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Furnishing autohydrolyzed poplar weakly alkaline P-RC APMP to make lightweight coated base paper, TAPPI Journal February 2022
ABSTRACT: This work investigated the effects of autohydrolysis pretreatment severity on poplar (Populus tomentosa Carr.) woodchips used to make a type of high-yield pulp (HYP) known as preconditioning followed by refiner chemical treatment, alkaline peroxide mechanical pulp (P-RC APMP). It also investigated the ratios for partially replacing sodium hydroxide (NaOH) with magnesium oxide (MgO) in the high-consistency (HC) retention stage of the P-RC APMP process on the obtained HYP’s properties. The results show that the pretreatment severity of autohydrolysis at combined hydrolysis factor (CHF) = 10.77 and the 50 wt% ratio for partially substituting NaOH with MgO were the optimum conditions for making light-weight coated (LWC) base paper. Compared to the conventional P-RC APMP, the optimized P-RC APMP had similar bulk and higher tensile, burst, and tear indices, as well as opacity, but a slightly lower ISO brightness. When the optimized P-RC APMP and commercial softwood bleached sulfate pulp (SBKP) were blended to make LWC base paper, the most favorable pulp furnish was comprised of 50% optimized P-RC APMP and 50% commercial SBKP. The obtained LWC base paper handsheet had better bulk, and its other properties could also meet the require-ments of LWC base paper.
Journal articles
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The Shendye-Fleming OBA Index for paper and paperboard, TAPPI Journal March 2022
ABSTRACT: We are proposing a new one-dimensional scale to calculate the effects of optical brightening agents (OBA) on the bluish appearance of paper. This index is separate from brightness and whiteness indices.In the paper industry, one-dimensional scales are widely used for determining optical properties of paper and paperboard. Whiteness, tint, brightness, yellowness, and opacity are the most common optical properties of paper and paperboard. Most of the papers have a blue cast generated by addition of OBA or blue dyes. This blue cast is given because of the human perception that bluer is whiter, up to a certain limit. To quantify this effect, it is necessary to determine how much blue cast paper and paperboard have. As the printing industry follows the ISO 3664 Standard for viewing, which has a D50 light source, this also plays a very important role in showing a blue cast. Color perception is based on light source and light reflected from an object. The ultraviolet (UV) component in D50 interacts with OBA to provide a reflection in the blue region of the visible spectrum. Use of a UV blocking filter results in measurements without the effect of emission in the blue region. This difference is used in determining the OBA effect in the visible range of the paper. This equation is known as the Shendye-Fleming OBA Index.
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Control of malodorous gases emission from wet-end white water with hydrogen peroxide, TAPPI Journal October 2021
ABSTRACT: White water is highly recycled in the papermaking process so that its quality is easily deteriorated, thus producing lots of malodorous gases that are extremely harmful to human health and the environment. In this paper, the effect of hydrogen peroxide (H2O2) on the control of malodorous gases released from white water was investigated. The results showed that the released amount of total volatile organic compounds (TVOC) decreased gradually with the increase of H2O2 dosage. Specifically, the TVOC emission reached the minimum as the H2O2 dosage was 1.5 mmol/L, and meanwhile, the hydrogen sulfide (H2S) and ammonia (NH3) were almost completely removed. It was also found that pH had little effect on the release of TVOC as H2O2 was added, but it evidently affect-ed the release of H2S and NH3. When the pH value of the white water was changed to 4.0 or 9.0, the emission of TVOC decreased slightly, while both H2S and NH3 were completely removed in both cases. The ferrous ions (Fe2+) and the copper ions (Cu2+) were found to promote the generation of hydroxyl radicals (HOœ) out of H2O2, enhancing its inhibition on the release of malodorous gases from white water. The Fe2+/H2O2 system and Cu2+/H2O2 system exhibited similar efficiency in inhibiting the TVOC releasing, whereas the Cu2+/H2O2 system showed better perfor-mance in removing H2S and NH3.
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The role of hornification in the deterioration mechanism of physical properties of unrefined eucalyptus fibers during paper recycling, TAPPI Journal February 2024
ABSTRACT: Physical properties of cellulosic paper deteriorate significantly during paper recycling, which hinders the sustainable development of the paper industry. This work investigates the property deterioration mechanism and the role of hornification in the recycling process of unrefined eucalyptus fibers. The results showed that during the recycling process, the hornification gradually deepened, the fiber width gradually decreased, and the physical properties of the paper also gradually decreased. After five cycles of reuse, the relative bonding area decreased by 17.6%, while the relative bonding force decreased by 1.8%. Further results indicated that the physical property deterioration of the paper was closely related to the decrease of fiber bonding area. The fiber bonding area decreased linearly with the reduction of re-swollen fiber width during paper recycling. Re-swollen fiber width was closely related to the hornification. Hornification mainly reduces the bonding area of unrefined eucalyptus fiber rather than the bonding force. The work elucidates the role of hornification in the recycling process of unrefined eucalyptus fibers and the deterioration mechanism of paper physical properties, which will be helpful to control the property deterioration of paper and achieve a longer life cycle.
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Determining operating variables that impact internal fiber bonding using Wedge statistical analysis
ABSTRACT: In this study, Wedge statistical analysis tools were used to collect, collate, clean up, plot, and analyze several years of operational data from a commercial paper machine. The z-direction tensile (ZDT) and Scott Bond tests were chosen as representative of fiber bond strength. After analyzing thousands of operational parameters, the ones with the most significant impact upon ZDT involved starch application method, starch penetration, and the amount of starch applied. Scott bond was found to be significantly impacted by formation and refining. Final calendering of the paper web has also shown an impact on internal fiber bonding.
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Factors affecting the free shrinkage of handsheets: apparent density, fines content, water retention value, and grammage, TAPPI JOURNAL June 2018
Factors affecting the free shrinkage of handsheets: apparent density, fines content, water retention value, and grammage, TAPPI JOURNAL June 2018
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Creating adaptive predictions for packaging-critical quality parameters using advanced analytics and machine learning, TAPPI Journal November 2019
ABSTRACT: Packaging manufacturers are challenged to achieve consistent strength targets and maximize pro-duction while reducing costs through smarter fiber utilization, chemical optimization, energy reduction, and more. With innovative instrumentation readily accessible, mills are collecting vast amounts of data that provide them with ever increasing visibility into their processes. Turning this visibility into actionable insight is key to successfully exceeding customer expectations and reducing costs. Predictive analytics supported by machine learning can provide real-time quality measures that remain robust and accurate in the face of changing machine conditions. These adaptive quality “soft sensors” allow for more informed, on-the-fly process changes; fast change detection; and process control optimization without requiring periodic model tuning.The use of predictive modeling in the paper industry has increased in recent years; however, little attention has been given to packaging finished quality. The use of machine learning to maintain prediction relevancy under ever-changing machine conditions is novel. In this paper, we demonstrate the process of establishing real-time, adaptive quality predictions in an industry focused on reel-to-reel quality control, and we discuss the value created through the availability and use of real-time critical quality.
Journal articles
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Understanding wet tear strength at varying moisture content in handsheets, TAPPI Journal January 2021
ABSTRACT: A laboratory study was conducted looking at the effects of moisture content on wet tear strength in handsheets. Three different wetting techniques were used to generate the wet tear (Elmendorf-type) data at varying moisture levels, from TAPPI standard conditions (dry) to over 60% moisture content (saturated). Unbleached hardwood and softwood fiber from full-scale kraft pulp production were used. The softwood fiber was refined using a Valley beater to reduce freeness. Handsheets were made with a blend of hardwood and softwood and with refined softwood, without the addition of wet-end chemistry. The resulting grams-force tear data obtained from the test was indexed with basis weight and plotted versus both moisture content and dryness. As moisture content levels in the handsheets increased, the wet tear strength also increased, reaching a critical maximum point. This marked a transition point on the graph where, beyond a critical moisture content level, the tear strength began to decline linearly as moisture increased. This pattern was repeated in handsheets made from a blend of hardwood and softwood and from 100% refined softwood.
Journal articles
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The effect of microfibrillated cellulose on the wet-web strength of paper, TAPPI Journal January 2021
ABSTRACT: The wet-web strength of paper immediately after the press section of a paper machine is a critical factor in determining machine runnability. However, it is difficult to determine at commercial scale, because the web has to be broken and production interrupted in order to obtain a sample for measurement. The use of microfibrillated cellulose (MFC) is believed to increase wet-web strength, as it has allowed filler level increases of 10% or more on many commercial paper machines. In this paper, we describe a laboratory method for estimating the effect of MFC on wet sheet strength after press-ing, as well as actual measurements of wet-web strength from a pilot paper machine trial. These experiments have demonstrated the positive effect of MFC. At solids contents in the range typically observed after pressing, sheets with MFC at fixed filler content are significantly stronger, but also wetter, than those without it. When the use of MFC is combined with a typical increase in filler content, the wet web remains slightly stronger, but also becomes drier than the reference condition. These results are compatible with the theory put forward by van de Ven that wet-web strength is mainly a result of friction between entangled fibers, and they also suggest that the presence of MFC increases this friction.
Journal articles
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Advanced real-time digital microscopy of foaming processes, TAPPI Journal January 2023
ABSTRACT: The properties of aqueous foams play a major role in foam forming and foam coating. Inline real-time foam measurements provide highly desired opportunities for optimization and control of foaming processes. This paper presents inline digital microscopy measurements of aqueous foams in foaming processes. It presents methods for providing detailed information on foam quality parameters, such as foam density and foam homogeneity in real time from the process. In addition, this study evaluates the performance of transillumination and front-light illumination in imaging of foams. The tests show very good results for the transillumination approach. Limitations of the image-based optical technique are discussed, and the precision of bubble size distribution measurement is assessed with a certificated reference substance. The measured foam densities are compared against the reference foam densities in the range 100•300 g/L, providing a linear correlation with R2 value of 0.99. In the case of heterogenous foams with a wide bubble size distribution, the bubble size-dependent dimensionless depth of field must be taken into account to obtain accurate estimates of foam density. Bubble-scale foam homogeneity is described by the standard deviation of bubble size distribution in foam.