Note: Descriptions are shown in the official language in which they were submitted.
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P-2468P1
BARRIER COATING
10BACKGROUND OF THE INVENTION
This application is a continuation-in-part of United States Serial
Number 07/9937275, filed on December 18, 1992.
151. Field of the Invention
-This invention relates to a barrier coating for providing an
effective barrier against gas and water permeability for containers,
especially plastic evacuated blood collection tubes.
2. Description of the Related Art
With the increased emphasis on the use of plastic medical
products, a special need exists for improving the barrier properties of
25 articles made of polymers.
Such medical products that would derive a considerable benefit
from improving their barrier properties include, but are not limited to,
collection tubes and particularly those used for blood collection.
Blood collection tubes require certain performance standards to
be acceptable for use in medical applications. Such performance
standards include the ability to m~int~in greater than about 90%
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original draw volume over a one year period, to be radiation
sterilizable and to be non interfering in tests and analysis.
Therefore, a need exists to improve the barrier properties of
5 articles made of polymers and in particular plastic evacuated blood
collection tubes wherein certain performance standards would be able
to be met and the article would be effective and 'is able in medical
applications.
SUMMARY OF THE INVENTION
The present invention is a plastic composite container coated
with a barrier coating comprising at least two barrier materials.
15 Desirably, the barrier coating comprises a first layer of an inorganic
material and a second layer of a polymer material.
The first layer of the barrier coating may preferably be an
aluminum oxide based composition, such as AlOx wherein x is from
20 0.3 to about 0.9; a silicon oxide based composition; or a diamond
based composition. Most preferably, the first layer is an al~ um
oxide based composition.
The second layer may preferably be vinylidene chloride-
25 acrylonitrile-methyl methacrylate-methyl acrylate-acrylic acid
copolymers, thermosetting epoxy coatings, palylene polymers, or
polyesters,. The barrier coating may be formed either on an interior
surface portion, on an exterior surface portion, or both of the container.
Preferably, the second layer is a parylene polymer. Parylene is the
30 generic name for members of a polymer series developed by Union
Carbide Corporation. The base member of the series, called parylene
N, is poly-p-xylylene, a linear, crystalline material:
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CH 2 {~> 2
Parylene C, a second member of the parylene series is produced
from the same monomer as parylene N and modified by the substitution
5 of a chlorine atom for one of the aromatic hydrogens:
CH 2 --< 5 CH 2
Parylene D, the third member of the parylene series is produced
10 from the same monomer as parylene N and modified by the substitution
of the chlorine atom for two of the aromatic hydrogens:
CH2 ~CH2
c1
.
Most preferably, the polymer layer is a vinylidene chloride-
methyl methacrylate-methacrylate acrylic acid polymer. This polymer
20 is available as DARAN(~) 8600-C (tr~-lem~rk of W.R. Grace and Co.)
sold by GRACE, Organic Chemicals Division, Lexington, Mass.
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Plastic tubes coated with the barrier coating are able to m~int~in
substantially far better vacuum retention and draw volume retention
than previous tubes comprised of polymer compositions and blends
5 thereof without a coating of barrier materials.
Printing may be placed on the barrier coating applied to the
container of interest. For example, a product identification, bar code,
brand name, company logo, lot number, expiration date and other data
10 and information may all be included on the barrier coating.
Moreover, a matte finish or a corona discharged surface may be
developed Oll the barrier coating so as to make the surface a~pro~liate
for writing additional information on the label. Furthermore, a pressure
15 sensitive adhesive label may be placed over the barrier coating so as to
accommodate various hospital over-labels, for example.
Optionally, the substrate may be pre-treated with a first plasma
coating of oxygen, hydrogen, air or water vapor, followed by the
20 depositillg of silicon oxide or aluminum oxide. Most preferably, the
first plasma coating is oxygen. It is believed that the pre-treatment
provides for improved adherence qualities between the coating of
silicon oxide or aluminum oxide and the article.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a typical blood collection tube
with a stopper.
FIG. 2 is a longit~l-lin~l sectional view of the tube of FIG. 1
taken along line 2-2.
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FIG. 3 is a longi~l~in~l sectional view of a tube-shaped
container, similar to the tube of FIG. 1 without a stopper, comprising a
barrier coating.
S FIG. 4 is a longitll~lin~l sectional view of a tube-shaped
container, similar to the tube of FIG. 1 with a stopper, comprising a
barrier coating.
DETAILED DESCRIPTION
Referring to the drawings in which like reference characters
refer to like parts throughout the several views thereof, FIGS. 1 and
2 show a typical blood collection tube 10, having a sidewall 11
extending 30 from an open end 16 to a closed end 18 and stopper 14
which includes a lower annular portion or skirt 15 which extends into
and presses against the inner surface 12 of the sidewall for mainlai~ g
stopper 14 in place.
FIG. 3 shows the preferred embodiment of the invention, a
plastic tube coated with at least two layers of barrier materials. The
preferred embodiment includes many components which are
substantially identical to the components of FIGS. 1 and 2.
Accordingly, similar components l~erforming similar functions will be
numbered identically to those components of FIGS. 1 and 2, except
that a suffix "a" will be used to identify those components in FIG. 3.
Referring now to FIG. 3, the IJref~lled embodiment of the
invention, collection tube assembly 20 comprises a plastic tube 10a,
having a sidewall 1 la extending from an open end 16a to a closed end
18a. A barrier coating 25 extends over a substantial portion of the
length of the tube which is upon the outer surface of the tube with the
exception of open end 16a. Barrier coating 25 comprises a first layer
26 of an inorganic material and a second layer 27 of a polymer
material.
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FIG. 4 illustrates an alternate embodiment of the invention,
wherein collection tube assembly 40 comprises stopper 48 in place for
closing open end 41 of tube 42. As can be seen, sidewall 43 extends
5 from open end 41 to closed end 44 and stopper 48 includes an
annular upper portion 50 which extends over the top edge of tube 42.
Stopper 48 includes a lower annular portion or skirt 49 which extends
into and presses against the inside inner surface 46 of sidewall 43 for
maintaining stopper 48 in place and a well 52.
Covering a substantial portion of the length of the tube is a
barrier coating 45. Barrier coating 45 covers substantially most of the
tube with the exception of open end 41 thereof. Barrier coating 45
comprises a first layer 54 of an inorganic material and a second layer
15 56 of a polymer material. FIG. 4 differs from the embodiment in FIG.
3 in that the tube may be evacuated with the simultaneous placement of
stopper 48 therein after the application of barrier coating 45 over the
tube. Alternatively, the barrier coating may be applied to the tube
before it has been evacuated.
An alternate embodiment of the invention also includes a barrier
coating incorporating both the upper portion of the stopper, as well as
the entire container tube. Such an embodiment may be utilized, for
example, for sealing the container with the stopper in place. Once a
25 sample has been placed in the tube, the sample cannot be tampered
with by removal of the stopper. Additionally, serrations could be
included at the tube, stopper interface. The serrations may be
registered so that it can be determined if the sealed container has been
tampered with.
It will be understood by practitioners-in-the-art that such tubes
may also contain reagents in the form of additives or coatings on the
inner wall of the tube.
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The barrier coating forms a substantially clear or translucent
barrier. Therefore, the contents of a plastic tube layered with a barrier
coating comprising at least two layers of barrier materials are
subst~nti~lly visible to the observer at the same time identifying
5 information may be displayed over the barrier coating after it is applied
to the plastic tube.
The inorganic material of the barrier coating may be formed on a
substrate as a first layer by radio frequency discharge, direct or dual
10 ion beam deposition, sputtering or plasma chemical vapor deposition,
as described in U.S. Patent Nos. 4,698,256, 4,809,876, 4,992,298 and
5,055,318, the disclosures of which are herein incorporated by
reference.
The second layer of the barrier coating, a polymer material, may
be a parylene polymer applied to the first layer by a process similar to
vacuum met~lli7.ing, as described in U.S. Patent Nos. 3,342,754 and
3,300,332, the disclosures of which are herein incorporated by
reference. Alternatively, the second layer may be vinylidene chloride-
20 acrylonitrile-methyl methacrylate-methyl acrylate-acid acrylic polymer,
applied to the first layer by dip-coating, roll-coating or spraying an
aqueous emulsion of the polymer, followed by air drying of the coating,
as described in U.S Patent ~os. 5,093,194 and 4,497,859, the
disclosure of which are herein incorporated by reference.
The barrier coating of the present invention is ~lerelably a first
layer material comprising aluminum oxide, and a second layer of
vinylidene chloride-acrylonitrile-methyl methacrylate-methyl acrylate-
acrylic acid polymer applied to the first layer. A plastic blood
30 collection tube coated with the barrier coating will not interfere
with testing and analysis tllat is typically performed on blood in a tube.
Such tests include but are not limited to, routine chemical analysis,
biological inertness, hematology, blood chemistry, blood typing,
toxicology analysis or therapeutic drug monitoring and other clinical
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P-2468P1
tests involving body fluids. Furthermore, a plastic blood collection
tube coated with the barrier coating is capable of being subjected to
automated machinery such as centrifuges and may be exposed to
certain levels of radiation in the sterilization process with subst~nh~lly
5 no change in optical or mechanical and functional properties.
A plastic blood collection tube coated with the barrier coating is
able to maintain 90% original draw volume over a period of one year.
Draw volume retention depends on the existence of a partial vacuum,
10 or reduced pressure, inside the tube. The draw volume changes in
direct proportion to the change in vacuum (reduced pressure).
Therefore, draw volume retention is dependent on good vacuum
retention. A plastic tube coated with a barrier coating substantially
prevents gas penneation through the tube material so as to m~int~in
15 and enhance the vacuum retention and draw volume retention of the
tube.
If the barrier coating is also coated or applied on the inner
surface of the plastic blood collection tube, the barrier coating may be
20 hemorepellent and/or have characteristics of a clot activator if the first
layer of the barrier coating is a diamond composition.
It will be understood that it nlakes no di~erence whether the
plastic composite container is evacuated or not evacuated in
25 accordance with this invention. The presence of a barrier coating on
the outer surface of the container has the effect of maint~ining the
general integrity of the container holding a sample so that it may be
properly disposed of without any cont~rnin~tion to the user. Notable is
the clarity of the barrier coating as coated or applied on the container
30 and its abrasion and scratch resistance.
The barrier coating used in accordance with this disclosure, may
contain conventional additives and ingredients which do not adversely
affect the properties of articles made therefrom.
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EXAMPLE 1
METHOD FOR COATING PLASTIC SUBSTRATES
TUBES WITH MULTI-LAYER BARRIER COATING
A silicone oxide coating was applied to polypropylene tubes and
films (substrates) as follows:
The substrate was cleaned with a lllixlule comprising equal parts
of a micro detergent and de-ionized (DI) water solution. The substrate
was rinsed thoroughly in DI water and allowed to air dry. The cleaned
substrate was then stored in a vacuum oven at room temperature until it
was to be coated.
The cleaned substrate was then attached to a holder which fits
midway between the electrodes in the glass vacuum chamber. The
chamber was closed and a mechanical pump was used to achieve a
base pressure of 5 mTorr.
The electrode configuration is internally capacitively coupled
with permanent magnets on the backside of the titanium electrodes.
The special configuration provides the ability to confine the glow
between the electrodes because of the increase in collision probability
between electrons and reacting gas molecules. The net result of
applying a magnetic field is similar to increasing the power applied to
the electro, des, but without the disadvantages of higher bombardment
energies and increased substrate heating. The use of magnetron
discharge allows operation in the low pressure region and a substantial
increase in polymer deposition rate.
The monomer which consists of a mixture of trimethylsilane
(TMS) and oxygen was introduced through stainless steel tubing near
the electrodes. The gases were mixed in the monomer inlet line before
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introduction into the chamber. Flow rates were manually controlled by
stainless steel metering valves. A power supply operating at an audio
frequency of 40 kHz was used to supply power to the electrodes. The
system parameters used for thin film deposition of plasma polymerized
5 TMS/O2 on the polymer substrate were as follows:
Surface Pretreatment: Base Pressure = 5m Torr
Oxygen Flow = 10 sccm
System Pressure = 140m Torr
Power = 50 watts
Time = 2 minutes
Oxide Deposition: TMS Flow = 0.75 - 1.0 sccm
Oxygen Flow = 2.5 = 3.0 sccm
System Pressure = 90 - 100 mTorr
Power = 30 watts
Deposition Time = 5 minutes
After the thin film was deposited, the reactor was allowed to
20 cool. The reactor was then opened, and the substrate with a coating of
silicon oxide was removed. The coated substrate was then subjected to
a filrther coating of vinylidene chloride-acrylonitrile-methyl
methacrylate-methyl aclylate-acrylic acid polymer (PVDC) as
described in U.S. Patent Nos. 5,093,194 and 4,497,859.
EXAMPLE 2
COMPARISON OF SUBSTRATES WITH AND WITHOUT
MULTI-LAYER BARRIER COATINGS
All of the substrates prepared in accordance with Example 1
above were evaluated for oxygen permeance (OTR) as follows:
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Film or plaque samples were tested for oxygen permenace
(OTR) using a MO CON Ox-TRAN 2/20 (sold by Modern Controls,
IllC.). A single side of the film sample was exposed to 1 atm of 100%
oxygen atmosphere. Oxygen permeating through the sample film was
5 entrained in a nitrogen carrier gas stream on the opposite side of the
film, and detected by a coulmetric sensor. An electrical signal was
produced in proportion to the amount of oxygen permeating through
the sample. Samples were tested at 30~C and 0% relative humidity
(R.H.). Samples were conditioned for 1 to 20 hours prior to
10 determining oxygen permenace. The results are reported in Table 1 in
units of cc/m2-atm-day.
Tube samples were tested for oxygen permeance (OTR) using a
MOCON Ox-TRAN 1,000 (sold by Modern Controls, Inc.). A
15 package adapter was used for mounting the tubes in a manner that
allowed the outside of the tube to be immersed in a 100% ~2
atmosphere while the inside of tube is flushed with a nitrogen carrier
gas. The tubes were then tested at 20~C and 50% R.H. The tubes
were allowed to equilibrate for 2-14 days before a steady state
20 permeability is determined. The results are reported in Table 1 in units
of cc/m2-atm-day.
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TABLE 1
Sample ~2 Plasma FIRST SECOND Oxygen Transmission Rate
Pretreatment Coating Coating(cc/m2-atm-day~
(25 C)
PP film, control no SiOx no 46-59
PPfilm yes SiOX PVDC <0 1
PP film no AIOx PVDC 0.32
PP film yes AIOx PVDC 0.028
