called unsaturated components and lead to an impairment of the properties of the resulting polyurethane materials. In particular, they have unsaturated components that have an OH functionality 1 have the following consequences:

They are due to their z. T. very low molecular weight volatile and thus increase the total volatile content share in the polyether polyol and in the poly made therefrom urethanes, especially flexible polyurethane foams.

They act as chains in the production of the polyurethane terminates because they crosslink the polyurethane or the Delay or increase the molecular weight of the polyurethane reduce.

It is therefore technically very desirable to use the unsaturated ones Avoid components as much as possible.

One way to make polyether alcohols with a low The content of unsaturated components is the use of Multimetal cyanide catalysts, also as DMC catalysts referred to, mostly zinc hexacyanometallates, as alkoxylation catalysts. These compounds are often referred to as DMC  Described catalysts. There is a large number of documents in which the production of polyether alcohols by means of like catalysts is described. So in DD-A-203 735 and DD-A-203 734 the production of polyether polyols under Ver using zinc hexacyanocobaltate. By using of multimetal cyanide catalysts, the content of un saturated components in the polyether polyol to about 0.003 to 0.009 meq / g can be reduced - with conventional catalysis Potassium hydroxide is found in about 10 times the amount (approx. 0.03 to 0.08 meq / g).

The production of the multimetal cyanide catalysts is also knows. These compounds are usually produced by solutions of metal salts, such as zinc chloride, with solutions of alkali or alkaline earth metal cyanometalates, such as potassium hexa cyanocobaltat, are implemented. About the resulting precipitate suspension sion usually becomes one immediately after the precipitation process water-miscible component containing heteroatoms added. This component can already be in one or both of the starting material solutions are available. These water-miscible, heteroatoms ent holding component can be, for example, an ether, polyether, Alcohol, ketone, or a mixture thereof. Such procedures 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, US 3,829,505, US 3,941,849.

After the production of the polyether alcohols, the multimetal cyanide catalyst mostly separated from the polyether alcohol. Since the multimetal cyanide catalyst is mostly very finely divided ter form is present in the polyether alcohol, the separation is very difficult.

US 5,416,241 describes a process for the production of polyether alcohols described using DMC catalysts, in which after Addition of the alkylene oxides of the catalyst Alkali compounds are made insoluble and then filtered. However, this process destroys the DMC catalyst and can therefore no longer be reused.

In the process described in US 5,248,833, the DMC Catalyst with chelating agents precipitated and then filtered. In this process, too, the catalyst deactivated and can no longer be used.

In US 4,877,906 a process for the purification of DMC catalyzed polyether alcohols by treatment with alkali metal compounds, filtering, treatment with phosphorus  connections, renewed filtering and recovery of the sun cleaned polyol described. Here, too, the DMC Catalyst cannot be reused.

According to US 4,721,818, the DMC catalyst using alkali metal hydrides poorly solubilized and separated in this form.

Another method is described in US 5,010,047. Here will the polyether alcohol after manufacture in a non-polar Solvent dissolved, the DMC catalyst fails. After that the resulting suspension using a filter aid filtered. This gives a mixture of DMC catalyst and Filter aid that is still catalytically active and again can be used for the production of polyether alcohols. The concentration of the catalyst in the filter aid is however, very low, so that a lot of filter aids the synthesis is present. Collects after repeated use more and more filter aids.

Since DMC catalysts are very expensive to manufacture, it is desirable to use this several times without it becoming one Decrease in their catalytic activity comes without that other substances that affect the activity of the catalysts pregnant or handling the catalysts or the Reaction mixture z. B. difficult by changing viscosity can be recycled together with the DMC catalysts.

Surprisingly, it has now been found that it is possible to use the DMC catalyst after the reaction by sedimentation from the Remove polyether alcohol and then reuse it.

The invention accordingly relates to a method for working of polyether alcohols using DMC catalysts were produced, characterized in that after the order settlement of the catalyst by sedimentation of the polyether alcohol is separated without it after the completion of the Addition of the alkylene oxides is chemically changed.

The preferred embodiment of sedimentation is Centrifuge. Surprisingly, it is possible through that Centrifuge the content of DMC catalysts to values below Bring 2 ppm. The catalytic activity of Completely preserved DMC catalysts.

The sedimentation according to the invention is preferably carried out at Temperatures in the range between 10 to 200 ° C.  

According to the invention, Ver drive such DMC catalysts that use a hexacyanometalate acid. Such DMC Most catalysts are crystalline and monoclinic Crystal system. Such catalysts have been described for example in EP-A-862 947 and WO 99/16775.

The process is particularly advantageous for such polyethers alcohols can be used, in whose molecular weight distribution one off embossed high molecular flank with molecular weights above 80,000 daltons is present. Surprisingly, this becomes very high molecular weight portion of the polyether alcohol together with the DMC Catalyst separated from the polyether alcohol. A partition this very high molecular weight portion of the polyether alcohol from DMC catalyst before reuse is not required Lich, since this does not affect the catalytic activity and moreover the mixture of DMC catalyst and very high molecular weight polyether alcohol much easier to handle is as the pure, powdery catalyst. Besides, it is from Advantage if the very high molecular weight part from the polyether alcohol is removed, as this is in the production of Polyurethanes, especially polyurethane foams, are very disadvantageous can impact.

Surprisingly, you can use this mixture of DMC catalyst and very high molecular weight polyether alcohol also for production of polyether alcohols whose molecular weight distribution is none has a very high molecular flank. It shows that this mixture of DMC catalyst and very high mole Kular polyether alcohol remains stable and after the implementation again separated from the polyether alcohol in this form can be. There is no contamination of the polyether alcohol with the high molecular weight polyether alcohols with the DMC catalyst have entered the reaction mixture. Under "very high molecular weight "is a molecular weight of over 90,000 Da, especially in the range between 80,000 and 1,000,000 Da preferably between 80,000 and 300,000 understood.

When using the separated DMC catalysts that together with the very high molecular weight portion of the polyether alcohol were separated, for the reassembly of alkylene oxide shows up surprisingly, that the formation of the high molecular flank was suppressed.

Of course, according to the inventive method also such polyether alcohols are purified, their molecular weight distribution has no high molecular flank. In  In this case, however, it is necessary during sedimentation to spend more energy. So when using Centrifuges for performing the method according to the invention Centrifuge speed can be increased. The optimal conditions for sedimentation are for the skilled person by comparison try to determine easily.

The DMC catalyst can be removed from the polyether alcohol be freed of adhering polyetherol. That can be done by Wash, for example with water or organic solutions average, done. After that, it can be converted into a form in which he again as a catalyst for the production of polyether alcohols can be used. This can be done, for example Emulsification in solvents. Working up the Catalyst is carried out in particular when the Catalyst after separation to make another Polyether alcohol should be used to remove impurities to avoid in the product.

However, it is also possible to use it directly without further refurbishment use again for the production of polyether alcohols. This Process variant is used in particular if the Catalyst after workup to produce the same Polyether alcohol is to be used. As stated above this process variant can also be carried out if the polyether alcohol from which the DMC catalyst is made from a poly ether alcohol, whose molecular weight distribution is a high molecular weight Has flank, was separated.

In the technically usual batch production of polyether alcohol is first after the dosing of the alkylene oxides a so-called post-reaction phase connected, in which the alkylene oxide still present in the reaction mixture completely should react. This is usually followed by distillation, in the case of unreacted monomers and other volatile Components are to be removed from the reaction mixture. The catalyst according to the invention can then be removed connect. The separated catalyst can then, as be wrote, with or without reappraisal for the next approach be used.

Before or after the removal of the catalyst according to the invention a filtration of the polyether alcohol to remove coarse mechanical impurities or even larger ones Agglomerates of the DMC catalyst used carried out become.  

In the continuous production of polyether alcohols the end product is separated off continuously or in batches wise. The stripped polyether alcohol is worked up then mostly as described above. The separated catalyst can then one of the continuously to the reaction mixture dosed starting products, preferably the starting substance be set. This procedure can usually be based on a Workup of the separated catalyst can be dispensed with.

Through the work-up method according to the invention, it is over surprisingly possible, the DMC catalyst by a simple Process that can easily be used in existing manufacturing plants of polyether alcohols can be integrated, almost completely, that is, except for residual zinc and cobalt contents below 10 ppm, remove it from the polyether alcohol and then remove it practically without losses again for the production of polyether use alcohols. This allows the production of polyethers alcohols with DMC catalysts he much cheaper follow, since much less catalyst is provided got to.

The invention is illustrated by the examples below become.

Examples example 1

2000 ml of strongly acidic ion exchanger (K2431, Bayer) were regenerated with 700 g sulfuric acid 36% by weight and with water washed until the process was neutral. Then you gave one Solution of 240 g of potassium hexacyanocobaltate in 700 g of water on the Exchange column. The column was then eluted until the Outlet was neutral again. The 3085 g of eluate obtained were Tempered to 40 ° C and added another 4000 g of water. In this 750 g of Technocell® 150 cellulose were then suspended. A solution of 267.3 g of Zn (II) acetate was then Add dihydrate in 600 g of water. Then immediately gave 684 g tert-butanol and stirred at 40 ° C for a further 30 min. After that the solid was suctioned off and on the filter with tert.- Washed butanol. The solid thus obtained was at 30 ° C for 16 h dried in a vacuum drying cabinet.  

Example 2

7 l strongly acidic ion exchanger, which is in the sodium form (Amberlite® 252 Na, from Rohm & Haas) were converted into one Exchange column (length 1 m, volume 7.7 l) filled. The ion exchanger was then converted to the H form by 10% hydrochloric acid at a rate of 2 bed volumes was driven over the exchange column for 9 hours until the Na content in the discharge was less than 1 ppm. Then was the ion exchanger is washed neutral with water.

The regenerated ion exchanger was now used to create a to produce essentially alkali-free hexacyanocobaltic acid. A 0.24 molar solution of potassium hexacyanocobaltate in Water at the rate of one bed volume per hour passed over the exchanger. After 2.5 bed volume was from the potassium hexacyanocobaltate solution was changed to water. The 2.5 bed volumes obtained had an average content of Hexacyanocobaltic acid of 4.5 wt .-% and alkali contents smaller 1 ppm.

The hexacyanocobaltate used for the further examples Acid solutions were diluted with water accordingly.

2433 g of an aqueous hexacyanocobaltoic acid solution (cobalt content 6 g / l, potassium content <1 ppm) were heated to 40 ° C. and with stirring (paddle stirrer, U = 500 min ^-1 ) 120 ml Pluronic PE 6100 (BASF Aktiengesellschaft, coblock polymer from PO and EO) added and dissolved. A solution of 108.8 g of Zn (II) acetate dihydrate in 400 g of water was then added with stirring (blade stirrer, U = 500 min ^-1 ). 400 g of tert-butanol are then added to the suspension. The suspension was stirred at 40 ° C for a further 30 min. The solid was then filtered off and washed on the filter with tert-butanol.

The moist filter cake became a suspension with water processed, which has a multimetal cyanide content of 5% by weight pointed.

Example 3

The synthesis was carried out in a cleaned and dried 1 l Stirred autoclaves performed. There were 400 g of polypropylene glycol the molar mass 400 g / mol in the stirred kettle and 8.4 g of the catalyst according to Example 2 intimately mixed. The cauldron  Contents were made inert with nitrogen and 1 h at 140 ° C in Vacuum treated.

1 mol of ethylene oxide was then metered in at 140 ° C. and the reaction started. The remaining ethylene oxide was then metered in up to a total amount of 440 g. The dosing time was 35 minutes, the maximum pressure was 4.4 bar absolute. The product was worked up by vacuum distillation at 0.1 bar, 110 ° C. The polyol was filtered at 70 ° C at a pressure of 3 bar. The remaining catalyst was depleted by centrifugation in a laboratory centrifuge Universal 30 RF Fa. Hettich at 8000 rpm ^-1 and the polyol by decantation from the catalyst-containing sediment separated.

The resulting polyether alcohol had the following characteristics:
Hydroxyl number: 128 mg KOH / g
Viscosity at 25 ° C: 182 mPas (determined with a capillary viscometer according to Ubbelohde, test standard BASF Schwarzheide PPU 00 / 03-01)
Zn / Co content before centrifugation 117/50 ppm;
Zn / Co content after centrifugation 5/3 ppm.

Example 4

The synthesis was in a cleaned and dried 1 liter stirred autoclave performed. There were 400 g of polypropylene Glycol of molecular weight 400 g / mol in the stirred tank and with the catalyst of Example 1 intimately mixed. The cauldron Contents were made inert with nitrogen and 1 h at 105 ° C in Vacuum treated.

1 mol of ethylene oxide was then metered in at 105 ° C. and that Waiting for the reaction to start. Then the rest Liche ethylene oxide dosed up to a total amount of 440 g. The dosing time was 1.1 hours, the maximum pressure was 4.1 bar absolutely. The product was worked up by vacuum distillation. The catalyst was removed by centrifugation enriched and the polyol separated from the sediment by decanting. The catalyst residue (the sediment) did not continue treated.

The resulting polyether alcohol had the following characteristics:
Hydroxyl number: 127 mg KOH / g
Viscosity at 25 ° C: 146 mPas; (determined with a capillary viscometer according to Ubbelohde, test standard BASF Schwarzheide PPU 00 / 03-01)
Zn / Co content in the polyol after filtration: 112 / 46.6 ppm
Zn / Co content in the polyol after centrifugation: <1/1 ppm.

Example 5

The synthesis was carried out in a cleaned and dried 1 l Stirred autoclaves performed. There were 200 g of polypropylene glycol the molar mass 400 g / mol in the stirred tank and with the Catalyst residue from Example 4 intimately mixed. The cauldron Contents were made inert with nitrogen and 1 h at 135 ° C in Vacuum treated.

1 mol of propylene oxide was then metered in at 130 ° C. and that Waiting for the reaction to start. Then the rest Liche propylene oxide dosed up to a total amount of 800 g. The dosing time was 1.8 hours, the maximum pressure was 4.2 bar absolute. The product was worked up by Vacuum distillation and centrifugation.

The resulting polyether alcohol had the following characteristics:
Hydroxyl number: 53 mg KOH / g
Viscosity at 25 ° C: 655 mPa (determined with a capillary viscometer according to Ubbelohde, test standard BASF Schwarzheide PPU 00 / 03-01)
Zn / Co content: 9.5 / 5 ppm.

Claims (6)

1. Process for working up polyether alcohols, producible by catalytic addition of alkylene oxides to H-functional starter substances, characterized in that at least one multimetal cyanide compound is used as the catalyst and the catalyst is removed from the polyether alcohol by sedimentation after the addition of the alkylene oxides. 2. The method according to claim 1, characterized in that the Chemical catalyst after the addition of the alkylene oxides is not changed. 3. The method according to claim 1, characterized in that the sedimentation is a centrifugation. 4. The method according to claim 1, characterized in that the separated catalyst again as a catalyst for the addition of alkylene oxides to the H-functional start substances can be used. 5. The method according to claim 1, characterized in that the Catalyst is crystalline and a monoclinic crystal system owns. 6. The method according to claim 1, characterized in that the Catalyst by reacting a metal salt with a Hexcyanometallic acid prepared in the presence of a surfactant has been.