US3867246A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Chlorine-free multiple step bleaching of cellulose
Assignee: Evonik Operations GmbH
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Filing: 1973-04-16
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Granted: 1975-02-18
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Expires: 1993-04-16
Abstract
Abstract Cellulose is bleached in the absence of chlorine in an aqueous medium in a plural of steps including (1) employing an inorganic or organic peroxide or hydroperoxide under alkaline conditions, (2) an organic percarboxylic acid or water soluble salt thereof under acid conditions and (3) an inorganic or organic peroxide or hydroperoxide under alkaline conditions again. An acid pretreatment can be employed.
Inventors
- 👤 Gerhard Hebbel
- 👤 Horst Kruger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 07:22
CPC Classifications
D; D21; D21C; D21C9/00; D21C9/10; D21C9/16
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
76 words
A PLURAL STEP PROCESS FOR THE CHLORINE FREE BLEACHING OF CELLULOSE IN AN AQUEOUS MEDIUM COMPRISING BLEACHING IN A FIRST STEP WITH A PEROXIDE OR HYDROPEROXIDE UNDER ALKALINE CONDITIONS WHEREIN THE PH IS 8-13, THEN IN A SECOND STEP WITH A PERCARBOXYLIC ACID OR WATER SOLUBLE SALT THEREOF UNDER ACID CONDITIONS WHEREIN THE PH IS 4.5-6.5 AND THEN IN A THIRD STEP AGAIN WITH A PEROXIDE OR HYDROPEROXIDE UNDER ALKALINE CONDITIONS WHEREIN THE PH IS 8-13.
Claim 2
Dependent Claim
76 words
A PLURAL STEP PROCESS FOR THE CHLORINE FREE BLEACHING OF CELLULOSE IN AN AQUEOUS MEDIUM COMPRISING BLEACHING IN A FIRST STEP WITH A PEROXIDE OR HYDROPEROXIDE UNDER ALKALINE CONDITIONS WHEREIN THE PH IS 8-13, THEN IN A SECOND STEP WITH A PERCARBOXYLIC ACID OR WATER SOLUBLE SALT THEREOF UNDER ACID CONDITIONS WHEREIN THE PH IS 4.5-6.5 AND THEN IN A THIRD STEP AGAIN WITH A PEROXIDE OR HYDROPEROXIDE UNDER ALKALINE CONDITIONS WHEREIN THE PH IS 8-13.
Claim 3
Dependent Claim
22 words
A process according to claim 1 including the step of treating the cellulose with an acid prior to the first bleaching step.
Claim 4
Dependent Claim
44 words
A process according to claim 1 wherein the peroxide or hydroperoxide is hydrogen peroxide, sodium peroxide or t-butyl hydroperoxide and the percarboxylic acid or salt thereof is a peralkanoic acid of 2 to 5 carbon atoms or percarbonic acid or water soluble salt thereof.
Claim 5
Dependent Claim
24 words
A process according to claim 3 wherein the peralkanoic acid or salt thereof is peracetic acid, perpropionic acid or a salt of such acid.
Claim 6
Dependent Claim
69 words
A process according to claim 4 wherein the amount of peroxide or hydroperoxide is 0.5 - 6.0% by weight calculated as 100% hydrogen peroxide and based on the oven dried weight of the cellulose employed and the amount of peralkanoic acid or percarbonic acid or salt thereof is 0.5 - 3.0% by weight calculated as 100% hydrogen peroxide and based on the oven dried weight of the cellulose employed.
Claim 7
Dependent Claim
28 words
A process according to claim 5 wherein the bleaching in each step is carried out between 40*C. and the boiling point of the bleach liquor at atmospheric pressure.
Claim 8
Dependent Claim
19 words
A process according to claim 1 wherein the bleaching in each step is carried out between 20*C. and 140*C.
Claim 9
Dependent Claim
26 words
A process according to claim 7 wherein the total water employed in the process is 10 to 40 times the weight of cellulose to be bleached.
Claim 10
Dependent Claim
24 words
A process according to claim 8 wherein dilution water from the second or any subsequent bleaching step is returned to a preceding bleaching step.
Claim 11
Dependent Claim
30 words
A process according to claim 1 wherein the peroxide or hydroperoxide is hydrogen peroxide or sodium peroxide and the percarboxylic acid is peracetic acid or perpropionic acid or percarbonic acid.
Claim 12
Dependent Claim
40 words
A process according to claim 1 wherein the peroxide or hydroperoxide is hydrogen peroxide, sodium peroxide or t-butyl hydroperoxide and the percarboxylic or salt thereof is a peralkanoic acid of 2 to 5 carbon atoms or water soluble salt thereof.
Claim 13
Dependent Claim
24 words
A process according to claim 11 wherein the peralkanoic acid or salt thereof is peracetic acid, perpropionic acid or a salt of such acid.
Claim 14
Dependent Claim
66 words
A process according to claim 12 wherein the amount of peroxide or hydroperoxide is 0.5 - 6.0% by weight calculated as 100% hydrogen peroxide and based on the oven dried weight of the cellulose employed and the amount of peralkanoic acid or salt thereof is 0.5 - 3.0% by weight calculated as 100% hydrogen peroxide and based on the oven dried weight of the cellulose employed.
Claim 15
Dependent Claim
27 words
A process according to claim 1 wherein the peroxide or hydroperoxide is hydrogen peroxide or sodium peroxide and the percarboxylic acid is peracetic acid or perpropionic acid.
Claim 16
Dependent Claim
14 words
A process according to claim 1 wherein the peroxide or hydroperoxide is hydrogen peroxide.
Claim 17
Dependent Claim
29 words
A process according to claim 15 wherein the percarboxylic acid or salt thereof is a peralkanoic acid of 2 to 5 carbon atoms or a water soluble salt thereof.
Claim 18
Dependent Claim
29 words
A process according to claim 1 wherein the percarboxylic acid or salt thereof is a peralkanoic acid of 2 to 5 carbon atoms or a water soluble salt thereof.
Claim 19
Dependent Claim
15 words
A process according to claim 17 terminating with an alkaline peroxide or hydroperoxide bleaching step.
Claim 20
Dependent Claim
38 words
A process according to claim 1 wherein there is employed difficultly bleachable cellulose and there is included a fourth step with a percarboxylic acid or water soluble salt thereof and a fifth step with alkaline peroxide or hydroperoxide.
Claim 21
Dependent Claim
14 words
A process according to claim 19 wherein the difficultly bleachable cellulose is sulfate cellulose.
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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) | 1978-02-17 | 1978-08-19 | 1979-02-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-17 | 1982-08-19 | 1983-02-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-17 | 1986-08-19 | 1987-02-18 | $7700.00 | Window Closed / Lapsed |