US3830689A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Separate impregnation and common digestion of different wooden raw materials
Assignee: Metsaluton Selluloosa Oy
•
Filing: 1971-09-27
•
Granted: 1974-08-20
•
Expires: 1991-09-27
Abstract
Abstract Each of at least two different wooden raw material portions are separately impregnated with separate wood cooking solutions differing in strength and pH after which excess cooking solution is withdrawn from each raw material portion and the separately impregnated raw material portions are cooked together in a single steam phase cooking step.
Inventors
- 👤 P Rautalahti
- 👤 J Kettunen
- 👤 O Sonni
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 13:37
CPC Classifications
D; D21; D21C; D21C1/00; D21C3/00; D21C3/04; D21C3/06
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
42 words
The method of claim 1, wherein the raw materials are about 80 percent pine and about 20 percent birch and said pine is impregnated with a solution of sodium bisulphite and said birch is impregnated with a solution of carbonate-buffered sodium sulphite.
Claim 2
Dependent Claim
28 words
The method of claim 2, wherein said sodium bisulphite solution has a pH of about 4.5 and said carbonate-buffered sodium sulphite solution has a pH of about 8.5.
Claim 3
Dependent Claim
33 words
The method of claim 1, wherein said cooking is at a temperature of from about 160* C to about 165* C for a period of from about 20 minutes to about 60 minutes.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-08-19 | 1978-02-18 | 1978-08-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-19 | 1982-02-18 | 1982-08-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-19 | 1986-02-18 | 1986-08-20 | $7700.00 | Window Closed / Lapsed |