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
2002-05-29
2004-06-08
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S244000, C525S245000, C525S268000, C525S098000, C525S316000
Reexamination Certificate
active
06747098
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to arborescent or highly branched block copolymers comprising branched soft segments with a low glass-transition temperature (T
g
) and hard segments with a high T
g
or crystalline melting point that exhibit thermoplastic elastomeric properties. More particularly this invention relates to highly branched block copolymers of polyisoolefins and polymonovinylidene arenes that exhibit thermoplastic elastomeric properties.
BACKGROUND OF THE INVENTION
Thermoplastic elastomers (TPEs) are polymeric materials, which combine the properties of vulcanized rubbers and the processability and recylability of thermoplastics, see for example B. M. Walker,
“Handbook of Thermoplastic Elastomers
”, Van Nostrand Reinhold, New York (1979). While blends of elastomers and plastics are not compatible and show gross phase separation, block copolymers can only phase separate on a microscopic scale due to the connectivity of elastomeric and plastic blocks.
Branched polymers are of commercial interest due to their having markedly lower viscosity and less shear sensitivity than their linear counterparts. Thus branched block copolymers that have the added benefit of being thermoplastic elastomers should have a wide variety of commercial applications depending upon the elastomer and the thermoplastic used to form the block copolymer.
About 40% of TPEs are block copolymers, which contain both soft segments with a low glass-transition temperature (T
g
) and hard segments with a high T
g
or crystalline melting point, see G. Holden, in “
Rubber Technology”
, ed. M. Morton, Van Nostrand Reinhold, New York, Ch. 16, 465 (1987). The hard segments associate, leading to physical crosslinks, which disappear when heated above a certain temperature (Order-Disorder Temperature, ODT) and reappear immediately on cooling. The hard phase determines the mechanical strength, heat resistance, upper service temperature and strongly affects the oil and solvent resistance of a TPE. The chemical nature of the soft segments has an influence on elastic behavior, low temperature flexibility, thermal stability and aging resistance. According to present understanding in the field, in order to get good phase separation in block-type TPEs leading to good mechanical properties, the length of the elastomer chains should be as uniform as possible. This can be achieved by living polymerization, a unique process without termination and other side reactions of the growing polymer chain. Living conditions producing relatively uniform polymers can be achieved in anionic, cationic and radical systems.
An important commercial example of thermoplastic elastomeric block copolymers is styrene-elastomer-styrene, produced by living anionic polymerization. Most of the styrenic block copolymers have the general formula S-E-S, where S represents a hard amorphous polystyrene block and E represents a soft elastomeric block. Many of the polystyrene-polydiene block copolymers that are TPEs have the basic structure poly(styrene-block-butadiene-block-styrene) (S-B-S) or poly(styrene-block-isoprene-block-styrene) (S-I-S). The applications of these block copolymers are numerous. Important applications include solvent based and hot melt adhesives, sealants, coatings, hose, asphalt modifiers and sporting goods and automobiles, see G. Holden, N. R. Legge, R. Quirk, H. E. Schroeder (Eds.),
“Thermoplastic Elastomers—A comprehensive Review”
, Hanser Publishers, Munich (1996) and G. Holden, in
“Encyclopedia of Polymer Science and Engineering
”, ed. J. I. Kroschwitz, John Wiley and Sons, New York, Vol. 5, 416 (1996).
Recently, TPEs from another class of styrenic block copolymers have been developed with polyisobutylene (PIB) elastomeric segments, see U.S. Pat. No. 4,946,899 issued to J. P. Kennedy et al.
FIGS. 1A and 1B
show a diagrammatic representation of the first generation of these PIB-based TPEs which are linear triblock (
FIG. 1A
) and triarm—star block structures shown in
FIG. 1
b
. An important advantage of these TPEs based on polyisobutylene-polystyrene (S-IB-S) block copolymers is that there is no need of hydrogenation of the elastomeric segments like that in the case of S-B-S or S-I-S, because of the presence of a saturated PIB elastomeric block. These novel TPEs were found to have excellent damping characteristics (similar to butyl rubber over a wide frequency range), oxidative and hydrolytic stability and good gas barrier properties, see K. Koshimura, H. Sato,
Polym. Bull,
29, 705 (1992) and J. P. Puskas, G. Kaszas,
Rubber Chem. Technol.,
66, 462 (1996).
The first generation of these TPEs were linear and triarm-star blocks, whose synthesis and basic chemical characterization have been reported, see G. Kaszas, J. E. Puskas, W. G. Hager and J. P. Kennedy,
J. Polym. Sci., Polym. Chem
., A29, 427 (1991).and J. E. Puskas, G. Kaszas, J. P. Kennedy, W. G. Hager,
J. Polym. Sci., Polym. Chem
., A30, 41 (1992). The living polymerization of IB by di- and tri-functional initiators gives a uniform rubbery mid-block, followed by the sequential addition of styrene (St) which results in a glassy outer block.
The architecture of copolymers can be controlled by the synthesis procedure, and TPEs with various composition and molecular weight (MW) have been prepared and characterized; for a review see J. P. Puskas, G. Kaszas,
Rubber Chem. Technol.,
66, 462 (1996). The most frequently used initiators are di- and tricumyl derivatives, especially di- and tricumyl-ether and -chloride. The co-initiator mainly used for making high molecular weight PIBs, suitable for block copolymer synthesis, is TiCl
4
. The control of living IB polymerization is further improved by the use of electron pair donors like dimethyl sulfoxide or dimethyl acetamide and a proton trap such as di-tert-butyl pyridine (DtBP). These additives lead to better control of IB polymerization, resulting in narrow molecular weight distribution (MWD) PIB, and also improve the blocking efficiency of St monomers during TPE synthesis.
The S-IB-S triblocks and three-arm radial blocks obtained in the absence of electron pair donor and/or proton trap exhibit poor tensile properties due to inefficient blocking. The process has successfully been scaled up to a lb/batch scale (G. Kaszas, Polym. Mater. Sci. Eng., 67, 325 (1992) and an inventory of block copolymers have been prepared and characterized (P. Antony, J. E. Puskas: Proceedings of the Polymer Processing Society Meeting, May 21-24, Montreal, Canada (2001). Kuraray Inc., Japan, recently test-marketed linear S-IB-S block copolymers. The important emerging applications of these first generation linear and tri-star block copolymer materials include medical applications such as rubber stoppers for drugs and blood, gaskets and caps for syringes, blood and drug storage bags and tubes and the like as disclosed in Japanese Patent No. 5,212,104; Japanese Patent No. 5,269,201; and Japanese Patent No. 5,295,054.
Due to the high oxidative and chemical stability of the S-IB-S macromolecules, these materials have the potential to replace silicone rubber or other soft to semirigid bio-implantable polymers; U.S. Pat. Nos. 5,741,331 (1998); 6,102,939 (2000); and 6,197,240 (2001) issued to Pinchuk, L. Pinchuk, I. J. Khan, J. B. Martin and G. J. Wilson: Polyisobutylene-Based Thermoplastic Elastomers For Ultra Long Term Implant Applications; Sixth World Biomaterials Congress Transactions, 1452 (2001), and Pinchuk, L., Khan, I. J., Martin, J. B., Bridgeman, J., Wilson, G. J., Glass, J., Si, J. and Kennedy, J. P.; A New Family of Thermoplastic Elastomers for Ultra-Long Term Implant Based Upon a Backbone of Alternating Quaternary and Secondary Carbons”; 24
th
Annual Meeting of the Society for Biomaterials; April 22-26, San Diego, (1998), p. 173; are directed to biologically stable, non-biodegradable implant devices and methods of producing same, using linear or star polyolefin copolymers having the structures shown in FIG.
1
. They also disclosed the structure shown in FIG.
2
A.
The second generation of PIB-based TPEs shown in
FIG.
Antony Prince
Paulo Christophe
Puskas Judit E.
Asinovsky Olga
Hill & Schumacher
Schumacher Lynn C.
Seidleck James J.
The University of Western Ontario
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