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
1998-12-08
2001-02-06
Henderson, Christopher (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...
C525S358000, C525S359400, C525S342000, C525S353000
Reexamination Certificate
active
06184309
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to processes for removing protecting groups from protected functionalized polymers.
BACKGROUND OF THE INVENTION
Mono- and di-functional polymers (i.e., telechelic polymers that contain two functional groups per molecule at the termini of the polymer) have found wide utility in many applications. For instance, telechelic polymers have been employed as rocket fuel binders, in coatings and sealants and in adhesives. In addition, polymers that contain two hydroxyl groups per molecule can be co-polymerized with appropriate materials to form polyesters, polycarbonates, and polyamides (see U.S. Pat. No. 4,994,526).
A variety of polymerization techniques, such as cationic and free radical polymerizations, have been employed to prepare functional polymers. However, functionality can be best controlled with anionic polymerization. Living anionic polymerization of styrene and diene monomers were first described by Szwarc and his coworkers. See M. Szwarc,
Nature
178, 1169 (1956) and M. Szwarc, et al.,
J.Am.Chem.Soc.
78, 2656 (1956).
Various publications have discussed the use of protected functional initiators to provide telechelic polymers. An early approach to the preparation of telechelic polymers is discussed in D. N. Schulz, et al.,
J.Polym.Sci., Polym.Chem.Ed.
12, 153 (1974), which describes the reaction of a protected hydroxy initiator with butadiene. The resultant living anion was quenched with ethylene oxide to afford mono-protected di-hydroxy polybutadiene. While excellent functionality (f=1.87-2.02) was achieved by this process, the protected initiator was insoluble in hydrocarbon solution. Therefore, the reaction was conducted in diethyl ether, and as a result, relatively high 1,2 microstructure (31-54%) was obtained.
U.S. Pat. Nos. 5,331,058 and 5,362,699 to Shepherd, et al. discuss the preparation of telechelic polymers in hydrocarbon solutions using monofunctional silyl ether initiators. These monofunctional silyl ether initiators can be useful in producing dihydroxy (telechelic) polybutadienes having desirable characteristics, such as a molecular weight of typically 1,000 to 10,000, a 1,4 microstructure content of typically 90%, and the like.
These and other anionic polymerization techniques, and in particular those using protected functional initiators, can be useful for the preparation of protected functional polymers. However, problems have been encountered in deprotecting or removing the protecting group from functional polymer moieties. Typically, prior deprotecting processes can require the use of costly reagents, result in partial or essentially no cleavage of the protecting group, lack economic feasibility in commercial production (for example, require high temperatures, long reaction times, etc.), alter the polymer structure, and the like.
For example, U.S. Pat. Nos. 5,331,058 and 5,362,699 discuss the use of tetraalkylammonium fluorides in polar solvents as useful desilylation reagents. However, tetraalkylammonium fluoride reagents can be costly and difficult to handle due to their toxicity (see discussion in U.S. Pat. No. 5,376,745). Further, it can be difficult to effectively remove the silyl protecting groups of these types of initiators using tetraalkylammonium fluoride, and other, reagents. Other reagents, such as tert-butyldimethylsilyl triflate, can alter the polymer structure.
SUMMARY OF THE INVENTION
The present invention provides processes for deprotecting functionalized polymers, including mono- and di-functional polymers and functionalized multi-branched or star polymers. In the invention, the protected functionalized polymer is treated in the presence of an acid catalyst under conditions selected to remove at least one protecting group. Exemplary acid catalysts useful in the present invention include organic acids, mineral acids, heterogeneous acid systems, Lewis acids and fluoride ion sources.
The process of the invention is capable of being conducted at a variety of temperatures and processing times, ranging from ambient to about 200° C., and from about one hour to about 24 hours, thus imparting flexibilty to the deprotection process. Further, protected functionalized polymers can be effectively deprotected in accordance with the invention using relatively mild conditions and with minimal or no structural changes in the polymer. The process of the invention can also offer economies of production, including reduced reaction times, temperatures, lower reagent costs, and the like. Still further, deprotection conditions can also be selected to provide selected deprotection of dissimilar protecting groups, or to provide partial deprotection, as desired.
DETAILED DESCRIPTION OF THE INVENTION
The processes of the present invention are useful for deprotecting functionalized polymers, including mono- and di-functional polymers and functionalized multi-branched or star polymers. Polymers which can be deprotected in accordance with the present invention can be represented by the following general formulas:
FG-(Q)
d
—R
n
—Z—J-[A(R
1
R
2
R
3
)]) (I)
or
L[(Q)
d
—R
n
—Z—J-[A(R
1
R
2
R
3
)]
x
]
m
(II)
wherein FG is H or a protected or non-protected functional group; Q is a saturated or unsaturated hydrocarbyl group derived by incorporation of a compound selected from group consisting of conjugated diene hydrocarbons, alkenylsubstituted aromatic hydrocarbons, polar compounds, and mixtures thereof; d is an integer from 10 to 2000; R is a saturated or unsaturated hydrocarbyl group derived by incorporation of a compound selected from the group consisting of conjugated diene hydrocarbons, alkenylsubstituted aromatic hydrocarbons, and mixtures thereof; n is an integer from 0 to 5; Z is a branched or straight chain hydrocarbon group which contains 3-25 carbon atoms, optionally containing aryl or substituted aryl groups; J is oxygen, sulfur, or nitrogen; [A(R
1
R
2
R
3
)]
x
is a protecting group, in which A is an element selected from Group IVa of the Periodic Table of Elements; R
1
, R
2
, and R
3
are each independently selected from the group consisting of hydrogen, alkyl, substituted alkyl groups containing lower alkyl, lower alkylthio, and lower dialkylamino groups, aryl or substituted aryl groups containing lower alkyl, lower alkylthio, and lower dialkylamino groups, and cycloalkyl and substituted cycloalkyl containing 5 to 12 carbon atoms; and x is dependent on the valence of J and varies from one when J is oxygen or sulfur to two when J is nitrogen; L in Formula II is a linking or coupling agent, as described below; and m can be an integer from 3 to 50.
In the present invention, a polymer as represented by Formulas (I) or (II) above is treated with an acid catalyst which is suitable for removing or cleaving the protecting group [A(R
1
R
2
R
3
)]
x
. The process of the invention is particularly useful for the removal of alkyl ether protecting groups wherein J is oxygen and A is carbon, although the invention is not limited to removal of these groups.
The acid catalyst employed in accordance with the invention is generally selected from the group consisting of organic acids (including without limitation para-toluenesulfonic acid, trifluoroacetic acid, acetic acid, methanesulfonic acid, and the like), dilute mineral acids (including without limitation hydrochloric acid, phosphoric acid, sulfuric acid, and the like, having a concentration between about 0.01 N and about 12 N), heterogeneous acid systems (including without limitation acid ion exchange resins, such as Amberlyst® 15, a commercially available polystyrene-based resin with sulfonic acid groups, Dowex® 50, a commercially available polystyrene-based resin from Dow Chemical, Reillex® 425 HCl, a commercially available polyvinyl pyridine-based resin from Reilly Tar and Chemical, acid clays, and the like), Lewis acids (including without limitation trimethylsilyl iodide, iron (III) chloride with acetic anhydride, boron trihalides, such as boron trifluoride, and the like) and s
Engel John F.
Granger Eric J.
Kamienski Conrad W.
Quirk Roderic P.
Schwindeman James A.
Alston & Bird LLP
FMC Corporation
Henderson Christopher
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