Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Reexamination Certificate
2000-05-19
2002-03-19
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
C502S150000, C502S152000, C502S153000, C502S155000, C502S162000, C502S168000, C502S200000, C502S216000, C525S403000, C525S419000, C526S108000, C526S113000, C526S120000, C526S135000, C526S140000, C526S273000, C528S090000, C528S092000, C528S103000
Reexamination Certificate
active
06358877
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 groups 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 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 having equivalent weights of about 800 or more tend to have very significant quantities of the monofunctional impurities when prepared using KOH as the catalyst. 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. Those DMC catalysts that are active usually 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. Recently, developmental and commercial efforts have focused almost exclusively on zinc hexacyanocobaltate, together with a specific completing 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, 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 that exhibits a short induction period before rapidly polymerizing alkylene oxides, and provides for a more controlled exotherm when the rapid polymerization commences.
SUMMARY OF THE INVENTION
In one aspect, this invention is a metal cyanide catalyst complexed with an organic sulfone (R
5
—S(O)
2
—R
5
) or sulfoxide (R
5
—S(O)—R
5
) compound.
In another aspect, this invention is an improvement in a process for polymerizing an epoxide compound in the presence of a catalyst, the improvement wherein the catalyst is a metal cyanide catalyst complexed with an organic sulfone or sulfoxide compound.
It has been found that the metal cyanide catalyst complex of the invention has excellent activity as an epoxide polymerization catalyst. In particular, the catalyst often exhibits sharply reduced induction periods when used in such polymerizations, compared, for example, to the zinc hexacyanocobaltate/t-butanol/poly(propylene oxide) complex that is most commonly used. In addition, smaller, more easily controlled exotherms are usually seen when rapid alkylene oxide polymerization begins.
DETAILED DESCRIPTION OF THE INVENTION
By “metal cyanide catalyst”, it is meant a catalyst represented by the formula
M
b
[M
1
(CN)
r
(X)
t
]
c
[M
2
(X)
6]
d
•zL•aH
2
O•nM
3
x
A
y
wherein
M is a metal ion that forms an insoluble precipitate with the M
1
(CN)
r
(X)
t
group and which has at least one water soluble salt;
M
1
and M
2
are transition metal ions that may be the same or different;
each X independently represents a group other than cyanide that coordinates with an M
1
or M
2
ion;
M
3
x
A
y
represents a water-soluble salt of metal ion M
3
and anion A, wherein M
3
is the same as or different than M;
L represents the organic sulfone or sulfoxide compound;
b and c are positive numbers that, together with d, reflect an electrostatically neutral complex;
d is zero or a positive number;
x and y are numbers that reflect an electrostatically neutral salt;
r is from 4 to 6; t is from 0 to 2; and
a and n are positive numbers (which may be fractions) indicating the relative quantities of water sulfone or sulfoxide compound, and M
3
x
A
y
, respectively.
The X groups in any M
2
(X)
6
do not have to be all the same. The molar ratio of c:d is advantageously from about 100:0 to about 20:80, more preferably from about 100:0 to about 50:50, and even more preferably from about 100:0 to about 80:20.
Similarly, mixtures of two or more different M
1
(CN)
r
(X)
t
groups can be used.
M and M
3
are preferably metal ions selected from the group consisting of Zn
+2
, Fe
+2
, Co
+2
, Ni
+2
, Mo
+4
, Mo
+6
, Al
+3
, V
+4
, V
+5
, Sr
+2
, W
+4
, W
+6
, Mn
+2
, Sn
+2
, Sn
+4
, Pb
+2
, Cu
+2
, La
+3
and Cr
+3
. M and M
3
are more preferably Zn
+2
, Fe
+2
, Co
+2
, Ni
+2
, La
+3
and Cr
+3
. M is most preferably Zn
+2
.
M
1
and M
2
are preferably Fe
+3
, Fe
+2
, Co
+3
, Co
+2
, Cr
+2
, Cr
+3
, Mn
+2
, Mn
+3
, Ir
+3
, Ni
+2
, Rh
+3
, Ru
+2
, V
+4
and V
+5
. Among the foregoing, those in the plus-three oxidation state are more preferred. 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.
Preferred groups X include anions such as halide (especially chloride), hydroxide, sulfate, carbonate, late, thiocyanate, isocyanate, isothiocyanate, C
1-4
carboxylate and nitrite (NO
2−
), and uncharged species such as CO, H
2
O and NO. Particularly preferred groups X are NO, NO
2−
and CO.
r is preferably 5 or 6, most preferably 6 and t is preferably 0 or 1, most preferably 0. In most instances, r+t will equal 6.
Suitable anions A include halides such as chloride and bromide, nitrate, sulfate, carbonate, cyanide, oxalate, thiocyanate, isocyanate, isothiocyanate, perchlorate and C
1-4
carboxylate. Chloride ion is especially preferred.
L represents an organic sulfone or sulfoxide compound. Suitable sulfone compounds are represented by the general formula R
5
—S(O)
2
—R
5
, where each R
5
is unsubstituted or inertly substituted alkyl, cycloalkyl, aryl, or, together with the other R
5
, forms part of a ring structure that includes the sulfur atom of the sulfone (—S(O)
2
—) group. Suitable sulfoxide compounds are represented by the general formula R
5
—S(O)—R
5
, where each R
5
is as just described. In this context, “inertly substituted” means that the group contains no substituent which undesirably reacts with the metal cyanide compound, its precursor compounds (as described below) or an alkylene oxide, or which otherwise undesirably interferes with the polymerization of an alkylene
Flagler Kendra L.
Laycock David E.
The Dow Chemical Company
Wood Elizabeth D.
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