EP1545684A1 - Ballon a resistance elevee et a douceur sur mesure - Google Patents

Ballon a resistance elevee et a douceur sur mesure

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Publication number
EP1545684A1
EP1545684A1 EP02766060A EP02766060A EP1545684A1 EP 1545684 A1 EP1545684 A1 EP 1545684A1 EP 02766060 A EP02766060 A EP 02766060A EP 02766060 A EP02766060 A EP 02766060A EP 1545684 A1 EP1545684 A1 EP 1545684A1
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EP
European Patent Office
Prior art keywords
balloon
polymer
temperature
tubing
blank
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP02766060A
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German (de)
English (en)
Inventor
Brooke Ren
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St Jude Medical ATG Inc
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St Jude Medical ATG Inc
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Publication date
Application filed by St Jude Medical ATG Inc filed Critical St Jude Medical ATG Inc
Publication of EP1545684A1 publication Critical patent/EP1545684A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L29/00—Materials for catheters, medical tubing, cannulae, or endoscopes or for coating catheters
    • A61L29/04—Macromolecular materials
    • A61L29/06—Macromolecular materials obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds

Definitions

  • This invention relates to balloons, balloon catheters, and methods of making balloons or balloon catheters that are useful in medical dilatation procedures.
  • medical dilatation procedures open obstructed blood vessels or expand medical devices, and are often done in either small body passageways or with very small medical devices.
  • the balloon or balloon catheter should have high strength and an extremely thin wall for flexibility and a low profile.
  • a balloon catheter is a thin, flexible length of tubing having a small inflatable balloon at a desired location along its length, such as at or near its tip.
  • Finding balloon materials, however, that offer high strength, flexibility, toughness, and predictable size under inflation pressure has been a challenge.
  • PET Polyethylene terephthalate
  • PET balloons are well known non-compliant materials that can be used to make strong and rigid balloon catheters.
  • the PET balloon's strength arises from the polymer's structure and high molecular orientation resulting from processing.
  • PET balloons possess especially high tensile strength and tightly controllable inflation characteristics, they also have several undesirable properties. For instance, the material's stiffness makes it difficult to fold the balloon.
  • PET balloons have a tendency to form pin holes or other signs of weakening, which make them easy to rupture.
  • a balloon made primarily of PBT may be formed by first, axially stretching the extruded tubing that eventually becomes the balloon while inflating the tubing at a pressure low enough to avoid radially expanding the tubing beyond its original non-distended diameter, and second, blowing the stretched tubing at a higher temperature.
  • adding small amounts of boric acid to PBT improves extrusion clarity and processability by reducing crystallinity after extrusion.
  • Zhang et al . in PCT application WO 02/26308 (“the ' 308 application”) teach that defects in polymeric materials, such as PBT, PET, and polyamides, may be reduced by post-extrusion modification.
  • the modification includes, first, axially stretching and radially expanding the extruded tubing that eventually becomes the balloon, and second, blowing the stretched tubing at an elevated temperature.
  • the x 308 application further teaches that by using the post-extrusion modification a balloon may be tailored to obtain different balloon diameters when starting from a given wall thickness of extruded tubing. Neither reference, however, teaches or suggests how to attain high balloon hoop tensile strength while achieving good flexibility and toughness .
  • the present invention provides a group of semi- crystalline, thermoplastic polymeric materials that when processed correctly yields desirable attributes such as high hoop strength, flexibility, and puncture resistance. [0010] It is an object of this invention to provide a method for producing a balloon, which exhibits high dilatation force, balanced bi-axial properties, and easy re-folding after dilatation.
  • the processing steps of the invention enable fast crystallization materials, which are generally' difficult to process according to prior art methods, to be made into balloons for use in medical devices.
  • This method entails operating balloons below the glass transition temperature of the balloon material, while retaining the material's strength, toughness, and flexibility characteristics.
  • Such a balloon may be comprised of semi-crystalline polymers composed of small spherulites .
  • FIG. 1 plots the balloon stiffness factor as a function of the temperature at which it is tested.
  • FIG. 2 illustrates the effect of temperature on the balloon hoop tensile strength.
  • FIG. 3 illustrates the effect of temperature on the rate of polymer crystallization.
  • polysemi-crystalline polymer refers to polymers that exhibit some degree of crystalline order (e.g., a regularly repeating arrangement of atoms in three dimensions) .
  • Semi-crystalline polymers would include, for instance, acetal, nylon, PE, polypropylene, and polyester.
  • amorphous polymers have polymer chains that are randomly entwined, creating a homogeneous and isotropic material in the bulk.
  • Amorphous polymers would include, for example, polycarbonate, polystyrene, acrylonitrile-butadiene- styrene (ABS) , styrene acrylonitrile (SAN) , and PVC.
  • thermoplastics refers to materials that become soft and moldable when heated and change back to solid when allowed to cool. Examples of thermoplastics include acetal, acrylic, cellulose acetate, nylon, polyethylene, polystyrene, vinyl, and polyester. In contrast, "thermoset” plastics, such as epoxies, phenolics, and unsaturated polyesters, develop cross links during processing. The cross linking prevents relative movements between the chains and makes the material a hard solid. Thus, heating a thermoset material degrades the material so that it cannot be re- processed satisfactorily.
  • Glass transition temperature refers to the lowest glass transition temperature displayed by the material.
  • Cold forming refers to a process of deforming a polymeric tubing by axially stretching and optionally radially expanding with internal pressure the tubing while below its glass transition temperature.
  • Thermoforming refers to a process of producing plastic parts under pressure and elevated temperature (e.g., above the polymer's glass transition temperature) .
  • a balloon is "compliant" if it is able grow in volume and stretch at least 5% beyond its non-distended balloon diameter at 200 psi .
  • the "non-distended balloon diameter” corresponds to the nominal diameter of the balloon.
  • the stiffness of a balloon may be quantified by a "stiffness factor.” As described by G. Grover, M. Sultan, and S. Spivak in “A Screening Technique for Fabric Handle,” JTI, Vol. 84(3), T486 (1993), the stiffness factor of a balloon may be measured by attaching the balloon to a Chatillon force gauge and pulling it through a hole.
  • the stiffness factor reported herein is measured at ambient temperature (i.e., 22°C) using a 2 mm hole (approximating the diameter of an anastomosis connector) with a balloon that has been deflated and which has a non-distended diameter that is about 3 mm.
  • the stiffness factor is calculated by dividing the pull-through force (measured in pounds) by twice the thickness of the balloon wall (measured in inches) . The higher the calculated stiffness factor number, the stiffer the balloon.
  • This test method is commonly referred to as a "ring test," and has been widely used, as shown in "Measuring Film Stiffness," Modern Packaging 2, p. 121 (1963) and “Quantitative Measurement of the ⁇ Feel' of Fabric,” NASA Tech.
  • the crystallization time is a function of both nucleation rate and crystal growth rate.
  • Polymeric materials having a “fast crystallization time” refers to materials that have a fast rate of nucleation and a slow crystal growth rate relative to the nucleation rate.
  • the “crystallization time” is the minimum crystallization half-time at the temperature that the material crystallizes the quickest. As described in U.S. patent 5,039,727, incorporated herein by reference, the crystallization time is measured by placing a small portion of polymer on a slide glass, covering it with a cover glass, and heating the polymer until it melts.
  • Viscoelasticity refers to the changes in a polymer's mechanical properties as a function of temperature and strain rate .
  • Polymers described as viscoelastic can display the properties of either an elastic solid and/or viscous fluid, depending on the temperature or time scale at which the polymer is observed. More specifically, at temperatures below T g , the polymer's behavior is predominantly elastic. At temperatures above T g , however, the polymer's behavior is predominantly viscous.
  • the rate a polymer is deformed can significantly affect the mechanical properties exhibited by a polymer. For instance, reducing the rate that a polymer is deformed can cause the polymer to demonstrate a viscous behavior similar to that exhibited by the same polymer at higher temperatures .
  • a polymer In the transition region between the elastic state and viscous state, a polymer is in a "leathery state.”
  • the leathery state of a polymer refers to a state near the glass transition temperature in which the mechanical behavior of the polymer becomes sluggish. In this leathery state, the behavior from both the elastic and viscous states significantly contributes to the mechanical response of the material .
  • a polymer in a leathery state can be extensively deformed, it generally will slowly return to its original state when the stress is removed. In the leathery state, viscous sliding of the polymer chains occurs with difficulty, and the polymer exhibits a high elastic hysteresis.
  • melt index measures the rate of extrusion of thermoplastics through an orifice. The M.I., as reported herein, were measured using the ASTM D 1238 testing procedure.
  • Modulus provides a measure of a material's resistance to deformation as a function of stress.
  • the modulus of a material is calculated by measuring the change in stress as a function of strain.
  • the "hoop ratio” is the ratio of the . predetermined balloon diameter to the original diameter of the extruded tubing. [0036] The hoop tensile strength of the balloons reported herein were measured at ambient temperature using the well known membrane equation:
  • HTS (burst pressure (psi) ) x (non-distended balloon diameter)
  • HTS the balloon hoop tensile strength
  • catheter balloons are needed to deliver a radial force to expand either a medical device or a blood vessel.
  • a high internal pressure is applied to a balloon to expand a connector.
  • the balloon should have sufficient strength to avoid bursting at high internal pressure and a predictable balloon hoop tensile strength.
  • the balloon be flexible, puncture resistant, and have thin walls.
  • Semi- crystalline polymers processed according to the present invention have been found to exhibit the desired properties that make them advantageous for high internal pressure applications.
  • balloons of the invention may be suited for medical applications not requiring repeated inflation of a balloon, where the balloon's ability to reach the same diameter at the same pressure during repeated inflation-deflation cycles is not critical.
  • Polymeric materials that exhibit the ability to follow the same stress-strain curve during repeated application and relief of stress are described as having a high degree of elastic stress response.
  • the elastic stress response may be determined according to the method described in U.S. Patent 6,283,939. The larger the calculated elastic stress response, the less repeatable the diameter attained by a balloon inflated to a particular pressure. In one embodiment, the balloons of the invention exhibit an elastic stress response that is greater than 5. [0040] As further discussed below, the morphology and crystal size of semi-crystalline polymers can heavily influence a number of the polymer's properties, including material flexibility (i.e., stiffness), strength, toughness, and glass transition temperature (T g ) .
  • Semi- crystalline polymers of the invention are preferably processed to form small spherulite crystal morphology.
  • spherulites grow radially from a nucleation site, such as a single crystal or defect. They may be obtained from either a concentrated solution or from melt. Polymers that are melt crystallized commonly develop as spherulites. Thus, crystallizing the polymer from melt is the preferred method of crystallization in the invention. Polymers composed of small spherulites are preferred because they are usually more flexible than comparable polymers made of large spherulites, which are more difficult to fold (i.e., stiffer) and less puncture resistant.
  • the spherulites are smaller than about 20 microns when measured with a polarized light microscope or scattering X-ray microscope.
  • the morphology and extent of crystallinity obtained depends, in part, on the crystal nucleation rate and crystal growth rate. Slow nucleation and fast crystal growth tend to result in a small number of large spherulites, whereas fast nucleation and slow crystal growth tend to result more preferably in a larger number and density of small spherulites. Because spherulites tend to grow until they impinge upon another spherulite or other surface interface that interferes with further crystal growth, suitable materials for use in the invention preferably nucleate spherulites at a high enough concentration such that each spherulites does not have the ability to grow too large.
  • the spherulites in the invention are less than about 20 microns in the longest dimension.
  • a nucleating agent may be added to facilitate nucleation of spherulites, certain agents may prompt, upon exposure to human tissue, an undesirable reaction in the human body.
  • the selected polymer preferably nucleates quickly enough so that the addition of a nucleating agent is not necessary.
  • balloons made from materials that crystallized faster tend to exhibit greater flexibility when formed according to the invented process.
  • the balloon generally has a stiffness factor of less than about 100 lbs/inch. In an alternative preferred embodiment, the balloon has a stiffness factor of less than about 75 lbs/inch.
  • the rate a polymer crystallizes is influenced by a number of factors, including the length of the polymer chain, size of the side chains connected to the polymer backbone, molecular weight, and processing conditions. Because long chain polymers have order on long length- scale regions, they usually nucleate faster than shorter chain polymers, allowing for a faster crystallization time. Bulky side chains off the backbone of the polymer, however, can slow crystallization by reducing the polymer's mobility for crystal growth. Crystal growth can also be slowed by lowering the temperature or may be even quenched by reducing the temperature to below the T g to stop the molecular diffusion of polymer chains to the crystal growth surface.
  • the polymer has a crystallization time of less than about 20 seconds. In an alternative preferred embodiment, the polymer has a crystallization time of less than about 10 seconds. In a further alternative embodiment, the polymer has a crystallization time of less than about 5 seconds. In another alternative embodiment, the polymer has a crystallization time of less than about 3 seconds.
  • selecting a semi-crystalline polymer with certain functional groups that create secondary intermolecular bonds between the polymer chains is among the ways one can improve the extent to which the polymer crystallizes. Secondary intermolecular bonds can help make the polymer chains pack tighter. In addition to improving the extent and rate of crystallization, secondary intermolecular bonds, such as hydrogen bonding and dipole-dipole interactions, among functional groups can contribute to the polymer's mechanical strength. Examples of polymers that have strong attractive chain interactions include, but are not limited to, polyester, polyamide, polyurethane, polyetheretherketone, and polyimide .
  • hydrogen bonding can play a significant role in the crystallization process, and in some instances, may improve the polymer's mechanical strength.
  • Polymeric materials to be used in the two-step forming process of the invention are preferably held together in part by secondary intermolecular bonds that are weaker than typical hydrogen bonding forces (see Table 2) .
  • the strongest secondary intermolecular bonds of the polymer selected for use in the invention are dipole-dipole interactions between polar functional groups in the polymer. It is believed that intermolecular attraction between polymeric chains as a result of hydrogen bonding may overcome the beneficial effect of the two-step forming process.
  • the strongest secondary intermolecular bonds in the polymer are preferably and predominantly dipole-dipole interactions between polar functional groups of the polymer.
  • Table 2 Secondary Intermolecular Bond Energy
  • polymers may be good candidates for use in the invention based on their rapid crystallization and relatively high material strength, which arises in part from the dipole- dipole interaction between polar functional groups of the polymeric chain.
  • PBT polybutylene terephthalate
  • PBN polybutylene naphthalate
  • PTT polytrimethylene terephthalate
  • PTN polytrimethylene naphthalate
  • Copolymers of PTT, PBN, or PTN with polyethers are further examples of materials that may be used.
  • PBN may be used as a homopolymer for a single layer balloon.
  • Other polymers not listed above may also be used in the invention provided the predominant secondary intermolecular bonds in the polymer come from dipole- dipole interaction between polar functional groups and the polymer has an adequate nucleation rate and crystal growth rate properties to result in a high density of spherulite crystals, yielding a strong and flexible polymeric material.
  • high molecular weight polymers are more advantageous than low molecular weight polymers.
  • High molecular weight polymeric balloons of the invention tend to be more flexible and have a higher hoop tensile strength than balloons made with low molecular weight polymers.
  • higher molecular weight polymeric balloons (reflected by a lower melt index in the last three rows of Table 3) are less crystalline (reflected by a lower enthalpy) but more flexible (reflected by a lower stiffness factor) than the low molecular weight polymeric balloon formed from the material in the first row of the table.
  • the molecular chains of the polymer can grow to such an extent that they become entangled with other polymer chains and become unable to slip along each other.
  • This entanglement makes the polymer chains difficult to untangle, and accordingly makes the polymer stronger and more resilient to stress and strain.
  • chain entanglement advantageously does not increase the material's stiffness.
  • the M.I. corresponding to the point where the material achieves the best flexibility and hoop tensile strength may be referred to as the "entanglement point .
  • the entanglement point depends on the specific composition of the polymer. PBT balloons of the invention, for example, have an entanglement point at an M.I. around 10.
  • the crystallinity and stiffness start to increase. As shown in the last two rows of Table 3, as the molecular weight further rises beyond the entanglement point, the polymer exhibits increasing crystallinity accompanied by a loss in flexibility.
  • Intrinsic viscosity may be used as an indicator of molecular weight. Generally, the higher the intrinsic viscosity, the higher should be the molecular weight of the polymer.
  • the balloon is made from a material that has an intrinsic viscosity of between about 0.8 and about 1.5.
  • the balloons of the invention provide a comparable high modulus but with improved flexibility and puncture resistance as a result of the small spherulites and chain entanglement.
  • decreasing the T g would be another way to increase flexibility, as shown by the black data points joined by the sloping solid black line in FIGS. 1-2, the advantage gained from the improved flexibility would be outweighed by the loss of balloon hoop tensile strength.
  • the bulk properties of a polymer can differ significantly from its film properties once formed into a balloon, it has been determined that certain bulk polymers, processed according to the invention, may result in a combination of properties that are useful for making balloons to use in medical procedures. Namely, such balloons may be useful for use in medical devices requiring a high dilatation force.
  • Bulk polymers that have a tensile strength of not less than about 5000 psi, elongation at break of not less than about 50%, and flexural modulus of not less than about 200 kpsi may produce, if processed according to the invention, balloons with high strength, good flexibility, and toughness.
  • the selected polymer first undergoes a melt extrusion process to maximize the density of small spherulites.
  • the formation of spherulites is favored over other crystal morphologies when the polymer molecular chains are not oriented before the melt extrusion.
  • the polymer is preferably heated to a melt state and pumped through a die at a uniform rate to form an extruded tubing. After emerging from the die, the extruded tubing passes through an air cooling gap (e.g., tank gap) .
  • the extruded tubing is pulled by a puller into a water cooling trough (e.g., quench bath) .
  • the crystallization time of a polymer increases from T g to a maximum, and then decreases as the temperature rises to the equilibrium melting point (T e ) .
  • T e is the temperature at which the largest, most perfect crystals can be formed by slow crystallization or annealing.
  • the preferred temperature for initiation of nucleation during extrusion is at the peak of the curve (i.e., where crystallization is the fastest) shown in FIG. 3.
  • the polymer preferably attains the preferred temperature in the tank gap, after emerging from the extruder but before reaching the quench bath.
  • the extruded tubing reaches the quench bath, the majority of the nucleation should be complete.
  • the crystal morphology may continue to grow and change, however, depending on the quenching temperature.
  • the extruded tubing preferably is cooled by a quench bath that is below the T g of the polymer that forms the extruded tubing.
  • the quenching temperature is maintained well below the T g of the selected polymer, the material ' s crystal morphology will be essentially "frozen.” If the quenching temperature, however, is maintained just above the T g of the material, then depending on the puller speed, the polymer chains in the material could have enough mobility and time to further crystallize and form a different crystal morphology, thereby making the material stiffer (see Table 4) . As illustrated in Table 4, lowering the quenching temperature helps to produce a material that is more flexible. If the extruded tubing is comprised of PBT, the tubing is preferably quenched at a temperature between about 5°C and about 40°C.
  • tubing made of PTT is preferably quenched at a temperature between about 5°C and about 50°C.
  • the extruded tubing next undergoes a two-step forming process, which includes cold forming the tubing into an intermediate balloon blank and subsequently thermoforming the balloon blank into a balloon.
  • This two-step forming process helps to further increase the density of spherulites and is particularly advantageous for polymers that have fast nucleation and high crystallinity.
  • balloons made of the appropriate material exhibit an increased balloon hoop tensile strength and, in some case, a T g higher than the extruded tubing from which it came.
  • balloons of the invention have a hoop tensile strength of greater than about 20,000 psi.
  • balloons of the invention have a hoop tensile strength of greater than about 30,000 psi.
  • the extruded tubing is "cold formed" into an intermediate balloon blank.
  • the extruded tubing is axially stretched at a temperature no higher than about T g + 10°C.
  • the extruded tubing is axially stretched at a temperature when the polymeric material composing the intermediate balloon blank is in its leathery state.
  • Extruded tubing made of PBT, for instance is preferably cold formed at a temperature between about 15°C and about 40°C.
  • the realignment imparts a strong molecular orientation to the polymeric material and helps to make the walls of the blank stronger.
  • Parameters that may be controlled to influence the outcome of the cold-forming process include, for example, internal pressure, temperature, and deformation rate. One can alter a combination of these parameters as needed to strengthen the walls of the balloon formed according to the invention.
  • the material if the extruded tubing is inflated to radially expand its diameter during the axial stretching, the material preferably is axially stretched to at most about 300% of its original length and radially expanded by pressure to at most about 150% beyond the non-distended radial diameter of the extruded tubing.
  • the extruded tubing is preferably stretched at a constant linear rate no faster than about 100 inches/minute. More preferably, the material is stretched at a constant linear rate no faster than about 20 inches/minute . In an alternative embodiment, the material is stretched at a constant linear rate no greater than about 5 inches/minute.
  • the extruded tubing is preferably axially stretched until it reaches its ductile limit.
  • the ductile limit corresponds to the maximum plastic deformation an extruded tubing can experience before the polymer in the tubing fractures .
  • the less the material is axially stretched the more the material may be radially expanded during the cold-forming process.
  • the more the material is axially stretched the less the material can be radially expanded.
  • the intermediate balloon blank is preferably inflated during thermoforming by an internal pressure that is higher than that used during the cold-forming process. If a high internal pressure is used, however, during the cold-forming step (e.g., causing the tubular blank to expand beyond its original diameter) , the inflation pressure used during the thermoforming is preferably lower than the pressure used during cold forming.
  • the axial deformation rate should be reduced to give the polymeric structures in the material more time to reorient. It is believed that by axially stretching the extruded tubing at a sufficiently slow rate during the cold forming, the recoil of the polymeric chains composing the tubing imparts a multidimensional orientational strength to the material as a result of the new polymeric crystalline structure formed during cold forming. At a given temperature, axially stretching the extruded tubing more slowly allows the polymeric material more time to relax and crystallize. The preferred stretching rate is dependent on the difference between the cold-forming temperature and the T g of the polymer.
  • the tubing is preferably stretched at a rate no greater than about 20 inches per minute. More preferably, the tubing is stretched at a rate less than about 10 inches per minute. Even more preferably, the stretching rate is no greater than about 5 inches per minute.
  • the tubing comprising PBT may be stretched as fast as about 300 inches/minute.
  • the intermediate balloon blank is thermoformed.
  • the intermediate balloon blank is heated to a temperature at least about 10°C higher than T g/ while pressure is applied to expand the intermediate balloon blank.
  • the intermediate balloon blank is heated to a temperature no higher than about 10°C below its melt temperature.
  • the thermoforming step further crystallizes the material to form additional small spherulites, yielding a balloon that advantageously exhibits balanced material orientational properties, including a balanced burst failure mode .
  • the intermediate balloon blank is expanded during thermoforming to no more than about 800% of the original non-distended radial diameter of the tubular blank.
  • the intermediate balloon blank is preferably expanded to a hoop ratio that yields a balloon with the highest hoop tensile strength.
  • An intermediate balloon blank made of PBT, for example, preferably would be thermoformed at a temperature between about 85°C and about 150°C.
  • the PBT intermediate balloon blank most preferably is expanded to attain a hoop ratio of about 5.6.
  • the two-step forming process advantageously preserves the., small spherulites formed during the extrusion process and helps promote additional small spherulite formation in the polymer material.
  • the small spherulites made during the extrusion and the two-step forming process helps produce a compliant balloon with balanced biaxial material properties and improved balloon hoop tensile strength. This results in a balloon that exhibits the ability to impart a high dilatation force and easy re-folding after dilatation.
  • the two-step forming process enables forming balloons that have been traditionally difficult to thermoform. As shown in Tables 5 (a) - (b) , the two-step forming process also imparts higher balloon hoop tensile strength than prior art forming processes .
  • run number 13 of Table 5 (a) a PBT balloon was made without the cold-forming step.
  • the balloon in run number 14 was cold formed by stretching the tubing at ambient temperature in air. As shown in run number 14, cold forming helped increase the balloon's hoop strength.
  • the balloon in run number 15 was cold formed at 30 °C in a water bath, resulting in a higher balloon hoop tensile strength.
  • PBT balloons made from ULTRADUR® 4500 were similarly made with and without cold forming. As shown in run numbers 16 and 17, cold forming improves balloon hoop tensile strength. Because of the increased material hoop tensile strength from cold forming, the intermediate balloon blank formed in run number 17 required a greater thermoforming pressure than run number 16 to inflate the balloon blank into a balloon. [0075] Run numbers 18 and 19 compare two different cold-forming methods using VALOX® 315. As shown in run number 19, cold forming without internal pressure may yield balloons having superior balloon hoop tensile strength compared to balloons cold formed with internal pressure. The improvement to the material tensile strength is reflected in part by the necessity to use a higher thermoforming pressure to inflate the balloon blank in run number 19 compared to run number 18.
  • Run numbers 20-23 in Table 5(b) compare the effects of cold forming on PTT balloons. As shown in Table 5 (b) , PTT balloons that underwent cold forming produced higher balloon hoop tensile strengths than a balloon made without cold forming.
  • the glass transition temperature of the balloons of the invention is preferably above human body temperature (i.e., above about 37°C) . More preferably, the glass transition temperature is above about 40°C. In one embodiment of the invention, the balloon has a glass transition temperature of between about 45°C and about 60°C. Even when the glass transition temperature is above 40°C, the balloons remain compliant and suitable for use with a medical device in the human body.
  • Tests were performed to compare extruded tubing versus balloons made with the two-step forming process.
  • an extruded tubing made from each type of material was cold formed by radially expanding and simultaneously axially stretching the tubing.
  • the intermediate balloon blank was subsequently thermoformed.
  • the balloons formed with the two- step forming process had a higher T g than the extruded tubing.
  • Table 6 Illustrates Glass Transition Temperature Improvement As A Result of the Two- Step Forming Process (With Radial Expansion During Cold Forming)
  • Table 7 illustrates the effect on balloon hoop tensile strength of the cold-forming pressure relative to the thermoforming pressure .
  • the thermoforming pressure is preferably greater than the cold-forming pressure.
  • the cold-forming pressure is preferably higher than the thermoforming pressure if the inner diameter of the cold-formed tubing is larger than the extruded tubing (run numbers 32-33) .
  • tubing that is axially stretched at slower rates produces balloons with higher hoop strength.
  • run numbers 34-36 the faster the axial stretching rate, the lower the hoop tensile strength of the balloon. If the tubing is axially stretched too quickly, it is believed that the polymer has insufficient time to relax, resulting in a tubing that is then highly oriented in the axial direction, thus making it difficult to produce balloons with balanced biaxial material properties that are capable of imparting a high dilatation force under a high internal pressure.
  • Table 9 Effect of cold-forming temperature on balloon hoop tensile strength.
  • the two-step forming process was found beneficial especially for fast crystallization materials.
  • Table 10 demonstrates that when the process is applied to a material that has a slow crystallization time, such as PET, neither the T g nor the balloon hoop tensile strength improves in comparison to a balloon made according to a typical prior art method (e.g., run number 39).
  • run number 40 a moderate stretching rate and an internal pressure of 110 psi was applied to the extruded tubing during cold forming.
  • run number 41 a low stretching rate and no internal pressure was used during cold forming.
  • run number 42 a high stretching rate and no internal pressure was applied during cold forming.
  • a longer relaxation time was used in run number 41, the balloon showed lower balloon hoop tensile strength compared to run number 42. This result is believed to arise from stress-induced crystallization caused by the faster rate of stretching the PET.
  • Run number 41 shows the most flexibility compared to the runs that do not use internal pressure during the cold-forming process. It is believed that if the crystallization rate of the materials is too slow relative to the rate the material is stretched, new additional spherulites may not have enough opportunity to form during the stretching process of the cold-forming step, resulting in a material that is stiffer. [0090] In all of the tested PET balloons, the T g of the balloon was found to be lower than that of the extruded tubing from which it was formed. Furthermore, no conditions for the two-step forming process were found to yield a balloon with better hoop tensile strength and flexibility than a balloon prepared according to known prior art conditions (run number 39) .
  • the two-step forming process was found not to be as beneficial for materials with strong hydrogen bonding, such as polyamides and nylon.
  • materials with strong hydrogen bonding such as polyamides and nylon.
  • Table 11 when the two-step forming process of the invention was applied to Nylon 12, for instance, and compared against the same material . that underwent only the thermoforming step, neither the T g nor the balloon hoop tensile strength showed improvement.
  • Table 12 because of the strong hydrogen bonding present in the polymer, the properties of balloons made of polyamide did not vary significantly with varying process conditions. Furthermore, in all cases with the nylon balloons, the balloons formed according to two-step process exhibited a lower T g than that of the extruded tubing from which it came .
  • CELANEX® 1600 a high molecular weight grade polybutylene terephthalate with an intrinsic viscosity of 1.2, was melt extruded at a temperature between about 246°C and about 260°C and quenched at a temperature between about 4°C and about 38°C. The material was extruded to form an extruded tubing with an inner diameter of about 0.02 inches and an outer diameter of about 0.04 inches. Following extrusion, the extruded tubing was cold formed at about 22°C while inflated to a pressure of about 520 psi. During the cold forming, the tubing was axially stretched 280% at an axial stretch rate of about 5 inches/minute.
  • the intermediate balloon blank was thermoformed at a temperature of about 95°C, while inflated to a pressure of about 280 psi.
  • the blank was subjected to a hoop ratio of about 5.6, yielding a balloon with a non-distended working diameter of about 3.0 mm.
  • the processed balloon's hoop strength was about 32,789 psi with a T g of about 49°C.
  • the stiffness factor of the balloon made according to these steps is about 64 lbs/inch.
  • CELANEX® 1600 a high molecular weight grade polybutylene terephthalate with an intrinsic viscosity of 1.2, was melt extruded at a temperature between about 246°C and about 260°C and quenched at a temperature between about 4°C and about 38°C. The material was extruded to form an extruded tubing with an inner diameter of about 0.02 inches and an outer diameter of about 0.04 inches. Following extrusion, the extruded tubing was cold formed at about 30°C without internal pressure. During the cold forming, the tubing was axially stretched 280% at an axial stretch rate of about 20 inches/minute.
  • the intermediate balloon blank was thermoformed by inflating it to a pressure of about 500 psi at a temperature of about 95°C.
  • the blank was subjected to a hoop ratio of about 5.6, yielding a balloon with a non-distended working diameter of about 3.0 mm.
  • the processed balloon's hoop strength was about 33,391 psi with a T g of about 49°C.
  • the stiffness factor of the balloon made according to these steps is about 50 lbs/inch.
  • tubing comprising PTT processed according to the invention including cold forming with or without internal pressure, was found to yield balloons suitable for use in high dilatation force medical applications.
  • Extruded tubing comprising PTT is preferably cold-formed at a temperature between about 30°C and about 50°C.
  • the intermediate balloon blank made by cold forming is thermoformed at a temperature between about 85° C and about 99°C.
  • the balloon made of PTT has an intrinsic viscosity of between about 0.9 and about 1.5, a crystallization time of less than about 15 seconds, a hoop tensile strength of greater than about
  • the balloon made of PTT has a glass transition temperature of between about 55°C and about 70°C.

Abstract

L'invention concerne un ballon et un nouveau procédé de production et d'utilisation dudit ballon. Le procédé décrit consiste en deux étapes de formation permettant de pallier la fragilité classique présentée par les polymères utilisés sous la température de transition vitreuse (Tg). L'invention concerne également des critères de sélection de matières polymères qui pourraient être utilisées dans la production de ballons médicaux ayant une résistance et une flexibilité souhaitable lorsque ces matières sont traitées selon le procédé de l'invention.
EP02766060A 2002-08-22 2002-08-22 Ballon a resistance elevee et a douceur sur mesure Withdrawn EP1545684A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2002/026792 WO2004022149A1 (fr) 2002-08-22 2002-08-22 Ballon a resistance elevee et a douceur sur mesure

Publications (1)

Publication Number Publication Date
EP1545684A1 true EP1545684A1 (fr) 2005-06-29

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EP (1) EP1545684A1 (fr)
JP (1) JP2005536310A (fr)
AU (1) AU2002329810A1 (fr)
WO (1) WO2004022149A1 (fr)

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Publication number Priority date Publication date Assignee Title
US10951940B2 (en) 2007-09-26 2021-03-16 Maxell, Ltd. Portable terminal, information processing apparatus, content display system and content display method

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE189402T1 (de) * 1994-03-02 2000-02-15 Scimed Life Systems Inc Blockcopolymerelastomer ballon für katheter
US5871468A (en) * 1996-04-24 1999-02-16 Medtronic, Inc. Medical catheter with a high pressure/low compliant balloon
JPH10295801A (ja) * 1997-04-25 1998-11-10 Nippon Zeon Co Ltd バルーンカテーテル
WO1999044649A1 (fr) * 1998-03-04 1999-09-10 Scimed Life Systems, Inc. Composition et procede de production de ballonnets de catheter en pbt

Non-Patent Citations (1)

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Title
See references of WO2004022149A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10951940B2 (en) 2007-09-26 2021-03-16 Maxell, Ltd. Portable terminal, information processing apparatus, content display system and content display method

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JP2005536310A (ja) 2005-12-02
AU2002329810A1 (en) 2004-03-29
WO2004022149A1 (fr) 2004-03-18

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