Mare Dynamics

Mare: some recent developments in the field of yankee coating

The conditioning of the yankee cylinder surface plays a dramatic role in the performance of the tissue machine.

Author: Mare SpA

The setup of the coating “layer” is so important that it can make the difference between producing high quality, properly creped tissue in case of a good set up and jeopardizing production or, even, stop the machine to prevent severe damages on the yankee in case of a bad arrangement. What is also well known is that the yankee coating can be influenced both directly, through the nature and dosage of yankee coating chemicals, and indirectly through chemicals added to the process.
Creping efficiency and caliper development are among the most important key process indicators of the tissue creping process. They are both linked to process performance and machine productivity, as tissue makers know very well. We have recently made some valuable experiences under this regard, that we would like to submit to you as case histories.

In this article we want to introduce you to our novel chemicals MARESOFT S 850 and MARERELEASE R 300. The first chemical is used to integrate the yankee coating recipe used on the tissue machine, while the second can be used both to integrate the recipe or to substitute the incumbent release agent. Either way, the chemicals allow the formation of a more uniform, thicker and plastic coating layer, characterized by a lower friction level (Cover picture).
Some case histories follow.

Mare has the capabilities and experience to meet your chemical needs with both functional and process chemistries

Table 1: It is clearly visible the reduction of roll length required to reach for the same roll diameter with a growing dosage of MARESOFT S 850

 

Case history 1

One of our customers aimed at increasing the caliper of tissue paper so to decrease the crepe ratio on the machine and increase production rate of double width, high speed machine. For this reason, MARESOFT S 850 was fed to the yankee spray bar while no other process parameters neither the dosage of the existing yankee coating chemicals.

The increase of caliper was revealed instantly by a reduction of the length of tissue, wrapped in the roll in production, needed to reach for the same roll diameter (Image 1, Image 2).

As it can be seen in Table 1, the reduction of length can be estimated in minimum 6%. This can be translated as (a) a corresponding reduction of bulk density of the tissue sheet or (b) as reduction of the time to reach for the same diameter in the roll or (c) as an increase in the number of rolls produced at the end of the day with the same amount of fiber. The gain in caliper measured in the mill’s lab was about 9% with the consequent possibility (d) to decrease the crepe ratio increasing production having caliper in spec.

Image 1: This picture represents the impact on roll diameter at different roll length while MARESOFT was dosed. It is clear how shorter roll lengths were needed to get to the same diameter
Image 2:
Length required by a tissue roll to reach for a 190 cm diameter vs dosage of MARESOFT S 850

Case history 2

A tissue mill experienced a severe loss of caliper at every ceramic blade change on one of its high softness premium tissue grades. The only way to recover quickly the caliper was to reduce by 4% the pope reel speed and the corresponding production rate until the blade bevel was worn enough to recover thickness. In order to help with this issue, MARESOFT S 850 was fed to the spray bar of a double width, high speed tissue machine, keeping constant all the other process parameters and chemical dosages. The mill observed that MARESOFT S 850 helped them to keep the caliper up and to avoid the usual reduction for pope reel speed.

The paper and board manufacturing industry runs through the core of Mare

Case history 3

In one additional case history, MARERELEASE R 300, a novel release aid with was applied as an additional component of the coating package in place of the standard release. The advantage of caliper growth was once again used to increase machine productivity. The caliper measured on the tissue rolls increased enough to allow a reduction of the crepe ratio from 17,6% to 16,0% and an increase in yankee speed of 3%, preserving the specs of the paper. The corresponding combined increase in daily production was assessed in +6%.

We hope that these few lines once again will demonstrate the proactivity and creativity of MARE in delivering new solutions on the tissue market, with the goal to contribute to the performance of the operations of our customers. Contact your local MARE sales representative for more information.

 

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