Surgery – Male reproductory tract shields or birth control devices
Reexamination Certificate
1995-05-31
2001-04-10
Brown, Michael A. (Department: 3764)
Surgery
Male reproductory tract shields or birth control devices
Reexamination Certificate
active
06213123
ABSTRACT:
This invention relates to a method for making a non-rigid, flexible, thin walled, closed-ended, tubular article of thermoplastic elastomer, to an apparatus therefor and to the article produced. More particularly, this invention relates to a method for drawing, with a plug assist, very thin walled, non-rigid, flexible, closed-ended, tubular articles of thermoplastic elastomer, to a plug assisted drawing apparatus therefor and to liners, condoms and finger cots produced thereby.
BACKGROUND OF THE INVENTION
Thin walled tubular articles of thermoplastic elastomer are known in the art to provide strong, thin, flexible protective barriers. Protective barriers having these characteristics are particularly useful to protect skin surfaces from unwanted contact or contamination and, yet, to preserve sensitivity of touch, as with condoms or finger cots used in medical examination.
U.S. Pat. No. 4,576,156, Dyck, et al., describes a condom manufactured from a variety of polyurethane thermoplastic elastomers. In the process for manufacture, a shaped mandrel is urged into the face of pre-heated, extruded elastomeric film and the film assumes the shape of the mandrel with the application of vacuum.
U.S. Pat. No. 4,684,490, Taller, et al., describes a condom manufactured from certain polyurethane thermoplastic elastomers. In the process for manufacture, a mandrel is coated with an emulsion of elastomeric material prepolymer and the coating is cured at elevated temperature.
Additional methods to manufacture condoms from thermoplastic elastomers are generally known. In one process for manufacture, the thermoplastic elastomer is blown into very thin film, the film is cut into appropriate preforms and the segments are heat sealed to form a condom.
Despite the fact that thermoplastic elastomers are taught to be suitable materials for the manufacture of the articles described above; despite the fact that these elastomers may be employed to produce a stronger, thinner and a more reliably defect free product as compared to natural rubber, the present material of choice; thin walled tubular articles are not commercially produced from thermoplastic elastomers. Each of the above described processes is unsuitable for high volume production for one or more of several reasons. For instance, the wall thickness of the resultant product may not be controllable to the desired tolerance. Also, though the product is thinner and stronger, the elastomeric modulus may be too high, i.e., the elastomer may be too stiff. Further, considering cure or annealing times required, the through-put of the machinery required may be too low.
Thus, it is an object of the present invention to rapidly produce tubular articles of thermoplastic elastomer which are soft, flexible and have a uniformly thin wall thickness.
It is also an object of the present invention to provide a method for melt forming tubular articles of thermoplastic elastomer which have a low modulus and a uniformly thin wall thickness.
It is a further object of the present invention to provide a method and hardware to draw with plug assist, tubular articles of thermoplastic elastomer which have a low modulus and a uniformly thin wall thickness.
It is another object of the present invention to provide a thermoplastic elastomer which may be drawn into tubular articles having thin walls and a low modulus.
SUMMARY OF THE INVENTION
Briefly, according to the present invention, there is provided a method for making a thin walled, closed-ended, tubular article of a thermoplastic elastomer, said method comprising:
a) providing a tubular mold having a longitudinal axis, a terminal end, and an opposite open end, said open end having a rim, and providing a preform of thermoplastic elastomer, said preform having two opposing, substantially coplanar faces and said thermoplastic elastomer heated to have a viscosity and elasticity within a range that the preform can be drawn;
b) placing a face of said preform of thermoplastic elastomer on said rim;
c) applying air pressure or vacuum to one face of said preform to impose an air pressure differential across the faces of the preform and axially directing a plug against the outward face of the preform, thereby drawing and urging the preform to flow into the mold, the plug directed at a rate upon contact with the preform that the preform is not punctured by the plug;
d) further applying air pressure or vacuum and further axially directing the plug against the preform, the air pressure or vacuum applied at a rate and the plug directed at a rate whereby the resultant air pressure differential across the faces of the preform maintains a portion of the flowing preform away from the wall of the tubular mold; and
e) at a point where the plug nears the terminal end, evacuating remaining air from between the flowing preform and the walls of the mold whereby the preform is drawn into contact with the cooling walls of the mold to form a shaped article.
Also provided by the present invention is a method to prepare a thermoplastic elastomeric preform for forming or drawing into a thin walled, closed-ended, tubular article having a wall thickness of between about 0.005 and 0.25 mm, said method comprising:
i) providing a tubular mold having a longitudinal axis, a terminal end, and an opposite open end, said open end having a rim;
ii) heating a thermoplastic elastomer to a sufficient temperature to substantially eliminate the crystalline regions, whereby the viscosity and elasticity of said thermoplastic elastomer are substantially reduced, and shaping said thermoplastic elastomer to form a preform having two substantially coplanar opposing faces;
iii) cooling said thermoplastic elastomer whereby the viscosity and elasticity are recovered within a range that the preform can be drawn; and
iv) placing a face of said preform of thermoplastic elastomer on said rim.
Further provided by the present invention is a plug assembly for use in plug assisted drawing of thin walled, closed-ended, tubular articles of thermoplastic elastomer comprising an axially centered rod, said rod attached to the base of an axially centered, frustoconically shaped plug, said plug having a crown face opposite said base and extending from said crown face, an axially centered contact projection.
Further provided by the present invention is a plug assembly for use in plug assisted drawing of thin walled, closed-ended, tubular articles of thermoplastic elastomer comprising an axially centered rod, said rod attached to a first face of an axially centered, disc shaped plug, said plug having a second face opposite said first face and extending from said second face, an axially centered contact projection.
Also provided by the present invention is a condom formed from a polyesterurethane thermoplastic elastomer, said elastomer characterized by a melt index, measured at 210° C. under a 3800 g load, in the range of from 24-36 g/10 min; 10-25% by weight MDI; 0.1-5% by weight 1,4-butanediol; 70-89.9% by weight polybutylene/hexylene adipate having an average molecular weight of 1000-3000 Daltons; and 0-5% by weight lubricant.
Further provided by the present invention is a condom of thermoplastic elastomer, said condom having an axially centered tubular body, an open end and an opposite closed end, said tubular body having a maximum diameter at a point along said axis adjacent to said closed end and said tubular body having a minimum diameter at a point along said axis between said point of maximum diameter to and including said open end.
Additionally, provided by the present invention is a method to lower the modulus of a thin walled, closed-ended, tubular article of thermoplastic elastomer, said method comprising the steps of:
1) stretching said tubular article onto a forming mandrel; and
2) heating said tubular article and mandrel to a temperature of between 100 and 125° C. for a time sufficient to lower the modulus of said thermoplastic elastomer.
REFERENCES:
patent: 4359160 (1982-11-01), Myers et al.
patent: 4552717 (1985-11-01), Murley et al.
patent: 4964416 (1990-10-01), Foldesy
pa
Miller Robert G.
Miller William C.
Tankovitz Oskar T.
Brown Michael A.
Harbour John
Janssen-Ortho, Inc.
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