FR2461340A1 - CELL INSULATING ELECTRIC CABLE AND PROCESS FOR PREPARING THE SAME - Google Patents

Abstract

ELECTRIC CABLE WITH CELLULAR INSULATION FORMING AT THE SAME TIME SEALING SHEATH. THE INSULATION CONSISTS OF EXPANDED POLYVINYL CHLORIDE UP TO A VOLUME PERCENTAGE OF CLOSED PORES OF 20 TO 40 BY ADDITION OF VERY FINE GRAINS OF A DECOMPOSITION POINT CHEMICAL EXPANSION AGENT BETWEEN 180 AND 200C . APPLICATION TO LOW OR MEDIUM VOLTAGE CABLES.

Description

2 46 13 4 0

  The present invention relates to an electric cable for low or medium

  voltage, cell insulator forming at the same time sealing sheath.

  Polyelectrically insulated electrical cables are already known

  thylène. This is however a relatively high density material and quite expensive. Solid poly-chloride insulated cables have already been used

  compact vinyl, less dense material and less expensive than polyethylene.

  However, cell polyvinyl chloride insulation has not been achieved so far, since plasticizers and fillers have to be added to allow its use in cabling, and so far the testing of conductive coatings. by polyvinyl chloride cellular gave only cables of very irregular thickness, unsatisfactory

for industrial use.

  It is an object of the present invention to provide an electrically insulating cellular cable, which at the same time forms a sealing sheath made of polyvinyl chloride, which has a uniform thickness, an expansion of the insulation which is not excessive, a fine structure and a fairly superficial appearance

  smooth, allowing its application in industrial manufacture.

  The electrical cable according to the invention is characterized in that its insulation consists of expanded polyvinyl chloride up to a percentage of closed pores of about 20 to 40%, by the addition of very fine grains of a polyvinyl chloride. chemical expansion of decomposition point included

between 1800 and 2000C approximately.

  It further preferably responds to at least one of the following features:

  - The chemical expansion agent is azodicarbonamide.

  - The chemical expansion agent is in grains of medium size

about 10 microns.

  - The chemical expansion agent is in a proportion by weight of 0.05

at 0.5% by weight.

  Polyvinyl chloride is also added with a nucleating agent.

  - The nucleating agent is talc in fine grains.

  - The fine-grain talc is in a proportion of about 0.5% by weight.

  The invention also relates to a method of manufacturing an electric cable as defined above, characterized in that it is passed through an extruder whose temperature of the head is maintained between 1600 and 1800C, a part by the punch an electrical conductor, on the other hand by the peripheral matrix of the polyvinyl chloride added with very fine grains of a decomposition point chemical expansion agent

from about 1800 to 2000C.

2 2 62461340

  The following is an example of the manufacture of polyvinyl chloride insulating low-voltage electrical cables according to the invention and their properties as a function of the materials used and the

operating conditions.

  A 0.9 mm diameter copper wire was used which was sheathed with plasticized polyvinyl chloride sold under the trade designation "Benvic KI 80/100", supplemented with an azodicarbonamide swelling agent. ,

  and in some cases talc acting as a nucleating agent.

  The blowing agent was added to the polyvinyl chloride by kneaded coating (with addition of about 0.5 wt% wetting agent). It was used either the product sold under the commercial designation "Celogen AZ" by the Chevassus Company, or that sold under the commercial designation "AZB" by the French Society of Organo-Synthesis. The application head of the polyvinyl chloride was a discharge screw of the plastic of a conventional type, used in particular for polyethylene, with a filter formed by a 30/60/120/60 sieve, a punch of diameter 0.92 mm and a die diameter 2.2 mm. The speed of the discharge screw was 68 rpm, and the pulling speed was 50 m / min. For some of the tests, the

copper was preheated.

  The table below summarizes the test results.

  Sealing electric cables with cellular vinyl polyvinyl chloride

  Wire Lead Probe (d C) Extruder Temp (d C) Input Wired Output HF 192 Cable Temperature at Output d C Die Distance to Cooling Tray. (mm) Results diamltredensite il I

rate -

dtexpan-

if we

_... .....

FLOWING AGENT "CELOGEN AZ"

        not

1200 I

    he ll, sr If nnn 192 n II tl he n IV l7 I, he n he he he lt he n he n he nr 2,2 3,07 2,735 2,625 2,53 2,575 2,28 2,28 1 , 38 0, 7 0.83 0.85 0.93 0.9 1.14 1.07 O Observations Expansion too strong cooling too brutal Expansion too strong insulation very loose quite good result, very important fumes

Strong expansion cold

too brutal

Expansion too strong-

  rough appearance Aspect a little better aue in the test 6 Good result, rather fine structure / aspeet a little rough t Very good result, rather fine structure. Smooth and shiny appearance as test 10. But structure a little less fine..b 0- o> N test content of blowing agent (% wt) o o 0, 5 I 0.3 0.1

0, 1% + 0.5%

talc n He he

AZB INFLATOR

  II II II Il II II 1500 i 160 (ventilation) 1500 to 1600 (ventilation) ti ventil. 2.63 2.63 2.69 2.32 2.47 2.4 0, 86 0.85 0.82 1.18 1.1 1.0 1, 02 Good result, very fine structure, expansion a little strong id id

Excellent result, structure

  very fine. Smooth and glossy appearance but more expansive structure near the driver

Very fine structure.

  Very smooth appearance despite fairly high expansion

Excellent structural results

  very fine. Very smooth appearance 0.1% it te 0, o6% i, It -

2 4613 40

  Although the electrical cable and the method of preparation which have been described with reference to the examples appear the preferable embodiments of the invention, it will be understood that various modifications can be made without departing from the scope of the invention. In particular, certain additives not detrimental to the controlled expansion of polyvinyl chloride can be added, and the extrusion conditions can be

  modified to some extent under the same reservation.

  The invention applies in particular to the insulation of cables and

  electrical conductors for low voltage.

6 2461340

Claims (6)

  1 / electric cable for low or medium voltage, with cellular insulation forming at the same time sealing sheath, characterized in that said insulator is constituted by poly-vinyl chloride expanded to a percentage by volume of closed pores of 20 at about 40%, by adding very fine grains of a chemical expansion agent of decomposition point between 1800 and 2000C approximately.   2 / electric cable according to claim 1, characterized in that the agent   Chemical expansion is azodicarbonamide.   3 / electric cable according to claims 1 or 2, characterized in that   the chemical expansion agent is in grains of average size about 10 microns.   4 / electric cable according to one of claims 1 to 3, characterized in   that the chemical expansion agent is in a weight ratio of 0.05 at 0.5% by weight.   Electrical cable according to one of claims 1 to 4, characterized   the polyvinyl chloride is also added with a nucleating agent. 6 / electric cable according to claim 6, characterized in that the agent   nucleation is talc in fine grains.   7 / electric cable according to claim 7, characterized in that the talc   in fine grains is in a proportion of about 0.5% by weight.   8 / A method of manufacturing an electric cable according to claim 1, characterized in that it is passed through an extruder whose temperature of the head is maintained between 1600 and 1801C, on the one hand by the punch   an electrical conductor, on the other hand by the peripheral matrix of the poly-   vinyl chloride with very fine grains of an expanding agent   chemical decomposition point of about 1800 to 2000C.