Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-10-13
2002-04-16
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S333400, C525S341000, C525S342000, C525S343000, C525S353000, C525S366000, C525S379000, C525S381000
Reexamination Certificate
active
06372858
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention is directed to the use of solid nucleophilic reagents for conversion of the benzylic bromine functionality on brominated isobutylene/para-methylstyrene copolymer to other functionalities and methods of making and using the same.
2. Related Art
The benzylic halogen, like bromine, functionality on copolymers is uniquely suited as the base from which versatile functionalized saturated copolymers can be made because it can be made to undergo “clean” nucleophilic substitution reactions with a great range of nucleophiles, so that many desired types and amounts of functionality can be introduced without undesirable side reactions and under conditions which are mild enough to avoid degradation and/or cross-linking of the saturated copolymer containing the pendant benzylic halogen functionality. Furthermore, in many instances, it is possible to only partially convert the pendant benzylic halogen to another desired functionality while retaining some, or to later convert another portion of the remaining benzylic halogen functionality to yet another new functionality, so that copolymers containing mixed functionalities can be made. The mixed functionality has been utilized to provide unique combinations of properties, such as grafting with another functional polymer via one of the functionalities and then crosslinking or adhering to some surface via another of the functionalities. (See, e.g., U.S. Pat. No. 5,162,445 which is herein incorporated by reference.)
A benzylic halogen functionality constitutes a very active electrophile which will react under suitable conditions with any nucleophile capable of donating electrons to it. Suitable nucleophiles include, but are not limited to, those containing oxygen, sulfur, nitrogen, sodium, and potassium. Equally important to this versatility in types of nucleophiles which will react with the benzylic halogen functionality, is the relatively mild conditions under which these nucleophilic substitution reactions proceed so that substitution reactions can be completed to introduce the desired new functionality without cleavage or cross-linking reactions involving the saturated hydrocarbon backbone. For example, by using isobutylene/para-bromo-methylstyrene/para-methylstyrene terpolymers as a “base” polymer for modification, and by conducting nucleophilic substitution reactions under appropriate conditions many pendent functionalities have been prepared: (1) esters (many containing other functional groups such as acetate, stearate, linoleate, eleostrearate, acrylate, cinnamate, etc.); (2) hydroxyl (attached directly in place of the benzylic bromine or attached via another linkage); (3) carboxy; (4) nitrile; (5) quaternary ammonium salts; (6) quaternary phosphonium salts; (7) s-isothiuronium salts; (8) dithiocarbamate esters; and (9) mercaptans.
The above-described nucleophilic reactions require achieving an intimate contact between the reactants under the proper reaction conditions. In typical ion-exchange processes, the reactants involved are generally both small molecules; thus the required intimate contact is generally easily achieved by using a suitable solvent system. However, when one or both, of the reactants are attached to a large polymeric molecule, it is much more difficult to achieve the required intimate contact. In the instant invention, the benzylic halogen (the “polar” electrophile) is attached to and thus “buried” within a low polarity hydrocarbon copolymer matrix (the isobutylene/para-methylstyrene copolymer backbone). The achieving of the required intimate contact between the polar reactants (the electrophile and the nucleophile) when the electrophile (the benzylic halogen) is attached to and “buried” within the low polarity hydrocarbon polymer matrix presents a formidable challenge. The brominated isobutylene/para-methylstyrene copolymers containing reactive benzylic bromine electrophilic functionality are most readily soluble in low polarity hydrocarbon solvents with solubility parameters close to that of the copolymer (i.e. 6 to 7). On the other hand, most small molecule nucleophiles are either insoluble or only sparingly soluble in those low polarity solvents which are preferred for the benzylic bromine containing copolymers. Hence, it is difficult to find a common solvent for both reactants so that the nucleophilic substitution reaction can proceed. Furthermore, the low polarity hydrocarbon solvents in which the brominated benzylic bromine containing copolymers are soluble do not solvate the polar reaction sites (i.e. the electrophile
ucleophile sites) well so that the substitution reactions do not proceed at satisfactory rates even if the reactants are brought into contact in that low polarity medium.
Powers et. al. in U.S. Pat. No. 5,162,445 have described conditions under which nucleophilic substitution reactions, utilizing the benzylic halogen functionality of isobutylene/para-methylstyrene copolymers can be run but the conditions require the use of solvent blends containing a polar co-solvent to dissolve the nucleophilic reagent and solvate the reaction site; require the use of expensive phase transfer catalysts which are difficult to recover and reuse; require enhancing solubility of the nucleophilic reagents (in the low polarity hydrocarbon solvents in which the brominated isobutylene/para-methylstyrene copolymers are soluble) by using large and expensive organo-soluble cations such as tetrabutylammonium; and require very extensive and expensive washing steps to remove the by-products of the nucleophilic substitution reaction before the substituted isobutylene/para-methylstyrene copolymer can be worked up and recovered for use.
In particular, the required washing steps often greatly complicate and add to the cost of the process under the previously described reaction conditions. For instance: under the previously described conditions, the benzylic bromine on a brominated isobutylene-para-methylstyrene copolymer could be replaced with acrylate by a nucloephilic substitution reaction between the copolymer and tetrabutylammonium acrylate. The process would involve bringing the electrophile and the nucleophile into the required intimate contact by dissolving the copolymer in a hydrocarbon solvent such as hexane (or a hexane/isopropanol solvent blend); dissolving the tetrabutylammonium acrylate in a polar solvent such as isopropanol; mixing the two solutions and heating to effect the substitution reaction in a resulting solvent blend of approximately 85% hydrocarbon and 15% alcohol. (Alternatively, the tetrabutylammonium acrylate nucleophilic reagent could be formed “in-situ” by reacting tetrabutylammonium hydroxide with acrylic acid but the reaction medium would still have to be an hydrocarbon/alcohol blend and use of the expensive tetrabutylammonium cation would still be necessary.) The products of the nucleophilic substitution reaction would be the desired acrylate derivative of the copolymer and tetrabutylammonium bromide by-product in the mixed hydrocarbon/alcohol solvent blend (also containing some water by-product if the tetrabutylammonium acrylate nucleophilic reagent were formed “in-situ” by reacting tetrabutylammonium hydroxide with acrylic acid). It is necessary to completely remove the tetrabutylammonium bromide by-product during the work-up and recovery of the desired polymeric acrylate derivative because even small amounts of the tetrabutylammonium bromide left in the polymeric product can cause cross-linking and/or gelation in the polymeric product as well as introducing other product quality problems. Very extensive washing steps including basic, acidic, and then neutral washes are required to completely remove the tetrabutyl ammonium bromide. These washing steps are very time consuming and costly and make it very difficult and costly to recover and recycle the expensive tetrabutylammonium cation, the polar cosolvent (isopropanol) and any phase transfer catalyst used because these materials have been extracted and are present at high di
Chee Chia S.
Powers Kenneth William
Wang Hsien-Chang
Exxon Mobil Chemical Patents Inc.
Faulkner Kevin M.
Lipman Bernard
Peebles Brent M.
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