US3865685A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multiple step bleaching of cellulose with a per compound and chloride dioxide
Assignee: Evonik Operations GmbH
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Filing: 1973-04-16
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Granted: 1975-02-11
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Expires: 1993-04-16
Abstract
Abstract Cellulose is bleached with reduced use of chlorine at atmospheric pressure in a plural step process using as the only bleaching agents chlorine dioxide and a per compound, which process begins and ends with per compound steps and has alternating per compound and chlorine dioxide steps.
Inventors
- 👤 Gerhard Hebbel
- 👤 Horst Kruger
- 👤 Werner Traser
- 👤 Herbert Pfand
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; D21C9/1057
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
133 words
A PLURAL STEP PROCESS IN THE ABSENCE OF SUPERATMOSPHERIC PRESSURE OF A CHLORINE-POOR COMPLETE BLEACHING OF CELLULOSE IN AN AQUEOUS MEDIUM WHEREIN THE MAIN BLEACHING AGENT IS A PER COMPOUND AND USING AS THE ONLY BLEACHING AGENTS CHLORINE DIOXIDE AND A PER COMPOUND WHEREIN THE BLEACHING OF THE CELLULOSE CONSISTS OF BLEACHING IN A FIRST BLEACHING STEP IN WATE R WITH A PER COMPOUND, THEN IN A SECOND BLEACHING STEP IN WATER WITH CHLORINE DIOXIDE, AND THEN IN A THIRD BLEACHING STEP AGAIN IN WATER WITH A PER COMPOUND, SAID PROCESS HAVING ALTERNATING PER COMPOUND AND CHLORINE DIOXIDE STEPS, BEGINNING AND FINISHING WITH PER COMPOUND STEPS, THE CHLORINE DIOXIDE BEING EMPLOYED IN AN AMOUNT TO PROVIDE NOT OVER 1 WEIGHT PERCENT OF CHLORINE BASED ON THE OVEN DRIED WEIGHT OF THE CELLULOSE EMPLOYED.
Claim 2
Dependent Claim
133 words
A PLURAL STEP PROCESS IN THE ABSENCE OF SUPERATMOSPHERIC PRESSURE OF A CHLORINE-POOR COMPLETE BLEACHING OF CELLULOSE IN AN AQUEOUS MEDIUM WHEREIN THE MAIN BLEACHING AGENT IS A PER COMPOUND AND USING AS THE ONLY BLEACHING AGENTS CHLORINE DIOXIDE AND A PER COMPOUND WHEREIN THE BLEACHING OF THE CELLULOSE CONSISTS OF BLEACHING IN A FIRST BLEACHING STEP IN WATE R WITH A PER COMPOUND, THEN IN A SECOND BLEACHING STEP IN WATER WITH CHLORINE DIOXIDE, AND THEN IN A THIRD BLEACHING STEP AGAIN IN WATER WITH A PER COMPOUND, SAID PROCESS HAVING ALTERNATING PER COMPOUND AND CHLORINE DIOXIDE STEPS, BEGINNING AND FINISHING WITH PER COMPOUND STEPS, THE CHLORINE DIOXIDE BEING EMPLOYED IN AN AMOUNT TO PROVIDE NOT OVER 1 WEIGHT PERCENT OF CHLORINE BASED ON THE OVEN DRIED WEIGHT OF THE CELLULOSE EMPLOYED.
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
35 words
A process according to claim 1 wherein the per compound is used in an amount of 0.5 to 10% calculated as 100% hydrogen peroxide and based on the oven dried weight of the cellulose employed.
Claim 5
Dependent Claim
27 words
A process according to claim 1 wherein there is included at least one additional chlorine dioxide or per compound step in water subsequent to said third step.
Claim 6
Dependent Claim
30 words
A process according to claim 4 wherein there is employed chlorine dioxide in a fourth bleaching step in water and a per compound in a fifth bleaching step in water.
Claim 7
Dependent Claim
18 words
A process according to claim 1 wherein the per compound is hydrogen peroxide, sodium peroxide or t-butyl hydroperoxide.
Claim 8
Dependent Claim
69 words
A process according to claim 5 wherein the amount of per compound is 0.5 - 6% by weight calculated as 100% hydrogen peroxide and based on the oven dried weight of the cellulose employed. 8. A process according to claim 1 wherein the bleaching is carried out in all of the steps at a temperature between 20* C. and the boiling temperature of the bleach liquor at atmospheric pressure.
Claim 9
Dependent Claim
25 words
A process according to claim 8 wherein the water employed in the process is 10 to 40 times the weight of cellulose to be bleached.
Claim 10
Dependent Claim
21 words
A process according to claim 9 wherein the water from the third bleaching step is returned to the first bleaching step.
Claim 11
Dependent Claim
33 words
A process according to claim 10 wherein chlorine dioxide is employed in a fourth bleaching step in water and the water from the fourth bleaching step is recycled to the second bleaching step.
Claim 12
Dependent Claim
16 words
A process according to claim 1 wherein the per compound is hydrogen peroxide or sodium peroxide.
Claim 13
Dependent Claim
13 words
A process according to claim 12 wherein the per compound is hydrogen peroxide.
Claim 14
Dependent Claim
12 words
a process according to claim 4 wherein the cellulose is sulfate cellulose.
References Cited (Backward Citations)
US2492047A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-02-10 | 1978-08-12 | 1979-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-10 | 1982-08-12 | 1983-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-10 | 1986-08-12 | 1987-02-11 | $7700.00 | Window Closed / Lapsed |