GB729755A - Dyeing plastic sheets for use in glare screens - Google Patents

Abstract

<PICT:0729755/IV (c)/1> <PICT:0729755/IV (c)/2> A thermoplastic sheet for use in the manufacture of safety glass anti - glare screens is dyed from one edge with a gradually decreasing hue towards the middle thereof, by suspending it above a dye bath, gradually immersing it in the bath for a predetermined distance and at a predetermined rate, quickly withdrawing it from the bath and then rinsing it first with an aqueous alcohol and then with water. The sheet may be made of polyvinyl butyral which may be plasticized with dibutoxyethyl adipate, dibutyl sebacate, triethylene glycol dihexoate, or a mixture of triethyleneglycol caprate and triethyleneglycol caprylate, and the dye, e.g. an acid dye, is preferably dissolved in aqueous alcohol. Apparatus for carrying out the dyeing consists of a dye bath, a carriage for supporting the plastic sheets, means for creating relative motion between the carriage and the bath first to immerse the sheets in the bath and then remove them therefrom, control means for causing the sheets to be moved slowly into said bath at varying speeds for a predetermined distance and then removed quickly therefrom, and spray means for directing a rinsing medium on to the dyed area of the sheets immediately after removal from the dyebath. In operation, the plastic sheets 22 are held in dipping frames 27 supported on hooks 26 below a carriage 23 which is supported for vertical dipping movement upon uprights 40. The uprights 40 are connected by means of the linkages 50 and 51 and rod 52 to a slide plate 47, movement of which in an upward direction is caused by the weight of the carriage 23 and is controlled by a cam 67, the rate and extent of entry of the plastic sheets into the dyebath depending upon the contour of the cam 67. At the end of the upward movement the slide plate may be rapidly lowered by means of the geared unit 68 lowering the slotted link 71, so that the plastic sheets supported by the carriage are rapidly withdrawn from the dyebath 44. Immediately upon completion of the dyeing cycle, the carriage 23 is raised to the level of the rails 33, 34 along which it then moves to the rinsing section D where the sheets are subjected on both sides to an alcohol rinse by means of the spray pipes 81. After the first rinse, the carriage is moved along its rails to the second rinsing position E where the plastic sheets are rinsed with water supplied through spray pipes 102, which may be raised or lowered by means of the handle 121, a latch being provided to retain the spray pipes in their elevated position. The sheets are given a final rinse with distilled water.