Patent GB-1386438-A (GB)
Title: Non-woven fabric of fibrillated webs having a network structure  and a process for producing same
IPC: D04H13/00
Filed: 1972-07-20
Abstract: 1386438 Laminated non-woven fabric NIPPON PETROCHEMICALS CO Ltd 20 July 1972 [24 July 1971] 34105/72 Heading B5N A non-woven fabric comprises two fibrillated webs bonded together to form a unitary structure, each fibrillated web being formed from a composite film comprising at least two layers bonded together to form a unitary structure, a first said layer A being a plastics layer which is adapted to be stretched at a given temperature to impart thereto a stretch effect and a second said layer B being a plastics layer which exhibits substantially no stretch effect but which has a melting point or softening point which is lower than that of said first plastics layer and at which a stretch effect imparted to said first plastics layer is not adversely effected, the second plastics layers of the fibrillated webs being heat- and pressure-bondable to each other, and the non-woven fabric having been formed by arranging the fibrillated webs so that their second plastics layers are in face-to-face contact and applying heat and pressure thereto to bond said second plastics layers together at their areas of contact without adversely affecting the stretch effects imparted to said first plastics layers. A fibrillated web is defined as being a plastics film which has been uniaxially stretched to impart a stretch effect thereto, split into fibres substantially in the direction of stretching so that the fibres are not completely separated but are connected to their adjacent fibres by means of branch fibres, and then spread transversely so as to form an open network of substantially parallel, spaced apart fibres joined by spaced apart branch fibres. Stretch effect is defined as that property of certain polymer films, when the polymer film stretched uniaxially and longitudinally to a length at least several times its original length at a temperature which allows molecular orientation, by which the polymer molecules are oriented in the stretch direction and the strength of the film in this direction is increased while at the same time is more readily splittable in the stretch direction and hence more readily fibrillatable. Adverse affect on a stretch effect is defined as being a decrease in the strength of the film in the stretching direction. The first layer may be formed of high density polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polyacrylonitrile, polyvinylidene chloride, polyamide or polyester. The second layer may be formed of low density polyethylene, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer or thermoplastic rubber. The composite film may be made by bonding, e.g. by heat or adhesive, the preformed films; alternatively, a co-extrusion process may be used. In a preferred embodiment, a composite film comprises a layer of a polymer exhibiting a stretch effect sandwiched between two layers of a polymer exhibiting no stretch effect. The two fibrillated webs may comprise different components. The splitting operation, which follows the uniaxial stretching by using a barbed needle, a rotating file bar or by a twisting process. The fibrillated webs are preferably assembled at an angle of 90 degrees. The non-woven fabrics may be used in combination with other sheet material, e.g. paper or cloth, the combination being such that a polymer layer of relatively low softening or melting point is in contact with the other sheet material.