Factors influencing MOW deinking : laboratory scale studies

The deinking of MOW is examined at laboratorial scale. The effect of deinking aids, pre-washing and mixing are studied. The operating conditions during pulp treatment affect the pulp and paper properties, interfering with the mechanism of ink removal and modifying the ink particle characteristics. Pre-washing the pulp facilitates the deinking process. Cellulolytic enzymes and deinking chemicals are comparable in terms of ink removal ability.Portucel Vian

Enzymatic versus chemical deinking of non-impact ink printed paper

Enzymatic versus chemical deinking is examined for MOW and photocopy prints. Several enzymatic preparations and two fibre/ink particle separation methods are tested. Deinking was monitored by image analysis and standard pulp and paper characterisation procedures. The effectiveness of the fibre/ink particle separation method depends on the ink particle’s size: for smaller particles a washing step is recommended whereas for larger particles, the use of flotation is necessary. The enzymatic treatment is a competitive alternative for MOW and photocopy paper deinking. However, the process requires the selection of an adequate enzymatic preparation for each paper grade

Refining and enzymatic treatment of secondary fibres for paperboard production : Cyberflex measurements of fibre flexibility

Recycling is generally affected by secondary fibre quality. High temperature and pressure during the drying stage causes irreversible changes in fibre morphology, which is the mainly responsible for the considerable reduction in the swelling and bonding ability (strength and number of bonds) [1, 2, 3]. Additionally, the reduced dewatering ability of these pulps is a major problem during paper manufacture as they decrease the speed on the paper machine and worsen sheet formation [4]. Secondary fibre upgrade is difficult and sometimes unpredictable, as the samples to be treated vary along with their history. Traditional upgrade methodologies have been used to improve secondary fibre properties, but the results are most of the times insufficient [1, 5]. Different reports suggest that treating pulps with enzymes and refining could overcome these problems [4, 6, 7, 8, 9]. More recently, Cellulose-Binding Domains (CBD’s) usage has been shown as an interesting tool to modify recycled fibres properties

Modification of secondary pulp fibre fractions by enzymatic treatment

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Enzymatic modification of paper fibres

The enzymatic mode of action in paper fibre upgrading is still uncertain. In an attempt to clarify how enzymes modify pulp and paper properties, several parameters were analysed in the present work: (i) thermal analysis of the water–solid surface interactions; (ii) fibre cake permeability; (iii) particle size analysis. The results obtained suggest that enzymes modify the interfacial properties of fibres, increasing the water affinity, which in turn change the technical properties of pulp and paper, such as drainability and strength. The modification of paper and pulps following a treatment with cellulosebinding domains further supports this hypothesis

Effects of enzymatic treatment and refining on the properties of recycled pulp

The effect of refining and enzymatic treatment on secondary fibre properties is shown. The following treatment sequences were studied: (i) refining; (ii) refining + enzymatic treatment; (iii) enzymatic treatment + refining; (iv) enzymatic treatment. The effectiveness of the methods was evaluated by measuring physical and mechanical properties of pulp and paper (drainage rate, burst, tensile and tear indexes). The obtained data revealed that combined refining and enzymatic treatment can be considered as a valuable methodology to upgrade recycled pulps. The first is responsible for increasing burst and tensile resistance. The second, if developed under controlled conditions, alloes better drainage, with only slight variation on paper mechanical properties

Laboratory paper pulp deinking : an evaluation based on image analysis, ISO Brightness and ERIC

Image analysis, ERIC and ISO Brightness measurements were used to evaluate the effectiveness of laboratory deinking assays. The accurate measurement of the residual ink amount is difficult and the results depend on the methodology used. The three techniques correlate only when the same paper pulp sample is analysed and when the ink particle size distribution profile is similar. As the relative amount of each particle size depends on the deinking protocol used, the ink removal effectiveness is measured differently according to each test method. Image analysis was shown to be the most reliable method

Enzymatic depolymerisation of cellulose

Cellulose degree of polymerisation (DP) was determined in paper pulps and commercial powder celluloses before and after the enzymatic treatment with a blend of cellulases and hemicellulases. Three different methods were used: (i) chemical method, based on the measurement of the cellulose reducing power; (ii) viscosimetry; and (iii) gel permeation chromatography. Although based in very different principles, the three methods find similar DP values in the case of pure cellulose with narrow molecular weight distributions. The chemical method is more sensitive to detect enzymatic depolymerisation and appears to provide a good estimation of the number-average DP. GPC data offers more detailed information about the enzymes mode of action on the fibres, showing that cellulose hydrolysis in the presence of the commercial preparation Celluclast 1.5L follows a layer-by-layer solubilisation mechanism.University of Beira Interior – Department of Paper Science and Technology; Portucel Viana

Tecnologias alternativas para a melhoria das características da fibra secundária

O presente trabalho tem por objectivo o estudo da utilização de enzimas e domínios das enzimas responsáveis pela ligação à celulose (Cellulose Binding Domains - CBD's) para melhoria das propriedades de fibra secundária. Uma amostra de fibra secundária proveniente da desintegração de cartão (Portucel Viana) foi tratada por via enzimática e por adição de CBD's. O tratamento enzimático permitiu o aumento da drenabilidade, embora as propriedades de resistência tenham diminuído. A adição de CBD's conduziu a resultados bastante satisfatórios, permitindo o aumento simultâneo da drenabilidade da pasta e da resistência do papel

Preliminary studies on enzymatic deinking

Results on enzymatic deinking of paper pulps are shown. The process includes paper pulping, with an enzymatic cocktail, followed by flotation and dewatering. Three different wastepaper samples were used and tested. The deinking of the pulp was monitored by image analysis. Physical, mechanical and optical properties of pulp and paper were also determined. The obtained data revealed the effectiveness of the assayed enzyme preparation. However, enzyme use needs further optimisation as paper strenght properties suffered important alteration