Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Including application of internal fluid pressure to hollow...
Reexamination Certificate
1999-06-22
2002-12-17
McDowell, Suzanne E. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Including application of internal fluid pressure to hollow...
C264S573000
Reexamination Certificate
active
06495090
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to catheter balloons for medical devices. In particular, the present invention relates to biaxially oriented semi-compliant catheter balloons comprising acrylonitrile polymers, acrylonitrile copolymers, and acrylonitrile blends. The present invention further comprises methods of making such catheter balloons.
BACKGROUND OF THE INVENTION
Catheter balloons are extensively used in medical applications such as angioplasty, valvuloplasty, urological procedures, and tracheal or gastric intubation. Catheter balloons are generally made using non-compliant materials (e.g. polyethylene terephthalates, polyacrylenesulfide, and copolyesters), compliant materials (e.g., polyvinyl chloride [PVC], polyurethanes, crosslinked low density polyethylenes [PETs], and highly irradiated linear low density polyethylene [LDPE]), or semi-compliant materials (e.g., nylon, and polyamines). Some of the desirable attributes for catheter balloons include high tensile strength (to avoid bursting under pressure and to dilate tough lesions), controlled compliance (to avoid overinflation and subsequent vessel damage), flexibility (to facilitate retraction through vessels), moisture resistance (to avoid loss of mechanical strength), ease of coating with drugs or lubricants, and ease of bonding to a catheter material.
However, no single prior art catheter balloon material offers all of the above-discussed desirable characteristics. For example, while non-compliant balloon materials have the advantage of high tensile strength, this same property makes them resistant to folding and reshapability with the result that they are difficult to retract through vessels. Although decreased wall thickness may overcome folding resistance, it nevertheless results in “pinholing,” which is associated with a fragility during insertion and the need for extreme care in handling, as well as possible damage to surrounding tissue caused by high pressure fluid leakage. Additionally, because catheter balloons of non-compliant materials do not inflate beyond a particular distended profile, they cannot be tailored to fit the changing diameter of physiological vessels. Non-compliant materials suffer from the added drawback that they do not readily accept coatings and are difficult to bond to other materials (e.g., catheter materials) due to their higher melt temperatures which resist melting adhesion, and polymer polarity which resists biocompatible adhesives.
Similarly, catheter balloons made of compliant materials exhibit some undesirable characteristics. Compliant balloons are characterized by the ability to continually distend with increasing pressure, thus causing additional distention of the treated vessel. However, this property also risks overinflation of the catheter balloon and subsequent vessel damage. The risk of overinflation is exacerbated by the low tensile strength of compliant materials, which results in balloon burst failure and vessel injury. Though this risk may be reduced by increasing the balloon's wall thickness, the resulting balloons resist folding (i.e., winging) and are more cumbersome to use because of their rigidity.
Catheter balloons which are constructed of art-known semi-compliant materials also possess undesirable properties. For example, while known semi-compliant balloon materials combine the advantages of relatively high tensile strength and controlled compliance, they nevertheless continue to exhibit pinholing, difficulty in coating and bonding with other materials, and excessive material shrinkage. Semi-compliant nylon materials suffer from the additional disadvantage of being hygroscopic, thus suffering from accelerated loss of mechanical strength.
Thus, what is needed is a catheter balloon having relatively high tensile strength, controlled compliance, reduced tendency for pinholing, ease of coating with and of bonding to other compounds, as well as resistance to moisture.
SUMMARY OF THE INVENTION
The invention provides a catheter balloon comprising biaxially oriented acrylonitrile polymer. In one preferred embodiment, the balloon is within its glass transition state at approximately human body temperature. Without intending to limit the invention to a particular wall thickness and tensile strength, in an alternative preferred embodiment, the acrylonitrile polymer catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0013 inches and a tensile strength of at least approximately 15000 psi. While not intending to limit the invention to a particular tailored compliance, in a more preferred embodiment, the tailored compliance of said acrylonitrile polymer catheter balloon is from approximately 5% to approximately 15%. In an alternative embodiment, the acrylonitrile polymer catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0015 inches, reaches approximately quarter size at a pressure from approximately 12 atmospheres to approximately 14 atmospheres, reaches nominal size at a pressure of from approximately 4 atmospheres to approximately 6 atmospheres, and has a rated burst pressure of at least approximately 1 atmosphere greater than said pressure from approximately 12 atmospheres to approximately 14 atmospheres.
The invention further provides a catheter balloon comprising biaxially oriented acrylonitrile copolymer. Without limiting the invention to any particular components, in one embodiment, the acrylonitrile copolymer comprises acrylonitrile and methyl acrylate. Without limiting the invention to any particular components and/or proportions of components, in a preferred embodiment, the acrylonitrile copolymer comprises from approximately 73 to approximately 77 parts by weight of acrylonitrile and from approximately 23 to approximately 27 parts by weight of methyl acrylate, said acrylonitrile copolymer being sold under the trademark “BAREX 210™.” In a more preferred embodiment, the BAREX 210™ balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0012 inches and a tensile strength of at least approximately 15000 psi. In yet a more preferred embodiment, the tailored compliance of said acrylonitrile copolymer catheter balloon is from approximately 5% to approximately 15%. In a further preferred embodiment, the intrinsic viscosity of said acrylonitrile copolymer catheter balloon is from approximately 0.8 to approximately 1.3. In yet a further preferred embodiment, the acrylonitrile and methyl acrylate copolymer catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0012 inches, reaches approximately quarter size at a pressure from approximately 12 atmospheres to approximately 14 atmospheres, reaches nominal size at a pressure of from approximately 4 atmospheres to approximately 6 atmospheres, and has a rated burst pressure of at least approximately 1 atmosphere greater than said pressure from approximately 12 atmospheres to approximately 14 atmospheres.
Also without limiting the invention to particular components and/or proportions of components, in an alternative preferred embodiment, the acrylonitrile copolymer comprises from approximately 73 to approximately 77 parts by weight of acrylonitrile and from approximately 23 to approximately 27 parts by weight of methyl acrylate, said acrylonitrile copolymer being sold under the trademark “BAREX 218™.” In a more preferred embodiment, the BAREX 218™ catheter balloon has a mean wall thickness of from approximately 0.0006 inches to approximately 0.0013 inches and a tensile strength of at least approximately 15000 psi. In yet a more preferred embodiment, the tailored compliance of said acrylonitrile copolymer catheter balloon is from approximately 5% to approximately 15%. In a further preferred embodiment, the intrinsic viscosity of said acrylonitrile copolymer catheter balloon is from approximately 0.8 to approximately 1.3. In yet a further preferred embodiment, the BAREX 218™ catheter balloon has a mean wall th
Infinity Extrusion & Engineering
McDowell Suzanne E.
Medlen & Carroll LLP
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