Dissertations / Theses on the topic 'Handsheet'

For paper producers, an understanding of the development of strength properties in the paper is of uttermost importance. Strong papers are important operators both in the traditional paper industry as well as in new fields of application, such as fibre-based packaging, furniture and light-weight building material. In the work reported in this thesis, three approaches to increasing paper strength were addressed: mixing different pulps, multilayering and reinforcement with man-made fibres. In specific: The effects of mixing Swedish softwood kraft pulp with southern pine or with abaca (Musa Textilis) were investigated. Handsheets of a softwood kraft pulp with the addition of abaca fibres were made in a conventional sheet former. It was seen that the addition of abaca fibres increased the tearing resistance, fracture toughness, folding endurance and air permeance. Tensile strength, tensile stiffness and tensile energy absorption, however, decreased somewhat. Still it was possible to add up to about 60% abaca without any great loss in tensile strength. As an example, with the addition of 30% abaca, the tear index was increased by 36%, while the tensile index was decreased by 8%. To study the effect of stratification, a handsheet former for the production of stratified sheets, the LB Multilayer Handsheet Former was evaluated. The advantage of this sheet former is that it forms a stratified sheet at low consistency giving a good ply bond. It was shown to produce sheets with good formation and the uniformity, evaluated as the variation of paper properties, is retained at a fairly constant level when the number of layers in the stratified sheets is increased. The uniformity of the sheets produced in the LB Multilayer Handsheet Former is generally at the same level as of those produced in conventional sheet formers. The effects of placing southern pine and abaca in separate layers, rather than mixing them homogeneously with softwood pulp were studied. Homogeneous and stratified sheets composed of softwood and southern pine or softwood and abaca were produced in the LB Multilayer Handsheet Former. It was found that by stratifying a sheet, so that a pulp with a high tear index and a pulp with a high tensile index are placed in separate layers, it was possible to increase the tear index by approximately 25%, while the tensile index was decreased by 10-20%. Further, by mixing a pulp with less conformable fibres and no fines with a pulp with more flexible fibres and fines, a synergy in tensile strength (greater strength than that predicted by linear mass fraction additivity) was obtained. The effects of stratifying sheets composed of softwood and abaca were compared to the effects of refining the softwood pulp. Homogeneous and stratified sheets composed of softwood with three different dewatering resistances and abaca were also produced in the LB Multilayer Handsheet Former. It was found that by stratifying the sheets the tear index was retained while the tensile index was increased by the refining. The effects of reinforcing softwood pulp of different dewatering resistances with man-made fibres with low bonding ability were also investigated. Man-made fibres (i.e. regenerated cellulose, polyester and glass fibres) were added in the amounts 1, 3, or 5 wt% to softwood pulp of three different dewatering resistances. It was found that with refining of a softwood pulp and subsequent addition of long fibres with low bonding ability the tensile-tear relationship can be shifted towards higher strength values. The bonding ability of the man-made fibres was evaluated by pull-out tests and the results indicated that, in relation to the fibre strength, regenerated cellulose (lyocell) was most firmly attached to the softwood network while the glass fibres were most loosely attached.

In about 30 years of experiments and development, impulse drying is now considered as a well known technology and a good candidate in the constant effort to save energy in the paper industry. The drying section is indeed the most expensive section in the process of paper production. However, this potential technology has a major disadvantage, stopping its implementation in the industry. Paper, which is a porous material with a variable compressibility, experienced a sudden release of energy at the nip opening during impulse drying. Under these conditions of high intensity process (both in temperature and pressure), the fiber mat has a tendency to delaminate. This web disruption is a critical issue against impulse drying. This thesis comes up with a new approach to the problem. These last years, the technology itself has been addressed in this issue and many improvements have been reached in terms of energy release (heat transfer control, material coating ). The novel idea is then to investigate the inner structure of the paper once it has been coated with starch to a large extent (up to 10 or 20% of the relative basis weight). Starch is known for its large use in industry, but also its capability to expand under high temperature. Hence, both relative strength and bulking effects are investigated in this thesis, using numerous experiments with variable temperatures and pressures, along with ultrasonic testing and image analysis. We have the opportunity to appreciate the phenomenon of heat transfer and mass transport in the coated medium, while reaching promising results in terms of strength and bulk. These are finally investigated using scanning electron microscopy as a first step toward a pore expansion model for starch imbued handsheets.

Almost all research on biorefinery concepts are based on chemical pulping processes and ways of utilising lignin, hemicelluloses and extractives as well as a part of the remaining cellulose for production of nano materials in order to create more valuable products than today. Within the Forest as a Resource (FORE) research program at FSCN we are utilising the whole chain of unit processes from forestry to final products as paper and board, where the pulping process research focus on high yield process as TMP and CTMP. As these process solutions are preserving or only slightly changing the properties of the original wood polymers and extractives, the idea is to find high value adding products designed by nature. From an economic perspective, the production of nanocellulose from a chemical pulp is quite expensive as the pulp has to be either enzymatically (e.g. mono-component endoglucanase) pre-treated or chemically oxidised using the TEMPO (2,2,6,6 - tetramethyl-piperidine-1-oxil) - mediated oxidation method in order to make it possible to disrupt the fibres by means of homogenisation. In high yield pulping processes such as in TMP and CTMP, the idea with this study was to investigate the possibility to use fractions of low quality materials from fines fractions for the production of nano-ligno-cellulose (NLC). The integration of a NLC unit process in a high yield pulping production line has a potential to become a future way to improve the quality level of traditional products such as paper and board grades. The intention of this research work was that, by using this concept, a knowledge base can be created so that it becomes possible to develop a low-cost production method for its implementation. In order to study the potential of this concept, treatment of thermo-mechanical pulp (TMP) fines fractions were studied by means of homogenisation It seems possible to homogenise fine particles of thermo-mechanical pulp (1% w/v) to NLC. A correspond fines fraction from bleached kraft pulp (BKP) was tested as a reference at 0.5% w/v concentration. The objective presented in this work was to develop a methodology for producing mechanical pulp based NLC from fines fractions and to utilise this material as strength additives in paper and board grades. Laboratory sheets of CTMP and BKP, with addition of their respective NLC, were made in a Rapid Köthen sheet former. It was found that handsheets of pulp fibres blended with NLC improved the z-strength and other important mechanical properties for similar sheet densities. The characterisation of the particle size distribution of NLC is both important and challenging and the crill methodology developed at Innventia (former STFI) already during the 1980s was tested to see if it would be both fast and reliable enough. The crill measurement technique is based on the optical responses of a micro/nano particle suspension at two wavelengths of light; UV and IR. The crill value of TMP and CTMP based nano-ligno-cellulose were measured as a function of the homogenisation time. Results showed that the crill value of both TMP-NLC and CTMP-NLC correlated with the homogenisation time.

碩士
國立中興大學
森林學系
88
The main purpose of this study was to make sized paper with good performance of ink color and conservation. Three series of sizing agents (rosin, AKD and Polymaron-360) were applied by internal sizing and dipping process under neutral pH value, respectively. After accelerated aging, optical and physical properties of these sized papers were evaluated to find the best formulation of sizing. The results of internal sized paper showed that the sizing degree was in proportion to the dosage of AKD, which led to slippery paper surface and poor ink color for higher AKD dosage. The proper dosage was around 0.6 to 0.7% of AKD. Alum would have adverse effect on the durability of paper. 0.5% alum with 1.0% rosin size (Hi-pHase and Size pine T) was suggested in preparing the sized papers. Polymaron-360 internal sized paper was good to the folding endurance; the ink color was similar to that of acidic paper. Polymaron-360 could be considered as a good sizing agent, with dosage of 0.5-1.0%, for good aging resistance. The results also showed that the sizing degree of rosin dipping sized paper was unstable and faded out easily. In comparison with two other sizing agents, ink color of Polymaron-360 dipping sized paper was better than that of AKD dipping sized paper. Ink color of AKD dipping sized paper and AKD internal sized paper were almost similar. However, ink color of Polymaron-360 internal sized paper was better than that of Polymaron-360 dipping sized paper. The optimum dipping dosage in stock was 0.01- 0.02% for AKD, and 0.05-0.50% for Polymaron-360. The brightness of dipping sized papers was lower than that of internal sized papers. After accelerated aging, the degree of color reversion of dipping sized papers was greater than that of internal sized papers. Regarding to the pH value and physical strength, dipping sized papers were considered to be better than those of internal sized papers.

碩士
國立屏東科技大學
森林系
91
Using recycled fiber as part of the stuff for papermaking has been a necessity. The application of recycled fiber, however, would affect the final strength properties of the products due to the drying and rewetting of the fibers. Starch, especially cationic starch was thus used to mitigate the defect. The objectives of this study are to evaluate the effect of the cationic starch dosage and the adoption of recycled mixed office waste (MOW) fiber on the retention and handsheet properties in the currently mainstreamed neutral papermaking system. The results showed that the size fastness increased with increasing AKD and cationic starch dosages no matter MOW fibers were added or not. The cationic potato starch showed better size fastness than that of cationic tapioca starch. The size fastness was controlled by AKD and cationic starch dosage, and decreased with increasing charge of MOW pulp. The strength of MOW recycled fiber was improved by an appropriate beating to a CSF of 280ml. The burst and tensile indices of the handsheet were improved with the addition of cationic starch. The strength of handsheet increased with the increasing application of MOW recycled fiber mainly due to its better fiber length distribution than that of the LBKP’s. The overall first pass retention and first pass fines retention were more than 97% and 90% respectively, with the addition of cationic potato starch. The figures were 90% and 70% respectively for the laboratory modified cationic tapioca starch. The first pass retention decreased with increasing cationic starch dosage, due to over cationic demand. The specific charge density of the stock changed sensitively with the addition of potato starch. The ultimate potential of the stock reached to a near isoelectric point after all the designed additives were applied, showing that the sequence of addition is applicable in the neutral papermaking system.

碩士
大葉大學
環境工程學系碩士班
100
In order for printing and writing papers to comply with the function of communication, there are certain requirements on the optical properties of the grade. At present, many mills engage the use of mineral pigments as fillers to papermaking stocks to improve optical properties of the resulting paper. Filler addition constitutes a part of production cost, however. Whether by physical means the floc structures of the stock can be altered and lead to better optical properties is a topic worthy of investigation. 　　In this study, the basic stock preparation flow was followed with different pulp consistencies, and different combinations of filler proportions subjected to varying stirring rates and stirring time so as to modify the degrees of flocculation of fibers and fillers. The stocks were then formed into handsheets with the premise that shear force might alter the chance of fibers binding to fillers and thus increase strength and produce better optical properties for the resulting handsheets. 　　The results indicated that paper physical properties, such as burst index and tensile index were increased when stronger shear stresses were applied to the stock during floc formation. Ash retentions tended to increase with stronger stirring intensity and stirring time. As for filler combinations, when a portion of calcium carbonate was substituted by platy minerals such as sericite or talc, the resulting handsheets showed an increase in strength properties at the cost of slight decrease in the optical properties. Scanning microscopy observations showed that upon forming flocs, filler particles attach themselves often to the interstices of fiber binding sites and on the surface of fibers, forming platy aggregates, the reduction of fillers at the inter-fiber bonding areas thus might contribute to better inter-fiber bonding and enhanced physical properties of the resulting papers.