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US 4,729,817 AGranted
Process for the oxidative delignification of demethylated chemical pulp
AssigneeTenneco Canada Inc. (ERCO division)
InventorsRaymond C. Francis, Douglas W. Reeve
Life of this patent
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Abstract
The extent of delignification of chemical pulps by oxygen-containing chemicals, preferably hydrogen peroxide, is enhanced by demethylating the pulp prior to such oxidative delignification, to a degree of demethylation of at least about 30%, preferably at least about 50%. Demethylation may be achieved by chemical treatment of the already-formed pulp or by modification to the pulping process to result in demethylated pulp.
Claims5
A process for the oxidative delignification of chemical pulp, which comprises:
- forming a chemical pulp containing about 2 to about 6 wt. % of lignin from wood by a kraft process, a soda process or a sulphite process,
- chemically demethylating the lignin content of said chemical pulp with an electron-deficient compound selected from the group consisting of aluminum chloride, boron tribromide and trimethylsilyl iodide or a nucleophile selected from the group consisting of organic and inorganic sulfides, reagents containing thiosulfate, sulfite, iodide, bromide or chloride ions, and phosphides, without effecting any substantial delignification of said chemical pulp during said chemical demethylation of the lignin so as to provide lignin in said chemical pulp with a degree of demethylation of at least about 30%, and thereafter
- subjecting said demethylated pulp to oxidative delignification by contact with an oxidative delignification agent.
A process of forming delignified chemical wood pulp, which comprises:
- forming a chemical wood pulp having a lignin content of about 2 to about 6 wt. % by pulping wood using pulping chemicals,
- chemically demethylating the lignin content of said pulp without effecting any substantial delignification of the pulp using an electro-deficient compound or a nucleophile to a degree of demethylation of at least about 30%, and
- oxidatively delignifying said chemical wood pulp using an oxidative delignification agent selected from the group consisting of hydrogen peroxide, molecular oxygen, chlorine dioxide and peracetic acid.
Dependencies are inferred from the claim text.