Method for preparing double metal cyanide catalyst

Abstract

The present invention relates to an improved process for the preparation of double metal cyanide (DMC) catalysts for the preparation of polyoxyalkylene polyols, preferably polyether polyols and / or polyether carbonate polyols. A further subject of the invention is a DMC catalyst obtainable by such a method, and the use of a catalyst according to the invention for producing polyoxyalkylene polyols.

Description

[0001] The present invention relates to an improved process for preparing double metal cyanide (DMC) catalysts for preparing polyoxyalkylene polyols, preferably polyether polyols and / or polyether carbonate polyols. Another subject of the present invention is the DMC catalyst obtainable by this process and the use of the catalyst according to the invention for preparing polyoxyalkylene polyols.

[0002] DMC catalysts are known in principle from the prior art (see, for example, US-A 3404109, US-A 3829505, US-A 3941849 and US-A 5158922). DMC catalysts such as those described in US-A 5470813, EP-A 700949, EP-A 743093, EP-A 761708, WO 97 / 40086, WO 98 / 16310, WO 00 / 47649 and WO 2021 / 165283 A1 have very high activity in the homopolymerization of epoxides and enable the preparation of polyether polyols at very low catalyst concentrations (25 ppm or less), so that it is generally no longer necessary to remove the catalyst from the finished product. Typical examples are the highly active DMC catalysts described in EP-A 700949 which contain not only a double metal cyanide compound (eg zinc hexacyanocobaltate(III)) and an organic complexing ligand (eg tert-butanol) but also a polyether having a number average molecular weight of more than 500 g / mol.

[0003] WO 01 / 39883 A1 discloses a process for preparing a double metal cyanide (DMC) catalyst for preparing polyether polyols by polyaddition of alkylene oxides onto starter compounds having active hydrogen atoms, in which a DMC catalyst dispersion is prepared using a mixing nozzle, preferably a jet disperser. The DMC catalyst thus prepared has an increased activity in the preparation of polyether polyols, a reduced particle size and a narrower particle size distribution.

[0004] WO 01 / 80994 A1 likewise discloses a process for preparing a double metal cyanide (DMC) catalyst (DMC), wherein aqueous solutions of metal salts and metal cyanide salts are first reacted in the presence of an organic complexing ligand and optionally one or more other complex-forming components to form a DMC catalyst dispersion, this dispersion is then filtered, the filter cake is subsequently washed by filter cake washing with one or more aqueous or nonaqueous solutions of the organic complexing ligand and optionally one or more other complex-forming components, and the washed filter cake is finally dried after optional squeezing or mechanical removal of water. The disclosed process shortens the catalyst preparation time, wherein the resulting catalyst has an activity comparable to that of a reference catalyst in the preparation of polyether polyols.

[0005] EP 700949 A2 describes a DMC catalyst containing a DMC compound, an organic complexing ligand and 5% to 80% by weight of a polyether having a number average molecular weight of >500 g / mol, wherein the preparation of the DMC catalyst dispersion is carried out at room temperature. The catalyst used is usually active in the preparation of polyether polyols.

[0006] WO 2021 / 148272 A1 discloses a method for preparing a double metal cyanide catalyst (DMC), wherein the resulting DMC catalyst exhibits improved catalytic activity in the preparation of polyoxyalkylene polyols, for example in a catalyst test according to the "8K Diol Stressed Tests". Here, an aqueous solution of a cyanide-free metal salt, an aqueous solution of a metal cyanide salt, an organic complexing ligand and propylene glycol as a component for forming a complex are reacted to form a dispersion, wherein the reaction is carried out using a mixing nozzle and wherein the process temperature of the dispersion during the reaction is between 26°C and 49°C.

[0007] The object of the present invention is to provide an improved process for preparing double metal cyanide (DMC) catalysts, which have a further increased catalytic activity in the preparation of polyoxyalkylene polyols, preferably polyether polyols and / or polyether carbonate polyols, wherein this improved activity leads, for example, to a reduction in product viscosity in a semi-batch polyol preparation process according to the "8K diol stress test" described, for example, in WO 98 / 16310 A1 and in catalyst tests in a continuous polyol preparation process. The goal is therefore to provide more catalytically active DMC catalysts, which lead to polyoxyalkylene polyols, preferably polyether polyols and / or polyether carbonate polyols, having a reduced viscosity, thus facilitating the further processability of the polyoxyalkylene polyols in the subsequent polyurethaneization reaction. The increased catalyst activity also makes it possible to reduce the amount of catalyst used, which improves the economic feasibility of the process.

[0008] At the same time, the process for preparing DMC catalyst dispersions should be carried out with a relatively simple apparatus configuration, low energy demand during shearing, good temperature control and likewise good scalability compared to known industrial processes, so that it can be easily implemented in existing DMC catalyst preparation processes, for example in loop reactors.

[0009] Surprisingly, it has now been found that a process for preparing a double metal cyanide (DMC) catalyst achieves the above-mentioned objects, said process comprising

[0010] i) reacting an aqueous solution of a cyanide-free metal salt, an aqueous solution of a metal cyanide salt, an organic complexing ligand and a complex-forming component, characterized in that the complex-forming component contains one or more compounds (1) of formula (I):

[0011] R1-O-(R2-O) n -H(I)

[0012] in

[0013] R1 is a substituted or unsubstituted aryl group,

[0014] R2 is an alkylene group, preferably an ethylene group or an isopropylene group, particularly preferably an ethylene group (Et), and

[0015] n≧1, preferably 5≦n≦80, particularly preferably 7≦n≦70, very particularly preferably 8≦n≦60.

[0016] The invention is explained in more detail below, wherein the embodiments according to the invention can be combined with one another as desired, as long as the contrary is not obvious from the technical background.

[0017] Components that form complexes

[0018] Compound (1)

[0019] According to the present invention, the components forming the complex contain one or more compounds (1) of formula (I):

[0020] R1-O-(R2-O) n -H(I)

[0021] in

[0022] R1 is a substituted or unsubstituted aryl group,

[0023] R2 is an alkylene group, preferably an ethylene group or an isopropylene group, particularly preferably an ethylene group (Et), and

[0024] n≧1, preferably 5≦n≦80, particularly preferably 7≦n≦70, very particularly preferably 8≦n≦60.

[0025] In one embodiment of the process according to the invention, R1 has a structure according to formula (II):

[0026]

[0027] in

[0028] R3, R4, R5, R6, R7 are independently selected from hydrogen, a straight-chain or branched alkyl group having 1 to 22 carbon atoms, an alicyclic group having 3 to 22 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 16 carbon atoms.

[0029] In a preferred embodiment of the process according to the invention, R3, R5 and R7 are independently selected from hydrogen, straight-chain or branched alkyl groups having 1 to 22 carbon atoms, alicyclic groups having 3 to 22 carbon atoms and substituted or unsubstituted aryl groups having 6 to 16 carbon atoms, and R4 and R6 are hydrogen.

[0030] In a particularly preferred embodiment of the process according to the invention, R3, R5 and R7 are independently selected from linear or branched alkyl groups having 1 to 10 carbon atoms and substituted or unsubstituted aryl groups having 6 to 12 carbon atoms, and R4 and R6 are hydrogen.

[0031] In one embodiment of the method according to the invention, R1 has a structure according to formula (III), (IV) or (V):

[0032]

[0033] In a preferred embodiment of the process according to the invention, R1 has a structure according to formula (III).

[0034] In one embodiment of the method according to the invention, compound (1) has a structure according to formula (VI), (VII) and / or (VIII):

[0035]

[0036]

[0037] Among them, n≥1, preferably 5≤n≤80, particularly preferably 7≤n≤70, and most preferably 8≤n≤60.

[0038] In a preferred embodiment of the process according to the invention, compound (1) has a structure according to formula (VI), wherein 5≤n≤80, preferably 7≤n≤70, particularly preferably 8≤n≤60, wherein such compound (VI) is also referred to as tri-sec-butylphenol ethoxylate having 5 to 80, preferably 7 to 70, particularly preferably 8 to 60 ethoxy units.

[0039] Compound (2)

[0040] In one embodiment of the method according to the invention, the components forming the complex contain not only compound (1) but also one or more compounds (2), wherein the compound (2) can be selected from the compound classes of polyethers, polyesters, polycarbonates, polyalkylene glycol sorbitan esters, polyalkylene glycol glycidyl ethers, polyacrylamide, poly(acrylamide-co-acrylic acid), polyacrylic acid, poly(acrylic acid-co-maleic acid), polyacrylonitrile, polyalkyl acrylates, polyalkyl methacrylates, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl acetate, polyvinyl alcohol, poly-N-vinyl pyrrolidone, poly(N-vinyl pyrrolidone-co-acrylic acid), polyvinyl methyl ketone, poly(4-vinylphenol), poly(acrylic acid-co-styrene), oxazoline polymers, polyalkyleneimines, copolymers of maleic acid and maleic anhydride, hydroxyethylcellulose and polyacetals, or glycidyl ethers, glycosides, carboxylates, esters or amides of polyols, cyclodextrins or phosphorus compounds.

[0041] In the process according to the invention for preparing a DMC catalyst, preference is given to using polyethers as compound (2).

[0042] In a preferred embodiment, the polyethers have a number-average molecular weight of ≧500 g / mol, the number-average molecular weight being calculated from the determined OH number.

[0043] The OH value was determined according to DIN 53240.

[0044] Suitable polyethers include those prepared by ring-opening polymerization of cyclic ethers, wherein these cyclic ethers also include, for example, oxetane polymers and tetrahydrofuran polymers. Various catalysis may be used for this purpose. The polyethers have suitable end groups, for example hydroxyl, amine, ester or ether end groups.

[0045] In a particularly preferred embodiment, the polyethers have an average hydroxyl functionality of 2 to 8 and a number average molecular weight in the range from 500 g / mol to 10 000 g / mol, preferably from 700 g / mol to 5000 g / mol, the number average molecular weight being calculated from the determined OH number.

[0046] In a particularly preferred embodiment, the polyether is a polyether polyol, wherein the polyether polyol is obtained by reacting an alkylene oxide with an H-functional starter compound in the presence of an acidic, basic and / or organometallic catalyst. These organometallic catalysts are, for example, double metal cyanide (DMC) catalysts.

[0047] Suitable polyether polyols are poly(oxypropylene) polyols, poly(oxypropyleneoxyethylene) polyols, polytetramethylene ether glycols and block copolymers containing poly(oxy)ethylene, poly(oxy)propylene and / or poly(oxy)butylene blocks, for example poly(oxy)ethylene-poly(oxy)propylene block copolymers having terminal poly(oxy)ethylene blocks.

[0048] In a preferred embodiment, the polyether polyol is a poly(oxypropylene) polyol having a number-average molecular weight of ≧500 g / mol, wherein the number-average molecular weight is calculated from the determined OH number.

[0049] In a particularly preferred embodiment, the polyether polyol is a poly(oxypropylene)polyol, preferably a poly(oxypropylene)diol and / or a poly(oxypropylene)triol, having a number average molecular weight of 700 g / mol to 4000 g / mol, wherein the number average molecular weight is calculated from the determined OH number.

[0050] In an alternative embodiment, the polyether has an average hydroxyl functionality of 2 to 8 and a number average molecular weight in the range of 150 g / mol to less than 500 g / mol, preferably 200 g / mol to 400 g / mol, wherein the number average molecular weight is calculated from the determined OH number.

[0051] In a preferred alternative embodiment, the alternative polyethers are polyether polyols, wherein these alternative polyether polyols have an average hydroxyl functionality of 2 to 8 and a number average molecular weight in the range of 150 g / mol to less than 500 g / mol, preferably an average hydroxyl functionality of 2 to 8 and a number average molecular weight in the range of 200 g / mol to 400 g / mol, wherein the number average molecular weight is calculated from the determined OH number. These alternative polyether polyols are likewise obtained by reacting alkylene oxides and H-functional starter compounds in the presence of acidic, basic and / or organometallic catalysts. These organometallic catalysts are, for example, double metal cyanide (DMC) catalysts.

[0052] Suitable alternative polyether polyols are poly(oxypropylene) polyols, poly(oxypropyleneoxyethylene) polyols, polytetramethylene ether glycols and block copolymers containing poly(oxy)ethylene, poly(oxy)propylene and / or poly(oxy)butylene blocks, for example poly(oxy)ethylene-poly(oxy)propylene block copolymers with terminal poly(oxy)ethylene blocks. Tripropylene glycol, triethylene glycol, tetrapropylene glycol, tetraethylene glycol, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether and mono- and dialkyl ethers of diols and poly(alkylene glycols) are also suitable.

[0053] In a particularly preferred alternative embodiment, the alternative polyether polyol is a polypropylene glycol and / or polyethylene glycol having a number average molecular weight in the range from 150 g / mol to less than 500 g / mol, the number average molecular weight being calculated from the determined OH number.

[0054] In a preferred embodiment of the method according to the present invention, the molar ratio of compound (1) to compound (2) is from 50:1 to 1:50, preferably from 20:1 to 1:20.

[0055] In an alternative embodiment of the process according to the invention, the components forming the complex contain no further compounds (2) in addition to the compound (1).

[0056] Cyanide-free metal salts

[0057] Cyanide-free metal salts suitable for preparing double metal cyanide compounds preferably have the general formula (IX),

[0058] M(X) n (IX)

[0059] in

[0060] M is selected from the metal cation Zn 2+ , Fe 2+ 、Ni 2+ , Mn 2+ 、Co 2+ , Sr 2+ Sn 2+ , Pb 2+ and Cu 2+ ; M is preferably Zn 2+ , Fe 2 + 、Co 2+ or Ni 2+ ,

[0061] X is one or more (i.e. different) anions, preferably anions selected from halide (i.e. fluoride, chloride, bromide, iodide), hydroxide, sulfate, carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate, oxalate and nitrate;

[0062] When X = sulfate, carbonate or oxalate, n is 1, and

[0063] When X = halide, hydroxide, cyanate, thiocyanate, isocyanate, isothiocyanate or nitrate, n is 2,

[0064] Or a suitable cyanide-free metal salt has the general formula (X),

[0065] M r(X)3(X)

[0066] in

[0067] M is selected from the metal cation Fe 3+ 、Al 3+ and Cr 3+ ,

[0068] X is one or more (i.e. different) anions, preferably anions selected from halide (i.e. fluoride, chloride, bromide, iodide), hydroxide, sulfate, carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate, oxalate and nitrate;

[0069] When X = sulfate, carbonate or oxalate, r is 2, and

[0070] When X = halide, hydroxide, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate or nitrate, r is 1,

[0071] Or a suitable cyanide-free metal salt has the general formula (XI),

[0072] M(X) s (XI)

[0073] in

[0074] M is selected from the metal cation Mo 4+ 、V 4+ and W 4+ ,

[0075] X is one or more (i.e. different) anions, preferably anions selected from halide (i.e. fluoride, chloride, bromide, iodide), hydroxide, sulfate, carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate, oxalate and nitrate;

[0076] When X = sulfate, carbonate or oxalate, s is 2, and

[0077] When X = halide, hydroxide, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate or nitrate, s is 4,

[0078] Or a suitable cyanide-free metal salt has the general formula (XII),

[0079] M(X) t (XII)

[0080] in

[0081] M is selected from the metal cation Mo 6+ and W 6+ ,

[0082] X is one or more (i.e. different) anions, preferably anions selected from halide (i.e. fluoride, chloride, bromide, iodide), hydroxide, sulfate, carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate, oxalate and nitrate;

[0083] When X = sulfate, carbonate or oxalate, t is 3, and

[0084] When X = halide, hydroxide, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate or nitrate, t is 6.

[0085] In a preferred embodiment of the method according to the invention, the cyanide-free metal salt of the aqueous solution of the cyanide-free metal salt is one or more compounds selected from zinc chloride, zinc bromide, zinc iodide, zinc acetate, zinc acetylacetonate, zinc benzoate, zinc nitrate, iron(II) sulfate, iron(II) bromide, iron(II) chloride, cobalt(II) chloride, cobalt(II) thiocyanate, nickel(II) chloride and nickel(II) nitrate, particularly preferably zinc chloride.

[0086] Metal cyanide salts

[0087] Metal cyanide salts suitable for preparing double metal cyanide compounds preferably have the general formula (XIII)

[0088] (Y) a M'(CN) b (A) c (XIII)

[0089] in

[0090] M' is one or more metal cations selected from 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 preferably one or more metal cations selected from Co(II), Co(III), Fe(II), Fe(III), Cr(III), Ir(III) and Ni(II),

[0091] Y is selected from alkali metals (i.e. Li + 、Na + , K + , Rb + , Cs + ) and alkaline earth metals (i.e. Be 2+ , Ca 2+ Mg 2+ , Sr 2+ , Ba2+ ), one or more metal cations,

[0092] A is selected from one or more anions of halide (i.e., fluoride, chloride, bromide, iodide), hydroxide, sulfate, carbonate, cyanate, thiocyanate, isocyanate, isothiocyanate, carboxylate, oxalate, or nitrate, and

[0093] a, b and c are integers, wherein the values ​​of a, b and c are selected to ensure the electronic neutrality of the metal cyanide salt; a is preferably 1, 2, 3 or 4; b is preferably 4, 5 or 6; c preferably has the value 0.

[0094] In a preferred embodiment of the method according to the invention, the metal cyanide salt of the aqueous solution of a metal cyanide salt is one or more compounds selected from the group consisting of potassium hexacyanocobaltate (III), potassium hexacyanoferrate (II), potassium hexacyanoferrate (III), calcium hexacyanocobaltate (III) and lithium hexacyanocobaltate (III), particularly preferably potassium hexacyanocobaltate (III).

[0095] Preferred double metal cyanide compounds contained in the DMC catalyst according to the invention are compounds of the general formula (XIV)

[0096] M x [M' x ,(CN) y ] z (XIV), wherein M is as defined in formula (IX) to (XII), and

[0097] M' is as defined in formula (XIII), and

[0098] x, x', y and z are integers and are selected to ensure electronic neutrality of the double metal cyanide compound.

[0099] Preferably, x=3, x'=1, y=6 and z=2, M is Zn(II), Fe(II), Co(II) or Ni(II), and M' is Co(III), Fe(III), Cr(III) or Ir(III).

[0100] In a preferred embodiment of the method according to the invention, the double metal cyanide compound is one or more compounds selected from the group consisting of zinc hexacyanocobaltate (III), zinc hexacyanoiridate (III), zinc hexacyanoferrate (III) and cobalt (II) hexacyanocobaltate (III). Particular preference is given to using zinc hexacyanocobaltate (III).

[0101] Organic complexing ligand

[0102] For example, in US 5158922 (see in particular column 6, lines 9 to 65), US 3404109, US 3829505, US 3941849, EP-A 700949, EP-A 761708, JP 4145123, US 5470813, EP-A 743093, WO 99 / 46042 and WO-A 97 / 40086, organic complexing ligands added in the preparation of DMC catalysts are disclosed. The organic complexing ligands used are, for example, water-soluble organic compounds containing heteroatoms, such as oxygen, nitrogen, phosphorus or sulfur, which can form complexes with double metal cyanide compounds. Preferred organic complexing ligands are alcohols, aldehydes, ketones, ethers, esters, amides, ureas, nitriles, thioethers and mixtures thereof. Particularly preferred organic complexing ligands are aliphatic ethers (such as dimethoxyethane), water-soluble aliphatic alcohols (such as ethanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, 2-methyl-3-butene-2-ol and 2-methyl-3-butyn-2-ol), compounds containing aliphatic or alicyclic ether groups and aliphatic hydroxyl groups (such as ethylene glycol mono-tert-butyl ether, diethylene glycol mono-tert-butyl ether, tripropylene glycol monomethyl ether and 3-methyl-3-oxetane methanol). The most preferred organic complexing ligand is selected from one or more compounds of dimethoxyethane, tert-butanol, 2-methyl-3-butene-2-ol, 2-methyl-3-butyn-2-ol, ethylene glycol mono-tert-butyl ether and 3-methyl-3-oxetane methanol.

[0103] In a preferred embodiment of the method according to the present invention, the organic complexing ligand is one or more compounds selected from dimethoxyethane, tert-butanol, 2-methyl-3-butene-2-ol, 2-methyl-3-butyn-2-ol, ethylene glycol mono-tert-butyl ether and 3-methyl-3-oxetanemethanol, particularly preferably tert-butanol.

[0104] Mixing nozzle

[0105] The DMC catalyst dispersion is preferably prepared using mixing nozzles (eg smooth jet nozzles, Levos nozzles, Bosch nozzles etc.), particularly preferably jet dispersers as described in patent application WO 01 / 39883 A1.

[0106] The basic structure and mode of operation of a suitable mixing nozzle are described below. Figure 1The schematic structure of a simple smooth jet nozzle is shown. Reactant stream 1 is first accelerated in nozzle 3 and sprayed into slow-flowing reactant stream 2 at high flow rate. In this process, reactant stream 2 is accelerated and reactant stream 1 is decelerated. A portion of the kinetic energy of reactant jet 1 is converted into heat in this process and is therefore no longer available for mixing operations. The two reactant streams are then mixed by vortexes (vortex cascades) of different sizes decayed by the turbulence of the resulting jet. Compared with a stirred tank, the concentration difference can be significantly reduced more rapidly in this way, because significantly larger and more uniform power density can be achieved. Average power density P is calculated by the following formula at this:

[0107]

[0108] Where: Δp: pressure drop in the nozzle

[0109] Volume flow

[0110] V: Volume of nozzle hole

[0111] The use of such a nozzle shall be referred to as method 1 hereinafter.

[0112] In a smooth jet nozzle, the first reactant stream is first accelerated in the nozzle and injected at a high flow rate into the second reactant stream flowing slowly. The two reactant streams are then mixed by the turbulence of the resulting jet decaying into vortices of different sizes (vortex cascade). Compared with a stirred tank, the concentration differences can be reduced significantly more quickly in this way, since significantly greater and more uniform power densities can be achieved.

[0113] Jet disperser

[0114] For the method according to the invention, it is particularly preferred to use Figure 2 or Figure 3 The jet disperser shown in FIG. The jet disperser can be constructed ( Figure 2) so that the two nozzles 5 and 6 are arranged in succession. The reactant stream 1 is first greatly accelerated in the nozzle 5 by the cross-sectional contraction. The accelerated jet inhales the second component due to the high flow rate in the process. The nozzle spacing is preferably selected so that due to the short residence time, only nucleation occurs in the mixing chamber 4 without crystal growth. The decisive factor for the optimal design of the jet disperser is therefore the nucleation rate of the solid. Advantageously set a residence time of 0.0001s to 0.15s, preferably 0.001s to 0.1s. Crystal growth does not occur until the outlet 3. The diameter of the nozzle 6 should preferably be selected so that the partially mixed reactant stream is further accelerated therein. Due to the shear force thus additionally generated in the nozzle 6, a uniformly mixed state is achieved in a shorter time due to faster vortex decay compared to method 1. Therefore, compared to method 1, it is possible to achieve an ideal mixed state of reactants even in the case of a precipitation reaction with an extremely high nucleation rate, so that it is possible to set a specific stoichiometric composition during the precipitation reaction. The pressure drop in the nozzle of 0.1 bar to 1000 bar or 1*10 7 W / m 3 Up to 1*10 13 W / m 3 At a power density of 1000 Å, a nozzle diameter of 5000 μm to 50 μm, preferably 2000 μm to 200 μm, has proven to be advantageous. This mixing operation is referred to as method 2 below.

[0115] Depending on the desired particle size, further n nozzles (where n=1-5) can be connected downstream to obtain a multistage jet disperser. Figure 3 Such a multi-stage jet disperser is shown. After the nozzle 6, the dispersion is again conducted through the nozzle 7. With regard to the design of the nozzle diameter, what applies to the nozzle 6 also applies here.

[0116] Compared to method 2, an additional advantage of the additional disperser is that the already formed particles can be mechanically comminuted by the high shear forces in the nozzle. It is thus possible to produce particles with a diameter of 10 μm to 0.1 μm. Instead of a plurality of nozzles in series, comminution can also be achieved by circulation of the dispersion. The use of such nozzles is referred to below as method 3.

[0117] Due to the energy dissipation in the nozzle and due to the crystallization enthalpy, heating of the dispersion can result. Since the temperature can have a significant influence on the crystal formation process, heat transfer means can be installed downstream of the mixing element for isothermal process mode.

[0118] It is possible, for example, to achieve unproblematic scaling by using a larger number of holes, connecting a plurality of mixing elements in parallel or by increasing the free nozzle area. However, increasing the free nozzle area cannot be achieved by increasing the nozzle diameter, since this leads to the possibility of core flow, which results in a poorer mixing result. For nozzles with a large free nozzle area, it is therefore preferred to use slits with a corresponding area.

[0119] The DMC catalyst dispersion is preferably prepared using a mixing nozzle, particularly preferably a jet disperser. Examples of suitable apparatus are shown in Figure 4 and 5 middle. Figure 4 A semi-batch process using a loop reactor is shown, Figure 5 A continuous process for preparing a DMC catalyst dispersion is shown.

[0120] In one embodiment of the process according to the invention, the preparation of a double metal cyanide catalyst (DMC) comprises

[0121] i) in a first step, reacting an aqueous solution of a cyanide-free metal salt, an aqueous solution of a metal cyanide salt, an organic complexing ligand and a complex-forming component containing one or more compounds (1) of the formula (I) (according to claim 1) to form a dispersion;

[0122] (ii) optionally, in a second step, separating solids from the dispersion obtained in (i);

[0123] (iii) optionally, in a third step, washing the separated solid with an aqueous solution of an organic complexing ligand by means of a filter cake washing method;

[0124] (iv) and optionally, in a fourth step, drying the resulting solid.

[0125] Step i)

[0126] An aqueous solution of a cyanide-free metal salt, such as zinc chloride, used in a stoichiometric excess (at least 50 mol %, based on the metal cyanide salt), and an aqueous solution of a metal cyanide salt, such as potassium hexacyanocobaltate, are preferably first reacted in the presence of an organic complexing ligand, which may be, for example, tert-butanol, to form a dispersion. Such a DMC catalyst dispersion is preferably prepared using a mixing nozzle, particularly preferably a jet disperser.

[0127] The following describes the loop reactor (according to Figure 4) is used in combination with a jet disperser to prepare a DMC catalyst dispersion in a semi-batch process. Here, the aqueous solution of the cyanide-free metal salt can be circulated from container B2 and the aqueous solution of the metal cyanide can be metered in from container B1, or vice versa. When the two streams are combined in mixing element M, a dispersion of the DMC compound is formed. The dispersion of the DMC compound can be prepared by method 1, 2 or 3, preferably by method 2 or 3. The advantage of these methods is that it is possible to achieve a constant reactant ratio throughout the precipitation process.

[0128] Preferably, the dispersion formed after precipitation is circulated through the jet disperser for a further few minutes to hours.

[0129] The nozzle diameter in this case is preferably between 2000 μm and 200 μm, with the pressure drop in the nozzle being between 0.1 bar and 1000 bar.

[0130] The organic complexing ligand can in this case be present in an aqueous solution of a cyanide-free metal salt and / or an aqueous solution of a metal cyanide salt, or be metered directly into the dispersion obtained after precipitation of the double metal cyanide compound (via container B1 or B2 ).

[0131] In one embodiment of the method according to the invention, the dispersion circulated through the jet disperser subsequently has a complex-forming component containing one or more compounds (1) of the formula (I) metered in via container B1 or B2. The complex-forming component containing one or more compounds (1) of the formula (I) is preferably used in a mixture of water and an organic complexing ligand.

[0132] The metered addition of the complex-forming component containing one or more compounds (1) of the formula (I) into the circuit and the subsequent recirculation are preferably carried out at a pressure drop in the nozzle of between 0.001 bar and 10 bar.

[0133] According to the present invention, it is also possible to Figure 5 The DMC catalyst dispersion is prepared in a continuous process as shown by way of example in . The aqueous solution of the cyanide-free metal salt and the aqueous solution of the metal cyanide salt are reacted in a mixing element M1 according to method 1, 2 or 3 to form a dispersion. The organic complexing ligand may be present in the aqueous solution of the cyanide-free metal salt and / or in the aqueous solution of the metal cyanide salt. In this case, the aqueous solution of the cyanide-free metal salt and / or the aqueous solution of the metal cyanide salt are omitted. Figure 5 The dispersion can be circulated via the mixing element M2. The components for forming the complex containing one or more compounds (1) of the formula (I) - preferably in a mixture of water and organic complexing ligand - can subsequently be added in the mixing element M3 and recirculated to increase the residence time.

[0134] Process temperature

[0135] In a preferred embodiment of the process according to the invention, the process temperature in step i) is between 26° C. and 49° C., preferably between 28° C. and 47° C., particularly preferably between 29° C. and 42° C., very particularly preferably between 30° C. and 40° C. The process temperature here corresponds to Figure 4 A process temperature between 26° C. and 49° C., preferably between 28° C. and 47° C., particularly preferably between 29° C. and 42° C., very particularly preferably between 30° C. and 40° C., brings about a further improvement in the activity of the DMC catalyst.

[0136] Step (ii)

[0137] In a preferred embodiment of the process according to the invention, in a second step (ii), solids are separated off from the dispersion obtained from (i).

[0138] Here, the solid, ie the precursor of the catalyst according to the invention, is separated from the dispersion by known techniques, such as centrifugation or filtration.

[0139] Suitable filtering devices are described, for example, in “Ullmann's Encyclopedia of Industrial Chemistry”, Volume B 2, Chapters 9 and 10, VCH, Weinheim, 1988 and in H. Gasper, D. Oechsle, E. Pongratz (eds.): “Handbuch derindustriellen Fest / Flüssig-Filtration”, Wiley-VCH Verlag GmbH, Weinheim, 2000.

[0140] The pressure gradient required for filtration can be applied here by gravity, by centrifugal force (eg filter centrifuge), preferably by gas pressure difference (eg vacuum filter or pressure filter) or by liquid pressure (eg filter press, drum or disk filter, and possibly cross-flow filtration modules).

[0141] To separate the catalyst, discontinuous as well as continuously operating filtration devices can be used. Examples of discontinuously operating filtration devices are scraper discharge centrifuges and bag filter centrifuges, membrane, box, frame or tube filter presses, automatic filter presses, automatic pressing devices, platen, cartridge and plate filters and vacuum and pressure suction filters. Examples of continuously operating filtration devices are belt filter presses, pressure and vacuum drum filters, pressure and vacuum disk filters, belt filters and cross-flow filters.

[0142] For filtering the DMC catalyst dispersion, vacuum or pressure filters or vacuum or pressure suction filters are particularly suitable on the laboratory scale; on the pilot and production scale, pressure suction filters, filter presses and automatic filter presses are particularly suitable.

[0143] On the test and pilot scale, membrane filter presses have proven to be particularly suitable. With the aid of suitable filter cloths, preferably membrane cloths, these are able to filter the DMC catalyst dispersions based on an applied liquid pressure gradient.

[0144] The filtration is generally carried out at a temperature of 10 to 80° C. The applied pressure difference can be 0.001 bar to 200 bar, preferably 0.1 bar to 100 bar, particularly preferably 0.1 bar to 25 bar, the applied pressure difference depending on the apparatus used.

[0145] Step (iii)

[0146] The separated solid obtained in step (ii) can be washed by means of redispersion or cake washing.

[0147] In a preferred embodiment of the process according to the invention, in the third step (iii), the separated solid is washed with an aqueous solution of the organic complexing ligand by means of a filter cake washing method.

[0148] The filter cake washing is preferably carried out by pulping or preferably by flow-through washing. Here, the washing liquid flows through the filter cake and displaces the liquid previously contained in the filter cake, wherein diffusion effects also come into play. The removal of water from the washed filter cake can be achieved by gas pressure difference, centrifugal force or mechanical pressing, or preferably in a combined manner (removal of water by gas pressure difference followed by mechanical pressing). The pressure for mechanical pressing can in this case be applied mechanically as well as by a membrane.

[0149] By means of filter cake washing, the production process is simplified and thus also accelerated. The preferred ratio of washing liquid to filter cake volume is that amount which achieves a complete exchange of the amount of liquid present in the original filter cake.

[0150] In an alternative preferred embodiment variant of the process according to the invention, the separated solid is subsequently washed in a third process step with an aqueous solution of an organic complexing ligand (for example by redispersion and subsequent re-isolation by filtration or centrifugation). This makes it possible to remove, for example, water-soluble by-products such as potassium chloride from the catalyst according to the invention. The amount of organic complexing ligand in the aqueous washing liquid is preferably 40% to 80% by weight, based on the total solution.

[0151] Optionally, in a third step, a complex-forming component containing one or more compounds (1) of formula (I) is added to the aqueous wash solution, preferably in the range of 0.5% to 5% by weight, based on the total solution.

[0152] It is also advantageous to wash the separated solid more than once. Preferably, in the first washing step (iii-1), washing is carried out with an aqueous solution of an organic complexing ligand (e.g., by redispersion and subsequent separation by filtration or centrifugation), so as to remove, for example, water-soluble byproducts, such as potassium chloride, from the catalyst according to the present invention. It is particularly preferred that the amount of the organic complexing ligand in the aqueous washing liquid is between 40% by weight and 80% by weight based on the total solution of the first washing step. In a further washing step (iii-2), the first washing step is repeated one or more times, preferably 1 to 3 times, or a non-aqueous solution, such as a mixture or solution of a component forming a complex of an organic complexing ligand and a compound (1) containing one or more formula (I) (preferably in the range of 0.5% by weight to 5% by weight based on the total amount of washing liquid of step (iii-2)) is used as a washing liquid, and the solid is washed with it one or more times, preferably 1 to 3 times.

[0153] Step (iv)

[0154] In a preferred embodiment of the process according to the invention, in the fourth step (iv), the solid obtained is subsequently dried.

[0155] Here, the separated and optionally washed solid, optionally after comminution, is subsequently dried at temperatures of generally 20 to 100° C. and pressures of generally 0.1 mbar to standard pressure (1013 mbar).

[0156] Steps (ii) and (iii)

[0157] In a preferred embodiment of the process according to the invention, steps (ii) and (iii) are carried out in a filter press.

[0158] It has proven to be advantageous to squeeze the washed filter cake after the filter cake washing at a pressure of 0.5 to 200 bar, preferably at the highest possible pressure. This can be done, for example, directly after the filter cake washing in a filter press or by means of other suitable pressing devices which are able to exert mechanical pressure so that liquid present in the filter cake can escape through a membrane or a suitable filter cloth. The mechanical removal of water from the filter cake after the filter cake washing and preferably before drying can preferably be carried out in a filter press, preferably by mechanical squeezing by means of pressure applied to the membrane. The mechanical removal of water preferably results in the washing liquid being removed from the filter cake as substantially as possible.

[0159] Steps (ii), (iii) and (iv)

[0160] The DMC catalyst is subsequently dried at a temperature of about 20 to 100° C. and a pressure of about 0.1 mbar to standard pressure (1013 mbar). Contact dryers and convection dryers as well as spray dryers are suitable for this. Drying is preferably also carried out directly in an apparatus for mechanically separating off the liquid, if these are suitable for this (e.g. suction dryers, centrifugal dryers, “hot filter presses”).

[0161] In a particularly preferred embodiment of the process according to the invention, steps (ii), (iii) and (iv) are carried out in a heatable filter press.

[0162] The method preferably uses a heatable filter press. This is designed as a conventional filter press with a membrane package. In terms of design, the membrane plates used differ from conventional membrane plates in that the heating medium can flow through the space behind the membrane. Preferably, a liquid-tight (so-called "drip-proof" or "air-tight") membrane filter plate is used.

[0163] The heated heating medium flows through the filter cake on the rear side of the filter press membrane, which is completely separated from the filter cake by the filter press membrane and the filter medium, and heats the filter cake in the process. The pressurized medium is under a sufficiently high pressure in this case to ensure that the membrane is in contact with the filter cake. The filter cake can be heated on one or both sides. In view of the drying time, heating on both sides is advantageous.

[0164] A vacuum is applied on the filtrate side to assist the drying process. This vacuum can be generated, for example, by a liquid ring pump. The sucked-off vapor stream is cooled upstream of the vacuum pump to condense out volatile components (e.g. tert-butyl alcohol and water). The variables measured and controlled are the condensation amount, the pressure in the filtrate system of the press and the filter cake temperature.

[0165] In the process, the membrane press pressure is preferably 0.1 bar to 10 bar. The temperature of the pressurized and heated medium is 30° C. to 80° C., preferably 40° C. to 60° C. The filtrate side pressure is preferably less than 100 mbar. A sufficiently high flow rate of the heating medium should be selected for good heat transfer between the heating medium and the product. The drying time is generally a few minutes to a few hours, generally 1 to 10 hours. Residual moisture contents below the target value of about 5% are reliably achieved with this type of drying.

[0166] In a further process step, the product thus separated and freed from secondary components can be ground and packaged.

[0167] Product by process claims

[0168] The present invention further provides a DMC catalyst prepared by the process according to the invention.

[0169] The present invention further provides for the use of the DMC catalysts prepared by the process according to the invention in a process for preparing polyoxyalkylene polyols, preferably polyether polyols by addition polymerization of alkylene oxides onto starter compounds having active hydrogen atoms and / or polyether carbonate polyols by addition polymerization of alkylene oxides onto starter compounds having active hydrogen atoms in the presence of carbon dioxide.

[0170] Due to their extremely high activity, the DMC catalysts prepared by the process according to the invention can generally be used at extremely low concentrations (25 ppm and lower, based on the amount of polyoxyalkylene polyol, preferably polyether polyol to be prepared). If the polyoxyalkylene polyol, preferably polyether polyol, prepared in the presence of the DMC catalyst prepared by the process according to the invention is used for the preparation of polyurethanes, the removal of the catalyst from the polyoxyalkylene polyol, preferably polyether polyol, can be omitted without adversely affecting the product quality of the resulting polyurethane. Example

[0171] The OH number was determined according to the procedure of DIN 53240. The viscosity was determined according to the procedure of DIN 53018 by means of a rotational viscometer (Physica MCR 51, manufacturer: Anton Paar).

[0172] Preparation of DMC catalyst:

[0173] Embodiment 1 (comparison):

[0174] Using the method according to WO 01 / 39883 A1 Figure 4 The catalyst is prepared by using a device.

[0175] In the case of a composition containing the Figure 2 In a loop reactor with a jet disperser having one hole (diameter 0.7 mm) at 35°C (in WO 01 / 39883 A1 Figure 4 A solution of 258 g of zinc chloride in 937 g of distilled water and 135 g of tert-butanol was circulated in the container D2 in the reactor (measured in the reactor in the reactor). A solution of 26 g of potassium hexacyanocobaltate in 332 g of distilled water was metered in. The pressure drop in the jet disperser was 2.9 bar. Subsequently, the dispersion formed was circulated for 60 minutes at 35° C. and a pressure drop in the jet disperser of 2.9 bar. Thereafter, a mixture of 5.7 g of tert-butanol, 159 g of distilled water and 27.6 g of polypropylene glycol 1000 (PPG-1000) was metered in, and the dispersion was then circulated for 80 minutes at 35° C. and a pressure drop in the jet disperser of 2.9 bar.

[0176] 230 g of the resulting dispersion was placed in a 20 cm 3The mixture was filtered through a pressure suction filter with a filter area of ​​1000 g and then washed with a mixture of 82 g tert-butyl alcohol, 42.3 g distilled water and 1.7 g polypropylene glycol 1000. The washed filter cake was mechanically squeezed between two strips of filter paper and finally dried at 60° C. under a high vacuum of about 0.05 bar (absolute) for 2 hours.

[0177] Embodiment 2:

[0178] Example 2 was carried out analogously to Example 1 (comparative), except that in the corresponding preparation steps, tri-sec-butylphenol ethoxylate ( Sapogenat T130) replaces polypropylene glycol 1000 (PPG-1000).

[0179] Embodiment 3:

[0180] Example 3 was carried out analogously to Example 1 (comparative), except that in the corresponding preparation steps, tri-sec-butylphenol ethoxylate ( Sapogenat T180) replaces polypropylene glycol 1000 (PPG-1000).

[0181] Embodiment 4:

[0182] Example 4 was carried out analogously to Example 1 (comparative), except that in the corresponding preparation steps, tri-sec-butylphenol ethoxylate ( Sapogenat T500) instead of polypropylene glycol 1000 (PPG-1000).

[0183] Catalyst Test ("8K Diol Stress Test"):

[0184] DMC catalysts are tested in the so-called "8K diol stress test". Starting from a difunctional polypropylene glycol starter with an OH number of 147 mg KOH / g ("Arcol Polyol 725" from Covestro), a polypropylene glycol ("8K diol") with a calculated OH number of 14 mg KOH / g, i.e. a molecular weight of 8000 g / mol, is prepared with a short propylene oxide metering time (30 minutes). The decisive criterion for the quality / activity of the catalyst in this test is the viscosity of the resulting polyol, wherein DMC catalysts with increased quality / activity lead to lower 8K diol viscosities.

[0185] General implementation:

[0186] A 1-liter stainless steel reactor was initially charged with 75 g of a difunctional polypropylene glycol starter (OH value = 147 mg KOH / g) and 30.7 mg of a DMC catalyst. After 5 nitrogen / vacuum exchanges between 0.1 and 3.0 bar (absolute), the reactor contents were heated to 130° C. under stirring (800 rpm). The mixture was then stripped with nitrogen at 130° C. and 100 mbar (absolute) for 30 minutes. 7.5 g of propylene oxide were then added at 130° C. and 100 mbar (absolute) to activate the catalyst. Catalyst activation was manifested as an accelerated pressure drop in the reactor. After the catalyst had been activated, the remaining propylene oxide (685.7 g) was metered in over 30 minutes at 130° C. under stirring (800 rpm). After a post-reaction time of 30 minutes at 130° C., the volatile components were distilled off at 90° C. under vacuum (<10 mbar) for 30 minutes. The product was then cooled to room temperature and removed from the reactor.

[0187] The OH number and viscosity (25° C.) of the obtained product were measured. In case the measured OH number deviated from the calculated OH number (14 mg KOH / g), the “corrected viscosity” was determined from the measured viscosity using the following formula:

[0188] Corrected viscosity (25°C) = measured viscosity (25°C) + 659*(OH value – 14)

[0189] The results of the catalyst testing in the "8K Diol Stress Test" are summarized in Table 1.

[0190] Table 1:

[0191]

[0192]

[0193] The results show that in the "8K Diol Stress Test" as a semi-batch polyol preparation method, the DMC catalyst prepared using tri-sec-butylphenol ethoxylate as the complex forming component gives lower polyol viscosity values ​​than the DMC catalyst using polypropylene glycol 1000 as the complex forming component.

[0194] Catalyst Testing (Continuous Method):

[0195] The available reactor volume V was charged with a polyether polyol (OH functionality = 2.82; OH value = 48 mg KOH / g; propylene oxide / ethylene oxide ratio = 89.5 / 10.5; containing 25 ppm DMC catalyst). R. The following components were metered into a 1.951 liter, continuously operated stainless steel pressure reactor at 130° C. with stirring (800 rpm):

[0196] -817.50 g / h of propylene oxide

[0197] -95.51 g / h of ethylene oxide

[0198] -21.69 g / h of glycerol

[0199] - 3.83 g / h of a dispersion of 0.00613 g of DMC catalyst in 1 g of propylene glycol

[0200] The reaction mixture is continuously withdrawn from the pressure reactor, wherein the reactor is always completely filled with liquid, so that the reaction volume V corresponds to the reactor volume V R The reaction was completed by continuously transferring the removed reaction mixture into an afterreactor (a tubular reactor with an internal volume of 1.0 L) which was thermostated to 100° C. After leaving the afterreactor, the resulting product was cooled to room temperature and then subjected to analytical checks. Table 2 shows the analytical values ​​of the samples extracted after a total reaction time corresponding to 12 residence times.

[0201] Measure the OH value and viscosity (25°C). In case the measured OH value deviates from the calculated OH value (48 mg KOH / g), the "corrected viscosity" is determined from the measured viscosity using the following formula:

[0202] Corrected viscosity (25°C) = measured viscosity (25°C) + 13*(OHN–48)

[0203] Table 2:

[0204]

[0205]

[0206] The results show that even in a continuous polyol preparation process, DMC catalysts prepared using tri-sec-butylphenol ethoxylate as a complex forming component give lower polyol viscosity values ​​than DMC catalysts using polypropylene glycol 1000 as a complex forming component.

Claims

1. A method for preparing a double metal cyanide catalyst (DMC), comprising i) reacting an aqueous solution of a cyanide-free metal salt, an aqueous solution of a metal cyanide salt, an organic complexing ligand and a complex-forming component, characterized in that The complex-forming components contain one or more compounds (1) of formula (I): R1-O-(R2-O) n -H(I) in R1 is a substituted or unsubstituted aryl group, R2 is an alkylene group, preferably an ethylene group or an isopropylene group, particularly preferably an ethylene group (Et), and n≧1, preferably 5≦n≦80, particularly preferably 7≦n≦70, very particularly preferably 8≦n≦60.

2. The method according to claim 1, wherein R1 has a structure according to formula (II): in R3, R4, R5, R6, R7 are independently selected from hydrogen, straight-chain or branched alkyl groups having 1 to 22 carbon atoms, alicyclic groups having 3 to 22 carbon atoms, and substituted or unsubstituted aryl groups having 6 to 16 carbon atoms, Among them, preferably R3, R5, R7 are independently selected from hydrogen, straight-chain or branched alkyl groups having 1 to 22 carbon atoms, alicyclic groups having 3 to 22 carbon atoms, and substituted or unsubstituted aryl groups having 6 to 16 carbon atoms, and R4 and R6 are hydrogen.

3. The method according to claim 1 or 2, wherein: R3, R5, R7 are independently selected from linear or branched alkyl groups having 1 to 10 carbon atoms and substituted or unsubstituted aryl groups having 6 to 12 carbon atoms, and R4 and R6 are hydrogen.

4. The method according to any one of claims 1 to 3, wherein R1 has a structure according to formula (III), (IV) or (V):

5. The method according to any one of claims 1 to 4, wherein the compound (1) has a structure according to formula (VI), (VII) and / or (VIII): Among them, n≥1, preferably 5≤n≤80, particularly preferably 7≤n≤70, and most preferably 8≤n≤60.

6. The process according to any one of claims 1 to 5, wherein the DMC catalyst comprises a double metal cyanide compound of formula (XIV) M x [M' x ,(CN) y ] z (XIV), and M is selected from the group consisting of Zn(II), Fe(II), Ni(II), Mn(II), Co(II), Sr(II), Sn(II), Pb(II) and Cu(II), preferably one or more metal cations selected from the group consisting of Zn(II), Fe(II), Co(II) and Ni(II), and M' is selected from one or more metal cations of 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), preferably Co(III), Fe(III), Cr(III) and Ir(III), and x, x', y and z are integers and are selected to ensure the electron neutrality of the double metal cyanide compound, wherein preferably, x=3, x'=1, y=6 and z=2.

7. The method according to any one of claims 1 to 6, wherein the double metal cyanide compound is one or more compounds selected from zinc hexacyanocobaltate (III), zinc hexacyanoiridate (III), zinc hexacyanoferrate (III) and cobalt (II) hexacyanocobaltate (III), preferably zinc hexacyanocobaltate (III).

8. The method according to any one of claims 1 to 7, wherein the metal cyanide salt is one or more compounds selected from potassium hexacyanocobaltate (III), potassium hexacyanoferrate (II), potassium hexacyanoferrate (III), calcium hexacyanocobaltate (III) and lithium hexacyanocobaltate (III).

9. according to the method described in any one of claims 1 to 8, wherein the organic complexing ligand is one or more compounds selected from dimethoxyethane, the tert-butyl alcohol, 2-methyl-3-butene-2-ol, 2-methyl-3-butyn-2-ol, ethylene glycol mono-tert-butyl ether and 3-methyl-3-oxetanedemethanol, preferably the tert-butyl alcohol.

10. The method according to any one of claims 1 to 9, wherein the complex-forming components further contain a compound (2), wherein the compound (2) is a polyether, preferably a polyether polyol.

11. The method according to claim 10, wherein the molar ratio of compound (1) to compound (2) is 50:1 to 1:50, preferably 20:1 to 1:

20.

12. The process according to any one of claims 1 to 11, wherein the reaction in step i) is carried out using a mixing nozzle, preferably a jet disperser.

13. The process according to claim 1 , wherein the process temperature of the dispersion during the reaction in step i) is between 26° C. and 49° C., preferably between 28° C. and 47° C., particularly preferably between 29° C. and 42° C., very particularly preferably between 30° C. and 40° C.

14. Double metal cyanide catalyst (DMC) obtainable according to any one of claims 1 to 13.

15. Use of the double metal cyanide catalyst (DMC) according to claim 14 for preparing polyoxyalkylene polyols, preferably polyether polyols and / or polyether carbonate polyols.

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