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Showing papers in "Appita Journal in 2007"


Journal Article
TL;DR: In this article, the effect of eucalyptus chemical pulp fines on filler retention and paper properties was examined, and the benefit of pre-mixing fines and fillers before addition, compared to separate addition, was evaluated.
Abstract: The effect of eucalyptus chemical pulp fines on filler retention and paper properties was examined. Different quantities and qualities of fines were studied, and the benefit of pre-mixing fines and fillers before addition, compared to separate addition, was evaluated. As expected, fines enhanced paper properties, but retarded the drainage. The qualities of fines had a strong influence on paper strength properties and drainage of the pulp furnish. Fillers did not retard drainage; they had a positive effect on optical properties but impaired paper strength. In general, the retention of fillers was minor compared to fines. Retention, strength and optical properties of resultant paper were improved by addition of pre-mixed fines and fillers to pulp furnish. This improvement was achieved at the cost of significantly reduced drainage.

47 citations


Journal Article
TL;DR: In this article, the behaviour of four different polymeric fixatives in the presence of wood extractive components with and without fibres was investigated, and it was shown that polyethylenimine (PEI) was shown to cause nonselective deposition onto both fibre and non-fibre surfaces, as well as reduce the amount of wood extracts in the dissolved and colloidal phase.
Abstract: The behaviour of the four different polymeric fixatives in the presence of wood extractive components with and without fibres was investigated. Cationic polyacrylamide (CPAM) and high and medium charge co-polymers of polyacrylamide and poly(diallyl-dimethyl ammonium chloride (polyDADMAC) were found to stabilise the wood extractive colloids in solution, as well as to attach the wood resins to the fibre. Polyethylenimine (PEI) was shown to cause non-selective deposition onto both fibre and non-fibre surfaces, as well as reduce the amount of wood extractives in the dissolved and colloidal phase. PEI was also found to preferentially interact with triolein and the medium charge co-polymer exhibited preference in fibre-attachment of oleic acid.

16 citations


Journal Article
TL;DR: In this paper, an ECF-bleached softwood pulp was treated with carboxymethyl cellulose (CMC), and the CMC sorptions were carried out under specified conditions (60 C, pH 12.5, CMC addition 1%, pulp consistency 5%) in order to introduce more charged groups on the surface of fibres.
Abstract: An ECF-bleached softwood pulp was treated with carboxymethyl cellulose (CMC). The CMC sorptions were carried out under specified conditions (60 C, pH 12.5, CMC addition 1%, pulp consistency 5%) in order to introduce more charged groups on the surface of fibres. The beating of pulp, pHvalue, degree of substitution (DS) of CMC and electrolyte concentration had a major impact on the amount of CMC attached. The increase in the water retention values (WRV) of the CMC-treated pulps was very significant, and was associated with improved internal (approximately 50% increase) and tensile strengths of resultant handsheets. These handsheets prepared in water and in electrolyte solution were further studied by electron microscopy (ESEM). As the sorption conditions used are similar to those in papermaking systems, this surface modification method may be advantageous in practice, for example, after the refining stage.

14 citations


Journal Article
TL;DR: In this paper, a modified Page equation is proposed based on a newly developed method to calculate the relative bonded area from sheet density and fibre shape, which is used as a fitting parameter.
Abstract: The Page equation is the most widely used equation to predict the tensile strength of paper. In this paper, the derivation of the Page equation is examined critically and a modified Page equation is proposed based on a newly developed method to calculate the relative bonded area from sheet density and fibre shape. The predictions of the original and modified Page equations were then tested against twelve sets of sheets made from different unbleached, never dried radiata pine kraft pulps. The bond strength was used as a fitting parameter. The best fit bond strengths varied so widely as to make it impossible to use either the original or modified Page equation to predict tensile strength, without prior knowledge of the bond strength applicable to that data set.

13 citations


Journal Article
TL;DR: In this paper, a split application of low charges of chlorine dioxide on each D stage allows selective reactions on free phenolic groups and avoids waste of ClO2 in secondary reactions, leading to a 30-35% reduction in the AOX release.
Abstract: Novel ECF sequences using split application of chlorine dioxide have been designed and optimized. The application of low charges of chlorine dioxide on each D stage allows selective reactions on free phenolic groups and avoids waste of ClO2 in secondary reactions. Applying this new concept allowed a 30-35% reduction of ClO2 during prebleaching. Rapid DR and ER stages involving rapid mixing and low retention times (2 min) were also successfully tested at low ClO2 charges. Avoiding additional washers can be obtained by suppressing washing between D and E. This was shown to be a good strategy provided an additional amount of sodium hydroxide to counterbalance the acidic carry-over of the D stage was added. As a result, the AOX release was significantly reduced compared to conventional D0E prebleaching.

13 citations


Journal Article
TL;DR: Two different a-Keggin type polyoxometalates (POMs) in conjunction with a commercial silicomolybdate (SiMo) preparation were tested in a catalytic oxygen bleaching concept as discussed by the authors.
Abstract: Two different a-Keggin type polyoxometalates (POMs) in conjunction with a commercial silicomolybdate (SiMo) preparation were tested in a catalytic oxygen bleaching concept. The idea of this biomimetic concept is to harness the radical species produced in reactions of O2 to effective delignification through formation of activated hydrogen peroxide in situ. Results of the laboratory bleaching trials showed modest delignification only. It is concluded that the probable reason for the rather poor delignification results is the low reoxidation rate of the tested POMs: The functionality of the catalytic bleaching concept presented should be tested further with catalysts possessing faster regeneration rates. Two different a-Keggin type polyoxometalates (POMs) in conjunction with a commercial silicomolybdate (SiMo) preparation were tested in a catalytic oxygen bleaching concept. The idea of this biomimetic concept is to harness the radical species produced in reactions of O2 to effective delignification through formation of activated hydrogen peroxide in situ. Results of the laboratory bleaching trials showed modest delignification only. It is concluded that the probable reason for the rather poor delignification results is the low reoxidation rate of the tested POMs: The functionality of the catalytic bleaching concept presented should be tested further with catalysts possessing faster regeneration rates.

12 citations


Journal Article
TL;DR: An acoustic technique, with microphone placed near the print nip exit on a sheet-fed offset press during trial printing of newsprint, was used to provide information relating to splitting of the...
Abstract: An acoustic technique, with microphone placed near the print nip exit on a. sheet-fed offset press during trial printing of newsprint, was used to provide information relating to splitting of the ...

6 citations


Journal Article
TL;DR: In this article, the effect of PCC filler clustering on sheet properties is investigated and the authors conclude that fillers agglomerate to clusters that are strong enough to resist pressures during handsheet making and lead to increased bulk of the sheet.
Abstract: This paper considers the effect of PCC filler clustering on sheet properties. We used three different PCC grades that have very different structures and we applied two different methods to prepare handsheets. On the basis of experimental measurement results, cross-sectional SEM-images of handsheets and KCL-PAKKA simulations we conclude that fillers agglomerate to clusters that are strong enough to resist pressures during handsheet making and lead to increased bulk of the sheet.

6 citations


Journal Article
TL;DR: In this paper, a novel measurement technique, based on infrared thermography, has been applied for characterizing the thermal properties of paper with high spatial resolution, which is termed as active thermography.
Abstract: A novel measurement technique, based on infrared thermography, has been applied for characterizing the thermal properties of paper with high spatial resolution. The technique is termed as 'active thermography' since the temperature response of a paper sheet is observed and analyzed with respect to an external periodic heating. Through the analysis of the temperature response of the paper surface in the Fourier domain for different modulation frequencies of incident heat flux, heat transfer velocities across the solid-gas interface can be estimated. This in turn results in estimation of the heat capacity of paper by solving the heat balance equations of the system. The thermal heating is applied spatially homogeneously. Therefore all these calculations are performed for all pixels in the image sequence. A spatial distribution and temporal development of all these parameters were visualized. Also the technique shows high potential to the non-invasive dynamic measurements in paper drying.

4 citations


Journal Article
TL;DR: In this paper, the influence of ionic strength during pulping (measured as sodium ion concentration) on pulp strength (evaluated as tear index vs. tensile index) and...
Abstract: A study was undertaken in order to investigate the influence of ionic strength during pulping (measured as sodium ion concentration) on pulp strength (evaluated as tear index vs. tensile index) and ...

3 citations


Journal Article
TL;DR: In this article, the authors tried to explain the variation in reactivity for spruce sulfite fibres principally by comparing the reactivity of fibres taken from different parts of the spruce tree.
Abstract: Carboxymethyl cellulose (CMC) is produced from dissolving pulp, usually of the sulfite type, although prehydrolysed kraft pulp can also be used. In industrial production of CMC, a certain amount of the pulp fibres will not fully react with the monochloroacetic acid in the CMC process and an undesirable amount of fibres are therefore still present in the final CMC. This naturally downgrades the CMC quality. The laboratory study reported here has tried to explain the reason for this variation in reactivity for spruce sulfite fibres principally by comparing the reactivity of fibres taken from different parts of the spruce tree. Compression wood was believed to be especially problematic but it is shown that it is probably not the origin of the un-reacted fibres. Instead it is believed that the source of slowly reacting fibres that end up as impurities in the CMC is 1) the presence of poorly cooked and bleached fibres in the dissolving pulp and/or 2) an excessively low content of galactoglucomannan in the pulp.

Journal Article
TL;DR: In this paper, the authors focus on how deformations of the board might lead to print non-uniformities, and the mechanisms behind striping in halftone flexo post-printing.
Abstract: Print non-uniformity problems are a major concern for flexo post-printers. Many of these non-uniformities are suspected to be caused by the corrugated board structure itself. Striping is the most obvious one, but also other print quality problems might be structure related. This work focuses on how deformations of the board might lead to print non-uniformities, and the mechanisms behind striping in halftone flexo post-printing. The problems were analysed by using finite element models to simulate deformed board and halftone dot conditions in the printing nip. Striping was found to be caused by differences in coverage in different areas due to pressure variation related dot gain. Deformations of the board were shown to have a potential of causing print non-uniformities by affecting the pressure distribution.

Journal Article
TL;DR: Image analysis, ERIC and ISO brightness measurements were used to evaluate the effectiveness of laboratory deinking assays and image analysis was shown to be the most reliable method.
Abstract: 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.

Journal Article
TL;DR: In this article, the influence of different bleaching sequences on the fibre surface properties of softwood kraft pulp, before and after ageing, was determined by measuring the Dynamic Contact Angle (DCA) in water and by performing Electron Spectroscopy for Chemical Analysis (ESCA) on the pulp fibres.
Abstract: The aim of this study was to determine the influence of different bleaching sequences on the fibre surface properties of softwood kraft pulp, before and after ageing. This was done by measuring the Dynamic Contact Angle (DCA) in water and by performing Electron Spectroscopy for Chemical Analysis (ESCA) on the pulp fibres. The study, which was conducted on Elemental Chlorine Free (ECF) and Totally Chlorine Free (TCF) bleached softwood pulps, showed that there were measurable fibre surface differences between bleached pulps, depending on the bleaching method applied. The DCA was consistently higher for the TCF fibres. The change in the fibre properties after a storage period of six months, measured as DCA, was more pronounced for the ECF fibres. A higher contact angle of the fibres after storage indicated either a migration of extractives and/or lignin from the fibre wall to the surface or a change in the components on the fibre surface which caused it to become more hydrophobic.