EP0402335A2
Expired / Lapsed
EP
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Process for bleaching lignocellulose-containing pulps
Assignee: Nouryon Pulp and Performance Chemicals AB
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Filing: 1990-05-21
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Granted: —
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Expires: 2010-05-21
Abstract
Abstract The invention relates to a process for bleaching chemically delignified lignocellulose-containing pulp, to render more efficient a peroxide-containing treatment stage, by treating the pulp with a complexing agent before the peroxide step, so that the trace metal profile of the pulp is altered by the treatment with the complexing agent, in the absence of sulphite, at a pH in the range from 3.1 up to 9.0 and at a temperature in the range from 10°C up to 100°C, whereupon, in a subsequent step, the treatment with a peroxide-containing substance is carried out at a pH in the range from 7 up to 13, said two-step treatment being carried out at an optional position in the bleaching sequence applied to the pulp.
Inventors
- 👤 Per G. Lundgren
- 👤 Lillemor K. Holtinger
- 👤 Jiri J. Basta
- 👤 Marie R. Samuelsson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 06:19
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/10; D21C9/147; D21C9/1026; D21C9/1042; D21C9/1057; D21C9/16; D21C9/163
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
118 words
A process for bleaching chemically delignified lignocellulose-containing pulp, adapted to render more efficient a peroxide-containing treatment step, by treating the pulp with a complexing agent before the peroxide step, characterised in that the trace metal profile of the pulp is altered by treatment with a complexing agent, there being no sulphite present, at a pH in the range from 3.1 up to 9.0 and at a temperature in the range from 10°C up to 100°C, whereupon, in a subsequent step, the treatment with a peroxide-containing substance is carried out at a pH in the range from 7 up to 13, this two-step treatment being carried out at an optional position in the bleaching sequence applied to the pulp.
Claim 2
Dependent Claim
118 words
A process for bleaching chemically delignified lignocellulose-containing pulp, adapted to render more efficient a peroxide-containing treatment step, by treating the pulp with a complexing agent before the peroxide step, characterised in that the trace metal profile of the pulp is altered by treatment with a complexing agent, there being no sulphite present, at a pH in the range from 3.1 up to 9.0 and at a temperature in the range from 10°C up to 100°C, whereupon, in a subsequent step, the treatment with a peroxide-containing substance is carried out at a pH in the range from 7 up to 13, this two-step treatment being carried out at an optional position in the bleaching sequence applied to the pulp.
Claim 3
Dependent Claim
20 words
A process according to claim 1, characterised in that the bleaching sequence applied to the pulp comprises an oxygen stage.
Claim 4
Dependent Claim
19 words
A process according to claim 2, characterised in that said two-step treatment is carried out after the oxygen stage.
Claim 5
Dependent Claim
23 words
A process according to claims 1-3, characterised in that the first treatment step is carried out at a pH from 4 to 8.
Claim 6
Dependent Claim
23 words
A process according to claim 4, characterised in that the first treatment step is carried out at a pH from 6 to 7.
Claim 7
Dependent Claim
20 words
A process according to claims 1-3, characterised in that said two-step treatment is carried out with an intermediate washing step.
Claim 8
Dependent Claim
24 words
A process according to claim 1, characterised in that the complexing agent is a nitrogenous polycarboxylic acid, or a phosphonic acid, or a polyphosphate.
Claim 9
Dependent Claim
20 words
A process according to claim 7, characterised in that the complexing agent is diethylenetriaminepentaacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA).
Claim 10
Dependent Claim
21 words
A process according to claim 1, charac terised in that the peroxide-containing substance is hydrogen peroxide or hydrogen peroxide + oxygen.
Claim 11
Dependent Claim
26 words
A process according to claims 1-3, characterised in that the pulp, after said two-step treatment, is subjected to a final bleaching to obtain the desired brightness.
Claim 12
Dependent Claim
68 words
A process according to claims 1-10, characterised in that the first step of said two-step treatment is carried out at a temperature of from 26 to 100°C during from 1 to 360 min., and that the second step is carried out at a temperature of from 50 to 130°C during from 5 to 960 min., the treated pulp having a concentration of from 1 to 40% by weight.
References Cited (Backward Citations)
No citation records indexed.
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