EP0018287B1
Expired / Lapsed
EP
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Process for the delignification of unbleached chemical paper pulp
Assignee: LA CELLULOSE DES ARDENNES
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Filing: 1980-04-16
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Granted: 1983-01-12
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Expires: 2000-04-16
Abstract
No abstract record available.
Inventors
- 👤 Jacques Carles
- 👤 Henri Lemoyne
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 03:55
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/10; D21C9/16; D21C9/163
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
134 words
A process for the delignification of unbleached chemical wood pulp characterized in that it comprises the combination of the following steps: a) a step of oxidation of the unbleached pulp with a peroxide, in an alkaline medium with a % peroxide/pulp ratio with respect to the Kappa index of said pulp of from 0.01 to 0.1, and with a pH kept at a value of from 9 to 12, the said oxidation being followed by b) a step of mechanical pressing of the oxidized pulp with recycling of the extraction effluents from the pressing step, - partly upstream the oxidation step, - partly downstream the oxidation step with a view to ensure the prior dilution of the pulp oxidized before the pressing, - and if necessary partly towards the wash of the unbleached pulp.
Claim 2
Dependent Claim
134 words
A process for the delignification of unbleached chemical wood pulp characterized in that it comprises the combination of the following steps: a) a step of oxidation of the unbleached pulp with a peroxide, in an alkaline medium with a % peroxide/pulp ratio with respect to the Kappa index of said pulp of from 0.01 to 0.1, and with a pH kept at a value of from 9 to 12, the said oxidation being followed by b) a step of mechanical pressing of the oxidized pulp with recycling of the extraction effluents from the pressing step, - partly upstream the oxidation step, - partly downstream the oxidation step with a view to ensure the prior dilution of the pulp oxidized before the pressing, - and if necessary partly towards the wash of the unbleached pulp.
Claim 3
Dependent Claim
40 words
The process of claim 1, characterized in that the mechanical pressing of the oxidized pulp is conducted in such a way as to obtain a squeezing of the pulp corresponding to a pulp concentration or density of 10 to 60%.
Claim 4
Dependent Claim
42 words
The process of claim 1 or 2, characterized in that the prior dilution of the pulp oxidized before the pressing is adjusted in such a way as to obtain a pulp concentration of from 1 to 5% by weight immediately before pressing.
Claim 5
Dependent Claim
51 words
The process of claim 1, 2 or 3, characterized in that the recycling of part of the extraction effluents from the pressing step upstream of the oxidation step is adjusted so as to obtain a quantity of dissolved materials of from 0.5% to 5% by weight with respect to the pulp.
Claim 6
Dependent Claim
27 words
The process of claim 1, 2, 3 or 4, characterized in that immediately after pressing, the juices contained in the pulp are moved by a washing liquor.
Claim 7
Dependent Claim
25 words
The process of claim 1, characterized in that the oxidation of the unbleached pulp is conducted with hydrogen peroxide in the presence of sodium hydroxide.
Claim 8
Dependent Claim
23 words
The process of claim 1 or 6, characterized in that the duration of the oxidation step is from 10 minutes to 5 hours.
Claim 9
Dependent Claim
21 words
The process of claim 1 or 6, characterized in that the temperature is from 40 to 95°C during the oxidation step.
Claim 10
Dependent Claim
20 words
The process of claim 2, characterized in that the pulp concentration or density after pressing is from 30 to 40%.
Claim 11
Dependent Claim
24 words
The process of claim 8, characterized in that the oxidation of the unbleached pulp is conducted at a temperature of from 70 to 90°C.
Claim 12
Dependent Claim
21 words
The process of claim 7, characterized in that the duration of the oxidation step is from 20 minutes to 3 hours.
Claim 13
Dependent Claim
20 words
The process of claim 1, characterized in that the pH is kept at 10 to 11 in the oxidation step.
Claim 14
Dependent Claim
25 words
The process of claim 1, characterized in that the oxidized, pressed and if necessary washed pulp, is subjected to a sequence of subsequent bleaching operations.
Claim 15
Dependent Claim
61 words
The process of claim 1, characterized in that during the oxidation step a slight overpressure is kept in the column of pulp compared with the atmospheric pressure and with the pressure of the steam of the liquid phase of the pulp to be treated, the said overpressure being limited to a value below or equal to 2 kg/cm 2 (2 bars).
Claim 16
Dependent Claim
27 words
The process of claim 14, characterized in that the said overpressure is limited to a value of from 100 to 500 g/cm 2 (0,1 to 0,5 bar).
Claim 17
Dependent Claim
23 words
The process of claim 14, characterized in that the oxidation step is conducted in a closed reactor inside which the pulp progresses downwards.
Claim 18
Dependent Claim
23 words
The process of claim 14, characterized in that the oxidation stage is conducted in a closed reactor inside which the pulp progresses upwards.
Claim 19
Dependent Claim
20 words
The process of any one of the preceding claims characterized in that the unbleached chemical pulp is an unbleached Kraftpulp.
References Cited (Backward Citations)
No citation records indexed.
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