Two stage process for sulfonating mechanical pulp fibers
US4708771A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 31, 1984 |
| Grant date | Nov 24, 1987 |
| Priority date | — |
| Expiry date | Dec 31, 2004 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C3/266
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
A two stage sulfonation system includes a mixing tank, a retention tank, a thickening press, a pressurized vessel, and a liquor recovery press in series relation. The system is designed to receive mechanical pulp, in a slurry form, first introduced into the mixing tank simultaneously with a metered charge of sodium sulfite solution from the holding tank, the sodium sulfite content of which is at a level from about 40 to about 200 g/l. The solution is mixed into the slurry to provide a relatively uniform and intimate contact thereof with its fiber content. This slurry is transferred to the retention tank and there held subject to a sub-boiling temperature between 140 to 210 degrees F., producing a first stage sulfonation of the fiber content. The slurry is then passed to the pressurized vessel, in the course of which it is subjected to a pressing action, extracting liquor which inherently contains a majority of the original sodium sulfite charge directed to the mixing tank. A second stage sulfonation occurs in the pressurized vessel, producing a fiber which after refining is suited for use as reinforcing pulp in newsprint or specialty grade paper, without need for addition of conven…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.