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Chemical and Morphological Analyses of the Tissue Yankee Coating
Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
Hollmark Imptec AB.
Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
2009 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 24, no 1, 52-59 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2009. Vol. 24, no 1, 52-59 p.
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
URN: urn:nbn:se:kau:diva-3813DOI: 10.3183/NPPRJ-2009-24-01-p052-059OAI: oai:DiVA.org:kau-3813DiVA: diva2:208682
Available from: 2009-03-19 Created: 2009-03-19 Last updated: 2013-11-22Bibliographically approved
In thesis
1. Improvement of the tissue manufacturing process
Open this publication in new window or tab >>Improvement of the tissue manufacturing process
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The creping process and the conditions on the Yankee cylinder are the key factors in the production process. They need to be kept under good control in order to maintain a high and uniform quality. A natural coating always develops on the surface of the Yankee cylinder due to evaporation from dissolved and dispersed substances and to fiber fragments that remain on the surface after creping. Nevertheless, coating chemicals are sprayed onto the Yankee surface in order to modify the adhesion between the paper and the dryer cylinder. To be able to control the process, on-line measurements of coating thickness as well as of the crepe structure of the tissue paper produced would be very valuable. In the work described in this thesis, the coating layer was analyzed chemically and morphologically to provide information about the coating layer before starting any on-line measurements. The chemicals added and the constituents of the pulps are known to the paper producers, but what is left on the cylinder and whether there are different layers of coating still remain to be investigated. The chemical analysis indicated that the adhesive content was higher in an inner layer of the coating than in the outer layer. The relative amount of polyamide-amine resin calculated on the basis of the nominal nitrogen content in the resin was low indicating that the coating consisted of a significant amount of carbohydrates or other substances. The coating layer could not be considered transparent. It was observed that the coating was thick and appeared patch-wise and that it contained fiber fragments. Measurements on a laboratory scale, to further be applied on-line on the tissue machine, have been investigated and evaluated in this study. The thickness of the coating layer on a laboratory dryer has been measured. The method was based on fluorescence with an optical brightener added to the coating chemicals sprayed on the Yankee dryer. With a UV-LED (Ultra Violet - Light Emitting Diode) the coating layer was exposed to UV-light and the intensity of the light emitted by the optical brightener in the layer was measured. The intensity in the trials with different thickness of the coating and no coating was scattered and no trend could be seen between the different trial points. Attempts were made to measure the wavelength of the tissue paper produced with an optical fiber perpendicular to and at an angle to the paper surface. The paper was travelling in a slow speed while the measurements were made. The collected signal to noise ratio was low and it was not possible to detect any representative characteristic wavelength of the tissue.

Place, publisher, year, edition, pages
Karlstad: Karlstad University, 2009. 35 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2009:13
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-3646 (URN)978-91-7063-236-5 (ISBN)
Presentation
2009-03-27, Ericssonsalen 9C 204, Karlstad universitet, Karlstad, 10:00 (Swedish)
Opponent
Available from: 2009-03-19 Created: 2009-02-19 Last updated: 2011-10-18Bibliographically approved
2. New methods for evaluation of tissue creping and the importance of coating, paper and adhesion
Open this publication in new window or tab >>New methods for evaluation of tissue creping and the importance of coating, paper and adhesion
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The creping process and the conditions on the Yankee cylinder dryer are key factors in a tissue paper mill, and they therefore need to be kept under good control in order to maintain a high and uniform quality. To this end it would be valuable to be able to make on-line measurements of Yankee coating thickness as well as the crepe structure of the tissue paper. The adhesion of paper to the cylinder affects the creping process and more information about the parameters that affect the adhesion is therefore of interest. To perform trials on a full scale or in a pilot plant is very costly and laboratory creping equipment is therefore sought after in order to be able to measure the adhesion force.

The coating layer for use on the cylinder was analysed. It contained a large amount of carbohydrates and could not be considered transparent. The thickness of the coating layer was measured on a laboratory cylinder with a method based on fluorescence. An optical brightener was added to the coating chemicals and the coating layer was subjected to UV-radiation. The intensity of the light emitted by the optical brightener was measured and gave an indication of the thickness of the coating layer. The equipment has to be further investigated before it is possible to implement the new sensor on-line.

New creping equipment and an adhesion method were developed for use on a laboratory scale. The equipment can operate with different creping angles and the force needed to crepe the paper can be measured. The highest creping force was obtained for papers of high grammage, low dryness at adhesion, high drainability, high fines content and high hemicellulose content.

A more direct method is to analyse the structure of the produced paper. Measurements were made on a tissue paper with an optical fibre sensor while the paper was travelling at low speed. The collected signal was mathematically analysed and the characteristic wavelength was calculated for different paper samples. These values were close to the wavelengths measured with an off line method by a commercial crepe analyser.

Abstract [en]

Baksidestext

The creping process is the heart of tissue paper manufacture. To control the process better, on-line measurements of paper structure and coating thickness are sought after. The creping is highly dependent on the adhesion of the paper to the Yankee dryer. To be able to measure the adhesion, laboratory creping equipment was also required. Different pulp parameters affect the adhesion and some of them have been investigated in this work.

The coating on the Yankee cylinder consisted mainly of fiber fragments and could not be considered as transparent, which had to be considered when choosing a method to measure coating thickness. A method based on the light emitted from an optical brightener in the coating when subjected to UV-irradiation was used, but has to be further improved before it can be used on-line.

A new laboratory creping method was developed to determine the adhesion between paper and metal, and the force needed to scrape off the paper with a doctor blade was measured. The highest creping force was obtained for papers made of pulp with a high drainability, high fines content and high hemicellulose content.

An optical method using reflected light to measure crepe wavelength on-line was developed. The paper travelled under a sensor and the light collected was mathematically analyzed to determine the most common wavelength.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2013. 60 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2013:47Karlstad University Studies, ISSN 1403-8099
Keyword
tissue, creping, paper adhesion, Tissue paper, creping, paper adhesion, coating layer, adhesives, Yankee cylinder, crepe structure, wavelength measurements
National Category
Engineering and Technology
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-29317 (URN)978-91-7063-525-0 (ISBN)
Public defence
2013-12-13, Nyqvistsalen, Karlstads universitet, Karlstad, 10:15 (English)
Opponent
Supervisors
Available from: 2013-11-22 Created: 2013-10-07 Last updated: 2015-11-26Bibliographically approved

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Boudreau, JonnaBeghello, Luciano

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