Stock dyeing, or internal dyeing in packaging grades is one of the biggest challenges that face papermakers today. Paper machines differ in the chemistry of the wet end. There are no two paper machines with identical chemistry. Because of that, the use of chemicals must be optimized individually for each paper machine. This is also true in conjunction with the application of dyes.

In order to get a uniform shade from reel to reel there are many factors that need to be taken into consideration, namely:

Paper machine furnish

(waste quality and variations)

• Dyeing conditions
• Correct choice of dyestuffs and Technology

partner

 ROBAMA – ACAT Technology partner, dyestuffs

ROBAMA is a European manufacturer of dyes, optical brighteners and auxiliaries, mainly for paper, textile and leather industries with a range of over 150 brown liquid dyes (direct and basic) which covers the most demands of the market.

Although ROBAMA has a wide extended range of over 150 brown liquid dyes (direct and basic) which covers the most demands of the market, their technical department developed new colors to meet with our customers specific requirements.

Correct selection of dyestuffs for successful trials is critical and particularly complicated.

Trial results:

The three coordinates of CIELAB represents the lightness of the color (L*= 0 yields black and L* =100 indicates diffuse white; specular white may be higher), its position between red/magenta and green (a*, negative values indicate green while positive values indicate magenta) and its position between yellow and blue (b*, negative values indicate blue and positive values indicate yellow.) Robama were able to blend a brown dye to achieve the L*, a* and b* values to meet our specific customer’s requirements.

MPACT paper mill – Industrial trial

MPact Paper Mills manufacture recycled based

Packaging and industrial paper grades.

Fibre used in this process is a combination of recycled industrial waste and sugarcane bagasse. One of the biggest costs of producing quality packaging grades at any waste based operation is the shading requirements of their customers. This particular machine is a single ply fourdrinnier without a size press, hence internal dyeing of the sheet requires the addition of large amounts of brown and black dye.

Mpact management awarded ACAT a 7-day on-machine trial based on color matching and onsite laboratory analysis done using Robama Trupocor brown and black dye specifically blended to mill specification.

Summary:

 A significant overall reduction in brown dye

consumption

• Very stable L* and a* values despite challeng-

ing changing conditions during the trial.

• Guaranteed future business and a first for

supply of dyestuff into the paper industry.

It is well known that a high linting and dusting tendency of newsprint will almost certainly cause a higher frequency of production stops in offset printing.

Such stops are connected with production losses and high costs for blanket cleaning. Linting and dusting are terms used to define the tendency of a paper surface to shed loose and weakly bonded particles and accumulate these on the blanket during offset printing.

Dust is filler or other fines materials, which are not firmly attached to the paper surface. Such materials are easily removed from the paper surface during prining and accumulate on the printing blanket especially in the first first printing unit. The result is a deterioration of the print quality to the point where the press must be stopped and cleaned.

Fibers are removed from the surface of the paper when the external forces exceed the forces holding the fibers together. This programme deals with the area of internal treatments of thermomechanical pulp (TMP) and recycled fiber containing paper grades such as newsprint. The objective of such treatments was to reinforce the surface strength of the paper in order to decrease the linting and dusting of the paper during printing.

SizeStarR 300 L

SizeStar® 300 L is a semisynthetic polymeric sizing agent, which improves internal sizing and deceases dusting. It gives good control of sheet hydrophobicity and subsequent improvement in heat set offset printing performance.

SizeStar® 300 L is applied as an internal sizing agent in newsprint to impart resistance to the penetration of water and fatty liquids in the substrate. SizeStar® 300 L is added to thickstock at a point of high shear for optimum distribution in the stock. Recommended dilution before dosage is 1:10.

The objective was to determine the overall positive impact on linting on Newsprint with the use of SizeStar® 300 L. SizeStar® 300 L was added to the suction of the machine chest.

SUMMARY:

• An overall reduction in lint chemical was achieved
• A significant overall reduction in starch and polymer was achieved.
• A reduction in the lint view numbers was achieved
• An improvement in sheet properties in terms of Tear and Tensile were observed even with an increase in sheet ash of 0,5% during the trial period.