WO1999067327A1

WO1999067327A1 - Electroconductive thermoplastic mixture for the preparation of pipings, systems in conduits, heating means and similar articles

Info

Publication number: WO1999067327A1
Application number: PCT/IT1998/000177
Authority: WO
Inventors: Antonello Rietti
Original assignee: Antonello Rietti
Priority date: 1998-06-25
Filing date: 1998-06-25
Publication date: 1999-12-29

Abstract

The electroconductive thermoplastic mixture according to the present invention may be used for the realization of pipings, systems in conduit, heating means and consists in PVC in suspension, stabilized with lead compounds with the addition of calcium stearate and of diottilphtalate and of electroconductive carbon black, in a percentage of minimum 5 % to a maximum of about 21 %.

Description

ELECTROCONDUCTIVE THERMOPLASΗC MIXTURE FOR THE PREPARATION OF PIPINGS, SYSTEMS IN CONDUITS, HEATING MEANS AND SIMILAR ARTICLES

The present invention concerns an electroconductive thermoplastic mixture for the realization of pipings, systems in conduits, heating means and similar, provided with a relatively high electric conductivity and in any case such as absolutely not to cause electrostatic charges which in turn might cause discharges and explosions in presence of possible gas/combustible and air mixtures.

It is known that for safety reasons the gas pipings for the detailed low pressure gas distribution near the buildings are out of steel, while in many cases - according to the Italian and European laws in force - the connections with the main pipings are performed also with plastic material pipes.

But it is also known that steel as well as most of the metal materials have a low resistance to corrosion and need a suitable protection against the chemical agents in the air, caused by wandering currents.

The mechanical protection systems of known kind, like bundles of organic and inorganic fibres or bands, soaked with a usually bituminous mixture, and the electric sy- stems (cathode protections), are very expensive and scarcely effective and of poor reliability in time.

On the other hand, the coating with extruded plastic materials at present does not solve the problem of the connection points, where most often the corrosion is stressed.

The most oftenly applied solution is the one of making use of an outer protection pipe out of plastic material.

Infact, it is well known that plastic pipings assure a considerable lasting even in presence of strong chemical assault and are totally indifferent to wandering currents due to their feature of extremely low electric conductivity.

Just this latter feature may be dangerous: infact, a material with extremely high dielectric features (volume resistivity) 10/1 5=10/18 ohm/cnr' and su rface resistance 10/10=10/14 ohm/cm , especially if in free air, gets charged with static electricity up to very high values and such as to cause a considerable electric discharge.

Furthermore, between the metal pipe and the sheath, a gas pocket may be situated accumulated in time due to small losses and obviously mixed with air; in this case, the consequences of the discharge can be imagined and are however disastrous.

It is the aim of the present invention to solve all above mentioned inconveniences by means of an electroconductive thermoplastic mixture which does not allow - once it has been used for the realization of pipings and other derived products - the forming of electrostatic charges, as in the meantime it has a specific resistivity of sufficient value and such, as absolutely not to determine electrolytic corrosions, even in presence of the highest wandering currents.

A further feature of the mixture according to the present invention consists of a totale inertia of the chemical aggressive agents in the outer surroundings of the pipe (ground and atmosphere) as well as in the inner room (e.g. hydrocarbon condensation), and furthermore of a total combinatorial non reaction with the many usual or casual components of the different soils.

The present invention will be described more in detail hereinbelow relating to some possible embodiments.

An electroconductive thermoplastic mixture according to the present invention for realizing pipings, systems in conduits, heating means and similar comprises, for each 100 kg of PVC polyvinyl chloride in suspension PK 68, the following components, according to possible variations expressed in kg:

- lead stabilizers (tribasic sulphate, bibsic phosphite, bibasic stereate, neutral stereate) from 2 kg to 8 kg

- calcium stereate from 0,1 kg to 0,5 kg

- diottilphtalate (DOP) from 0,1 kg to 1 ,5 kg

- electroconductive carbon black from 5 kg to 30 kg

In a preferred realization of the present invention, on 100 kg of mixture the following minimum and maximum percentages of the components may be used:

minumum % maximum %

- PVC suspension PK 68 76,3 90,4

- lead stabilizers 2,3 3,8

- calcium stearate 0,09 0,3

- diottilphtalate (DOP) 0 0,6 with the addition of electroconductive black carbon from a maximum percentage of 21 ,3 to a minimum percentage of 4,9.

The products obtained with the mixture according to the present inventions show a plurality of possible applications: - in the plant engeneering field, for the distribution of gas in hospitale and research centres;

- in the methanizing in conduits;

- in the heat transport for teleheating and cooling;

- in the conventional plant engeneering;

- in the industry in general and in detail in the food industry, where the pipings must convey fat substabces which need a temperature control like in the sheathed pipes;

- in the methane systems, in the production workshops where sparks from engines and from welding systems may be freed, and where the need of heating the rooms exists;

- in the realization of methane pipe-lines, waterworks and electroducts, where the need rises to cross channels andrivers so as to avoid the realization of goose necks which need unceasingly highly expensive servicing;

- in the thermic control of the ground, e.g. for the airport strips, where there is the danger of winter frost, making the use thereof safe in any atmosphere condition;

- in all those fields where it is requested to control the temperature of fluids, in warm as well as in cold conditions;

- in all those cases where the availability is requested in spite of the installation in conduits, due to the conduc- tivity of the mixture, by means of devices like metal detectors, like e.g. with the addition, by extrusion, of a strip of conductive mixture onto the polyethylene pipes in waterworks, methane pipe-lines and similar;

- in the surface applications on pipings in general out of copper, iron, aluminium and plastic, as cathode protections;

- in the surface applications on storing containers of combustible material in general to be put underground for the natural earthing of the manufacture;

- in the realization of round, square and rectangular shapes, full and hollow, in all those fields in which cathode protections and surface conductivity are requested;

- in all civil and industrial applications, for sealing gaskets, where the need exists not to interrupt the conductivity of said pipings;

- in all those fields where there is the need of discharging all electromagnetic and electrostatic waves, comprising the earthing of the wandering currents which are formed on the vehicles;

- in the applications on the bottom of shoes, for discharging static electricity.

Claims

1. An electroconductive thermoplastic mixture for the realization of pipings, systems in conduits, heating means and similar, characterized in the following components for each 100 kg of PVC polyvinyl chloride in suspension PK 68, expressed in kg: