DE2455780A1 - Difficulty combustible cables - with PVC compsn. sheath and polyethylene insulated core conductors - Google Patents

Abstract

In a difficulty combustible cable consisting of plastic insulated core conductors and a plastic sheath, of improved electrical properties and/or smaller dimensions, the core conductor insulation consists of a material of low dielectric constant such as polyethylene, foamed polyethylene or polypropylene, while the cable sheath consists of a mixture contg. PVC which has an oxygen index rising from 32 with decreasing weight ratio of sheath material to core conductor insulating material, and pref. when this weight ratio is =3.0:1 the oxygen index of the sheathe material is >=32, while if the ratio is =1.5:1, the oxygen index is >=35. The cable while retaining its non-flammable properties has much improved electrical properties making is partic. suitable for high duty telephone cables.

Description

Flame retardant shift cable with improved electrical properties the Application relates to a flame-retardant switching cable, consisting of plastic-insulated . Cores and plastic sheath, with improved electrical properties and / or smaller dimensions.

Switch cables have the task of being electrical and / or electronic Devices or apparatus, for example in telephone exchanges, on relatively short Connect distances. They are mostly installed in closed rooms and there are therefore high requirements because of the consequential damage that occurs in the event of a fire placed on the flame retardancy of switching cables.

In the case of the known shift cables, this condition is their cable core consists of cores insulated with polyvinyl chloride (PVC) and with a PVC cable sheath is provided, largely fulfilled.

For this, however, the known shift cables have disadvantages, which because of the increasing use of electronic circuits in the aforementioned Devices in question.

For example, the known shift cables have such values Operating capacity or 7wischenaderkapacity that the electronic circuits are influenced in the connected devices in a way that is no longer permissible can.

The task on which the application is based is to create a switching cable indicate which is much better compared to the known shift cables electrical properties or lower if the electrical properties are the same Dimensions. The characteristic of the fire behavior of the well-known Sehaitkabel Properties of the new gearshift cable should be at least the same or even be better quality.

According to the invention, this object is achieved in that the insulation the cores made of a material with a low dielectric constant, such as polyethylene (PE), foamed polyethylene or polypropylene (PP) and the cable jacket from one Polyvinyl chloride containing mixture, which with decreasing weight ratio Sheathing material / core insulation material has an increasing oxygen index starting at 37 possesses, further advantageous features of the invention are in the claims 2 to 4 and are explained in more detail below.

The new shift cable has a cable core, the individual wires with PE, foamed PE or PP are insulated and provided with a cable jacket made of PVC, depending on the weight ratio of PVG of the cable jacket to the insulating material the core has a certain oxygen index per unit length of the cable.

The oxygen index according to Fenimore and Zarten is used as a measure of the Flammability of a substance is used, whereby the incombustibility is the greater or the higher the oxygen index, the lower the flammability. After this known test methods are slowly burning substances by means of an oxygen index between 22 and 27 and self-extinguishing substances through an oxygen index 27 characterizing'-.

In the practical implementation of the new switching cable with PVC cable sheath and PE-insulated wires have shown that the desired flame retardancy It is essential if the conditions given in the table below are met are: Weight ratio oxygen index (O2 index) PVC: PE des Sheath PVC # 3.0: 1 # 32 # 1.5: 1 # 35 These oxygen indices can be calculated according to achieve the further invention by a mixture of the cable jacket, which consists from: 100 parts by weight PVC 40-60 "" diisodecyl phthalate 5-15 "" chlorinated paraffin 3 - 10 "" antimony trioxide 5 - 30 "" zinc borate The new shift cable has a Resistance to ignition that is equal to or better than that of the well-known FVC shift cables. The comparable or even improved fire behavior was determined by a bundle test judged. With this jacket material was also used for the specified weight ratios (PVC) for core insulation material, the limit values in the oxygen index of the PVC sheath determined However, the operating capacity of the new cable is about 50% less and it also has about 25% less attenuation.

If, in certain applications, the electrical properties of the new shift cable are of no importance, you can use instead Applying the teaching given, the dimensions of the cable can be reduced.

Claims (4)

Expectations 1. Flame-resistant switching cable, consisting of plastic-insulated Cores and plastic sheath, with improved electrical properties and / or smaller dimensions, characterized in that the insulation of the wires from one Material with a low dielectric constant, such as polyethylene, foamed polyethylene or polypropylene and the cable jacket from a mixture containing polyvinyl chloride consists, which with decreasing weight ratio of sheath material / core insulation material Has an increasing oxygen index starting at 32. 2. Shift cable according to claim 1, characterized in that at one Weight ratio of sheath material / core insulation material of # 3.0: 1 of the oxygen index of the sheath material is # 32. 3. Shift cable according to claim 1, characterized in that at one Weight ratio of sheath material / core insulation material of C 1.5 1 the oxygen index of the sheath material is> 35. 4. Shift cable according to claim 1 and one of claims 2 or 3, characterized in that the jacket material consists of. a mixture, which to 100 parts by weight of polyvinyl chloride 40-60 parts by weight of diisodecyl phthalate, 5 - 15 parts by weight of chlorinated paraffin, 3 - 10 parts by weight of antimony trioxide and 5 - 30 parts by weight Contains parts of zinc borate.