Patent GB-377995-A (GB)
Title: Improvements in or relating to the preparation of colloidal suspensions of solids
IPC: B01J13/00
Filed: 1931-04-24
Abstract: In a process for reducing solids to the colloidal state, the powdered material is mixed with a colloid and sufficient of the suspension medium to form a stiff and adhesive paste.  The paste is caused to adhere to a surface and another surface is moved relatively to the first surface and sufficiently close thereto to cause the paste to adhere to the second surface and be torn away from the first surface whereby a shearing action is exerted on the paste structure.  The colloid used preferably imparts adhesive properties to the paste, e.g. gum arabic, gummy materials, gelatine, albuminous substances, concentrated sulphite lye from wood pulp manufacture, and cellulose derivatives such as hydrocellulose.  The material obtained is stirred up with the suspension medium, e.g. water, preferably that used for washing the sediments of previous workings and containing about 4 per cent of suspended material, giving a sol containing about 12 per cent of solids, after sedimentation.  This suspension is used for washing the same amount of fresh treated material, thus giving a sol containing about 28 per cent of suspended material.  By repetition of this procedure, sols containing up to 40 per cent of suspended material can be obtained.  Suitable apparatus comprises a series of rollers slightly spaced apart, each roller rotating at a greater peripheral speed than the roller preceding it in the series, and the spacing between successive rollers being reduced proportionately to the difference in peripheral speed between each successive pair of rollers.  Means are provided for feeding the material on to the first roll and removing it from the last, and a number of such series of rollers may be used, through which the paste is fed in succession, and in which the spacing between the rolls is progressively reduced from series to series.  According to an example, a mixture of sulphur, gum arabic and water in the proportions of 8 : 1 : 1 is treated in an ordinary mixer to obtain a stiff crumbly paste.  This paste is fed into a machine consisting of four series of rollers, each series containing three rollers rotating at 10, 30 and 90 r.p.m. respectively.  The spacing throughout the whole series is reduced progressively from 24/1000 in. to 2/1000 in.  The final paste is treated with water as previously described.ALSO:In a process for reducing solids to the colloidal state, the powdered material is mixed with a colloid and sufficient of the suspension medium to form a stiff and adhesive paste.  The paste is then passed through a series of rollers, slightly spaced apart, each roller rotating at a greater peripheral speed than the roller preceding it in the series, and the spacing between successive rollers being reduced proportionately to the difference in peripheral speed between each successive pair of rollers.  Means are provided for feeding the material on to the first roll, and removing it from the last, e.g. a shallow V-shaped stripping knife, and a number of such series of rollers may be used, through which the paste is fed in succession, and in which the spacing between the rollers is progressively reduced from series to series.  According to an example, a mixture of sulphur, gum arabic and water in the proportions of 8 : 1 : 1 is treated in an ordinary mixer to obtain a stiff crumbly paste.  This paste is fed into a machine consisting of four series of rollers, each series containing three rollers rotating at 10, 30 and 90 r.p.m. respectively.  The spacing throughout the whole series is reduced progressively from 24/1000 in. to 2/1000 in.  The final paste is treated with water.