Greaseproof paper has a dense structure and therefore provides a natural barrier against materials like fat and oils. The barrier is obtained by extensive refining of the pulp. This refining is however a costly operation, not only in terms of direct costs for the refining but also in terms of indirect costs because the energy consumption for the drying of the paper is affected by the refining. A full-scale trial was performed to investigate the role of the pulp with respect to the energy demand and the barrier properties of the final papers. Paper made of 100% sulphite pulp with a low degree of refining exhibited the lowest energy consumption at a given level of air permeance. In addition, the effect of refining on the air permeance was compared with that of calendering. The calendering affected the air permeance less than the refining. The papers produced in the full-scale trial were later used as substrates for coatings and for detailed studies of the paper structure. Coating with chitosan was examined on a bench-scale and on a pilot scale. The studies showed that greaseproof paper can be upgraded with an oxygen barrier, but also that suitable coating techniques are lacking for the application of the coating in a sufficient amount. The influence of the base paper on the barrier properties of chitosan-coated paper was investigated in another study, in which it was found that greaseproof paper possesses a unique coating hold-out which cannot be met by other types of paper with a more open structure. It was also found that the coated paper had a lower oxygen permeability than the chitosan coating itself, and this indicates that the dense surface layer of greaseproof paper contributed to the oxygen permeability of the coated paper. The pore volume fraction of the greaseproof paper was found to be approximately 40% and it is therefore surprising that its air permeance is so low. To bring understanding to this question, the structure of greaseproof paper was studied using several methods. It was found that the structure was dominated by very small pores with a median diameter of <0.3 µm. The fraction of closed pores was also substantial. A porosity gradient was also found, indicating that the papers used in the study had a closed surface. The hypothesis that the surface layer of the paper contributed to the oxygen barrier was tested in an experiment in which greaseproof paper was extrusion-coated with polyethylene. The oxygen permeability was measured at 0%, 50% and 90% relative humidity, and the permeability was found to increase with increasing moisture content. Because only the cellulose layer in the paper and not the polyethylene layer in the coating is affected by moisture, this result supports the hypothesis that the surface layer of the paper contributed to the oxygen barrier properties of the coated paper.

We are provided countless products from the forest industry and has been through many years. Paper, paper board, packaging materials and furniture to mention a few. A special type of paper used in food packaging for example, is greaseproof paper. Many producers of greaseproof papers use the toxic and harmful group of chemicals called per- and polyfluorinated alkyl substances (PFAS) in coating since they possess grease resistance. Nordic Paper is a manufacturer of iamKraft® kraft paper and greaseproof paper with over a hundred years of experience without the use of PFAS. Without PFAS, they instead rely on excess refining to form a very dense paper. Nordic Paper has decided to introduce the addition of eucalyptus fibers to the softwood sulfate pulp to enhance the formation of the paper. This study aims to investigate the effects of ~20% addition of eucalyptus fibers to softwood sulfate pulp in regard to refiner energy expended, air permeance (as a measure of grease resistance) and formation. Laboratory work has been done on hand made sheets with a vacuum suction box in laboratory scale. Eight different pulps (four with addition of eucalyptus), provided from Nordic Paper Seffle AB, Säffle, with different refining degree was used in this study. The vacuum pressure used was 20 kPa through all tests, with dwell times 0, 1, 2.5, 5, 10, and 20 ms on sheets with a grammage of 50 g/m2. The study has shown that the pulp with ~20% addition of eucalyptus achieved 86°SR with only 82% expended energy relative to the softwood pulp, which had a refining degree of 87°SR. This small difference in refining degree led to a similar development in dewatering after 20 ms dwell time and 20 kPa, where the softwood pulp achieved a dryness of 9.2% and the pulp with addition of eucalyptus achieved 9.0% dryness. The formation of the softwood pulp was worse, which was the reason for the implementation of addition of eucalyptus. The air permeance on the other hand was not improved by the eucalyptus, but more data is needed to confirm since it is based on only one occasion. So, if the air permeance (grease resistance) allows, Nordic Paper Seffle AB may be able to save 20% in expended energy for refining of softwood sulfate pulp with addition of eucalyptus. / Vi tillhandahåller otaliga produkter från skogsindustrin och har gjort i många år. Papper, kartong, förpackningsmaterial och möbler för att nämna några. En speciell typ av papper som används i till exempel livsmedelsförpackningar är fettresistent papper. Många tillverkare av dessa papper använder den giftiga och skadliga gruppen av kemikalier som kallas per- och polyfluorerade alkylämnen (PFAS) i beläggning eftersom de har fettbeständiga egenskaper. Nordic Paper är en tillverkare av iamKraft® kraftpapper och ”greaseproofpapper” med över hundra års erfarenhet utan användning av PFAS. Utan PFAS förlitar de sig istället på extra malning av fibrer för att bilda ett mycket tätt papper. Nordic Paper har beslutat att införa tillsats av eukalyptusfibrer till sulfatmassa av barrved för att förbättra formationen på papperet. Denna studie syftar till att undersöka effekterna av ~20 % tillsats av eukalyptusfibrer till barrsvedssulfatmassan med avseende på förbrukad malningsenergi, luftpermeans (som ett mått på fettbeständighet) och formation. Laborationer har utförts på handgjorda ark med vakuumsuglåda i laboratorieskala. Åtta olika massor (fyra med tillsats av eukalyptus), tillhandahållna från Nordic Paper Seffle AB, Säffle, med olika malningsgrad användes i denna studie. Vakuumtrycket som användes var 20 kPa genom alla tester, med uppehållstider 0, 1, 2.5, 5, 10 och 20 ms på ark med en ytvikt på 50 g/m2. Studien har visat att massan med ~20% tillsats av eukalyptus uppnådde 86°SR med endast 82% förbrukad energi i förhållande till sulfatmassan, som hade en malningsgrad på 87°SR. Denna lilla skillnad i malningsgrad ledde till en liknande utveckling i avvattning efter 20 ms uppehållstid och 20 kPa, där sulfatmassan uppnådde en torrhalt på 9.2% och massan med tillsats av eukalyptus uppnådde 9.0% torrhalt. Formationen på sulfatmassan var sämre, vilket var anledningen till genomförandet av tillsats av eukalyptus. Luftpermeansen å andra sidan förbättrades inte av eukalyptusen, men mer data behövs för att bekräfta detta eftersom den enbart är baserad på ett enda tillfälle. Så om luftpermeansen (fettbeständigheten) tillåter kan Nordic Paper Seffle AB spara 20% i förbrukad energi för malning av barrvedssulfatmassa med tillsats av eukalyptus.

Vacuum dewatering of paper is a heavily energy expensive process, even more so for greaseproof paper, which is one of the main products at Nordic Paper Seffle AB. Due to this being such an energy demanding process, improvements in the vacuum dewatering could save massive amounts of energy. The focus of this thesis is to investigate the effect of a triple vacuum suction box on the dewatering rate of greaseproof paper, using a tried and tested method of simulative triple vacuum suction box at a laboratory scale, with the difference of simulating a quadruple vacuum suction box, and how the grammage of the paper sheet affected this, using unbleached sulphate pulp consisting of soft wood with an addition of 20 % eucalyptus fibers. The results were as expected, showing the expected dryness curve behavior of diminishing returns of the dryness to dwell time ratio, and the method showed valid for improving the energy efficiency compared to a single vacuum suction box, in terms of both expended energy, and yielded dryness. The grammage had a significant effect on the dewatering, with the heavier paper at 100 gsm showing the need of higher dwell times and increased levels of vacuum pressure than the lighter paper at 50 gsm. An addition of a triple vacuum suction box could possibly replace multiple high vacuum suction boxes, leading to even greater savings. Further testing would be required for optimization of the vacuum levels and dwell times for the 100 gsm paper sheet, in order to reach the same dryness as the 50 gsm paper sheet. / Vakuumavvattning av papper är en mycket energikrävande process, ännu mer för greaseproofpapper, som är en av huvudprodukterna hos Nordic Paper Seffle AB. Eftersom detta är en så energikrävande process kan förbättringar av vakuumavvattningen spara enorma mängder energi. Fokus för denna avhandling är att undersöka effekten av en trippelvakuumsuglåda på avvattningseffektiviteten av greaseproofpapper, med hjälp av en beprövad metod för simulativ trippelvakuumsuglåda i laboratorieskala, med skillnaden att simulera en fyrdubbelvakuumsuglåda, och hur ytvikten på pappersarket påverkar detta; med oblekt sulfatmassa bestående av långfiber med tillsats av 20 % eukalyptusfibrer. Resultaten var som förväntat och visade den förväntade torrhaltskurvans beteende av avtagande förbättring av torrhalten, och metoden visade sig vara giltig för att förbättra energieffektiviteten jämfört med en enda vakuumsuglåda, både vad gäller förbrukad energi och torrhalt. Ytvikten hade en stor effekt på avvattningen, där det tyngre papperet på 100 gsm visade behov av längre uppehållstider och ökade nivåer av vakuumtryck än det lättare papperet vid 50 gsm. Ett tillägg av en trippelvakuumsuglåda kan troligen ersätta flera högvakuumsugslådor, vilket leder till ännu större besparingar. Ytterligare tester skulle krävas för optimering av vakuumnivåerna och uppehållstiderna för 100 gsm pappersarket, för att nå samma torrhet som 50 gsm pappersarket.