Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Layered – stratified traversely of length – or multiphase...
Reexamination Certificate
2001-07-03
2004-08-17
Eashoo, Mark (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Layered, stratified traversely of length, or multiphase...
C264S209200
Reexamination Certificate
active
06776945
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to medical devices having extruded polymeric members. More specifically, the present invention relates to medical devices such as intravascular catheters and guide wires having extruded polymeric members with helical orientation.
BACKGROUND OF THE INVENTION
A wide variety of medical devices utilize extruded polymeric members. For example, intravascular catheters and guide wires commonly utilize an extruded polymeric member as a shaft component. Because intravascular catheters and guide wires must exhibit good torqueability, trackability and pushability, it is desirable that the extruded polymeric shaft component have good torque transmission, flexibility and column strength. These attributes are commonly incorporated into intravascular devices by utilizing a composite shaft construction. Alternatively, the polymer material which forms the shaft component may be oriented to enhance the mechanical characteristics thereof.
For example, U.S. Pat. No. 5,951,494 to Wang et al. discloses a variety of medical instruments, such as guide wires and catheters, formed at least in part of elongated polymer members having helical orientation. The helical orientation is established by processing an elongate polymer member with tension, heat and twisting. Wang et al. theorize that the tension, heat and twisting process results in a polymer member that has helical orientation on the molecular level. Such molecular helical orientation enhances torque transmission of the elongate polymer member, which is important for some types of intravascular medical devices that must be navigated through long and tortuous vascular pathways.
Wang et al. teach that the tension, heat and twisting is a post-processing technique performed on a preformed polymer member. The pre-formed polymer member may comprise, for example, a rod, a tube, a polymer-metal composite, or a polymer
on-metal composite. Because Wang et al. teach post-processing of a pre-formed polymer member, the resulting oriented polymer member inherently involves two (or more) separate processes. First, the polymer member must be formed by, for example, an extrusion process, and second, the polymer member must be oriented by post-processing (i.e., tension, heat and twisting).
Because these two separate processes may involve manufacturing inefficiencies, it is desirable to provide a single manufacturing process to form an elongate polymer member having helical molecular orientation. For example, it may be desirable to provide an extrusion process to obtain a polymer member with molecular helical orientation. However, to our present knowledge, such an extrusion process is not known in the prior art. Perhaps the closest examples of related extrusion processes are disclosed in U.S. Pat. No. 5,059,375 to Lindsay and U.S. Pat. No. 5,639,409 to Van Muiden.
Lindsay '375 discloses an extrusion process for producing flexible kink resistant tubing having one or more spirally-reinforced sections. The extruder includes a rotatable head having an extrusion passageway for spirally extruding a thermoplastic filament into a base thermoplastic material to form a spirally-reinforced tube. The rotatable head is rotated at a predetermined velocity to form the reinforcement filament in a spiral or helical pattern in the wall of the tubing. However, with this process, the wall of the tubing is not helically oriented at all, and neither the filament nor the wall of the tubing are helically oriented on the molecular level. Accordingly, the resulting tubing does not enjoy the advantages obtained by molecular helical orientation as disclosed in Wang et al.
Van Muiden '409 discloses an extrusion process for manufacturing a tube-like extrusion profile by conveying a number of divided streams of different polymeric materials to a rotating molding nozzle. The streams of material flow together in the rotating molding nozzle to form at least two helically shaped bands of material. After allowing the combined streams of material to cool off, an extrusion profile comprising a plurality of bands of polymeric material extending in a helical pattern is formed. However, the bands of material are not helically oriented on the molecular level as in Wang et al. since the helical pattern is imparted by the rotating nozzle when the polymeric materials are in a molten state.
From the foregoing, those skilled in the art will appreciate that there exists an unmet need for a single manufacturing process to form an elongate polymeric member having molecular helical orientation.
SUMMARY OF THE INVENTION
To address this unmet need, the present invention provides an elongate polymer member having molecular helical orientation formed by rotation immediately after passing through the extrusion head. In particular, the elongate polymer member is rotated downstream of the extrusion head in the molten state prior to solidification in order to impart the molecular helical orientation. The molten state refers to a state in which the polymer is below the melting temperature but above the glass transition temperature. Rotating the polymer member in the molten state allows the helical orientation to be imparted at the molecular level. In addition, rotating the polymer member in the molten state allows for more rotations per lineal foot than otherwise feasible with post-processing techniques.
The polymer member may be rotated at speeds of 1000 rpm or more, and preferably at 3,500 rpm or more. The extrusion rate may range from 10 fpm to 100 fpm, and preferably 20 fpm to 50 fpm. The resulting helical orientation ranges from 10 rotations per foot (rpf) to 350 rpf, and preferably ranges from 70 rpf to 175 rpf. The extrusion rate and/or the rotation rate may be varied during the extrusion process to vary the degree of molecular orientation at various positions along the elongate member.
The elongate polymer member may comprise a single polymer extrusion, a multi-polymer intermittent co-extrusion, or a multi-polymer continuous co-extrusion. The elongate polymer member may comprise a single layer, multiple layers, or a composite. The elongate polymer member may be extruded over a core member which may carry a substrate (e.g., PTFE tube, wire braid, wire coil, etc.) onto which the elongate polymer member is extruded. The core member may be removed after extrusion to form a tubular structure. The elongate polymer member may be fed back into the extrusion system for a second pass to create an outer layer preferably having a molecular helical orientation in the opposite direction from that of the first pass.
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U.S. patent application Ser. No. 09/898,717, Wang, filed Jul. 3, 2001.
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Chen John
Chin Albert
Sahatjian Ronald
Wang (Bruce) Yiqun
Wang Lixiao
Crompton Seager & Tufte LLC
Eashoo Mark
Sci-Med Life Systems, Inc.
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