Appeal No. 96-3717
Application 08/229,115
[t]he organic polymer formulating the medical tube of the present invention has a
mechanical loss tangent (tan * ) of at least 0.5 at body temperature .... Where tan * isJ J
less than 0.5, the tube is so stiff as to thrust against the surrounding tissue while inserted in
the body, and gives a feeling of physical disorder ....
The medical tube of the present invention has a modulus of transverse elasticity (G ) of 1-
J
1000 MPa at body temperature .... With a G over 1000 MPa, said medical tube always
J
thrusts against the surrounding tissue due to the exceeding stiffness thereof while inserted
in the body, and gives a feeling of physical disorder, which is the same defect as that of the
tube having a tan * of less than 0.5. On the other hand, those having a G of less than 1J J
MPa can be squeezed by internal pressure due to a low mechanical strength. Since
cannula, ED catheter, etc. are usually indwelled in the body for a long period, it is desirable
to reduce the feeling of physical disorder to the least possible extent.
* * *
The preferred medical tube is made of an organic polymer having a water absorption of
not more than 5 wt% .... When the water absorption exceeds 5 wt%, the swollen tube
presses the surrounding tissue and gives a feeling of physical disorder ....
From the viewpoint of penetration force, the medical tube of the present invention desirably
has the above-mentioned flexibility after being inserted into the body, namely, at body
temperature, and has a sufficient rigidity at room temperature before the insertion, or at a
low temperature artificially prepared (e.g. 10-15E C).
As pointed out, supra, Solomon discloses that his catheter can comprise a polyurethane. He
discloses two polyurethanes having water absorption of less than 5 wt%. In addition, Solomon discloses
that his “catheter must be stiff enough to be inserted into, for example, a blood stream, without kinking” and
that “once in contact with the blood, it should preferably soften and become sufficiently flexible to bend and
be advanced through the tortuous path of the vessel” (col. 4, lines 14-20). Solomon further discloses that
polyurethane 80 A and 55 D meet this mechanical criteria (col. 4, lines 21-34). While Solomon is silent
as to components of the polyurethanes and the molar ratios of the components, in the absence of any
-7-
Page: Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Next
Last modified: November 3, 2007