Patent ES-339747-A1 (ES)
Title: Improvements relating to the production of filament-like structures from synthetic materials
IPC: B29D28/00
Filed: 1967-04-25
Abstract: In a process for the production of filamentlike structures from synthetic materials in which a continuous sheet of film is cut longitudinally into strips which are then stretched and, if desired, twisted, the sheet of film is cut into strips with curved or serrated edges. The sheet of film may be partly stretched before it is cut up into individual strips, and the strips are suitably wound on winding mechanisms whose rotational speed is regulated in dependence upon the tension of the strips, into cross-wound packages or large cops of any structure, in particular in so-called parallel winding. In synthetic material strips so formed, at least one of the two longitudinal edges of the strip formed in the direction in which the sheet of film travels is curved or serrated. Preferably, both the longitudinal edges are curved or serrated, and the indentations in one of the longitudinal edges of the strip are arranged at such a distance apart from the indentations in the other longitudinal edge that a strip zone extending on a straight line in the longitudinal direction of the strip itself, is formed between the two rows of indentations. In both forms of strip, the curved or serrated edge form of the strip may be interrupted at intervals by a straight edge form. The intervals between the indentations or projections along one edge may vary in size and, in particular, increase and decrease in length. The indentations or projections along one edge may be displaced in relation to the indentations or projections along the other edge in the longitudinal direction of the strip. The indentations and projections along one edge of the strip may differ in shape from the opposite regions of the other longitudinal edge. Such a strip may consist of several interconnected plastics layers which differ in their physical properties. One or both outer layers of such a strip may consist of foamed plastic. In apparatus as shown (Fig. 1), a sheet of film 6 is extruded from the die 5 and solidified in cooling bath 7 fitted with deflector roll 8 to such an extent that it can be cut by cutting discs 13 on a cutter shaft 12 after passing a tension roller or bars 9 and a supporting roller 10 in a supporting frame 11. Cooling rollers may be used in place of the cooling bath 7. A motor 14 drives cutter shaft 12 through gear unit 15. The rotational speed of godets or rollers 16 of a stretching arrangement 17 governs the delivery rate of the sheet of film 6. In addition, the stretching arrangement 17, in conjunction with tension rollers 9 and supporting rollers 10 and 18, produces the tautness in the sheet of film required for cutting in the proximity of the cutting discs 13 between the supporting rollers 10 and 18. Cutting discs 13 are mounted on cutter shaft 12 in such a way that the wavy lines of the cutting edges extend parallel to one another. In order, however, to obtain strips in which the wavy lines of the cut edges are not parallel to one another, i.e. in which the amplitudes of the waves or serrations are staggered in relation to one another, the cutting discs 13 may alternatively be so mounted on cutter shaft 12 that they are offset at a certain angle relative to one another. Alternatively, a non- rotatable cutter beam in which knives or razor blades are clamped may be used in place of cutter shaft 12. To produce the curved wavy or serrated cut edges of the strips of film, the cutter beam is reciprocated transversely of the direction in which the sheet of film is travelling, e.g. by means of a crank drive. After leaving the last roller 16 of stretching arrangement 17 the film, cut into strips 19, travels through heating zone 20 before it is taken up by rollers 21 of a stretching arrangement 22. Rollers 21 rotate at a higher speed than the rollers 16 so that the ratio between the two rotational speeds governs the degree of stretching of the strips 19 which can vary between 1: 4 and 1:12. Strips 19 are guided from stretching arrangement 22 to machine frame 23 with as many winding heads 24 as there are strips. Before strips 19 are wound on to the packages 25 of winding heads 24, they travel over a comb-like guide bar 26 fixed to the machine frame 23, a guide roller 27, a so-called dancer arm 28 and another guide roller 29, to the thread guide of a traversing mechanism 30 which lays the individual strips 19 on their respective packages 25. Dancer arm 28 senses the tension of the particular strip 19 and regulates the rotational speed of the package 25 and the speed of reciprocation of the traversing thread guide by way of a separate control unit. Fig. 3 shows a strip cut out of a non- laminated sheet of film before stretching, and Fig. 4 shows such a strip after stretching Fig. 5 is a longitudinal section through an unstretched strip consisting of a carrier film and a plastics layer foamed on to it, and Fig. 6 is a longitudinal section through such a strip after stretching. Examples relate to the production of polypropylene filament-like structures and foamed polypropylene filament-like structures.