Patent GB-1011844-A (GB)
Title: Process for the improvement of physical properties of cellulosic materials
IPC: C08B31/18
Filed: 1964-03-25
Abstract: The invention comprises the reaction product of a dialdehyde polysaccharide with a water-soluble acidic salt of a metal of Group II, IV or VI of the Periodic System. An aqueous dispersion of such a reaction product is made by heating a mixture of dialdehyde polysaccharide and water, containing 1-30% by weight of the polysaccharide, to 60-95 DEG  C. for a time sufficient to ensure that no unruptured granules of polysaccharide remain, adding to the resulting dispersion the above metal salt in an amount of 2.5-100% based on the weight of the polysaccharide, and allowing the salt to react with the dialdehyde polysaccharide dispersion for 1-10 minutes at pH 2.0-4.0 and at 25-95 DEG  C. If necessary, the pH of the dialdehyde polysaccharide dispersion may be lowered before reaction with the metal salt by adding, e.g. hydrochloric, sulphuric or formic acid. The dispersion and heating of the dialdehyde polysaccharide in water may be effected in presence of a buffer such as sodium acetate, sodium citrate, mono-sodium phosphate, borax or sodium hexametaphosphate. Specified dialdehyde polysaccharides are penodate-oxidized starches, amylose, amylopectin, cellulose, gums, dextrans, algin and inulin.  Specified water-soluble acidic salts are salts of zinc, strontium, tin, chromium and zirconium, e.g. chlorides and sulphates.  The reaction products are cationic hydrophilic colloids in which the metal salt is complexed with the dialdehyde polysaccharide. A dispersion of such a reaction product is added to an aqueous slurry of cellulosic material in the paper-making process to improve the strength of the paper (see Division D2).ALSO:An aqueous dispersion of a reaction product of a dialdehyde polysaccharide with a water-soluble acidic salt of a Group II, IV or VI metal is added to an aqueous slurry of cellulosic material to improve the physical properties thereof.  The polysaccharide-salt reaction products are cationic hydrophilic colloids and they improve the wet and dry strengths of cellulosic webs formed in paper-making operations.  The dialdehyde polysaccharide may be derived from starches, inulin, cellulose dextram, algin gums, and the salt with which it is reacted may be e.g. chlorides or sulphates of zirconium, tin, strontium, chromium or zinc.  In the paper-making process the aqueous dispersion of the polysaccharide-salt reaction product may be added to a pulp slurry at any point at the wet end of the machine, or from a tub size, size press or from showers on to a dried or partially dried sheet, in an amount of 0.05-10% by weight based on oven-dry pulp.  A large number of natural cellulosic fibres are specified.  In an example, an aqueous dispersion of dialdehyde starch-zerconium chloride complex is added to a 1% aqueous slurry of bleached Kraft pulp at pH 4.5-5.5, in proportions of 0.2-0.5% of salt based on the pulp.  Samples of treated slurry are added to a pre-filled Deckle box of a Noble and Wood sheet machine.  The water used to fill the box is adjusted to pH 4.5-5.5.  A sheet is formed using a white water return system, and the sheet is pressed and dried at 220 DEG F. during a 3-minute cycle on the steam heated dryer of the sheet machine.