GB1183498A - Improvements relating to Tobacco-Smoke Filters - Google Patents

Abstract

1,183,498. Tobacco-smoke filters. BRITISH-AMERICAN TOBACCO CO. Ltd. 21 Oct., 1968 [24 Oct., 1967; 24 Nov., 1967; 4 Jan., 1968], Nos. 48233/67, 53548/67 and 673/68. Heading A2C. Tobacco-smoke filters comprise synthetic resin foam material comminuted to a particulate form and wrapped in a band. Preferably a polyurethane resin foam is used but other suitable synthetic resins are polyvinyl chloride, polyethylene, polystyrene, polystyrene/acrylonitrile copolymers, or less desirably condensation polymers of phenols, urea or melamine with formaldehyde. The particulate foam material may be bonded with an adhesive which may be a thermoplastic or thermosetting resin, e.g. a polyethylene resin, or may be an inorganic substance of low melting point i.e. below 250‹C., e.g. crystalline sodium orthophosphate dodecahydrate, and may constitute up to 80 per cent of the total weight of the mixture of adhesive and comminuted foam. Manufacture. Mixtures of comminuted foam material and adhesive may be fed on to a paper band, which band is advantageously coated with a thermoplastic adhesive, and the band is then passed through compression, heating and shaping stations to produce a continuous filter rod. Alternatively, the comminuted foam, with or without powdered or granular adhesive, may be brought into filter rod form by feeding it on an uncoated paper band to the garniture of a conventional cigarettemaking machine. In this latter case, if adhesive is mixed with the foam material it need not be activated by heating until after the rod has been formed. Suitably modified forms of known apparatus are disclosed. In the examples: toluene diisocyanate and diphenylmethane-4 : 4<1> diisocyanate based rigid polyurethane foams were comminuted mixed with comminuted sodium phosphate dodecahydrate and formed into filter sections which were sandwiched between pairs of fibrous cellulose acetate filter sections; zinc acetate was added to a polurethane/sodium acetate mixture to enhance the removal of hydrogen cyanide and hydrogen sulphide by the filter formed therefrom; and cupric nitrate trihydrate was used as the adhesive for a polystyrene foam material. Other adhesive materials used with a toluene diisocy anate based rigid polyurethane foam were sodium perborate tetrahydrate, hydrated calcium bromide, aluminium bromide non- ahydrate, ferrous sulphate heptahydrate, cupric nitrate trihydrate, sodium aluminium sulphate dodecahydrate, sodium acetate trihydrate, magnesium acetate dihydrate, aluminium stearate and magnesium stearate.