Our FAQ
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Is Test liner only produced by brown dyes?
No the only True Brown Dyes are Basic Dyes and have poor fastness. The ADD's Browns are all mixtures of Yellow, Orange, Red Blue and Black liquids. Using the Single dyes say Yellow, Orange and Blue enables excellent shade control and very quick color change grades.
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Do dyes effect the paper making process?
No, dyes have no effect on the paper making process, BUT the paper making process can effect the dyes and color. Temperature, Anionic and or Cationic additives, Alum etc.
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Basic principles of the dyes addition.
Most modern machines use metered liquid dyes. These dyes are added Late in the system separated from other chemical adds. The best addition point is after the Level Box or before silo and fan pump. In very Dark shades 2/3rds of the dye can be added at the Pulper and the balance color controlled at normal addition point.
If a combination of ADD and CDD is used then they must be separated by at least 2 meters at the addition points.
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How to determine the Bulk dyeing formulation from Lab?
The actual dosage of dyes in production line is generally 60- 80% of the laboratory amount. This is because of on machine circulation of backwater and very hard water. Where multiple dyes are used to obtain shade best to reduce all of them by 50% as the individual dyes have different substantivity and can greatly alter final shade.
Only on machine can final dye formulation be achieved. However using Closed Loop Color Control, the shade can easily be achieved if start at 50% of Lab formulation and let the control achieve the final shade.
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Factors which can affect the dyeing result.
1) Stock quality & concentration.
2) Addition point and addtion sequence of dyes.
3) Temperature.
4) Filler and pH value.
5) White water recycling.
6) Process auxiliaries.
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The function of Aluminum Sulfate.
Alum is used as a fixative for sizing where Rosin is used. It also is used to flocculate Anionic Trash. However, it should never be used for pH control as will contribute to very high conductivity. It is very beneficial for ADD dyes in that it promotes fixation of them to pulp fibers.
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Why can't Dye affinity reach 100%?
As the dyes not only dye the pulp fibers they also dye Anionic trash and fillers. The first pass retention on paper machines is never 100% and in some cases Filler retention can be as low as 50% so this colored mater stays in the backwater. When dyeing it is important to Close the system as much as possible to ensure little or no colored water is discharged into the environment.
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How to improve the two-sidedness of paper?
Two-sidedness of colored paper sheet is where one side of paper sheet is darker while it is lighter on the other side. This normally occurs where fillers in sheet are used and the dyed filler accumulates on the vacuum side of the sheet resulting in darker color.
To reduce the two-sidedness of paper, the following points need to be done:
Correct selection of dyes and pigments; Check amount of filler; The foils and vacuum system should be adjusted to improve wet line;
Check addition point and sequence, the use of fixing agent, color fixing agent or other dyeing auxiliaries, and the surface dyeing together.