FR2814382A1 - METHOD FOR DEPOSITING AN INTERNAL COATING IN A PLASTIC CONTAINER - Google Patents

Abstract

The invention concerns a method for making plastic containers, which includes shaping the container, deposition of a coating having barrier properties to diffusion on an internal surface, said method being plasma-assisted under pressure close to atmospheric pressure. The invention is characterised in that said coating has a thickness ranging between 150 and 1500 ANGSTROM and comprises a material or a mixture of materials belonging to the following group: amorphous carbon, hydrogenated or not, nitrogenous or not, oxides, nitrides or carbides or their mixture or their combination of one or several of the following metals (Si, Mg, Al, Ti, Zr, Nb, Ta, Mo, W, V). Preferably the coating is a mixture comprising carbon with polymeric trend and silicon oxide and the substrate is a thermoplastic material such as polyolefin, typically polyethylene or polypropylene, or a polyester, typically, PET or PEN.

Description

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TECHNICAL FIELD The invention relates to a method of depositing an internal coating in a plastic container. These containers are intended to contain liquid to pasty products such as pharmaceuticals, parapharmaceuticals, cosmetics and food.

STATE OF THE ART Plastic containers are generally known for their good chemical stability at low temperatures. On the other hand, the relatively high permeability of plastics conventionally used for the preparation of containers did not make it possible to obtain containers of a single polymeric material effectively protecting the product against a possible loss of aroma or oxidation by ambient air.

We know from US 4,712,990, US 4,518,344, US 4,512,730, US 4,554,190 and US 4,497,621 a process for obtaining fully plastic containers, easy to recycle, satisfactorily protecting food products against possible loss of aroma and pollution by ambient air in the event of prolonged storage. These containers are produced by coinjection molding of several polymeric materials, for example one or more polyolefins and a material with improved barrier property such as EVOH (ethylene-vinyl alcohol copolymer).

WO9522413, FR 2 776 540, DE 43 16 349 and EP 0 773 166 disclose methods for obtaining the deposition of a coating, essentially

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constitué de carbone amorphe sur la surface interne de récipients en matière plastique telle qu'une polyoléfine ou un polyester tel que le PET (polyéthylène téréphtalate) ou le PEN (polyéthylène naphtalate). Il a été en effet constaté que la couche de carbone amorphe présentait de bonnes propriétés barrières à la diffusion qui pouvaient compléter avantageusement celles, non négligeables de matériaux tels que le PET.

consisting of amorphous carbon on the internal surface of plastic containers such as a polyolefin or a polyester such as PET (polyethylene terephthalate) or PEN (polyethylene naphthalate). It has in fact been found that the amorphous carbon layer had good diffusion barrier properties which could advantageously complement those, which are not negligible of materials such as PET.

PROBLEM POSED The first process, consisting of co-injecting different polymeric materials is a complex process requiring the installation of sophisticated machines with molding tools comprising a very large number of feed channels which must lead the good material to be injected to the right place. The viscosity of a material being very sensitive to temperature, the simultaneous flow of the same polymeric material in a large number of channels requires perfect control of the temperature prevailing in the multiple injection tool. In addition, the simultaneous injection of several polymeric materials of very different viscosities - at equal temperature, EVOH is much more viscous than the polyolefins it coexists makes the problem of controlling structural stability even more complex (distribution of thicknesses ) and geometric of the co-injected products. The development of such devices is therefore delicate and costly. It can only be justified for containers produced in very large series.

The second type of process is based on a deposit assisted by a plasma generated in a vacuum enclosure. This type of process is not very compatible with production at high rates and requires the use of complex devices for its implementation in the context of production in large series (sealed enclosures, pumps for achieving high voids

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en très peu de temps, générateurs de hautes fréquences, dispositifs de manipulation automatisée, etc...). La demanderesse a donc cherché un procédé plus économique permettant d'atteindre le même but : obtenir des récipients entièrement polymériques capable de préserver à l'abri de l'air ambiant et de conserver les arômes des produits tels que des produits pharmaceutiques, para pharmaceutiques, cosmétiques et alimentaires.

in a very short time, high frequency generators, automated handling devices, etc.). The Applicant has therefore sought a more economical process allowing the same goal to be achieved: obtaining fully polymeric containers capable of preserving, sheltered from ambient air and of preserving the aromas of products such as pharmaceuticals, para-pharmaceuticals, cosmetics and food.

ou leur combinaison d'un ou plusieurs des métaux suivants (Si, Mg, AI, Ti, Zr, Nb, Ta, Mo, W, V). OBJECT OF THE INVENTION A first object of the invention is a process for manufacturing plastic containers including, after the container has been shaped, the deposition on the internal surface of a coating having diffusion barrier properties, said process being carried out by plasma assistance under a pressure close to atmospheric pressure, characterized in that said coating has a thickness of between 150 and 1500 and comprises a material or a mixture of materials belonging to the following group: amorphous carbon, hydrogenated or not, nitrogenous or not, oxides, nitrides or carbides or their mixture

or a combination of one or more of the following metals (Si, Mg, AI, Ti, Zr, Nb, Ta, Mo, W, V).

Preferably, this deposition is carried out on the internal surface of the container at a speed compatible with industrial production rates, typically of one or more hundreds of units per minute.

More particularly, the deposit can comprise amorphous carbon, hydrogenated or not, nitrogenous or not, that is to say a material with a polymer tendency, characterized by a network of chains of amorphous carbon capable of comprising hydrogen or nitrogen bonds. The Applicant has found that such a deposit has very good diffusion barrier properties.

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d'arômes tels que ceux introduits dans les produits pharmaceutiques, para pharmaceutiques, cosmétiques et alimentaires. Le produit peut ainsi conserver tous ses arômes.

aromas such as those introduced into pharmaceutical, para-pharmaceutical, cosmetic and food products. The product can thus retain all of its aromas.

composé SiOx, où x est compris entre 1, 8 et 2, 1 suivant le rapport des concentrations en oxygène et en silicium dans le plasma formé. La demanderesse a constaté qu'un tel dépôt a de très bonnes propriétés barrière à la diffusion de l'oxygène. Le produit reste ainsi à l'abri de l'oxydation par l'air ambiant en cas de stockage prolongé. It can also include silicon oxide, typically a

SiOx compound, where x is between 1, 8 and 2, 1 depending on the ratio of oxygen and silicon concentrations in the plasma formed. The Applicant has found that such a deposit has very good barrier properties to the diffusion of oxygen. The product thus remains protected from oxidation by ambient air in the event of prolonged storage.

Preferably, the deposit is a mixture comprising carbon with a polymer tendency and silicon oxide (which we will call hereinafter "silica" for simplicity). The product can thus retain all of its aromas and remains protected from oxidation by ambient air in the event of prolonged storage. The mixture can be homogeneous throughout the thickness of the coating. It can also be very rich in carbon in the vicinity of the substrate and very rich in silica on the surface, the concentration of the respective elements varying continuously between these extreme points of the coating. In this way, one obtains a gradual deposition of layers first rich in amorphous carbon then rich in silica. The hydrogenated amorphous carbon, located in a sublayer, ensures better bonding on the thermoplastic polymer substrate and ensures greater flexibility in the coating obtained. The silicon oxide layer completes the barrier effect of the carbon layer while limiting the coloring due to carbon.

The deposition is carried out on the internal surface of the container made of polymeric material, the latter being a thermoplastic material such as a polyolefin or a polyester, typically PET or PEN. The wall of such a container can thus be free of a polymeric layer with properties

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barrières, rigide et difficile à injecter simultanément avec les autres couches constitutives de la paroi. Le revêtement selon l'invention confère à la structure de la paroi du tube des propriétés barrières satisfaisantes. L'épaisseur du revêtement est variable selon le matériau choisi. Elle doit être suffisamment épaisse pour conférer à la structure des propriétés barrières se traduisant . pour l'oxygène, par une perméabilité inférieure à 1 ml/m2/jour/atmosphère (norme ASTMD3985) . pour la vapeur d'eau, par une perméabilité inférieure à 2 g/m2/jour/atmosphère (norme ASTM F327) . et pour les arômes, par une perméabilité inférieure à 0,5 10-6 g/m2/jour/mmHg Jusqu'à présent, les conteneurs en matière plastique envisagés pour être utilisés dans le domaine de l'invention étaient, même si cela ne suffisait pas, réalisés dans une matière choisie parmi les matières polymériques ayant des propriétés barrières à la diffusion des gaz améliorées (par exemple le PET). Avec le dépôt réalisé dans le mode préférentiel de l'invention, c'est-à-dire un revêtement composé d'un mélange carbone amorphe et silice, homogène ou à composition graduelle, nous pouvons obtenir, même avec une faible épaisseur du revêtement, des propriétés barrières satisfaisantes de telle sorte qu'il n'est pas nécessaire de choisir un matériau particulier pour le substrat (matière de base de la paroi du conteneur) et que l'on peut prendre des matériaux moins performants en ce qui concerne leur perméabilité mais plus faciles à mettre en oeuvre. Ainsi, une simple polyoléfine peut suffire, en particulier du polypropylène. Celui-ci présente contrairement au PET l'avantage d'être nettement plus facile à mettre en forme : il n'est pas nécessaire de réaliser des préformes et de contrôler le processus de mise en forme pour obtenir un matériau bi-orienté. Le coût de fabrication de tels conteneurs s'en trouvent notablement diminué.

barriers, rigid and difficult to inject simultaneously with the other constituent layers of the wall. The coating according to the invention gives the structure of the wall of the tube satisfactory barrier properties. The thickness of the coating is variable depending on the material chosen. It must be thick enough to give the structure translating barrier properties. for oxygen, by a permeability of less than 1 ml / m2 / day / atmosphere (standard ASTMD3985). for water vapor, by a permeability of less than 2 g / m2 / day / atmosphere (standard ASTM F327). and for the aromas, by a permeability of less than 0.5 10-6 g / m2 / day / mmHg Until now, the plastic containers envisaged for use in the field of the invention were, even if this did not not enough, made of a material chosen from polymeric materials having barrier properties to the diffusion of improved gases (for example PET). With the deposit produced in the preferred embodiment of the invention, that is to say a coating composed of a mixture of amorphous carbon and silica, homogeneous or of gradual composition, we can obtain, even with a small thickness of the coating, satisfactory barrier properties so that it is not necessary to choose a particular material for the substrate (basic material of the container wall) and that less efficient materials can be taken with regard to their permeability but easier to implement. Thus, a simple polyolefin may suffice, in particular polypropylene. Unlike PET, this has the advantage of being much easier to shape: it is not necessary to make preforms and control the shaping process to obtain a bi-oriented material. The cost of manufacturing such containers is significantly reduced.

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Selon l'invention, on effectue ce dépôt en utilisant un réacteur plasma de traitement de surface. Le plasma peut être généré sous différents types de décharges : décharge au travers d'une barrière diélectrique ou décharge de type corona avec différents types d'excitation : micro-ondes, radiofréquences, courant alternatif de moyenne fréquence. Ces types de génération de plasma présentant l'avantage de pouvoir se faire sous une pression voisine de la pression atmosphérique.

According to the invention, this deposition is carried out using a plasma surface treatment reactor. The plasma can be generated under different types of discharges: discharge through a dielectric barrier or corona type discharge with different types of excitation: microwave, radio frequency, medium frequency alternating current. These types of plasma generation have the advantage of being able to be carried out under a pressure close to atmospheric pressure.

The coating is obtained by condensation after decomposition of a body or a gaseous compound. The plasma can be generated by dielectric barrier discharge or corona discharge. In this case, the working pressure can be close to atmospheric pressure, which is appreciable because the treatment time can be significantly reduced and the operation can be integrated more easily into the normal cycle of high-speed production.

A particularly advantageous embodiment of the invention consists in placing the container in a device comprising two electrodes: an external one conforming as best as possible to the shape of the container and another intended to enter the container. The device also has a supply means injecting a precursor gas inside the container. After a certain time necessary to evacuate the ambient air and replace it with the precursor gas, the electrode introduced inside the container is brought to an alternating voltage of about ten kV, the external electrode being connected to the earth, to generate the plasma.

If the container is a body provided with a bottom connected to a vertical wall and a neck connected to said vertical wall by a shoulder, the external electrode can have a simple shape (vertical wall and bottom matching the shape of the bottom of the container) but, in this case, the deposition of the coating at the shoulder and

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du goulot risque d'être irrégulier et peu épais. On peut alors envisager d'améliorer le dispositif soit en construisant l'électrode externe en plusieurs parties mobiles radialement, lesdites parties ayant une surface interne épousant la forme externe du conteneur, épaule et goulot inclus. Le déplacement radial est défini de telle sorte que le diamètre de l'ouverture offerte lorsque lesdites parties mobiles sont en position extrême soit supérieur au diamètre maximum de la paroi verticale du conteneur.

the neck may be irregular and not very thick. One can then envisage improving the device either by constructing the external electrode in several radially movable parts, said parts having an internal surface matching the external shape of the container, shoulder and neck included. The radial displacement is defined so that the diameter of the opening offered when said moving parts are in the extreme position is greater than the maximum diameter of the vertical wall of the container.

If this vertical wall is cylindrical, one can also envisage a device similar to that illustrated in FIGS. 10e and 10f and presented in example 3 of the application WO 99/46964: as the container has a symmetry of revolution, it is made to rotate around its axis of symmetry and the internal surface of the wall of the container is passed through a confined plasma in the form of a bead. In this case, the electrodes have a simpler shape, the positioning of the container is faster and does not require a complex device with radially movable parts; finally the plasma generated has a more stable spatial extent.

This process has the advantage of being able to be carried out under a pressure close to atmospheric pressure, preferably between 200 and 760 millimeters of mercury. A slightly lower pressure than atmospheric pressure allows better control of the purity of the gas circulating in the container. Preferably, a preliminary sweep is carried out with an inert gas, of the argon type to avoid the formation of impurities (risk of reaction with nitrogen in the air, water vapor, etc.) which may deteriorate. the quality of the adhesion of the layer thus deposited.

We are targeting a deposit thickness between 150 Å and 1500 Å, preferably less than 300 Å. The material to be deposited can be any material having good barrier properties to the diffusion of aromas and gases. To obtain a

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dépôt d'alumine, on emploie de préférence comme gaz précurseur du tributyle-aluminium AI (C4H9) 3 que l'on fait circuler dilué dans un mélange argon et oxygène. Pour obtenir un dépôt de carbone amorphe, on fait passer un courant de gaz carburé, typiquement de l'acétylène C2H2 ou du fluorure de carbone CF4. Pour obtenir un dépôt d'oxyde de silicium, on fait circuler un gaz tel que l'HMDSO (hexaméthyldisiloxane) ou le TMDSO (tétraméthyldisiloxane).

deposit of alumina, preferably used as a precursor gas tributyl aluminum AI (C4H9) 3 which is circulated diluted in an argon and oxygen mixture. To obtain an amorphous carbon deposition, a stream of carburetted gas is passed, typically acetylene C2H2 or carbon fluoride CF4. To obtain a deposit of silicon oxide, a gas such as HMDSO (hexamethyldisiloxane) or TMDSO (tetramethyldisiloxane) is circulated.

Finally, to obtain the deposition of a mixed carbon + silica coating, a mixture of carburetted gas and precursor gas is circulated for the deposition of silica. This mixture has a constant composition or, in the “gradual deposition” variant mentioned above, a variable composition passing continuously from 100% of fuel gas at the start of treatment to 100% of precursor gas for the deposition of silica (hexa- or tetramethyldisiloxane for example) at the end of treatment.

The figure shows schematically in axial section a first device intended to implement the method according to the invention. A second device, particularly well suited to axisymmetric containers, is described in Example 3 of application WO 99/46964 and illustrated in Figures 10e and 10f of this same document.

EXAMPLE (Figure) The internal wall of the container of this example, made of polypropylene, was covered with a thick coating of 250 angstroms and comprising a mixture of amorphous carbon and silica. The coating was deposited by plasma assistance using the device illustrated in the figure.

While the external electrodes 20 and 21 are placed in an extreme radial position (direction of the arrows 22), the container 10 is placed inside the volume occupied by said electrodes 20 and 21. The container 10 has a bottom 11, a

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paroi verticale 12, un goulot 13 et une épaule 14 reliant la paroi verticale au goulot. Les électrodes externes se rapprochent grâce à un mouvement radial centripète et enserrent le conteneur 10. Une électrode centrale 30 est introduite dans le volume interne du conteneur. Lorsque ce conteneur est un boîtier cylindrique de 45 mm de diamètre, l'électrode 30 a de préférence un diamètre de 17 mm. Lorsque l'électrode 30 est enfoncée, sa partie 31 au regard de l'épaule 14 et du goulot 13 du boîtier est électriquement isolée avec un manchon isolant 40. La longueur du manchon isolant, typiquement en téflon, est déterminée de telle sorte qu'il n'y ait pas de dépôt préférentiel au niveau de l'épaule ou du goulot.

vertical wall 12, a neck 13 and a shoulder 14 connecting the vertical wall to the neck. The external electrodes approach by means of a centripetal radial movement and enclose the container 10. A central electrode 30 is introduced into the internal volume of the container. When this container is a cylindrical case 45 mm in diameter, the electrode 30 preferably has a diameter of 17 mm. When the electrode 30 is pushed in, its part 31 facing the shoulder 14 and the neck 13 of the housing is electrically insulated with an insulating sleeve 40. The length of the insulating sleeve, typically made of Teflon, is determined so that there is no preferential deposit at the shoulder or the neck.

The electrode 30 is hollow. It has a dozen small diameter perforations 32 (0 <0.1 mm) in the lower part and a few perforations of the same diameter above. Before the generation of the plasma, argon is injected inside the electrode 30 and entrains the ambient air towards the outside of the container. Then the precursor gas is injected - an acetylene-ATSMO mixture - and the electrode 30 is brought to an alternating voltage of about ten kV, the external electrode being connected to earth, to generate the plasma.

revêtement. Une dizaine de secondes suffit pour obtenir un revêtement de 250 À. The gas circulates from bottom to top (arrows 50) and the plasma, generated by an excited source at 250 kHz with an electrical power of 400 W, comes to flush the internal surface of the container by bringing the carbon-silica mixture of

coating. Ten seconds is enough to obtain a 250 A coating.

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AVANTAGES DU PROCEDE SELON L'INVENTION

a possibilité d'utiliser pour le substrat un matériau moins coûteux que le PET, du polypropylène par exemple ; . possibilité de choisir pour le revêtement un mélange de matériaux optimal vis-à-vis du compromis souplesse - propriétés barrières ; . le dépôt est mince et déformable : les propriétés barrières sont maintenues même après utilisation poussée du conteneur.

ADVANTAGES OF THE PROCESS ACCORDING TO THE INVENTION

has the possibility of using for the substrate a less expensive material than PET, polypropylene for example; . possibility of choosing an optimal mix of materials for the coating with regard to the flexibility - barrier properties compromise; . the deposit is thin and deformable: the barrier properties are maintained even after extensive use of the container.

Claims (5)

 1) Process for the manufacture of plastic containers including, after the container has been shaped, the deposition on the internal surface of a coating having barrier properties to diffusion, said process being carried out by plasma assistance under a pressure close to atmospheric pressure characterized in that said coating has a thickness of between 150 and 1500 Å and comprises a material or a mixture of materials belonging to the following group: amorphous carbon, hydrogenated or not, nitrogenous or not, oxides, nitrides or carbides or their mixture or combination of one or more of the following metals (Si, Mg, AI, Ti, Zr, Nb, Ta, Mo, W, V). 2) Method according to claim 1 wherein the coating is a mixture comprising carbon with a polymer tendency and silicon oxide. 3) Method according to claim 2 wherein the coating deposited is very rich in carbon in the vicinity of the substrate and very rich in silicon oxide on the surface, the concentration of the respective elements varying continuously between these extreme points of the coating 4) A method according to any one of claims 1 to 3 wherein the container material is a thermoplastic such as a polyolefin, typically polyethylene or polypropylene, or a polyester, typically PET or PEN. 5) container capable of being obtained by the process according to any one of claims 1 to 4, characterized in that it is made of polypropylene and that its internal surface is covered with a coating whose thickness is between 150 and 1500 Â and which includes a material or mixture <Desc / Clms Page number 12>  of materials belonging to the following group: amorphous carbon, hydrogenated or not, nitrogenous or not, oxides, nitrides or carbides or their mixture or combination of one or more of the following metals (Si, Mg, AL Ti, Zr, Nb, Ta , Mo, W, V)