In U.S. Patent 7,645,717, Dow Global Technologies, Inc. (Midland, MI) reveals nano-scale DMC catalyst complexes that are highly active alkylene oxide polymerization catalysts. They show a greatly improved ability to catalyze the formation of ethylene oxide (EO)-capping onto secondary hydroxyl-terminated polyethers. The catalysts can be prepared by precipitation in the dispersed adequous phase of a water-in-oil emulsion.
Dow inventors Sandeep S. Dhingra, Karla F. Mabe and Keith Jeffrey Watson developed the methods for making metal cyanide catalyst complexes and to methods for polymerizing alkylene oxides in the presence of a metal cyanide catalyst.
Polyethers are prepared in large commercial quantities through the polymerization of alkylene oxides such as propylene oxide and ethylene oxide. This polymerization reaction is usually conducted in the presence of an initiator compound and a catalyst. The initiator compound usually determines the functionality (number of hydroxyl groups per molecule of the polymer) and in some instances imparts some desired functionality. The catalyst is used to provide an economical rate of polymerization.
Metal cyanide complexes are becoming increasingly important alkylene oxide polymerization catalysts. These complexes are often referred to as "double metal cyanide" or "DMC" catalysts. A shortcoming of conventional DMC catalysts is their inability to efficiently polymerize poly(ethylene oxide) end-caps onto poly(propylene oxide) polyols to form polyols terminated with primary hydroxyl groups.
Metal cyanide complexes are becoming increasingly important alkylene oxide polymerization catalysts. These complexes are often referred to as "double metal cyanide" or "DMC" catalysts. A shortcoming of conventional DMC catalysts is their inability to efficiently polymerize poly(ethylene oxide) end-caps onto poly(propylene oxide) polyols to form polyols terminated with primary hydroxyl groups.
Dow provides a DMC catalyst that more efficiently catalyzes the EO-capping reaction. The DMC catalyst efficiently polymerizes propylene oxide, as well.
The metal cyanide catalyst in the form of particles having an average particle size, as determined by transmission electron spectroscopy, of from about 20 to about 500 nm.
The process for making a metal cyanide catalyst includes (A) forming an emulsion having a plurality of water droplets dispersed in an immiscible continuous phase, wherein the water droplets contain a transition metal cyanide compound and a metal salt that reacts with the transition metal cyanide compound to form a water-insoluble metal cyanide catalyst, and (B) subjecting the emulsion to conditions such that the transition metal cyanide compound and the metal salt react in the water droplets to form the water-soluble metal cyanide catalyst.
The metal cyanide catalyst in the form of particles having an average particle size, as determined by transmission electron spectroscopy, of from about 20 to about 500 nm.
The process for making a metal cyanide catalyst includes (A) forming an emulsion having a plurality of water droplets dispersed in an immiscible continuous phase, wherein the water droplets contain a transition metal cyanide compound and a metal salt that reacts with the transition metal cyanide compound to form a water-insoluble metal cyanide catalyst, and (B) subjecting the emulsion to conditions such that the transition metal cyanide compound and the metal salt react in the water droplets to form the water-soluble metal cyanide catalyst.
