Double metal cyanide catalysts for producing polyether polyols

Details Double metal cyanide catalysts for producing polyether polyols Double metal cyanide catalysts for producing polyether polyols

2000-09-06

2001-09-18

Richter, Johann (Department: 1621)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Organic compound containing

C502S156000, C502S159000

Reexamination Certificate

active

06291388

ABSTRACT:

The invention relates to new, improved double metal cyanide (DMC) catalysts for preparing polyetherpolyols by the 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 polyetherpolyols has the particular effect of reducing the proportion of monofunctional polyethers with terminal double bonds, so-called monools, as compared with the conventional method for preparation of polyetherpolyols by means of alkali metal catalysts, such as alkali metal hydroxides. The polyetherpolyols obtained in this way may be processed to produce high quality polyurethanes (e.g. elastomers, foams, coatings). DMC catalysts are usually obtained by reacting an aqueous solution of a metal salt with the aqueous solution of a metal cyanide salt in the presence of a low molecular weight organic coordination ligand, e.g. an ether. In a typical catalyst preparation, for example, aqueous solutions of zinc chloride (in excess) and potassium hexacyanocobaltate are mixed and then dimethoxyethane (glyme) is added to the suspension which is formed. After filtering and washing the catalyst with aqueous glyme solution, an active catalyst of the general formula
Zn
3
[Co(CN)
6
]
2
.xZnCl
2
.yH
2
O.z glyme
is obtained (see e.g. EP 700 949).
U.S. Pat. No. 5,482,908, U.S. Pat. No. 5,536,883 and EP 700 949 disclose improved DMC catalysts which contain a polyether with a number average molecular weight greater than 500, in addition to the double metal cyanide compound and the organic coordination ligand. The improved DMC catalysts have exceptionally high activity and enable the preparation of polyetherpolyols with the addition of very small amounts of catalyst (25 ppm: see example 8 in EP 700 949). The highly active DMC catalyst formulations described in U.S. Pat. No. 5,482,908, U.S. Pat. No. 5,536,883 and EP 700 949 preferably contain polyetherpolyols with hydroxy-functionalities of 2 to 8 as polyethers. Polyetherpolyols suitable for use in the improved DMC catalysts are poly(oxypropylene)polyols, EO-terminated poly(oxypropylene)polyols, mixed EO/PO-polyols, butylene oxide polymers, butylene oxide copolymers with ethylene oxide and/or propylene oxide and poly(tetramethylene-ether) glycols. Poly(oxypropylene)-polyols are particularly preferred (see page 4, lines 8-12 in EP 700 949, column 4, lines 26-34 in U.S. Pat. No. 5,482,908 and column 4, lines 32-40 in U.S. Pat. No. 5,536,883). On the other hand, polyethyleneglycols, i.e. pure ethylene oxide polyetherpolyols are generally referred to as unsuitable for preparing improved, highly active DMC catalysts (see page 4, lines 10-11 in EP 700 949, column 4, lines 31-32 in U.S. Pat. No. 5,482,908 and column 4, lines 37-38 in U.S. Pat. No. 5,536,883).
U.S. Pat. No. 5,627,120 and WO 97/40086 disclose further highly active DMC catalysts which contain a polyether with a number average molecular weight of less than 500, in addition to the double metal cyanide compound and the organic coordination ligand. Interestingly, polyethylene glycols with a number average molecular weight of less than 500 are also particularly preferred for preparing the DMC catalysts described in U.S. Pat. No. 5,627,120 and WO 97/40086 (see column 3, lines 57-60 in U.S. Pat. No. 5,627,120 and page 7, lines 8-10 in WO 97/40086).
The object of the present invention is now to provide further improved DMC catalysts for use in the polyaddition of alkylene oxides to appropriate starter compounds and which have clearly increased catalyst activity when compared with the types of catalysts known hitherto. Ideally, the catalyst may then be used at such a low concentration (15 ppm or less), due to the increased activity, that otherwise costly catalyst separation processes are no longer required and the product can be used directly for polyurethane applications.
Surprisingly, it has now been found that DMC catalysts which contain a double metal cyanide compound, an organic coordination ligand and 5 to 80 wt. %, with respect to the amount of DMC catalyst, of an ethylene oxide polyether with a number average molecular weight greater than 500, have a greatly increased activity for the polyaddition of alkylene oxides to starter compounds containing active hydrogen atoms and therefore enable the preparation of polyetherpolyols at very low catalyst concentrations (15 ppm or less).
The present invention therefore provides new, improved, double metal cyanide (DMC) catalysts comprising
a) a double metal cyanide compound and
b) an organic coordination ligand,
which are characterised in that they contain 5 to 80 wt. %, with respect to the amount of final catalyst, of an ethylene oxide polyether with a number average molecular weight greater than 500.
The catalysts according to the invention may also optionally contain a further
1
to 10 wt. % of water and/or 5 to 25 wt. % of water-soluble metal salt from preparation of the double metal cyanide.
Double metal cyanide compounds a) which arc suitable for catalysts according to the invention arc the reaction products of a water-soluble metal salt and a water-soluble metal cyanide salt.
The water-soluble metal salt preferably has the general formula M(X)
n
, wherein M is selected from 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. X is an anion, preferably selected from the group of halides, hydroxides, sulfates, carbonates, cyanates, thiocyanates, isocyanates, isothiocyanates, carboxylates, oxalates and nitrates. n has the value 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) chloride, cobalt(II) thiocyanate, nickel(II) chloride and nickel(II) nitrate. Mixtures of different metal salts may also be used.
The water-soluble metal cyanide salt preferably has the general formula (Y)
a
M′(CN)
b
(A)
c
, wherein 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 metal cyanide 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 the group of halides, hydroxides, sulfates, carbonates, cyanates, thiocyanates, isocyanates, isothiocyanates, carboxylates, oxalates or nitrates. Both a and b are positive integers (≧1), wherein the values for a, b and c are chosen in such a way that the metal cyanide salt does not carry an electrical charge; c preferably has the value 0. Examples of suitable water-soluble metal cyanide salts are potassium hexacyanocobaltate(II), potassium hexacyanoferrate(II), potassium hexacyanoferrate(III), calcium hexacyanocobaltate(II) and lithium hexacyano-cobaltate(III).
Examples of suitable double metal cyanide compounds a) which may bc used in catalysts according to the invention are zinc hexacyanocobaltate(III), zinc hexacyanoferrate(II), zinc hexacyanoferrate(III), nickel(II) hexacyanoferrate(II) and cobalt(II) hexacyanocobaltate(III). Further examples of suitable double metal cyanide compounds are mentioned, for example, in U.S. Pat. No. 5,158,922 (column 8, lines 29-66). Zinc hexacyanocobaltate(III) is preferably used.
DMC catalysts according to the invention contain an organic coordination ligand b), since this may, for example, increase the catalytic activity. Suitable organic coordination ligands are known in principle and are described in detail in the previously cited pri

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