Note: Descriptions are shown in the official language in which they were submitted.
WO 95/23619 218 4 3 8 3 PCT/US95/02717
BLOCK COPOLYMER ELASTOMER CATHETER BALLOONS
Background of the Invention
Balloons mounted on the distal ends of catheters are widely used in
medical treatment. The balloon may be used widen a vessel into which the
catheter is
inserted or to force open a blocked vessel. The requirements for strength and
size of the
balloons vary widely depending on the balloon's intended use and the vessel
size into
which the catheter is inserted. Perhaps the most demanding applications for
such
balloons are in balloon angioplasty in which catheters are inserted for long
distances
into extremely small vessels and used to open stenoses of blood vessels by
balloon
inflation. These applications require extremely thin walled high strength
relatively
inelastic balloons of predictable inflation properties. Thin walls are
necessary because
the balloon's wall and waist thicknesses limit the minimum diameter of the
distal end of
the catheter and therefore determine the limits on vessel size treatable by
the method
and the ease of passage of the catheter through the vascular system. High
strength is
necessary because the balloon is used to push open a stenosis and so the thin
wall must
not burst under the high internal pressures necessary to accomplish this task.
The
balloon must have some elasticity so that the inflated diameter can be
controlled, so as
to allow the surgeon to vary the balloon's diameter as required to treat
individual
lesions, but that elasticity must be relatively low so that the diameter is
easily
controllable. Small variations in pressure must not cause wide variation in
diameter.
While angioplasty balloons are considered inelastic relative to balloons
used in most other applications, there is in the art a general classification
of such
balloons based on their expandability or "compliance" relative to each other.
As used
herein, "non-compliant" balloons are the least elastic, increasing in diameter
about 2-
7%, typically about 5%, as the balloon is pressurized from a inflation
pressure of about
6 atm to a pressure of about 12 atm, that is, they have a "distension" over
that pressure
range of about 5%. "Semi-compliant" balloons have somewhat greater
distensions,
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WO 95/23619 PCT/US95/()2717
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generally 7-16% and typically 10-12% over the same pressurization range.
"Compliant"
balloons are still more distensible, having distensions generally in the range
of 16-40%
and typically about 21% over the same pressure range. Maximum distensions,
i.e.
distension from nominal diameter to burst, of various balloon materials may be
significantly higher than the distension percentages discussed above because
wall
strengths, and thus burst pressures, vary widely between balloon materials.
The 6-12
atm inflation range is used in the present application to allow direct
comparison of the
compliance attributes of various balloons.
The strength of the polymer materials used in the balloons varies widely.
The strongest balloons are also the most inelastic, being made of highly
orientable
polymers such as polypropylene, polyethylene terephthalate or other phthalate
polyesters or copolyesters, and nylons. Tensile wall strengths are commonly
20,000-
50,000 psi. Commercial angioplasty balloons made of such materials with
nominal
diameters in the range of 1.5-4.5 mm have distensions in the non-compliant to
semi-
compliant range and can often be rated to pressures of 16 atm or higher
without risk of
bursting (actual burst pressures may exceed 20 atm). Generally, however, as
compliance increases the wall strength decreases. Other semi-compliant and
compliant
balloons are made of less highly orientable polymers such as ethylene-vinyl
acetate,
polyvinyl chloride, olefin copolymers and ionomer resins. The wall strengths
of
balloons made from these less orientable materials are still lower than those
made from
the highly orientable polymers, commonly in the range of 6,000-15,000 psi,
resulting in
lower rated maximum inflation pressures of 9-10 atm.
The particular distension and maximum pressure attributes of a balloon
are also influenced both by polymer type and by the conditions under which the
balloon
is blown. Angioplasty balloons are conventionally made by blowing a tube of
polymer
material at a temperature above its glass transition temperature. For any
given balloon
material, there will be a range of distensions achievable depending on the
conditions
chosen for the blowing of the balloon.
In US 4,906,244 to Pinchuck there are described balloons of nylon (i.e.
aliphatic polyamide) materials, such as nylon 12, nylon 11, nylon 9, nylon 6/9
and nylon
6/6. Like all other polymer materials the distensions of these balloons can be
determined, within a range, by controlling blowing conditions such as initial
dimensions
WO 95/23619 21843 8 3 PCT/US95/02717
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of tubing, prestretching, hoop ratio and heat set conditions. The data in the
reference
show that compliance characteristics can be obtained ranging from non-
compliant to
semi-compliant characteristics and that wall strengths of greater than 15,000
can be
obtained. The reference suggests that higher compliances can be achieved with
nylon
materials but there is no indication of what other nylons or other balloon
forming
conditions could be employed to do so.
It has also been suggested to prepare balloons of thermoplastic
elastomers in US 4,254,774 to Boretos, and polyamide elastomers have been
mentioned
among a number of possible balloon materials suggested in US 5,250,069 to
Nobuyoshi, et al, but there are many of such thermoplastic elastomer polymers
and
before the invention hereof it has been expected that performance of balloons
made
from these materials would not be generally any better than high to
intermediate
compliance made from conventional tliermoplastic polymers such as polyethylene
ionomer, polyvinyl chloride, polyethylene or ethylene-vinyl acetate.
In US 5,290,306 polyester ethers and polyetheresteramide polymers of
Shore D hardness less than 55 have been proposed for use as a sleeve or co-
extruded
outer layer to a balloon of a biaxially oriented nylon or polyethylene
terephthalate (PET)
material, so as to provide the balloon with improved softness and pin-hole and
abrasion
resistance.
Polyurethane block copolymers having flexural modulus of about
190,000 and an ultimate elongation of 250% are disclosed as balloon materials
in EP
0592885 and mention is made of also using polyester block copolymers or
polyamide
block copolymers but no suggestion is made that such alternative copolymers
could be
usefully employed if their flexural modulus was substantially lower or their
ultimate
elongation was substantially higher than the disclosed polyurethane block
copolymers.
Summary of the Invention
New balloon materials, which possess a unique combination of physical
properties including non-compliant, semi-compliant and compliant distension
attributes,
good flexibility and high tensile strength, are made from particular block
copolymer
thermoplastic elastomers characterized as follows:
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the block copolymer is made up of hard segments of a polyester or
polyamide and soft segments of polyether;
the polyester hard segments are polyesters of ttxephthalic acid
and a CZ-Cq, diol,
the polyamide hard segments are polyamides of C6 or higher,
preferably C 10 -C1Z, carboxylic acids and C6 or higher, preferably C~ o-
C 12, organic diamines or of C6 or higher, preferably C1Q-C 12, aliphatic
cw-amino-ac-acids, and
the polyether soft segments are polyethers of C2-C 10, preferably
C4-C6 diols;
the block copolymer has a low flexural modulus, narnely less than
150,000 psi, preferably less than 120,000 psi;
the block copolymer has a hardness, Shore D scale, of greater than 60;
and
the percentage by weight of the block polymer attributable to the hard
segments is between about 50% and about 95%.
From such polymers, balloons having compliant to semi-compliant
expansion profiles can be prepared with wall strengths greater than 15,000
psi,
frequently greater thaa 20,000 psi. The high strength of the balloons produced
from the
polymers allows for construction of low profile catheters and the low flexural
modulus
contributes to a softer feel found with the balloons of the invention,
compared to those
made of other high strength polymer materials. Low profile cathcters made with
the
inventive balloons have very good initial crossing, good trackability and good
recrossing after fust inflation.
Dcscription of the Drawings
Fig. I is a graph of the distension from nominal diameter to burst of
several balloons of the invention prepared from a polyamide/polyether
polyester block
copolymer using different hoop ratios to form the balloon.
Fig, 2 is a graph as in Figure 1 using an alternate polyarnide/polyether
polyester block copolymer to form the balloon of the invention.
AMEMDfD SHEET
21843.83
WO 95/23619 PCT/US95/02717
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Detailed Description of the Invention
The preferred balloons of the invention are made of polyamide/polyether
block copolymers. The polyamide/polyether block copolymers are commonly
identified
by the acronym PEBA (polyether block amide). The polyamide and polyether
segments
of these block copolymers may be linked through amide linkages, however, most
preferred are ester linked segmented polymers, i.e. polyamide/polyether
polyesters.
Such polyamide/polyether/ polyester block copolymers are made by a molten
state
polycondensation reaction of a dicarboxylic polyamide and a polyether diol.
The result
is a short chain polyester made up of blocks of polyamide and polyether. The
polyamide and polyether blocks are not miscible. Thus the materials are
characterized
by a two phase structure: one is a thermoplastic region that is primarily
polyamide and
the other is elastomer region that is rich in polyether. The polyamide
segments are
semicrystalline at room temperature. The generalized chemical formula for
these
polyester polymers may be represented by the following formula:
HO-(C-PA-C--O-PE-O)n H
Ii II
0 0
in which PA is a polyamide segment, PE is a polyether segment and the
repeating
number n is between 5 and 10.
The polyamide segments are suitably aliphatic polyanlides, such as
nylons 12, 11, 9, 6, 6/12, 6/11, 6/9, or 6/6. Most preferably they are nylon
12 segments.
The polyamide segments may also be based on aromatic polyamides but in such
case
significantly lower compliance characteristics are to be expected. The
polyamide
segments are relatively low molecular weight, generally within the range of
500-8,000,
more preferably 2,000-6,000, most preferably about 3,000-5,000.
The polyether segments are aliphatic polyethers having at least 2 and no
more than 10 linear saturated aliphatic carbon atoms between ether linkages.
More
preferably the ether segments have 4-6 carbons between ether linkages, and
most
preferably they are poly(tetramethylene ether) segments. Examples of other
polyethers
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WO 95/23619 PCT/US95/02717
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which may be employed in place of the preferred tetramethylene ether segments
include
polyethylene glycol, polypropylene glycol, poly(pentamethylene ether) and
poly(hexamethylene ether). The hydrocarbon portions of the polyether may be
optionally branched. An example is the polyether of 2-ethylhexane diol.
Generally
such branches will contain no more than two carbon atoms. The molecular weight
of
the polyether segments is suitably between about 400 and 2,500, preferably
between 650
and 1000.
The weight ratio of polyamide to polyether in the polyaniide/polyether
polyesters used in the invention desirably should be in the range of 50/50 to
95/5,
preferably between 60/30 and 92/08, more preferably, between 70/30 and 90/10.
Polyamide/polyether polyesters are sold commercially under the PEBAX
trademark by Atochem North America, Inc., Philadelphia PA. Examples of
suitable
conunercially available polymers are the Pebax 33 series polymers with
hardness 60
and above, Shore D scale, especially Pebax 7033 and 6333. These polymers are
made up of nylon 12 segments and poly(tetramethylene ether) segments in about
90/10
and about 80/20 weight ratios, respectively. The average molecular weight of
the
individual segments of nylon 12 is in the range of about 3,000-5,000
grams/mole and of
the poly(tetramethylene ether) segments are in the ranges of about 750-1,250
for the
6333 polymer and about 500-800 for the 7033 polymer. The inherent viscosities
of
these polymers are in the range of 1.33 to 1.50 dl/g.
Generally speaking, balloons of Pebax 7033 type polymer exhibit
borderline non-compliant to semi-compliant behavior and balloons of Pebax
6333
type polymer show semi-compliant to compliant distension behavior, depending
on the
balloon forming conditions.
While the Pebax -type polyamide/polyether polyesters are most
preferred, it is also possible to use other PEBA polymers with the physical
properties
specified herein and obtain similar compliance, strength and softness
characteristics in
the finished balloon.
As an alternative to polyamide elastomers, it is also possible to utilize
polyester/polyether segmented block copolymers and obtain similar balloon
properties.
Such polymers are made up of at least two polyester and at least two polyether
segments. The polyether segments are the same as previously described for the
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polyamide/polyether block copolymers useful in the invention. The polyester
segments
are polyesters of an aromatic dicarboxylic acid and a two to four carbon diol.
Suitable dicarboxylic acids used to prepare the polyester segments of the
polyester/polyether block copolymers are ortho-, meta- or para- phthalic acid,
napthalenedicarboxylic acid or meta-terphenyl-4,4'-dicarboxylic acids.
Preferred polyester/polyether block copolymers are poly(butylene
terephthalate)-block-poly(tetramethylene oxide) polymers such as Arnitel EM
740,
sold by DSM Engineering Plastics. Hytrel polymers, sold by DuPont which meet
the
physical and chemical specifications set out herein can also be used, but are
less
preferred.
It is believed important that the block copolymers have a hardness, Shore
D scale, of at least 60 and a flexural modulus of no more than about 150,000,
in order to
obtain the desirable combination of strength, compliance and softness
characteristics
which distinguish the inventive balloons. Preferably the Shore D hardness is
in the
range of 65-75 and the flexural modulus is in the range of 50,000-120,000. The
preferred polymers useful in the invention are also characterized by a high
ultimate
elongation of about 300% or higher and an ultimate tensile strength of at
least 6,000 psi.
The balloons of the invention are made using known techniques for
forming catheter balloons. For coronary angioplasty catheter balloons (balloon
diameters of about 1.5-4.0 mm), single wall thicknesses of less than 0.001
inches,
preferably less than 0.0007 inches, are readily obtained. Wall strengths for
such
balloons are in excess of 15,000, typically at least 18,000 psi, and in most
cases in the
range of about 20,000 to 32,000 psi. For peripheral angioplasty, balloons of
up to 10
mm diameter may be used and in such cases somewhat thicker walls may be
employed.
Even with a 10 mm balloon, wall thicknesses of about 0.0015 mm or less can be
employed to provide balloons with burst pressures of at least 10 atm. Suitably
the
balloons are formed by expansion of tubing at a hoop ratio (mold
diameter/tubing ID) of
between 3 and 8, preferably between 4 and 7.
The following examples illustrate the preparation and unique properties
of balloons of the invention.
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EXAMPLES
TUBING EXTRUSION:
In examples 1-9, 11 and 13 all tubing materials were made from
Atochem Pebax 7033 and Pebax 6333 by extrusion. Polymer pellets were dried
to
less than 0.10 wt% moisture content before extrusion. Tubing was extruded at
melt
temperature range of 200 C to 220 C by hot feedthroat through seven extruder
zones
with controlled temperatures. The extrusion conditions were based upon
manufacturer's
recommended polymer processing conditions. After the polymer material extruded
out
of the die in tube form it passed through a small air gap and was cooled in a
deionized
water bath maintained at about 65 F. A puller was used to pull the tube
through the
water bath. After passing through the puller, the extruded tubing was cut into
8 inch
sections or spooled. A variety of tubing sizes were made by this method.
EXAMPLE 1
The product of this example is a 2.25 mm balloon made from Pebax
7033. This polymer has a Shore D hardness of 69, a flexural modulus of 67,000,
an
ultimate tensile strength of 8,300 psi and an ultimate elongation of 400%. The
tubing
sections had an OD of 0.0270 inch and an ID of 0.0179 inch. In order to form a
2.25
mm balloon with a 20 mm body length, a mold having dimensions that allowed the
tube
to blow out to the appropriate body size and balloon waist inner diameters was
used.
After the tubing section was securely inside the mold, the mold was
placed in a holder. The tubing section extended out the top of the mold and
was fed into
a Touhy clamp through which nitrogen gas applied to the inner lumen of the
tubing at
280 psi with tension applied to the tubing. The tubing section at the bottom
of the mold
was clamped off such that the pressure was maintained inside the tubing
section. The
mold was then gradually dipped into a deionized hot water bath maintained at
90 C
(tl C) to a point just above the proximal waist portion of the mold at a
controlled
manner. A balloon was formed by radial expansion with internal pressure using
a hoop
ratio of 5.1. After the balloon formed, the mold was removed from the hot
water bath
and cooled for approximately 10 sec in a deionized water bath maintained at
about
10 C.
Balloons prepared in this manner were subjected to standard burst tests
by measuring the double wall thickness of the deflated balloon, inflating the
balloon at
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WO 95/23619 PCT/US95/02717
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incrementally increasing pressures and measuring the outside diameter at each
increment until the balloon burst. Burst strength, distension and balloon wall
strength
were calculated from the data obtained. Average results are given in Table 1.
EXAMPLE 2
The product of this example is a 3.00 mm balloon made from Pebax
7033. The tubing sections had an OD of 0.0290 inch and an ID of 0.0179 inch. A
3.00
mm size mold was used to produce the balloons. These 3.00 mm balloons were
made
by the same procedure used in example 1, except for the water bath temperature
and
internal blowing pressure. The water bath temperature and the pressure were
maintained at 95 C and 300 psi, respectively. The hoop ratio of the balloon
was 6.2.
The results of testing for burst, distension and wall strength are also listed
in Table 1.
EXAMPLE 3
The product of this example is a 3.00 mm balloon made from Pebax
.7033. The tubing sections had an OD of 0.0316 inch and an ID of 0.0179 inch.
A
corresponding size mold was used to mold balloons. In this example, 90 C water
bath
and 400 psi internal blowing pressure were used. The test results provided in
Table 1
show that these balloons gave a higher burst pressure than the previous
examples.
EXAMPLE 4
The product of this example is a 3.00 mm balloon made from Pebax
7033. The tubing sections had an OD of 0.0320 inch and an ID of 0.0215 inch. A
3.00
mm size mold was used to produce the balloons. The same molding conditions
described in example 2 were used except that the tubing was prestretched at
room
temperature before molding balloons. The prestretch stretching ratio X was 1.5
in this
example. The test results of this example are listed in Table 1.
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Table 1. Burst and Distension Test Results of Pebax 7033 Material (averages
of at least 5 balloons).
Single Wall Burst Distension Distension Distension Wall
Balloon Size Thickness Pressure 88 psi-Burst 88 psi - 132 88 psi - 176
Strength
Exam le (mm) (inch) (psi) % psi (%) psi (%) (psi)
1 2.25 0.00042 230 21.3 4.2 10.9 25400
2 3.00 0.00041 230 12.7 3.2 7.1 29200
3 3.00 0.00060 260 12.8 3.6 6.9 25900
4 3.00 0.00049 220 23.5 4.4 9.0 26300
EXAMPLE 5
Balloons having 2.0-3.0 mm diameters were prepared from Pebax 7033
using hoop ratios of 4.6, 5.1 and 6.7. The balloons were expanded
incrementally at
.37 C until they burst. The results, plotted in Figure 1, show semi-compliant
curves
with very high burst strengths ranging from 15-18 atm and maximum distensions
at
burst of 24% - 45%.
EXAMPLE 6
In this example, balloons were made from Pebax 6333. This polymer
has a Shore D hardness of 63, a flexural modulus of 49,000, an ultimate
tensile strength
of 8,100 psi and an ultimate elongation of 3 00%. The same balloon forming
procedure
as in example I was used, except as noted below. The product of this example
is a 2.5
mm balloon. The tubing sections had an OD of 0.0316 inch and an ID of 0.0179
inch.
A 2.5 mm size mold was used to produce the balloons. In this example, a 95 C
water
bath and a 300 psi internal blowing pressure were used. The hoop ratio for
blowing the
balloon was 5.5. The results of burst, distension and wall strength are shown
in Table 2.
EXAMPLE 7
Pebax 6333 tubing with an OD of 0.0310 inch and an ID of 0.0170
inch was used to produce 3.0 mm balloon. The water bath temperature was 90 C
and
the internal blow pressure was 300 psi. The hoop ratio for blowing the balloon
was 6.9.
Test results are shown in Table 2.
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Table 2. Burst and Distension Test Results of Pebax 6333 Material (averages
of at least five balloons)
Single Wall Distension Distension Distension
Balloon Size Thickness Burst 88 psi-Burst 88 psi - 132 88 psi - 176 Wall
Example (mm) (inch) Pressure ("/o) psi psi Strength
(psi) (%) ( /u) (psi)
6 2.50 0.00058 220 33.7 3.4 17.4 19900
7 3.00 0.00049 210 17.1 4.2 9.7 26100
EXAMPLE 8
Balloons having 2.25-3.0 mm diameters were prepared from Pebax
6333 using hoop ratios of 4.2, 5.5 and 6.9. The balloons were expanded
incrementally at
37 C until they burst. The results, plotted in Figure 2, show semi-compliant
and
compliant curves with burst strengths of 11.5-14 atm and distensions at burst
of 23% -
69%.
EXAMPLE 9
The products of this example were 3.00 mm balloons made from Pebax
6333. The tubing sections had an OD of 0.0350 inch and an ID of 0.0190 inch. A
3.00
mm size mold was used to produce the balloons. Portions of the tubing sections
were
prestretched at a stretching ratio of 2(X=2) before molding the balloons. The
prestretched portions were on either side of a central 8 mm unstretched
portion
protected during the prestretching operation by a clamp. The unstretched
central portion
was then formed into a 20 mm long, 3.0 mm diameter balloon body by expansion
under
pressure in a mold as in the previous examples. The temperature of the water
bath was
95 C and the expansion pressure was 340 psi. The balloons made in this manner
had a
hoop ratio of 6.2, a single body wall thickness of between 0.0006 and 0.0007
inches, a
distal waist wall thickness of between 0.0014 and 0.0021 inches a proximal
waist wall
thickness of between 0.0014 and 0.0018 inches. The burst pressure of the
balloons was
about 270 psi. The balloon distension was semi-compliant.
EXAMPLE 10
The material used in this example was Arnitel EM 740 sold by DSM
Engineering Plastics. This polymer had a Shore hardness of 74D, a flexural
modulus
120,000 psi, an ultimate tensile strength of 6,400 psi and an ultimate
elongation of
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340%. 2.25 mm Balloons were prepared from tubing of dimensions OD = 0.0270
inches
and ID = 0.0179 inches. The tubing was necked at two ends and the balloon body
portion was unstretched, as described in Example 9. The molding temperature
was
80 C. The molding pressure was 290 psi. The molding tension was 50 grams.
Balloon properties are given in Table 3.
Table 3: Burst and Distention Test Results of Arnitel EM 740 Material
Example Balloon Size Single Burst Distention Distention Distention Wall
(mm) Wall Pressure 88-Burst 88-132 88-176 Strength
Thickness (psi) % % % (Psi)
(inch)
11 2.25 0.00041 238 34 6.2 16.7 25,700
EXAMPLE 11
The material used in this example was Pebax 7033. The molding
temperature was 95 C. The molding pressure was 500 psi. 2.00 mm Balloons were
prepared from tubing segments as set forth below. All tubing segments were
stretched at
room temperature with different stretching ratios and starting tubing
dimensions. The
unit of ID and OD is inches.
a: the tubing was stretched at X = 2.5 stretching ratio
starting ID = 0.0130, OD = 0.0252
ending ID = 0.0087, OD = 0.0177
b: the tubing was stretched at X = 3.0 stretching ratio
starting ID = 0.0132, OD = 0.0252
ending ID = 0.0081, OD = 0.0162
c: the tubing was stretched at X = 4.5 stretching ratio
starting ID = 0.0132, OD = 0.0262
ending ID = 0.0064, OD = 0.0136
The properties of the resulting balloons are set forth in Table 4.
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Table 4: Burst and Distention Test Results of Pebax 7033 Material
Example Balloon Single Burst Distention Distention Distention Wall
Size Wall Pressure 88-Burst 88-132 88-176 Strength
(mm) Thickness (psi) % % % (Psi)
(inch)
12 a 2.0 0.00058 279 14.6 4.0 6.5 18,900
12 b 2.0 0.00060 279 14.6 3.5 6.6 18,300
12 c 2.0 0.00062 353 22.2 3.0 5.4 22,600
EXAMPLE 12
The material used in this example was Arnitel EM 740 poly(butylene
terephthalate)-block-poly(tetramethylene oxide). 2.75 mm Balloons were
prepared
from tubing of dimensions: OD = 0.0390 inches and ID = 0.0230 inches. The
tubing
was stretched at room temperature at ~, = 4.8. The dimension of stretched tube
was:
OD = 0.0250 inches and ID= 0.0200 inches. The molding temperature was 80 C.
The molding pressure was 490 psi. The molding tension was 30 grams. The
properties of the resulting balloons are set forth in Table 5.
Table 5: Burst and Distention Test Results of Arnitel EM 740 Material
Example Balloon Single Wall Burst Distention Distention Distention Wall
Size (mm) Thickness Pressure 88-Burst 88-132 88-176 Strength
(inch) (psi) % % % (Psi)
13 2.75 0.00066 265 43.9 8.0 18.2 21,700
EXAMPLE 13
Pebax 7033 tubes with dimensions 0.0198 inch OD and 0.0339 inch
ID is drawn at room temperature with a central region protected by an inserted
hypo
tube approximately 0.018 inch in diameter and 1.0 inch in length. The tube was
drawn until an 8 mm central region remained undrawn. Ten sterilized balloons
(3.0
mm in diameter and 20 mm in length) with an average double wall thickness
0.00142
inch are made by radially expanding the 8 mm central tubing portion at 95 C.
The
resulting burst pressure is 270-280 psi and the distension is 9% over the
range 88-176
psi and 16% over the range 88-235 psi.
COMPARATIVE EXAMPLES
COMPARATIVE EXAMPLES A-C
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The material used in this example was Pebax 3533. This polymer has a
Shore D hardness of 35 and a flexural modulus of 2,800. Balloons were made by
expanding tubes of ID = 0.0330 inch and OD = 0.0480 inch. The molding
temperature
was 66 C. The molding pressure was 80 psi. Distension and burst were run at
room
temperature (22 C). Balloon properties are set forth in Table 6.
Table 6: Burst and Distention Test Results of Pebax 3533 Material
Comparative Balloon Size Single Wall Burst Distention Wall
Example (mm) Thickness Pressure 10-Burst Strength
(inch) (psi) % (Psi)
A 1.50 0.00495 75 67 450
B 2.00 0.00218 50 89 900
C 2.50 0.00185 40 73 1060
COMPARATIVE EXAMPLE D
The material used in this example was Pebax 5533. This polymer has a
Shore D hardness of 55 and a flexural modulus of 29,000. 3.00 mm balloons were
prepared from tubing sections having an ID of 0.0190 inch and an OD of 0.0360
inch.
The molding temperature was 87.5 C. The molding pressure was 300 psi. Portions
of
the tubing sections were prestretched at a stretching ratio of 2(X=2) before
molding the
balloons. The prestrctchcd portions were on either side of an 8 mm central
unstretched
portion protected during the prestretching operation by a hypo tube as in
example 13.
The unstretched central portion was then formed into a 20 mm long, 3.0 mm
diameter
balloon body by expansion under pressure in a mold. Balloon properties are set
forth in
Table 7.
Table 7: Burst and Distention Test Results of Pebax 5533 Material
Comparative Balloon Single Wall Burst Distention Distention Distention Wall
Example Size Thickness Pressure 88-Burst 88-132 29.4-Burst Strength
(mm) (inch) (psi) % % % (psi)
D 3.00 0.00073 132 17.0 17.0 44.3 10,700
COMPARATIVE EXAMPLES E-G
The material used in this example was Riteflex 640 poly(butylene
terephthalate)-block-poly(tetramethylene oxide). This polymer has a Shore D
hardness
of 40 and a flexural modulus of 12,300. Balloons were made by expanding tubes
of ID
CA 02184383 2005-08-26
-15-
= 0.0360 inch and OD = 0.0430 inch. The molding temperature was 80 C. The
molding pressure was 80 psi. Balloon properties are set forth in Table 8.
Table 8: Burst and Distention Test Results of Riteflex 640 Material
Comparative Balloon Size Single Wall Burst Distention Wall
Example (mm) Thickness Pressure 10-Burst Strength
(inch) (psi) % (Psi)
E 1.50 0.00216 80 66 1100
F 1.75 0.00105 65 52 2100
G 2.25 0.00088 60 62 3020
