Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – With means applying electromagnetic wave energy or...
Reexamination Certificate
2000-12-18
2002-10-01
Mayekar, Kishor (Department: 1741)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
With means applying electromagnetic wave energy or...
C422S186300, C422S186040
Reexamination Certificate
active
06458330
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an installation in which an operation is performed that requires control over the atmosphere inside a chamber, and relates in particular to an installation for the surface treatment of a running substrate, particularly a polymer film, more precisely for implementing a method whereby the substrate is subjected to an electrical discharge in a gaseous mixture other than air.
2. Description of Related Art
In particular, it is known that the performance of films (surface energy, adhesion properties, etc.), particularly of polyolefin films, can be improved by depositing a small amount of silicon oxide on their surface. To this end, according to these known methods, the substrate (the film) made of polymer is subjected to an electrical discharge with dielectric barrier at a pressure higher than 10 kPa, and, at the same time or subsequently, the substrate thus treated is exposed to an atmosphere consisting of an active gaseous mixture, the active mixture containing, for example, a gas capable of causing the formation of the silicon oxygen deposit, such as a silane (usually a silicon hydrocarbon which may or may not be halogenated, or an alkoxysilane).
In general, treatment by electrical discharge in a gaseous mixture is performed continuously, at substrate running speeds ranging from about ten to several hundred meters per minute, usually in a chamber containing, in addition to the electrodes, a device for injecting the active gaseous mixture and devices for extracting the gaseous emissions. The discharge is created between the electrodes of the chamber arranged on one side of one of the surfaces of the substrate and a counterelectrode arranged on the side of the opposite surface.
By way of illustration of this state of the art of surface treatments of running polymer films, reference may, for example, be made to document EP-0 622 474.
More specifically, the substrate to be treated is applied against the periphery of a metal roll covered with a dielectric material used as a counterelectrode and grounded, along an arc of a circle of several tens of degrees, for example over half the circumference of the roll. A cap delimiting the chamber covers part of the length of this arc of a circle, approximately centrally, extending far enough away from this arc to be able to contain the various elements necessary for the treatment; the length of the roll in its axial direction is slightly greater than the width of the substrate, and the length of the chamber in the same direction is itself generally slightly greater than the width of the substrate.
Furthermore, on an industrial scale, treatment is often performed constantly 24 hours a day, and the apparatus under the cap has to operate as an open system. In spite of the devices for extracting and injecting the active gaseous mixture, the air entrained as a boundary layer at the surface of the strip cannot be completely prevented from getting under the cap. The treatment is therefore carried out in a gaseous mixture consisting of the active gaseous mixture injected and of air, the proportions of which are poorly controlled.
The active gaseous mixtures employed are generally binary or ternary mixtures consisting of nitrogen by way of carrier gas and of active gases in proportions of the order of a few hundreds of ppm. Work carried out in optimizing the method clearly demonstrates that the level of each of the active gases in the mixture is an essential parameter that needs to be controlled as strictly as possible. Furthermore, certain active gases such as silanes have the property of reacting strongly with air to give byprnducts, particularly solid and gaseous ones.
It is therefore necessary to have use of a treatment installation capable of good control over the treatment gaseous atmosphere, by reducing the amount of incoming air as far as possible.
There are also known (see, for example, the European patent mentioned earlier), installations for implementing such methods comprising injectors for injecting active gaseous mixture right inside the discharge and extraction slits at the inlet and outlet of the chamber. The injection and extraction flow rates are regulated so that the amount of incoming air is minimized. However, minimal air content achieved under the cap remains high by comparison with the content of active gas in the injected mixture. Hence, when the desired treatment level demands that the gaseous mixture contains a very low content of oxidizing gas, uncontrolled addition of a certain amount of air (and therefore oxygen, which is an oxidizing gas) to the gaseous mixture leads to poor control of the quality of the treatment. Control over the composition of the active gaseous mixture may therefore prove insufficient with this type of installation.
The object of the invention is to overcome this drawback and more particularly to provide an improved installation of the aforementioned type (in which an operation is performed that requires control over the atmosphere inside a chamber), and, in the particular case of the surface treatments of running substrates, to propose an installation such that the control and management of the gas are possible both in terms of incoming gases and exiting gases, through the fact that:
the air entrained on the surface of the substrate is prevented from entering the treatment chamber;
the active gaseous mixture is injected into the chamber and thus used optimally for the actual treatment;
any gaseous emissions are collected so that they can be processed before they are rejected to the air.
SUMMARY OF THE INVENTION
To this end, the invention relates first of all to an installation in which an operation is performed that requires control over the atmosphere inside a chamber, the operation being performed in the presence of a gaseous mixture capable of giving off emissions, characterized in that it comprises:
inlet and outlet devices adjoining the chamber to oppose respectively the ingress of air into the chamber and the exit of gaseous emissions therefrom;
an extraction device comprising a duct opening into the chamber; and
means for regulating the flow rate of gas drawn out by said extraction device so as to maintain an approximately zero pressure difference between the inside of the chamber and the surrounding atmosphere.
The expression “approximately zero” according to the present invention is to be understood as meaning a pressure difference (positive or negative) not exceeding a few tens of Pa or even 100 Pa. However, it is preferable according to the present invention to work with pressure differences not exceeding 50 Pa or even differences lower than 10 Pa.
The installation according to the invention may also have one or more of the following features:
the inlet device comprises means for injecting an inert gas forming a gas knife upstream of the chamber, means for creating a raised pressure discharging the inert gas away from the chamber forming a piston preventing air from entering the chamber and means for ducting the air away from the chamber.
the outlet device comprises means for injecting an inert gas forming a gas knife downstream of the chamber, means for creating a raised pressure discharging the inert gas toward the chamber forming a piston opposing the entrainment of emissions out of the chamber, and means for ducting toward the chamber any emissions that may be trying to leave this chamber.
said means for injecting the inert gas forming a gas knife comprise a flat-walled gas-injection slit opening to inside the inlet or outlet device concerned.
said means for creating a raised pressure discharging the gas and forming a piston comprise open grooves facing the interior space of the inlet or outlet device concerned and forming a labyrinth.
said ducting means comprise a passage separated from said gas-injection means by a partition and open facing the interior space of the inlet or outlet device concerned.
said ducting means comprise a passage cut into one face of a plate separated from another part by a space for
Cocolios Panayotis
Coeuret François
Döring Wolfgang
Förster Franck
Gelot Jean-Louis
Burns Doane Swecker & Mathis L.L.P.
L′Air Liquide Societe Anonyme a Directoire et Conseil de S
Mayekar Kishor
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