TECHNICAL FIELD This invention concerns a procedure for extrusion to be used for making composite multi-property tiles and obtained tiles.

BACKGROUND ART As we know, right from the time of antiquity, man has been trying to create floor tiles that are durable, attractive, hygienic and economic. Thus many types of tiles have been produced, including ceramic, artificial marble, cement and artificial stone ones. Many different composites can be used in these types of tiles : Portland cement, white cement, clay, feldspar, quartz, silicofluoride, magnesium cement, dolomite etc. As a result of the many techniques, components and reagents used, tiles are produced with very different characteristics in terms of : appearance, durability, electric conductivity, porosity, weight, resistance to damage, natural radiation and touch. All of these types of tiles have intrinsic characteristics, which make them attractive depending on the personal or architectural context in which they must be evaluated. Just as every song has its own intrinsic beauty,

which cannot be substituted by another harmony, every type of tile has its own appeal, its own intrinsic characteristics, even if its chemical composition is similar to another.

It only takes a few details that appear insignificant, in the production process or in the blend of materials and reagents used, to give them new and surprising properties. So, when defining the properties of a tile we must take into consideration subtle aspects, delicate balances at a sublime level of perception, emotions that cannot be reasonably explained that draw not so much from the sphere of the aesthetically similar as from the complexities of electro-magnetic interference on the biological organism and on its implications on the laws that govern our psychic nature in general. The purpose of this invention is therefore to define a tile that can be made through a skilful and careful blending of natural composites in the true sense of the word, combined in appropriate amounts. Another purpose is to define a tile, as above in which said composites are bound together will methods and means that will create a product that expresses an ideal reconciliation between the properties of hardness, tenacity, porosity, smoothness and lightness.

Another purpose is to define a tile that will dissipate electro-static charges in the environment. Another

purpose is to define a tile that will be able to significantly reduce sound waves. Another purpose is to define a tile with fireproof properties. Another purpose is to define a procedure that makes it possible to produce tiles economically. Another purpose is to define a procedure, as above, that makes it possible to produce very long tiles economically. Another purpose is to define a procedure, as above, that will make tiles with surfaces and/or edges that are shaped according to free, imaginative, aesthetic and/or functional lines. Another purpose is to define a production process that avoids the use of traditional pressing and/or tamping techniques inside specific moulds.

DISCLOSURE OF INVENTION These and other purposes appear to be achieved by the procedure indicated in the main claim and that includes most of the following points. The preliminary phase consists in carefully blending the following composites in the granular or powder state that are present in the following percentages in weight. The technological properties of each are known: their overall formulation, however, is new.

Magnesium oxide varying from 40% to 70%; this percentage is proportionally suitable for giving the finished tile electric conductivity that will dissipate

electro-static charges; silica, or quartz sand, varying from 10% to 40%, in proportion to the hardness you wish to give to the tile ; calcium carbonate, in the form of powdered marble, varying from 5% to 30%; sawdust, in compressed form, with granules of between 0.002mm and 2mm varying from 3% to 30%; cellulose fibre with a maximum length of 2mm, varying from 3% to 10% glass fibres, broken up into lengths of a few millimetres, varying from 1 to 5%; talc, varying from 1% to 5% ; pigments, possibly iron oxide, following the known technology, varying from 2% to 10%.

The powdery mixture specified above is then carefully mixed with a rotary-blade mixer, rotating at a low speed, in order to prevent the lighter and/or smaller particles from escaping into the air. When mixing has finished, the earth-like mixture is transferred to another mixing machine, which has a kneading function. A watery solution of magnesium chloride with a density ranging from 20 to 35 Baume degrees and magnesium sulphate with a density of between 5 and 25 Baume degrees is in fact pumped into the machine, through special nozzles, at a pressure of approximately 1 bar. These composites are

present in respective proportions of 80/100% and 0/30%. The weight of this watery re-agent forms 30 to 70% of the weight of the total resulting mixture. The mixture is kneaded until it is completely blended.

Immediately after this it is transferred to a screw extruder that extrudes it through a die, which has the same section as the desired tile, after previously eliminating the gases contained in the mixture using well-know technological methods.

The advantage of this die is that it not only gives the tiles the required level surface but various shapes and sizes of longitudinal scoring. This die can also be asymmetrical in order to give the typical rounded edge to slabs with an elongated shape used at the top of steps. At its extrusion mouth this die can also be used with one or more rollers that may be idle or operating at a rim speed synchronised with the extrusion speed, in order to create, on the top that will constitute the decorative surface of the tile, transversal scoring, rustication, geometrical decorations and innumerable other shapes that can be obtained from the various ways of preparing the mixture laminated by the extruder. These rollers could work together with a conveyor belt, installed below, moving at the same speed as extrusion, and supporting the laminated mixture that has not yet hardened. These rollers could also replace the

usual cutting technique using tight steel wires. Such a cutting process could in fact take place by"rotary die- cutting"the laminated substance below during formation, defining in this way the perimeter shape of the tile, which may be straight or shaped at opposite sides so that it can be embedded. Once the shape of the tile has been defined, it is left to consolidate in the air, where it hardens spontaneously during a period that varies from 4 to 12 hours, according to the percentages of the various substances used. Finally the product is transferred to weathering rooms where it stays for 24 hours at a temperature ranging from 20 to 60°C, derived also from the heat that escapes from the tiles themselves due to the exothermic reactions connected to their hardening process.