Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE DISCLOSURE
Many potting systems which have been developed
in the past have been used in biomedical devices, such as
the hollow-fiber artificial kidney, to form the so-called
"tube sheets". They, however, have met with limited
success. Among the resins used in these potting compounds
are polyolefins, wax-extended polyolefins, polyolefin
copolymers, polyamides, polystyrene, polyvinyl chloride,
silicone rubbers, epoxy resins and the like. However, all
the above resins have been found deficient in one aspect
or another, and, therefore, it is desirable to produce a
system which is more acceptable to the medical field.
Many of the above resins have long cure times
which cause delays in production. Also, unless centrifical
casting is used to produce the tube sheets, wicking of the
polyurethane up the hollow-fibers occurs, which is very
undesirable because it tends to create irregularities in
the "tube sheet" which, could cause leaks, and because it
reduces the surface area of the hollow-fibers. Slow curing
systems and wicking of the polyurethane resin can be
eliminated by the use of catalysts such as organo-metallic
compounds or tertiary amines, however, the use of these
types of catalysts in the "tube sheet" is prohibited
because of their toxicity if absorbed into the blood.
We have found that we can achieve the fast
cure necessary to eliminate the wicking problems without
resorting to the use of viscous polyurethanes by using
Quadrol~ as a reactive catalyst. Quadrol~ is N,N,
N',N'-tetrakis (2-hydroxypropyl) ethylene diamine. The
initial mix viscosity of the urethane system must be low
in viscosity if good penetration of the urethane into
A
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the bundle of hollow-fibers is to be obtained. However,
if the viscosity does not increase rapidly wicking will
occur. We have found that the use of Quadrol will cause
the viscosity of the urethane system to increase rapidly
without markedly increasing the initial mix viscosity of
the system.
Apparently Quadrol has catalytic activity due
to its tertiary nitrogens. Its four hydroxyl groups react
with the isocyanate chemically bonding it to the polymer
structure of the urethane "tube sheet", and as such, it
does not present a toxicity problem.
In the instant invention a two component system
is prepared and when the two components are reacted with
one another, a superior fast curing non-wicking casting
system is produced which is toxicologically more
acceptable.
SUMMARY OF THE INVENTION
The present invention relates to a hollow fiber
separatory device capable of use in biomedical applications
comprising a hollow fiber bundle consisting of a piurality
of fine hollow fibers whose end portions are potted in a
tube-sheet and whose open fiber ends terminate in a tube-
sheet face, the resulting bundle being sealed within a
casing to form a separatory cell having one or more fluid
ports which allow for the passage of one fluid through the
fibers and another around the fibers without mixing of the
two fluids, said tuhe-sheet comprising a cured polyurethane
composition comprising the reaction product of (1) a polyol
mixture of (a) at least one polyol, and (b) N-N-N'-N'-
tetrakis (2-hydroxypropyl) ethylene diamine, and (2) an
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isocyanate terminated polyurethane based prepolymer, said-
diamine being present in said polyol mixture in an amount
sufficient to cause the viscosity of the urethane system
- to increase rapidly upon mixing of said polyol containing
mixture and said prepolymer to form a gel which turns to a
solid upon standing without markedly increasing the initial
mix viscosity of the urethane system, thereby permitting
placement of said urethane system and substantially reduc-
ing wicking of said urethane system after placement, said
amount providing a ratio of equivalents of the N-N-NI-N'-
tetrakis (2-hydroxypropyl) ethylene diamine to the polyol
of from 5:95 to 40:60, and said polyol and said prepolymer
being reacted in amounts to provide an NCO:OH equivalent
ratio of about 1 to 1.1:1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polyols which may be employed in conjunction
with Quadrol include castor oil, esters of castor oil,
polyethers such as polyoxypropylene glycol and polytetra-
methylene glycol, homopolymers or copolymers of hydroxyl
bearing butadiene, and hydroxyl bearing polyesters, such
as polyethylene glycol adipate and the like and combina-
tions thereof.
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lllS893
As stated above, the equivalents ratio of Quadrol to
polyol used to cure the isocyanate terminated prepolymer falls
within the range from 5:95 to 40:60.
The isocyanate terminated prepolymer is preferably
formed from an aromatic diisocyanate such as 4-4'diphenylmethane
diisocyanate, however, a cycloaliphatic diisocyanate such as
3-isocyanato methyl, 3,3,3-trimethylcyclohexyl isocyanate (IPDI)
may also be employed. The useable isocyanates for making the
prepolymers in this invention also include aliphatic and aro-
matic diisocyantes such as polymethylene poly (phenylene iso-
cyanate), tolylene diisocyanate (TSI), 1,5-naphthalene diiso-
cyanate, phenylene diisocyanates, or mixtures of these materials,
4,4'-methylene bis(cyclohexyl isocyanate) and hexamethylene
diisocyanate, as well as related aromatic and aliphatic iso-
cyanates, which may also be substituted with other organic
or inorganic groups that do not adversely affect the course
of the chain-extending and/or cross-linking reaction.
Formation of the isocyanate terminated prepolyer is
accomplished by reacting an excess of one of the preceding
isocyanate components with a polyol having a relatively high
molecular weight of between about 400-6000. Among the polyols
useful in formation of the isocyanate terminated prepolymer
are those selected from compounds based essentially on poly-
- butadiene, castor oil, esters of castor oil or hydroxyl bearing
polyethers or combinations of them.
Suitable polyether polyols include aliphatic alkylene
glycol polymers exemplified by polypropylene ether glycol and
poly 1-4 butylene ether glycol. Also trifunctional compounds
exemplified by the reaction product of trimethylol propane or
~lycerine with propylene oxide may be exployed as the polyol
constituents.
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1115893
The polybutadiene based polyols are liquids that are
founded on hydroxyl terminated liquid butadiene homopolymers
and hydroxyl terminated butadiene copolymers with styrene.
In order to prepare the non-wicking casting system
of the instant invention, the polyol containing the Quadrol is
merely admixed with the isocyanate terminated prepolymer and
the liquid mixture rapidly forms a gel which turns to a solid
mass upon standing.
The non-wicking feature of the casting system is
determined by placing the ends of a bundle of hollow-fibers
into the liquid mixture before the mixture turns to a gel. The
degree of wicking (capillary action) is determined by the dis-
tance the liquid mixture rises into the hollow-fibers before
the liquid forms a gel.
By using the polyols containing Quadrol described
above and mixing them with the previously described isocyanate
terminated prepolymers, substantially non-wicking urethane
systems are produced.
In order to describe more fully the instant invention
the following examples are presented.
EXAMPLE 1
In this example the prepolymer employed was prepared
as follows:
204 grams of a 400 molecular weight polyoxypropylene
glycol (0.966 eq), 205 grams of castor oil (0.599 eq) and 795
grams MDI (6.360 eq) were added to a reactor and flushed with
nitrogen. The temperature was raised to 75C. and maintained
at 70-80C. for 2 hours. The resulting prepolymer had an NCO
content of 16.7~.
272 grams of this prepolymer were mixed with 325 grams
of castor oil and 3.6 grams of Quadrol at room temperature.
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~iS893
The end of a bundle of hollow-fibers were inserted into the
liquid mixture to a depth of 1 inch. The mixture formed a gel
in 70 minutes and turned solid while standing overnight. Before
forming the gel, the liquid rose 4.2 cm in the hollow-fibers,
the height of the rise recorded as the amount of wicking.
The operational details and the results obtained are
recorded in the Table.
EXAMPLES 2-4
In these examples the procedure of Example 1 was
repeated except that various amount of Qudrol were added to
the polyol. Again, the details and results are recorded in the
Table along with Control Run A which contained no Quadrol.
From the data, the degree of wicking is dependent
upon the amount of Quadrol employed.
EXAMPLES 5-8
In these examples the prepolymer used was prepared
by admixing 1530 grams ~3 eq) of a 1000 molecular weight poly-
oxypropylene glycol, 2835 grams of a polymethylene poly(phenyl-
eneisocyanate) (21 eq) having an isocyanate functionality o~
approximately 2.2, and 2.2 grams of benzoyl chloride in a
reactor and flushed with nitrogen. The temperature was rai~ed
to 65C. and maintained for 1.5 hours at 60-70C. The resulting
prepolymer had an NCO content of 17.2~.
Various amounts of this prepolymer were mixed with
polyoxypropylene glycol triol (600 MW) containing various amounts
of Quadrol. Upon immersing hollow-fibers in the mixture, the
amount of wicking was determined and recorded in the Table
along with Control Run B which contained no Quadrol.
EXAMPLES 9-12
The prepolymer used in these examples were formed
by admixing 342 grams of castor oil (1 eq) and 1188 grams (9 eq)
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1115893
of a polymethylene poly(phenyleneisocyanate) having an iso-
cyanate functionality of 2.7 in a reactor and flushed with
nitrogen. The temperature was raised to 60C. and maintained
at a temperature of 60-70C. for 1.5 hours. The resulting
prepolymer had an NCO content of 21.5%.
Various amounts of this prepolymer were mixed with
castor oil containing varying quantities of Quadrol. The
operational details and results obtained are also recorded in
the Table along with those of Control Run C which contained
no Quadrol.
From the above description and by the examples
presented, it has clearly been shown that wicking may be held
to a minimum when a polyol containing a Quadrol is admixed with
an isocyanate terminated prepolymer as described above.
While this invention has been described and illus-
trated by the examples shown, it is not intended to be strictly
~imited thereto, and other variations and modifications may be
employed within the scope of the following claims.
1115893
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