Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From heterocyclic reactant containing as ring atoms oxygen,...
Reexamination Certificate
2003-03-31
2004-03-30
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From heterocyclic reactant containing as ring atoms oxygen,...
C528S403000, C528S412000, C528S414000, C528S420000, C568S672000, C568S678000, C568S679000, C568S680000
Reexamination Certificate
active
06713599
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved method of forming polymer polyols. More specifically, the present invention relates to an improved method of forming polymer polyols having a narrow molecular weight distribution using double metal cyanide (DMC) catalysts.
BACKGROUND OF THE INVENTION
Polymer polyols are used in large quantities for producing polyurethanes. Several types of polyols, mainly polyether polyols and polyester polyols, but also including polyether carbonate polyols are commonly used in combination with isocyanates, catalysts and other components to form polyurethane polymers. The quality and properties of the polyurethane polymers are directly related to the properties of the polyol being reacted with the isocyanate.
Higher molecular weight polyols are preferably used for the formation of certain polyurethanes such as flexible polyurethane foam and CASE applications. Higher molecular weight polyether polyols are obtained from the reaction of polyol initiators with alkylene oxide monomers in the presence of catalysts. Polyethercarbonate polyols are obtained from the copolymerization reaction of polyol initiators with alkylene oxide monomers and carbon dioxide monomer in the presence of catalysts. One preferred class of catalysts for the formation of polyether polyols and in particular for the formation of polyethercarbonate polyols are double metal cyanide (DMC) catalysts. One problem associated with the formation of polyether polyols using DMC catalysts, is the need to use extremely high purity and high cost DMC catalysts in extremely low catalyst concentrations. High purity DMC catalysts are very expensive and are a significant contribution to manufacturing costs. The extremely low concentrations employed in turn lead to problems with catalyst deactivation and catalyst poisoning during the course of the production process. Another problem associated with the formation of polyether polyols using DMC catalysts, even high quality DMC catalysts, is the formation of unwanted high molecular weight tails, which are small amounts of high molecular weight polyether polymer that severely affect polyurethane foaming and polyurethane foam properties. When polyethercarbonate polyols are produced from the copolymerization reaction of polyol initiators with alkylene oxide monomers and carbon dioxide monomer in the presence of DMC catalysts, the resulting polyethercarbonate polyols typically have a much broader polydispersity than corresponding polyether polyols of comparable molecular weight. Generally polymer polyols with narrow polydispersity are preferred, since broader polydispersity leads to increased polyol viscosity and inferior polyurethane foaming and foam properties.
Several attempts to reduce the high molecular weight tail in polyether polyols have been disclosed. U.S. Pat. Nos. 5,958,944 and 6,083,420 discloses providing an oxyalykyl mixture having essentially pure, higher alkylene oxide during the terminal portion of the polymer formation to limit the growth of the polymer tail. Although the pure, higher alkylene oxide forms no more than about 15 weight percent of the total polyol weight, the desired polyol has been modified to reduce the molecular weight of the polyol tail.
U.S. Pat. No. 6,204,357 discloses a method of preparing polyether polyols where only a small amount of the yield includes a higher molecular weight than desired. The polyether is formed from ethylene oxide that is reacted with primary and secondary initiators in the presence of a double metal cyanide catalyst. The combination of the primary and secondary initiators reduces the amount of high molecular weight tails.
PCT patent publication WO 97/29146 discloses a complex production process involving the continuous addition of starter to achieve reduced levels of high molecular weight tail.
To produce high quality polyurethane foams, it would be desirable to produce a wide range of polyols having a high molecular weight, a narrow polydispersity and a low viscosity while not modifying the characteristics of the polyol.
SUMMARY OF THE INVENTION
In one embodiment, the present invention is a method for forming polyether polyols or polyethercarbonate polyols comprising the steps of: reacting an alkylene oxide or an alkylene oxide and carbon dioxide with an initiator in the presence of a double metal cyanide catalyst, and a sterically hindered chain transfer agent capable of protonating the polyol. The chain transfer agent functions to protonate the end group of the resident growing polymer polyol chain, causing it to leave the DMC catalytic centers so another round of alkylene oxide or carbon dioxide addition can take place with another growing chain.
The use of a chain transfer agent eliminates the need to modify the polyol to reduce the chain tail while still providing the ability to produce a wide range of polyols useful in forming urethanes. The inventive method of forming the polyol increases the chain transfer rate of the reaction to more than the chain growth rate. By balancing these rates in a desirable ratio, the molecular weight distribution of the polyol is optimized without having to modify the polyol.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Polymers of alkylene oxides are well known and useful in a number of applications, including detergent and cleaner compositions, oil well drilling fluids, inks, metal working fluids, lubricants in paper coating compositions, ceramics manufacturing, chemical intermediates for organic nonionic surfactants which in turn are used in cosmetics, textiles and chemical processing, polyurethanes which are used as flexible foams and elastomers, chemical intermediates for esters which are used in textile spin finishes, manufacturing cosmetic agents, and foam control agents for a wide variety of processes.
In the present invention, a unique method of forming a polyether or polyether carbonate polyol is provided. Such polyols, in one context, are reactive with an isocyanate compound to form a polyurethane. Polyurethanes are typically formed from a polyol and an isocyanate. Various polyols result in polyurethanes having various types of properties that may be desirable for a particular function. One polyol may be reactive with an isocyanate to form a thermoplastic polyurethane and another polyol may be reactive to form a flexible foam. Polyols such as polyether polyols, polyether carbonate polyols, and polypropylene carbonate polyols are reactive with an isocyanate to produce polyurethanes known to have different properties.
Polyols are formed by the polymerization of alkylene oxides and initiators. Double metal cyanide (DMC) catalysts are highly active and produce polyether polyols containing only a very low concentration of by-products (unsaturation).When the polymerization reaction is carried out in the presence of CO
2
polyether carbonate polyols are formed.
Double metal cyanide catalysts are used to increase and control the rate of formation of the polyol polymer chain during the formation of a polyol. Double metal cyanide catalysts known to be effective are: zinc hexacyanoferrate (EH), zinc hexacyanoferrate (II), nickel (II) hexacyanoferrate (II), nickel (II) hexacyanoferrate (III), zinc hexacyanoferrate (III) hydrate, cobalt (II) hexacyanoferrate (II), nickel (II) hexacyanoferrate (III) hydrate, ferrous hexacyanoferrate (III), cobalt (II) hexacyano cobaltate (III), zinc hexacyano cobaltate (II), zinc hexacyanomanganate (II), zinc hexacyano chromate (III), zinc iodo pentacyanoferrate (III), cobalt (II) chloropentacyanoferrate (II), cobalt (II) bromopentacyanoferrate (II), iron (II) fluoropentacyanoferrate (II), zinc chlorobromotetracyanoferrate (III), iron (III) hexacyanoferrate (III), aluminum dichlorotetracyanoferrate (III), molybdenum (IV) bromopentacyanoferrate (II), molybdenum (VI) chloropentacyanoferrate (II), vanadium (IV) hexacyanochromate (II), vanadium (V) hexacyanoferrate (III), strontium (II) hexacyanomanganate (III), tungsten (IV) hexacyano vanadate (IV), aluminum chloropentacyano vanadate (V), tungsten (VI) h
Dexheimer Edward Michael
Hinz Werner
Neff Raymond
Wildeson Jacob
Aylward D.
BASF Corporation
Borrego Fernando A.
Dawson Robert
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