US4294653A
Expired / Lapsed
US
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Process for manufacturing chemimechanical cellulose pulp in a high yield within the range from 65 to 95%
Assignee: Mo och Domsjo AB
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Filing: 1978-04-11
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Granted: 1981-10-13
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Expires: 1998-04-11
Abstract
Abstract A process is provided for the manufacture of bleached chemimechanical cellulose pulp in high yield of between 65 and 95% from particulate and preferably washed lignocellulosic material, such as wood chips, featuring the use of spent or waste bleaching liquid, preferably from a lignin-preserving bleaching process, in at least one stage of the process where a cooling and diluting liquid is required, such as during mechanical defibration of the material.
Inventors
- 👤 Jonas A. I. Lindahl
- 👤 Lars G. Rudstrom
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 08:39
CPC Classifications
D; D21; D21C; D21C3/00; D21C3/22; D21B; D21B1/00; D21B1/04; D21B1/12; D21B1/14; D21B1/16
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
110 words
In the process for the manufacture of chemimechanical cellulose pulp in high yields within the range from about 65 to about 95% from particulate lignocellulosic material which comprises subjecting particulate lignocellulosic material to a mild partial digestion in the presence of a delignifying agent, and then mechanically defibrating the partially digested material, the improvement which comprises blending the partially digested lignocellulosic material after it has been defibrated to within the range from about 27 to about 44% of completion with waste bleaching liquor from a lignin-preserving bleaching process cooled to a temperature not exceeding 40° C.; and then completing the defibration to obtain a pulp of improved brightness and strength.
Claim 2
Dependent Claim
110 words
In the process for the manufacture of chemimechanical cellulose pulp in high yields within the range from about 65 to about 95% from particulate lignocellulosic material which comprises subjecting particulate lignocellulosic material to a mild partial digestion in the presence of a delignifying agent, and then mechanically defibrating the partially digested material, the improvement which comprises blending the partially digested lignocellulosic material after it has been defibrated to within the range from about 27 to about 44% of completion with waste bleaching liquor from a lignin-preserving bleaching process cooled to a temperature not exceeding 40° C.; and then completing the defibration to obtain a pulp of improved brightness and strength.
Claim 3
Dependent Claim
33 words
A process according to claim 1, in which the waste bleaching liquor is recycled lignin-preserving bleaching liquor from bleaching of chemimechanical cellulose pulp obtained from lignocellulosic material in the same chemimechanical manufacturing process.
Claim 4
Dependent Claim
25 words
A process according to claim 1, in which the bleaching liquor is added for cooling and dilution to a partially defibrated pulp suspension during defibration.
Claim 5
Dependent Claim
23 words
A process according to claim 3, wherein the waste bleaching liquor used as the diluting and cooling liquid also comprises fresh bleaching chemicals.
Claim 6
Dependent Claim
27 words
A process according to claim 1, in which aqueous defibrated pulp suspension obtained thereby is washed, screened and dewatered, and the dewatered cellulosic pulp is then bleached.
Claim 7
Dependent Claim
31 words
A process according to claim 5, in which the bleached pulp is dewatered in a second dewatering stage, and then bleached in a second bleaching stage performed with reducing bleaching agents.
Claim 8
Dependent Claim
25 words
A process according to claim 6, which comprises recovering the reducing waste bleaching liquor by passing said waste liquor directly to a chemicals recovery plant.
Claim 9
Dependent Claim
44 words
A process according to claim 1, wherein the defibrated pulp obtained thereby is bleached with a bleaching agent selected from the group consisting of hydrogen peroxide, sodium peroxide, peracetic acid, sodium dithionite, sulfur dioxide, sodium bisulfite, sodium sulfite, hydroxylamine, hydrazine, thiourea, and thioglycolic acid.
Claim 10
Dependent Claim
48 words
A process according to claim 1, in which the waste bleaching liquor is from a bleaching process where the bleaching agent is selected from the group consisting of hydrogen peroxide, sodium peroxide, peracetic acid, sodium dithionite, sulfur dioxide, sodium bisulfite, sodium sulfite, hydroxylamine, hydrazine, thiourea, and thioglycolic acid.
Claim 11
Dependent Claim
17 words
A process according to claim 9, in which the waste bleaching liquor is a peroxide bleaching liquor.
Claim 12
Dependent Claim
17 words
A process according to claim 9, in which the waste bleaching liquor is a dithionite bleaching liquor.
Claim 13
Dependent Claim
24 words
A process according to claim 1, in which the waste bleaching liquor has a pH within the range from about 6 to about 12.
Claim 14
Dependent Claim
27 words
A process according to claim 1, in which the lignocellulosic material is heated with steam prior to being defibrated in the presence of the waste bleaching liquor.
Claim 15
Dependent Claim
26 words
A process according to claim 1, wherein the waste bleaching liquor is mixed with a pH-adjusting solution prior to the blending with the particulate lignocellulosic material.
Claim 16
Dependent Claim
31 words
A process according to claim 1, which comprises recovering waste bleaching liquor from a bleaching stage, and recycling the waste bleaching liquor to the blending with the treated particulate lignocellulosic material.
Claim 17
Dependent Claim
15 words
A process according to claim 1, which comprises adding complexing agents to the defibrated material.
Claim 18
Dependent Claim
26 words
A process according to claim 1, which comprises steam-moistening the particulate lignocellulosic material, steam-heating the material at a temperature about 100° C., prior to partial digestion.
Claim 19
Dependent Claim
51 words
A process according to claim 1, which comprises steam-moistening the particulate lignocellulosic material, steam-heating the material at a temperature above 100° C., and then defibrating the material, in two stages adding the waste bleaching liquor as diluting and cooling liquor to the material prior to or during the second defibration stage.
Claim 20
Dependent Claim
42 words
A process according to claim 1, in which the partially digested particulate lignocellulosic material is defibrated in the presence of said delignifying agent to form cellulose pulp in the presence of waste bleaching liquor cooled to a temperature not exceeding 40° C.
Claim 21
Dependent Claim
29 words
A process according to claim 19, in which the particulate lignocellulosic material is heated with steam to moisten the chips, impregnated with a cellulose delignifying chemical, and then digested.
Claim 22
Dependent Claim
26 words
A process according to claim 19, in which the defibrated pulp suspension is screened and dewatered, and the dewatered defibrated cellulose pulp material is then bleached.
Claim 23
Dependent Claim
22 words
A process according to claim 21, in which the bleaching liquor is from a lignin-preserving bleaching process using a peroxide bleaching agent.
Claim 24
Dependent Claim
30 words
A process according to claim 22, in which the bleached pulp is passed to a second dewatering stage, followed by a second bleaching stage performed with a reducing bleaching agent.
Claim 25
Dependent Claim
25 words
A process according to claim 23, which comprises recovering the reducing waste bleaching liquor by passing said waste liquor directly to the chemicals recovery plant.
Claim 26
Dependent Claim
44 words
A process according to claim 21, wherein the dewatered defibrated cellulose pulp is bleached with a bleaching agent selected from the group consisting of hydrogen peroxide, sodium peroxide, peracetic acid, sodium dithionite, sulfur dioxide, sodium bisulfite, sodium sulfite, hydroxylamine, hydrazine, thiourea, and thioglycolic acid.
Claim 27
Dependent Claim
29 words
A process according to claim 25, in which the bleached pulp is passed to a second dewatering stage, followed by a second bleaching stage performed with reducing bleaching agents.
Claim 28
Dependent Claim
24 words
A process according to claim 19, in which the waste bleaching liquor has a pH within the range from about 6 to about 12.
Claim 29
Dependent Claim
26 words
A process according to claim 19, in which the lignocellulosic material is heated with steam and then defibrated in the presence of the waste bleaching liquor.
Claim 30
Dependent Claim
13 words
A process according to claim 28, in which the defibrated material is screened.
Claim 31
Dependent Claim
21 words
A process according to claim 28, wherein the waste bleaching liquor is mixed with a pH-adjusting solution prior to the blending.
Claim 32
Dependent Claim
33 words
A process according to claim 19, in which the cellulose delignifying chemical is selected from the group consisting of sodium bisulfite, sodium hydroxide, sodium carbonate and sodium bicarbonate, magnesium carbonate and magnesium bicarbonate.
Claim 33
Dependent Claim
61 words
A process according to claim 19, in which the mild digestion is effected at a temperature within the range from about 80° to about 180° l C., at a superatmospheric pressure within the range from 0 to 20 kp/cm 2 , and the digestion is continued until a Kappa number within the range from about 50 to about 150 is obtained.
Claim 34
Dependent Claim
45 words
A process according to claim 19, in which the defibration is effected in a disc refiner at a temperature within the range from about 80° to about 180° C. at a superatmospheric pressure within the range from about 0.5 to about 10 kp/cm 2 .
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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) | 1984-10-12 | 1985-04-13 | 1985-10-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-10-12 | 1989-04-13 | 1989-10-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-10-12 | 1993-04-13 | 1993-10-13 | $7700.00 | Window Closed / Lapsed |