No description available.

Tissue, among the highest value added paper products, finds extensive application in modern society. Continued efforts are being made to further improve tissue properties, such as strength, softness and water absorbency. Besides the efforts on characterizing facial tissue softness, this study focuses on tissue quality improvement through chemical means. The application of a wet strength resin, Kymene1500 and a debonding agent, Softrite7516 onto cellulose fibers is considered. First, the adsorption kinetics of the two chemical additives onto cellulose fibers was studied. The adsorption mechanisms were proposed and validated by kinetic data. A novel apparatus was designed in this study, and represented the first in the field to collect real-time data, which has the potential to be applied to the adsorption kinetic study of other types of paper additives. Second, the effects of Kymene1500 and Softrite7516 on various sheet properties were studied. The results provide quantitative information on tissue additives effects on sheet properties. It is shown that the combined application of the additives can overcome the disadvantages of individual species and produce sheets with both wet strength and softness. Finally, environmental-benign debonding agents with polyoxyethylene chains were applied to the sheets, and the effects of two design parameters, i.e., fatty acid and degree of ethoxylation, on tissue properties were investigated.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Patterson, Timothy; Committee Member: Aidun, Cyrus; Committee Member: Banerjee, Sujit

Cotton as a dominating natural fibre imparts a major contribution in the whole textile market including natural and artificial fibres. The demand of this cellulosic fibre is increasing rapidly day by day, on the other hand supply cannot fulfill its demand, and as a result price goes higher in world market. Now people are looking for alternatives to cotton in different applications. Viscose as cellulosic origin, the cheapest of all cellulosic fibres could be the best alternative. Viscose fibre exhibits some similar properties compared to cotton except its poor wet strength. In this thesis work different chemical finishes were applied to improve the wet strength of viscose fabric. For this purpose water repellent and soil release finishes were applied. Both water repellent and soil release finishes helped in reducing the molecular barrier around the individual fibres that lowered the surface tension of the fibre. It reduces the absorbency of viscose fibre hence leads to higher wet strength. Water repellent finish was applied alone as well as in combination with soil release finish. It was seen that viscose fibre exhibited better wet strength after applying water repellent and soil release finishes on it. This improved property of viscose could replace the cotton fibre in certain applications like bed linen. / Program: Magisterutbildning i textilteknologi

Wet web paper cohesive properties behave in a similar way than tensile strength properties. The result was obtained using an unique apparatus developed by the IPST, which allows the cohesive strength determination for different wet web solids content. With the results a linear relation can be established between the cohesive strength index (obtained with the splitting apparatus) and the tensile strength index (obtained with the Instron). The splitting apparatus results can be used to calculate strain based on the work of Osterberg.

Abstract High Yield Pulp (HYP), i.e. TMP, SGW or CTMP, is normally used in printing papers (News, SC and LWC) or in a middle layer on cardboard i.e. in products that either have high demands on printability and runnability in fast printing presses or contribute to high bulk in cardboards in order to minimize pulp consumption at a certain sheet stiffness. Tensile strength as a function of density is significantly higher for HYP compared to chemical pulps such as sulphate and sulphite pulps. However, chemical pulp is mainly used in packaging materials that require very high tensile strength, while at the same time allowing the density of the paper to be high. By utilizing the softening properties of high-yielding lignin-rich fibres by hot-pressing technology, it is possible to significantly increase sheet density and thereby strength closer to the level of chemical pulps. Furthermore, due to the presence of high levels of lignin, it was shown that considerably higher wet strength can be achieved compared to chemical pulp without the addition of strengthening agents. The study focuses on the softening of stiff and lignin-rich fibres in papers based on HYP with sufficiently high moisture contents, when hot-pressing at temperature levels significantly above the softening temperature (Tg) of lignin Hot-pressing increases the density of the sheet which increases the contact surface between the fibres in the paper structure. The high pressing temperature can be said to induce a viscous flow of lignin, which also increases the potential for fibre-fibre bonding. It is conceivable that covalent bonds are obtained via condensation reactions and partly that interdiffusion between the lignin in the fibre walls can be obtained as they come close enough to each other during the hot-pressing. The research also shows that hot-pressing greatly improves properties in the form of dry and wet strength as well as hydrophobicity for HYP and for lignin-rich kraft paper. The first part of the study shows the effect of hot-pressing on strength properties of paper sheets based on CTMP, HT-CTMP, TMP, NSSC, SCPal and NBSK. The second part includes a study on how and to what extent different amounts of residual lignin in the pulp contribute to the dry and wet strength of the sheets of paper during hot-pressing as a function of increasing temperature. To demonstrate this, pilot scale cooking of unbleached pulp to various lignin levels was carried out. In all experiments in parts one and two, laboratory sheets with a surface weight of 150 g/m2 and a dry content of 50% were made with a Rapid Köthen (RK) sheet former, after which the sheets were hot-pressed in a cylinder press at temperatures up to 200°C, constant high pressure of about 7 MPa, nip pressure dwell time of 1.5 sec and production speed 1 m/min. The third part includes a study on the optimization of variables in a new design of a dynamic cylinder press for hot-pressing technology. This design is based on previous research at Mid Sweden University combined with key knowledge of steel band technology within IPCO AB. The new pilot machine is based on heating of a steel belt with infrared heat (IR) up to 300°C, a maximum line load of 15 kN/m in two press nips and a dwell time of 23-240 ms in the nip depending on the production speed which is up to 5 m/min. The experiments in part three were based on RK paper sheets with 100 g/m2 and approximately 63% dry content made by HT-CTMP. The results confirm that hot-pressed HYP-based paper sheets enable permanent densification by softening lignin, which provides a very high dry tensile strength and a remarkable improvement in wet tensile strength compared to bleached kraft pulp without the need for wet strength agents. A tensile index of 75 kNm/kg, compression strength index (SCT) of 45 kNm/kg and wet tensile strength index of 16 kNm/kg were obtained, which can be compared with the corresponding values for bleached kraft pulp based paper sheets of 85 kNm/kg, 35 kNm/kg and 5 kNm/kg respectively, all with the same density after hot-pressing at 200°C. The NSSC reached the highest tensile strength index of 92 kNm/kg. The study with the unbleached kraft pulps showed that the lignin content had a significant effect on both the dry and wet tensile strength indices. The pulps showed a linear relationship between wet strength and lignin content. The increase in lignin content from 0% to 12% improved the dry tensile index by 20% and SCT by 35% and gave a very significant increase in the wet strength index from 3 to 23 kNm/kg after hot-pressing. All lignin-rich paper samples exhibit good wet stability for at least 24 hours and an improved surface hydrophobicity by increasing the pressing temperature and lignin content. Optimization of the new steel belt based press machine showed that high nip pressure and two press nips had a great effect on density and strength. Whereas high temperature, well above Tg of lignin, and long pressing time were more important to achieve high wet strength. The highest wet strength index value, 27 kNm/kg, was reached when the pressing temperature was 290°C, the nip pressure about 8 MPa, the pressing time in the press nip 40 ms and the dwell time in contact with the steel belt 23.5 sec. It was also noted that no delamination occurred in these tests. In order to obtain both high dry and wet strength, it is important to have high lignin content, high temperature, high nip pressure and sufficiently long pressing time / Sammanfattning Högutbytesmassa (HYP), d.v.s. SGW, TMP eller CTMP, används normalt i tryckpapper (News, SC och LWC) eller i mittskikt i kartong dvs i produkter som har höga krav på tryckbarhet och körbarhet i snabba tryckpressar eller för att bidra till hög bulk i kartong så att man därmed kan minimera förbrukningen av massa för att nå en viss arkstyvhet. Dragstyrka som funktion av densitet är väsentligt högre för HYP jämfört med kemiska massor som sulfat- och sulfitmassor. Däremot används främst kemiska massor i förpackningsmaterial som kräver mycket hög dragstryka, där man samtidigt tillåter att papperets densitet får vara hög. Genom att utnyttja mjukningsegenskaperna hos högutbytesmassors ligninrika fibrer genom varmpressningsteknik kan man väsentligt öka arkdensitet och därigenom styrka till i nivå med kemiska massors. Vidare visas att man tack vara närvaro av höga halter lignin kan nå väsentligt högre våtstyrka jämfört med kemisk massa utan tillsats av styrkehöjande kemikalier. Studien fokuserar på mjukgörning av styva och ligninrika fibrer vid varmpressning vid temperaturnivåer väsentligt över mjukningstemperaturen (Tg) för lignin av HYP-baserat papper med tillräckligt hög fukthalt. Varmpressning ökar arkens densitet, vilket ökar kontaktytan mellan fibrerna i pappersstrukturen. Den höga pressnings-temperaturen kan sägas inducera ett visköst flöde av lignin, vilket då ökar möjligheten att få starkare för fiber-fiber-bindning. Man kan dels tänka sig att kovalenta bindningar erhålls via kondensationsreaktioner och dels att man kan erhålla interdiffusion mellan ligninet i fiberväggarna då de kommer tillräckligt nära varandra vid varmpressningen. Forskningen visar också att varmpressning högst väsentligt förbättrar egenskaper i form av torr- och våtstyrka samt hydrofobicitet för både HYP-baserat och ligninrikt kraftpapper. Den första delen av studien visar effekten av varmpressning på styrke-egenskaper hos pappersark baserade på CTMP, HT-CTMP, TMP, NSSC, SCPal och NBSK. Den andra delen inkluderar en studie om hur och i vilken utsträckning olika mängder av kvarvarande lignin i massa bidrar till pappersarkens torrstyrka och våtstyrka vid varmpressning som funktion av ökande temperatur. För att demonstrera detta tillverkades oblekt kraftmassa till olika ligninhalter i pilotskala. I alla experiment i del ett och två i avhandlingen tillverkades laboratorieark med ytvikten 150 g/m2 och torrhalten 50% i en Rapid Köthen (RK) arkformare varefter arken varmpressades i en cylinderpress vid temperaturer upp till 200°C och konstant högt tryck på cirka 7 MPa i ett pressnyp med uppehållstiden 1,5 s i pressnypet  vid maskinhastigheten 1 m/min. Den tredje delen i avhandlingen inkluderar en studie om optimering av variabler i en ny design av en dynamisk cylinderpress för varmpressteknik. Den nya designen baseras på tidigare forskning vid Mittuniversitetet kombinerat med nyckelkunskap om stålbandstekniker inom IPCO AB. Den nya pilotmaskinen är baserad på att ett stålbälte uppvärms med infraröd värme (IR) upp till 300°C, en linjelast upp till 15 kN/m i två pressnyp vardera, med variabel presstid 23-240 ms i pressnypet beroende av maskinhastigheter upp till 5 m/min. Experimenten i del tre i avhandlingen baserades på RK-pappersark tillverkade av HT-CTMP med ytvikten 100 g/m2 och torrhalten ca 63%. Resultaten bekräftar att varmpressande HYP-baserade pappersark möjliggör permanent densifiering genom mjukning av lignin, vilket ger en mycket hög torr dragstyrka och en anmärkningsvärd förbättring av våt dragstyrka jämfört med blekt kraftmassa utan att våtstyrkemedel behöver användas. Ett dragindex på 75 kNm/kg, kompressionsstyrkeindex (SCT) på 45 kNm/kg och våtstyrkeindex på 16 kNm/kg erhölls vilket kan jämföras med motsvarande värden för pappersarken från blekt kraftmassa på 85 kNm/kg, 35 kNm/kg respektive 5 kNm/kg, alla med samma densitet efter varmpressning vid 200°C. Lövvedsbaserad NSSC nådde det högsta dragstyrkeindexet på hela 92 kNm/kg. Studien med de oblekta kraftmassorna visade att lignininnehållet hade en signifikant effekt på både torr- och våtstyrkeindex. Kraftmassorna uppvisade ett linjärt samband mellan våtstyrka och lignininnehåll. Ökningen i ligninhalten från 0% till 12% förbättrade dragindexet med 20% och SCT med 35% och gav en mycket signifikant ökning i våtstyrkeindex från 3 till 23 kNm/kg efter varmpressningen. Alla ligninrika pappersprover uppvisar god våtstyrkestabilitet under minst 24 timmar och en förbättrad ythydrofobicitet genom ökning av presstrycktemperaturen och lignininnehållet. Optimering av den nya stålbandsbaserade cylinderpressen visade att högt pressnyptryck och två pressnyp hade stor effekt på densitet och styrka. Emedan hög temperatur, långt över Tg för lignin, och lång presstid var viktigare för att nå hög våtstyrka. Det högsta värdet på våtstyrkeindex, 27 kNm/kg, uppnåddes när presstemperaturen var 290°C, pressnyptrycket cirka 8 MPa, presstiden i pressnypet 40 ms och tiden i kontakt med stålbältet 23,5 sek. Det noterades också att ingen delaminering inträffade i dessa tester. För att erhålla både hög torr- och våtstyrka är det viktigt med högt lignininnehåll, hög temperatur, högt nyptryck och tillräckligt lång presstid. / <p>Vid tidpunkten för framläggningen av avhandlingen var följande delarbeten opublicerade: delarbete 1 (accepterat), delarbete 2 (inskickat), delarbete 3 (manuskript).</p><p>At the time of the defence the following papers were unpublished: paper 1 (accepted), paper 2 (submitted), paper 3 (manuscript).</p>

<p>A systematic investigation of Polyvinylamine (PVAm) as a strength-enhancing polymer for wet paper was undertaken through the development of a new test method that simulates the influence of polymers on fibre-fibre bonding in paper. Pairs of wet regenerated cellulose membranes were laminated using the paper strength-enhancing polymer as the lamination adhesive. The resulting laminates served as a physical model for fibre-fibre bonds in paper and the wet laminate strength was determined by ninety degree peeling experiments. Key experimental parameters and sources of error were identified.</p> <p>The mechanism of PVAm paper wet strength enhancement was explored by the wet cellulose delamination procedure. Initial results showed that PVAm was a poor wet adhesive for cellulose unless the cellulose was lightly oxidized. The adhesion was found to be a strong function of the concentration of amine and of the cellulose oxidation products. This led to the hypothesis that there are two mechanism in action; the first being the well-accepted electrostatic bonding theories and the second being covalent bond formation between acetal/hemi-acetals/aldehydes and the amine.</p> <p>A thorough investigation of the surface chemistry and morphology was conducted to confirm the hypothesis of covalent bond formation between aldehydes and amines. Oxidized regenerated cellulose was laminated with PVAm and the peeled surfaces analyzed by X-ray Photoelectron Spectroscopy (XPS). It was shown that the wet delamination force correlated to the acetal/hemi-acetal/alehyde surface concentration. It was concluded that the delamination force would be increased by a cumulative strengthening of both the cellulose surface and adhesive interface.</p> / Doctor of Philosophy (PhD)

No description available.

Polyamideamine epichlorohydrin (PAE) resin is a water soluble additive and the most used permanent wet strength additive in alkaline conditions for preparing wet strengthened papers. In this thesis, we studied some properties of PAE resins and wet strengthened papers prepared from them. In order to elucidate PAE structure, liquid state, 1H and 13C NMR was performed and permitted signals assignment of PAE structure. PAE films were prepared to study cross-linking reactions and then thermal and ageing treatments were performed. According to our results, the main PAE cross-linking reaction occurs by a nucleophilic attack of N atoms in the PAE and/or polyamideamine structures forming 2-propanol bridges between PAE macromolecules. A secondary contribution of ester linkages to the PAE cross-linking was also observed. However, this reaction, which is thermally induced, only occurs under anhydrous conditions. The mechanism related to wet strength development of PAE-based papers was studied by using CMC as a model compound for cellulosic fibres and PAE-CMC interactions as a model for PAE-fibres interactions. Based on results from NMR and FTIR, we clearly showed that PAE react with CMC that is when carboxylic groups are present in great amounts. Consequently, as the number of carboxylic groups present in lignocellulosic fibres is considerably less important and the resulting formed ester bonds are hydrolysable, we postulate that ester bond formation has a negligible impact on the wet strength of PAE-based papers. In the second part of this work, a 100% Eucalyptus pulp suspension was used to prepare PAE-based papers. PAE was added at different dosages (0.4, 0.6 and 1%) into the pulp suspension and its adsorption was indirectly followed by measuring the zeta potential. Results indicate that the adsorption, reconformation and/or penetration phenomena reach an apparent equilibrium between 10 and 30 min. Moreover, we showed that the paper dry strength was not significantly affected by the conductivity level (from 100 to 3000 µS/cm) of the pulp suspension. However, the conductivity has an impact on the wet strength and this effect seems to be enhanced for the highest PAE dosage (1%). We also demonstrated that storing the treated paper under controlled conditions or boosting the PAE cross-linking with a thermal post-treatment does not necessarily lead to the same wet strength. Degrading studies of cross-linked PAE films showed that PAE degradation in a persulfate solution at alkaline medium was more effective. A preliminary study of industrial PAE-based papers (coated and uncoated papers) was also performed. For uncoated paper, persulfate treatment was the most efficient. For coated papers, all treatments were inefficient in the used conditions, although a decrease of the wet tensile force of degraded samples was observed. The main responsible of the decrease of persulfate efficiency for coated papers was probably related to side reactions of free radicals with the coating constituents.

Le travail présenté dans ce manuscrit s’intéresse au mode d’action des résines thermodurcissables utilisées pour conférer au matériau papier des propriétés spécifiques. En effet, certains papiers sont destinés, au cours de leur usage, à être en contact avec des liquides et en particulier de l’eau. C’est le cas, par exemple, des papiers absorbants, de certains papiers filtres, mais aussi de papiers pour étiquettes ou pour billets de banque. En présence d’eau, les papiers perdent rapidement leur résistance mécanique, essentiellement due à la présence en grand nombre de liaisons hydrogène, d’où la nécessité d’un traitement : l’objectif est de maintenir un certain niveau de résistance des papiers saturés en eau. Ces traitements consistent à introduire dans la suspension fibreuse, en cours d’élaboration, des pré-polymères cationiques s’adsorbant à la surface des fibres. Après la formation de la feuille de papier, la feuille humide est séchée et c’est au cours de cette étape que s’amorce la réticulation de ces polymères. Elle conduit à la formation d’un réseau tridimensionnel de polymère dans le matelas fibreux. Ce réseau permet au papier de conserver ses propriétés mécaniques lorsqu’il est en contact avec de l’eau. Il présente ce que l’on appelle communément une résistance à l’état humide (REH). Un des inconvénients de ce type de traitement est lié aux difficultés de recyclage des papiers obtenus. Il nécessite un traitement particulièrement intensif et coûteux qui couple une action mécanique (désintégration, dépastillage) à une action chimique (utilisation d’hydroxyde de sodium, par exemple). Même si ces produits sont largement utilisés, les mécanismes mis en jeu que ce soit pour le développement des propriétés de REH ou pour le recyclage ne sont pas totalement compris. Dans ce contexte, ce travail a pour objectif d’étudier le mode d’action de pré-polymères de polyamideamine épichlorhydrine (PAE), couramment utilisés en papeterie pour conférer au matériau papier une résistance à l’état humide (REH). Il s’intéresse à la caractérisation de solutions commerciales de PAE et à l’étude des mécanismes réactionnels de ces pré-polymères. Il traite également de l’effet de certains paramètres de production du papier sur l’efficacité des traitements. Enfin, il apporte de éléments nouveaux sur la compréhension de l’étape de recyclage. / Polyamideamine epichlorohydrin (PAE) resin is a water soluble additive and the most used permanent wet strength additive in alkaline conditions for preparing wet strengthened papers. In this thesis, we studied some properties of PAE resins and wet strengthened papers prepared from them. In order to elucidate PAE structure, liquid state, 1H and 13C NMR was performed and permitted signals assignment of PAE structure. PAE films were prepared to study cross-linking reactions and then thermal and ageing treatments were performed. According to our results, the main PAE cross-linking reaction occurs by a nucleophilic attack of N atoms in the PAE and/or polyamideamine structures forming 2-propanol bridges between PAE macromolecules. A secondary contribution of ester linkages to the PAE cross-linking was also observed. However, this reaction, which is thermally induced, only occurs under anhydrous conditions. The mechanism related to wet strength development of PAE-based papers was studied by using CMC as a model compound for cellulosic fibres and PAE-CMC interactions as a model for PAE-fibres interactions. Based on results from NMR and FTIR, we clearly showed that PAE react with CMC that is when carboxylic groups are present in great amounts. Consequently, as the number of carboxylic groups present in lignocellulosic fibres is considerably less important and the resulting formed ester bonds are hydrolysable, we postulate that ester bond formation has a negligible impact on the wet strength of PAE-based papers. In the second part of this work, a 100% Eucalyptus pulp suspension was used to prepare PAE-based papers. PAE was added at different dosages (0.4, 0.6 and 1%) into the pulp suspension and its adsorption was indirectly followed by measuring the zeta potential. Results indicate that the adsorption, reconformation and/or penetration phenomena reach an apparent equilibrium between 10 and 30 min. Moreover, we showed that the paper dry strength was not significantly affected by the conductivity level (from 100 to 3000 µS/cm) of the pulp suspension. However, the conductivity has an impact on the wet strength and this effect seems to be enhanced for the highest PAE dosage (1%). We also demonstrated that storing the treated paper under controlled conditions or boosting the PAE cross-linking with a thermal post-treatment does not necessarily lead to the same wet strength. Degrading studies of cross-linked PAE films showed that PAE degradation in a persulfate solution at alkaline medium was more effective. A preliminary study of industrial PAE-based papers (coated and uncoated papers) was also performed. For uncoated paper, persulfate treatment was the most efficient. For coated papers, all treatments were inefficient in the used conditions, although a decrease of the wet tensile force of degraded samples was observed. The main responsible of the decrease of persulfate efficiency for coated papers was probably related to side reactions of free radicals with the coating constituents.