Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-05-09
2002-10-08
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S330800, C525S331400, C528S421000
Reexamination Certificate
active
06462133
ABSTRACT:
BACKGROUND OF THE INVENTION
Alkylene oxides such as ethylene oxide, propylene oxide and 1,2-butylene oxide are polymerized to form a wide variety of polyether products. For example, polyether polyols are prepared in large quantities for polyurethane applications. Other polyethers are used as lubricants, brake fluids, compressor fluids, and many other applications.
These polyethers are commonly prepared by polymerizing one or more alkylene oxides in the presence of an initiator compound and an alkali metal catalyst. The initiator compound is typically a material having one or more hydroxyl, primary or secondary amine, carboxyl or thiol groups. The function of the initiator is to set the nominal functionality (number of hydroxyl groups/molecule) of the product polyether, and in some instances to impart some desired functional group to the product.
Until recently, the catalyst of choice was an alkali metal hydroxide such as potassium hydroxide. Potassium hydroxide has the advantages of being inexpensive, adaptable to the polymerization of various alkylene oxides, and easily recoverable from the product polyether.
However, to a varying degree, alkali metal hydroxides catalyze an isomerization of propylene oxide to form allyl alcohol. Allyl alcohol acts as a monofunctional initiator during the polymerization of propylene oxide. Thus, when potassium hydroxide is used to catalyze propylene oxide polymerizations, the product contains allyl alcohol-initiated, monofunctional impurities. As the molecular weight of the product polyether increases, the isomerization reaction becomes more prevalent. Consequently, poly(propylene oxide) products prepared using KOH as the catalyst at equivalent weights of about 800 or more tend to contain very significant quantities of the monofunctional impurities. This tends to reduce the average functionality and broaden the molecular weight distribution of the product.
More recently, the so-called double metal cyanide (DMC) catalysts have been used commercially as polymerization catalysts for alkylene oxides. These DMC catalysts are described, for example, in U.S. Pat. Nos. 3,278,457, 3,278,458, 3,278,459, 3,404,109, 3,427,256, 3,427,334, 3,427,335 and 5,470,813, among many others. Because these catalysts do not significantly promote the isomerization of propylene oxide, polyethers having low unsaturation values and higher molecular weights can be prepared, compared to potassium hydroxide-catalyzed polymerizations.
Unfortunately, the DMC catalysts have other significant drawbacks. DMC catalysts are difficult to separate from a polyether polyol. As a result, most of the time the catalyst is simply left in the polyol. This requires that the catalyst be continually replaced, which adds to the cost of producing the polyether. In some cases, the DMC catalyst interferes with downstream uses of the polyol, and so cannot be left in the polyol. Perhaps more important is that DMC catalysts are not effective in producing ethylene oxide-capped poly(propylene oxides). These capped polyols represent a significant portion of the demand for polyols for polyurethane applications. As a result, polyol manufacturers using DMC catalysts must in addition conduct separate ethylene oxide-capping processes using in most cases conventional alkali metal hydroxide catalysts.
Even more recently, certain phosphazene and phosphazenium compounds have been mentioned as alkylene oxide polymerization catalysts. See, for example, U.S. Pat. Nos. 5,952,457 and 5,990,352, as well as EPO-A-0 763 555, 0 879 838, 0 897 940, 0 916 686 and 0 950 679. These compounds are reported to provide good polymerization rates and to provide poly(propylene oxide) polymers having low levels of unsaturation. Moreover, these compounds are capable of producing ethylene oxide-capped poly(propylene oxides). However they are quite expensive and difficult to separate from the product polyether. Thus, the polyol manufacturer must either engage in expensive steps to recover the catalyst, or else ship the product with the catalyst still in it. Either option significantly increases the cost of the polyether. Moreover, the strongly basic catalyst interferes with many downstream uses of the polyether.
It would be desirable to provide an alkylene oxide polymerization catalyst that provides good polymerization rates, produces poly(propylene oxide) polymers with low levels of unsaturation, allows for the production of ethylene oxide-capped poly(propylene oxide) polymers, and is inexpensively removed from the product polyol.
SUMMARY OF THE INVENTION
In one aspect, this invention is a cross-linked organic polymer having pendant phosphazene groups including at least two phosphorus atoms or phosphazenium groups including one or more phosphorus atoms.
In another aspect, this invention is a method comprising subjecting an alkylene oxide to polymerization conditions in the presence of an initiator compound and a catalytically effective amount of a crosslinked organic polymer having pendant phosphazene or phosphazenium groups, wherein said crosslinked organic polymer is substantially insoluble in said alkylene oxide and said polyether.
DETAILED DESCRIPTION OF THE INVENTION
In this invention, a crosslinked organic polymer having pendant phosphazene or phosphazenium groups is used as a catalyst for an alkylene oxide polymerization.
By “phosphazene” group, it is meant an uncharged group containing a chain of alternating nitrogen and phosphorus atoms which contains at least two nitrogen atoms in the chain. The phosphazene group will contain at least one —N═P—N— linkage in the chain. It is preferred that the phosphazene group contains at least two phosphorus atoms in the chain. The phosphazene group more preferably has from about 2 to about 6 phosphorus atoms. The chain of nitrogen and phosphorus atoms may be branched. It is most preferred that each phosphorus atom is bound to four nitrogen atoms. Typically, each phosphorus atom will be singly bonded to three nitrogen atoms, and doubly bonded to a fourth nitrogen atom.
A “phosphazenium” group is a corresponding cationic group. With phosphazenium groups, it is preferred that the chain contains from about 1 to about 6 phosphorus atoms. As before, the chain of nitrogen and phosphorus atoms may be branched. It is most preferred that each phosphorus atom is bound to four nitrogen atoms.
Thus, polymers containing phosphazene groups can be represented by the structures
Polymer-[N═P{[—N═P(A
2
)]
x
—NR
2
}
3
]
z
(I)
and
Polymer-{NR
1
—[P(A
2
)═N]
x
—P(A
2
)═NR}
z
(IA)
Similarly, polymers containing phosphazenium groups can be represented by the structures
Polymer-[NR
1
—P
+
{[—N═P(A
2
)]
x
—NR
2
}
3
]
z
(II)
and
Polymer-{NR—[P(A
2
)═N]
x
—P
+
(A
2
)—NRR
1
}
z
(IIA)
In these formulae, each R and R
1
is independently in each occurrence (a) an unsubstituted or inertly substituted alkyl or aryl group, (b) an unsubstituted or inertly substituted alkylene or arylene group that, together with another R or R
1
group on the same nitrogen atom, forms a ring structure including that nitrogen atom, (c) an unsubstituted or inertly substituted alkylene or arylene group that, together with a R or R
1
group bonded to a different nitrogen atom bonded to a common phosphorus atom, forms a ring structure including an —N—P—N— or —N—P═N— moiety, or (d) hydrogen. Each R is preferably a C
1-10
alkyl group, or together with another R forms a C
2-5
alkylene group that forms part of a ring structure with a nitrogen atom or an —N—P—N— or —N—P═N— moiety. Each R
1
is preferably hydrogen, methyl, ethyl, n-propyl or isopropyl, or together with another R forms a C
2-5
alkylene group that forms part of a ring structure with a nitrogen atom or an —N—P—N— or —N—P═N— moiety. Each A is independently —[N═P(A
2
)]
x
—NR
2
, where R is as before. Each x is independently zero or a positive integer. The values
Dow Global Technologies Inc.
Sellers Robert E. L.
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