US3769152A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Digestion of wood with oxygen in the presence of alkali
Assignee: Mo och Domsjo AB
•
Filing: 1971-02-26
•
Granted: 1973-10-30
•
Expires: 1991-02-26
Abstract
Abstract A process is provided for the production of cellulose of high brightness from wood by digestion with alkali and oxygen in aqueous solution under moderate oxygen pressure, limiting the amount of alkali at the start of the digestion to less than that required, and progressively adding alkali as the digestion continues, while maintaining the digestion liquor at a pH within the range from about 9.2 to about 13.
Inventors
- 👤 Hans Olof Samuelson
- 👤 Sture Erik Olof Noreus
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 16:51
CPC Classifications
D; D21; D21C; D21C3/00; D21C3/02; D21C3/026; D21C3/22; D21C3/26; D21C3/263
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
30 words
The process of claim 1, in which the amount of alkali is within the range from about 5 to about 20 percent of the total molar quantity of alkali required.
Claim 2
Dependent Claim
15 words
The process of claim 1, in which the alkali is added continuously during the digestion.
Claim 3
Dependent Claim
16 words
The process of claim 1, in which the aLkali is added in increments during the digestion.
Claim 4
Dependent Claim
19 words
The process of claim 1, in which the pH is within the range from about 9.5 to about 11.5.
Claim 5
Dependent Claim
33 words
The process of claim 1, in which pH is permitted to drop below 9, down to about 8, during the final stages of the process without seriously affecting the quality of the pulp.
Claim 6
Dependent Claim
29 words
The process of claim 1 in which the total amount of alkali is within the range from about 1 to about 10 kilomoles per 1,000 kg. of dry wood.
Claim 7
Dependent Claim
40 words
The process of claim 7, in which the cellulose pulp produced is a viscose, acetate or cuprammonium pulp, and the amount of alkali is within the range from about 6 to about 8 kilomoles per 1,000 kg. of dry wood.
Claim 8
Dependent Claim
37 words
The process of claim 7 in which the cellulose pulp produced is a semichemical pulp, and the amount of alkali is within the range from about 1 to about 2 kilomoles per 1,000 kg. of dry wood.
Claim 9
Dependent Claim
37 words
The process of claim 7, in which the cellulose pulp produced is a paper pulp, and the amount of alkali is within the range from about 2.5 to about 5 kilomoles per 1,000 kg. of dry wood.
Claim 10
Dependent Claim
50 words
The process of claim 7, in which the cellulose pulp produced is a pulp for use in making fine paper, plastic fillers, and soft paper or tissue paper, and the amount of alkali is within the range from about 2 to about 6 kilomoles per 1,000 kg. of dry wood.
Claim 11
Dependent Claim
18 words
The process of claim 1 in which the alkali is any alkali metal hydroxide or alkali metal carbonate.
Claim 12
Dependent Claim
14 words
The process of claim 12 in which the alkali metal hydroxide is sodium hydroxide.
Claim 13
Dependent Claim
14 words
The process of claim 12 in which the alkali metal carbonate is sodium carbonate.
Claim 14
Dependent Claim
30 words
The process of claim 1 in which the alkali is a mixture of alkali metal hydroxide or alkali metal carbonate with an alkali metal bicarbonate which serves as a buffer.
Claim 15
Dependent Claim
14 words
The process of claim 15 in which the alkali metal bicarbonate is sodium bicarbonate.
Claim 16
Dependent Claim
30 words
The process of claim 16 in which the amount of alkali metal bicarbonate is within the range from about 1 to about 5 kilomoles per 1,000 kg of dry wood.
Claim 17
Dependent Claim
36 words
The process of claim 1 in which the aqueous alkali includes a buffering agent which increases the buffer capacity of the digestion liquor, and assists in maintaining the pH within the prescribed range during the digestion.
Claim 18
Dependent Claim
20 words
The process of claim 18, in which the pH is maintained within the range from about 9.5 to about 9.7.
Claim 19
Dependent Claim
37 words
The process of claim 18, in which the buffering agent is a waste liquor selected from the group consisting of waste liquor from a previous alkaline oxygen digestion and waste liquor from an alkaline oxygen bleaching process.
Claim 20
Dependent Claim
32 words
The process of claim 1, in which the initial alkali charged comprises an alkali metal carbonate and the remainder of the alkali charged as the digestion proceeds is an alkali metal hydroxide.
Claim 21
Dependent Claim
17 words
The process of claim 21 in which the initial alkali charged also includes an alkali metal bicarbonate.
Claim 22
Dependent Claim
21 words
The process of claim 1, in which the alkali comprises a mixture of an alkali metal hydroxide and alkali metal carbonate.
Claim 23
Dependent Claim
20 words
The process of claim 1, in which the digestion temperature is within the range from about 90* to about 175*C.
Claim 24
Dependent Claim
30 words
The process of claim 1, in which, during the major portion of the digestion, the partial pressure of oxygen is within the range from about 3 to about 12 atmospheres.
Claim 25
Dependent Claim
20 words
The process of claim 1, in which the aqueous alkali comprises an inhibitor inhibiting attack on the hemicellulose and cellulose.
Claim 26
Dependent Claim
13 words
The process of claim 26, in which the inhibitor is a magnesium compound.
Claim 27
Dependent Claim
41 words
The process of claim 27, in which the magnesium compound is a magnesium complex selected from the group consisting of an inorganic or organic acid complex of polyhydroxy acids, organic acids containing at least two carboxylic acid groups, and polyphosphoric acids.
Claim 28
Dependent Claim
20 words
The process of claim 28, in which the organic acid is an aliphatic Alpha - or Beta -hydroxy carboxylic acid.
Claim 29
Dependent Claim
18 words
The process of claim 26, in which the inhibitor is an alkali-soluble silicic acid or alkali metal silicate.
Claim 30
Dependent Claim
24 words
The process of claim 1, in which the wood is pretreated with water or an aqueous acidic, neutral or alkaline solution before the digestion.
Claim 31
Dependent Claim
27 words
The process of claim 31, in which the aqueous solution comprises a sulfite precursor selected from sulphur dioxide, an alkali metal bisulphite, or an alkali metal sulphite.
Claim 32
Dependent Claim
28 words
The process of claim 31, in which the pretreatment is carried out in the presence of a complexing agent for bivalent and or polyvalent ions of transition metals.
Claim 33
Dependent Claim
21 words
The process of claim 1, in which a surface-active substance is present during at least a part of the digestion process.
Claim 34
Dependent Claim
22 words
The process of claim 1, in which the wood is a hardwood selected from birch, beech, poplar, aspen, maple, alder and eucalyptus.
Claim 35
Dependent Claim
24 words
The process of claim 1, in which the wood is in the form of particles having an average thickness of at most 3 mm.
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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) | 1976-10-29 | 1977-04-30 | 1977-10-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-29 | 1981-04-30 | 1981-10-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-29 | 1985-04-30 | 1985-10-30 | $7700.00 | Window Closed / Lapsed |