Method for treating bleached lignin containing cellulose pulp by reducing .alpha.-carbonyl and .gamma.-carbonyl groups and converting short-wave quanta to long-wave light quanta

Abstract

A method for treating lignin containing pulp, subsequent to being bleached by: a) always treated with at least one chemical, which chemically reduces .alpha.-carbonyl and .gamma.-carbonyl groups in the lignin; and in at least one further step is b) treated with at least one chemical, which will block the phenolic hydroxyl groups of the lignin and/or c) supplied with at least one chemical, which will convert short-wave light quanta to long-wave light quanta. According to a preferred embodiment of the invention cellulose pulp is subjected to all of the above treatment processes, i.e. a)+b)+c) and is washed after the two initial treatment stages. The method solves the problem of yellowing of lignin containing pulps, e.g. high yield pulp.

Dependencies are inferred from the claim text.