Patent GB-723231-A (GB)
Title: Process for the manufacture of packing materials for sticky masses or masses which soften under the action of temperature, and for the treatment of the inner surfaces ofcasting moulds
IPC: B65D25/14
Filed: 1951-12-03
Abstract: A process for the preparation of packing materials made of paper, fibrous materials, woven fabrics, wood, metal and the like, for substances which are adhesive or which become soft or viscous under the effect of temperature, such as bitumens, tar products, resins, synthetic resins, waxes and the like, likewise for the treatment of casting moulds for such substances, comprises impregnating or coating the packing materials or moulds with an aqueous solution of a soluble alginic acid derivative and subsequently precipitating a layer of an insoluble alginic acid derivative in the presence of sufficient hygroscopic agent to make said layer suitable for the absorption of moisture. Preferably a 1/2 to 5 per cent. aqueous solution of an alkali metal salt or ammonium salt of alginic acid is used to coat or impregnate the material, and then the conversion of this coating or impregnating layer into an insoluble derivative is effected by treatment with gaseous or dissolved acids or preferably by alkaline earth metal or heavy metal salt solutions. A preferred precipitating agent is concentrated calcium chloride solution.  The coating and/or precipitating solution may have added to it water-soluble agents, e.g. glycerine, glycol, which absorb moisture, and water-soluble derivatives of cellulose, e.g. cellulose methyl ether and/or derivatives of starch or types of sugar, more especially hygroscopic derivatives.  Filling materials, e.g. ground fibrous material, paper powder, sawdust, and minerals such as silicates may be added to the coating solution, as also may metal powders having a reflecting action, e.g. aluminium powder or copper bronze.  A pigment or water-soluble dye may also be added to the coating solution.ALSO:A mould for casting substances which are adhesive or which become soft or viscous under the effect of temperature, such as bitumens, tar products, resins, synthetic resins or waxes, is impregnated or coated with an aqueous solution of a soluble alginic acid derivative and subsequently a layer of an insoluble alginic acid derivative is precipitated therefrom in the presence of sufficient hygroscopic agent to make said layer suitable for the absorption of moisture. Preferably a 1/2 -5 per cent. aqueous solution of an alkali metal salt or ammonium salt of alginic acid is used to coat or impregnate the mould, and then the conversion of this coating or impregnating layer into an insoluble derivative is effected by treatment with gaseous or dissolved acids or preferably by alkaline earth metal or heavy metal salt solution.  A preferred precipitating agent is concentrated calcium chloride solution.  The coating and/or precipitating solution may have added to it water soluble agents, e.g. glycerine, glycol, which absorb moisture, and water soluble derivatives of cellulose, e.g. cellulose methyl ether and/or derivatives of starch or types of sugar, especially hygroscopic derivatives. Filling materials, e.g. ground fibrous material, paper powder, sawdust, and minerals such as silicates may be added to the coating solution as also may metal powders having a reflecting action, e.g. aluminium powder or copper bronze.  A pigment or water soluble dye may also be added to the coating solution.