Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-04-24
2003-11-04
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S618000, C568S619000, C568S620000
Reexamination Certificate
active
06642423
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to processes for preparing poly(oxyethylene) polymers and to methods for preparing same.
Polymers of ethylene oxide are well known and useful in a number of applications such as 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. These polymers may have no more than one oxyethylene group in succession, or be a higher molecular weight polymer containing one or more long chains of consecutive oxyethylene groups.
Poly(oxyethylene) polymers are commonly made through an anionic polymerization process, whereby ethylene oxide is combined with an initiator compound and a strongly basic catalyst such as potassium hydroxide or certain organic amines. The initiator compound contains one or more oxyalkylatable groups such as hydroxyl, thiol, carboxylic acid and the like. The initiator compound determines the functionality (i.e., number of hydroxyl groups/molecule of product) and in some cases may introduce some desired functional group into the product.
There are some disadvantages of polymerizing ethylene oxide using these strongly basic catalysts. One problem is that the strongly basic catalysts do not produce a low polydispersity product when a tertiary hydroxyl initiator compound is used. In addition, the basic catalyst usually must be removed from the product before it is used, which increases manufacturing costs. In addition, some kinds of initiator compounds cannot be ethoxylated using strongly basic catalysts because they contain base-sensitive functional groups.
In order to ethoxylate certain types of initiators that are sensitive to alkali and alkaline earth bases, Lewis acids such as boron trifluoride-diethyl etherate and organic amines such as triethylamine have been tried. However, some of these catalysts tend to promote the formation of large amounts of by-products, especially when it is attempted to add three or more moles of ethylene oxide per equivalent of initiator compound. The Lewis acid catalysts tend to catalyze “back-biting” reactions where the growing polymer chain reacts with itself to form cyclic ethers such as dioxane and various crown ethers. These cannot be removed easily from the desired product, and so the product cannot be used in many applications.
So-called double metal cyanide (“DMC”) catalysts have been used in alkoxylation reactions to make polyols and polyesterethers. These catalysts are mainly of interest in polymerizing propylene oxide. This is because propylene oxide readily undergoes a rearrangement reaction in the presence of strong bases. The rearrangement reaction occurs at rates that approach or even exceed that of the desired propoxylation reaction. The practical result of this is that it is very difficult to prepare polypropylene oxide) polymers of above about 3000 equivalent weight in an anionic polymerization catalyzed with a strong base. Lower equivalent weight poly(propylene oxide) polymers can be made using strongly basic catalysts, but contain significant quantities of monofunctional impurities. Thus, DMC catalysis has focussed on polymerizing propylene oxide. In some cases, random copolymers of propylene oxide and ethylene oxide have been made with DMC catalysts by polymerizing mixtures of ethylene oxide and propylene oxide.
Poly(propylene oxide) polymers that are end-capped with poly(oxyethylene) blocks are important raw materials for making polyurethanes. Attempts have been made to produce these using DMC catalysts, and in particular to form the poly(oxyethylene) blocks through a DMC-catalyzed polymerization of ethylene oxide. These attempts have not been successful. Instead of forming terminal poly(oxyethylene) blocks on the polyol, the ethylene oxide instead mostly goes into forming a very high molecular weight poly(ethylene oxide) homopolymer. So, end-capping capping with polyethylene oxide is usually performed using a basic catalyst such as potassium hydroxide, although in some instances the DMC catalyst may also be present.
SUMMARY OF THE INVENTION
This invention is a process for preparing a polyether, comprising forming a mixture of an initiator compound having one or more oxyalkalatable groups, ethylene oxide and a metal cyanide catalyst complex, and subjecting the mixture to conditions sufficient to ethoxylate the oxyalkalatable groups of the initiator.
This invention permits the formation of initiated polymers of ethylene oxide. Surprisingly, the ethoxylation of initiator compounds proceeds well using a metal cyanide catalyst complex without forming large quantities of high molecular weight poly(ethylene oxide). Further, this invention permits the formation of several new classes of polyethoxylated initiator compounds that could not be made in good yield using strongly basic or Lewis acid type catalysts.
DETAILED DESCRIPTION OF THE INVENTION
In this invention, an initiator compound is ethoxylated by reaction with ethylene oxide in the presence of a catalytically effective amount of a metal cyanide catalyst. The ethoxylation is conducted by combining the initiator, metal cyanide catalyst and ethylene oxide and subjecting the mixture to conditions sufficient to polymerize the ethylene oxide. In this manner, the initiator compound becomes ethoxylated until poly(oxyethylene) chains of a desired length are produced. As discussed below, once polymerization has begun, other alkylene oxides can be polymerized and other types of monomers that are copolymerizable with alkylene oxides can be polymerized as well.
In most cases, a so-called “induction period” occurs at the beginning of the polymerization reaction, in which little or no polymerization occurs. Under ethylene oxide polymerization conditions, this is manifested by a period during which reactor pressure remains constant or decreases only slowly. The induction period may range from a few minutes to several hours, depending on the particular catalyst that is used and the temperature. During this induction period, the catalyst becomes activated and then rapid polymerization of the ethylene oxide commences.
It is believed that activation of the catalyst complex requires that it be exposed to an alkylene oxide. In the ordinary case, where a poly(oxyethylene) homopolymer is to be produced, the catalyst will be activated in the presence of ethylene oxide.
However, it is not necessary to use ethylene oxide to activate the catalyst. Propylene oxide and/or other alkylene oxides can be used if desired to activate the catalyst, at which point ethylene oxide is added to the reaction mixture and polymerized. In such cases, a certain amount of the other alkylene oxide will polymerize onto the initiator compound. It is believed that unless substantially all of the other alkylene oxide is consumed, subsequently added ethylene oxide will polymerize rapidly with little or no additional induction period. On the other hand, if the supply of the other alkylene oxide is exhausted, then a second induction period is often seen when ethylene oxide is added.
The starting mixture of catalyst, initiator compound and alkylene oxide is conveniently made by combining the catalyst and initiator compound in a pressure reactor (or by forming the catalyst in the initiator), and then pressurizing the reactor with an initial quantity of the alkylene oxide used to activate the catalyst. The induction period follows, as indicated by a nearly constant or slowly decreasing pressure in the reactor. The onset of rapid polymerization that follows the induction period is evidenced by a drop in pressure as the initial quantity of alkylene oxide is consumed.
The starting mixture of catalyst, initiator compound and alkylene
Clement Katherine S.
Dianis William P.
Elwell Richard J.
Laycock David E.
Molzahn David C.
Barts Samuel
Dow Global Technologies Inc.
Witherspoon Sikarl A.
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