Note: Descriptions are shown in the official language in which they were submitted.
b5
1--
Background of the Invention
The present applica~ion relates generally to
medica~ plastic formulations and particularly to medical
liquid containers such as flexible, collapsible9 intra-
venous solution containers. The materials disclosedexhibit the particular advantages of being essentially
transparent, soft and flexible, essentially free of
extractables, and able to res:ist high temperatures
present in autoclaving.
Various materials have been utilized for intra-
venous solution containers in the past. In particular,
'~ U.S. Patent No. 4,140,162 discloses a formulation for
medical liquid containers containing both polypropylene
and a block copolymer. A third ingredient disclosed
comprises polyethylene or polyethylene vinyl acetate.
The present invention is distinguished from the '162
patent by the use of ethylene methyl acrylate, which is
lower in cost and provides more desirable physical
properties such as improved thermal stability and a
wider range of processing temperatures. Other formula-
tions of block copolymers which include polypropylene
may be found in U.S. Patent No. 3,792,124. These formu-
lations are not suitable for flexible medical liquid
containersf however, in that they are ionic, which
would alter the solutions con-tained therein.
Summary of the Invention
In accordance with this invention, a clear,
flexible, thermoplastic material is provided, capable of
being processed into hollow shapes by conventional plas-
tic processing Methods and subsequently autoclaved. Thematerial comprises: (A) from about 40 to 70~ by weight
of a polyolefin, usually polypropylene admixed with (~)
from about 5 to 40~ by weight of an ethylene loweralkyl
acrylate; and (C) from about 5 to 40~ by weight of one
of several block copolymers: ethylene butylene having
terminal polystyrene units, butadiene styrene having
terminal polystyrene units, an olefin elastomer of the
--2--
ethylene propylene type, or butyl rubber (polybutadiene
isoprene).
Ingredient (A) as described above is a poly-
olefin consisting essentially of polyprop~lene units.
Many commercial varieties of polypropylene contain
small amounts of ethylene units. This does not make a
major impact on the properties of the propylene material.
Ingredient (B) generally comprises ethylene
methyl acrylate (EMA) and is commercially available from
Gulf Oil Chemicals Co., Orange, Texas, under the numbers
2205 and 2255. EMA is a random copolymer consisting of
a polyethylene backbone with methyl acrylate side
branches. Gulfls present commercial product contains
approximately 20~ by weight of methyl acrylate. EMA's
distinguishing properties include a low melt temperature
and corresponding easy heat sealability, as well as
good thermal stability in the range of 600 to 630~ F.,
and "rubbery" mechanical properties, including low
stiffness, high elongation, clarity and high impact
strength. A comparison of ethylene methyl acrylate to
ethylene vinyl acetate may be seen in the following
Table I:
Table I
EMA EVA
Processing Ranye, F 300-620 450 Max
Thermal StabilityExcellent Poor
Corrosive Possibility No Yes
Pellets Require
Protection from Moisture
During Storage No No
Moisture BarrierFair Fair
Adhesion to Substrates:
Paper Excellent Excellent-Good
OPP Excellent Poor
Cellophane (PVDC-Coated) Excellent Poor
Aluminurn Foil (Unprimed) Poor Poor
Price, ~/Lb. 59-1/2 41-1/2-61-1/2
_ ~/cu. in. _ 2 1.4-2.0
-- 3 --
The general mecha.nical properties of E~ may be
ound in Ta~l~ II below w~en co~pared to low density
polyethylene (LDPE).
Table II
Pro~ert~ Compariso _ f EMA to LDPE
EMA L~PE
Melt Index ~4 2
Density/ gm/cc 0~942 0~917
Vicat Softening
Point, ~ 138 ~194
Tensile StrO psi 162~ 1~50
Elongation, ~ 720 650
~ardness, 5hore D 35 46
Flex, stif~ness, psi4000 18~500
Stress Crack Resist~No 90%
(Hostapal9 122 F) Failures Failures
Dielectric Constant
@ 100 k~z 3.1 203
Dissipation Factor
@ 100 KhZ 0.015 000002
Low ~emp. Brittle- ~o 10%
ness to -105Y .Failures Failures
.... .. . .
Price/ ~e~/lbO 59-1/2 43-1/2
~/cu. in. 2 1.4
As shown in Table II, the most notable property changes
brought about by the copolymerization of ethylene with
methyl acrylate are: depression of melting point, signi~
ficant reduction in flexural modulus, and improvement
in stress crack resistance. A key attribute of EMA resin,
compared with other copolymers of low density polyethyl-
ene is LMA's great thermal stability. EMA can be processed at very hi~h temperatures; up to 600 to 630Fo
without polymer breakdown and/or chain cission. Some of
the other low density polyethylene copolymers, like
EVA, when mixed with high temperature-resistant plastics
3S such as polyprolpylene and high density polyethylene and
heated in exces3 o~ 450F. begin to break down and
liberate acids that attack metal surfaces of extrusion
equipmentO
Although EMA is the preferred em~odiment of
element B o the mater~al, o-ther loweralkyl ethylene
acrylates may be utilized ~uch as ethylene ethyl acrylate
and ethylene butyl acrylate, with similar results.
'Loweralkyl" is defined as an alkyl group having 1-5
carbon atoms, such as ethyl, methyl~ ~utyl~ etc.
The third element ~C~ of this novel plastic
material comprises from abcut 5 to 40% ~y weight of a
thermoplas~ic composition; usually a ~lock copolymer oP
ethylene bu*ylen2 having ~erminal polystyrene uni-ts~
Ethylene butylene blook copolymers having terminal
polystyrene units are commerically available under ~he
trademark Kraton G~ from the Shell Chemical Co. Other
rubbery ~lock copolymers such as bu~adiene styrene havin~
terminal polystyrene units may also be utilized. For
example, ~he impermeable polymeric compositions ~isclosed
in U.S. Patent 3,686~364 assigned to Polymer Corporation
Limitedl discloses a series of ~utadiene styrene block
copolymers useful as the thîrd element in ~le present
~0 applicationO Similarly, the ~lock copolymers disclosed in
U.S. Patent 3,865,776 assigned to S~ell Oil Co~pany, may
also be utilizedO Similarly, U.S. Patent 3,970,71~ assigned
to Philips Petroleum Company discloses block copolymers
wherein alpha olefins and/or mixtures of alpha oleflns
are manufactured. These are sold under the trademark
Solprene 406, 411, 414 and 475 and may also ~e utilized.
Ethylene propylene dienemonomer, available from Exxon aa
Vistalon* #721, #404, #457, #714, #707 or #71g, or ethylene
propylene dienemonomer elastomer, avaîlable from ~eisler
Corporation under the num~er XC-5214, may also be used
a~ the third îngredient of the material. Polyisobutylene
elastomers 301d by Exxon as LM Vistanex*, ~istanex* MML-80,
100 and 120 and igobutylene isoprene copolymers such as
Exxon Butyl 077 ancl butyl rubber, from Polysar of Canada,
may also be utiliæed as the thîrd ingredient.
*trade mark
PC/~b _
-5
The following Table III discloses a series of
examples of the above listed material, showing in particu-
lar, the proportionate ~ercentages~ by weight, of elements
A~ B and CO
Table III
Preferred Embodi~ents
PP EMA EEA KRATON
MATZ 10D 90~ 10%
t2205)
70~ ~30%
MATZ 7D 80~ 20%
(2255~
70~ 30%
MZO3-3 70% 30~
7~ 30%
~n a preferred embodiment9 10~ ethylene methyl acrylate
was mixed with 90% polypropyleneO The resultiny combi-
nation was t~en mixed in a proportion of 70~ EMA polv~
propylene to 30% element C. The resulting material
exhibited the following properties, as seen in Table IV.
# The particular grade of Kraton~ was G-27~5 and
contains pol~propylene and approximately 42% by
weight o mineral oil~ This results in the final
composition haYing the mineral oil present in an
amount of approximately 12.75~ by weight.
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--7--
In addition, the resultiny formulation was
found to be highly suitable for sheet extrusion, injec-
tion molding or blow moldiny into flexible, transparent,
autoclavable intravenous solution containers. In par-
ticular, the resulting container was found to be ofsufficient strength to withstand heavy impact during
shipment and use, while at the same ~ime being suffi~
ciently flexible to collapse easily during drainage of
intravenous solution from the container.
The following examples further illustrate
specific embodiments of the invention.
--8--
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A block copolymer having thermoplastic rubber
characteristics consisting essentially of a rubbery
olefin polymer of generally equal proportions of ethylene
5 and butylene units in terminal blocks of polystyrene was
added to a rotational mixer in the amount of 40~ by
weight with 10% by weight of a blend of 90~ polypro~ylene
and 10% EMA. The block copolymer used was Kraton~ 2705
sold by the Shell Chemical Company. Mechanical proper~
ties of Kraton~ 270S are as follows:
~ardness, shore A 52
Tensile propertiesy ASTM D~412
Tensile strength~ psi 1650
Elon~ation at break 800
Modulus at 100% extension, psi 200
Set after break/ % 55
Tear strength, pli (ASTM D-624)130
Compression set at 70C, % (ASTM D-395) 32
Yerzley resilience, % (ASTM D-9453 75
2~ Specific gravity 0.g0
The ingredients were premixed in the rotational mixer
- and then introduced into an extruder for extrusion
into a rodO The rods were then chopped into smaller
pellet sized pie~es. The chopped pellets were utilized
2S in the commercially available blow molding apparatus,
specifically a continuous extrusion machine, with a
secondary blow station manufactured by Romellog Fell-
bach of Oeffingen. The material was found to be 5UC-
cessfully fabricated into a tran~parent, flexible, col-
lapsible intravenous solution container which was auto-
clavable under a typical sterilizing cycle without an
distortion.
The above listed percentages were duplicated
35 . util.izing as ~lement C of the composition, a different
block copol~ler, said block copolymer being either a
linear or a branched block copolymer having at least two
,i."' ~
~10--
polymer blocks A and at least one polymer block B, each
polymer block A being selected from the group consisting
of monoalkenyl arene polymers and hydrogenated products
thereof wherein no more than 25~ of the arenedouble
bonds had been reduced and polymer block B is a hydro-
genated polymer block of a C4~5 conjugated diene polymer
wherein at least about 30% of the aliphatic unsaturation
has been reduced by hydrogenation. Speci~ically~ each
polystyrene block has an average molecular weight be-
~ween about 2,000 and 50~000 and the hydrogenated poly
butadiene block has an average molecular weight between
about 20,000 and 300pOOOO
A bloc~ copol~mer of general form polyalpha
methyl~styrene-polybutadine-polyethylmethl styrene
(hereinafter referred to as alpha~beta-alpha block co
polymer) was prepared and blended with uncured butyl
rubbarD The alpha-beta-alpha block copol~mer had an
alpha methyl styrene content of approximately 35% weight
and a molecular weight of about 60,000~ Three separate
blends were prepared using 30, 40 and 50 parts b~ weight
of butyl rubber respectively with 100 parts by weight
of alpha-beta-alpha block copolymer. The blending was
carried out on a micromil, the mil rolls were at
elevated temperatures in the range of about 130C. to
about 150C~ The resulting blends were then admixed
with components A and B as previously described.
In this Example, the same percentages of ele~
ments A an~ B of the composition are disclosed in Example
2. Element C comprises 10~ by weight of a thermoplastic
composition comprising a block copolymer having at least
two monoalkenyl arene polymer blocks and at least one
substantially completely hydrogenated diene polymer
block. For example, polymer block A is a block copolymer
having the structure polystyrene-completely hydrogenated
,, .,:.
-11
polybutadiene-polystyrene with block molecular weights
oE 25,000 100,000-25,000. An alternative formulation is
a block copolymer oE the same structure and block identi~
ty but having block molecular weights of 10,000-50,000-
10,000.
Example 5
A block copolymer of general form polyethyl-
methyl styrene polybutadiene polyethyl methyl styrene
was prepared with different quantities of uncured butyl
rubber. The alpha-beta-alpha block copolymer had an
alpha methyl styrene content of approximately 35 per-
cent by weight and a molecular weight of about 60,000.
The nonterminal elastomer block may be polybutadiene, or
polybutadiene and butyl rubber. The resulting block
copolymer was then admixed with components A and B.
Example 6
Other specific aliphatic olefins, aromatic
olefins and/or mixtures thereof may be selected from
the following list and utilized according to the teach-
ings herein:
TPR thermoplastic rubber 1600, Uniroyal, Inc.
Naugatuk, Connecticut;
Combinations of isotatic polypropylene and
ethylene propylene rubber;
TPR thermoplastic rubber 1900, Uniroyal, Inc.,
Naugatuk, Connecticut;
As in an additional ingredient, from .25 to .5%
of a nucleating agent such as sodium benzoate or millad
3900 polyolefin clarifies both manufactured by Milliken
Corp., may be added to the above listed formulations to
improve clarity.
The foregoing description and drawings merely
explain and illlustrate the invention, and the invention
is not so limited thereto, except insofar as the appended
claims are limited to those skilled in the art who have
the disclosure before them and are able to make modifica-
tions and variations therein without departing from the
scope of the invention.
~D
SUPPLEMENTARY DISCLOSURE
..
In accordance with a Eurther aspec-t of this
invention, a clear, flexible, thermoplastic material is
provided, capable of ~eing processed into hollow shapes
by conventional thermoplastic processing methods and
subsequently autoclaved. The material comprises- (A)
from about 45 to 70~ by weigh~ of a polypropylene
polyolefîn, ineluding its copolymers, admixed with from;
(~) about 5 to 25 ~y weight of an ethylene loweralkyl
acrylate; ~C~ from about 10 to 4~% by weig~t of an
ethylene bu~ylene block copolymer having termunal
polystyrene units; and ~D~ from about a to 15% of a high
boiling point petroleum dist~llation byproduct or
representated by mineral oilO
The following examples fuxther illustrate t~is
aspect o~ the invention:
_ mple 7
Example 1 was repeated with a block copolymer
(Kraton~ G 27Q5] added to the rotational mixer in the
2a amount of 30~ by weight with 70~ by ~eight of a blend of
80% polypropylene and 20% EMA, to o~tain the same
successful results.
Example 8
Example 5 was repeated using the percentages
given in example 7.
Example 9
Example 4 was repeated using ~h2 same percentages
o elements A and B as for example 80 However, element
C comprises 18% by weight rather than 10% by weight as in
example 4, and an additional element D of mineral oil in
an amount of 12~ would be added to hoth formulationsO
The following examples 10 and 11 are set forth
for the purpose o~ illustrating the use of a styrene-
ethylene-butylene-styrene block copolymer without the use
of mineral oil. The particular block copolymer is Kraton~
1651 which is also manufactured by Shell Chemlcal Company.
~ 12 -
pc/ , (~,
.. .. .
E mple 10
ient % Weight
Polypropylene 50
Eth~3.ene methyl acr~late 10
Kraton~ 1651 40
Mineral Oil o
Exam~le 11
% Wei~t
Polypropylene 56
Ethylene methyl acrylate 14
Kraton~ 1651 30
Mineral Oil 0
The same processing conditions are employed in
Examples 10 and 11 as set forth in Example 1 to result in
a clear, flexible~ thermoplastic material capa~le of ~eing
blow m~lded into flexi~le containers for intravenou~
solutions.
pc/~
I
