Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From heterocyclic reactant containing as ring atoms oxygen,...
Reexamination Certificate
2000-05-19
2002-04-23
Lovering, Richard D. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From heterocyclic reactant containing as ring atoms oxygen,...
C502S153000, C502S156000, C528S414000, C528S415000, C568S606000
Reexamination Certificate
active
06376645
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to metal catalysts for alkylene oxide polymerization.
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 incorporate some desired functional group into 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 a propylene oxide polymerization, the product contains allyl alcohol-initiated, monofunctional impurities. As the molecular weight of the product polyether increases, the isomerization reaction becomes more prevalent. Consequently, 800 or higher equivalent weight poly(propylene oxide) products prepared using KOH as the catalyst tend to have 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. Because some of 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 those made with potassium hydroxide.
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. The composition of these catalysts can vary widely, but can generally be represented by the formula
M
b
[M
1
(CN)
r
(X)
t
]
c
.zL.aH
2
O.nM
x
A
y
wherein M is a metal ion that forms an insoluble precipitate with the metal cyanide grouping M
1
(CN)
r
(X)
t
and which has at least one water soluble salt;
M
1
is a transition metal ion;
X represents a group other than cyanide that coordinates with the M
1
ion;
L represents an organic complexing agent;
A represents an anion that forms a water-soluble salt with the M ion;
b and c are numbers that reflect an electrostatically neutral complex;
r is from 4 to 6; t is from 0 to 2; and
z, n and a are positive numbers (which may be fractions) indicating the relative quantities of the complexing agent, water molecules and M
x
A
y
, respectively.
However, experience has shown that most of the possible combinations of M, M
1
, X, L, r and t do not provide a catalyst having sufficient activity to be of commercial interest. Most combinations show virtually no activity at all. In addition, not all of those possible combinations of M, M, X, L, r and t provide very low unsaturation poly(propylene oxide) polymers. Recently, developmental and commercial efforts have focussed almost exclusively on zinc hexacyanocobaltate, together with a specific complexing agent, t-butanol.
As described in U.S. Pat. No. 5,470,813, one disadvantage of DMC catalysts is that they tend to require an induction period of close to an hour to many hours in some cases before becoming active. Little polymerization occurs during this induction period, but it is followed by a strongly exothermic reaction. For some operations, particularly continuous polymerization processes, it would be desirable to reduce this induction period and to provide a less strongly exothermic reaction.
It would be desirable, therefore, to provide an active catalyst for polymerizing alkylene oxides, which is less expensive to prepare than zinc hexacyanocobaltate complexes. It would be even more desirable to provide such a catalyst that exhibits a short induction period before rapidly polymerizing alkylene oxides, and especially desirable if the catalyst provides for a more controlled exotherm when rapid polymerization commences.
SUMMARY OF THE INVENTION
In one aspect, this invention is a metal catalyst represented by the general structure:
M
b
[M
1
(CN)
6
]
c
[M
2
(NO
2
)
6
]
d
.zL.aH
2
O.nM
3
x
A
y
,
wherein M and M
3
are metal ions that form an insoluble precipitate with the M
1
(CN)
6
and M
2
(NO
2
)
6
ions, and which have at least one water soluble salt;
M
1
and M
2
are trivalent transition metal ions;
L represents an organic complexing agent;
A represents an anion that forms a water-soluble salt with the M
3
ion;
b, c and d are numbers that reflect an electrostatically neutral complex, with the ratio of c:d being from about 50:50 to about 99:1; and
z, n and a are positive numbers (which may be fractions) indicating the relative quantities of the complexing agent, water molecules and M
3
x
A
y
, respectively.
In another aspect, this invention is an improvement in a process for polymerizing an epoxide compound, wherein the polymerization is conducted in the presence of the catalyst of the first aspect.
In a third aspect, this invention is a method of making an active polymerization catalyst, comprising
(a) forming a first solution of water soluble hexacyanometarate and hexanitrometallate compounds, said hexacyanometallate and hexanitrometallate compounds being present in proportions such that said solution contains a molar ratio of hexacyanometallate to hexanitrometallate ions of about 50:50 to 99:1.
(b) mixing said first aqueous solution with a second solution of a water soluble salt of a metal that forms a water-insoluble precipitate with hexacyanometallate and hexanitrometallate ions so as to precipitate a metal [hexacyanometallate hexanitrometallate], and
(c) either simultaneously or after step (b), contacting said metal [hexacyanometallate hexanitrometallate] with an organic complexing agent and, if no stoichiometric excess of metal salt is used in step (b), an additional quantity of a metal salt.
It has been found that the metal [hexacyanometallate hexanitrometallate] complex of the invention has excellent activity as an epoxide polymerization catalyst. The complexes, particularly those containing higher levels of hexanitrometallate ion, tend to have very short induction periods. In many cases, they provide a well-controlled exotherm at the start of polymerization. Often, the catalysts provide poly(propylene oxide) polymers with levels of unsaturation below 0.01 meg/q.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst of this invention is a metal hexacyanometallate hexanitrometallate that is complexed with an organic complexing agent. As used herein, “hexacyanometallate” refers to a group having the structure [M
1
(CN)
6
]
3−
, where M
1
is as described before. “Hexanitrometallate” refers to a group having the structure [M
2
(NO
2
)
6
]
3−
, where M
2
is as described before. M
1
and M
2
are preferably Fe
+3
, Co
+3
, Cr
+3
, Mn
+3
, Ir
+3
and Rh
+3
. Co
+3
and Fe
+3
are even more preferred and Co
+3
is most preferred. M
1
and M
2
may be the same or different, but preferably are both the same and most preferably are both Co
+3
.
The hexacyanometallate and hexanitrometallate groups are present in molar ratios of from about 50:50, prefer
Flagler Kendra L.
Gulotty, Jr. Robert J.
Laycock David E.
Lovering Richard D.
The Dow Chemical Company
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