Patent GB-946031-A (GB)
Title: Method for preparing vitreous silica products
IPC: C03C25/68
Filed: 1961-08-04
Abstract: In producing vitreous silica fibres by leaching a vitreous fibrous material with an acid and subsequently firing, particles of silica are applied to the fibres at any stage before firing.  The silica particles may be less than 100m  and preferably in colloidal form. Acids may be aqueous HCl, H2SO4, HNO3, acetic, or chloracetic. The silica particles may be added to the acid before the fibres, e.g. woven textiles, or fibres in bulk or in baths, are immersed therein, or as a coating to the fibres, which may, or may not, be dried, or allowed to dry, before contact with the acid.  The silica particles may be applied as a sizing to the fibres during drawing, or prior to weaving. Alternatively, the fibres may be washed with water containing silica particles after leaching.  The leaching may be effected at elevated temperature, e.g. above 100 DEG  F., with an acid concentration of 0.1-5N. A leaching time of 1-40 hours is employed depending on the acid concentration, the acid/glass ratio, the SiO2 content of the glass, the thickness and nature of the fibres, and the temperature.  Intermittent agitation ensures uniform distribution of SiO2 particles.  A concentration of less than 1% dispersed SiO2 particles having a diameter less than 50m  is preferred, and increasing concentration is required with increasing particle size.  After leaching, the fibres may be washed with water acidified to pH3-5, which may also contain dispersed silica particles.  Excess moisture is removed by heating to 200 DEG  C., and the fibres are dehydrated and heat shrunk at 1800 DEG  F. for several minutes to 1 hour. Specification 636,893 is referred to.ALSO:In producing vitreous silica fibres by leaching a vitreous fibrous material with an acid and subsequently firing, particles of silica are applied to the fibres at any stage before firing. The silica particles may be less than 100 m  and preferably in colloidal form. Acids may be aqueous HCl, H2SO4, HNO3, acetic, orchloracetic.  The silica particles may be added to the acid before the fibres, e.g. woven textiles, or fibres in bulk in batts, are immersed therein, or as a coating to the fibres, which may, or may not, be dried, or allowed to dry, before contact with the acid.  The silica particles may be applied as a sizing to the fibres during drawing, or prior to weaving. Alternatively, the fibres may be washed with water containing silica particles after leaching.  The leaching may be effected at elevated temperature, e.g. above 100 DEG F., with an acid concentration of 0.1-5N.  A leaching time of 1-40 hours is employed depending on the acid concentration, the acid/glass ratio, the SiO2 content of the glass, the thickness and nature of the fibres, and the temperature.  Intermittent agitation ensures uniform distribution of SiO2 particles.  A concentration of less than 1% dispersed SiO2 particles having a diameter less than 50 m  is preferred, and increasing concentration is required with increasing particle size. After leaching, the fibres may be washed with water acidified to pH3-5, which may also contain dispersed silica particles.  Excess moisture is removed by heating to 200 DEG C., and the fibres are dehydrated and heat shrunk at 1800 DEG F. for several minutes to 1 hour.  Specification 636, 893 is referred to.