Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-04-23
2004-06-01
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C528S015000, C528S031000, C528S032000, C524S433000, C524S588000
Reexamination Certificate
active
06743831
ABSTRACT:
RELATED APPLICATION
Not applicable.
FIELD OF THE INVENTION
The present invention is directed to medical catheters having improved mechanical properties.
BACKGROUND OF THE INVENTION
Various types of materials are used for catheters, such as Dow Corning HP (high performance) or Dow Corning ETR (extra tear resistance) material. These types of materials have relatively high tear resistance. However, it would be desirable to have a catheter material that had a higher crush and creep resistance than Dow Corning HP or Dow Corning ETR.
Crush resistance and creep resistance are important properties for catheters because they can be subjected to various forces, such as compression and stretching forces after they are implanted within a patient. For example, a catheter that is implanted within a patient so that it can come into contact with the spinous processes can be frequently subjected to compression from the spinous processes.
Other materials have higher crush and creep resistance than Dow Corning HP and Dow Corning ETR. An example of such a material is Dow Corning MDX. While this type of material has relatively high crush and creep resistance, it is not considered to be suitable material for a catheter because a higher tear resistance material is believed to be necessary for such a catheter.
Tear resistance is important for catheters because they can be “nicked” or cut on the introducer needle during placement. Notably, this can occur without the physician implanting the catheter knowing that a nick or cut had occurred. Tear resistance is a mechanical property that indicates how quickly a cut or tear progresses to a fracture or break.
As it will be readily appreciated by those skilled in the art of medical catheters, certain mechanical properties, such as tear strength, abrasion resistance, resistance to shredding, compression set, crush and creep resistance are of great importance in the materials for any catheter device that is implanted into the human body. It should also be readily appreciated by those skilled in the art that catheters having improved mechanical properties, and particularly improved tear resistance, crush resistance and creep resistance provide higher performance and better results than catheters having lesser such mechanical properties.
The need still exists for catheters having improved mechanical properties, including improved tear resistance, crush resistance and creep resistance. The present invention provides such a catheter.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a catheter having improved overall mechanical properties over prior catheters.
It is another object of the present invention to provide tubular material for implantable medical catheters, which material has improved overall mechanical properties, including improved tear resistance, crush resistance and creep resistance.
The implantable medical catheter disclosed herein attains the foregoing and other objects of the present invention. More specifically, the implantable medical catheter of the present invention comprises a catheter defining at least one fluid passageway and a cured elastomer composition obtained by cross-linking an uncured blend composition that comprises an intimately admixed mixture that comprises the following components: (A) silica that had been silyliated by treatment and contains trialkylsilyl groups comprising approximately 23 to 45 percent by weight of the mixture; (B) a polysiloxane copolymer composed of divalent —R
1
R
2
SiO—, divalent —R
3
R
4
SiO— and end-blocking R
5
R
6
R
7
SiO— units, comprising approximately 55 to 77 percent by weight of the mixture, where R
1
and R
2
independently are lower alkyl of 1 to 6 carbons, phenyl or trifluoropropyl, R
3
is vinyl, allyl, or other olefinic group having up to 4 carbons, R
4
is lower alkyl of 1 to 6 carbons, phenyl or trifluoropropyl, and R
5
, R
6
, and R
7
independently are lower alkyl of 1 to 6 carbons, phenyl, vinyl, allyl, or other olefinic group having up to 4 carbons and one double bond, the polysiloxane copolymer has a degree of polymerization (D.P.) approximately in the range of 3500 to 6500, and the olefin containing —R
3
R
4
SiO— groups are present randomly distributed in the polysiloxane copolymer and approximately in the 0.05 to 0.3 mol percent range, with the provisos that when R
1
, or R
2
, or both represent phenyl groups then proportion of the phenyl-containing divalent siloxane units does not exceed 15 mol percent and when R
1
or R
2
or both represent trifluoropropyl groups, then the proportion of the trifluoropropyl-containing divalent siloxane units does not exceed approximately 40 mol percent in the polysiloxane copolymer; (C) a catalyst, and (D) an organohydrogen polysiloxane cross-linker, the catalyst and the cross-linker being present in the uncured blend composition in sufficient amount to cause the cross-linking reaction to occur.
In one embodiment, the polysiloxane copolymer, the —R
1
R
2
SiO— group is —R(CH
3
)
2
SiO—, the —R
3
R
4
SiO— group is —CH
3
(CH
2
═CH)SiO—, and the R
5
R
6
R
7
SiO— group is —(CH
3
)
2
(CH
2
═CH)SiO—.
In one embodiment, the —CH
3
(CH
2
═CH)SiO— group is present in the proportion of 0.142 mol percent in the polysiloxane copolymer.
In one embodiment, the silyliated silica includes trimethylsilyl groups in such quantity that the carbon content of the silyliated silica is in the range of approximately 4 to 8 percent by weight of the silyliated silica.
In one embodiment, the carbon content of the silyliated silica is approximately 7.3 percent by weight of the silyliated silica.
In one embodiment, the catheter includes barium sulfate (BaSO
4
).
REFERENCES:
patent: 4055682 (1977-10-01), Merrill
patent: 5908878 (1999-06-01), Baity et al.
patent: 5948539 (1999-09-01), Paulsen et al.
patent: 6040369 (2000-03-01), Paulsen et al.
patent: 6080829 (2000-06-01), Tapsak et al.
Helen Kazemi-Shirazi et al., “New Silicone Rubber 2, Biocompatible Silicone Rubbers”; Die Angewandt Makromolekulare Chemi 203 (1993) p. 193-201. Institute of Chemical Technology of Organic Materials, Vienna University of Technology, Getreidemark, 9/162, A-1060 Vienna, Austria.
International Search Report dated Sep. 4, 2003.
Banner & Witcoff , Ltd.
Medtronic Inc.
Moore Margaret G.
Zimmer Marc S.
LandOfFree
Implantable medical catheter having reinforced silicone... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Implantable medical catheter having reinforced silicone..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Implantable medical catheter having reinforced silicone... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3341988