The packaging and board sector a highly specialized
section of the paper industry has a great demand for the dyestuffs. This
increasing demand is backed by the replacement of traditional basic
dyestuffs with highly advanced and modified basic and direct dyes.
Traditional Basic dyes enjoyed an unrivalled position for a considerable
number of years due to a lot of factors, important among them are high
colour strength, acceptable properties and a more or less modest
pricing. But over the years, other dye types, that includes the Direct
dyes have tilted the scale of economy in its favour as the perfect
choice in the packaging sector.
When it comes to packaging grades the choice of dyes
narrows down to three broad categories namely
Basic dyes,
Modified
Basic dyes and
Anionic direct dyes. However, a very vital
point to note here is that the selection of the dye types cannot be done
in isolation only. Other points like if the end product is to be added
to a size-press or in the wet-end (stock addition) must be thoroughly
considered. Given here are few of the criterias that are applied while
considering the type of dye to be used.
- Hue and depth of target shade
- Necessary technical properties like lightfastness
- Base colours and types of the furnish
- Laws governing environment
- Cost factors
The following table highlights the comparative
advantages, disadvantages of the three types of dyes used in the
packaging sector namely Basic dyes, Modified Basic dyes and Aninic
Direct Dyes.
Dye |
Advantage |
Limitation |
Basic dye |
Substantively is moderate |
Poor lightfastness |
|
Above par tinctorial strength |
Not so good shade stabilty |
|
Is economical |
Acid content is high |
|
Diverse shade range |
Backwaters coloured |
|
|
Preferential Dyeing |
Modified Basic dye |
Very good Substantivity |
Shade range is somewhat limited |
|
Backwaters are cleared |
Lighfastness through better than basic dyes, but still not up
to the mark |
|
Coverage of all the fibers |
|
|
Light fastness is better than basic dyes |
|
Anionic Direct Dyes |
Good substantivity |
Somehow limited build-up on some furnishes |
|
Llightfastness is moderate to good |
|
|
Not expensive |
|
|
Broad shade |
|
The dyes find application in the following popular
packaging sector:
- Newsprints
- Sacks
- Egg boxes
- Carton board
- fiber board
- Kraftliner
- Cationic size press formulations
- Anionic size press formulations