Smoke filters

Collagen fibres are used within one end of a cigarette wrapper as a filter tip, or as a filter cartridge in a tobacco pipe. The fibres may be derived from various specified skin or hide materials, from bone tendon or other connective tissues, or from partially detanned leather scrap, or may be reconstituted from dissolved collagen. The fibres may be chemically created to control their water absorption and chemical stability and may comprise from 0.5% to 2.5% by weight of an aldehyde or 0.5% to 1.5% of a metallic tanning agent, e.g. chromium, aluminium, zirconium or iron, or may contain a polyphosphate or vegetable tanning agent. The fibres may comprise acidic collagen fibres which have been equilibriated at a pH of 2.5 to 6.5 and alkaline collagen fibres which have been equilibriated at a pH of 7 to 11 mixed in a ratio between 1 : 10 and 10 : 1. The fibres may be mixed with cellulose acetate fibres. In a filter, the fibres may extend generally in the same direction or randomly or the fibre mass may be helically twisted. The fibres may act on tobacco smoke particles chemically or by neutralization of electrical charges thereon. The fibres have a specific surface area of 298 sq. metres per gram. Quantitative process examples of the preparation of suitable collagen fibres are given.