WO2002002171A2

WO2002002171A2 - Coextruded plastic catheter

Info

Publication number: WO2002002171A2
Application number: PCT/US2001/020426
Authority: WO
Inventors: Ludwig Simmet
Original assignee: Minitube Of America, Inc.
Priority date: 2000-06-29
Filing date: 2001-06-27
Publication date: 2002-01-10
Also published as: WO2002002171A3; AU2001271517A1

Abstract

A coextruded plastic catheter is disclosed having an outer plastic layer and an inner plastic layer. The interface between the inner layer and the outer layer has a non-circular cross-section to resist separation of the two layers due to torsional forces. The inventive catheter is useful for reproductive and other medical procedures.

Description

COEXTRUDED PLASTIC CATHETER This invention relates to coextruded catheters for use in medical procedures, particularly for use in reproductive procedures.

Coextrusion allows the production of an article made up of two or more different materials. The use of multiple materials of construction is advantageous for articles that must meet multiple physical properties that are difficult, if not impossible, to obtain in a single material. Such a device is a catheter wherein physical properties such as flexibility, stiffness and coefficient of friction may be critical to the proper functioning of the catheter. Several coextruded catheters are known in the art. USP 5,348,536, issued to Young et al., discloses a coextruded multilayer catheter in which one layer is a soft elastic material such as silicone and the other layer is a stiffer material. The harder material of the coextruded material of Young et al. need not extend the full length of the softer material. The catheter of Young et al. is disclosed to be particularly useful for hemodialysis. USP 5,538,510, issued to Fontirroche et al., discloses an intravascular catheter comprising a length of flexible plastic tubing which, in turn, comprises an outer plastic layer and an inner plastic layer. The plastic materials of the outer and inner layers of the Fontirroche et al. catheter are different, and may be chemically bonded to each other. USP 5,961,765, issued to Kastenhofer, discloses an interventional catheter for angioplasty and the like, comprising a catheter tube formed of two superposed layers of materials different from one another. The inner layer of the Kastenhofer catheter is comprised of a low friction non-kinkable material and the outer layer is comprised of material with a higher friction coefficient than the material forming the inner layer.

However, the adhesion of the two material layers to each other is a concern for the above prior art catheters. Indeed, as reported in "Propylene: Structure, Blends and Composites" edited by J. Karger-Kocsis (1995 Chapman & Hall, London) page 51, the great majority of polymer blends are immiscible. As a result, interfacial adhesion in. both molten and solid states is usually poor. The problems associated with poor adhesion between the layers are emphasized when the catheter is connected to other articles due to torsional forces caused by rotating the catheter and article in relation to each other. The problem is further intensified as the size of the catheter is increased because it is easier to exert higher torsional forces with larger parts.

The prior art references have disclosed the use of chemical bonding as a means of improving the adhesion between the two layers. However, as is well known in the art, many polymers are very resistant to chemical reactions. Therefore, a coextruded catheter wherein the two layers maintain their positions relative to each other is still desired. One hallmark of the current invention is such a catheter.

A catheter is disclosed comprising:

A. A first component comprising an outer tube having an inner cross-section having a non-circular shape; and

B. A second component comprising an inner tube in intimate contact with the outer tube with an outer cross-section having a shape identical to the shape of the inner cross-section of the first component; wherein the second component is contiguous within the first component such that the inner cross-section of the first component coincides with the outer cross-section of the second component.

The current invention advantageously maintains the two components of the catheter in relation to one another without the requirement of chemical bonding to adhere the two components to each other. FIG. 1 shows a top perspective view of a catheter adapted for use in artificial insemination of swine.

FIG. 2 shows a cross-section, along the line (2), of the catheter of FIG. 1 wherein the innermost cross-section is non-circular. FIG. 3 shows a cross-section, along the line (2), of the catheter of FIG. 1 wherein the innermost cross-section is circular.

Coextruded products are produced by known plastic extrusion methods. However, instead of using one plastic resin, several plastic resins are extruded simultaneously. This is accomplished by having multiple extruders, each processing one material, feeding plastic melt into a common die. The coextruded products can achieve properties that are superior to those of single-material extruded products, or that are unavailable from single-material extruded products. This synergistic effect supports the design and manufacturing of single plastic parts that have the properties of products that would otherwise have to be assembled. The inventive catheter is made from at least two different plastics. These two separate plastics flow from their respective extruders through separate conduits until the flows merge just prior to the extrusion die. The conduit for the inner component is located within the conduit for the outer component and the two conduits are generally concentric. The merger of the two melt streams puts each stream in intimate contact with the other in a two-fluid flow pattern. As such, the outer component forms an outer tube and the inner component forms an inner tube in intimate contact with the outer tube, such that the outer tube and inner tube together form a single channel catheter tube. The outer component and the inner component are contiguous both radially along the circumference of the interface between the outer component and inner component and longitudinally along the flow channel. This provides for a continuous production of a tube having a cross-section, as shown for example in FIGS. 2 or 3. Conveniently, the continuous tube may be cooled, solidified and cut to length.

The shape and dimensions of the catheter are predominantly controlled by the design of the extrusion die. For a tubular product such as the inventive catheter, the extrusion die will consist of an orifice with a centered pin within the orifice. The shape of the orifice will determine the shape of the catheter while the shape of the pin will determine the inner shape of the tube. One skilled in the art will recognize that the final size and shape of the catheter is influenced by other factors such as die swell, extrusion rate and post extrusion handling. The inventive catheter is a single channel tube. Preferably, the outer component and the inner component are substantially the same length, more preferably the outer component and the inner component each extend the entire length of the catheter. Preferably, the ends of the outer component and the inner component are coplanar at at least one end, more preferably at both ends, of the catheter. The outer cross-section of the outer component should be smooth, rounded and non-angular, more preferably circular. The inner cross-section of the inner component may be any shape but is preferably non- angular, more preferably is circular. The non-angular cross-section of the outer component minimizes the possibilities of snagging or damaging the body part into which it is inserted. The non-angular cross-section of the inner component minimizes the drag on the flow of fluids through the catheter.

An important aspect of this invention is that the interface cross-section between the inner and outer components is non-circular. Preferably, the interface cross-section comprises at least one salient. The term "salient" refers to a projecting angle or part. Preferably the salient forms an angle although rounded salients (protrusions) are within the scope of this invention. Most preferably, the salients of the interface cross-section form a gear or star shape, for example, such as shown in FIG. 2. However, any shape which is non-circular (e.g., oval) is suitable for use in this invention.

The non-circular interface cross section mechanically interlocks the inner and outer components. This mechanical interlock inhibits rotation of the inner and outer components in relation to each other. As such, this mechanical interlock provides the desired resistance to separation due to torsional forces between the inner and outer components.

The shape of the interface cross-section between the two plastic components is predominantly controlled by the shape of the inner conduit at the point where the two flows merge. Factors which provide more precise control over the shape of the interface cross-section between the inner and outer components include, inter alia: (i) merging the two melt flows as close as possible to the entrance of the extrusion die; (ii) providing for similar flow velocities for the two melt flow streams from the point of merger of the streams; and (iii) using immiscible fluids. Any thermoplastic is usable for the components of the inventive catheter.

Examples of suitable thermoplastics include polyolefins (such as polyethylene, polypropylene etc.), polyvinylchloride, nylons, polyfluorocarbons, thermoplastic polyurethanes, polystyrene, non- vulcanized elastomers, cellulosic resins, acrylic resins and silicones. Advantageously, the materials for each of the components are selected to provide the desired physical characteristics for the inventive catheter. For example, in a preferred embodiment, the outside component is selected to be polyethylene in order to provide the desired flexibility, stiffness and low coefficient of friction for an insemination catheter. The inner component of this embodiment is selected to be a rubbery thermoplastic elastomer such as ethylene vinyl acetate copolymer (hereinafter "EVA"). The EVA provides a higher coefficient of friction which aids in preventing an inserted object (such as the nozzle of a semen tube) from detaching from the catheter.

The coextruded catheter of this invention may be used in any medical procedure such as reproductive procedures, angioplasty, transfusions, or intraveneous administration of fluids, more preferably reproductive procedures. The outer dimensions of the catheter are selected based on the desired use. For example, intravascular catheter tubes typically have diameters of about 0.04 to 0.05 inch. In contrast, for the preferred embodiment of use with reproductive procedures, the catheter diameter can be, and preferably is, much larger. For instance, in catheters for livestock insemination, the outer cross-section of the first component may be transcribed by a circle with a diameter of at least about 0.06, more preferably at least about 0.125, even more preferably at least 0.25 inches. Such a catheter is useful as a means to transfer reproductive samples into, or recover reproductive samples from, the body of an animal, preferably a mammal, more preferably a human, cow, horse, sheep, pig or goat, most preferably a pig. The reproductive sample may be sperm, ovum, oocyte or embryo, most preferably sperm or embryo.

One example of the preferred embodiments of this catheter is for use in the artificial insemination of swine. A catheter, such as shown in FIG. 1, is inserted into a sow or gilt. A container containing boar semen and, typically a culture medium, is attached to the end of the catheter projecting outside of the sow or gilt's body, preferably by inserting a nozzle of the sperm container into the inner channel of the catheter. The sperm culture is then allowed to transfer from the sperm container through the catheter and is deposited in the pig's cervix.

Another example of a preferred application of the inventive catheter is the recovery of ova, oocyte or embryos from swine. In this application, a catheter such as shown in FIG. 1 is inserted into the body of a sow or gilt. A second, smaller diameter catheter is inserted through the channel of the inventive catheter and into the uterus of the sow or gilt. A liquid is transported through the smaller diameter catheter in order to flush out the uterus of the pig. The flushing liquid, along with any entrained ova, oocytes or embryos, is transported out of the pig's body through the inventive catheter. The desired reproductive samples may then be recovered from the flush liquid.

In the most preferred embodiment, the catheter is adapted for use for inseminating pigs as shown in FIG. 1. The catheter tube (11) is straight and relatively rigid. The tube (11) has a diameter of approximately 0.25-0.30 in. and is typically 18-24 inches long. Typically, the catheter maybe fitted with a foam insert (12) at the end of the catheter which is inserted into the sow. The catheter has a cross-section (2), two alternatives of which are represented by FIG. 2 and FIG. 3, respectively.

FIG. 2 represents a catheter having a circular outer component outer cross-section (22) but a non-circular inner component inner cross-section (25). The interface (23) between the outer component (21) and the inner component (24) is a star shape. The outer component (21) of this embodiment is selected to provide mechanical strength and is typically polyethylene. The inner component (24) of this embodiment is selected to provide a high coefficient of friction and is typically EVA. The high friction coefficient provides both a more secure attachment for articles inserted into the catheter and greater resistance to separation of the inner and outer components due to torsional forces. Preferably, the catheter for inseminating pigs has the cross-sections as shown in

FIG. 3. The outer cross-section (32) is circular as is the component inner inner cross- section (34). The outer component (31) is polyethylene and the inner component (34) is EVA. The interface (33) between the outer component (31) and the inner component (34) is a star shape.

Claims

The invention claimed is:

1. A catheter comprising:

(A) a first component comprising an outer tube with an inner cross-section having a non-circular shape; and (B) a second component comprising an inner tube in intimate contact with the outer tube with an outer cross section having a shape identical to the shape of the inner cross section of the first component, wherein the second component is contiguous within the first component such that the inner cross section of the first component coincides with the outer cross section of the second component.

2. The catheter of Claim 1, wherein the non-circular shape of both components comprises at least one salient.

3. The catheter of Claim 1, wherein the second component comprises a material having a higher coefficient of friction that the material of the first component. 4. The catheter of Claim 3, wherein the material of the second component comprises a rubbery thermoplastic.

5. The catheter of Claim 3, wherein the material of the second component is ethylene vinyl acetate copolymer (EVA).

6. The catheter of Claim 1, wherein the first component comprises a thermoplastic resin selected from the group consisting of polyolefins, polyvinylchloride, nylons, polyfluorocarbons, thermoplastic polyurethanes, polystyrene, non- vulcanized elastomers, cellulosic resins, acrylic resins and silicones.

7. The catheter of Claim 6, wherein the thermoplastic resin is a polyolefin.

8. The catheter of Claim 6, wherein the thermoplastic is polyethylene.

. The catheter of Claim 1, wherein

(A) the first component tube further has a length, an outer cross-section, a first end and a second end, wherein both the first and second ends are open; and

(B) the second component tube further has a length, an inner cross section, a first end and a second end, wherein both the first and second ends are open.

10. The catheter of Claim 9, wherein the length of the second component is substantially equal to the length of the first component.

11. The catheter of Claim 9, wherein the first end of the first component is substantially coplanar with the first end of the second component. 12. The catheter of Claim 9, wherein the outer cross section of the first component has a shape that is transcribed by a circle with a diameter of at least 0.125 in.

13. The catheter of Claim 9, wherein the outer cross section of the first component has a shape that is transcribed by a circle with a diameter of at least 0.25 in.

14. The catheter of Claim 1, adapted for use in reproductive procedures, wherein the reproductive procedure is the transfer of reproductive samples into the body of a mammal or the recovery of reproductive samples from the body of a mammal.

15. The catheter of Claim 14, wherein the mammal is a human, cow, horse, sheep, pig or goat.

16. The catheter of Claim 14, wherein the reproductive sample is sperm, ovum, oocyte or embryo.

17. The catheter of Claim 14, wherein the mammal is a pig.

18. The catheter of Claim 1, wherein the second component comprises a thermoplastic resin selected from the group consisting of polyolefins, polyvinylchloride, nylons, polyfluorocarbons, thermoplastic polyurethanes, polystyrene, non-vulcanized elastomers, cellulosic resins, acrylic resins and silicones.

19. The catheter of Claim 18, wherein the thermoplastic resin is a non- vulcanized elastomer.

20. The catheter of Claim 18, wherein the thermoplastic is EVA.