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
1999-10-28
2003-06-17
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...
C525S095000, C525S280000, C525S331900, C525S332200, C525S333100, C525S333400
Reexamination Certificate
active
06579940
ABSTRACT:
FIELD OF INVENTION
This invention, generally is directed to thermoplastic elastomers, methods for their manufacture and use, and to physically and mechanically improved articles manufactured therefrom. More specifically the present invention provides new thermoplastic elastomeric compositions, articles and methods of making same which embody the desirable physical qualities normally associated with natural rubber latex in addition to markedly reduced allergenicity and significantly improved chemical and physical properties including solvent resistance, elasticity and resilience.
BACKGROUND OF THE INVENTION
Broadly stated, the present invention provides new enhanced thermoplastic elastomers having unique combinations of physical, chemical, and mechanical properties which make them particularly well suited for replacing natural rubber latex in articles traditionally made from natural rubber latex. More specifically, the present invention is directed to functionally enhanced thermoplastic elastomers incorporating unique cross-linkages such that the compositions function as elastomeric materials having aspects of thermoset material stability and function. These unique materials have been optimized to function as improved replacements for cured natural rubber latex while maintaining, and even surpassing the beneficial physical, chemical, and mechanical properties of natural rubber latex. Moreover, in addition to being readily applicable to the majority of existing latex article manufacturing processes, the thermoplastic elastomeric materials of the present invention possess the added benefit of being compatible with continuous manufacturing techniques including extrusion, blow forming, injection molding, rolling and sheet formation.
Articles manufactured from natural rubber latex exhibit a variety of desirable properties including resistance to creep (resisting the undesirable elongation of a material under constant stress), compression resistance (the ability of an article to return to its original size and volume after squeezing), elasticity, solvent and plasticizer resistance, and overall biocompatibility. Unfortunately, a primary drawback associated with natural rubber latex articles is the growing number of people that are allergic to them.
Early attempts at producing articles made from alternative non-natural rubber latex materials have been generally successful though not without their associated problems. Substitute artificial or synthetic latex materials are relatively expensive when compared to natural rubber latex and in some cases are considerably more expensive. More importantly, in most applications their physical, mechanical, and chemical properties are markedly inferior to those of natural rubber latex. For example, some artificial rubbers lack sufficient elasticity or strength to function effectively as gloves. Some are affected by solvents making them difficult to use around alcohols or naturally occurring oils which can soften and degrade the material. Others exhibit deforming material creep when subjected to constant stress. This can result in sagging and bagginess which make such materials inappropriate for inflation balloons or similar structures. Other latex replacements possess poor compression resistance and permanently deform when subjected to compressive stress. These inferior properties can make it difficult to package, store, or use articles manufactured from these alternative materials without damage.
Accordingly, it is a primary objective of the present invention to provide an effective material suitable for use as a replacement for natural rubber latex in the production of commercial and medical products. Concomitant with this objective is providing elastomeric replacement materials for natural rubber latex that can be incorporated into most existing continuous manufacturing processes without significant modification or expense.
It is an additional objective of the present invention to provide alternative materials, especially for medical devices and products, enhancing their physical, chemical, and mechanical properties and thus the functionality of these devices and products.
SUMMARY OF THE INVENTION
These and other objects are achieved by the present invention which provides novel biocompatible, nonallergenic thermoplastic elastomeric compounds, methods for producing these compounds and articles made therefrom. The novel compounds made in accordance with the teachings of the present invention provide functionally enhanced thermoplastic elastomers that, as compared to natural rubber latex, are less allergenic, possess increased elastomeric resilience, decreased creep, and increased resistance to oils, lipids and organic solvents while simultaneously eliminating many of the adverse properties which can significantly limit the natural product's utility.
Articles made from the thermoplastic elastomeric (TPE) compounds of the present invention possess excellent elasticity, exceptional resilience, exhibit minimal creep and resist swelling when exposed to oils, lipids and organic solvents, yet remain non-toxic. This unique combination of physical and biological properties results in a material that is ideally suited for medical devices and other products including those which may contain natural rubber latex.
In one embodiment of the present invention, the thermoplastic elastomeric compounds are composed of at least one thermoplastic elastomer comprising individual triblock sub-units containing two polystyrene hard domains and one polyolefin rubber domain. In accordance with the teachings of the present invention the individual triblocks are uniquely cross-linked using double bonds present in the polystyrene hard domain, the polyolefin rubber domain, or both in order to modify the properties of the material.
In another embodiment of the present invention, the TPE is composed of individual diblock sub-units containing one polystyrene hard domain and one polyolefin rubber domain. The individual diblocks may be linked together through their polyolefin rubber domains using suitable coupling agents forming dendritic structures. Further, the diblocks of the present invention can be used with, or without, coupling reagents to modify their properties.
When produced in accordance with the teachings of the present invention these compounds can be modified to contain additional unsaturated groups that can be further cross-linked to increase TPE entanglement. The extent of entanglement present in the TPE is a function of the number, type and location of the double bonds and contributes to the TPE's final character and functionality. This, in turn, is controlled by the raw materials used and reaction conditions selected utilizing the teachings of the present invention. Thus, utilizing the teachings of the present invention, the thermoplastic elastomeric compounds of the present invention can be modified or designed to exhibit a wide range of physical properties. Depending on the extent of cross-linking present in the materials, these compounds can possess physical properties ranging from thermoplastics to thermoset resins. Consequently, precise control of the properties and functions of the materials and articles of the present invention can be achieved. This provides yet another advantageous aspect of the present invention and significantly increases the options available to materials engineers, product designers, and end users.
An initial step in the exemplary methods of producing thermoplastic elastomeric compounds of the present invention involves providing styrene monomers with a lithium catalyst in the presence of suitable olefin monomers such as isoprene or 1,3-butadiene. Additional alkyl and aryl compounds containing vinyl-type groups, coupling reagents, and/or halogen containing compounds may be added to the reaction mixtures resulting in a number of different TPE material classes including base TPEs, high strength TPEs and entanglement TPEs, each exhibiting its own combination of superior physical and chemical properties relative to natural rubbe
Asinovsky Olga
Cullman Louis
Edwards Lifesciences Corporation
Seidleck James J.
Vinitskaya Lena
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