GB906086A - Flexible ducting - Google Patents

Abstract

906,086. Making flexible ducting. IMPERIAL CHEMICAL INDUSTRIES Ltd. Jan. 18, 1961 [Feb. 3, 1960], No. 3821/60. Class 99(2). Flexible ducting is made by feeding an organopolysiloxane gum composition in strip or ribbon form into a nip formed between a rotating mandrel and an idler roll until the desired thickness of the composition is obtained and thereafter heat curing to an elastomer. One or more reinforcing fabric layers in sheet, strip or tube form e.g. knitted, woven or felted fabric of metal, glass cloth, cotton, polyethylene terephthalate or a synthetic polymer, may be included. Sheet or strip reinforcement may be firstly wrapped round the mandrel and coated with an adhesive or applied over an organopolysiloxane layer or in tube form it is placed on the mandrel and, if necessary, coated with an adhesive. The mandrel may be first wetted with a wetting agent such as ethylene oxide, with alkyl phenols, fatty acids, resin acids or sorbitan monostearate. Curing under heat and pressure may be carried out after applying a tape such as of polyethylene terephthalate followed by a shrinkage tape, e.g. wet cotton, in live steam or air at 120‹-150‹C for ¢ to 1¢ hours. After removal of the mandrel and the wrappings an after-cure at 200‹ to 250‹C for 24 hours may be given. The organopolysiloxane gum may have a methyl, phenyl or vinyl organo group or two or more different groups. Fillers may be fume silica, precipitated silica, silica aerosols, diatomaceous earths, titanium dioxide or zirconium silicate which may be treated before use to modify surface characteristics e.g. by a polysiloxane. Plasticizers may be diphenylsilanediol or (tetramethylethylenedioxy) dimethylsilone. Curing agents may be an organic peroxide such as benzoyl, chlorobenzoyl or dicumyl peroxide.