Surgery – Means and methods for collecting body fluids or waste material – Receptacle attached to or inserted within body to receive...
Reexamination Certificate
1994-11-14
2001-01-30
Weiss, John G. (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Receptacle attached to or inserted within body to receive...
C604S403000, C604S408000
Reexamination Certificate
active
06179818
ABSTRACT:
The invention relates to a vessel for biological materials comprising a multilayer polymeric barrier material that has very low permeability to small molecules, such as water and oxygen, high flexibility and softness, and is resistant to tearing. The invention is particularly useful for forming vessels that receive biological fluids, such as ostomy bags and bags for storing blood, blood products, and IV solutions. The barrier material is comprised of at least one layer of an oriented liquid crystal polymer (“LCP”).
A critical feature for an ostomy bag, which is used to collect body fluids from the ostomies of colostomy, urostomy and ileostomy patients, is low oxygen permeability. The measure of oxygen permeability serves as a surrogate for measures of the permeability of other small molecules, such as those causing odor. The greater the oxygen permeability, it is believed, the more the ostomy bag will become a source of unpleasant odor as an ostomy patient's day progresses. In view of the odor problem, a material having an oxygen permeability in excess of about 100 cc/m
2
/day cannot reasonably be used for this purpose. A material that is now widely used commercially, a plasticized poly(vinylidene chloride) (“PVDC”), has a permeability of between about 35 cc/m
2
/day and 75 cc/m
2
/day when used in commercially practical thicknesses, (e.g., from about 10 to 75 &mgr;m). PVDC-based materials are sometimes plasticized to increase softness. However, plasticized materials generally must be thicker to provide adequate barrier properties.
PVDC-based materials are almost universally used despite the now well-established environmental concerns surrounding the use of chlorinated organic products. These concerns are especially accentuated for medical products, where biological safety issues make incineration, which can generate
dangerous chlorinated materials such as dioxin, a preferred method of disposal. The prevalence of PVDC-based products is based on their flexibility, softness and performance as odor barriers. One feature of the present invention is that it can be used to make a material with properties that make it practical for use in ostomy bags and that has an oxygen permeability substantially less than that of comparable PVDC films. In some embodiments, the present invention unexpectedly can show permeabilities of less than 5 cc/m
2
/day, even in some cases less than about 2 or about 1 cc/m
2
/day, while retaining strength and flexibility properties suitable for forming ostomy bags.
Other properties that a material that forms an ostomy bag should have are strength, flexibility and softness. The importance of the strength of an ostomy bag to patients, for whom social environments can be trying, is self-evident. The importance of flexibility is less evident. Flexibility and softness correlate with quietness when the material is flexed. For instance, an ostomy bag of a sufficiently flexible material will not make a noise or “crinkle” when a patient moves or shifts his or her weight. The real or perceived social trauma arising from such noise can be substantial. With the present invention, it is believed that ostomy bags that at least match PVDC for strength, flexibility, softness and quietness can be prepared while retaining the remarkable barrier properties discussed above.
For vessels for IV solutions, blood and blood products, strength and flexibility have also been important properties. Safety issues accentuate the importance of strength. Flexibility is important for ease of handling and, more importantly, to allow the vessel to collapse when fluid is transferred out or to expand from a collapsed form when fluid is transferred into it. In this way, the collapsible vessel avoids the formation of vacuums or air pockets that would block fluid transfer. Biohazard safety is one of the reasons for using materials with good barrier properties for these vessels. Another function of the barrier properties of these vessels is to limit fluid loss. Traditionally, such bags have been constructed of poly(vinyl chloride) (“PVC”). PVC, while forming an excellent barrier to small molecules, nonetheless, when used by itself, allows the evaporation of too much water to be useful for long-term storage of such biological fluids. To overcome this, medical workers have typically used a second, enveloping bag of rubber-modified polyethylene to enclose the PVC bag and thus limit water loss. The barrier material of the present invention should limit this water loss, allowing medical workers to avoid using the second enveloping bag.
The combination of flexibility, strength and impermeance of the barrier material of the invention is surprising since the material has a core comprising an LCP. LCP materials have lately been recognized for their barrier properties, about which there has been interest in the food industry. See, e.g., Japanese Patent Applications Nos. 4135750, 3269054, 3071842, 2261456, 2253948-2253951, 2253920, 2220821, 2191636, 62187033, and 56028852, and European Patent Application No. 503063. However, it is believed that such materials have not been considered for use for forming the ostomy vessels and vessels for IV solutions, blood and blood products contemplated by the present invention. Such LCP compositions are notorious for their stiffness and the ease with which they tear along at least one axis. As discussed above, these properties would not be appropriate for the vessels of the invention. The present invention avoids the stiffness problem by using a thin layer of oriented LCP. (However, the thinness of the LCP layer, which has the greatest contribution to gas impermeability and a substantial contribution to strength, makes the superior performance of the invention over PVDC membranes even more surprising.
In one aspect, the present invention provides for increased tear resistance of the LCP layer by adding certain optically active compounds to the LCP material. Such optically active compounds can help bring about the formation of alignment patterns of the LCP materials to create a “cholesteric” phase (defined further below). Such cholesteric phases have multiple planar segments of aligned mesogenic groups, with the alignment of each succeeding planar segment incrementally offset from the alignment of the previous planar segment. The net result is that, for any direction of stress that might be applied to the material, there are aligned, self-reinforcing LCP molecules situated to meet the stress.
Another aspect of the present invention is to increase the tear resistance of the LCP layer by the application of torsional stress to the upper and lower surfaces of an LCP material as it is extruded from a slot die. The torsional stress tends to align the mesogenic groups in the LCP composition in the direction of the stress. The molecular alignment pattern of the upper, lower and even intermediate layers of material made this way can be such that there is sufficient reinforcement to meet stress along any axis, and thus to avoid tearing. See, Lusignea and Blizard, “Processing and Applications of Liquid Crystal Polymers and Blends, Society for Advancement of Material and Process Engineering” (1993).
Another method of increasing tear resistance in accordance with the present invention is to use the “inflation” method (also called the “blown film” process). See, Japanese Patent Application No. 4085325 and
Encyclopedia of Polymer Science and Engineering
(John Wiley & Sons, 1987) V. 7, pp. 98-102. In this method, order in a first orientation is imposed by melt-extruding the LCP composition through a die. Concurrently, air is injected through the middle of the die, forming a bubble in the extruded material. The surface forces on the inflating film apparently impart new directions of order among some of the oriented, mesogenic domains. It is believed that film formed in this way has, within one layer, “biaxial” orientation. However, the applicant does not wish to be limited by this theory. The important observation is that films manufactured in this way have useful thicknesses for osto
Klem Leslie
Kydonieus Agis
Lin Cuilian
Shah Kishore
Bristol--Myers Squibb Company
Furman, Jr. Theodore R.
Kilcoyne John M.
Mager Carie
Weiss John G.
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