GB1278340A - New elastic filaments and bristles and their production - Google Patents

Abstract

1278340 Diorganopolysiloxane fibres SOC RHODIACETA 29 Dec 1969 [30 Dec 1968 14 Oct 1969] 63149/69 Heading B5B [Also in Division C3] Filaments and bristles having a vulcanized diorganopolysiloxane as the filament-forming material and which possess both a kilometric breaking strength above 1À25 and an elongation at break of at least 300% are disclosed. The filaments may be made from a mixture comprising essentially: (a) 1000 parts by weight of an unvulcanized diorganopolysiloxane of formula where R represents monovalent unsubstituted or substituted hydrocarbon radicals, of which at least 60% are methyl and 0À03-2% are vinyl and which are free from substituents liable to interfere with the vulcanization process or to impair the long-term stability of the filaments or bristles, and where R<SP>1</SP> and R<SP>11</SP>, which may have the same or different meanings, represent H or an -SiR 3 group, and where n represents a number from 2,000 to 20,000. (b) 300 to 1000 parts by weight of a filler. This may be a form of silica having a high surface area (and may or may not have been treated with an organosilicon compound) such as pyrogenic silicas and silicas produced by precipitation, diatomaceous silicas, ground quartz, talc, mica, clay or sand. Also usable are lampblack, graphite, titanium oxides, iron, magnesium, zinc, antimony and aluminium oxides, calcium, magnesium and zinc carbonates, fibrous fillers such as asbestos or glass fibre and metallic powders, e.g. those based on aluminium, tin, zinc or iron. Other filters or adjuvants may also be added. (c) 3 to 30 parts by weight of a vulcanization catalyst. Many known producers of free-radicals may be used, such as organic peroxides and percarbonates and the oxaziridines, or catalysts based on platinum, in particular mixtures of a hydrogenopolysiloxane and platinum. (d) A plasticizer may also be added, generally no more than 50 parts by weight. Amongst such compounds are (tetramethylethylene dioxy)- dimethylsilane, diphenylsilanediol and hydroxylated or alkoxylated oils. In apparatus as shown, the composition is extruded through a spinneret (3) and the resulting filaments stretched by rollers (4) and (5) at a stretch ratio between 1 and 1À5 whilst being heated to 140-320 ‹ C. for a duration of 0À1 seconds to 5 minutes. The filaments receive a second stretch on rollers (6) and (7) or wind-up roller (8) with or without heating at stretch rates such that the overall stretch ratio is from 1À2-4À0. The heating and stretching is readily accomplished by using heated rollers after the extrusion. The stretch ratio is then governed by the relative speeds of the rollers. The extrusion and the first and second stretching are notwithstanding the heating, performed at a temperature in the neighbourhood of room temperature.