Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-07-13
2003-08-05
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S218100, C526S219000, C526S308000, C526S340200, C526S346000, C526S348700, C585S527000
Reexamination Certificate
active
06602967
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates, generally, to use of initiators for cationic polymerization, and specifically, to use of carbocations formed through deamination as initiators of addition polymerization.
2. Description of Related Art
In general, four reaction intermediates exist for initiation of addition polymerization: Zeigler-Natta catalysts, carbocations, free radicals and carbanions. Addition polymerization is readily accomplished via free radicals and carbanions but conventional initiation via carbocations is limited principally by low initiator reactivity.
Cationic polymerization represents an important body of techniques for the synthesis of many polymers possessing unique structures and properties. The cations used to initiate polymerizations include protons, oxonium ions and carbocations. Two chemical sources of carbocations are currently in use:
(1) Stable carbocation salts such as hexafluoroantimonates of trityl and tropylium carbocations. These species are able to initial polymerizations of reactive monomers such as styrenes but they are too stable to initiate polymerizations of less reactive monomers such as ethene (ethylene) and isobutene.
(2) Haloalkane/Friedel-Crafts (F-C) complexes. These systems generate carbon-based electrophiles which are not “free” carbocations. The carbocations generated are more reactive than carbocations salts but are still unable to initiate polymerization of monosubstitued alkenes and ethene. Additionally, the utility of this system is compromised by the inability to identify the actual initiating species (polarized haloalkane, carbocation, ion pair, or ion multiplet), extreme moisture sensitivity, and limited catalyst solubility in many of the common solvents.
Carbocations, also known as carbenium ions, generated through deamination are known in the art to be highly reactive. Deamination is defined to mean the class of reactions in which nitrogen or a nitrogen-containing molecule is extruded during the course of reaction to generate a reactive intermediate. Dediazoniation is the step along the reaction pathway when the nitrogenous molecule is lost.
Several methods exist for accessing deaminatively generated carbocations that are formed as part of an nitrogen-separated ion pair or nitrogenous-molecule-separated ion pair (NSIP). These highly reactive cations are inaccessible via solvolytic routes. The carbocations formed through this deaminative approach are discussed by the inventor and others in
A Study of Essentially Free Carbocations Derived via Diazonium and Oxo Diazonium Ions in the Liquid Phase
, Journal of Organic Chemistry, Vol. 64, No. 16. Deaminative methods for generating these highly reactive carbocations include:
nitrosoamide thermolyses
nitroamide thermolyses
acidification of diazoalkanes and triazenes
nitration and nitrosation of N-alkyl-O-acylhydroxylamines, amines, and salts of amides
acylation of salts of N-nitroso and nitroamines
decomposition of alkadiazenyl-2-oxide esters
The critical component is the presence of nitrogen in the carbocation precursors to form N2 or NO as the inert molecule. The presence of the inert molecule blocks the carbocation from its counterion to allow reaction with any other nucleophiles present, e.g., the solvent or in this invention, the monomer. The NSIP can be depicted by:
R
3
C+N
2
or N
2
OR′XO
R=hydrogen and/or any compound that forms a secondary, tertiary or resonance-stabilized carbocation such as, but not limited to, CH3, benzyl ring
R′=any [organic] compound
X=any acid function, including but not limited to CO and SO
2
Intramolecular modes of deamination by appropriate modification of the amine or by direct attachment to a nitrous acid equivalent are known in the art. See White, et al., J. Am. Chem. Soc. 1992, 114, 8023. In unimolecular generation of carbocations from N-nitroso- and N-nitroamides, the substrates already possess built-in groups so that on thermolysis, diazonium ions (or analogues) are formed; the latter then dediazoniate to the corresponding carbocation(s). For example, an N-alkyl-N-nitrosoamide rearranges on heating to form an unstable trans-diazotate ester which then fragments into an intimate ion pair containing a diazonium ion. The latter readily deadizaoniate to form a nitrogen-separated ion pair.
U.S. Pat. Nos. 5,032,653 and 5,336,745 disclose the addition of nitrogen-containing compounds as functional groups to polymers. Similarly U.S. Pat. Nos. 5,444,135 and 5,629,394 disclose the addition of nitrogen containing compounds as functional groups to polymers by living cationic polymerization. The processes disclosed discuss cationic polymerization using a cationic catalyst, preferably Freidel-Crafts catalyst, in the presence of monomer and the nitrogen initiator compound. The nitrogen initiator releases a nitrogen functional group that then binds with the developing polymer. Although this loss of nitrogen functional group may be viewed broadly as a deaminative step, the compound that releases the nitrogen group is not disclosed or claimed to initiate the polymerization in any way.
U.S. Pat. No. 5,223,591 discloses a carbocation initiator formed through activation of a sulfonium salt. The distinguishing feature of the invention is the retention of the sulfide by covalent bond with the cationic fragment that initiates polymerization. The carbocation is activated by thermal, photochemical or electron bombardment of a heterocyclic, aryl substituted or with an aryl ring fused sulfonium salt with a non-nucleophilic anion which causes the ring to open. The carbocations discussed do not disclose deamination as the formative step, nor the inclusion of nitrogen or nitrogen containing compounds to form the carbocation.
U.S. Pat. No. 5,376,744 discloses a process for polymerizing olefinic monomers using carbocations known in the art in a medium of supercritical carbon dioxide. The use of supercritical carbon dioxide rather than hydrocarbon solvents allows polymerization at higher temperatures, i.e., between 31 to 60° C. without decreasing the molecular weight of the resulting polymer. The supercritical carbon dioxide is not claimed to initiate the reaction in any way.
U.S. Pat. Nos. 4,112,209 and 4,161,573 disclose a process for making polystyrene with molecular weight between 1,000 and 50,000 using “commonly known” cation generators including protonic acids and Freidel-Craft catalysts in a solvent. The claimed process is limited to styrene contacted with cation generators in 3 or more stages while maintaining substantially isothermal conditions between 0° C. and 120° C., with styrene always present in greater stoichiometric amount in relation to the cation. The formation of carbocations by deamination in particular is not discussed as a, “commonly known” cation generator.
Carbocations formed through thermolysis of N-nitrosoamides to initiate polymerization form polystyrene yielding 10
6
molecular weight is discussed by the inventor and others in
Deaminatively Generated Carbocations as Initiators of Styrene Polymerization
, Organic Letters 1999, Vol. 1, No. 5, which is incorporated herein by reference. In that study, the polystyrene produced was at least one order of magnitude higher than that commercially available.
Polymers with high molecular weight and/or high melting points have potential commercial viability but their production is currently limited by existing commercial methods. Polymerization by free radical initiators terminates the polymer chain too quickly, preventing the formation of long polymer chains that raise the average molecular weight of the polymer and increase its melting point. Polymerization initiated through carbanions proceeds too slowly, i.e., over several days, to have much commercial viability.
Polymer melting point is a function of both mass and structure, tacticity, and crystallinity. Zeigler-Natta catalysts
Darbeau Ron W.
Delaney Mark S.
Ramelow Ulku
Kean, Miller, Hawthorne, D'Armond, McCowan & Jarman L.L.P.
McNeese State University
Teskin Fred
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