The objective of this work was to study the addition of fluorescent whitening agents (FWAs) for efficient use on pigment coating of paper substrates with low grammage and the goal was to achieve high optical response by using low amount of FWAs. A commercial light-weight coated (LWC) paper grade was provided by Stora Enso Corbehem Mill and isotropic laboratory sheets were produced at Stora Enso Research Centre using PFI sheet former. Optical properties such as brightness, whiteness and L, a* and b* colour space values were evaluated using Minolta spectrophotometer with D65 illuminant for both types of substrate using different types and amounts of FWA while the effect of the addition of dye was evaluated in both isotropic sheets and as well as in the coating. The results showed that brightness and whiteness of double-coated paper increased by increasing the amount of fluorescent whitening agent in the coating layer. Also, higher brightness and whiteness was achieved by introducing a higher amount of fluorescent whitening agent in the top coating rather than in a pre-coating. The addition of a shading colorant in the paper substrate had a positive influence not only on the brightness but also on the whiteness of coated paper. / Syftet med denna studie var att studera tillsatsen av fluorescerande vitmedel (FWA) för att effektivisera användningen i pigmentbestrykning av papper med låg ytvikt. Målet var att nå en hög optisk respons men ändå använda en låg mängd FWA. Ett kommersiellt LWC-papper erhölls från Stora Enso, Corbehems pappersbruk, och isotropa laboratorieark tillverkades med PFI-arkformerare på Stora Enso Research Centre. Optiska egenskaper, såsom ljushet, vithet och färgrymd (L, a* och b* värden), hos samtliga prover med varierande mängd och typ av FWA uppmättes med hjälp av en Minolta spektrofotometer med D65 ljuskälla. Effekten av färgnyanstillsats utvärderades både hos handgjorda ark och hos bestrykningslager. Resultaten visade att både ljushet och vithet hos dubbelbestrukna ark ökade med ökad mängd FWA i bestrykningslagren. Högre ljushet och vithet nåddes också när FWA placerades i toppbestrykningen. Tillsats av nyanseringsfärg i papperssubstratet ökade både ljushet och vithet hos de bestrukna arken.

Orientadores: Carlos Magnus Carlson Filho, Raul Vinhas Ribeiro / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-05T15:44:02Z (GMT). No. of bitstreams: 1 Domingos_AlinePaulino_M.pdf: 2016351 bytes, checksum: 82db83a7778962c2c07b6ea4ac7e6514 (MD5) Previous issue date: 2005 / Resumo: As novas tecnologias de transmissão trazem maior flexibilidade e eficiência à rede de acesso, tornando-a capaz de atender o contínuo crescimento de demanda por serviços de telecomunicações. Uma alternativa de evolução conveniente em muitos casos é o provimento de serviços através de redes wireless fixas. Estas redes, conhecidas genericamente como FWA (Fixed Wireless Access), podem reduzir os investimentos da infra-estrutura de acesso. Neste trabalho apresentamos uma nova abordagem para o planejamento de sistemas FWA utilizando um modelo de programação linear mista baseado na representação em grafos. Devido à alta complexidade associada à resolução de problemas deste tipo através de métodos exatos, propomos um tratamento baseado em algoritmos genéticos (GA). A partir de uma formulação exata, mostramos como especificar os componentes principais de um GA: cromossomo, codificação da solução, avaliação de fitness, estrutura da população e operadores genéticos (processo de cruzamento e mutação). No problema tratado, as variáveis de decisão foram codificadas para um cromossomo especializado e eficiente. Além disto, o problema da infactibilidade de alternativas geradas foi contornado por um método de descarte. Garante-se também para cada alternativa a maximização da demanda atualizada (o que proporciona maior rentabilidade). Uma aplicação do método é relatada / Abstract: New transmission technologies give more flexibility and efficiency to the Access network, which is supposed to deal with the continuous growth of demand for telecommunication services. Operator companies need to innovate their networks in order to provide broadband services. Therefore, the network planning is essential to achieve the best performance under minimum cost. An alternative of evolution that seems to be interesting is the provision of services through fixed wireless networks. These networks, generically known as FWA (Fixed Wireless Access), can reduce the infrastructure access cost. In this paper, we present a new approach to the planning of FWA systems. First, we develop an optimization model with binary decision variables. The mathematical formulation to the model is also stated. Because solving mixed integer problems through exact methods is a complex task, we adopt a strategy based on genetic algorithms (GA). Thus, we show how to specify the main components of a GA: chromosome, solution coding, fitness assessment, population structure, and genetic operators (crossover and mutation process), in order to specialize the technique to the FWA planning problem. Besides, chromosome feasibility is ensured. An application of the proposed method is also reported. / Mestrado / Otimização / Mestre em Engenharia Elétrica

The main purpose of this thesis was to find ways to maintain a low level of light‐induceddiscolouration at an increased addition of mechanical and chemimechanical pulps in coated highqualityfine paper and magazine paper grades. Current technology allows the production of highyieldpulps such as thermomechanical and chemimechanical pulps with properties suitable formanufacturing high‐quality paper or paperboard with a low basis weight. Coating of woodcontainingpaper will probably be necessary for photo‐stability reasons if lignin‐containing pulps areto be used as the main fibre furnish in long‐life and high‐value products.In order to find the most suitable pulp for this purpose, light‐induced discolouration of a variety ofpaper samples from unbleached and bleached softwood and hardwood pulps was studied under bothaccelerated and long‐term ambient light‐induced ageing conditions. Hardwood high‐yield pulps,especially aspen pulps, were proven to be more photo‐stable compared to softwood pulps. Hardwoodpulps should therefore be the first choice for applications where a high permanence is desirable.Evaluating ageing characteristics using the CIELAB colour system showed that accelerated ageingconditions tend to mainly increase the b* value and decrease the L* value (i.e. yellow the pulp),whereas long‐term ambient ageing also increases the a* value, which makes the pulp more reddish.A new method for studying the influence of the UV‐screening properties of coating layers on abase paper was developed, and used to investigate the effect of pigment, pigment size distribution,binder and UV‐absorbing additives. The coat weight and pigment type were found to be the mostimportant factors for reducing the transmittance of UV‐radiation. Coating colours containing kaolinpigments had a lower UV‐transmittance than calcium carbonate pigments. Of the calcium carbonates,precipitated calcium carbonates were better than ground calcium carbonates and the difference wasgreater at higher coat weights. The particle size distribution should preferable be narrow. When thebest pigment (bleached kaolin) and the best binder (styrene butadiene latex) were combined withtitanium dioxide, the UV‐transmittance could be reduced by about 90% at a coat weight of ~10 g/m2.At a coat weight close to 20 g/m2, the transmittance was close to zero. This shows that it is possible tomore or less fully protect a double coated base paper from harmful UV‐radiation, when the coatinglayer has an optimum composition for that purpose. A prerequisite to reach so far is that the coatinglayer has an even coat weight.