GB737170A - Improvements in a method of producing stencils - Google Patents

Abstract

737,170. Paper for stencils &c. DICK CO., A. B. Jan. 1, 1952 [Jan. 5, 1951], No. 23/52. Drawings to Specification. Class 96. [Also in Group XVI] An ink-impervious sheet for use in producing duplicating stencils (see Group XVI) consists of a felted layer comprising a mixture of heatdestructible fibres, e.g. cellulose pulp, and a minor proportion of heat-insensitive or less heat-sensitive fibres, e.g. glass or synthetic fibres. The heat-insensitive fibres are in a proportion of 3-40 per cent, preferably 20 per cent, and may consist of mineral fibres such as glass, asbestos or rock wool. The destructable fibres may consist of kraft or a sulphite type of pulp cellulosic fibres, or, alone or mixed with the pulp fibres, wool, cotton, silk, hemp, or synthetic resinous fibres such as regenerated cellulose polyamides (nylon), cellulose acetate (rayon), vinyl acetate-vinyl chloride, or polyvinylidine chloride. The sheet may also contain fillers such as finely-divided silica, diatomaceous earth, titanium dioxide or chalk, and should be calendered or compacted. For example, a sheet may be 0.002 inch thick and include 90 per cent kraft pulp fibres and 10 per cent by weight glass wool fibres # inch long. Glass fibres 1/16 -¢ inch long or more may be used. In order to lower the temperature necessary for destruction of the fibres to form the stencil (see Group XVI), activators may be used, which may be incorporated in the sheet, or applied by coating or impregnation, or included in the ink composition or carbon composition applied to the sheet. Activators used, particularly with cellulosic pulp fibres, may be hydrochloric acid, sulphuric acid, and aluminium, bismuth, ferric, cupric or stannic chloride, cupric, ferrous ammonium, chromium, potassium or mercuric sulphate, potassium bisulphate, ammonium persulphates, peroxides, perchlorides, or nitrates, or organic acids or acidic compounds such as citric acid, aniline hydrochloride, aniline nitrate, aniline bromide, aniline hydrobromide, organic sulphonic acid, 1-naphthalene, 4-sulphonic acid, indophenol, ammoniuin thiocyanide, coupled with ferric chloride, and mixture of such compounds. The activator should be present to 0.1-10 per cent by weight of the fibres to be destroyed. An example is a sheet of 20 per cent glass fibres, 80 per cent pulp fibres with 1 per cent ferric chloride, and carbon paper to apply the letters containing ferric sulphate.