Patent GB-1379672-A (GB)
Title: Production of fine fibre mass
IPC: B29C48/05
Filed: 1972-05-31
Abstract: 1379672 Fine fibres OJI YUKA GOSEISHI KENKYUJO KK 31 May 1972 [1 June 1971] 25485/72 Heading B5B [Also in Division D2] A mass of fine fibres is made by a process comprising: (i) kneading a mass of a molten, water-insoluble, stable-to-water, linear thermoplastic crystalline polymer with water at a temperature above the melting point of the polymer and under a pressure at which water can exist in liquid state, thereby to produce a molten polymer mass which has water finely and uniformly dispersed therein, the quantity of water being from 2 to 50% by weight of the resulting molten polymer mass; (ii) adding supplementary water under an elevated temperature and pressure to the molten polymer mass obtained from step (i), the quantity of the water being at least 100% by weight of said molten polymer mass produced from step (i); and then, (iii) extruding the mixture of water and the molten polymer mass obtained from step (ii) into a region of lower pressure so as to evaporate the water dispersed in the molten polymer mass and the water added to the molten polymer mass whereby the molten polymer mass is cooled and subdivided into a mass of fine fibres. The linear polymer may be a polyolefin selected from homopolymers and mutual copolymers of ethylene, propylene, and butene-1, copolymers of the monomers as predominant constituents, with other monomers copolymerizable therewith, and mixtures of the polymers, particularly a mixture of a polyolefin and polystyrene. A water sorption agent, suitably a fine solid selected from nitrates, oxalates, acetates, sulphates, sulphites, carbonates, phosphates, hydroxides, and halides of alkali metals, alkaline earth metals (including magnesium) and ammonium, or a fine water-insoluble solid comprising a silicate, may also be present in the molten linear polymer. A surface active agent may be dissolved in the water dispersed in the molten linear polymer. In the apparatus of Fig. 1, the polymer is continuously melted in extruder 1, while water from reservoir 2 is heated by heat exchanger 4 and continuously pumped via pressure control valve 5 into kneader 6, suitably an extruder, where the water is dispersed in the polymer melt to form a fine dispersion of water and polymer. The dispersion is pumped at high pressure to extrusion orifice 13 by metering pump 8, the pressures in the flowpath upstream from orifice 13 and in the transfer zone being sensed by pressure gauges 17 and 18. Near the orifice, water heated in heat exchanger 11 is injected by high pressure metering pump 10 into the transfer zone, its pressure being adjusted by pressure control valve 12 so as to maintain a constant flow rate. Ejection of the polymer-water dispersion at orifice 13 into the atmosphere results in the production of a mass of uniform fine fibres of high rigidity. In the apparatus of Fig. 2 the melting of the polymer, injection of water, and kneading and dispersion of water are carried out in a single extruder. Figs. 3, 4 and 5 (not reproduced) show various types of extruder used to introduce the supplementary water; in each the water is introduced through the orifice at the side.