|
|
Bleaching
Whiteness, as a comparison to a standard, is measured in a 100 pt range.
Bleached, sulfite pulp can achieve a value of 94% ISO when tested on a Zeiss reflectance meter, and unbleached alkaline stock may be 15% ISO as a comparison. This is the characteristic brown, corrugated paper found in bags and cartons. So-called chromophoric group on the lignin are responsible for color. The fibers themselves, the cellulose and hemi-cellulose are inherently white and do not contribute to the color. Hence, the strategy of bleaching is to destroy these chromophoric groups. There are two principal methods in bleaching. One is to selectively destroy the chromophoric groups on the lignin while leaving the lignin itself intact. This is generally referred to as ‘brightening’ and is more common on mechanical pulps that have high lignin content. Brightening however does not have a permanent effect; exposure to light causes lignin to dicolor as can be observed with old newspapers. True bleaching removes all residual lignin and allows stable white pulps to be produced.
|
|
|
|
|
Locate a dist
|
Tech support / Request Price
|
Process Related Products
|
Process Related Product Case Histories
Case History Report:
CHS20040925-0025
|
Equipment: Suction fan
|
|
Problem: Exposure:
PH 4.5. Temp. 50°C - 60°C
Chlorides and high humidity
Problem:
The production was changed. This resulted in the fluid having a lower pH and a higher temperature. Due to these environmental changes, heavy corrosion has occurred on the suction fans. Some of these fans are 15 years old. A new acid-proof fan will cost $20,000 (USD).
|
|
|
Hide Left Menu
Packing wizard