The influence of nanofibrillated cellulose on mechanical and printing properties of packaging paper

Papirji in kartoni, namenjeni embaliranju, morajo dosegati čim boljše mehanske lastnosti ob čim nižji masi oz. gramaturi, hkrati pa morajo imeti tudi primerne površinske lastnosti za tiskanje v različnih tiskarskih tehnikah. Za doseganje teh lastnosti se jim vse pogosteje dodaja nanoceluloza. Nanoceluloza je sodoben, naravni nanomaterial z izjemnimi mehanskimi lastnostmi, ki se ga lahko pridobiva s kemijskimi, z mehanskimi ali z biološkimi postopki oz. s kombinacijo le-teh. Glede na način pridobivanja, dimenzije in druge lastnosti, se nanoceluloza loči na: nanofibrilirano celulozo (NFC), nanokristalinično celulozo (NCC) in bakterijsko nanocelulozo (BNC). V raziskavi je bil preučen vpliv dodatkov NFC in BNC, pridobljenih iz alternativnih surovinskih virov, na osnovne, mehanske, površinske, optične in tiskarske lastnosti embalažnega papirja, ki bi se lahko uporabljal kot t. i. nepremazan, beljen kraft liner. V raziskavi je bila nanofibrilirana celuloza pridobljena iz japonskega dresnika, ki je ena izmed najbolj invazivnih tujerodnih rastlin pri nas. Poleg nanofibrilirane celuloze je bila iz stranskega produkta, ki nastaja pri klasičnem postopku pridobivanja kisa, pridobljena tudi bakterijska nanoceluloza. Z namenom določitve vpliva dodatka različnih nanoceluloz na lastnosti papirja so bili iz beljenih, sulfatnih, evkaliptusovih celuloznih vlaken z dodanim kationskim škrobom in 10 oz. 20 % NFC ali BNC oblikovani laboratorijski listi. Analiza osnovnih, mehanskih, površinskih in tiskarskih lastnosti je pokazala, da dodatek obeh vrst nanoceluloze pozitivno vpliva na večino izmerjenih lastnosti papirja. Posledično sledi zaključek, da je tovrstna nanoceluloza primerna za uporabo v papirništvu, kljub temu, da je bila proizvedena iz alternativnih surovinskih virov.Paper and board for packaging must have as good mechanical properties as possible at the minimum possible weight or grammage. At the same time, they must achieve suitable surface properties for printing with different printing techniques. To achieve these properties, nanocellulose often added to them. Nanocellulose is a modern, naturally based nanomaterial, with exceptional mechanical properties. It can be obtained with chemical or mechanical procedures, with the use of appropriate microorganisms or with a combination of these approaches. Depending on the method of production, dimensions and other properties, nanocellulose can be classified as nanofibrilated cellulose (NFC), nanocrystalline cellulose (NCC), and bacterial nanocellulose (BNC). The purpose of our research was to determine the impact of two different types of nanocellulose, obtained from alternative raw materials, on basic, mechanical, surface, optical and printing properties of packaging paper, potentially used as uncoated, bleached kraft liner. In the research, nanofibrilated cellulose was obtained from Japanese knotweed, which is one of the most invasive plants in Europe. Beside nanofibrillated cellulose, BNC was obtained from a by-product formed during the classical vinegar production. To determine the effect of nanocellulose addition on paper properties, laboratory sheets were formed of kraft, bleached, eucalyptus cellulose fibers, with cationic starch and 10% or 20% of NFC or BNC added. Analyses of basic, mechanical, surface and printing properties have shown that the addition of both types of nanocellulose had a positive effect on most of the measured paper properties. Based on the results of the research it can be concluded, that both obtained nanocelluloses are suitable for use in papermaking, despite the fact that they have been produced from alternative raw materials