HK1032924B - Double metal cyanide catalysts containing polyester for preparing polyether polyoles - Google Patents

Description

Double metal cyanide catalysts containing polyester for preparing polyether polyols

Technical Field

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

Background

Double metal cyanide (CMC) catalysts for polyaddition of alkylene oxides to starter compounds containing active hydrogen atoms are known (see, for example, US 3404109, US 3829505, US 3941849 and US 5158922). The use of these double metal cyanide catalysts for preparing polyether polyols has the effect, in particular, of reducing the proportion of monofunctional polyethers having terminal double bonds, so-called monoools, in comparison with conventional preparation of polymeric polyols using base catalysts, such as alkali metal hydroxides. The polyether polyols thus obtained can be processed to give high-grade polyurethanes (e.g.elastomers, foams, coatings). DMC catalysts are generally obtained by reacting an aqueous solution of a metal salt with an aqueous solution of a cyanide metal salt in the presence of a low molecular weight organic complexing ligand, such as an ether. In a typical catalyst preparation process, for example, aqueous zinc chloride (in excess) is mixed with potassium hexacyanocobaltate and dimethoxyethane (glyme) is added to the resulting suspension. After filtration and washing of the catalyst with aqueous glyme solutions, an active catalyst of the general formula below is obtained (cf. EP 700949).

Zn₃[Co(CN)₆]₂·xZnCl₂·yH₂O.z glyme.

JP 4145123, US 547081, EP 700949, EP 743093 and EP 761708 disclose improved DMC catalysts which, by using tert-butanol as organic complexing ligand (by itself or in combination with polyethers (EP 700949, EP 761708)), enable a further reduction in the proportion of monofunctional polyethers having terminal double bonds in the preparation of polyether polyols. Furthermore, by using the modified DMC catalysts, the induction period of the polyaddition of alkylene oxides onto the corresponding starter compounds is shortened and the activity of the catalysts is increased.

Disclosure of Invention

The object of the present invention was to provide a further improved DMC catalyst for the polyaddition of alkylene oxides to the corresponding starter compounds, which has a considerably shorter induction period than the hitherto known catalyst classes, with a simultaneously significantly increased activity of the catalyst. The economics of the process are improved by reducing the overall reaction and cycle time to produce polyether polyols. Ideally, due to the increased activity, the catalyst can then be used at low concentrations, thus eliminating the costly step of separating the catalyst and the product can be used directly in polyurethane applications. It has surprisingly been found that DMC catalysts containing 5-80% by weight, based on the amount of catalyst produced, of polyester lead to a considerable reduction in the induction period in the production of polyether polyols, with a simultaneously significant increase in activity.

The present invention provides new and improved Double Metal Cyanide (DMC) catalysts comprising:

a) double metal cyanide compounds and

b) an organic complexing ligand, characterised in that it contains 5-80% by weight of polyester, based on the amount of catalyst produced.

The catalysts of the invention prepared from double metal cyanide compounds may also contain water, preferably from 1 to 10% by weight, and/or water-soluble salts, preferably from 5 to 25% by weight.

Double metal cyanide compounds a) suitable for the catalysts of the invention are reaction products of water-soluble metal salts and water-soluble cyanide metal salts.

Water-soluble metal salts are preferably of the formula 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). Particularly preferred are Zn (II), Fe (II), Co (II), Ni (II). X is an anion, 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 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 and nickel (II) nitrate. Mixtures of different metal salts may also be used.

The water-soluble cyanide metal salt preferably has the formula (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). M' is particularly preferably selected from the metals Co (II), CO (III), Fe (II), Fe (III), Cr (III), Ir (III) and Ni (II). The water-soluble cyanide metal salt may contain one or more of these metals. Y is an alkali metal ion or an alkaline earth metal ion. A is an anion selected from halide, hydroxide, sulfate, carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate, oxalate or nitrate. a and b are integers (. gtoreq.1), a, b and c being chosen so as to ensure electroneutrality of the cyanide metal salt; the value of c is preferably 0. Examples of suitable water-soluble cyanide metal salts are potassium hexacyanocobaltate (III), potassium hexacyanoferrate (II), potassium hexacyanoferrate (III), calcium hexacyanocobaltate (III) and lithium hexacyanocobaltate (III).

Examples of suitable double metal cyanides a) which can be used in the catalysts of the invention are zinc hexacyanocobaltate (III), zinc hexacyanoferrate (II), zinc hexacyanoferrate (III), nickel hexacyanoferrate (II) and cobalt hexacyanocobaltate (II). Examples of other suitable double metal cyanides can be found, for example, in US 5158922 (column 8, lines 29-66). Preference is given to using zinc hexacyanocobaltate (III).

The catalysts of the invention contain organic complexing ligands b) since, for example, the activity of the catalysts can be increased. Suitable organic complexing ligands are known in principle and are described in detail in the abovementioned prior art (cf., for example, U.S. Pat. No. 6, 5158922, column 6, lines 9 to 65). The complexing ligand can be added either during the preparation of the catalyst or immediately after the catalyst has precipitated. The complexing ligand is generally used in excess. Preferred complexing ligands are water-soluble, heteroatom-bearing organic compounds which can form complexes with double metal cyanides. Suitable organic complexing ligands are, for example, alcohols, aldehydes, ketones, ethers, esters, amides, ureas, nitrides, sulfides and mixtures thereof. Preferred organic complexing ligands are water-soluble aliphatic alcohols, such as, for example, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol and tert-butanol. Tert-butanol is particularly preferred.

The DMC catalysts of the present invention contain double metal cyanide in an amount of from 20 to 85% by weight, preferably from 25 to 80% by weight, based on the amount of finished catalyst, and the organic complexing ligand in an amount of from 1 to 30% by weight, preferably from 2 to 20% by weight, based also on the amount of finished catalyst.

The DMC catalysts of the present invention contain from 5 to 80% by weight of polyester, based on the amount of catalyst produced. A preferred catalyst comprises 10 to 60% by weight of polyester.

Polyesters suitable for preparing the catalysts of the invention are high molecular weight materials containing ester groups-O-CO-as repeating units of the chain. They are usually obtained by polycondensation of polyfunctional carboxylic acids and hydroxyl compounds. Other common preparation methods for polyesters include polycondensation of hydroxycarboxylic acids, polymerization of cyclic esters (lactones), polyaddition of polycarboxylic anhydrides with epoxides, and reaction of acid chlorides with alkali metal salts of hydroxy compounds. Transesterification of compounds with hydroxyl or carboxyl groups is also possible.

The preparation of polyesters is generally well known and is described in detail, for example, in "handbook of plastics", volume 7, polyurethane, third edition, 1993, p.67-74; "high polymer", volume 16, polyurethane: chemistry and technology, i. chemistry, first edition, 1962, p.44-66; "Ullmann's encyclopedia of Industrial chemistry", volume 19, fourth edition, 1982, p.61-88 and "Houben-Weyl, modern organic chemistry", volume E20, high molecular weight materials, fourth edition, 1987, p.1405-1457.

The polyesters preferably used are linear or partially branched polyesters having an average molecular weight of less than 10000, which are generally obtained by polycondensation of saturated or unsaturated aliphatic, cycloaliphatic or aromatic dicarboxylic acids with difunctional or trifunctional hydroxy compounds or mixtures of difunctional and trifunctional hydroxy compounds, and also by ring-opening polymerization of lactones, for example caprolactone, with diols and/or triols as starting compounds.

Particularly preferably used are polyesters having an average molecular weight of 400-6,000 and a hydroxyl number of 28-300mgKOH/g, which are suitable for the preparation of polyurethanes. These polyesters are generally prepared by the polycondensation of polyfunctional carboxylic acids and hydroxyl compounds. Possible polyfunctional hydroxy compounds for use herein are: in particular, ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propanediol, diisopropyl alcohol, 1, 3-butanediol, 1, 4-butanediol, 1, 6-hexanediol, 1, 12-decanediol, neopentyl glycol, trimethylolpropane, trimethylolethane, glycerol, and, in the less common case, certain long-chain trihydroxy compounds.

Possible polyfunctional carboxylic acids are: in particular, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, oxalic acid, succinic acid, glutaric acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, and, in an unusual case, the so-called "dimer acids" (obtained by dimerizing unsaturated vegetable fatty acids).

To prepare DMC catalysts that reduce the induction period and increase activity, both organic complexing ligands and polyesters are used (see examples 7-8 and comparative examples 6 and 9). The composition of the catalyst is generally determined by elemental analysis and thermogravimetric analysis.

The catalyst of the invention may be crystalline, partially crystalline or amorphous. The crystallinity is generally determined by powder X-ray diffraction.

Preferably the catalyst of the invention is a catalyst comprising

a) Zinc hexacyanocobaltate (III) and

b) tert-butanol, characterized in that it comprises 5 to 80% by weight of a polyester having an average molecular weight of 400-000 and a hydroxyl number of 28 to 300mg KOH/g, based on the amount of catalyst produced.

The improved DMC catalysts of the present invention are generally prepared in aqueous solution by reacting a metal salt (in excess) with a cyanide metal salt in the presence of an organic complexing ligand and a polyester.

Preferably, in this preparation process, an aqueous solution of a metal salt, such as zinc chloride, in an amount in excess of the stoichiometric amount (at least 50% based on the cyanide metal salt) and an aqueous solution of a cyanide metal salt, such as potassium hexacyanocobaltate, are first reacted in the presence of an aqueous solution of an organic complexing ligand, such as t-butanol, to form a suspension containing a double metal cyanide, such as zinc hexacyanocobaltate, excess metal salt, water and organic complexing ligand.

The organic complexing ligand may be present in one or both of the aqueous solutions or may be added to the suspension immediately after precipitation of the double metal cyanide compound. It has proven advantageous to mix the aqueous solution and the organic complexing ligand with vigorous stirring.

The catalyst suspension formed is then treated with polyester. In this process, the polyesters are preferably used as a mixture with water and organic complexing ligands.

The polyester-containing catalyst is separated from the suspension by known separation methods, such as centrifugation or filtration.

In order to increase the activity of the catalyst, it is advantageous if the separated catalyst is subsequently washed with an aqueous solution of the organic complexing ligand (for example by resuspension and subsequent separation by filtration or centrifugation). In this way, it is possible to remove, for example, water-soluble by-products, such as potassium chloride, which adversely affects the polyaddition reaction, from the catalyst of the invention.

The amount of organic complexing ligand in the aqueous washing solution is preferably 40 to 80% by weight. It is also advantageous to add small amounts, preferably from 0.5 to 5% by weight, of polyester to the aqueous washing solution.

The number of times of washing the catalyst is more preferably one or more. The first washing operation, for example, may be repeated once. However, it is preferred to carry out the next washing operation with a non-aqueous solution, for example a mixture of an organic complexing ligand and a polyester.

The washed catalyst is finally dried at 20-100 ℃ and 10Pa to atmospheric pressure (1013 mbar) and optionally after comminution.

It is a further object of the present invention to use the improved DMC catalysts of the present invention for the preparation of polyether polyols by polyaddition of alkylene oxides onto starter compounds containing active hydrogen atoms.

Alkylene oxides which are preferably used are ethylene oxide, propylene oxide, butylene oxide and mixtures thereof. The polyether chains can be built up, for example, by alkoxylation with only one monomeric epoxide, or else random or block polyether chains can be built up by alkoxylation with 2 or 3 different monomeric epoxides. For a more detailed description, see Ullmann's encyclopedia of Industrial chemistry, English edition, 1992, volume A21, page 670-671.

Compounds having a molecular weight of 18 to 2,000 and 1 to 8 hydroxyl groups are used as starting compounds containing active hydrogen atoms. Examples which may be mentioned are: ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propanediol, 1, 4-butanediol, hexanediol, bisphenol a, trimethylolpropane, glycerol, pentaerythritol, sorbitol, sucrose, degraded starch and water.

It is advantageous to use those starting compounds which contain active hydrogen atoms, which are, for example, prepared by conventional base catalysis from the abovementioned low molecular weight starting compounds and are oligomeric, alkoxylation products having a molecular weight of 200-.

The polyaddition of alkylene oxides on starter compounds containing active hydrogen atoms, catalyzed by the catalysts of the invention, is generally carried out at temperatures of from 20 to 200 ℃, preferably from 40 to 180 ℃ and particularly preferably from 50 to 150 ℃And (4) carrying out the reaction at a certain temperature. The reaction may be carried out at a total pressure of 0 to 2X 10⁶pa. The polyaddition reaction can be carried out in bulk or in an inert organic solvent, such as toluene and/or THF. The amount of solvent is generally from 10 to 30% by weight, based on the amount of polyether polyol to be prepared.

The catalyst concentration is chosen so that the polyaddition reaction can be controlled very well under the given reaction conditions. The catalyst concentration is generally from 0.0005 to 1% by weight, preferably from 0.001 to 0.1% by weight, based on the amount of polyether polyol to be prepared.

The molecular weight of the polyether polyol prepared by the process of the present invention is in the range of 500-100,000g/mol, preferably in the range of 1,000-50,000g/mol, more preferably in the range of 2,000-20,000 g/mol.

The polyaddition reaction can be carried out continuously or in a batch or semibatch process.

The catalysts of the invention generally require an induction period of several minutes up to several hours.

By means of the novel catalysts of the invention, the induction period in the preparation of polyether polyols is greatly shortened in comparison with the DMC catalysts known hitherto.

At the same time, the alkoxylation time is also greatly reduced, since the activity is significantly increased.

This results in a reduction of the total reaction time (sum of induction period and alkoxylation time) of typically about 60 to 70% compared to the DMC catalysts known hitherto.

Since the activity of the catalysts of the invention is greatly increased, they can be used at relatively low concentrations (below 15ppm, based on the amount of polyether polyol to be prepared, see example 10), and for polyurethanes, the removal of the catalyst from the polyol can generally be omitted without affecting the quality of the product.

Detailed Description

Examples Catalyst preparation Comparative example 1

DMC catalyst was prepared using tert-butanol as organic complexing ligand, without using polyester (catalyst A, synthesis according to JP 4145123).

A solution of 10g (73.3mMol) of zinc chloride in 15ml of distilled water is added to a solution of 4g (12mMol) of potassium hexacyanocobaltate in 75ml of distilled water with vigorous stirring. Immediately thereafter, a mixture of 50g of tert-butanol and 50g of distilled water was added to the suspension formed, and the mixture was then stirred vigorously for 10 minutes. The solid was separated by filtration, and then the solid was stirred with a mixture of 125g of t-butanol and distilled water (70/30; w/w) for 10 minutes and then filtered. Finally, the mixture was stirred with 125g of tert-butanol for 10 minutes. After filtration, the catalyst was dried at 50 ℃ and atmospheric pressure to a constant weight.

Yield of dried catalyst powder: 3.08g

Elemental analysis: cobalt 13.6%, zinc 27.35%, tert-butanol 14.2% (polyester 0).Example 2

The DMC catalyst (catalyst B) was prepared using tert-butanol as organic complexing ligand and using a linear polyester.

A solution of 12.5g (91.5mMol) of zinc chloride in 20ml of distilled water was added to a solution of 4g (12mMol) of potassium hexacyanocobaltate in 75ml of distilled water with vigorous stirring (24,000 rpm). Immediately thereafter, a mixture of 50g of tert-butanol and 50g of distilled water was added to the suspension formed, and the mixture was then stirred vigorously (24,000rpm) for 10 minutes. Then a mixture of 1g of a linear polyester of adipic acid and ethylene glycol (poly (ethylene adipate)) having an average molecular weight of 2,000 (hydroxyl number 55mg KOH/g), 1g of tert-butanol and 100g of distilled water was added, and the mixture was stirred (1000rpm) for 3 minutes. A solid was separated by filtration, and then the solid was stirred (10,000rpm) with a mixture of 70g of t-butanol, 30g of distilled water and 1g of the above-mentioned polyester, followed by filtration. Finally, the mixture was stirred (10,000rpm) with 100g of tert-butanol and 0.5g of the polyester described above for a further 10 minutes. After filtration, the catalyst was dried at 50 ℃ and atmospheric pressure to a constant weight.

Yield of dried catalyst powder: 4.87g

Elemental analysis: cobalt is 10.0%; 20.9 percent of zinc; t-butanol 7.5%; 22.1% of polyester.Example 3

The DMC catalyst (catalyst C) was prepared using tert-butanol as organic complexing ligand and a partially branched polyester.

The same as example 2, but using a polyester of adipic acid and ethylene glycol of average molecular weight 2,300 (hydroxyl number 50mg KOH/g) weakly branched with trimethylolpropane instead of the polyester of example 2.

Yield of dried catalyst powder: 3.85g

Elemental analysis: cobalt is 12.2%; 25.7 percent of zinc; t-butanol 7.1%; polyester ═ 12.3%.Comparative example 4

The DMC catalyst (catalyst D) was prepared using polyester but no tert-butanol as the organic complexing ligand.

A solution of 12.5g (91.5mMol) of zinc chloride in 20ml of distilled water was added to a solution of 4g (12mMol) of potassium hexacyanocobaltate in 75ml of distilled water with vigorous stirring (24,000 rpm). Immediately thereafter, a mixture of 1g of the polyester of example 2 and 100g of distilled water was added to the suspension formed, and the mixture was then stirred vigorously (24,000rpm) for 10 minutes. The solid was isolated by filtration, and then stirred (10,000rpm) with a mixture of 1g of polyester and 100g of distilled water for 10 minutes, followed by filtration. Finally, the mixture was stirred (10,000rpm) for a further 10 minutes with a mixture of 0.5g of polyester and 100g of distilled water. After filtration, the catalyst was dried at 50 ℃ and atmospheric pressure to a constant weight.

Yield of dried catalyst powder: 5.27g

Elemental analysis: cobalt 9.5%, zinc 16.6%, polyester 25.0% (t-butanol 0).Comparative example 5

The DMC catalyst was prepared using tert-butanol as organic complexing ligand and a polyether (catalyst E, synthesis according to EP 700949).

A solution of 12.5g (91.5mMol) of zinc chloride in 20ml of distilled water was added to a solution of 4g (12mMol) of potassium hexacyanocobaltate in 75ml of distilled water with vigorous stirring (24,000 rpm). Immediately thereafter, a mixture of 50g of tert-butanol and 50g of distilled water was added to the suspension formed, and the mixture was then stirred vigorously (24,000rpm) for 10 minutes. Then, a mixture of 1g of polypropylene glycol having an average molecular weight of 2,000 (hydroxyl number: 56mg KOH/g), 1g of t-butanol and 100g of distilled water was added, and the mixture was stirred (1,000rpm) for 3 minutes. The solid was separated by filtration, and then stirred (10,000rpm) with 70g of t-butanol, 30g of distilled water and 1g of the above polyether mixture for 10 minutes, followed by filtration. Finally, the mixture was stirred (10,000rpm) with 100g of tert-butanol and 0.5g of the polyether described above for a further 10 minutes. After filtration, the catalyst was dried at 50 ℃ and atmospheric pressure to a constant weight.

Yield of dried catalyst powder: 6.23g

Elemental analysis: 11.6% of cobalt, 24.6% of zinc, 3.0% of tert-butanol and 25.8% of polyether.Preparation of polyether polyols General procedure

50g of polypropylene glycol starting compound (molecular weight 1,000g/mol) and 3 to 20mg of catalyst (15 to 100ppm, based on the amount of polyether polyol to be prepared) are initially introduced under inert gas (argon) into a 500ml pressure reactor and heated to 105 ℃ with stirring. Propylene oxide (about 5g) was then metered in immediately until the total pressure had risen to 2.5X 10⁵Pa. Only when an accelerated drop in the reactor pressure was observed was the remainder of the propylene oxide metered in. This accelerated drop in pressure indicates that the catalyst is active. The remainder of the propylene oxide (145g) was then added at a total pressure of 2.5X 10⁵The metering is carried out continuously at Pa. After completion of the metering of propylene oxide and after 5 hours at 105 ℃ post-reaction, the reaction is carried out at 90 ℃ (1X 10)²Pa) volatiles were distilled off and the product was then cooled to room temperature.

The polyether polyols obtained were characterized by determining the number of hydroxyl groups, the double bond content and the molecular weight distribution Mw/Mn (MALDI-TOF-MS).

The progress of the reaction is monitored by means of a time/conversion curve (consumption of propylene oxide [ g ] vs. reaction time [ min ]). The induction period is determined by the intersection of the tangent line at the steepest point of the time/conversion curve with the extension of the baseline of the time/conversion curve.

The propoxylation time, which is indicative of the catalyst activity, is the time corresponding to the time between the activation of the catalyst (end of the induction period) and the end of the propylene oxide dosing.

The total reaction time is the sum of the induction period and the propoxylation time.Comparative example 6

Preparation of polyether polyol with catalyst A (100ppm)

An induction period: 290min

Time of propoxylation: 165min

Total reaction time: 455min

Polyether polyol: hydroxyl number (mgKOH/g) 28.5

Double bond content (mMol/kg) 6

M_w/M_n： 1.12Example 7

Preparation of polyether polyol with catalyst B (100ppm)

An induction period: 80min

Time of propoxylation: 55min

Total reaction time: 135min

Polyether polyol: hydroxyl number (mgKOH/g) 29.7

Double bond content (mMol/kg) 5

M_w/M_n： 1.04Example 8

Preparation of polyether polyol with catalyst C (100ppm)

An induction period: 70min

Time of propoxylation: 50min

Total reaction time: 120min

Polyether polyol: hydroxyl number (mgKOH/g) 29.6

Double bond content (mMol/kg) 5

M_w/M_n： 1.04Comparative example 9

Preparation of polyether polyol with catalyst D (100ppm)

An induction period: more than 700min

Time of propoxylation: is inactive

Comparison between examples 7-8 and comparative example 6 shows that the induction period is significantly reduced with the DMC catalysts of the invention containing an organic complexing ligand (tert-butanol) and a polyester compared to the DMC catalyst containing only an organic complexing ligand (tert-butanol) in the preparation of polyether polyols, and that the catalysts of the invention simultaneously have a greatly increased activity (as can be seen from the greatly shortened propoxylation time).

Comparative example 9 shows that DMC catalysts containing no organic complexing ligand but only polyester are inactive.Example 10

Preparation of polyether polyol with catalyst C (15ppm)

Total reaction time: 335min

Polyether polyol: hydroxyl number (mgKOH/g) 27.4

Double bond content (mMol/kg) 5

M_w/M_n： 1.05

Metal content in polyether without removal of catalyst: zn is 4ppm and Co is 2 ppm.

Example 10 shows that the separation of the catalyst from the polyol can be omitted because the novel DMC catalysts of the present invention have a very high activity and can be used in low concentrations for the preparation of polyether polyols.Comparative example 11

Preparation of polyether polyol with catalyst E (15ppm)

Total reaction time: 895min

Polyether polyol: hydroxyl number (mgKOH/g) 29.8

Double bond content (mMol/kg) 6

M_w/M_n： 1.04

Comparison between example 10 and comparative example 11 shows that the novel DMC catalysts of the present invention, which contain an organic complexing ligand (tert-butanol) and a polyester, are much more active than the highly active DMC catalysts known to date, which contain an organic complexing ligand (tert-butanol) and a polyether (comparable to the molecular weight and number of hydroxyl groups of the polyester used in the present invention). Therefore, the polyether polyol prepared by the novel catalyst can greatly shorten the total reaction time.

Claims (8)

1. A Double Metal Cyanide (DMC) catalyst comprising:

a) double metal cyanide compounds and

b) an organic complexing ligand characterised in that it comprises 5-80% polyester, based on the weight of the finished catalyst.

2. The DMC catalyst of claim 1, characterized in that the double metal cyanide is zinc hexacyanocobaltate (III).

3. The DMC catalyst of claim 1, wherein the organic complexing ligand is t-butanol.

4. DMC catalyst according to any of claims 1 to 3, characterized in that they contain 10 to 60% by weight of polyester.

5. DMC catalyst according to any of claims 1 to 3, characterized in that they comprise linear or partially branched polyesters having an average molecular weight of less than 10,000, which are obtained by polycondensation of saturated or unsaturated aliphatic, cycloaliphatic or aromatic dicarboxylic acids with difunctional or trifunctional hydroxy compounds, and which are also obtained by ring-opening polymerization of lactones with diols and/or triols.

6. DMC catalyst according to any of claims 1 to 3, characterized in that they contain polyesters having an average molecular weight of 400 and a hydroxyl number of 28 to 300 mgKOH/g.

7. A process for the preparation of DMC catalysts as claimed in claim 1, characterized in that an excess of metal salt is reacted with a cyanide metal salt in the presence of an organic complexing ligand and a polyester in aqueous solution, and the catalyst obtained is isolated, washed and dried to give the end product.

8. Use of the DMC catalyst of claim 1 for the preparation of polyether polyols by polyaddition of alkylene oxides on starter compounds containing active hydrogen atoms.