PROCESS INVOLVING HEAT TO UNITE THIN STRUCTURES OF SYN¬ THETIC MATERIAL, SUCH AS WOVEN AND NON-WOVEN FABRICS MOQUETTES AND THE LIKE, WITH PLASTIC MANUFACTURED GOODS

The invention concerns a process for the production of manufactured goods made of plastic material.

It is known that the use of heat is impossible for uni¬ fying thin structures of synthetic material , such as wo¬ ven' and non-woven fabrics, moquettes and others, with articles made of plastic material when the usual processes of moulding - especially injection moulding - vacuum form¬ ing, thermoforming, extrusion, calendering and others are adop ed , s ince high temperatures tend to melt said thin structures which in any case are damaged by the heat.

Also well known are the limitations inherent in other me- thods of unification.

Glueing is only possible when the manufactured goods can be attacked by solvents and by glues, therefore excluding for example those made of polyolefines such as polypropy¬ lene, polyethylene and others. The purpose of the above invention is to overcome these drawbacks as will be described below.

According to the invention the thin structures of syn¬ thetic material, such as woven and non-woven fabrics, moquettes and other kinds become heat-conducting and are made to adhere to a metal or in any case a highly hea -conduc ing surface.

Consequently, during the operation of unifying the thin structure with a manufactured article made of plastic ma¬ terial, the heat transferred from said material to the thin structure rapidly passes through the latter and into the heat-conducting wall behind thus preventing the

said thin structure from becoming overheated and damaged. The aforesaid thin structure can be made heat-conductive by impregnation with an emulsion of oil and water or some- similar emulsion, or by application of pastes containing a high percentage of metallic materials or, in any case, heat-conductive. During the unification process the vo¬ latile parts evaporate taking up heat and leaving the ma¬ nufactured product dry. In the technique of moulding plastic materials by means of dies, the aforesaid thin structure can be made to ad¬ here to the moveable die by bushings and the like kept pressing against said thin structure by pins sliding in holes made in the fixed die pressed by springs. The bushings are made of plastic material substant ally the same as that of the product to be moulded, their length not exceeding the thickness of said product to allow them to become spontaneously surrounded by the mass of material during the moulding process. The above thin structure can be protected from the flow of injected plastic material by means of a screen placed in front of the injection outlet and supported by pins and the like sliding in seats made for them in the fixed die . The dimensions of said screen must be substantially less than those of the product for moulding and its material must be the same as that of said product so that said screen can become spontaneously embedded within the mass of plastic material during moulding. In the vacuum forming technique the above thin structure is placed over the preformed sheet to which it is to be united, said sheet having been previously heated, and is

then pressed by counterdies against the lower die. In the vacuum thermoforming technique with vertical mould¬ ing machines the aforesaid thin structure already united ^• with a sheet is so placed as to face upwards while the electric heating elements for heating the forming die 1i,e below the sheet to be thermoformed .

In extrusion, the aforesaid thin structure is united with sheets, of thermoplastics and similar material ,when extru¬ sion takes place. Rollers are used to treat the aforesaid thin structure with the heat-conducting emulsion or with another heat-conduc¬ ting product.

By suitably regulating the temperature of the extruded ma¬ terial and the pressure of the extruding rollers, the thick- ness of said thin structure that must be left free can be determined at will.

In the thermoforming process the aforesaid thin structure already united with a sheet, is placed so as to lie out¬ wards from the manufactured product-, namely downwards and towards the female die, the male die being above.

In calendering to unite the aforesaid thin structure with a sheet of thermoplastic material, said structure is made to pass - together with the sheet of thermoplastic material under it - between upper cold rollers and lower heated ones

If the synthetic material of which the thin structure is made, such as woven or non-woven fabric, moquettes and the like or a part of said material and if the plastic material of the manufactured product with which said thin structure is being united by means of heat, are of a suitable kind,under the action of heat said thin structure and said product be¬ come united by welding together in a continuous and stable manner .

In other cases unification under the effect of heat takes place by the mechanical grip of elements composing the above thin structure, said elements entering the plastic material of the manufactured product during thermoformin _g thus increasing the stability of unification.

Where the material of the above thin structure made of synthetic material requires it, said structure is given pre.vious treatment with products that assist it, or some elements of which it is made, to get caught up in the body of the product made of plastic material

The advantages of the material are evident. Not only is the union made possible of thin structures made of synthetic material such as woven and non-woven fabrics, moquettes and the like with manufactured pro- ducts of plastic material even those unsuitable for re¬ ceiving glues and the like, such as polyethylene polypro¬ pylene and others, but such union is extremely strong on account of the aforesaid structure becoming partial¬ ly embedded in the plastic material. This union can be achieved without any trouble making use of practically all the known techuiques from injec¬ tion moulding to extrusion, from calendering to thermo- forming . By means of this invention, kinds of application never before possible can now be effected quickly and efficient-, ly , creating an innumerable quantity of new items as well as great improvements to those already known and offering possibilities of important industrial and commercal de¬ velopments . Characteristics and purposes of the invention will be made still clearer by the following example of its execution

illustrated by diagrammatic figures.

Fig.1 Section of an injection die for moulding a sheet of polypropylene associated to a moquette-type of fabric . Fig.2 The product tkan from the die after moulding. The die 10 is composed of a fixed part 11 and a mobile part 12.

The polypropylene is put into the die by the injector 14. The piece of moquette 20 is kept adhering to the wall 17 of the metal mobile d-ie 12 by means of bushes 21 suppor¬ ted by pins 22 free to translate in seats 23 in the fixed die 11 under pressure from cylindrical compression springs 24. The length of the bushes 21 is less than the thickness A of the polypropylene sheet 13 to be obtained. Said bushes are made of the same material.

The thin structure consisting of the moquette 20 has pre¬ viously been impregnated with a water-oil emulsion to make it heat-conducting. The injection mouth 14 is protected by a screen 30 con¬ sisting of a polypropylene disc with rear pegs 31 fitted into seats 32 made in the fixed die 11.

The thickness B of said disc is less than thickness A of the polyethylene manufactured product. During moulding the disc 30 becomes embedded in the pro- pylene product 13 while the supporting pegs 31 will be removed together with the injection stem 16. The heat passing from the thermoplastic material to the piece of moquette 20, due to the high degree of heat con- ductivity said structure possesses after impregnation with the oil-water emulsion, rapidly passes into the mass of

the mobile die 12 to whose inner wall 17 said moquette ^' 20 has been made to adhere.

As a result of this said moquette does not get hot enough to suffer damage. This phenomenon is similar to that occurring when the lighted end of a cigarette is placed on a sheet of flimsy paper adhering to a heat conducting surface. Said surface absorbs the heat so rapidly that the 800° of -the lit end of the cigarette do not raise the tempe¬ rature of the flimsy paper higher than about 60°.

When moulding is finished the bushings 21 and the disc 30 remain embedded in the sheet forming part of it and the product so obtained possesses all the best characteris ics offered by a perfect union between a semi-rigid material like polypropylene and a fabric structure like moquette.