GB841429A - Chemical lignocellulose pulping process and product - Google Patents

Abstract

<PICT:0841429/IV(a)/1> Pentosan-containing lignocellulose material is pulped by cooking with a 1 to less than 5% aqueous solution of a hydrotropic compound selected from benzoic acid, salicylic acid, xylenesulphonic acid, phenolsulphonic acid, toluenesulphonic acid, their alkali-metal salts and alkaline-earth metal salts and acidified solutions of these salts, until a substantial amount of the pentosans is removed. The solutions are stated to dissolve pentosans, leaving lignin largely unaffected. Cooking may be carried out at about 100 DEG C. until from 1/3 -\ba1/2 the pentosans have been removed, but the process may also be effected at increased pressures and higher temperatures. Cooking times may be about 1 hour under increased pressure, or from 1-5 hours at atmospheric pressure. When increased pressure is used, vapour may be condensed and returned to the reaction vessel. Preferred conditions comprise the use of bagasse or wood as raw material and extraction with sodium xylenesulphonate solution for some hours at 95-100 DEG C. Continuous operation may be employed, using the apparatus showing and adding dilute cooking solution continuously to make up for solution losses. Raw material is fed from tank 10 into the reaction vessel 1, which contains heated cooking solution, and the treated pulp is conveyed, by the belt 5 and funnel 9 to a conventional refiner 16. Refined pulp is pumped as a slush by pump 17 to screw press 19, where cooking liquor is separated and returned via pump 20 and pipes 21 to reaction vessel 1. Pulp passed through pipe 22 is water-washed in washer 23, washings being pumped via pump 24 and pipes 25, 21 back to reaction vessel 1, and pulp passes through pipe 27 to be again refined in refiner 26. Refined pulp is stored in tank 29, and if necessary may be bleached in conventional apparatus 31, 33. Pulp prepared by the process described is stated to have physical properties similar to sulphite or sulphate pulps but to have a high opacity similar to that of groundwood pulp and not to discolour on exposure to ultraviolet light. Specification 560,492 is referred to.