Applicant: WINDTEX VAGOTEX S.p.A.

Designated inventor: Elisabetta GASPARI

The present invention relates to a process for making a polyurethane multi-layer membrane, and a multi-layer membrane thus obtained.

In particular, the invention is advantageously used in the creation and production of articles or garments, such as shoes or industrial work clothes, and the like, or of technical-sport clothes, to which the following description will make explicit reference without thereby losing generality, in order to protect in an effective and optimal manner, in particular at low temperatures.

The structural and functional characteristics of the present invention and its advantages will be apparent from the underlying claims, and in particular from an examination of the following description made on the basis of a preferred but non- limiting schematic embodiment of the present process.

The process for making a multilayer membrane for use in industrial work and/or technical garments or clothes includes the mutual coupling of at least a first support layer (neutral support), formed by a polyurethane film in a solvent, with a weight of about 15 g/sqm, and a second layer, formed by a film of polyurethane in a solvent, with a weight of about 30 g/sqm, to which a determined amount of graphene nano powder, a white pigment, and a solvent (with a mixing carried out at ambient temperature) are also added.

According to the preferred formulation indicated below in the parameter table, the above-mentioned polyurethane film of the second layer is in a percentage varying from 50 to 55% (with best performance obtained experimentally at 52%), graphene is from 7 to 10% (with best performance experimentally obtained at 8%), a white pigment is from 0.2 to 1 %, and solvent, in particular DMF, is from 20 to 40%.

PU 25.9 kg 51.80%

GRAPHENE 4 kg 8.00%

WHITE 1/C pigment 0.1 kg 0.20%

DMF 20 kg 40.00%

Total 50 kg 100.00%

Note that the above-mentioned first and second layer forming the membrane are initially been obtained separately in laboratory, by lying the solution on an appropriate silicone-coated white paper, which is arranged through a "pilot", i.e, via a laboratory instrument that allows, by means of a blade, to apply the product on the above paper to obtain a thin layer. Then follows a period of polymerization, where the film on paper is inserted in the oven first at 100°C for one minute (drying) and then at 150°C for three minutes. Subsequently, the two first and second layers are coupled together by means of glue spotting application, applying a pressure of between 2 and 4 bar and at a temperature between 140 and 160°C, assuming a total thickness between 30 and 60 microns and a total weight of the membrane thus obtained in the range 40-70 g/sqm.

At the industrial level, however, the creation of the finished membrane is carried out in an industrial double-head machine coater, where the membrane is formed in two consecutive layers and without having to couple them as in the laboratory: in a first tray the above-mentioned first layer (or 'neutral' polyurethane) is loaded, then on a cylinder the silicone-coated paper is wound that, once it is operated, collects the solution from the tray to carry it inside appropriate ovens. At the outlet there is a second tray, which instead contains the solution provided by the mentioned second polyurethane layer with graphene, which is thus deposited on the first layer of neutral polyurethane previously created. Subsequently, the paper continues its movement through other ovens: therefore, at the end the same paper with the finished membrane (precisely formed by the two layers of film) will be rolled up on a reel. Finally, after an appropriate waiting period, the membrane will be 'solidified' and with the possibility of detachment from the above-mentioned paper support. With the aim of creating a fabric to be used particularly advantageously in the production of clothing in use in working activities or in sports, which is subject to external environmental weathering (e.g., cold places and/or harsh environments), exploiting particularly the very high conductivity of graphene, preferably the process also provides for the application on the above membrane means of electrical connection to a portable battery, such as a conductive ribbon, which is also made from graphene, thus realizing a multilayer membrane provided with a high heating power.

Indeed, from experimental tests, it has been shown that by applying to the membrane a 15 volt electric current, about 27mA and an increase of about 10°C than the surrounding environment have been detected, while at 30 volts about 53mA and an increase in temperature of about 25°C have been detected.

According to a preferable embodiment, after completion of the formation of the membrane by coupling the two above-mentioned first and second layers, the present innovative process may be advantageously provided with a further operative bonding step, during which the membrane itself is coupled with at least one laminate layer of predetermined material, preferably polyester (PES), polyamide (PA) or cotton (CO), polypropylene (PP), elastane (EA) and wool (WO), coupled to the membrane with 'spotting' or Open field' glue, also preferably added with graphene. Preferably, but not limited to, the above-mentioned membrane is disposed between two layers of laminated fabric as specified above.

A multilayer fabric with high impermeability and high windproof and thermal shock resistance capacities is therefore obtained, such as to be optimally used in clothing for use in industrial, technical and/or sport sectors.