Patent GB-580370-A (GB)
Title: Improvements in or relating to the manufacture of low density filamentous masses for heat insulation and other purposes
IPC: D04H3/16
Filed: 1944-03-09
Abstract: <PICT:0580370/IV/1> <PICT:0580370/IV/2> <PICT:0580370/IV/3> A light-weight filamentous product suitable for use as a heat insulating material, cushioning material, buoyant material, or air filtering material, comprises a bulky mass of filaments exhibiting internal surfaces of cleavage and formed of several layers of filaments extending substantially entirely across the mass and intercrossing in an irregular manner.  The filamentous mass may be obtained by passing a bundle of filaments through a fluid medium under turbulent conditions, forming the bundle into a sheet of a width large in respect of its thickness, and collecting the sheet in the form of a multiple-layered winding.  After collection, the wound sheet is cut transversely and removed from the winding device.  The multiple-layered sheet thus obtained is stretched in the direction of its width while being held taut along its length.  The length of the band is somewhat reduced, but the width and thickness are greatly increased to produce a light-weight fibrous product.  As shown in Fig. 1, a large number of filaments 2 is extruded from a nozzle 6 and conducted through a coagulating bath to a winding drum 5, funnel guides 4 and 7 being provided.  The guide 4 has an opening of large diameter so that the filaments are brought into the form of a flat sheet at the point of winding.  The coagulating liquid becomes turbulent as a result of the streaming of the filaments at high speed, and the filaments become intercrossed in an irregular manner. The motion of the liquid also produces some traversing of the sheet as it is laid on the drum.  If desired, the width of the band may be increased by traversing the guide 4 or the drum 5, or sheets of filaments from a plurality of adjacent spinnerets may be wound upon a single drum.  As shown in Fig. 4, a number of untwisted filamentary ropes or strands 14 are conducted into a liquid 15 under rod 16 which tends to fan out the filaments as they proceed to collecting drum 17. The sheet-like band of filaments passes nozzles 18, 19, which introduce jets of fluid such as air or water into the liquid bath and produce turbulence and fanning out of the filaments.  Lateral limiting guides 20, 21 are provided.  As shown in Fig. 5, an untwisted filamentary tow or rope 24 passes vertically downwards to winding drum 28.  Jets of air or water are directed against the bundle from nozzles 26, the orifices of which are so disposed as to cause a spreading out of the tow.  The fanning out of the filaments is facilitated when these are of hydrophobic character since the filaments become electrically charged by friction and repel each other.  The fanning out of hydrophobic filaments may be obtained by passing the tow over an electrically charged comb.  If the filamentary sheet is wound when in dry condition, it is preferable to wet the wound mass to compact it.  The mass is then dried, preferably after being cut and flattened out, and is then stretched in the direction of its width to form a product of low density.  The expanded product is composed of a number of separable layers, each of which is composed of a network of filaments.  A product of lower density may be obtained by separating the layers and then re-assembling them merely by laying them on top of one another.  The filaments used in making the product may be natural continuous filaments such as silk, filaments of glass or other inorganic material, or continuous artificial filaments of regenerated cellulose, cellulose esters or ethers, or polyvinyl compounds such as copolymers of vinyl chloride and acrylonitrile or vinyl acetate. Hollow or inflated filaments may be used.  Filaments of diameters of one half to 10 microns, or larger filaments up to those of 5 or more deniers may be used.  Mixtures of filaments of various diameters may be employed.  The dry filamentous mass may be subjected to treatment for shrinking the filaments therein.  Thus a polyvinyl resin mass may be subjected to a heat treatment.  The shrinking treatment gives a product of greater resilience and greater coherence between the filaments.  In making the product, mixtures of shrinkable and shrink-resistant filaments, or mixtures of elastic and non-elastic filaments, or mixtures of potentially adhesive and non-adhesive filaments may be used.  After collection on the winding drum the filamentous mass may be subjected to an activating agent for the potentially adhesive filaments, e.g. heat, or a solvent, or swelling agent, so as to cause those filaments to become tacky and to adhere to the other filaments. After de-activation, e.g. by cooling, or by evaporation of solvent, the product may be stretched.  The product so obtained comprises a skeleton network of adhesively secured filaments preventing the ready separation of the layers of the surrounding mass of filamentous material.  If desired, the activating agent may be applied only to selected portions of the sheet.  A composite mass may be obtained by superimposing wound bands of filaments collected as described above upon alternate layers of carded bats made of filaments of a different material.  The laminated mat or sheet may be cut with a sharp tool such as a razor, or with scissors or like shearing device.  In the latter case, the edges are deformed and have the appearance of a seam. The product may be given a quilted effect by applying pressure with an embossing roller, before or after enveloping it in a covering fabric.  The product may be used as blanket material. When hydrophobic filaments are used such as polyvinyl chloride-acetate copolymers, the product is substantially water-proof, and is useful in making life-belts.  Where mixtures of different filaments or mixtures of filaments of different sizes are used in making the layers of the material, spinnerets provided with different spinning solutions or having differently sized orifices may be arranged so that the filaments proceeding from them intermingle, or filaments drawn from a package may be fanned out just before reaching the spinning bath in which the other component filaments are freshly formed.  One or more filaments or twisted or untwisted bundles of filaments may be laid down with traverse about the filamentary band between the several convolutions therein as it is being formed.  Specification 579,183 is referred to.