U.S. patent application number 10/194248 was filed with the patent office on 2002-12-05 for container with a coating of barrier effect material, and method and apparatus for manufacturing the same.
This patent application is currently assigned to SIDEL. Invention is credited to Beldi, Nasser, Boutroy, Naima, Chollet, Patrick, Darras, David, Oge, Fabrice, Rius, Jean-Micl.
Application Number | 20020179603 10/194248 |
Document ID | / |
Family ID | 9524579 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020179603 |
Kind Code |
A1 |
Darras, David ; et
al. |
December 5, 2002 |
Container with a coating of barrier effect material, and method and
apparatus for manufacturing the same
Abstract
The invention provides a container such as a bottle or flask,
made heterogeneously from a material with a barrier effect and a
polymer material, characterized in that the material with a barrier
effect is an amorphous carbon material with a polymer tendency
which is applied as a coating on a substrate of polymer
material.
Inventors: |
Darras, David; (Le Havre,
FR) ; Rius, Jean-Micl; (Maneglise, FR) ;
Chollet, Patrick; (Lannion, FR) ; Boutroy, Naima;
(Pleumeur-Bodou, FR) ; Beldi, Nasser;
(Perros-Guirec, FR) ; Oge, Fabrice; (Lannion,
FR) |
Correspondence
Address: |
SUGHRUE, MION, PLLC
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037-3202
US
|
Assignee: |
SIDEL
|
Family ID: |
9524579 |
Appl. No.: |
10/194248 |
Filed: |
July 15, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10194248 |
Jul 15, 2002 |
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09647005 |
Sep 26, 2000 |
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09647005 |
Sep 26, 2000 |
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PCT/FR99/00692 |
Mar 25, 1999 |
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Current U.S.
Class: |
220/62.11 ;
425/363; 428/34.1; 428/35.7 |
Current CPC
Class: |
C23C 16/511 20130101;
Y10T 428/13 20150115; Y10T 428/31913 20150401; Y10T 428/1379
20150115; C23C 16/26 20130101; Y10T 428/31909 20150401; B65D
23/0821 20130101; Y10T 428/1352 20150115; Y10T 428/31855 20150401;
C23C 16/30 20130101; Y10T 428/30 20150115; H05H 1/4622 20210501;
H05H 1/463 20210501; Y10T 428/1383 20150115; B05D 1/62 20130101;
C23C 16/045 20130101; H05H 1/46 20130101; B65D 23/02 20130101 |
Class at
Publication: |
220/62.11 ;
428/34.1; 428/35.7; 425/363 |
International
Class: |
B32B 001/02; F16L
001/00; B65D 001/00; B32B 001/08; B29D 022/00; B29D 023/00; B65D
001/40; B65D 003/22; B65D 006/14; B65D 008/04; B65D 090/02; A23P
001/00; B29D 001/00; A23G 001/20; A23G 003/00; A21C 003/02; B28B
003/12; B28B 005/00; A21C 011/00; A01J 021/00; A01J 025/12 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 1998 |
FR |
98 03824 |
Claims
1. A container such as a bottle or flask, made heterogeneously from
a material with a barrier effect and a polymer material,
characterised in that the material with a barrier effect is an
amorphous carbon material with a polymer tendency which is applied
as a coating on a substrate of polymer material.
2. A container as claimed in claim 1, characterised in that the
material with a barrier effect is a nano-composite based on
amorphous carbon with a polymer tendency.
3. A container as claimed in claim 2, characterised in that the
material with the barrier effect is a nano-composite based on an
amorphous carbon with a polymer tendency incorporating metal
atoms.
4. A container as claimed in any one of the preceding claims,
characterised in that the coating of material with the barrier
effect is less than about 3000 .ANG. thick.
5. A container as claimed in claim 4, characterised in that the
coating of material with a barrier effect is between 50 and 1500
.ANG. thick.
6. A container as claimed in any one of the preceding claims,
characterised in that the polymer material is a polyolefin or a
polyester, in particular PET or PEN.
7. A container as claimed in any one of the preceding claims,
characterised in that the coating of material with a barrier effect
is applied to the substrate inside the container.
8. A container as claimed in any one of claims 1 to 6,
characterised in that the coating of material with a barrier effect
is applied to the substrate on the exterior of the container.
9. A method using a plasma excited by an electromagnetic wave to
form a container, such as a bottle or flask, made heterogeneously
from a material with a barrier effect and a polymer material
forming a substrate conforming to the shape of said container to be
produced, characterised in that said polymer material forming the
substrate is coated with a material with a barrier effect
comprising an amorphous carbon material with a polymer tendency,
consisting of the following steps: a blank of the container (18)
made from a polymer material forming the above-mentioned substrate
is placed in an enclosure (2), in which a high vacuum is created,
at least one carbon precursor is injected into the reaction chamber
(2, 18) in the gaseous state at a very low pressure, the precursor
being selected from the alkane, alkene, alkyne and aromatic
compounds or a combination of some of them, a microwave in the UHF
range is simultaneously electromagnetically excited in the reaction
chamber, at a relatively low power sufficient to generate a plasma
under temperature conditions which will maintain the polymer at a
temperature below the glass transition temperature on the one hand
and which will cause an amorphous carbon material with a polymer
tendency to be deposited on the other.
10. A method as claimed in claim 9, characterised in that the
container blank (18) made from polymer material is closed whilst
the gaseous carbon precursor is being injected into the enclosure
(2) onto the exterior of the blank, the volume between the
enclosure and the exterior of the blank constituting the reaction
chamber, whereby the coating of amorphous carbon material with a
polymer tendency is formed on the external surface of the container
blank.
11. A method as claimed in claim 9, characterised in that the
gaseous carbon precursor is introduced into the container blank
(18) made from polymer material, which then constitutes the
reaction chamber, at the same time as a pronounced vacuum is
created inside the container blank, whereby the plasma is formed in
the interior of the blank only and the coating of amorphous carbon
with a polymer tendency is deposited on the internal surface of the
container blank, and a vacuum is simultaneously created in the
enclosure in order to reduce the pressure differential between the
interior and the exterior of the blank.
12. A method as claimed in claim 11, characterised in that the
enclosure (2) is of a transverse dimension close to that of the
body of the container blank (18) so as to conform closely to the
container blank in order to make it easier to create a vacuum in
the enclosure.
13. A method as claimed in anyone of claims 9 to 12, characterised
in that the gaseous carbon precursor is injected at a pressure of
less than 1 mbar.
14. A method as claimed in any one of claims 9 to 13, characterised
in that before the internal coating of amorphous carbon material
with a polymer tendency is formed, an oxygen plasma is formed
inside the container blank (18) conducive to generating native
oxygen in order to clean the container blank.
15. A method as claimed in anyone of claims 9 to 13, characterised
in that before the internal coating of amorphous carbon material
with a polymer tendency is formed, a bactericidal agent is atomised
inside the container blank (18), after which an oxygen plasma is
formed, whereby the plasma generates a highly reductive medium
conducive to reducing bacterial contamination.
16. An apparatus which uses a plasma excited by electromagnetic
wave to form a container, such as a bottle or flask, made
heterogeneously from a material with a barrier effect and a polymer
material forming a substrate (container blank (18)) having the
shape of said container to be produced, this apparatus comprising a
plasma-generating device with an enclosure (2) fitted with means
(7) for injecting a gaseous precursor and electromagnetic
excitation means (8-12), characterised in that in order to coat
said polymer material forming the substrate with a material having
a barrier effect comprising an amorphous carbon material with a
polymer tendency, the means (7) for injecting the precursor are
connected to a means for generating a precursor in the gaseous
state, selected from the alkane, alkene, alkyne and aromatic
compounds or a combination of some of them, and injection means are
designed to deliver the gaseous precursor at a very low pressure,
and the electromagnetic excitation means (8-12) are of a sufficient
rating to generate microwaves in the UHF range.
17. An apparatus as claimed in claim 16, characterised in that the
enclosure (2) is of dimensions substantially larger than those of
the container blank (18) to be treated and in that the injection
means open into the enclosure (2) outside the container blank (18),
whereby, the container blank being closed, the apparatus generates
a plasma outside the container blank and it is on the external
surface of the container blank that the coating of amorphous carbon
material with a polymer tendency is deposited.
18. An apparatus as claimed in claim 16, characterised in that the
means (7) for injecting the gaseous precursor opens into the inside
of the container blank (18) placed inside the enclosure (2), in
that it is provided with pumping means (6) opening into the
container blank (18) and capable of generating a pronounced vacuum
therein, as a result of which the plasma is generated inside the
container blank which constitutes a reaction chamber and it is on
the internal surface of the container blank that the coating of
amorphous carbon material with a polymer tendency is deposited, and
in that the pumping means (6) are also arranged so as to generate a
vacuum in the enclosure (2) simultaneously in order to reduce the
pressure differential between the interior and the exterior of the
blank.
19. An apparatus as claimed in claim 18, characterised in that the
enclosure (2) is provided with a removable cover (4) providing a
sealed closure designed to support the injector (7) of the means
for injecting the gaseous precursor and the suction orifice (5) of
the pumping means and in that it also has means (17) designed to
support a container blank (18) by the neck thereof, applying the
lip (23) of said container blank in a tight seal against the
internal face (22) of said cover, surrounding said suction orifices
and the injector.
20. An apparatus as claimed in claim 19, characterised in that the
support means (17) can be axially displaced (19) in order to apply
the container blank against the internal face of the cover (4)
capping said suction orifices and injector prior to depositing the
coating or to remove the finished container therefrom after the
coating has been deposited.
21. An apparatus as claimed in claims 16 to 20, characterised in
that the microwave excitation means comprise a waveguide (8)
radially connected to a cavity (1) surrounding the enclosure (2),
said cavity (1) being provided with transverse short-circuit means
(10).
22. An apparatus as claimed in any one of claims 18 to 21,
characterised in that the enclosure (2) is of a transverse
dimension close to that of the body of the container blank
(18).
23. An apparatus as claimed in any one of claims 16 to 20,
characterised in that the microwave excitation means comprise
antenna (13) connected to a waveguide (15) and disposed radially in
a cavity (1) surrounding the enclosure (2), said cavity (1) being
provided with longitudinal short-circuit means (11).
24. An apparatus as claimed in any one of claims 16 to 20,
characterised in that the microwave excitation means comprise an
antenna (13) connected to a waveguide (15) and coaxially disposed
in a cavity (1) surrounding the enclosure (2), said cavity (1)
being provided with longitudinal short-circuit means (11).
Description
[0001] The present invention relates to containers, such as bottles
or flasks, of a heterogeneous structure made from a material which
produces a barrier effect and a polymer material.
[0002] The disadvantage of containers made from a polymer material
such as PET is that they are not impermeable to certain gases,
particularly oxygen and carbon dioxide.
[0003] This is the reason why carbonated drinks gradually lose
their carbon dioxide to the air through the polymer substance: the
shelf life of a carbonated liquid contained in a PET bottle will
not be more than a few weeks in terms suitability for sale or at
most a small number of months (for example 4 to 6).
[0004] This is also the reason how oxygen in the air is able to
penetrate the polymer material to come into contact with the liquid
in the container, placing it at risk of oxidation accompanied by a
deterioration in its properties: the shelf life of a bottle made
from PET and filled with beer will not be more than a few weeks
(for example 2 to 5 weeks) in terms of suitability for sale.
[0005] A known approach to this problem is to enhance the natural
barrier effect of the polymer substances used to make the
containers by lining the polymer wall with a layer of material
which has a stronger barrier effect.
[0006] Accordingly, it has been proposed that synthetic materials
in multiple layers be used for this purpose, such as those based on
aliphatic polyamides and/or mixtures of different substances. The
containers are then made using multi-layered preforms, in which the
layer of material with a barrier effect is located between at least
two layers of polymer material (for example PET). Beer bottles made
in this manner will have a considerably longer shelf life (for
example up to 12 months).
[0007] However, one major disadvantage of these multi-layered
containers is that the layers will come unstuck from one another.
In addition, making the preform, as well as making the container
from the preform by blow-moulding or by stretching-blow-moulding,
are quite complex processes and require certain precautions, which
makes them expensive.
[0008] Another proposal is that polymer containers be treated by
applying an external coating of an appropriate material such as
those known as PVDC or thermo-setting resins. However, the gain in
barrier effect achieved as a result is still quite low and the
presence of the coating material leads to difficulties when it
comes to recycling the basic polymer material.
[0009] Moreover, in all the known solutions mentioned above, the
polymer material (for example PET) is left in contact with the
liquid and does not offer any protection against the disadvantages
incurred by this contact: possibility of certain constituents
migrating from the polymer into the liquid, possibility of a
chemical reaction between the polymer and liquid, acetaldehyde
being transferred into the liquid, etc., all factors which are
likely to give rise to organoleptic problems.
[0010] It has also been proposed that a layer of material with a
barrier effect, for example hard carbon, be applied to a wall made
from polymer, for example PET, using plasma (document U.S. Pat. No.
5,041,303).
[0011] Document EP 0 773 166 also mentions the possibility of
forming such a layer of carbon on the internal face of the
container wall.
[0012] A carbon layer deposited in this manner would, of course,
remedy all the disadvantages listed above.
[0013] However, a relatively thick layer of hard carbon or
diamond-like carbon (DLC) would be needed. The wall of a container
made in this way would therefore have an internal layer of hard
carbon DLC, which is quite rigid, and an external layer of polymer
material such as PET, which is highly deformable. Due to their
differing and incompatible mechanical properties, the two layers of
polymer and hard carbon end up coming apart or unstuck.
[0014] Generally speaking, polymer containers with a barrier effect
by implementation of one of the techniques mentioned above are not
very common due to the complexity inherent in the different
processes, low production rates and the high cost of manufacturing
methods of this type.
[0015] The object of the invention is substantially to remedy
simultaneously all the problems mentioned above, as encountered
with known containers with an improved barrier effect, and to
propose a container which will effectively protect its contents
whilst being easy to manufacture on an industrial scale, using less
complex means under acceptable economic conditions.
[0016] To this end, in a first aspect, the invention proposes a
container such as a bottle or flask, heterogeneously made from a
material with a barrier effect and a polymer material which, as
proposed by the invention, is characterised in that the material
producing the barrier effect consists of an amorphous carbon
material with a polymer tendency, which is applied to a substrate
of polymer material. The substrate is a blank of the container and
already has the final shape of the container.
[0017] By amorphous carbon material with a polymer tendency is
meant carbon containing not only CH and CH.sup.2 bonds found in the
hard carbon, but also CH.sup.3 bonds which are absent in hard
carbon (to get a rough idea, the proportions of CH.sup.3, CH.sup.2
and CH are respectively 0, 40 and 60 in hard carbon and 25, 60 and
15 in amorphous carbon with a polymer tendency, whereas the
proportions of the electronic states sp.sup.3, sp.sup.2 and sp are
respectively 68, 30 and 2 in hard carbon and 53, 45 and 2 in carbon
of the polymer type).
[0018] Choosing an amorphous carbon material with a polymer
tendency overcomes the problem caused by the rigidity of hard
carbon or DLC: in practice, amorphous carbon materials with a
polymer tendency have a substantially lower mechanical rigidity
than that of hard carbon and the deformation capacity of a layer of
such a material is comparable with that of a polymer such as PET: a
container wall made as proposed by the invention using such an
amorphous carbon material with a polymer tendency adhered to a
substrate of polymer material such as PET will therefore be able to
withstand deformation at normal levels without these two layers
coming unstuck.
[0019] It is true that inherent in their physical and chemical
structure, amorphous carbon materials with a polymer tendency have
a lower molecular permeability coefficient than hard carbon which
has been used to date and it was thought that any barrier effect
they produced was less than perfect. This is one reason why they
have not been considered until now and why hard carbon or DLC was
used to provide layers with a barrier effect. Surprisingly, tests
conducted with amorphous carbon materials with a polymer tendency
have shown that the barrier effect obtained under certain operating
conditions is generally sufficient in practice for use in the
packaging of carbonated liquids or oxidizable liquids.
[0020] It would also be conceivable to use carbon-type
nano-composites (or DLN)--i.e. composites with reciprocally
interleaved dual networks, stabilised and random, one of which is a
network of amorphous carbon with a polymer tendency (a-c:H, with up
to 50% sp.sup.3 bonds) whilst the other may be a network of silicon
stabilised by oxygen (a-Si:o)-and nano-composites incorporating
metal atoms.
[0021] It is of advantage if the coating of amorphous carbon
material with a polymer tendency is of a thickness less than
approximately 3000 .ANG. (beyond that, too great a thickness
imparts too high a mechanical rigidity to the carbonated coating,
with the risk that it will rupture or become unstuck), preferably
between 800 and 1500 .ANG..
[0022] It should be pointed out that, although still transparent at
the above-mentioned thicknesses, amorphous carbon of the polymer
type is amber in colour which helps to protect against ultraviolet
rays (as a protection for beer in particular). It has been found
that under certain operating conditions, the effectiveness of the
barrier against ultra-violet afforded by this protection depends on
the thickness of the coating and, interestingly, increases sharply
with the intensity of ambient light (factor of about 8 in darkness
but a factor of about 30 in daylight).
[0023] The polymer material, which in practical applications is a
polyolefin or a polyester such as PET or PEN, may be used in a
reduced thickness because of the natural rigidity of the carbon
layer. On this subject, it should also be pointed out that the
carbon-based coating helps to reduce deformation of the container
wall when subjected to the pressure of a gaseous liquid, such as a
carbonated liquid. The container therefore retains a stable shape
and its interior volume remains constant: there is no change in the
composition of the liquid contained in it.
[0024] Although the coating with the barrier effect may be provided
on the exterior of the container blank, it is nevertheless
preferable if this coating forms the internal coating of the
container so that it will help to isolate the polymer material and
the liquid held in the container: the barrier effect will therefore
be extended and will render any migration of the polymer
constituents into the liquid, any chemical reaction between the
substances in the polymer and the liquid and any migration of
acetaldehyde into the liquid, etc., impossible.
[0025] It should be stressed, at this point, that the principle
underlying a container made as proposed by the invention is that
chemical bonds are established between the superficial carbon atoms
of the polymer substrate which have a free chemical bond and the
atoms of the carbon material which are brought into contact with
the polymer and have a free chemical bond, ready to combine with
the free bond of the superficial carbons in the polymer substrate.
Under these conditions, the coating of carbon material is linked to
the polymer substrate by a chemical and hence extremely powerful
bond; since the carbon material also has a polymer tendency as
explained above, the powerful chemical bond is nevertheless
accompanied by a relative capacity for deformation in the carbon
coating, these two features together providing a structure which no
longer exhibits the disadvantages (layers becoming unstuck in
particular) of the known containers made from hard carbon or
DLC.
[0026] A plasma deposition process can be used to deposit the
carbon coating, with carbon atoms having a free chemical bond
available for bonding with that of a superficial carbon atom in the
polymer.
[0027] Accordingly, a second aspect of the invention relates to a
method using a plasma excited by an electromagnetic wave to form a
container, such as a bottle or flask, made heterogeneously from a
material with a barrier effect and a polymer material forming a
substrate conforming to the shape of said container to be produced,
characterised in that said polymer material forming the substrate
is coated with a material with a barrier effect comprising an
amorphous carbon material with a polymer tendency, consisting of
two steps:
[0028] a blank of the container made from a polymer material
forming the above-mentioned substrate is placed in an
enclosure,
[0029] at least one carbon precursor is injected into the reaction
chamber in the gaseous state at a very low pressure of less than 10
mbar, the precursor being selected from the alkane, alkene, alkyne
and aromatic compounds or a combination of some of them,
[0030] a microwave in the UHF range is electromagnetically excited
in the reaction chamber with a relatively low power sufficient to
generate a plasma under temperature conditions which will maintain
the polymer at a temperature below the glass transition temperature
on the one hand and which will cause an amorphous carbon material
with a polymer tendency to be deposited on the other.
[0031] In a first possible implementing method, the container blank
made from polymer is closed whilst the gaseous carbon precursor is
being injected into the enclosure which is then the reaction
chamber, whereby the coating of amorphous carbon material with a
polymer tendency is deposited on the external surface of the
container blank.
[0032] In a second possible implementing method, the gaseous carbon
precursor is introduced inside the container blank of polymer
material, which then becomes the reaction chamber, whilst
simultaneously creating a pronounced vacuum in the container blank,
whereby a plasma is formed in the interior of the blank only and
the coating of amorphous carbon material with a polymer tendency is
deposited on the internal surface of the container blank;
furthermore, in order to prevent the container from deforming due
to the prevailing vacuum, a vacuum is simultaneously generated in
the enclosure to reduce the pressure differential between the
interior and the exterior of the blank. Moreover and by preference
in this instance, the enclosure is of a transverse dimension close
to that of the body of the container blank, closely conforming to
the container blank, so that a means with a lower power rating can
be used to generate the vacuum.
[0033] As a result of the features characterising the method
proposed by the invention, a coating of amorphous carbon material
with a polymer tendency can be deposited at the requisite low
thickness of less than 3000 .ANG. and in particular between 800 and
1500 .ANG. in a short time of a few seconds and not more than about
twenty seconds, with a modest microwave power in the order of a few
hundred watts (for example about 200 to 600 W) producing a power
density of about 0.5 to 2 watts per cubic centimeter. As a result,
the corresponding increase in temperature within the polymer
material of the container blank forming the substrate on which the
carbon coating will be deposited (inside or outside, as is the
case) remains relatively low and below the glass transition
temperature of the polymer (approximately 80 in the case of
PET).
[0034] These are the conditions under which the carbon coating is
formed under the action of a microwave plasma at low pressure (not
exceeding a few millibars and in practice in the order of 0.01 and
0.5 mbar) or "cold plasma", causing an amorphous carbon structure
with a polymer tendency to be formed, i.e. consisting of or
containing an over-hydrogenated amorphous carbon network exhibiting
the advantageous properties listed above.
[0035] Apart from obtaining a container with a barrier effect which
is mechanically well bonded onto the polymer substrate, the method
proposed by the invention offers the notable advantage of
facilitating the manufacture of sterile containers which may be
used in aseptic packaging production lines.
[0036] The plasma generated during the process of depositing the
carbon coating is sufficient to clean the internal surface of the
container blank as desired.
[0037] In order to obtain a more intense aseptic effect, it would
be conceivable to use a bactericidal agent beforehand, atomised to
produce micro-droplets or introduced in vapour form, for example
with a bubble system, onto the internal surface of the container
blank (for example hydrogen peroxide, phosphoric acid, steam,
etc.); subsequent generation of a plasma under the above-mentioned
conditions will create a highly reductive medium (by generating
native oxygen for example) which is capable of reducing the initial
bacterial contamination so as to meet the sterilisation
requirements.
[0038] In implementing the method described above, a third aspect
of the invention is an apparatus which uses a plasma excited by
electromagnetic wave to form a container, such as a bottle or
flask, made heterogeneously from a material with a barrier effect
and a polymer material forming a substrate (container blank) having
the shape of said container to be produced, this apparatus
comprising a plasma-generating device with an enclosure fitted with
means for injecting a gaseous precursor and electromagnetic
excitation means, which apparatus is characterised in that in order
to coat said polymer material forming the substrate with a material
having a barrier effect comprising an amorphous carbon material
with a polymer tendency, the means for injecting the precursor are
connected to a means for generating a precursor in the gaseous
state, selected from the alkane, alkene, alkyne and aromatic
compounds or a combination of some of them, in that in order to
coat said polymer material forming the substrate with a material
having a barrier effect comprising an amorphous carbon material
with a polymer tendency, the injection means open into the
enclosure and are designed to deliver the gaseous precursor at a
very low pressure of less than 10 mbar, and in that the
electromagnetic excitation means are of a sufficient rating to
generate microwaves in the UHF range.
[0039] In a first embodiment, the dimensions of the enclosure are
substantially larger than those of the container blank to be
treated and injection means open into the enclosure outside the
container blank, whereby, the container blank being closed, the
apparatus generates a plasma outside the container blank and it is
on the external surface of the container blank that the coating of
amorphous carbon material with a polymer tendency is deposited.
[0040] In a second embodiment, the means for injecting the gaseous
precursor open into the interior of the container blank arranged in
the enclosure and pumping means are provided opening into the
container blank and capable of generating a pronounced vacuum
therein, whereby the plasma is generated inside the container blank
and it is on the internal surface of the container blank that the
coating of amorphous carbon material with a polymer tendency is
deposited. In order to prevent the blank from deforming due to the
vacuum prevailing in the interior, a vacuum is simultaneously
created inside the enclosure to reduce the pressure differential
between the interior and the exterior of the blank. Advantageously
in this case, the enclosure is provided with a removable cover
producing a tight seal, designed to support the injector for the
gaseous precursor and the suction orifice of the pumping means; it
also has support means designed to support a container blank by the
neck thereof, applying the lip of said container,blank against the
interior face of said cover, surrounding said suction and injector
orifices. It is also desirable to be able to displace the support
means axially in order to apply the container blank against the
interior face of the cover, capping said suction and injector
orifices prior to depositing the coating, or in order to remove the
finished container once the coating has been deposited.
[0041] By preference, in order to facilitate use of the pumping
means and avoid having to use means of a higher capacity than
necessary, the enclosure has a transverse dimension close to that
of the body of the container blank.
[0042] As a result of the features proposed by the invention, in
particular due to the reduced processing times, it is possible to
mount a method of manufacturing a container with a barrier effect
on an industrial scale, which will enable containers to be produced
at a rate compatible with current requirements for packaging
liquids.
[0043] The invention will be more readily understood from the
detailed description below of certain embodiments, given by way of
illustration only and not restrictive in any respect. Throughout
the description, reference will be made to the appended drawings,
of which:
[0044] FIGS. 1 to 3 provide schematic illustrations, in section, of
three respective embodiments of an apparatus enabling a container
having a layer of material with a barrier effect to be produced, as
proposed by the invention, and
[0045] FIG. 4 is a section view of a preferred embodiment of the
apparatus illustrated in FIG. 1, set up with a view to forming a
layer of material with a barrier effect on the interior of the
container.
[0046] Turning firstly to FIG. 1, the apparatus comprises a cavity
1, with conductive walls, made from metal for example, the
dimensions of which are selected depending on the object to be
processed and the coupling mode required, surrounding an enclosure
2 defined by walls 3 made from a material transparent to
electromagnetic microwaves, such as quartz for example.
[0047] The enclosure 2 is closed at the top by a removable cover 4,
for example, which enables the object to be processed to be placed
in the enclosure and removed after treatment.
[0048] To enable a vacuum to be generated, the enclosure 2 is
connected to external pumping means (not illustrated) by means of
at least one connector: in FIG. 1, two connectors 5 are provided in
the base and the cover 4 respectively (pumping symbolised by arrows
6).
[0049] In order to inject at least one gaseous precursor into the
enclosure 2, preferably at a pressure below 1 mbar, at least one
injector 7 is provided, connected to at least one generator of
gaseous or liquid precursor (not illustrated), such as a tank, a
mixer or a bubble system. The injector 7 runs through the cover to
which it is attached, extending coaxially inside the connector 5 of
the pumping means, for example.
[0050] The cavity 1 is connected to an electromagnetic microwave
generator (not illustrated) by a waveguide 8 extending radially
relative to the side wall of the cavity 1. This waveguide is
provided with regulating means, for example plunger screws 12,
enabling the cavity to be tuned. At the opposite end (diametrically
opposed if the cavity describes a cylinder as is the case in
practical applications) is a section of waveguide 9 fitted with an
axially displaceable tuning plunger 10 constituting a transverse
short-circuiting device.
[0051] Finally, arranged respectively at the top and bottom of the
cavity 1 are two annular plates 11 surrounding the enclosure 2 and
constituting longitudinal short-circuits for the microwaves.
[0052] In the case where the intention is to deposit carbon on the
substrate of polymer material, i.e. on the wall of the container
blank made from polymer material, the gaseous precursor may be
selected from the alkane (for example methane), alkene, alkyne (for
example acetylene) and aromatic compounds.
[0053] The pressure within the reaction chamber (constituted either
by the enclosure or by the container blank as will be explained
later) must be low, preferably less than approximately 10 mbar, in
practice in the order of 0.01 to 0.5 mbar.
[0054] In addition, it is crucial that the heating to which the
polymer material of the substrate is subjected is kept low enough
to ensure that the glass transition temperature of the polymer is
not reached (which is in the order of 80 c in the case of PET, for
example). It is therefore necessary to use a very low microwave
power for the deposition reaction, for example of a few hundred
watts at most with microwaves in the UHF range (for example in the
order of 2.45 GHz).
[0055] As a result of the deposition conditions, in particular the
low temperature at which the carbon is deposited, a highly
hydrogenated amorphous carbon is produced, containing not only the
CH and CH.sup.2 radicals but also a notable fraction of CH.sup.3
radicals. The carbon produced is therefore one with a polymer
tendency or "soft" carbon, which is less rigid than hard carbon or
DLC. This layer of carbon with a polymer tendency is therefore
capable of deforming, which makes it capable of conforming to
deformation of the polymer forming the substrate, insignificant
though it may be. This results in an improved mechanical coupling
of the polymer substrate with the carbon and the risk of unsticking
is therefore sharply reduced, even eliminated.
[0056] However, it should be pointed out that although it is less
rigid than hard carbon or DLC, carbon with a polymer tendency or
"soft" carbon also retains a significant rigidity which in any
event is considerably higher than that of the polymer forming the
substrate. This being the case, it would be conceivable to use the
carbon layer for functional purposes as a means of imparting some
of the intrinsic rigidity to the finished container; consequently,
it may be that the polymer substrate does not have to provide the
function of mechanical strength within the container to a certain
extent. The thickness of the polymer substrate can be duly reduced
and the quantity of polymer used to manufacture each container
therefore reduced accordingly.
[0057] Furthermore, the fact of providing the carbon layer
reinforces the mechanical strength of the container and, as a
result, reduces or even eliminates the deformation capacity of a
container filled with a highly carbonated liquid: the shape and
thus the volume of the container remain stable, thereby preventing
part of the gas from being released from the liquid.
[0058] Clearly, the advantages outlined above are additional to the
fundamental advantage primarily sought, which is to produce a
barrier effect, in particular against gaseous exchanges between the
liquid contained in the container and the ambient atmosphere.
[0059] Finally, due to the implementing features proposed by the
invention, the deposition process can be operated at a rate of
several hundred Angstrom per second, achieving a processing time in
the order of a few seconds, which will be perfectly compatible with
industrial manufacturing processes.
[0060] Clearly, other embodiments of the apparatus would be
conceivable as a means of generating the plasma needed to deposit
the layer of amorphous carbon material with a polymer tendency,
sought in the context of this invention.
[0061] For example, the embodiment illustrated in FIG. 2, whilst
retaining the same design of cavity 1 and enclosure 2 (the same
reference numbers are used to denote elements which are the same as
those illustrated in FIG. 1), the microwave in this case is excited
by an antenna 13 which penetrates the cavity 1 radially through the
side wall thereof and which is connected to a waveguide in
transverse mode by a coaxial conductor 14.
[0062] FIG. 3 illustrates another embodiment with an axial
microwave cavity using an antenna 13, which is mounted in the base
of the cavity 1, substantially transversely to said base and more
or less coaxial with the enclosure 2. The longitudinal short
circuit in this case is achieved by the top annular plate 11 only,
whilst a single pumping orifice 5 is provided in the enclosure
2.
[0063] The various embodiments of the apparatus described above
enable the carbon material to be deposited on the external face of
the container blank made from polymer material: this being the
case, the volume of the enclosure 2 is markedly bigger than that of
the container blank so as to allow the plasma to build up, the
container blank being stoppered to prevent any deposition on the
interior.
[0064] However, as mentioned above, an external coating of carbon
material procures only a partial barrier effect which does not
prevent interactions between the polymer of the substrate and the
contents, generally liquid.
[0065] A total barrier effect can therefore be produced only if a
coating with a barrier effect is applied to the substrate inside
the container. The processing apparatus needs to be modified in
order to produce an internal coating of this type.
[0066] FIG. 4 illustrates an embodiment of the apparatus
illustrated in FIG. 1, designed to deposit an internal layer of
carbon. The enclosure 2 is preferably of a shape such that its
transverse or diametral dimensions are slightly larger than those
of the container blank to be processed, so as to facilitate the
process of placing the enclosure under vacuum as described below.
In order to prevent the blank from deforming due to the vacuum
prevailing inside, a vacuum is simultaneously created inside the
enclosure to reduce or even cancel out the pressure differential
between the interior and the exterior of the blank.
[0067] The cover 4, which is vertically mobile (double arrow 16)
enabling the container blank to be positioned and the treated blank
to be removed, has a vertical support arm 17 running through it for
the container blank 18; this arm is vertically mobile (double arrow
19) and optionally may rotate.
[0068] The cover 4 has an internal packing 20 provided with an
axial passage 21 into which or facing which the injector 7 for the
gaseous precursor opens. At its bottom end, the axial passage 21 is
shaped to form a seat 22 designed to receive and essentially seal
the lip 23 of the neck of the container blank 18 with a view to
axially positioning the container blank accurately. The packing 20
also has an annular opening, through which said support arm 17
passes, communicating with the central passage 22; this opening
forms the suction orifice 5 in the direction of the pumping means
to establish the vacuum. To ensure that the conditions conducive to
establishing the plasma occur in the container blank only, a
pronounced vacuum is established therein at the same time as said
compensating vacuum is established in the enclosure.
[0069] As a result of this layout, a plasma can be created inside
the container blank, which therefore acts as the actual reaction
chamber, enabling an internal deposit of carbon material to be
applied.
[0070] By way of example, the apparatus illustrated in FIG. 4 was
operated using acetylene as the gaseous precursor, introduced into
the neck of the container blank by an injector with a 4 mm diameter
at a rate of 80 sccm and at a pressure of 0.25 mbar. The residual
pressure inside the blank is in the order of 0.2 mbar and it was
found that a residual pressure of 50 mbar inside the enclosure was
enough to prevent any deformation in the blank under these
conditions. Excitation was by microwaves in the UHF range at a
frequency of 2.45 GHz (that is to say a wavelength .lambda.=12 cm
under vacuum); the microwave output is in the order of 180 W. Under
these conditions, it proved possible to apply a carbon deposit at a
growth rate in the order of 250 .ANG./s, i.e. to obtain a coating
with a thickness of 1500 .ANG. in a time of about 6 seconds.
[0071] In a second example, a piece of apparatus of the type
illustrated in FIG. 4 was used, injecting acetylene into the
container blank at a rate of about 160 sscm at a pressure of about
0.1 mbar. In this case, with a microwave output of about 350 W for
a half-liter bottle or about 500 W for a one-liter bottle, an
effective barrier coating was produced in a time of about 2 to 3
seconds.
[0072] Depending on the processing conditions (duration in
particular), using plasma for the process of manufacturing the
container provides a simple means of cleaning or disinfecting
(sterilisation) the interior of the container in plants operating a
container production, filling and sealing line in an aseptic
environment.
[0073] The plasma generated whilst the carbon layer is being
deposited may be sufficient to clean the internal surface of the
blank to an initial degree.
[0074] For a more intensive treatment, a simple oxygen plasma may
be used, created from reactive species, such as meta-stable
species, atomic or molecular oxygen for example, which are capable
of reducing the initial bacterial contamination by the action of
their natural energy to a sufficient degree to meet health
criteria.
[0075] These treatments are carried out in times of less than ten
seconds, which is compatible with industrial installations.
[0076] In order to obtain a high degree of sterilisation, it will
be necessary to use a bactericidal agent such as hydrogen peroxide
H.sub.2O.sub.2 on which, after a predetermined contact time with
the blank, an oxygen plasma is allowed to act: the
physical-chemical phenomena generated by the plasma in the hydrogen
peroxide-oxygen mixture generate the reactive species mentioned
above along with others which are significantly reductive and have
a powerful anti-bacterial effect.
[0077] Plasma treatment may also be considered as a means of
removing a bactericidal agent such as phosphoric acid which is a
reducer.
[0078] At this point, it should be stressed that, independently of
its function as a bactericide, hydrogen peroxide also creates free
radicals among the carbon atoms of the polymer present at the
surface of the substrate: as a result, an increased number of free
radicals is produced at the polymer surface susceptible to
receiving carbon atoms deposited on the surface, thereby
strengthening the chemical bonds established between the polymer
and the carbon deposited on its surface. Consequently, it would
also be conceivable to spray the surface of the substrate with
hydrogen peroxide prior to depositing the carbon coating in a
plasma atmosphere, before subjecting it to an oxygen plasma in
order to improve adherence of the carbon coating to the
polymer.
* * * * *