GB442866A - Improvements in or relating to the impregnation of articles with solutions in volatile (distillable) solvents - Google Patents

Abstract

<PICT:0442866/IV/1> In a process for impregnating materials with solutions containing a volatile solvent, the solution is subjected to a partial vacuum prior to its admission to the impregnating tank wherein the material is under vacuum. After the preliminary drying has been completed in an impregnator a which is under high vacuum from a pump j, the valve j<2> is opened for a short time to remove air from above the impregnant in a tank b. The impregnant is then admitted by gravity or transfer pump to the impregnator a through a pipe b<1> and valve b<2>, after which the valve j<2> is closed. After a few minutes the vacuum is broken by opening a valve f or by admitting an inert gas or further impregnant. A positive pressure is then <PICT:0442866/IV/2> applied by the combined compressor and vacuum pump k. After impregnation surplus solution is returned to the tank b, e.g. by means of a transfer pump. Solvent is removed from the material by evacuating the impregnator by pump k and admitting air through a filter c, drier d and heater e. A partial vacuum may be maintained during drying by means of a controlled leak in the inlet system. Oxidation or polymerization of the impregnant may be effected by the hot air treatment and may be completed in a separate oven. Solvent is recovered in a condenser g and transferred by the pump k to a storage tank h and thence to the varnish tank b. In the modified apparatus shown in Fig. 1 (Comp.), the vacuum side of pump k is connected to the varnish tank b instead of the pump j and the compressor side of pump k is connected through a pipe l to the intake of the heater e, or alternatively, through an extension m to the intake of drier d through a valve n. Specification 313,987, [Class 140], is referred to.