GB896599A - Improvements in or relating to tobacco smoke-filtering elements - Google Patents

Abstract

Filtering elements for cigarettes, tobacco pipes or cigar or cigarette holders comprise a bundle of continuous synthetic filaments with particles of a water-insoluble calcium or magnesium salt distributed over their surfaces and bonded thereto by an agent miscible with, or a solvent for, the filament material. The filaments may be bonded together at random points. A salt of meta-, ortho- or pyro-phosphoric acid or of stearic or carbonic acid may be used, and the particles may be between 0.1 and 10 microns in size and form from 5% to 60% of the filtering element. The major portion of the particles may be of a size less than twice the filament diameter but greater than one-tenth the filament diameter, and preferably, at least 80% of the particles are of less than filament diameter. The particles may be blown on to the filaments, or applied thereto as a slurry in cold water or in a volatile organic vehicle, or they may be applied electrostatically to filaments in the form of a banded tow. Alternatively, the particles may be dusted on to a banded tow of filaments, the surface of which is wetted with adhesive, e.g. dextrin glue, or with plasticizer, before, during or after dusting, e.g. a slurry of plasticizer, salt particles and perhaps water or alcohol may be used. The filaments may be nylon, polyamide, polyester or regenerated cellulose, or of cellulose acetate having 4 to 10 crimps per inch, 3 to 16 denier and 4,000 to 35,000 filaments to a bundle. The plasticizer may be glycerol triacetate or tripropionate, triethyl citrate, or di-(methoxyethyl)phthalate with or without sodium lauryl sulphate. After treatment with plasticizer and particles, a banded tow may be returned to its original shape and bonded by heat treatment after forming into paper-wrapped cigarette filter rod lengths. To aid particle bonding, the filament surfaces may be treated with an oil, before or after adding the plasticizer and particles. The oil may comprise from 3% to 8% of the filtering element and is colourless, odourless, tasteless, non-volatile and non-toxic, and insoluble in the plasticizer at room temperatures although it may be soluble therein at elevated temperatures so that it may be applied dissolved in the plasticizer applied hot. Suitable oils are castor, cottonseed, almond, coconut, peanut and olive; pharmaceutical grades of light, medium and high viscosity mineral oils, lauryl alcohol and glycerol oleates, laurates and ricinoleates. Quantitative process examples are given.