ACETIC ACID PULPING OF STRAWS UNDER ATMOSPHERIC PRESSURE AND ACETIC ACID PULPING EFFECTIVELY UTILIZING WASTE LIQUORS

摘要

PROBLEM TO BE SOLVED: To obtain a pulp obtained by effectively pulping straws under the atmosheric pressure, having strength characteristics equal to those of pulps prepared according to a conventional method and excellent in quality, by adding an aqueous solution of acetic acid containing a catalytic amount of a mineral acid added thereto to cut straws and heating the resultant mixture. ;SOLUTION: An aqueous solution of acetic acid containing a catalytic amount of a mineral acid such as hydrochloric acid or sulfuric acid added thereto is added to cut straws and the resultant mixture is then heated to carry out the pulping of the straws under atmospheric pressure. An unbleached pulp is preferably bleached with a hypo (a hypochlorite) and oxygen- chlorine dioxide-hydrogen peroxide, etc., to produce a bleached pulp and the straws are pulped with acetic acid under atmospheric pressure. The resultant digested liquor is separated into the pulp and a waste liquor. The mineral acid in the waste liquor is then neutralized with an alkali to distill the aqueous solution of the acetic acid for use in washing of the pulp. The pulp is subsequently washed with hot water and warm water is added to the solid matter in the waste liquor and separated into a water-soluble part and a water-insoluble part. Saccharides are recovered from the water-soluble part and acetic acid lignin is recovered from the water-insoluble part. The acetic acid contained in the hot water wash liquid of the pulp is recovered with an ion exchange membrane, etc., and the acetic acid wash liquid of the pulp is preferably reused as a solvent for the acetic acid pulping method under the atmospheric pressure.;COPYRIGHT: (C)1999,JPO