HK1083222B - Double metal cyanide catalysts for producing polyether polyols - Google Patents

Description

Double metal cyanide catalysts for preparing polyether polyols

The present invention relates to novel Double Metal Cyanide (DMC) catalysts for preparing polyether polyols by polyaddition of alkylene oxides to starter compounds containing active hydrogen atoms.

Double Metal Cyanide (DMC) catalysts for the polyaddition of alkylene oxides to starter compounds containing active hydrogen atoms are known (see, for example, U.S. Pat. No. 3,404,109, U.S. Pat. No. 3,829,505, U.S. Pat. No. 3,941,849 and U.S. Pat. No. 5,158,922). The use of these DMC catalysts for preparing polyether polyols in particular reduces the content of monofunctional polyethers having terminal double bonds, the so-called "monools", in comparison with conventional processes for preparing polyether polyols with alkali metal catalysts, such as alkali metal hydroxides. The polyether polyol thus obtained can be processed into high-quality polyurethanes (e.g., elastomers, foams and coatings). DMC catalysts are usually obtained by reacting an aqueous solution of a metal salt with an aqueous solution of a metal cyanide salt in the presence of an organic complex ligand, such as an ether. In a typical catalyst preparation, for example, an aqueous solution of (excess) zinc chloride is mixed with an aqueous solution of potassium hexacyanocobaltate, and dimethoxyethane (glyme) is then added to the resulting suspension. After filtration and washing of the catalyst with an aqueous glyme solution, the catalyst having the general formula

Zn₃[Co(CN)₆]₂·x ZnCl₂·y H₂O.z glyme

With a catalyst (see, for example, EP-A700949).

The following references disclose DMC catalysts: JP-A4145123, U.S. Pat. No. 5,470,813, EP-A700949, EP-A743093, EP-A761708 and WO 97/40086, which catalysts further reduce the content of monofunctional polyethers having terminal double bonds in the preparation of polyether polyols by using tert-butanol as organic ligand, by itself or in combination with polyethers (EP-A700949, EP-A761708, WO 97/40086). Furthermore, the use of these DMC catalysts shortens the induction time in the polyaddition reaction of alkylene oxides with the corresponding starter compounds and increases the catalyst activity.

It has now been found that DMC catalysts which comprise a crown ligand as ligand have a very high activity in the preparation of polyether polyols.

The subject of the invention is therefore a Double Metal Cyanide (DMC) catalyst comprising:

a) at least one double metal cyanide compound,

b) at least one organic ligand, which is not a crown ligand; and

c) at least one crown ligand.

The catalysts of the invention may optionally comprise d) water, preferably in an amount of from 1 to 10% by weight and/or e) one or more compounds of the formula (I) M (X) resulting from the preparation of the double metal cyanide a)_nPreferably in an amount of 5 to 25% by weight. In (I), M is selected from the following metals: zn (II), Fe (II), Ni (II), Mn (II), Co (II), Sn (II), Pb (II), Fe (III), Mo (IV), Mo (VI), Al (III), V (V), V (IV), Sr (II), W (IV), W (VI), Cu (II) and Cr (III). Zn (II), Fe (II), Co (II) and Ni (II) are particularly preferred. The anions X are identical or different, preferably identical, and are preferably selected from the group consisting of halide, hydroxide, sulfate, carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate, oxalate or nitrate. n has a value of 1, 2 or 3.

The double metal cyanide compounds a) contained in the catalysts of the invention are reaction products of water-soluble metal salts and water-soluble metal cyanide salts.

Water-soluble metal salts suitable for preparing the double metal cyanide compounds a) are preferably those of the formula (I) M (X)_nWherein M is selected from the group consisting of the metals Zn (II), Fe (II), Ni (II), Mn (II), Co (II), Sn (II), Pb (II), Fe (III), Mo (IV), Mo (VI), Al (III), V (V), V (IV), Sr (II), W (IV), W (VI), Cu (II) and Cr (III). Zn (II), Fe (II), Co (II) and Ni (II) are particularly preferred. The anions X are identical or different, preferably identical, and are preferably selected from the group consisting of halide, hydroxide, sulfate, carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate, oxalate or nitrate. n has a value of 1, 2 or 3.

Examples of suitable water-soluble metal salts are zinc chloride, zinc bromide, zinc acetate, zinc acetylacetonate, zinc benzoate, zinc nitrate, iron (II) sulfate, iron (II) bromide, iron (II) chloride, cobalt (II) thiocyanate, nickel (II) chloride, nickel (II) nitrate. Mixtures of different water-soluble metal salts may also be used.

Water-soluble metal cyanide salts suitable for preparing the double metal cyanide compounds a) are preferably prepared from the formula (II) (Y)_aM′(CN)_b(A)_cWherein M' is selected from the metals Fe (II), Fe (III), Co (II), Co (III), Cr (II), Cr (III), Mn (II), Mn (III), Ir (III), Ni (II), Rh (III), Ru (II), V (IV) and V (V). Particularly preferably M' is selected from the metals Co (II), Co (III), Fe (II), Fe (III), Cr (III), Ir (III) and Ni (II). The water-soluble metal cyanide salt may contain one or more of these metals. The cations Y are identical or different, preferably identical, and are selected from alkali metal ions and alkaline earth metal ions. The anions A are identical or different, preferably identical, and are selected from the group consisting of halide, hydroxide, sulfate, carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate, oxalate or nitrate. Not only a but also b and c are integers, wherein the values of a, b and c are selected to obtain electroneutrality of the metal cyanide salt; a is preferably 1, 2, 3 or 4; b is preferably 4, 5 or 6; c is preferably 0. Examples of suitable water-soluble metal cyanide salts are potassium hexacyanocobaltate (III), potassium hexacyanoferrate (II), potassium hexacyanoferrate (III), calcium hexacyanoferrate (III) and lithium hexacyanoferrate (III).

Preferred double metal cyanide compounds a) comprised in the catalyst of the present invention are compounds represented by the general formula (III):

M_x[M′_x′(CN)_y]_zwherein

M is as defined for formula (I);

m' is as defined for formula (II);

x, x', y and z are integers and are selected such that the double metal cyanide is electrically neutral.

It is preferable that:

x is 3, x' is 1, y is 6 and z is 2,

m ═ zn (ii), fe (ii), co (ii), or ni (ii); and is

M ═ co (iii), fe (iii), cr (iii), or ir (iii).

Examples of suitable double metal cyanides a) are zinc hexacyanocobaltate (III), zinc hexacyanocollitate (III), zinc hexacyanocobaltate (III) and cobalt hexacyanocobaltate (II). Examples of other suitable double metal cyanides can be found in, for example, US-a5,158,922. Zinc hexacyanocobaltate (III) is particularly preferably used.

The organic ligands b) contained in the DMC catalysts of the present invention are known in principle and are described in detail in the prior art (for example U.S. Pat. No. 5,158,922, U.S. Pat. No. 3,404,109, U.S. Pat. No. 3,829,505, U.S. Pat. No. 3,941,849, EP-A700949, EP-A761708, JP-A4145123, U.S. Pat. No. 5,470,813, EP-A743093 and WO 97/40086). Preferred organic ligands are water-soluble organic compounds which carry heteroatoms, such as oxygen, nitrogen, phosphorus or sulfur, and which can form complexes with the double metal cyanide compounds a). Suitable organic ligands are, for example, alcohols, aldehydes, ketones, ethers, esters, amides, ureas, nitriles, sulfides and mixtures thereof. Preferred organic ligands are water-soluble aliphatic alcohols, such as ethanol, isopropanol, n-butanol, isobutanol, sec-butanol and tert-butanol. Tert-butanol is particularly preferred.

Suitable crown ligands c) are monocyclic crown compounds such as crown ethers, crown ethers substituted by heteroatoms (e.g. aza-, thia-or phospha-crown ligands), globular ligands (spherenden), cyclic compounds composed of heteroaromatic building blocks such as furan, thiophene or pyridine (e.g. hexapyridine) or cyclic compounds which contain a keto group, a carboxylate group or an acid amide group as donor site in the ring (e.g. nonactin or valinomycin). Preferably, crown ethers are used as crown ligands c). Particular preference is given to those whose ring system comprises from 3 to 20 oxygen atoms, where two adjacent oxygen atoms are in each case connected by a bridge having a length of from 2 to 6 carbon atoms. On the central ring system of the crown ether, an aliphatic or aromatic ring may be fused; the crown ethers may additionally have functional groups such as amino, hydroxyl, carbonyl or nitro groups.

Examples of unsubstituted crown ethers are [12] crown-4 (1, 4, 7, 10-tetraoxacyclododecane), [15] crown-5 (1, 4, 7, 10, 13-pentaoxacyclopentadecane), [18] crown-6 (1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane), [21] crown-7 (1, 4, 7, 10, 13, 16, 19-heptaoxaheneicosane) or [24] crown-8 (1, 4, 7, 10, 13, 16, 19, 22-octaoxacyclotetracosane). Examples of crown ethers having fused ring systems are benzo [15] crown-5, dibenzo [18] crown-6, dicyclohexyl [18] crown-6 or dibenzo [30] crown-10. Examples of crown ethers having additional functional groups are 2-hydroxymethyl [12] crown-4, 2-hydroxymethyl [18] crown-6, [18] crown-6-2, 3, 11, 12-tetracarboxylic acid, 4-aminodibenzo [18] crown-6, 2-aminomethyl [15] crown-5, 4-formylbenzo [15] crown-5, 4-nitrobenz [18] crown-6 or perfluoro [15] crown-5. Other examples are given in J.chem.Soc.89(1967) 7017, Angew.chem, 84 (1972) 16 or G.W.Gokel, S.J.Korzeniowski (Hrsg), "Macrocyclic polyester Synthesis", Springer, Berlin, Heidelberg, New York 1982.

The DMC catalysts of the present invention comprise from 20 to 90% by weight, preferably from 25 to 80% by weight, of double metal cyanide compounds a) and from 0.5 to 30% by weight, preferably from 1 to 25% by weight, of organic ligands b), based in each case on the amount of catalyst prepared. The DMC catalysts of the present invention generally comprise from 1 to 80% by weight, preferably from 1 to 40% by weight, of the at least one crown ligand c), based on the amount of catalyst prepared.

The catalyst composition is usually analyzed by means of elemental analysis, thermogravimetric analysis or extraction to remove ionic surface or interfacial active compounds and subsequent gravimetric determination.

The catalysts of the present invention may be crystalline, partially crystalline or amorphous. Crystallinity is typically analyzed by powder X-ray diffraction.

The catalyst of the present invention preferably comprises:

a) zinc hexacyanocobaltate (III),

b) tert-butanol, and

c) a coronal ligand.

The preparation of the DMC catalysts of the present invention is generally carried out in aqueous solution by reaction of α) metal salts, in particular metal salts represented by the formula (I), with metal cyanide salts, in particular metal cyanide salts represented by the formula (II), β) organic ligands b) which are not crown ligands, and γ) at least one crown ligand c).

In this case, a metal salt, for example zinc chloride, used in stoichiometric excess (at least 50 mol% based on the moles of metal cyanide salt), is first reacted with an aqueous solution of a metal cyanide salt, for example potassium hexacyanocobaltate, in the presence of an organic ligand b), for example tert-butanol, wherein a suspension is formed which contains a double metal cyanide a), for example zinc hexacyanocobaltate, water d, an excess of metal salt e) and the organic ligand b).

In this case, the organic ligands b) may be present in the aqueous solution of the metal salt and/or metal cyanide salt or added directly to the suspension obtained after precipitation of the double metal cyanide a). An excess of organic ligand is typically used. It has proven advantageous to mix the aqueous solution and the organic ligand b) under vigorous stirring. The resulting suspension is then generally treated with component c). Component c) is preferably used in admixture with water and the organic ligand b).

The catalyst is then separated from the suspension by known techniques, such as centrifugation or filtration. In a preferred embodiment of the invention, the separated catalyst is subsequently washed with an aqueous solution of the organic ligand b) (for example by resuspension and subsequent re-separation by filtration or centrifugation). In this way, for example, water-soluble by-products, such as potassium chloride, can be removed from the catalyst of the invention.

The amount of organic ligands b) in the washing solution is preferably from 20 to 80% by weight, based on the total amount of the solution. Furthermore, it is advantageous to add a small amount of the crown ligand c) used as component γ) to the aqueous washing solution, preferably from 0.5 to 5% by weight, based on the total amount of the solution.

Furthermore, it is advantageous to wash the DMC catalyst more than once. For this purpose, the first washing step described above can be repeated, for example. However, preference is given to using nonaqueous solutions, for example mixtures of organic ligands and the crown ligands c) used as component γ) in the further washing process.

The washed catalyst is then dried, optionally after comminution, at temperatures of generally from 20 to 100 ℃ and pressures of generally from 0.1 mbar to atmospheric pressure (1013 mbar).

A further subject of the invention is the use of the DMC catalysts of the invention in a process for preparing polyether polyols by polyaddition of alkylene oxides to starter compounds containing active hydrogen atoms.

Preferred alkylene oxides are ethylene oxide, propylene oxide, butylene oxide and mixtures thereof. The polyether chains can be formed by alkoxylation, for example, using only one monomeric epoxide or using 2 or 3 different monomeric epoxides in a random or block manner. A detailed description of this point can be found inUllmanns Encyclopdie der industriellen ChemieA21 volume, 1992, page 670 and pages that follow.

Preferred starting compounds containing active hydrogen atoms are compounds having a (number average) molecular weight of from 18 to 2000 and from 1 to 8 hydroxyl groups. Examples of such starter compounds are ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propanediol, 1, 4-butanediol, 1, 6-hexanediol, bisphenol A, trimethylolpropane, glycerol, pentaerythritol, sorbitol, sucrose, degraded starch or water.

Preference is given to using, for example, starting compounds containing active hydrogen atoms which are prepared from the abovementioned low-molecular-weight starting compounds by conventional alkali metal catalysis, and starting compounds which constitute oligomeric alkoxylation products having a (number average) molecular weight of 200-2000.

The polyaddition of the alkylene oxides catalyzed by the catalysts of the present invention on the starting compounds containing active hydrogen atoms is generally carried out at temperatures in the range from 20 to 200 deg.C, preferably from 40 to 180 deg.C, more preferably from 50 to 150 deg.C. The reaction can be carried out at a total pressure of from 0.0001 to 20 bar. The polyaddition can be carried out in bulk or in an inert organic solution, such as toluene and/or THF. The amount of solvent is usually from 10 to 30% by weight, based on the amount of polyether polyol to be prepared.

The concentration of the catalyst is chosen such that the polyaddition reaction is adequately controlled under the given reaction conditions. The catalyst concentration is usually from 0.0005% to 1% by weight, preferably from 0.001% to 0.1% by weight, more preferably from 0.001 to 0.0025% by weight, based on the amount of polyether polyol to be produced.

The (number average) molecular weight of the polyether polyol prepared by the process of the present invention is in the range of 500-100000g/mol, preferably 1000-50000g/mol, more preferably 2000-20000 g/mol.

The polyaddition can be carried out continuously or discontinuously (e.g., in a batch or semi-batch process).

Due to its significantly increased activity, the catalyst of the present invention can be used in very low concentrations (25ppm and less, based on the amount of polyether polyol to be prepared). In the production of polyurethanes, if polyether polyols prepared in the presence of the catalysts of the present invention are used (Kunststoffhandbuch, volume 7, polyurethane, third edition, 1993, pages 25 to 32 and 57 to 67), the step of removing the catalyst from the polyether polyol can be omitted without adversely affecting the product quality of the polyurethane obtained.

EXAMPLE 1 DMC catalyst containing cis-bicyclohexano [18] crown-6

9 ml of a 7.4% by weight aqueous solution of potassium hexacyanocobaltate were added to a mixture of 15 ml of an 11.8% by weight aqueous zinc chloride solution, 13 ml of tert-butanol and 0.4 g of cis-dicyclohexyl [18] crown-6 with vigorous stirring. The precipitate formed is washed with a mixture of 10 ml of tert-butanol and 30 ml of water and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 50 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

12.9% by weight of cobalt, 25.7% by weight of zinc, 6.0% by weight of tert-butanol and 14.6% by weight of cis-bicyclohexano [18] crown-6.

EXAMPLE 2 DMC catalyst containing cis-bicyclohexano [18] crown-6

9 ml of a 7.4% by weight aqueous solution of potassium hexacyanocobaltate are added to a mixture of 15 ml of an 11.8% by weight aqueous zinc chloride solution, 13 ml of tert-butanol, 1 ml of 12% by weight acetic acid and 0.4 g of cis-dicyclohexyl [18] crown-6 with vigorous stirring. The precipitate formed is washed with a mixture of 10 ml of tert-butanol and 30 ml of water and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 50 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

cobalt 10.4 wt%, zinc 25.3 wt%, tert-butanol 4.8 wt%, cis-bicyclohexano [18] crown-6 24.2 wt%.

EXAMPLE 3 DMC catalyst containing cis-bicyclohexano [18] crown-6

26.1 ml of a 1.84% aqueous solution of hexacyanocobaltic acid was added to a mixture of 15 ml of an 11.8% by weight aqueous zinc chloride solution, 13 ml of t-butanol, 1 ml of 12% by weight acetic acid and 0.4 g of cis-dicyclohexyl [18] crown-6 with vigorous stirring. The precipitate formed is washed with a mixture of 10 ml of tert-butanol and 30 ml of water and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 50 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

cobalt 10.5 wt%, zinc 19.7 wt%, tert-butanol 4.9 wt%, cis-bicyclohexano [18] crown-6 15.2 wt%.

EXAMPLE 4 DMC catalyst containing cis-bicyclohexano [24] crown-8

6 ml of a 7.4% by weight aqueous solution of potassium hexacyanoferrate and 5 ml of a 4.8% by weight aqueous solution of potassium hexacyanoferrate (III) are added to a mixture of 15 ml of an 11.8% by weight aqueous zinc chloride solution, 13 ml of tert-butanol and 0.4 g of cis-dicyclohexyl [24] crown-8 with vigorous stirring. The precipitate formed is washed with a mixture of 10 ml of tert-butanol and 30 ml of water and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 50 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

7.3% by weight of cobalt, 3.7% by weight of iron, 25.5% by weight of zinc, 5.2% by weight of tert-butanol and 21.7% by weight of cis-bicyclohexano [24] crown-8.

EXAMPLE 5 DMC catalyst containing cis-bicyclohexano [18] crown-6

4.5 ml of a 7.4% by weight aqueous solution of potassium hexacyanoferrate and 5 ml of a 7.2% by weight aqueous solution of potassium hexacyanoferrate (III) are added to a mixture of 15 ml of an 11.8% by weight aqueous zinc chloride solution, 13 ml of tert-butanol and 0.4 g of cis-dicyclohexyl [18] crown-6 with vigorous stirring. The precipitate formed was washed with 30 ml of water and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 50 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

6.2% by weight of cobalt, 5.9% by weight of iron, 25.9% by weight of zinc, 5.9% by weight of tert-butanol and 16.7% by weight of cis-bicyclohexano [18] crown-6.

EXAMPLE 6 DMC catalyst containing [18] crown-6

9 ml of a 7.4% by weight aqueous solution of potassium hexacyanocobaltate are added to a mixture of 28 ml of a 12.7% by weight aqueous zinc chloride solution, 13 ml of tert-butanol, 1 ml of 12% by weight acetic acid and 0.4 g of [18] crown-6 with vigorous stirring. The precipitate formed was washed with 30 ml of water and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 100 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

cobalt 11.0 wt%, zinc 26.2 wt%, tert-butanol 6.2 wt%, and [18] crown-6 15.1 wt%.

Example 7 DMC catalyst containing [15] crown-5:

27 ml of a 1.79% by weight aqueous solution of hexacyanocobaltic acid are added to a mixture of 28 ml of a 12.7% by weight aqueous solution of zinc chloride, 13 ml of tert-butanol, 1 ml of 12% by weight acetic acid and 0.4 g of [15] crown-5 with vigorous stirring. The precipitate formed was washed with 30 ml of water and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 100 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

cobalt 10.7 wt%, zinc 23.3 wt%, tert-butanol 5.0 wt%, and [15] crown-5 wt% 11.4 wt%.

EXAMPLE 8 DMC catalyst containing 2-hydroxymethyl [18] crown-6

9 ml of a 7.4% by weight aqueous solution of potassium hexacyanocobaltate are added to a mixture of 14 ml of a 12.7% by weight aqueous zinc chloride solution, 13 ml of tert-butanol and 0.4 g of 2-hydroxymethyl [18] crown-6 with vigorous stirring. The precipitate formed was washed with 30 ml of water and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 100 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

10.4% by weight of cobalt, 24.7% by weight of zinc, 5.8% by weight of tert-butanol and 12.4% by weight of 2-hydroxymethyl [18] crown-6.

EXAMPLE 9 DMC catalyst containing 2-hydroxymethyl [18] crown-6

27 ml of a 1.79% by weight aqueous solution of hexacyanocobaltic acid are added to a mixture of 14 ml of a 12.7% by weight aqueous solution of zinc chloride, 13 ml of tert-butanol, 1 ml of 12% by weight acetic acid and 0.4 g of 2-hydroxymethyl [18] crown-6 with vigorous stirring. The precipitate formed was washed with 30 ml of water and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 100 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

10.1% by weight of cobalt, 20.2% by weight of zinc, 4.2% by weight of tert-butanol and 13.4% by weight of 2-hydroxymethyl [18] crown-6.

Comparative example 10 DMC catalyst without crown ligand

9 ml of a 7.4% by weight aqueous solution of potassium hexacyanocobaltate are added to a mixture of 15 ml of an 11.8% by weight aqueous zinc chloride solution and 13 ml of tert-butanol with vigorous stirring. The precipitate formed is washed with 10 ml of tert-butanol and filtered. Subsequently, 20 ml of tert-butanol were added to the residue and filtered again. After filtration, the catalyst was dried to constant weight at 50 ℃ under reduced pressure (10 mbar).

Elemental analysis, thermogravimetric analysis and extraction:

15.7% by weight of cobalt, 27.8% by weight of zinc and 7.9% by weight of tert-butanol.

Preparation of polyether polyols

General procedure

50g of polypropylene glycol starting material (molecular weight 1000g/mol) and 20mg of catalyst were introduced under protective gas (argon) into a 500ml pressure reactor and heated to 130 ℃ with stirring to determine the catalyst activity.

At a pressure of 2.5 bar, up to 50g of propylene oxide were metered in over 30 minutes. After 30 minutes the reaction mixture was cooled to room temperature and the propylene oxide was removed by argon purging.

The product was evaluated by molecular weight distribution (weight average) by GPC.

The following table gives the results obtained:

catalyst of the examples No	Mw[g/mol]
		1	2130
2	1970
		3	1940
4	2180
		5	2020
6	1920
		7	1890
8	1910
		9	1900
10 (comparison)	1310

Claims (7)

1. A double metal cyanide catalyst comprising:

a) at least one double metal cyanide compound,

b) at least one organic ligand which is not a crown ligand, and

c) at least one crown ether.

2. The double metal cyanide catalyst of claim 1 further comprising d) water and/or e) a water soluble metal salt.

3. The double metal cyanide catalyst of claim 1 or 2, wherein the double metal cyanide a) is zinc hexacyanocobaltate (III).

4. The double metal cyanide catalyst of claim 1 or 2, wherein the organic ligand b) is tert-butanol.

5. The double metal cyanide catalyst of claim 1 or 2, wherein the catalyst comprises 1 to 80 wt.% of at least one crown ether.

6. A method for preparing a double metal cyanide catalyst comprising the steps of:

i) in aqueous solution, the following compounds are reacted:

alpha) metal salts and metal cyanide salts

Beta) an organic ligand which is not a crown ligand, and

gamma) a crown ether, a cyclic ether,

ii) separating, washing and drying the catalyst obtained in step i).

7. A process for producing polyether polyols by polyaddition of alkylene oxides to starter compounds containing active hydrogen atoms, wherein the polyaddition of the alkylene oxides is carried out in the presence of one or more double metal cyanide catalysts as claimed in one of claims 1 to 5.