Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-03-28
2002-07-16
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S487000, C524S507000, C524S508000, C524S578000, C524S513000, C524S515000, C523S105000, C523S113000
Reexamination Certificate
active
06420475
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to novel gels and their uses.
BACKGROUND OF THE INVENTION
Like (SEPS) poly(styrene-ethylene-propylene-styrene), random mixtures of ethylene and butylene midblock copolymer segment of conventional SEBS poly(styrene-ethylene-butylene-styrene) block copolymers is almost totally amorphous, substantially free of any crystallinity or non-crystalline. Such SEBS block copolymers with substantially non-crystalline ethylene-butylene elastomer midblock segment are used for making elastomeric gels of varying rigidities which can vary from soft to firm. Such gels are hereafter referred to as “non-crystalline midblock gels” or “amorphous midblock gels” or more simply “amorphous gels”. Generally, the properties of amorphous gels increase with increasing gel rigidity. The amorphous gels at any rigidity, however, can fail catastrophically when cut or notched while under applied forces of high dynamic and static deformations, such as extreme compression, torsion, high tension, high elongation, and the like. Additionally, the development of cracks or crazes resulting from a large number of deformation cycles can induce catastrophic fatigue failure of amorphous gel composites, such as tears and rips between the surfaces of the amorphous gel and substrates or at the interfaces of interlocking material(s) and amorphous gel. Consequently, such amorphous gels made from SEPS and SEBS are inadequate for the most demanding applications involving endurance at high stress and strain levels over an extended period of time.
SUMMARY OF THE INVENTION
I have now discovered novel gels with improved properties made from thermoplastic elastomer copolymers and block copolymers having one or more substantially crystalline polyethylene segment midblocks exhibiting greater advantage over other non-crystalline component forming gels. The crystal gels advantageously exhibit high, higher, and ever higher tear resistances than ever realized before as well as improved high tensile strength.
The advances in improved properties of the crystal gels over amorphous gels are many, these include: improved damage tolerance, improved crack propagation resistance, improved tear resistance, improved resistance to fatigue, etc. Such crystal gels are advantageous for end-use involving repeated applications of stress and strain resulting from large number of cycles of deformations, including compression, compression-extension (elongation), torsion, torsion-compression, torsion-elongation, tension, tension-compression, tension-torsion, etc. The crystal gels also exhibit improved damage tolerance, crack propagation resistance and especially improved resistance to high stress rupture which combination of properties makes the gels advantageously and surprisingly exceptionally more suitable than amorphous gels made from non-crystalline poly(ethylene) component copolymers at corresponding gel rigidities.
The crystal gels which are advantageously useful for making various toys, medical devices, and other useful articles of manufacture including disposable inflatable restraint cushions comprises: 100 parts by weight of one or more high viscosity (I) linear triblock copolymers, (II) multi-arm block copolymers, (III) branched block copolymers, (IV) radial block copolymers, (V) multiblock copolymers, (VI) random copolymers, (VII) thermoplastic crystalline polyurethane copolymers with hydrocarbon midblocks or mixtures of two or more (I)-(VII) copolymers in combination with or without major or minor amounts of one or more other (VIII) copolymers or polymers, said copolymers having one or more segments or one or more midblocks comprising one or more substantially crystalline polyethylene segments or midblocks and selected amounts of a compatible plasticizer (IX) sufficient to achieve gel rigidities of from less than about 2 gram Bloom to about 1,800 gram Bloom with the proviso that when said (I)-(VII) copolymers having nil amorphous segment or nil amorphous midblock are combined with one or more (VIII) copolymers having one or more amorphous segments or amorphous midblocks to form a stable plasticizer compatible gel.
As used herein, the term “gel rigidity” in gram Bloom is determined by the gram weight required to depress a gel a distance of 4 mm with a piston having a cross-sectional area of 1 square centimeter at 23° C.
The gels comprising the thermoplastic elastomer copolymers and block copolymers having one or more substantially crystalline polyethylene segments or midblocks of the invention are hereafter referred to as “elastic-crystalline gels” or simpler “crystal gels”. The segments or midblocks of copolymers forming the crystal gels of the invention are characterized by sufficient crystallinity as to exhibit a melting endotherm of at least about 40° C. as determined by DSC curve.
The various types of high viscosity copolymers and block copolymers employed in forming the crystal gels of the invention are of the general configurations (Y-AY)n copolymers, A-Z-A, and (A-Z)n block copolymers, wherein the subscript n is two, three, four, five or more. In the case of multiarm block copolymers where n is 2, the block copolymer denoted by (A-Z)n is A-Z-A. It is understood that the coupling agent is ignored for sake of simplicity in the description of the (A-Z)n block copolymers.
The segment (A) comprises a glassy amorphous polymer end block segment which can be polystyrene, poly(alpha-methylstyrene), poly(o-methylstyrene), poly(m-methylstyrene), poly(p-methylstyrene) and the like, preferably, polystyrene.
The segment (Y) of (VI) copolymers (Y-AY)n comprises substantially crystalline poly(ethylene) (simply denoted by “-E-” or (E)). In the case of (VI) copolymers (A-Y)n, (Y) when next to (A) may be substantially non-crystalline or amorphous ethylene segments. For example a crystalline copolymer (Y-AY)n may be represented by: . . . -E-E-E-E-E-E-E-E-E-SE-E-E-E-E-E-E-SE-E-E-E-E-E-E-SE- . . . Where Y is a long run of polyethylenes or a non-crystalline copolymer (AY-AY)n: . . . -E-SE-SE-E-SE-E-SE-E-SE-E-E-SE-SE-E-SE- . . . , Where Y is a non-crystalline run of ethylene.
The end block segment (A) comprises a glassy amorphous polymer end block segment which can be polystyrene, poly(alpha-methylstyrene), poly(o-methylstyrene), poly(m-methylstyrene), poly(p-methylstyrene) and the like, preferably, polystyrene. The segment (Y) of (VI) random copolymers A-Y comprises substantially crystalline poly(ethylene) (simply denoted by “-E-” or (E)). In the case of (VIII) random copolymers A-Y, (Y) may be substantially non-crystalline or amorphous ethylene segments. The midblocks (Z) comprises one or more midblocks of substantially crystalline poly(ethylene) (simply denoted by “-E- or (E)”) with or without one or more amorphous midblocks of poly(butylene), poly(ethylene-butylene), poly(ethylene-propylene) or combination thereof (the amorphous midblocks are denoted by “-B- or (B)”, “-EB- or (EB)”, and “-EP- or (EP)” respectively or simply denoted by “-W- or (W)” when referring to one or more of the amorphous midblocks as a group) The A and Z, and A and Y portions are incompatible and form a two or more-phase system consisting of sub-micron amorphous glassy domains (A) interconnected by (Z) or (Y) chains. The glassy domains serve to crosslink and reinforce the structure. This physical elastomeric network structure is reversible, and heating the polymer above the softening point of the glassy domains temporarily disrupt the structure, which can be restored by lowering the temperature. During mixing and heating in the presence of compatible plasticizers, the glassy domains (A) unlock due to both heating and solvation and the molecules are free to move when shear is applied. The disruption and ordering of the glassy domains can be viewed as a unlocking and locking of the elastomeric network structure. At equilibrium, the domain structure or morphology as a function of the (A) and (Z) or (A) and (Y) phases (mesophases) can take the form of spheres, cylinders, lamellae, or bicontinous structures. The scale of separation of
Applied Elastomerics, Inc.
Sanders Kriellion
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