Chemistry of hydrocarbon compounds – Product blend – e.g. – composition – etc. – or blending process... – With nonhydrocarbon additive
Reexamination Certificate
2000-12-21
2001-09-04
Anthony, Joseph D. (Department: 1714)
Chemistry of hydrocarbon compounds
Product blend, e.g., composition, etc., or blending process...
With nonhydrocarbon additive
C585S020000, C585S024000, C585S428000, C252S182290, C252S405000, C252S407000
Reexamination Certificate
active
06284936
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and compositions for inhibiting the polymerization of vinyl monomers, and more particularly relates, in one embodiment, to methods and compositions for inhibiting the polymerization of vinyl aromatic monomers.
BACKGROUND OF THE INVENTION
It is well known that undesirable and costly polymerization is a significant problem during the manufacturing of various vinyl monomers, particularly vinyl aromatic compounds, such as styrene. 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.
Recently, a new class of compounds called stable free radicals is being investigated to replace the nitrophenol products. Although stable free radicals are effective on monomer polymerization, their current cost makes them unattractive. It would be desirable if a composition and method could be devised to overcome some of the problems in using the stable free radical polymerization 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 vinyl aromatic compounds, such as styrene.
It is another object of the present invention to provide a method and composition to effectively inhibit the polymerization of styrene that is less expensive than using stable free radicals exclusively.
Still another object of the invention is to permit use of a composition to effectively inhibit the polymerization of styrene that has little or no environmental concerns.
In carrying out these and other objects of the invention, there is provided, in one form, a composition for inhibiting polymerization of vinyl aromatic compounds that includes an alkyl-dihydroxyarene, a hydrogen transfer agent, and a stable nitroxide.
DETAILED DESCRIPTION OF THE INVENTION
It has been discovered that the combination of substituted alkyl-dihydroxyarenes, a hydrogen transfer agent, and a stable nitroxide is an effective treatment to control styrene monomer polymerization. This treatment protocol is most effective when formulated in an organic amine, although the composition may find effective use without the organic amine.
It is expected that suitable vinyl aromatic monomers that may be polymerization inhibited by the compositions and methods of this invention include, but are not necessarily limited to styrene, substituted styrene, divinylbenzene, vinyltoluene, vinyl naphthalene, polyvinylbenzenes, and isomers thereof. Preferably, the aromatic monomer is styrene.
Alkl-Dihydroxyarenes
Suitable substituted alkyl-dihydroxyarenes for the polymerization inhibiting composition of the invention may include, but are not necessarily limited to, substituted alkyl-dihydroxybenzenes having the formula:
where R
1
and R
2
are the same or different and are independently selected from the group consisting of hydrogen, straight, branched, and cyclic alkyl groups averaging from about 1 to about 6 carbon atoms, where R
1
and R
2
are not both hydrogen preferably from about 1 to about 4 carbon atoms, and where x averages from about 1 to about 9.
Examples of specific substituted alkyl-dihydroxyarenes that would be suitable in the composition of this invention include, but are not necessarily limited to, tert-butylhydroquinone; 2,5-di-tert-butylhydroquinone; tert-butylcatechol; hydroquinone; 3,5-di-tert-butylcatechol; catechol; 3,3,3′, 3′-tetramethyl-1,1′-spiro-bis-indane-5,5 ′, 6,6′-teterol; and mixtures thereof.
Hydrogen Transfer Agent
It is anticipated that any compound that readily transfers hydrogen by an insertion reaction that does not require stable, stand-alone intermediates would be expected to be useful in the invention. The hydrogen transfer agent is a separate component of the inventive composition different from the alkyl-dihydroxyarene. For any particular inventive composition, the alkyl-dihydroxyarene and the hydrogen transfer agent are not the same compound. Hydrogen transfer agents suitable for use in the polymerization inhibiting composition of this invention include, but are not necessarily limited to, naphthalene; anthracene; decalin; hydroquinoline; 1,2,3,4-tetrahydronaphthalene (TETRALIN®; DuPont); 9,10-dihydroanthracene; fluorene; squalane; squalene; trimethyldihydroquinoline, tetramethylhydroquinoline; and mixtures thereof.
Stable Nitroxide
The stable nitroxide of the composition useful for inhibiting polymerization of vinyl aromatic compounds may include, but are not necessarily limited to those having the formula:
where R
3
, R
4
, R
5
, and R
6
are the same or different and are independently selected from the group consisting of straight, branched, or cyclic alkyl groups of from 1 to about 9 carbon atoms, preferably from about 1 to 3 carbon atoms; where y averages from at least 1 to about 6; where Z is selected from the group consisting of hydrogen, oxygen, alkyl groups, alkoxy groups, hydroxyl, aryl groups, alkaryl groups, heterocyclic alkyl groups; and where when Z contains carbon atoms, may contain an average of from about 1 to 9 carbon atoms, preferably from about 1 to 3 carbon atoms.
Examples of specific stable nitroxides that would be suitable in the composition of this invention include, but are not necessarily limited to, 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO); 4-OXO TEMPO; 1-oxyl-2,2,6,6-tetramethylpiperidine; 1-oxyl-2,2,6,6-tetramethylpiperidin-4-one; 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-2-acetate; 1-oxyl-2,2,6,6-tetramethyl-1-piperidin-4-yl-2-ethylhexanoate and mixtures thereof.
Organic Amine
Organic amines suitable in the methods and compositions of this invention may include, but are not necessarily limited to, organic amines of the formula:
R
7
—NH—R
8
where R
7
and R
8
are the same or different and are independently selected from the group consisting of straight, branched, and cyclic alkyl groups; alkoxy groups; hydroxyalkyl groups; and aminoalkyl groups; averaging of from about 1 to about 20 carbon atoms, preferably from about 6 to about 9 carbon atoms, where both R
7
and R
8
are not simultaneously hydrogen.
Examples of specific organic amines that would be suitable in the composition of this invention include, but are not necessarily limited to, butylamine; hexylamine; n-octylamine; dodecylamine; cyclohexylamine; N,N-dihexylamine; ethanolamine; N-(2-aminoethyl)ethanol; ethylenediamine; 2-aminopropanol; and mixtures thereof.
Proportions
A number of factors affect the effective amounts of the alkyl-dihydroxyarenes, hydrogen transfer agents, and stable nitroxides of this invention that would be useful to inhibit the polymerization of a vinyl compound, including, but not necessarily limited to, the nature of the vinyl compound, the concentration of the vinyl compound, the temperature and pressure environment of the vinyl compound, the nature of the particular alkyl-dihydroxyarenes, hydrogen transfer agents, and stable nitroxides used, and the like. Nevertheless, some general guidelines as to the effective proportion of the alkyl-dihydroxyarenes, hydrogen transfer agents, and stable nitroxides in the vinyl compound may be given.
If the organic amine is not present, the composition of this invention may have from about 1 to about 10,000 ppm of the alkyl-dihydroxyarene; from about 1 to about 10,000 ppm of the hydrogen transfer agent; and from about 1 to about 10,000 ppm of the stable nitroxide, based on the total amount of vinyl aromatic compound being treated. Preferably, the proportions range from about 34 to about 200 ppm of the alkyl-dihydroxyarene; from about 34 to about 118 pp
Anthony Joseph D.
Baker Hughes Incorporated
Madan Mossman & Sriram P.C.
LandOfFree
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