US3944463A
Expired / Lapsed
US
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Pulping of lignocellulosic material with oxygen in two stages at increasing pH
Assignee: Mo och Domsjo AB
•
Filing: 1973-12-12
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Granted: 1976-03-16
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Expires: 1993-12-12
Abstract
Abstract A process is provided for producing cellulose pulp of high brightness, which comprises pulping lignocellulosic material such as wood with oxygen under superatmospheric pressure in two stages, in the first at a pH within the range from about 6 to about 9, and in the second at a more alkaline pH of at least about 10.
Inventors
- 👤 Hans Olof Samuelson
- 👤 Leif Ake Smedman
- 👤 Erik Olof Sture Hagglund
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 03:52
CPC Classifications
D; D21; D21C; D21C3/00; D21C3/22; D21C3/26; D21C3/263
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
114 words
A process for preparing cellulose pulp which comprises pulping lignocellulosic material with oxygen under superatmospheric pressure in the presence of an alkaline compound in at least two oxygen pulping stages, in a first stage at a pH within the range from about 6 to about 9 and at a temperature within the range from about 110° to about 160° C; and in a second stage at a pH of at least about 10 and at a temperature within the range from about 80° to about 160° C; and continuing the pulping with oxygen under superatmospheric pressure at a temperature within the range from about 80° to about 160° C until cellulose pulp is obtained.
Claim 2
Dependent Claim
114 words
A process for preparing cellulose pulp which comprises pulping lignocellulosic material with oxygen under superatmospheric pressure in the presence of an alkaline compound in at least two oxygen pulping stages, in a first stage at a pH within the range from about 6 to about 9 and at a temperature within the range from about 110° to about 160° C; and in a second stage at a pH of at least about 10 and at a temperature within the range from about 80° to about 160° C; and continuing the pulping with oxygen under superatmospheric pressure at a temperature within the range from about 80° to about 160° C until cellulose pulp is obtained.
Claim 3
Dependent Claim
26 words
A process in accordance with claim 1 in which the alkaline compound is selected to allow pulping with oxygen at a pH within the stated range.
Claim 4
Dependent Claim
32 words
A process in accordance with claim 2 in which the alkaline compound is selected from the group consisting of alkali metal and alkaline earth metal carbonates, bicarbonates, and hydroxides, and mixtures thereof.
Claim 5
Dependent Claim
32 words
A process in accordance with claim 1 in which the amount of alkaline compound is within the range from about 1 to about 10 kilomoles per 1000 kg. of dry lignocellulosic material.
Claim 6
Dependent Claim
29 words
A process in accordance with claim 1 in which all of the alkali required for the pulping is added to the lignocellulosic material at the start of the process.
Claim 7
Dependent Claim
39 words
A process in accordance with claim 1 in which only a portion of the alkali required is added at the start of the process, and alkali is added to the system thereafter, in amounts to maintain the desired pH.
Claim 8
Dependent Claim
67 words
A process in accordance with claim 1, in which the oxygen pulping is preceded by a pretreatment of the lignocellulosic material with an aqueous liquor containing an alkaline compound at a temperature within the range from about 60° to about 200° C, until from about 5 to about 15% of the lignocellulosic material, based on the dry weight of the material, is dissolved in the pretreatment liquor.
Claim 9
Dependent Claim
33 words
A process in accordance with claim 7, in which the pH of the pretreatment liquor is within the range from about 6.5 to about 14 during the major portion of the pretreatment time.
Claim 10
Dependent Claim
38 words
A process according to claim 7 in which the pretreating liquor contains sodium carbonate, sodium bicarbonate or a mixture thereof, as the alkaline compound, and water or a spent pulping, bleaching or pretreating liquor as the aqueous phase.
Claim 11
Dependent Claim
55 words
A process in accordance with claim 7 in which spent pretreating liquor is separated from the lignocellulosic material before the oxygen pulping is begun, by washing out at least a part of the spent pretreating liquor from the pretreated lignocellulosic material with water or a waste oxygen pulping liquor derived from the oxygen pulping process.
Claim 12
Dependent Claim
51 words
A process in accordance with claim 1 in which in the first oxygen pulping stage the pH is at about 9 for the major portion, and is then allowed to decrease toward the lower end of the range during the remainder of the pulping time, thereby producing a low viscosity pulp.
Claim 13
Dependent Claim
38 words
A process in accordance with claim 1 in which in the first oxygen pulping stage the pH is within the range from about 6.5 to 8 during most of the pulping time, thereby producing a high viscosity pulp.
Claim 14
Dependent Claim
31 words
A process in accordance with claim 1 in which during the first oxygen pulping stage, the partial pressure of oxygen is within the range from about 3 to about 200 bars.
Claim 15
Dependent Claim
36 words
A process in accordance with claim 1 in which the partial pressure of oxygen during the first oxygen pulping stage is within the ragne from about 8 to about 50 bars, thereby producing a paper pulp.
Claim 16
Dependent Claim
31 words
A process in accordance with claim 1 in which the partial pressure of oxygen during the second oxygen pulping stage is within the range from about 1 to about 100 bars.
Claim 17
Dependent Claim
44 words
A process in accordance with claim 1, which includes washing first pulping liquor from the partially pulped cellulosic material from the first oxygen pulping stage and then contacting the partially pulped cellulosic material with a second pulping liquor for the second oxygen pulping stage.
Claim 18
Dependent Claim
23 words
A process in accordance with claim 16, in which the washing liquor is a spent pulping liquor from the second oxygen pulping stage.
Claim 19
Dependent Claim
30 words
A process in accordance with claim 1, in which the pulping is carried out in the presence of a degradation inhibitor which protects the cellulose and hemicellulose molecules against degradation.
Claim 20
Dependent Claim
24 words
A process in accordance with claim 18, in which the inhibitor is charged to the pulping liquor at an early stage of the pulping.
Claim 21
Dependent Claim
22 words
A process in accordance with claim 18, in which the inhibitor is added to a pretreatment liquor prior to the oxygen pulping.
Claim 22
Dependent Claim
23 words
A process in accordance with claim 18, in which the inhibitor is added to the oxygen pulping liquor before combination with lignocellulosic material.
Claim 23
Dependent Claim
15 words
A process in accordance with claim 18, in which the inhibitor is a magnesium compound.
Claim 24
Dependent Claim
15 words
A process in accordance with claim 1, in which the oxygen is pure oxygen gas.
Claim 25
Dependent Claim
18 words
A process in accordance with claim 1, in which the oxygen is in admixture with an inert gas.
Claim 26
Dependent Claim
27 words
A process in accordance with claim 1 in which carbon dioxide formed in the oxygen pulping at a pH from about 6 to about 9 is removed.
Claim 27
Dependent Claim
18 words
A process in accordance with claim 25 in which such carbon dioxide is absorbed in an alkaline liquid.
Claim 28
Dependent Claim
28 words
A process in accordance with claim 1 in which a peroxide is added to the pulping liquor during or at the end of the second oxygen pulping stage.
Claim 29
Dependent Claim
30 words
A process in accordance with claim 1 in which the superatmospheric pressure during the second oxygen pulping stage is less than the superatmospheric pressure in the first oxygen pulping stage.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-03-16 | 1979-09-15 | 1980-03-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-03-16 | 1983-09-15 | 1984-03-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-03-16 | 1987-09-15 | 1988-03-16 | $7700.00 | Window Closed / Lapsed |