Low Basis Weight Research Articles

Estimating limits of wet pressing on paper machines

Water removal by wet pressing on paper machines depends on many factors such as press impulse, pressure, basis weight, equilibrium moisture, rewet, furnish, and fabric properties. These factors must be considered together to estimate wet pressing limits, such as the possibility of attaining 65% solids content on commercial paper machines. We have made such estimates employing the Decreasing Permeability Model (DPM) of wet pressing. This paper describes the utility of this approach and discusses some findings, such as the large dependence of low basis weight grades on equilibrium moisture content, maximum nip pressure, and rewet. The model also estimates the impact of basis weight, web temperature, double-felting, and incoming web solids on water removed.

Effect of electrospinning parameters on the air filtration performance using electrospun polyamide-6 nanofibers

Due to their high filtration efficiency and low basis weight nanofibrous filters are suitable for filtration applications. The objective of this study was to investigate the effect of electrospinning parameters including polymer solution concentration (10-15 wt.%), applied voltage (15-25 kV) and tip-collector distance (7.5-12.5 cm) on the filtration efficiency of polyamide (PA) nanofibers. The morphology of the PA nanofibers was characterized using scanning electron microscope (SEM) analysis. The SEM image results indicated that the average fiber diameter of PA nanofibers was 220 nm at PA solution concentration of 12.5 wt.%, applied voltage of 20 kV, tip-collector distance of 10 cm, flow rate of 0.5 mL h-1, temperature of 25 ?C and humidity of 40%. The obtained results showed that the highest quality factor and efficiency of 7.02?10-2 Pa-1 and 96% were optimal parameters for nanofibrous filters during 30 and 240 min of electrospinning time, respectively. The presented study showed that the morphology optimization of nanofibers is an effective method for improvement of filtration performance.

The Fundamental Absorbency Mechanisms of Hygiene Paper

A hygiene paper is characterized by having low density and low basis weight (i.e., weight per area). Its main constituent is cellulose fiber, known as pulp. Since hygiene paper including tissue (i.e., bathroom- and facial-tissue), paper towel, and napkins has low density and low basis weight, it is thin like a paper sheet. A hygiene paper requires good softness, strength, and absorbency. With regards to absorbency, a hygiene paper should be able to pick up liquid spills as fast as possible before it is disposed of. In short, its lifetime is extremely short, lasting only for a few seconds. The Lucas-Washburn theory has been validated from the absorbency data of some commercial tissue products available in the patent literature. The theory suggests that absorbency amount (Q) should be proportional to the square root of time, t 1/2 , in a plot of Q against t 1/2 . Such a plot is referred to as the Lucas-Washburn plot and the slope is known as the Lucas-Washburn slope, K. A higher value of K indicates a higher speed of absorption. The slope, K, is a function of the surface tension and the viscosity of the liquid, the wettability of the solid surface by the liquid, and the porous structure of the product. The wettability depends on the surface roughness (or profile) and the surface heterogeneity. It is recognized that the absorbency should depend on the absorbency measurement methods employed. Although many absorbency measurement methods have been implemented, only a few have been standardized. The standardization of absorbency test methods is necessary to compare the products objectively without ambiguity.

Silk nanofibers as high efficient and lightweight air filter

Silk is a widely available, edible, biocompatible, and environmentally sustainable natural material. Particulate matter (PM) pollution has drawn considerable attention because it is a serious threat to public health. Herein, we report a human-friendly silk nanofiber air filter, which exhibits superior filtration efficiency for both PM2.5 and submicron particles with obviously low pressure drop and low basis weight compared to typical commercial microfiber air filters. Additionally, other functions such as antibacterial activity could be easily integrated into the silk nanofiber air filters, enabling the fabrication of multifunctional air filters. All the above characteristics, combined with the natural abundance and biocompatibility of silk, suggest a great potential for the use of silk nanofibers as air filters, especially as comfortable and personal air purifiers.

Air Permeability and Moisture Management Properties of Electrospun Nanofiber Membranes

Recently, electrospun nanofiber membranes (ENMs) have been received an increased attention in personal protective clothing owing to their excellent filtration efficiency and low basis weight as filtering materials. However, high resistance to air flow is a major drawback of ENMs which in turn effect on comfort. In addition, comfort properties such as moisture management of ENMs need to be evaluated for practical applications. It is argued that air permeability and moisture management influenced by selection of electrospinning process parameters. This research studied the effect of collector speed and deposition time on the air permeability of ENMs. Polyacrylonitrile nanofibers that had the diameter in the range of 291-877 nm were fabricated. The deposition time significantly influenced air permeability, unlike collector speed. Hence a short deposition time is desirable. A good correlation was found between the theoretical porosity and experimental air permeability of ENM. Furthermore, it was found that moisture management properties of ENM require improvements for personal protective clothing.

The comparative study of aerosol filtration by electrospun polyamide, polyvinyl acetate, polyacrylonitrile and cellulose acetate nanofiber media

Nanofiber media produced from different polymers via electrospinning were examined for the removal of aerosol particles from the air flow. The polymeric materials used as a filter media included polyamides 6 (PA6) and 6/6 (PA6/6), polyvinyl acetate (PVAc), polyacrylonitrile (PAN), and cellulose acetate (CA). The comparative filtration performance of the single-ply and multi-ply nanofiber media mats was evaluated. The measurements of filtration efficiency and estimation of quality factors (QF) were performed for monodisperse 100 and 300nm polystyrene latex and polydisperse NaCl particles. The results revealed that PVAc nanofiber media filter (PVAc_60) due the unique morphology of beaded nanofibers combined the highest QF and the high filtration efficiency: 0.055Pa−1 (98.79%) for 100nm particles and 0.042Pa−1 (96.79%) for 300nm particles accordingly. The PAN nanofiber media also showed relatively high filtration properties, while other nanofiber media (PA and CA) with high quality factors did not exceed filtration efficiency of 91%. The comparison of one-ply and multi-ply nanofiber media, characterized by lower basis weight, showed that multi-ply structures only slightly increase filtration properties for 100 and 300nm particles, in some cases worsening filtration properties.

Control performance of paper-based blood analysis devices through paper structure design.

In this work, we investigated the influence of paper structure on the performance of paper-based analytical devices that are used for blood analysis. The question that we aimed to answer is how the fiber type (i.e., softwood and hardwood fibers) influences the fiber network structure of the paper, which affects the transport of red blood cells (RBCs) in paper. In the experimental design, we isolated the influence of fiber types on the paper structure from all other possible influencing factors by removing the fines from the pulps and not using any additives. Mercury porosimetry was employed to characterize the pore structures of the paper sheets. The results show that papers with a low basis weight that are made with short hardwood fibers have a higher porosity (i.e., void fraction) and simpler pore structures compared with papers made with long softwood fibers. RBC transport in paper carried by saline solution was investigated in two modes: lateral chromatographic elution and vertical flow-through. The results showed that the complexity of the paper's internal pore structure has a dominant influence on the transport of RBCs in paper. Hardwood fiber sheets with a low basis weight have a simple internal pore structure and allow for the easy transport of RBCs. Blood-typing sensors built with low basis weight hardwood fibers deliver high-clarity assays. Softwood fiber papers are found to have a more complex pore structure, which makes RBC transport more difficult, leading to blood-typing results of low clarity. This study provides the principle of paper sheet design for paper-based blood analysis sensors.

Aligned carbon nanotube sheet high efficiency particulate air filters

Aerosol filters, made with conventional micro-fiber fabrics, are designed to efficiently capture small particles from the air. Filters constructed of nano-fiber fabric structures provide even greater filtration efficiency than conventional micro-fiber fabrics due to their higher surface area and smaller pore size. Carbon nanotubes (CNTs) are very small diameter fibers that have the potential to be integrated into filters to further increase particle capture efficiency. In this study, CNT sheets, drawn from millimeter tall CNT arrays, were integrated between traditional micro-fiber fabrics to produce aerosol filters. The filtration performance of the novel filters showed that when the number of CNTs layers increased, the filtration efficiency increased dramatically, while the pressure drop also increased. In order to meet high efficiency particulate air (HEPA) filter requirements with a reasonable pressure drop, CNTs were laid in a cross-plied structure within the filter. The results demonstrated that the three layer cross-ply structure provided 99.98% filtration efficiency at 0.3μm particle size at a 10cm/s face velocity, making it a viable method for producing low basis weight HEPA filters utilizing CNTs as the main filtration component.

Bondable and Biodegradable Cellulosic Opacifiers

Fibers extracted from red algae produced a comparable increase in paper opacity to that produced by experimented inorganic fillers, calcium carbonate. Red algae fibers consist predominantly of cellulose and contain less than 1% inorganic ash. They are comparable to wood fibers in terms of their bonding, combustion, recycling, and biodegradation. While the bonding strength properties of paper decreased with an increase of inorganic fillers in the amount added to the paper, the red algae fibers maintained their bonding properties. These special characteristics seem to stem from the relatively large specific surface areas of the red algae fibers, which are relatively short (0.4–0.8 mm) and narrow (2–4 μm). Moreover, the addition of red algae fibers to the paper increased the paper stretch and folding endurance in proportion to their added amount. These special properties of red algae fibers may find application in low-basis weight printing paper grades that require high opacity and strength.

低坪量化に適したPAM系表面紙力剤

低坪量化に適したPAM系表面紙力剤

SURFACE SIZING APPLICATION OF WATERBORNE EPOXY RESIN ON LOW BASIS WEIGHT PAPER

Reducing basis weight could lead to huge savings of forest resources as well as energy consumption and waste treatment in the papermaking process. However, low basis weight paper generally lacks normal strength and stiffness. The lower the basis weight of the paper, the more important is surface sizing. Highly cross-linked cured epoxy resin, due to its epoxy group and phenyl group, has gained such outstanding mechanical properties and dimensional stability that it could be utilized to enhance paper strength and stiffness through surface sizing when incorporated with oxidized starch. In this study, the impacts of sizing volume, fluid temperature, curing agent, and curing system dosage on sizing were investigated. Our results indicated that a rigid resin layer and interpenetrating polymer network formed on the surface and in the inner layer of the paper, respectively. The formed resin layers strongly support the paper and thus resulted in the improvement of strength and stiffness.

Alkaline peroxide mechanical pulping of fast-growth paulownia wood

Alkaline peroxide mechanical pulping of paulownia wood harvested from exotic tree plantations in northern Iran was investigated. The fiber length, width, and cell wall thickness of this wood were measured as 0.82 mm, 40.3 μm, and 7.1 μm, respectively. The chemical composition including cellulose, lignin, and extractives soluble in ethanol-acetone, 1% NaOH, hot and cold water was determined as 49.5%, 25%, 12.1%, 26.9%, 11.4%, and 8.1% respectively. The ash content of this wood was 0.45%. Pre-washed chips were chemically treated at 70°C for 120 minutes with different combinations of three dosages (1.5, 3, and 4.5%) of hydrogen peroxide and three dosages (1.5, 3, and 4.5%) of sodium hydroxide prior to defibration. Other chemicals including DTPA, sodium silicate, and MgSO4 were constant at 0.5%, 3%, and 0.5%, respectively. The results showed that using a 1.5% hydrogen peroxide and 4.5% sodium hydroxide charge, the brightness of APMP pulp reached 68.7% ISO and higher chemical dosages did not improve the brightness; however, to produce APMP pulp with higher strength, a sodium hydroxide charge of 4.5% was needed. The tensile strength, tear strength, burst strength indices, and bulk density of the APMP pulp produced from 1.5% hydrogen peroxide and 4.5% sodium hydroxide were measured as 15.5Nm/g, 6.54mN.m2/g, 0.56kPa.m2/g, and 3.47cm3/g, respectively. The resulting pulp was bulky and is suitable for use in the middle layer of boxboard to provide the desired stiffness with a lower basis weight.

Surface sizing application of waterborne epoxy resin on low basis weight paper

Reducing basis weight could lead to huge savings of forest resources as well as energy consumption and waste treatment in the papermaking process. However, low basis weight paper generally lacks normal strength and stiffness. The lower the basis weight of the paper, the more important is surface sizing. Highly cross-linked cured epoxy resin, due to its epoxy group and phenyl group, has gained such outstanding mechanical properties and dimensional stability that it could be utilized to enhance paper strength and stiffness through surface sizing when incorporated with oxidized starch. In this study, the impacts of sizing volume, fluid temperature, curing agent, and curing system dosage on sizing were investigated. Our results indicated that a rigid resin layer and interpenetrating polymer network formed on the surface and in the inner layer of the paper, respectively. The formed resin layers strongly support the paper and thus resulted in the improvement of strength and stiffness.

Application of Precipitated Silica in Low Basis Weight Newspaper

Filler is one of the most important components of paper. Silica is a kind of excellent filler for its special chemical structure. Silica was prepared in the laboratory, and applied into paper. The dispersion properties of the silica with different sizes in paper sheets, the effect of smash on dispersion property of silica in paper sheets, the effect of silica on the zeta potential of newspaper pulp system, the effect of retention agent cationic polyacrylamide on zeta potential of newspaper pulp system and the effect of silica on properties of paper sheet were measured. The results show that the fineness of the silica used in paper is the most important factor which affects the dispersion. The addition of silica and the use of retention agent cationic polyacrylamide increase the zeta potential of the newspaper pulp system. The addition of precipitated silica increases the whiteness of paper slightly and the opacity obviously.

Filtration of nano-aerosol using nanofiber filter under low Peclet number and transitional flow regime

The objective of this study is to investigate the filtration of nano-aerosols (50–500 nm) using nanofiber filter for strong diffusion capture wherein Peclet number Pe drops to single digit and even below unity. The effect of strong slip flow or transitional flow, with the dimension of the flow domain comparable in order of magnitude to the distance of mean-free-path of air molecules (i.e. Knudsen number Kn f of order one), has also been investigated with nanofiber diameter reducing below 100 nm. Also, we examined implications due to use of very small diameter nanofibers. Nanofiber filters are made by electrospinning Nylon 6 (N6) nanofibers on microfiber substrate. The diameter of nanofibers electrospun from 12, 20, and 24% N6 solution are 94, 185, and 220 nm, respectively (corresponding Kn f of 1.44, 0.71, and 0.62). Previous studies showed that the conventional semi-empirical correlation as developed by Payet et al. [1] on single fiber efficiency due to diffusion mechanism ( η D ) as developed from moderate slip flow assumption offers good agreement with experimental results even when Kn f increases to 0.65 (i.e. transition flow regime) over Pe starting from 40 and dropping to 6. In this study, under large slip flow ( Kn f equals to 1.44), we show that Payet's correlation on η D deviating from measurements when Pe is below 10 and the deviation gets worse when Pe drops below unity. Therefore, Payet's correlation, pertaining only to moderate diffusion capture, underpredicts the single fiber capture efficiency for nano-particle or ultrafine particle (sized below 100 nm according to ISO Standard [2]), which may lead to respiratory [3] and cardiovascular [4] problems or diseases. As such, an improved empirical correlation on η D should be established based on new measurement to accurately assess the filter performance on these important particles for selection and sizing of filters in exercising preventive measures. In the study of effect of fiber diameter on capture efficiency and pressure drop, reducing d f from 185 to 94 nm facilitates the filtration of 50–500 nm nano-aerosol, but unfortunately elevates the pressure drop (Δ P). The benefit-to-cost effect is judged by the quality factor ( QF) which should be higher for filter with better performance. The QF of a filter with 185-nm nanofibers is higher than the one with 94-nm nanofibers when filtering 50–90 nm nano-aerosol, and vice versa when filtering 100–380 nm nano-aerosol. Filtration efficiency increases when nanofiber basis weight ( W) increases from 0.042 to 0.333 g m −2. However, the QF drops rapidly when W increases from 0.042 to 0.085 g m −2, and decreases slowly from W = 0.085 g m −2 onwards to W = 0.333 g m −2. As such, for a high performance filter a multi-layer filter formed from stacking up of a series of low basis weight nanofiber layers, each independently supported, is more favorable over using a single-layer nanofiber filter with the same total basis weight.

A method to determine lumen volume and collapse degree of pulp fibers by using bottleneck effect of mercury porosimetry

On applying mercury porosimetry to wood blocks or paper sheets, the “bottleneck” effect due to pits of fibers occurs and thus lumen volume can be determined from the weight increase due to the remaining mercury. However, in addition to the mercury in the lumen, some mercury drops may also remain in the space between fibers within a paper sheet. The mercury between fibers increased with an increase of basis weight. Thus, a large number of paper sheets of low basis weight, such as 10 g·m−2, should be used to determine the lumen volume of pulp fibers. Furthermore, in the case of fibers from mechanical pulp with many open cut fibers, mercury can retract from the open lumen such that the bottleneck effect due to pits does not occur. Therefore, the degree to which fibers are cut should also be considered for lumen volume determination. Although quantitative estimation of open cut fibers is difficult, the percentage of open cut fibers is quite low for the long fiber fraction. Thus, the remaining mercury for the long fiber fraction can be adopted as the lumen volume at least for practical purposes. Compared with the original lumen volume of the wood, the volumetric degree of fiber collapse was also estimated. Plausible values of almost 100% for lightly beaten KP and about 85% for slabwood thermomechanical pulp were obtained for the degree of collapse.

Felt Design for High Speed Printing Machines

Shoe press machines for H. S. P. G.(High Speed Printing Grade) have been actively introduced to the market places in the last few years. Technological advancements that are responsible for those machines demand superior performance from paper machine clothing.We believe that the combination of multi-layer base press felts and grooved shoe press belts are the most desirable to meet the required functions, such as stable runnability, efficient dewatering, less contamination and good smoothness.Laminated 2-layer or 3-layer felt designs take advantage of extremely fine cap basa fabric on the sheet side.Favorable results of the above combination have been reported in the commercial applications. Lower basis weight and higher density of felts combined with grooved belts, in particular, have enhanced water splash at out-going nip, resulting in improved sheet dryness.The latest generation of paper machines with no-draw configuration and design speed reaching 2, 000 meter per minute 6, 560 FPM) are becoming commercial reality.It is imperative to develop press felts and shoe press belts to most effectively tackle with additional issues such as “two-sidedness” and “re-wetting” as well as conventional felt and beit functions.

Random Fiber Networks and Special Elastic Orthotropy of Paper

We consider a particular in-plane elastic orthotropy observed experimentally for various types of paper, namely: S1111CS2222 2S1122D S1212 ,w hereSijkm are components of the in- plane compliance tensor. This is a statement of the invariance of in-plane shear compliance S1212, which has been observed in some studies but questioned in others. We present a possible explanation of this "special orthotropy" of paper, using an analysis in which paper is modeled as a quasi-planar random microstructure of interacting fiber-beams - a model especially well suited for low basis weight papers. First, it is shown analytically that without disorder a periodic fiber network fails the special orthotropy. Next, using a computational mechanics model, we demonstrate that two-scale geometric disorder in a fiber network is necessary to explain this orthotropy. Indeed, disordered networks with weak flocculation best satisfy this relationship. It is shown that no special angular distribution function of fibers is required, and that the uniform strain assumption should not be used. Finally, it follows from an analogy to the thermal conductivity problem that the kinematic boundary conditions, rather than the traction ones, lead quite rapidly to relatively scale-independent effective constitutive responses.

Roles of Press Felt in Press Section of Paper Machine

The functions required of press felt for paper machines are mainly water removal, web conveyance, and paper surface finish. The water removal performance of felts is closely related to steam consumption during the paper drying process and is a very important factor in determining energy consumption costs.Studies on water removal at the press section have been carried out by many researchers. The mechanism of water removal published by Wahlström in 1960 is the theory that is met with wide acceptance even today. Wahlström studied the process of water removal at the press nip which he divided into four phases and established a press model equation for sheet moisture ratio after the press nip based on peak pressure, flow resistance, evenness of pressure distribution, and rewetting.Nip peak pressure is the force required for pressing the sheet and squeezing the water out and is determined by machine and felt factors. Flow resistance is the resistance which occurred when the water flows at the cell walls, in between fibers, and at the inside of the felt while the pressure is loaded to both the sheet and felt. Even pressure distribution plays an important role in water removal at the press, especially in the case of a low basis weight sheet.Rewetting is water transference from the felt to sheet at the exiting side of the nip, caused by volume expansions of both the felt and sheet, capillary action, and water film splitting. Although water removal performance of felts plays an important role in cost reduction of paper production, felts need to have other critical functions. Therefore, it is very important for us feltmakers to have close discussions with paper makers on felt performance for designing the most suitable felts.

塗工紙の品質と印刷上の問題点

The printing world was dull especially in the field of the commercial printing, due to small demand in the depression that was caused by the high power of “YEN”, but it is becoming active as the economy in Japan grows up by promotion for inner demand.In the commercial printing field, we print matters in high quality, for instance catalogues, pamphlets, posters, handbills, and so on.Customers claims strictly for high qualitly, so about 90% of the papers we use is occupied by coated paper, including low-low weight coated paper.It is general that we select papers considering some factors that is the result of finished products, costs etc. Those papers are various in the grade and the basis weight.Recent trends are the tendency of the increasing of low-grade, low-basis weight, and the tendency of multi-colors and high speed for printing which is expected to last from now on.Therefore they are important subjects that we maintain and improve the printability for papers, as well as that we improve inks and printing machines.