Two-stage chemical treatment of mechanical wood pulp with sodium sulfite
US4502918A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 4, 1982 |
| Grant date | Mar 5, 1985 |
| Priority date | — |
| Expiry date | Jun 4, 2002 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C3/266
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
A two-stage chemical treatment process is disclosed for increasing the density, strength and brightness properties of mechanical wood pulp. The method comprises the steps of: applying an aqueous solution of sodium sulfite in the range of about 1%-10% sodium sulfite based on bone dry weight of wood to wood particles, the solution having a pH in the range of about 4.5-11; heating the sodium sulfite treated wood particles to a temperature in the range of about 100.degree.-160.degree. C. and maintaining the particles in the temperature range for a period of time in the range of about 20 seconds to 10 minutes; refining the heated sodium sulfite treated wood particles into mechanical wood pulp; separating the pulp into a reject fraction and an accept fraction, the reject fraction containing a higher proportion of shives and long fiber material; applying an aqueous solution of sodium sulfite, in the range of about 4%-50% sodium sulfite based on bone dry weight of wood, to the reject fraction, the solution having a pH in the range of about 4.5-11; cooking the sodium sulfite treated reject fraction at a temperature in the range of about 100.degree.-160.degree. C. for a period of time in the…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.