HK1002964A

HK1002964A - Apparatus and method for plasma processing

Info

Publication number: HK1002964A
Application number: HK98102063.1A
Authority: HK
Inventors: 戴维‧A‧马丁
Original assignee: 贝克顿迪金森公司
Priority date: 1996-01-30
Filing date: 1998-03-12
Publication date: 1998-09-30

Description

Apparatus and method for plasma processing

The present invention relates to apparatus and methods for facilitating plasma processing, particularly chemical plasma enhanced vapor deposition, plasma polymerization or plasma processing of barrier materials on the interior surfaces of vessels to provide effective barriers against gas and/or water permeation.

Plastic containers often do not have the chemical and physical characteristics for proper storage and/or handling of their intended contents, so the plastic surface can be chemically modified or coated with a film that eliminates these defects, thereby increasing the value of the original plastic container. Examples of containers include barrier layers having permeability to gases and/or water vapor and surface reactivity with the contents.

Of most particular interest are plastic medical products such as evacuated blood collection tubes, syringes or sample collection containers.

Vacuum plastic tubes are permeable to gases and water vapor in the air and substantially lose vacuum over time. The consequence of the loss of vacuum is a reduction in the ratio of draw volume to blood additive. Thus, there is a need to improve the barrier properties of plastic pipes, wherein some performance criteria should be met.

Methods for improving barrier properties of plastic containers include deposition of metal and metal oxide films from vacuum deposition sources such as plasma chemical vapor deposition, plasma polymerization, plasma sputtering, and the like. A common method of applying plasma deposited coatings or modifications to plastic containers is to place one or more containers in a vacuum chamber containing a low pressure process gas and an electrode for energizing the plasma. In most cases, these methods apply a coating to the outer surface of the container.

Accordingly, there is a need for improved methods and apparatus for placing coatings on the interior of container surfaces.

The present invention is an apparatus and method for applying a barrier film coating or treatment to the interior wall surface of a plastic container by plasma treatment. Such coatings and treatments can significantly improve the barrier properties of the container and the surface reactivity of the container.

Desirably, the barrier film coating contains a silicon oxide component, such as SiO_xWherein the number ratio of oxygen atoms to silicon atoms, x, is from about 15 to about 2.0.

A preferred apparatus of the present invention comprises means for delivering a reactive gas to the interior volume of a plastic container under vacuum conditions and means for applying and imparting energy to the interior of the container so as to energize or induce a plasma to the reactive gas so as to provide a barrier film on the interior wall surface of the plastic container.

Preferably, the apparatus for plasma treating the interior wall surface of the vessel comprises a multi-tube system connected to and/or exposed to the interior surface of the vessel. The multi-tube system preferably includes means for delivering reactant gases to the vessel and means for creating and maintaining a vacuum in the vessel during processing. The apparatus of the invention further comprises means for imparting energy inside the vessel so as to be able to generate a plasma.

Preferably, the means for delivering reactant gas to the vessel comprises a source of monomer, a source of oxidant and optionally a source of diluent gas.

Preferably, the means for creating and maintaining a vacuum in the vessel during the process is a vacuum pump.

Preferably, the means for generating a plasma comprises an electrode and an energy source.

Accordingly, a method for coating a barrier film on the inner wall surface of a container comprises the steps of:

(a) placing the open end of the container onto a vacuum multi-tube system;

(b) positioning the exterior surface of the container in position with a means for energizing the interior of the container;

(c) evacuating the container;

(d) adding a reaction gas to the vessel;

(e) energizing inside the container; and

(f) a plasma is generated inside the container and thus a barrier film coating is applied to the inner wall surface of the container.

Optionally, the process steps may be repeated to ensure that the barrier film coating is uniformly applied throughout the interior of the container or a second layer of barrier film coating is applied.

Optionally, the interior wall surface of the container may be chemically modified or pre-coated with a non-barrier coating. The non-barrier coating can provide a container with an inner wall surface that is significantly reinforced, stable, and smooth so that the adhesion of the barrier coating to the inner wall surface can be improved.

An alternative of the invention is to apply the top layer over a previously applied barrier film coating. The top layer can substantially protect the barrier film coating and impart a surface chemistry that enhances the properties of the final product, such as inhibiting or enhancing surface reactions with the intended contents of the container in use.

Preferably, the monomer source is an organosilicon component such as Hexamethyldisiloxane (HMDSO), Tetraethoxysilane (TEOS) or Tetramethylsilane (TMS).

Preferably, the source of oxidant is air, oxygen or nitrous oxide.

Preferably, the diluent gas source is an inert gas such as helium, argon or an inert gas such as nitrogen.

Preferably, the electrodes are inductively or capacitively coupled metal electrodes in the form of windings, a pointed rod or a flat or curved plate. Preferably, the electrodes are energized by an energy source such as low frequency Alternating Current (AC), Radio Frequency (RF) or microwave frequency potentials, either continuously or in pulses.

Preferably, the method of applying the barrier coating to the interior wall surface of the container comprises the steps of:

(a) placing the open end of the vessel in position in the vacuum manifold system;

(b) placing the outer surface of the container in position with an electrode connected to an energy source;

(c) evacuating the vessel with a vacuum pump to maintain the pressure inside the vessel at about 300 mtorr;

(d) controlling the flow of the organosilicon component and the oxidizer component and optional inert gas component through the multi-tube system and into the vessel;

(e) energizing the electrodes to impart energy to the composition inside the container;

(f) forming a glow discharge plasma inside the vessel; and

(g) a barrier film coating is deposited on the interior wall surface of the container.

Preferably, the steps of the method are repeated, wherein the electrodes of step (b) are replaced in position on the outer surface of the container.

Alternatively, the steps of the method may be repeated wherein the electrodes of step (b) are turned off and on and/or the component flow of step (d) is turned off and on to pulse the plasma energy or the component flow or both to enhance the barrier properties.

Furthermore, alternative method steps are as follows:

(h) de-energizing the electrodes; and

(i) the electrodes are energized to impart energy.

Further alternatives are as follows:

(h) stopping the flow of ingredients in step (d); and

(i) again controlling the flow of the ingredients as in step (d).

Another alternative is as follows:

(h) stopping the flow of ingredients in step (d);

(i) de-energizing the electrodes in step (e); and

(j) repeating steps (d) - (g).

The method of disposing a coating on the interior wall surface of a container and using the container as a vacuum processing chamber of the present invention has a number of distinct features and advantages over previous methods of applying a coating on the exterior surface of a container in a vacuum chamber.

A notable feature of the present invention is that the vessel can function as its separate vacuum chamber in which plasma-induced or enhanced reactions occur, resulting in modification of, or deposition on, the interior wall surfaces of the vessel. The apparatus and method of the present invention do not require a vacuum chamber. Vacuum chambers require significant process real estate and control when used in most deposition processes.

The invention can improve the production efficiency. The present invention allows for on-line operation on each individual vessel, as opposed to the common batch-wise operation of many vessels. Large batch operating chambers require longer depressurization times due to increased chamber volume and chamber venting. Thus, in the case of the present invention, the loading and unloading of containers in the batch chamber can be eliminated.

An important feature of the present invention is that the barrier film coating on the interior wall surface of the container can be substantially protected from physical damage. When the barrier film coating is on the outside of the container, as is often the case, it is subject to wear from handling during manufacture, shipping, or from end use. Thus, when the barrier film coating is on the inner wall surface of the container, the efficacy of the container pot life can be improved since damage to the barrier film coating is significantly reduced.

The present invention is further characterized in that the barrier film coating on the inner wall surface is of significantly higher quality than the barrier film coating on the outer wall of the container. This is because the inner wall surface of the container is not as prone to contact with contaminants such as oil, grease and dust during production as the container exterior. These contaminants on the container wall can cause coating non-uniformity, defects, and poor adhesion. The interior of the vessel need not be cleaned of accumulated coatings or particles because each vessel to be coated is a newly treated "chamber". In addition, since the means for providing energy to the interior of the container is external, it is not subject to coating agglomeration which could alter its electrical properties and degrade the process.

It is a further feature of the present invention that the means for providing energy to the interior of the container can be altered, moved and/or rotated at various locations and locations on the exterior of the container to substantially ensure uniformity of the barrier film coating. Thus, the plasma process does not result in "shielding" as would a plasma treatment on the outer wall of the vessel.

Other disadvantages of batch systems, in which treatment is performed on the outer wall of the vessel, include "fixturing" of the vessel above the electrodes and variations in vessel dimensions, such as "bowing". These situations are not a problem in the present invention. Furthermore, the lack of large batch-wise operating units results in a large loss in throughput, which is of secondary importance if on-line units are used with many pipes (because each pipe is less expensive). Due to the simplicity of the in-line process, alternative batch processes may be preferred to improve their roughness and repairability. It is believed that the vessel according to the invention can be operated in-line without stopping its travel along the pipeline.

A further advantage of the invention is that the energy supply means inside the container is outside the container, so that it is easy and inexpensive to replace such means. By thus easily replacing the device such as the electrode, the direction of the reaction gas is changed so as to adapt the production line to meet the specific requirements. Thus allowing a single line to handle containers of different configurations with only minor changes in the line.

Most preferably, the container of the present invention is a blood collection device. Such blood collection devices are either evacuated or non-evacuated blood collection tubes. Blood collection tubes are required to be made from polyethylene terephthalate, polypropylene, polyethylene naphthalate or copolymers.

Plastic tubes having a barrier film coating on the inner wall surface maintain much better vacuum, draw volume and thermo-mechanical integrity than plastic tubes having a barrier film coating on the outer wall surface of the tube, which are comprised of a polymer composition and mixtures thereof. In addition, the tubes are much more impact resistant than glass tubes.

Most notable are the transparency of the barrier film coating and its durability to substantial impact and abrasion resistance.

In addition, plastic blood collection tubes coated with a barrier film layer can withstand automated machinery such as centrifuges and may be exposed to some level of radiation during sterilization.

Drawings

FIG. 1 is a perspective view of a representative stoppered blood collection tube.

Figure 2 is a longitudinal cross-sectional view of the tube of figure 1 taken along line 2-2.

FIG. 3 is a longitudinal cross-sectional view of a tube-type container similar to the tube of FIG. 1 but without the stopper, containing a barrier coating.

FIG. 4 is a schematic view showing the plasma generating apparatus of the present invention.

Fig. 5 is a schematic diagram illustrating a tube connected to the apparatus of fig. 4 and to a winding electrode.

The invention may be embodied in other specific forms and is not limited to any specific embodiment described in detail by way of illustration. It will be apparent to those skilled in the art that various modifications can be made without departing from the scope and spirit of the invention. The scope of the invention is to be determined by the appended claims and their equivalents.

Referring to the drawings, wherein like reference numbers refer to like parts throughout the several views, FIGS. 1 and 2 illustrate a representative blood collection tube 10 having a sidewall 11 extending from an open end 16 to a closed end 18 and a stopper 14 including an underlying annular portion or rim 15 that extends into and presses against an inner surface 12 of the sidewall to hold the stopper 14 in place.

FIG. 2 schematically illustrates three mechanisms for altering the vacuum level in a blood collection tube: (A) gas permeation through the plug material; (B) gas leaks through the tube (C) at the plug tube contact surface. Therefore, when there is substantially no gas permeation and no leakage, a good vacuum is maintained and a good blood volume is maintained.

Figure 3 illustrates a preferred embodiment of the invention where the plastic tube is coated with at least one layer of barrier material. The preferred embodiment includes many of the same components as those of fig. 1 and 2. Accordingly, like components performing like functions are numbered identically to those components of FIGS. 1 and 2, except that the subscript "a" is used to identify those components in FIG. 3.

Referring now to FIG. 3, in a preferred embodiment of the present invention, collection tube assembly 20 comprises a plastic tube 10a having a sidewall 11a extending from an open end 16a to a closed end 18 a. The barrier coating 25 extends over a major portion of the interior surface of the tube except for the open end 16 a.

The barrier coatings of the present invention are deposited from a plasma generated inside the tube from one or more constituents of a particular reactive gas stream. Desirably, the reactive gas includes a unit gas component and an oxidant gas component. The tubes are positioned with the vacuum manifold system to allow controlled flow of the reactive gas species into the interior of the tubes. An external energy source to the tube energizes the gas stream to deposit a barrier coating on the inner wall of the tube.

The deposition process of the present invention is carried out at a pressure within the manifold of from about 70 millitorr (mTorr) to about 2000 mTorr during deposition, and the preferred pressure within the tube during deposition of the barrier coating is from about 70 mTorr to about 2000 mTorr.

The substrate is at about room temperature of about 25 c during the deposition process. That is, the substrate is not particularly heated during the deposition process.

Referring to fig. 4, the apparatus of the present invention comprises a vacuum manifold system 22. The vacuum manifold system comprises at least five connecting tubes 24, 26, 28, 30 and 32 and a connecting port 34, desirably a rubber gasket.

Connecting lines 24, 26, 28, 30 and 32 lead to isolation gate valves 42, 44, 46, 48 and 50, respectively. Valves 42, 44, 46, 48 and 50 lead to a monomer gas source 52, an oxidant gas source 54, a vacuum pump 56, an exhaust filter 58 and a dilution gas source 60, respectively. The apparatus of the present invention further includes means for generating energy, including an external electrode system 62 and an energy source 64. The energy source preferably includes a regulator 66, an amplifier 68 and an oscillator 70.

After the tube is manufactured by any suitable plastic tube forming process, such as injection molding, extrusion with end caps, blow molding, injection blow molding, etc., the open end of the tube is first connected to a vacuum manifold system at the junction and all valves are closed. Valve 46 is then opened and the vacuum pump is again actuated to reduce the pressure in the tube until the vacuum ranges from about 0.001 mtorr to about 100 mtorr.

The reactive gas components necessary for forming plasma inside the tube are introduced into the tube again through the multi-tube system. The valve 42 is first opened to allow the monomer gas composition to flow into the manifold system at a pressure of about 125 millitorr, a flow rate of about 1.0sccm, and a room temperature of about 74F. Valve 44 is then opened to allow the oxidizer gas component to flow into the manifold system at a pressure of about 175 millitorr, a flow rate of about 22sccm, and a room temperature of about 74F.

The monomer gas component and the oxidant gas component are preferably mixed with the inert gas component in a multi-tube system before flowing into the tubes. The amounts of these gases so mixed are controlled by a flow rate controller to adjustably control the flow rate ratio of the reactant gas flow components. Mixing of the reactive gas components within the tube is accomplished prior to energizing the electrical system.

Most preferably, the monomer gas component is preferably HMDSO and the oxidant gas component is preferably oxygen to form and deposit silicon oxide (SiO) on the inner wall surface of the tube_x) The barrier coating of (1).

The barrier coating deposited on the inner surface of the tube is brought to a predetermined thickness. The coating thickness is from about 500A to about 5000A. Preferably, the oxide coating has a thickness of about 1000A to about 3000A.

Optionally, a common control system, including a computer control, is interfaced with components of the system to receive status information from the components and to output control commands to them.

Suitable pressures for the reaction gas mixture are between about 70 mtorr and about 2000 mtorr, preferably between about 150 mtorr and 600 mtorr and most preferably about 300 mtorr.

Desirably, an organosilicon such as HMDSO is used as the monomer gas component at a flow rate of about 0.1 to 50sccm, preferably about 0.5 to about 15sccm and most preferably about 1.0sccm at 25 ℃ and about 80 to about 190 millitorr.

Desirably, air is used as the oxidant gas component at a flow rate of about 0.1 to about 50sccm, preferably about 15 to about 35sccm, and most preferably about 22sccm, at 25 ℃ and about 110 to about 200 millitorr.

Reactive gases, e.g. oxygen, F₂、Cl₂、SO₂Or N₂O may be used for pretreatment or post-treatment to react with the barrier coating precursor.

Preferably, the source of oxidant is air, oxygen or nitrous oxide.

Preferably, the diluent gas source is an inert gas such as helium, argon or a non-reactive gas such as nitrogen.

Examples of suitable organosilicon compounds are those that are liquid or gaseous at about room temperature and have a boiling point of about 0 ℃ to about 200 ℃, including tetramethyltin, tetraethyltin, tetraisopropyltin, tetraallyltin, dimethylsilane, trimethylsilane, diethylsilane, propylsilane, phenylsilane, hexamethyldisilane, 1, 2, 2-tetramethyldisilane, bis (trimethylsilane) methane, bis (dimethylsilyl) methane, hexa-methyldisiloxane, vinyltrimethoxysilane, vinyltriethoxysilane, ethylmethoxysilane, ethyltrimethoxysilane, divinyltetramethyldisiloxane, hexamethyldisilazane, divinylhexamethyltrisiloxane, trivinyl-pentamethyltrioxazane tetraethoxysilane and tetramethoxysilane.

Among the preferred silicones are 1, 1, 3, 3-tetramethyldisiloxane, trimethylsilane, hexamethyldisiloxane, vinyltrimethylsilane, methyltrimethoxysilane, vinyltrimethoxysilane and hexamethyldisilazane. The boiling points of these preferred organosilicon compounds are 71 deg.C, 55.5 deg.C, 102 deg.C, 123 deg.C and 127 deg.C, respectively.

The optional diluent gas in the gas stream is helium, argon or nitrogen. The non-reactive gas may be used for dilution of the reactive gas.

The specific gas or mixture may be a barrier coating precursor, like for SiO_xSiloxane or silane of the barrier layer, methane, hexane, etc., suitable for hydrocarbon polymerization or diamond-like coating.

In order to bring the reaction gases to a favorable reaction, energy is supplied to the interior of the tube to generate a plasma, which is a metal electrode in the form of a coil, a pin, a flat or curved plate, a ring or a cylinder, which is coupled inductively or capacitively via an electrode on the outside of the tube. Plate 62 is shown in fig. 4 and winding 74 is shown in fig. 5.

Preferably, the electrodes are energized with an energy source, which may be a low frequency Alternating Current (AC), Radio Frequency (RF), or microwave frequency potential, provided in continuous or pulsed fashion.

Most preferably, the electrodes are energized with an ideal RF power stage of about 5 watts to about 150 watts, preferably about 15 watts to about 40 watts and most preferably about 20 watts.

The result is an electrical breakdown within the tube and ionization of the process gas, i.e., the generation of a plasma within each individual tube. The plasma is energized for from 1 second to 20 minutes, preferably 5 seconds to 2 minutes. Condensation and chemical reactions of the process gases can produce the desired coating or modify the contained tube walls. The substrate may be any material suitable for vacuum. Such as plastic.

A variation of the method of the invention is to coat the interior of the container with a liquid layer, which may be by any of several methods, such as dip coating, self-spin coating, spray coating, or solvent coating, and then cross-linking or curing the liquid using a suitable plasma generated by the method of the invention, such that the liquid becomes a solid, semi-solid, or gel coating.

Various optical methods known in the art can be used to determine the thickness of the deposited film within the deposition chamber or to measure the film thickness after the article is removed from the deposition chamber.

Various substrates can be coated with barrier layer compositions using the method of the present invention. Such substrates include, but are not limited to, packaging materials, containers, bottles, canisters, tubes, and medical devices.

A number of methods other than plasma deposition may be used to deposit the barrier layer composition including, but not limited to, radio frequency discharge, direct or dual ion beam deposition, sputtering or evaporation.

Many other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of the invention.

The following examples are not intended to limit any particular embodiment of the invention, but are merely exemplary.

Example 1

A polypropylene (PP) tube was connected to a vacuum manifold system with an outer parallel plate electrode surrounding the outside of the tube. The interior of the tube is first evacuated to a vacuum of about 60 mtorr. Air at about 400 millitorr was then introduced into the tube via a multi-tube system and the electrodes were powered by a 38MHz oscillator for 30 watts of power for about 30 seconds to provide a surface activation treatment. While the plasma was energized, monomer gas of hexamethyldisilane vapor was fed through the tubes until the total pressure of the gas mixture was about 725 millitorr. Plasma deposition was maintained for about 1 minute followed by air for 30 seconds.

In SiO_xAfter deposition on the inner wall surface of the tube, the tube is separated from the multiple tubes. The permeation efficiency results for the tubes are shown in table 1.

Example 2

The PP tubes were connected to a vacuum manifold system and external parallel plate electrodes surrounding the outside of the tubes. The tube was first evacuated to a vacuum of about 60 mtorr. Air was then introduced into the tube at a pressure of about 600 millitorr. The hexamethyldisiloxane vapor was then introduced into the tube until the total pressure of the gas mixture in the tube was about 1.0 torr. The electrodes were energized at 38MHz and 22 watts for about 2 minutes, resulting in SiO generation in the tube_xThe plasma of (2).

In SiO_xAfter deposition on the inner wall of the tube, the tube is disconnected from the manifold. The permeation efficiency results for the tubes are shown in table 1.

Example 3

Polyethylene terephthalate (PET) tubes were connected to a vacuum manifold system and to external parallel plate electrodes surrounding the outside of the tubes. The tube was first evacuated to a vacuum of about 65 millitorr. Air was then introduced into the tube at a pressure of about 600 millitorr. Hexamethyldisiloxane vapor was then introduced into the tube until the total pressure of the gas mixture in the tube was about 1.0 torr. Energizing the electrode at 38MHz and 22 watts for about 2 minutes resulted in SiO_xA plasma is generated within the tube.

In SiO_xAfter deposition on the inner wall surface of the tube, the tube was separated from the multitubular tube, and the results of the permeability of the tube are shown in table 1.

Example 4

The PET tube was connected to a vacuum manifold system and to an external flat electrode with an end bend around the closed end of the tube. The tube was first evacuated to a vacuum of about 65 millitorr. Oxygen was then introduced into the tube at a pressure of about 300 millitorr. Hexaethyldisiloxane vapor was introduced until the total pressure in the tube was about 400 millitorr. Plasma was generated in the tube by energizing the electrodes at 38.5MHz and 22 watts for about 5 minutes.

SiO_xAfter deposition on the inner wall surface of the tube, the tube is separated from the multitubular tube. The permeability performance results of the tubes are shown in table 1.

Example 5

The tubes made of PP were connected to a vacuum manifold system and to an external flat electrode with an end bend around the closed end of the tube. The tube was first evacuated to a vacuum of about 65 millitorr. Oxygen was then introduced into the tube at a pressure of about 400 millitorr. Hexamethyldisiloxane is introduced into the tube until the total pressure of the gas mixture in the tube is about 750 mtorr. The plasma was formed in the tube after the electrodes were energized at 38.5MHz and 22 watts to generate plasma in the tube for about 5 minutes.

SiO_xAfter deposition on the inner wall surface of the tube, the tube is separated from the multiple tubes. The permeability performance results of the tubes are shown in table 1.

Example 6

The tubes made of PP were connected to a vacuum manifold system and to an external flat electrode with an end bend around the closed end of the tube. The tube was first evacuated to a vacuum of about 65 millitorr. Oxygen was then admitted to the tube at a pressure of about 400 millitorr. Hexamethyldisiloxane was introduced into the tube until the total pressure in the tube was 700 mtorr. Plasma was formed in the tube by energizing the electrode at 38.5MHz and 22 watts for about 2.5 minutes.

The tube was rotated about its axis while still under vacuum by about 90 degrees and the electrode was again energized at 38.5MHz and 22 watts for 2.5 minutes.

Example 7

A tube made of PP was connected to a vacuum manifold system and to a wound electrode around the closed end of the tube and a charged electrode around the open end of the tube. The tube was first evacuated. Air is now introduced into the tube at a pressure of about 200 millitorr. However, when the electrodes were energized at 11.7MHz and 62 watts for about 30 seconds, the air plasma was oxidized inside the tube resulting in an increase in the surface energy for increased liquid diffusion.

The tube was then disconnected from the vacuum manifold and the interior of the tube was coated with a 1% solution of tripropylene diacrylate in trichlorotrifluoroethane. The solvent is then allowed to evaporate leaving a diacrylate coating in the tube. The tube was then reconnected to the vacuum manifold and the electrodes. The diacrylate was cross-linked in place by 2 minutes of air plasma treatment at about 150 millitorr within the tube under the same energy, frequency, and electrode conditions as described above.

Air was then introduced into the tube at a pressure of about 150 millitorr.

Hexaethyldisiloxane vapor was introduced until the total pressure in the tube was about 250 millitorr. The plasma was formed in the tube by energizing the electrode at 11.7MHz and 62 watts for about 3 minutes.

The plasma of the hexamethyldisiloxane/air mixture is again tripled up in the tube so that the SiO_xThe barrier layer is deposited in four successive layers.

Followed by a protective top layer deposited on the SiO near the HMDSO polymerized with plasma_xAnd a barrier layer. The hexamethyldisiloxane is then introduced into the tube at about 300 millitorr and the electrodes are energized at 11.7MHz and 62 watts for about 60 seconds.

Example 8

A Polystyrene (PS) tube was connected to a vacuum manifold and to an outer wound electrode surrounding the closed end of the tube. The tube was first evacuated to a vacuum of about 30 mtorr. 22sccm of air was then introduced into the tube through the manifold system at a pressure of about 250 millitorr. Then, 1.0sccm of HMDS vapor was introduced into the tube through the multi-tube system under a pressure of 50 mTorr so that the total pressure of the gas mixture in the tube reached 300 mTorr. The electrodes were energized at 11MHz and 20 watts for about 5 minutes so that a plasma was generated within the tube.

SiO_xAfter deposition on the inner wall surface of the tube, the tube is disconnected from the multi-tube. The permeability performance results of the tubes are shown in table 1.

TABLE 1

Examples oxygen permeability

cc/m²Atm/day

PP tubes, uncoated controls

(example 1) 55.9

PP pipe (example 1) 26.1

PP tube, control (example 2) 50.0

PP pipe (example 2) 33.7

PET tubes (example 3) 1.75

PET tubes, control (example 3) 2.33

PET tube (example 4) 1.47

PET tubes, control (example 4) 2.33

PP pipe, W/non-rotating (example 5) 32.4

PP tubes, control W/no rotation (example 5) 57.1

PP tube, W/spin (example 6) 25.8

PP tubes, control W/spin (example 6) 57.1

PP tube, control (example 7) 77.1 < PP tube, (example 7) 4.42PS tube, uncoated control 145 (example 8) PS tube, (example 8) 77.3

Claims

1. A method of applying a barrier film coating to an interior wall surface of a plastic substrate, the method comprising:

(a) positioning a plastic article having an open end, a closed end, an outer portion, an inner portion, and outer wall and inner wall surface such that said open end is connected to a vacuum manifold system having a monomer supply, an oxidizer supply, and a vacuum supply;

(b) placing the outer wall surface of the plastic article in position with the electrode assembly;

(c) evacuating the interior of the article;

(d) delivering a monomer gas and an oxidant gas into the interior of the article;

(e) delivering an alternating current to the electrode; and

(f) the gas is ionized to form a plasma to apply a barrier film coating to the interior wall surface of the container.

2. The method of claim 1, wherein the substrate is a three-dimensional object.

3. The method of claim 2, wherein the substrate is a blood collection tube.

4. The method of claim 1, wherein the monomer gas is air, oxygen, or nitrous oxide.

5. The method of claim 1, wherein the oxidant gas is air, oxygen, or nitrous oxide (nitrous oxyden).

6. The method of claim 1, wherein the monomer gas is delivered to the article at about 0.5 seem to about 15 seem.

7. The method of claim 1, wherein an oxidant gas of about 15 seem to about 35 seem is delivered to the article.

8. The method of claim 1, wherein the article is evacuated to a pressure of from about 0.001 mtorr to about 100 mtorr.

9. The method of claim 1, wherein the monomer gas is delivered to the article at about 80 mtorr to about 190 mtorr.

10. The method of claim 1, wherein the oxidant gas is delivered to the article at about 110 mtorr to about 200 mtorr.

11. The method of claim 1, wherein step (d) further comprises a diluent gas.

12. The method of claim 11, wherein the diluent gas is an inert gas.

13. The method of claim 12, wherein the inert gas is helium, argon, or a non-reactive gas.

14. The method of claim 12, wherein the non-reactive gas is nitrogen.

15. The method of claim 1, wherein the alternating current is a low frequency alternating current, radio frequency or microwave frequency.

16. A multi-tube system for applying plasma to an interior wall of a plastic article, comprising:

(a) means for attaching and/or exposing the inner wall of the plastic article to the multi-tube system;

(b) means for delivering monomer into the vessel;

(c) means for delivering an oxidant into the vessel;

(d) means for creating and maintaining a vacuum in said article; and

(e) means for inputting energy inside said container.

17. The apparatus of claim 16, wherein said means for delivering monomer to said container is a valve.

18. The apparatus of claim 16, wherein the means for delivering the oxidant to the vessel is a valve.

19. The apparatus of claim 16, wherein the means for energizing the interior of the vessel is an electrode.

20. The apparatus of claim 16, wherein said means for attaching and/or exposing said inner wall of said plastic article to said manifold system is a rubber gasket.

21. The apparatus of claim 16, further comprising means for measuring pressure in the article.

22. The apparatus of claim 16, further comprising means for maintaining a pressure differential between said article and said manifold.

23. The apparatus of claim 22, wherein said means for maintaining a pressure differential is a valve.

24. The apparatus of claim 16, wherein the electrode is an inductive winding.

25. A method of applying a barrier film coating to an interior wall surface of a plastic substrate, the method comprising:

(a) placing a plastic article having an open end, a closed end, and outer and inner wall surfaces in a position such that the open end is connected to a vacuum manifold system having a monomer supply, an oxidizer supply, and a vacuum supply;

(b) positioning said outer wall surface of said plastic article in position with an electrode assembly;

(c) evacuating said interior of said article to about 0.001 mtorr to about 100 mtorr;

(d) delivering HMDSO monomer gas to said interior of said article at a pressure of from about 0.1sccm to about 50sccm and from about 80 millitorr to about 190 millitorr;

(e) delivering an atmospheric oxidant gas to said interior of said article at a pressure of from about 15 seem to about 35 seem and from about 110 millitorr to about 200 millitorr; and

(f) radio frequency power is supplied to the electrodes at about 5MHz to about 50MHz and about 15 watts to about 40 watts.

26. A method of applying a barrier film coating to an interior wall surface of a plastic substrate, the method comprising:

(a) placing a plastic article having an open end, a closed end, an outer portion, an inner portion, and outer wall and an inner wall surface in a position such that the open end is connected to a vacuum manifold system having a monomer supply, an oxidizer supply, and a vacuum supply;

(c) evacuating said interior of said article;

(d) delivering a monomer gas and an oxidant gas to said interior of said article;

(e) delivering radio frequency power to the electrode;

(f) ionizing the gas to form a plasma to apply a barrier film coating to the inner wall surface of the container;

(g) stopping the radio frequency power supply in step (e); and

(h) repeating steps (e) - (f).

27. The method of claim 26, wherein step (d) further comprises a diluent gas.

28. A method of coating a barrier film on an inner wall surface of a plastic substrate, the method comprising:

(c) evacuating the interior of the article;

(e) delivering radio frequency power to the electrode;

(g) stopping the gas delivery in step (d); and

(h) repeating step (d).

29. The method of claim 28, wherein step (d) further comprises a diluent gas.

30. A method of applying a barrier film coating to an interior wall surface of a plastic substrate, the method comprising:

(c) evacuating said interior of said article to a vacuum of from about 0.001 mtorr to about 100 mtorr;

(e) delivering an atmospheric oxidant gas to said interior of said article at a pressure of from about 15 seem to about 35 seem and from about 110 millitorr to about 200 millitorr;

(f) delivering radio frequency power to said electrode at about 5MHz to about 50MHz and about 5 watts to about 40 watts;

(g) stopping the gas delivery in step (d);

(h) stopping the radio frequency power supply in step (e); and

(i) repeating steps (d) - (h).

31. The method of claim 30, wherein step (d) further comprises a diluent gas.