FR2499324A1 - APPARATUS AND METHOD FOR PROCESSING A PLASTIC FILM WITH CORONA EFFECT - Google Patents

Abstract

THE INVENTION RELATES TO AN APPARATUS AND A PROCESS FOR TREATMENT OF A PLASTIC MATERIAL FILM BY THE CORONA EFFECT. IN THIS APPLIANCE, THE EARTHED TREATMENT ROLLER CONSISTS OF TWO CONCENTRIC CYLINDERS 1, 4 ELECTRICALLY CONDUCTIVE. A DIELECTRIC MATERIAL FILLS THE GAP 6 SEPARATING THE INTERNAL 1 AND EXTERNAL CYLINDERS 4. APPLICATION TO THE IMPROVEMENT OF THE SURFACE ADHESION OF PLASTIC MATERIALS.

Description

The present invention relates to an improved drum or roll

  supporting a plastic film, and the use of this roll during the electrical treatment of this film, that is to say during the corona treatment (scent) of plastic films to improve the adhesion of inks, adhesives

  or substances similar to the surface of these films.

  The conventional drum or roll of support

  in such treatment consists of an electrically conductive cylinder mounted on a concentric shaft and having an uninterrupted coating of material

  electrically insulating on its outer surface, which ensures

  re effective contact with the plastic film

  supported by said roll during its treatment. How-

  However, none of the insulating coatings used for this purpose have been found to be fully satisfactory, since glass and refractory ceramic products are very expensive and subject to crack formation and flaking because of their intrinsic fragility. while most polymer-based coatings are

  deteriorate rapidly in the discharge environment of ef-

  fluids, particularly as a result of the effects of heat and ozone and other corrosive vapors generated during such discharges, and also because of the

  abrasive of the treated plastic film.

  It is therefore an object of the present invention to provide an improved processing roll, which can operate considerably longer before it is necessary to replace the material

electrically insulating.

  The invention also aims to propose a procedure

  economic de treatment of a film of plastic material

  that in order to improve the surface tension of the latter.

  The drum or roll of support according to the present

  the invention comprises an electrically conductive outer cylinder which supports the plastic film; an electrically conductive inner cylinder mounted on a central shaft in the concentric alignment of said outer cylinder, from which it is spaced; as well as a dielectric layer in the gap between said

internal and external cylinders.

  The invention will now be described more in

  detail with reference to the annexed drawing as an example

  FIG. 1 is a partial longitudinal section of a suitable embodiment of a treatment roller; and FIG. 2 is a perspective view illustrating the use of this roller during the effect treatment.

  corona of a plastic film.

  In FIG. 1, which illustrates one of the end zones of the treatment roller, there is an internal electrically conductive cylinder 1 made of any suitable metal which does not necessarily have to withstand corrosion since the cylinder 'is

  not exposed to a discharge environment.

  For reasons of low cost and lightening, it is necessary to

  will preferably read aluminum to make this cylinder. The thickness of the cylinder 1 may be from about 6.35 mm to about 25.4 mm. This cylinder is suitably wedged onto shaft ends 2 according to the arrangement illustrated in FIG. 1, although many other types of mounting are also possible. In the illustrated embodiment,

  each end of the cylinder 1 is subject, for example

  in a cylindrical block 3 made of an electrically conductive metal, for example aluminum or any other metal

  used to make the cylinder 1. The blocks 3

  the structural stability of the roller and precise alignment with the central shaft on which these blocks are

  mounted, advantageously fitted by withdrawal.

  An outer cylinder 4, located at a distance from the inner cylinder 1, is made of an electrically conductive material and resistant to corrosion, such as

  stainless steel or other suitable alloy steels.

  The thickness of the outer cylinder can be from about 6.35 mm to about 19.05 mm. An interval 6 between the inner and outer cylinders 4 is filled as much as possible by an electrically insulating material having a dielectric constant and a dielectric strength sufficiently high to withstand the strong

  potentials required for corona treatment. The bus-

  between the inner and outer cylinders, which corresponds to the thickness of the dielectric material, is maintained between 0.76 mm and approximately 3.8 mm, preferably

  between about 2.03 mm and about 3.17 mm.

  Insulating extreme caps 7, subject

  to blocks 3 by screws 8 (two out of the eight used

  are shown in Figure 1), serve to protect

  manage the internal space of the roll of the corrosive influence exerted by the ozone, and to support the central shaft without causing electric short-circuits. Teflon is a suitable material for making corks

  extremes, although many other

  lants whose structural rigidity is sufficient

  can be used for this purpose with the same efficiency.

  you. At each of its ends, the outer cylinder 4 is fixed to the insulating plugs 7 by means of screws 9 (of which

  two of the eight used are illustrated in the figure

re 1).

  Among the appropriate subjects presenting the

4 -

  dielectric characteristics required to form the insulating layer placed in the gap 6 (see

  above), epoxy resins, coaxial

  fiberglass and epoxy resin, Hypalon, Teflon, polyester, silicone rubber (raw or

  treated) and silicon-based substances

  cate or ceramic. The dielectric constants of these

  insulating materials are typically between

  2.5 and about 5 and their dielectric strength

  The scale is from about 10 kV / mm to about 20 kV / mm. The insulation can be obtained by different

  processes according to the nature of the dielectric material

  than. For example, powdery substances can be

  inorganic slow in the meantime after the

  Killing of the treatment roller were assembled. Similarly,

  viscous fluids can be poured or injected into this

  interval after assembly is complete. Alternatively, prefabricated sleeves made of dielectric insulation may be placed on the inner cylinder before being placed on the outer cylinder. In a similar manner, substances to be sprayed or brushed onto a surface before curing are applied

  over the entire outer surface of the inner cylinder. Coatings

  epoxy resin reinforced with glass fibers are advantageously applied by first winding a

  glass filament on the inner cylinder and then sprayed

  risking the epoxy resin to fill the gaps between

the turns.

  Whatever the method used to set up the insulating layer in the interval 6, it is advisable to avoid as much as possible trapping air in this layer, or problems of arcing occur at places where the amount of dielectric material is insufficient. Therefore, care must be taken to avoid the formation of air bubbles under the coating sleeves and in sprayed and brushed coatings. A preferred method for placing the outer cylinder 4 on the inner cylinder coated with the insulating layer is the shrink-fit method, which reduces the risk of entrapment of air between said layer and said outer cylinder. When the insulating layer is made of hard material such as a

  epoxy resin, reinforced with glass or not, it is

  tageux grinding in addition to the surface of this layer

  to a smooth finish after it has been applied

  on the inner cylinder. After assembly, the surface of the outer cylinder 4 is preferably ground

  to obtain a finish as smooth as possible.

  Figure 2 illustrates the use of the roller of Figure 1 for corona plastic film processing. This film 10, guided by

  idle cylinders 11 and 12, passes on the treatment roller.

  which is grounded by a grounding conductor 13 connected to the shaft 2. The reference 14 designates an electrode connected to a source of electrical energy

  appropriate, high frequency and high potential.

  The electrode is spaced from the treatment roller, parallel to

  parallel to the axis of the latter, o o results in the formation of a uniform gap between the electrode and the film passing on the roller. The spacing is usually kept below about 6.35 mm and preferably from about 0.5 mm to about 1.52 mm. It is recommended to maintain the potential between the electrode and the treatment roller between about 3000 V and about 30 000 V, and the treatment is typically performed at a frequency

  from about 0.6 kHz to about 25 kHz.

  In a specific exemplary embodiment of a treatment roller shown essentially in Figures 1 and 2, the overall length of this roll is about 165 cm and its outer diameter is about 16.5 cm. The wall thickness of the cylinder 1, made of aluminum, is about 3.17 mm. The thickness of the insulating layer (fiberglass reinforced epoxy resin) completely filling the gap 6 is about 2.54 mm and the thickness of the outer cylinder 4 made of steel

stainless is about 3.17 mm.

  Many plastics constituting the film can be corona treated according to

  to the invention, among which mention will be made of polyole-

  such as polyethylenes, polypropylenes, polybutene-1 and copolymers based on two or more olefins having from 2 to 8 carbon atoms. Other plastics constituting the film include polystyrene, polyvinyl chloride, copolymers of vinyl chloride, polyamides and other materials. It is obvious that the terms "plastics" and "polymer" used herein include homopolymers, copolymers,

  terpolymers, laminates of block copolymers

  and similar materials. The thickness of the film is now

  typically held between about 2.54 / 5wn and about 508, wm. The advantages provided by the invention are numerous. Incidents due to combustion and roller failures are significantly reduced and the speeds of the processing chain can be increased without raising any difficulties due to

  greater power needed.

  It goes without saying that many modifications can be made to the apparatus and the process

  described and shown, without departing from the scope of the invention.

Claims (5)

  1. Apparatus for processing a film of matter   corona effect, characterized in that it comprises a treatment roller comprising a   external cylinder <4) electrically conductive and suppor-   both said film (10) of plastics material; an inner cylinder (1) electrically conductive, mounted on a central shaft (2) in the concentric alignment of said outer cylinder (4), from which it is spaced; as well as a dielectric material placed in the gap (6) between   internal (1) and outer (4) cylinders.   2. Apparatus according to claim 1, characterized   rised by the fact that the thickness of the dielectric material   that is between about 0.76 mm and about 3.8 mm.   3. Apparatus according to claim 1, characterized   because the dielectric constant of the material   dielectric res is between 2.5 and about 1 the dielectric strength of this material being   from about 10 kV / mm to about 20 kV / mm.   4. Apparatus according to claim 1, characterized   in that the treatment roller is provided with   insulating end plugs (7) at each end.   5. A method of producing a plastic film whose surface adhesion is improved with respect to substances applied thereto, by   to pass said film in an environment of ef-   fluve, characterized in that said emanations are discharged between an electrode and the   treatment roller put to the masseson the claim- 1.