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Method Development for Producing Napkins and Femcare Absorbent Cores by Using an Airlaid Former

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Method Development for Producing Napkins and Femcare Absorbent Cores by Using an Airlaid Former DEGREE PROJECT IN CHEMICAL SCIENCE AND ENGINEERING, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2020 Method development for producing napkins and femcare absorbent cores by using an airlaid former LINNEA KILEGRAN KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES IN CHEMISTRY, BIOTECHNOLOGY AND HEALTH Abstract Fluff pulp is a renewable material consisting of pure cellulose fibers which are obtained during pulping. These fibers are commonly used to form Airlaid-nonwoven products such as napkins and wipes. Fluff pulp is also used in absorbent cores in femcare products, incontinence products and diapers. Some of these absorbent core structures (especially in ultrathin pads) are produced through airlaid. Airlaid is a manufacturing technique which forms a randomly oriented fiber structure by using an applied suction. This degree project aimed at developing methods for producing napkins and femcare absorbent cores on a laboratory scale by using an airlaid former. Important properties such as grammage, thickness, density, bending length and liquid spreading were therefore measured on commercial napkins and femcare absorbent cores. Other analyses which were performed include tensile testing and SEM. Findings from these analyses were then used as a target reference during the method development. Two methods were developed; one for producing a napkin structure and one for producing a femcare absorbent core structure. The different manufacturing steps included fiber defiberization, sample formation, pressing, embossing, latex spraying and curing. Napkin structures and femcare absorbent core structures were produced by using the developed methods, and their properties were analyzed and compared with the commercial products. Analysis showed that the developed methods generated structures with grammages that corresponded well with the grammages in the commercial products. However, both developed structures were thicker and had lower density than the commercial products. This decreased density probably influenced the results in other analyses performed in this project. The developed napkin structure had a shorter bending length compared to the commercial napkins and the developed femcare structure had a better absorption capacity compared to the commercial femcare absorbent cores. Both developed structures obtained nice surface finish which corresponded well with the surface finish in the commercial products. However, SEM analysis indicated that no latex managed to reach the center in the developed structures. Keywords: Fluff pulp, nonwoven, airlaid, thermofiber, superabsorbent polymer, absorbent core, napkin, femcare i Sammanfattning Fluffmassa är ett förnybart material bestående av cellulosafiber som utvinns under massakokning. Dessa fiber används för att tillverka olika absorberande produkter som till exempel servetter. Fluffmassa används även för att tillverka absorptionskärnor i damhygienprodukter, inkontinensprodukter och blöjor. Vissa av dessa absorptionskärnor (speciellt i ultratunna bindor) tillverkas med airlaid. Airlaid är en tillverkingsteknik som ger fiberstrukturer med slumpmässig orientering genom att applicera ett undertryck. Syftet med detta examensarbete var att utveckla metoder för att tillverka servetter och absorptionskärnor till damhygienprodukter i laboratoriemiljö genom att använda en airlaid maskin i laboratorieskala. Detta utfördes genom att analysera viktiga egenskaper som exempelvis ytvikt, tjocklek, densitet, böjlängd och förmågan att absorbera vätska i kommersiella servetter och absorptionskärnor inom damhygien. Även dragprov och SEM- analys utfördes. Resultatet från dessa analyser användes som ett riktvärde under metodutvecklingen. Två metoder utvecklades - en för att tillverka en servettstruktur och en för att tillverka en absorptionskärna för damhygien. De olika tillverkningsstegen inkluderar defibrering, formering, pressning, prägling, latexsprayning samt härdning. Båda strukturerna tillverkades, och dess egenskaper analyserades och jämfördes med de kommersiella produkterna. Analyserna visade att de utvecklade metoderna genererade struktuer vars ytvikt stämde väl överrens med de kommersialla produkterna. Strukturerna var dock tjockare och hade en lägre densitet än de kommmersiella produkterna. Den minskade densiteten påverkade förmodligen resultatet från de andra analyserna som utfördes i detta projekt. Servettstrukturen hade en lägre böjlängd än de kommersiella servetterna och damhygienstrukturen hade bättre absorption än de kommersiella produkterna. Båda strukturerna hade en ytfinish som överensstämmde väl med de kommersiella produkterna. Dock visade SEM-analysen att latex saknades i mitten av de båda tillverkade strukturerna. Nyckelord: Fuffmassa, nonwoven, airlaid, termofiber, superabsorbent, absorptionskärna, servett, damhygien ii Table of Content Abstract ...............................................................................................................................................i Sammanfattning ................................................................................................................................. ii List of abbreviations ............................................................................................................................ v 1. Introduction ....................................................................................................................................1 1.1 Aim ...........................................................................................................................................1 1.2 Objectives .................................................................................................................................1 2. Background .....................................................................................................................................2 2.1 Nonwoven.................................................................................................................................2 2.2 Airlaid .......................................................................................................................................2 2.2.1 Fluff pulp defiberizing .........................................................................................................3 2.2.2 Web formation ...................................................................................................................3 2.2.3 Web bonding ......................................................................................................................3 2.3 Fluff pulp ...................................................................................................................................4 2.4 Bicomponent fibers/thermofiber ...............................................................................................5 2.5 Superabsorbent polymer (SAP) ..................................................................................................6 2.6 Absorbent hygiene products and their layers.............................................................................7 2.6.1 Top layer ............................................................................................................................8 2.6.2 Acquisition and distribution layer .......................................................................................8 2.6.3 Absorbent core ...................................................................................................................8 2.6.4 Back sheet ..........................................................................................................................8 2.7 Airlaid napkin structure .............................................................................................................8 3. Experimental part ...........................................................................................................................9 3.1 Materials ...................................................................................................................................9 3.2 Selection of commercial products for analysis ......................................................................... 10 3.3 Analysis ................................................................................................................................... 10 3.3.1 Grammage ....................................................................................................................... 10 3.3.2 Thickness and density ....................................................................................................... 10 3.3.3 Bending length ................................................................................................................. 11 3.3.4 Liquid spread and absorption capacity .............................................................................. 11 3.3.5 Scanning Electron Microscope (SEM) ................................................................................ 11 3.3.6 Tensile testing .................................................................................................................. 12 3.4 Method development for producing airlaid structures ............................................................ 12 4. Results and discussion ................................................................................................................... 13 4.1 Selected commercial products................................................................................................
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