FR2815164A1 - FLAT CABLE AND MANUFACTURING METHOD THEREOF - Google Patents

Abstract

The invention relates to a method of manufacturing a flat cable, characterized in that: - two polyester insulating cables are produced by extrusion-coating and drawing, - at least one side of each of the cables is treated by depositing therein an acid solution containing a dispersion of solid particles so as to obtain, after drying, a surface tension of between 50 and 60 dynes, - the treated face is then coated with a layer of adhesive, - the conductors are placed longitudinal between the respective coated faces of the two insulating wires, then the two wires are plate and secured against each other by trapping said conductors.

Description

The present invention relates to a flat cable and a

  method of manufacturing such a cable.

  Flat cables generally include longitudinal conductors trapped between two insulating films secured by layers of adhesive. These insulating films are generally made of polyester and

  for example polyethylene terephthalate (PET).

  However, these cables have a strong tendency to delamination, in particular under critical temperature and humidity conditions due to the weakness of the connection between the insulating filhns.

and adhesive layers.

  The object of the present invention is to solve this problem

  technically satisfactorily.

  This object is achieved, in accordance with the invention, by means of a process for manufacturing a flat cable, characterized in that: - two insulating polyester films are produced, by extrusion-coating, and drawing, - one treats at least one face of each of the films by depositing an acid solution containing a dispersion of solid particles therein so as to obtain, after drying, a surface tension of between 50 and 60 dynes, the coating of the face treated with tune is then carried out adhesive layer, - there are longitudinal conductors between the respective coated faces of the two insulating films, then - the two films are pressed and joined together against

imprisoning said conductors.

  According to an advantageous characteristic, said particles

  solids have a specific surface between 50 and 380 mn2 / g.

  According to another characteristic, the quantity of solid particles remaining attached to the film after treatment is included

between 0.01 and 0.80 g / m2.

  According to a specific mode of implementation, the acid solution contains trichloroacetic acid and the solid particles are

consisting of fumed silica.

  Another object of the invention is a flat cable of the type comprising longitudinal conductors trapped between two insulating films secured by layers of adhesive, characterized in that

  that the cable has a peel strength of between 2 and 3 N / mm.

  According to a specific embodiment, the adhesive is a mixture comprising from 70 to 90% by weight of polyester resin and from 10 to 30% by weight of epoxy resin, and capable of polymerizing under the action of my agent. crosslinking

based on polyisocyanate.

  Preferably, the polyester resin has a group content

  hydroxyls between 0.100 and 0.200 mol / kg.

  Alternatively, the polyester resin has a temperature

  glass transition less than 20 C.

  According to another variant, the epoxy resin is a bisphenol epoxy resin having a content of hydroxyl groups

between 2.4 and 2.6 mol / kg.

  The glass transition temperature of this epoxy resin

  is preferably between 30 C and 50 C.

  Preferably, the crosslinking agent consists of

  - 2 to 5% by weight relative to the total weight of toluene resin di-

  isocyanate. This resin preferably contains between 17 and 20% of

NCO group.

  According to yet another variant, the adhesive comprises, in

  in addition, fireproof fillers and / or coloring fillers.

  The flame retardant fillers consist, for example, of brominated derivatives, of chlorinated paraffin, of antimony oxide (Sb203) of zinc borate, of alumina trihydrate (A1OH3), of hydroxide.

  magnesium (MgOH2), polyphosphates and phosphorus derivatives.

  The coloring charges are, for example, made up of

titanium dioxide (TiO2).

  According to another characteristic, the internal face of the insulating cables is coated with fumed silica particles in an amount

between 0.01 and 0.80 g / m2.

  The method of the invention allows to considerably strengthen the connections, on the one hand, between the adhesive layers and the conductors and, on the other hand, between said layers and the insulating films. This improvement in adhesion is mainly due to the combined factors of the incorporation of the epoxy resin into the polyester matrix and the increase in reactive sites on the surface.

insulating films.

  As a result, the flat cable obtained by this process has very good mechanical properties and, in particular, a very high peel or delamination resistance. In addition, the adhesive layer has a better

  chemical resistance to oxidative degradation phenomena.

  Thus, the properties of the cable are preserved in the

  time even under very severe storage and use conditions.

  The invention will be better understood on reading the examples

following comparisons.

  First, a test tube of the cable of the invention is produced in the form of a flexible flat cable (FFC) having the following characteristics: a) longitudinal conductors of bare copper of 0.70 x 0.05 mrn pitch: 2.67 + 0.20 min thickness: 0.21 + 0.04 min width: 7.74 + 0.20 mmn b) PET insulating films of 50 μm treated according to the process of the invention with solid particles, the specific surface is 80 + 20 g / m2 and a residual quantity of solid particles on the film after treatment of between 0.2 and 1.0 g / m2 c) Adhesive formulation under the form of a mixture of the following resins: Proportions ( %) Temperature of glass transition group content (C) hydroxylated (mol / kg) Polyester resin 75 10 0.168 linear saturated Epoxy resin 25 35 2,400 bisphenol A type The measurement of the delamination resistance is then applied to three different test pieces, of which l only one was

  produced according to the method of the invention.

  One end of each test piece is provided between the two insulating films with a rupture initiator in the form of a Kapton polyinide adhesive tape (registered trademark). Then each test piece is fixed to an aluminum plate using a double-sided adhesive tape (468 MP tape from 3M). The very high resistance to tearing of this adhesive makes it possible to exert traction on the insulating film without conductor at a flat angle of 180 with a speed of 25 min / in under normal temperature conditions. The force required to obtain a peeling effect at the PET film / adhesive layer interface is measured as soon as a value is established

  constant of this force and corresponds to the resistance to delamination.

Results

  CHARACTERISTICS CHARACTERISTICS RESISTANCE TO

DELAMINATION (N / MM)

UNDER CONDITIONS

  INSULATING FILM ADHESIVE LAYER (1) * (2) *

  50 min PET film - resin mixture treated with saturated polyester discharge 1.70 2.20

  CORONA on the - thermnno- hardener

  glued side activatable - resin mixture PET film untreated saturated polyester of 50 nm - hardener 2.20 2.55 isocyanate - mixture of 75% PET film of 50 ipm saturated polyester resin treated according to and 25% resin 2, 80 2.95 l epoxy invention -2.2% isocyanate hardener (TDI) * (1) at ambient temperature and humidity (2) after baking the cable for 168 hours at 40 C and rate

99% humidity.

Claims (12)

  1. A method of manufacturing a flat cable, characterized in that: - two insulating polyester films are produced by extrusion-coating and drawing, - at least one side of each of the films is treated by depositing an acid solution therein containing a dispersion of solid particles so as to obtain, after drying, a surface tension of between 50 and 60 dynes, - the coating of the treated surface is then carried out with a layer of adhesive, - there are longitudinal conductors between the respective coated faces of the two insulating films, then - the two films are plated and joined together against each other in imprisoning said conductors.   2. Method according to claim 1, characterized in that said solid particles have a specific surface of between 50 and 380 m2 / g.   3. Method according to one of the preceding claims,   characterized in that the dispersion of solid particles is such that the quantity of solid particles remaining attached to the film after   treatment is between 0.01 and 0.80 g / m2.   4. Method according to one of the preceding claims,   characterized in that the acid solution contains trichloro acid   acetic and the solid particles consist of fumed silica.   5. Method according to claim 4, characterized in that the internal face of the insulating films is coated with silica particles   pyrogenated in an amount between 0.01 and 0.80 g / m2.   6. Method according to one of the preceding claims,   characterized in that the adhesive is a mixture comprising from 70 to 90% by weight of polyester resin and from 10 to 30% by weight of epoxy resin, and capable of polymerizing under the action of a crosslinking agent to polyisocyanate base.   7. Method according to claim 6, characterized in that the polyester resin has a content of hydroxyl groups between 0.100 and 0.200 mol / kg.   8. Method according to claim 6 or 7, characterized in that the polyester resin has a glass transition temperature below C.   9. Method according to one of claims 6 to 8, characterized in   what the epoxy resin is a bisphenol epoxy resin having a   content of hydroxyl groups between 2.4 and 2.6 mol / kg.   10. Method according to one of claims 6 to 9, characterized   in that the crosslinking agent consists of - 2 to 5% by weight per   based on the total weight of toluene di-isocyanate resin.   11. Method according to one of claims 6 to 10, characterized   in that the adhesive further comprises flame retardant fillers and / or coloring charges.   12. Flat cable obtained by the process according to one of the   claims 1 to 11, of the type comprising longitudinal conductors   trapped between two insulating films secured by layers of adhesive, characterized in that the cable has a peel strength between 2 and 3 N / mm.