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
2002-05-14
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
06388048
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 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 an. In addition, not all of those possible combinations of M, M
1
, X, L, r and t provide very low unsaturation poly(propylene oxide) polymers. Recently, developmental and commercial efforts have focused almost exclusively on zinc hexacyanocobaltate, together with a specific complexing agent, t-butanol.
Zinc hexacyanocobaltate (together with the proper complexing agent and a quantity of a poly(propylene oxide)) has the advantages of being active and of not significantly catalyzing the propylene oxide isomerization reaction. Because of the activity of this catalyst, it can be used in such small amounts that it is less expensive to replace the catalyst than to recover it from the product polyether. As a result, finishing operations can be avoided, thereby reducing the overall production cost. However, as the catalyst is often left in the product, it must be replaced, Thus, it would be desirable to reduce the cost of the catalyst as much as possible consistent with obtaining efficient polymerizations and desirable products.
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 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 [hexacyanocobaltate cobalthexanitrite nitroferricyanide] catalyst complexed with one or more organic complexing agents, wherein (a) the metal is any that forms a water-insoluble precipitate with hexacyanocobaltate, cobalthexanitrite and nitroferricyanide groups, (b) the molar ratio of hexacyanocobaltate to cobalthexanitrite groups is about 1:0.1-1.0, (c) the molar ratio of hexacyanocobaltate to nitroferricyanide groups is from about 1:0.1-1, and (d) the molar ratio of hexacyanocobaltate groups to cobalthexanitrite and nitroferricyanide groups combined is about 1:0.5-1.5.
In another aspect, this invention is an improvement in a process for polymerizing an epoxide compound in the presence of a catalyst. In the improved process, the catalyst is a metal hexacyanocobaltate cobalthexanitrite nitro-ferricyanide complexed with one or more organic complexing agents, said metal being any that forms a water-insoluble precipitate with hexacyanocobaltate, cobalthexanitrite and nitroferricyanide groups.
In a third aspect, this invention is a method of making an active polymerization catalyst, comprising (a) forming a first solution of water soluble hexacyanocobaltate, cobalthexanitrite and nitroferricyanide compounds, said hexacyanocobaltate, cobalthexanitrite and nitroferricyanide compounds being present in proportions such that said solution contains a molar ratio of hexacyanocobaltate to cobalthexanitrite ions of about 1:0.1-1, a molar ratio of hexacyanocobaltate to nitroferricyanitie ions of about 1:0.1-1, and a molar ratio of hexacyanocobaltate groups to cobalthexanitrite and nitroferricyanide groups combined of about 1:0.5-1.5, (b) mixing said first solution with a second solution of a water soluble salt of a metal that forms a water-insoluble precipitate with hexacyanocobaltate, cobalthexanitrite and nitroferricyanide groups so as to precipitate a metal hexacyanocobaltate cobalthexanitrite nitroferricyanide, and (c) either simultaneously with or after step (b), contacting said metal hexacyanocobaltate cobalthexanitrite nitroferricyanide 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 hexacyanocobaltate cobalthexanitrite nitroferricyanide complex of the invention has excellent activity as an epoxide polymerization catalyst. Because some of the expensive hexacyanocobaltate starting materials of conventional DMC catalysts are replaced with cobalthexanitrite and nitro
Flagler Kendra L.
Gulotty, Jr. Robert J.
Laycock David E.
Lovering Richard D.
The Dow Chemical Company
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