TORQUE RESISTANT TUBING

Abstract: Catheter tubing suitable for medical uses is disclosed, comprising an interior tubular portion (2, 4) and a concentric outer shell (6), wherein said interior portion extends beyond (10) said concentric outer shell (6) on at least one end of the longitudinal axis, and wherein the hardness of the concentric outer shell (6) exceeds the hardness of the interior tubular portion (2, 4), the interior tubular portion (2, 4) further comprising at least two resins co-tapered with respect to each other, the hardness of the innermost (2) of which exceeds the hardness of the outermost (4).

Description: TORQUE RESISTANT TUBING The present invention relates to new improved catheter tubing suitable for medical uses. More particularly, it relates to catheter tubing comprising an interior tubular portion and a concentric outer shell, wherein said interior tubular portion comprises at least two cotapered resins and extends beyond said concentric outer shell on at least one end of the longitudinal axis, and wherein the hardness of the innermost of the two cotapered resins exceeds the hardness of " the outermost resin and the hardness of the concentric outer shell resin exceeds the hardness of the outermost resin of the cotapered interior tubular portion. BACKGROUND OF THE INVENTION Ruiz, U.S. Pat. No. 4,385,635, discloses an angiographic catheter having a soft flexible, pliable, leading tip zone, wherein the catheter is composed of a main reinforced length and an intermediate zone between the tip zone and the main length, the main length being reinforced by an inner tube of a polyamide material and wherein the polyamide is tapered in the intermediate zone to provide a tapered reinforced section tapering distally and uniformly to zero of the tip zone, so that the distal end is of elastomeric material, such as urethane, constituting a soft tip. Flynn, U.S. Pat. No. 4,282,876, discloses multiwall and co-tapered multiwall tubing constructions, wherein either the interior tubular portion or the concentric outer shell comprises a radiopaque composition. Burlis et al., U.S. Pat. No. 3,752,617, relates to the extrusion of tubing having differen characteristics along its axial length. Flynn, U.S. Pat. No. 3,618,614, discloses multiwall surgical tubing comprising relatively thick, transparent tube encased in a relativel thin, visually transparent outer shell. In a preferre embodiment, the thermoplastic material of said outer shel will be a denser, stiffer material than that of the cor material to provide adequate torque resistance to the assembly and to provide the hard, slick exterior properties desired. The prior art illustrates attempts to provide flexible catheter tubing with a soft tip and a stiff body, in order to provide the required degree of insertion and manipulation ease without producing patient trauma in the sensitive internal passageways. Rigidity is required to allow advancement of the catheter by pushing, to allow susceptibility to axial movements of adjustment and to resist twisting or torque forces. Such catheters must also be able to withstand a high bursting pressure. For example r in constructing tubing for use in artificial kidney connections to the patient, it is desirable to have a tube with a stiff end and a flexible end. One method of constructing such tubing in the past has been to chemically remove the plasticizer from one end of the tube. Another method of making such a tube is to take two separate sections of different plastic tubes and fasten them togethe employing a suitable joining process. Neither of thes methods have been completely satisfactory. The chemica removal of plasticizer results in inconsistent levels o flexibility in the end of the tube, and fastened tube section possess the inherent risk of separation, causing interna injuries to the patient. As shown above, some catheter tubing construction found in the art have also attempted to increase resistance t torque by co-tapering different resins. While such a metho may have the effect of providing enhanced torque resistance o one end of the tube, the torque resistance diminishes as th co-tapering progresses. As a result, co-tapering as a metho to increase torque resistance, when used ■ alone, is no sufficient to provide torque resistance throughout the entir non-tip length of the tubing. Thus, such tubing is no adequate for complicated applications where high torqu resistance ' is required throughout the length of the tubing t provide ease of application.through tortuous body passages Also, co-tapering attempts such as Ruiz, U.S. Pat. No 4,385,635, utilize hard materials for the interior portion of the tubing, but such hard materials are not receptive to guide wire control . The catheter tubing constructions found in the art also do not provide the combination of torque resistance and a soft tip, because the soft tip has generally inconsistent properties and is a solid, non-connected part of the tubing. For instance, neither Flynn, U.S. Pat. No. 4,282,876, nor Flynn, U.S. Pat. No. 3,618,614, provide a soft tip for the tubing. Surprisingly, catheter tubing comprising a hard outer shell and a soft interior portion provides the resistance to torque required for insertion through tortuous body passages, without diminished flexibility or diminished frictional effect. Furthermore, such constructions, by utilizing soft interior portions, are more responsive to guide wire control than are hard interior portions. Additionally, constructions in which the soft interior portion extends beyond the hard outer shell obviates the need for attaching a soft tip to the tubing, thus avoiding the risk of separation of element. This is precisely the opposite approach than was taken by Ruiz, who emphasizes the desirability of having a soft outer shell. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood by reference to the accompanying drawing in which is shown an enlarged, fragmentary cross-sectional view along the longitudinal axis of a typical tube of this invention having a co-tapered interior tubular portion comprising an innermost resin (1) and an outermost resin (2) and a concentric outer shell, wherein said interior portion extends beyond the concentric outer shell on one end of the longitudinal axis, and wherein the hardness of the innermost resin (1) and that of the concentric outer shell resin exceeds the hardness of the outermost resin (2) of the tubular interior portion. SUMMARY OF THE INVENTION In accordance with the present invention there i provided catheter tubing suitable for medical uses, comprisin an interior tubular portion and a concentric outer shell wherein the interior portion extends beyond the concentri outer shell on at least one end of the longitudinal axis, an wherein the interior tubular portion comprises a firs innermost resin (1) and a second outermost resin (2), th tubing having a first point along its length and a secon point along its length spaced apart from said first point, th thickness of the first resin (1) tapering as it passes fro the first point to the second point and the thickness o second resin (2) tapering inversely to the taper of the firs resin (1) as it passes from the first point to the secon point, and wherein the hardness of the innermost resin (1 exceeds the hardness of the outermost resin (2) in th interior tubular portion and the hardness of the concentri outer shell resin exceeds the hardness of the second resi (2). Preferred features of the invention comprise cathete tubing as defined above wherein the interior tubular portio extends beyond the shell by at least about 1.0 inches, an especially such tubing wherein the interior tubular portio extends beyond the shell by from about 1.0 to about .20. inches. Also preferred iε catheter tubing as defined abov wherein the first innermost resin (1) comprises a resin havin a Shore D hardness in the range of about 45 to about 80, an wherein the second outermost resin (2) comprises a resi having a Shore A hardness in the range of about 40 to abou 100, special mention being made of catheter tubing wherein th concentric outer shell comprises a resin having a Shore hardness in the range of about 45 to about 85. Also contemplated by the invention is catheter tubin as defined above wherein the interior tubular portion and th concentric outer shell are essentially of uniform diamete throughout the length of the tubing, excluding the extensio cf the interior tubular portion and wherein the inner shell has an outer diameter of from about 0.030 tc about 0.072 inches and the outer 'shell has a wall thickness of from about 0.002 to about 0.010 inches. Among the embodiments of the invention are catheter tubings as defined above wherein the first innermost resin (1) comprises a resin selected from nylon, high density polyethylene, polypropylene, or a mixture of any of them; the second outermost resin (2) comprises a resin selected from polyurethane, an extrudable polyvinyl chloride, and medium density polyethylene or a mixture of any of them; and the concentric outer shell comprises a resin selected from a fluoropolymer, high density polyethylene, ultra high density polyethylene, polycarbonate, nylon or a mixture of any of them; and special mention is made of such tubing wherein the first innermost resin (1) comprises nylon, the second outermost resin (2) comprises polyurethane, and the concentric outer shell comprises high density polyethylene. The invention further contemplates providing catheter tubings as above defined wherein the second outermost resin (2) further comprises an effective amount of a radiopacifie comprising an ester of a polyiodobenzoic acid, special mentio being made of such catheter tubing wherein the ester comprise butyl 2,3,4,6- tetraiodobenzoate. In a further me or aspect the invention proyide catheters formed by heat shaping the tubing defined above. DETAILED DESCRIPTION OF THE INVENTION Polyurethanes are known to those skilled in the art They are described in the Modern Plastics Encyclopedia, 198 Edition, McGraw Hill, New York, pages 136 - 138. They ar also commercially available from a number of suppliers, suc as Dow Chemical as Pellethane 2363 Series 80 A-65 D and 75 (therein and herein, A and D designates Shore Hardness, a wel known measurement to those skilled in the art of plastic resi formulation: A Series being lower hardness than D Series an the numerical values within each Series increasing wit hardness) and"ISOPLAST" RTPU Resins, and also products fro B.F. Goodrich Co. tradenamed ESTANE Resins and from Thermedic Co. tradenamed "Tecoflex" Resins. Polyvinyl chloride is described in the Moder Plastics Encyclopedia, Id., pages 118 - 127. It is als commercially available from a number of suppliers, such a B.F. Goodrich tradenames GEON 3400 and 3500 Series, as well a Borden Co. and Union Carbide Co. Medium density polyethylene is described in the Moder Plastics Encyclopedia, Id., pages 63 - 74. It is als commercially available from a number of suppliers, such a U.S.I. Chemicals Co., Dow Chemical Co., Chevron Co., an DuPont Co. High density polyethylene is described in the Moder Plastics Encyclopedia, Id., pages 63 - 74. It is als available from a number of suppliers, such as U.S.I. Chemical Co., Chevron Co. , and DuPont Co.. Ultra high density polyethylene is described in th Modern Plastics Encyclopedia, Id., pages 63 - 74. It is als commercially available from a number of suppliers, such a Himont U.S.A., and Celanese-Hoechst Co. Nylon is described in the Modern Plastic Encyclopedia, Id., pages 30 - 31. It is also commerciall available from a number of suppliers, such as DuPont Co. Monsanto Co. and BASF Co. Fluσroplastics are described in the Modern Plastic Encyclopedia, Id., pages 24 - 26. They are also commerciall available from a number of suppliers, such as Dupont Co. tradenamed "Teflon" PTFE Resins, and from the Celanese-Hoechs Co. Polycarbonate is described in the Modern Plastic Encyclopedia, 'Id., pages 38 - 41. It is also commerciall available from a number of suppliers, such as General Electr Company, tradenamed "Lexan" Resins and from Mobay Corp. tradenamed "Makrolon" Resins. Butyl tetraiodobenzoates are described in Flyn U.S. 4,282,876, and references incorporated therein. The formulations will be aided in some cases by tfe inclusion of lubricants such as metallic stearate, stea-ri acid, paraffin wax, mineral oil, etc. in conventional amounts See U.S. Pat. No. 3,645,955, incorporated herein to minimiz an unnecessarily detailed description. The compositions are prepared and converted in useful products by techniques well known to those skilled I the art. In one manner of proceeding, the fluid ingredient e.g. esters of iodobenzoic acid, are blended with the powder solids, e.g., polyurethane resin, nylon resin, and the lik and, optionally, stabilizers and plasticizers, and then fus and mixed under pressure, e.g. in a Banbury-type mixer, a discharged. Conventional 2-roll compounding techniques c also be used. The composition is cooled and granulated. If extrusions are to be made, the granulat composition can be fed to a conventional machine, for exampl one or more one-inch Killion-type single screw extrude fitted to a bi-orifice extrusion head of a type shown Figure 6 of U.S. Patent no 4,282,876, and operated at suitable temperature, e.g., 300 degrees Fahrenheit, and t tubing is formed at a suitable rate, e.g, 7,000 - 10,000 fe per hour and cut automatically to length. Referring to the accompanying drawing, t thermoplastic composition for the innermost layer 2 of t interior tubular portion is discharged from the inner annul orifice of the bi-orifice extrusion head (not shown) by first extruder at a decreasing uniform rate. The outermo layer 4 is discharged from the concentric outer araan orifice of the extruder head (also not shown), thermoplastic composition therefor being supplied by a sec extruder at an increasing rate inversely proportional to declining rate of the first extruder. This provides an in tubular portion with innermost layer 2 tapering downward thickness while the outermost layer 4 is tapering upward thickness. Air pressure provides support for thermoplastic walls and assists in defining lumen 8 oαr extrusion. The increasing and decreasing rates of extrusion for innermost and outermost.walls- 2 and 4 may be provided over any convenient length of time cycle to provide continuous lengths of the co-tapered inner tubular portion. The exterior shell 6 can be put in place in any convenient manner, e.g., such as by slipping on a tube of heat shrinkable thermoplastic material and then heating to shrink it in place, or by providing a heated film coating die of an entirely conventional type immediately downstream of the bi-orifice die in which the cotapered inn The end of the extends beyond the outer shell ■ can be formed by techniques known to those skilled in the art. In one manner of proceeding, the end is centerless ground to remove the outer shell, thus exposing the soft interior. Other methods can also be used, such as using the aforementioned film coating die and terminating extrusion of the outer/ coating 1 6 at any desired length short of the end to produce soft tip 10. The tubing of this invention can be used for man various and diverse purposes, e.g., heart catheters, stomac tubes, nasal tubes, thoracic catheters, and other cathete tubings suitable for medical uses. However, from the foregoin description and the following examples and by reference t other well known teachings, the methods and modes by which th tubing of this invention can be formed into various othe articles will be readily apparent to those skilled in the art. The medical grade tubing prepared as described i the following examples will be non-toxic, non-reactive t tissue and may be sterilized -by gas or cold sterilizatio solutions. The tubing is generally dispensed as such and th surgeon or trained technician will form it into catheters fo rσentgenography. For maximum convenience, the tubing can als be preformed into articles and dispensed, e.g., as steril disposable intravenous catheters. By way of illustration, catheters according to thi invention will be fabricated from the medical-surgical tubin of the invention by operations comprising tip forming, ti finishing, shaping, side hole forming, and flaring. Before use they will be sterilized. Those skilled in the art will prepare a variety of tip shapes. For internal mammary and axillary artery branches a three-quarter loop is formed in the distal end. For percutaneous arteriography and cerebral arteriography via femoral, a 45 - 60 degree smooth bend will be formed in the distal end. Selective renal arteriography and celiac arteriography requires a one-half loop. Hepatic venography uses about a seven-eighths loop. For trans-septal left-heart catheterization via the femoral vein, a three-quarter loop, like that above-described for mammary branches, but larger, Is formed. On the other hand, abdominal aortography via brachiai artery uses a rather large, one-third closed loop and thoracic aortography via the femoral artery uses the same shape but bigger. For lumbar aortography via the femoral artery the tip is straight out. For coronary arteriography, the end of the catheter is looped. The heavier-walled tubing is formed into such typical shapes by inserting a forming wire within the tubin and heating in a tiny flame until visibly softened. B pulling from both ends the tubing is drawn to the wire an forms a uniform lumen around it. The tip is formed b cutting, e.g., with a razor blade, at the drawn diameter an is smoothly rounded in the flame. Next a precurved wire i inserted into the tube which is then immersed in hot wate until the tubing softens. Quenching in cold water will caus the catheter to conform to the curve of the forming wire Side hole "or eye punching is accomplished by rotating sharpened hole punch cannula under slight pressure. The hole should be large enough to expel contrast media without exces build up of injection pressures but should be no larger tha 2/3 of the internal diameter of the tubing. The catheter i cut to the preselected length and flared. Heating in a smal flame and rotating on a flaring tool produces a flare of th desired size. The catheter can be bonded at the flare, e.g. with epoxy cement, to a suitable hub. On the other hand, a adapter can be used to screw the catheter to a Luer-Lo stopcock, or the like. DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples illustrate the presen invention but are not intended to limit the claims in an manner whatsoever. Example 1 A co-tapered multiwall tube in made and covered wit a heat shrunk outer shell. The innermost and outermost layer are extruded concurrently and concentrically through annula concentric orifices of a multiorifice extruder so as to bon the inner and outer layers together. The co-tapering of th inner and outer layers is obtained by varying the rate o extrusion of the inner and outer layer. See the above mentioned Burlis et al patent and Flynn, U.S. 4,282,876. The rate of extrusion of the inner layer gradually varies fro a first rate to a second rate while the rate of extrusion o the outer layer gradually varies inversely for the inne layer. The inner layer comprises nylon having a hardness i the range of Shore D 46-78. The outermost layer comprise polyurethane having a hardness in the range of Shore A 55-95 Next a sleeve of heat shrinkable fluoroplasti (polytetrafluoroethylene jiaving a hardness in the range o Shore D 50-65) is slipped e er the cotapered tubing and th multiwall tubing is heated to shrink the outer tube and for a shell. Finally a portion of the shell is removed b centerless grinding from one end of the tube to leave a tw inch end comprising the exposed interior tubular portion a shown in the drawing. The outside diameter of the inner tubular portion i about 0.050 ' inches and the wall thickness of the outer shel is about 0.004 inches. Surgical catheters are formed from lengths of th tubing, for example 40-inch lengths, and they exhibit a degre of flexability and softening progressively changing from on end to the other. Such medical surgical catheters have manipulative characteristics which are advantageously employed by the surgical operator in inserting, withdrawing and controlling the catheter. EXAMPLE 2 The procedure of Example 1 is repeated except that the outermost layer of the inner tubular portion is substituted with a 55 to 65 Shore D hardness thermoplastic polyurethane containing 20 parts per 100 parts by weight of composition of n-butyl 2,3,4,6-tetraiodobenzoate. Medical surgical tubing according to this invention is obtained which, in addition to posessing the manipulative advantages described above, is highly radiopaque and has advantageously improved tensile properties over known radiopacified multiwall radiopacified tubing. The above-mentioned patents, publications and test methods are incorporated herein by reference. The foregoing detailed description will suggest man obvious variations to those skilled in the art. For example, instead of butyl tetraiodobenzoate, a mixture thereof with a ester of 2,5-diodobenzoic acid can be used. Instead o polyurethane, a flexible poly(vinyl chloride) resin can b used in the outermost layer of the inner tubular portion. Instead of poly(tetrafluoroethylene) in the shell, there ca be used high density polyethylene, ultra high densit polyethylene, polycarbonate resin, or high hardness nylon Instead of nylon in the innermost layer of the interio tubular portion, there can be used high density polyethylene or polypropylene. Any of the layers can also comprise mixe such resins. All such obvious modifications are within th full intended scope of the appended claims.

Claims: CLAIMS: 1. Catheter tubing suitable for medical uses, comprising an interior tubular portion and a concentric outer shell, wherein said interior portion extends beyond said concentric outer shell on at least one end of the longitudinal axis, and wherein said interior portion comprises a first innermost resin (1) and a second outermost resin { 2 ) , said tubing having a first point along its length and a second point along its length spaced apart from said first point, the thickness of said first resin (1) tapering as it passes from said first point to said second point and the thickness of said second resin (2) tapering inversely to the taper of said first resin (1) as it passes from said first point to said second point, and wherein the hardness of the innermost resin (1) exceeds the hardness of the outermost resin (2) in the interior tubular portion and the hardness of the concentric outer shell exceeds the hardness of said second resin (2). 2. Catheter tubing as defined on Claim 1 wherei said interior tubular portion extends beyond said shell by a least about 1.0 inches. 3. Catheter tubing as defined in Claim 2 wherein sai interior tubular portion extends beyond said shell by fro about 1.0 to about 20.0 inches. 4. Catheter tubing , as defined in Claim 1, wherei said first innermost resi.n (1) comprises a resin having Shore D hardness in the range of about 45 to about 80, an wherein said second outermost resin (2) comprises a resi having a Shore A hardness in the range of about 40 to abou 100. 5. Catheter tubing as defined in Claim 4, wherei said concentric outer shell comprises a resin having a Shor D hardness in the range of about 45 to about 85. 6. Catheter tubing as defined in Claim 1, wherein the interior tubular portion and the concentric outer shell are essentially of uniform diameter throughout the length of the tubing, excluding the extension of said interior tubular portion and wherein said inner shell has an outer diameter of from about 0.030 to about 0.072 inches and said outer shell has a wall thickness of from about 0.002 to about 0.010 inches. 7. Catheter tubing as defined in Claim 1, wherein said first innermost resin (1) comprises a resin selected from nylon, high density polyethylene, polypropylene, or a mixture of any of them; said second outermost resin (2) comprises a resin selected from polyurethane, an extrudable polyvinyl chloride, and medium density polyethylene or a mixture of any of them; and said concentric shell comprises a resin selected from a fluoropolymer, high density polyethylene, ultra high density polyethylene, polycarbonate, nylon or a mixture of any of them. 8. Catheter tubing as defined in Claim 7, wherein said first- innermost resin (1) comprises nylon, said second outermost resin (2) comprises polyurethane, and said concentric outer shell comprises high density polyethylene. 9. Catheter tubing as defined in Claim 1 wherein said second outermost resin (2) further comprises an effective amount of a radiopacifier comprising an ester of a polyiodobenzoic acid. 10. Catheter tubing as defined in Claim 9, wherein said ester comprises butyl 2,3,4,6-tetraiodobenzoate. 11. A catheter formed by heat shaping the tubing defined in Claim 1. AMENDED CLAIMS [received by the International Bureau on 25 August 1992 (25.08.92); original claim 11 deleted; original claims 1,2,4,7,8 and 9 amended; new claim 12 added; remaining claims unchanged (3 pages)] 1. Catheter tubing suitable for medical uses, comprising interior tubular portion and a concentric outer shell, wherein said interior portion extends beyond said concentric outer she on at least one end of the longitudinal axis, and wherein said interior portion comprises a first innermost resin (2) and a second outermost resin (4) , said tubing having a first point along its length and a second point at or beyond said concentr outer shell (6) along its length spaced apart from said first point, the thickness of said first resin (2) tapering in a decreasing fashion as it passes from said first point to said second point and the thickness of said second resin (4) taperi inversely to the taper of said first resin (2) as it passes fr said first point to said second point, and wherein the hardnes of the innermost resin (2) exceeds the hardness of the outermo resin (4) in the interior tubular portion and the hardness cf concentric outer shell exceeds the hardness of said second res (4) . 2. Catheter tubing as defined on Claim 1 wherein said inte rior tubular portion extends beyond said shell by at least abo l.o inch. 3. Catheter tubing as defined in Claim 2 wherein said inte rior tubular portion extends beyond said shell by from about i. to about 20.0 inches. 4. Catheter tubing as defined in Claim 1, wherein said firs innermost resin (2) comprises a resin having a Shore D hardness in the range of about 45 to about 80, and wherein said second our er ost resin (4) comprises a resin having a Shore A hardness in the range of about 40 to about 100. 5. Catheter tubing as defined in Claim 4, wherein said con- centric outer shell comprises a resin having a Shore D hardness in the range of about 45 to about 85. 6. Catheter tubing as defined in Claim 1, wherein the inte- rior tubular portion and the concentric outer shell are essen- tially of uniform diameter throughout the length of the tubing, excluding the extension of said interior tubular portion and wherein said inner shell has an outer diameter of from about 0.030 to about 0.072 inches and said outer shell has a wall tiiic nesε of from about 0.002 to about 0.010 inches. 7. Catheter tubing as defined in Claim 1, wherein said firs innermost resin (2) comprises a resin selected from the group COΪ sisting of nylon, high density polyethylene, polypropylene, or a mixture of any of them; said second outermost resin (4) comprise a resin selected from the group consisting of polyurethane, an extrudable polyvinyl chloride, and medium density polyethylene and a mixture thereof? and said concentric shell comprises a resin selected from a fluoropolymer, high density polyethylene, ultra high density polyethylene, polycarbonate, nylon and a mix- ture thereof. 8. Catheter tubing as defined in Claim 7, wherein said firs innermost resin (2) comprises nylon, said second outermost resin (4) comprises polyurethane, and said concentric outer shell co - prises high density polyethylene. 9. Catheter tubing as defined in Claim 1 wherein said secon outermost resin (4) further comprises an effective amount of a radiopacifier comprising an ester of a polyiodobenzoic acid. 10. Catheter tubing as defined in Claim 5, wherein said ester comprises butyl 2,3 ,4,6-tetraiodobenzoate. 12. A catheter, said catheter being produced by the process of heat shaping the catheter tubing defined in Claim 1.

Inventors: FLYNN VINCENT J, FLYNN, VINCENT, J.
Applicants: FLYNN VINCENT J, FLYNN, VINCENT, J.
Application year: 1991
Main classification: A61M25
IPC codes: A61M25