Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Treatment with particular chemical
Patent
1982-06-11
1987-03-24
Corbin, Arthur L.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Treatment with particular chemical
162 81, 162 90, D21C 304
Patent
active
046523413
ABSTRACT:
A process of treating fibrous ligno-cellulose material to form defibered chemical cellulose pulp suitable, for example, for the manufacture of paper and paperboard and dissolving pulp and to treat defibered ligno-cellulose material to produce basic animal feed or packaging and building boards.
The process is based on the nitration and dissolving of the lignin component of the cellulose material either in an alkaline solution or with a two step operation in which the nitration can be in an acid stage comprising the step of submerging the fiberous ligno-cellulosic material in aqueous nitric acid having an HNO.sub.3 concentration in the range of about 0.125 to 9 weight percent, followed by an alkaline stage to dissolve out the nitrated lignin from the fibrous structure. In the production of chemical pulp or animal feed the lignin containing solution (black liquor) is separated from the cellulose material.
The time required for nitration is substantially shortened by including in the nitrating solution aluminum compounds, e.g., aluminum salts of inorganic acids such as aluminum sulfate, aluminum chloride, aluminum phosphate or aluminum nitrate, preferably aluminum sulphate, i.e., papermaker's alum, in an amount sufficient to achieve an equivalent aluminum ion concentration in the pulping liquor, preferably about 0.065 to 0.105 parts by weight of aluminum sulphate for each 10 parts by weight of nitrate ion in the nitrating solution.
The nitrating liquor including wash water, either acid or alkaline, can be recycled to nitrating chemical exhaustion. Lignin-containing extraction liquor is recycled to build up the percentage of lignin solids and systematically purged. Part or all of the ligneous component may be recombined with the cellulosic pulp produced with which it acts as a retention agent, binder, water repellant and stiffening agent. In combination with defibered ligno-cellulosic materials its function is as a binder and hydrophilic material.
For grassy, fibrous ligno-cellulosic materials (i.e., straw) nitrate salts such as the alkali salts NaNO.sub.3, KNO.sub.3, or NH.sub.4 NO.sub.3, which have a relatively lower ionizing factor than nitric acid, can be used in an alkaline solution to nitrate and dissolve the ligneous component. The use of nitrates in an alkaline solution for woody fibrous materials (i.e., spruce wood chips) requires additional pulping time than if an aggressive acid nitrate source is used for nitration.
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