Chemistry of hydrocarbon compounds – Product blend – e.g. – composition – etc. – or blending process... – With nonhydrocarbon additive
Reexamination Certificate
1999-12-14
2001-07-17
Howard, Jacqueline V. (Department: 1764)
Chemistry of hydrocarbon compounds
Product blend, e.g., composition, etc., or blending process...
With nonhydrocarbon additive
C585S003000, C585S004000
Reexamination Certificate
active
06262323
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and compositions for inhibiting the polymerization of vinyl unsaturated monomers, and more particularly relates, in one embodiment, to methods and compositions for inhibiting the polymerization of dienes such as isoprene.
BACKGROUND OF THE INVENTION
It is well known that undesirable and costly polymerization is a significant problem during the manufacturing of various unsaturated monomers, particularly vinyl aromatic compounds, such as reactive dienes, specifically isoprene. In the purification of isoprene, reboilers on the extractive distillation absorber and stripper towers, and other equipment can experience fouling due to the presence of small oligomers (dimers/trimers/tetramers) of isoprene and cyclopentadiene, and large molecular weight free-radical polymers. The free-radical polymers are mixtures of linear and cross-linked isoprene and polymerized dimers.
Many kinds of inhibitors have been used in the past to minimize this problem. For instance, inhibitors such as diethylhydroxylamine, phenyl-p-phenylenediamines, tert-butyl catechol, and phenothiazine have been used to control polymer formation. During the early 1980s, compounds selected from the groups called alkyl-substituted di-nitro-phenols and nitroso-phenols found widespread use in the styrene industry. However, because such compounds also functioned as insecticides or were dangerous to handle, their use has been discouraged by environmental and government agencies.
It would be desirable if a composition and method could be devised to overcome some of the problems of the commercial polymerization inhibitors, and in particular to improve upon the performance of such prior inhibitors.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method and composition to effectively inhibit the polymerization of dienes such as isoprene.
It is another object of the present invention to provide a method and composition to effectively inhibit the polymerization of dienes that is more effective than using antioxidants and antipolymerants independently.
Still another object of the invention is to permit use of a composition to effectively inhibit the polymerization of isoprene that has reduced environmental concerns compared to some previous polymerization inhibitors.
In carrying out these and other objects of the invention, there is provided, in one form, a method for inhibiting the polymerization of a diene involving adding an effective amount thereto of a mixture including at least one phenylenediamine, at least one sterically hindered phenol, and at least one hydroxylamine.
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Chemical Abstract 94:176449, 1981.
Baker Hughes Incorporated
Howard Jacqueline V.
Madan Mossman & Sriram P.C.
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