Nanoparticles from alder and pine trees bark and their application in enhancing paper strength and barrier properties | Nanodaļiņu iegūšana no alkšņa un priedes koka mizām un to izmantošana papīra izturības un barjerīpašību uzlabošanai

Inglés. In the present work, nanoparticles were obtained from alder and pine bark and then used in the paper furnish and coatings. Extracted bark was obtained in the first stage of biorefinery chain when polyphenols have been isolated. Both extracted and unextracted bark was applied as raw material for production of nanoparticles. Bark was destructed by thermocatalytic process developed at the Institute. According to this method the bark was impregnated with a weak hydrochloric acid and thermally treated at 1200 C until a dry state. Then the partially destructed bark was dispersed in water medium in a ball mill. Gel-like dispersions were obtained which contained nanoparticles with dimensions around 300 nm. It was found that with increasing bark nanoparticles content paper handsheet tensile and burst index enlarged (Figure). At the filler content 20% in the case of non-extracted and extracted grey alder bark, tensile index increased by 28 and 44% and burst index by 78 and 91%, respectively. The smaller effect of the nanoparticle filler obtained from non-extracted bark can be explained by the fact that the extractives hinder the hydrogen bond formation between cellulose fibres and the nanoparticles. These results show that it is possible to replace the rather expensive pulp fibres by tree bark particles. From practical point of view it is important that the addition of bark nanoparticles also to the waste paper furnish boost the strength indices. It was demonstrated that 20% charge of the particles from grey and black alder improved the paper tensile index by 10 to 20% and the burs index by 15 to 25%. Also in these experiments the extracted bark nanoparticles were more efficient. In further experiments the paper produced by Ligatne Paper Mill was used to examine the possibilities to improve its barrier properties. It was established that 100 µm thin paper coatings made from black alder bark nanoparticles lead to the decrease of air permeability from 9 to 15 Gurley seconds. When using chitosan as the adhesive for bark nanoparticles the efficiency of the coatings was achieved to a much greater extent. In this case also paper strength properties were improved considerably

Letón. Pētījuma mērķis bija izstrādāt nanodaļiņu termokatalītisko iegūšanas metodi no kokrūpniecības atlikumiem  – galvenokārt mizām – un izmantot šīs nanodaļiņas papīra izturības un barjerīpašību uzlabošanai, pie tam aizvietojot dārgākās celulozes šķiedras. Nanodaļiņas ir izmantotas divējādi, iejaucot tās papīru veidojošo šķiedru suspensijā vai arī veidojot uz papīra virsmas 100 µm plānus pārklājumus. Rezultātā iegūti modificēti papīra paraugi, kas saturēja līdz 20% nanodaļiņu. Konstatēts, ka mizas nanodaļiņas veicina papīra izturības paaugstināšanu līdz pat 1,5 reizēm. Iepriekš biorafinērijā ekstraģētās mizas uzrādīja relatīvi labākus rezultātus. Mizas daļiņu izmantošana visperspektīvākā var būt krāsainajiem papīriem un papīriem no reciklētajām šķiedrām (makulatūras). Savukārt mizas nanodaļiņu pārklājumi ievērojami uzlabo nekrītota papīra barjerīpašības attiecībā uz gaisa caurlaidību. Vienlaicīgi var panākt papīra mehānisko īpašību paaugstināšanu, ja papildus kā adhēzijas veicinātāju izmanto hitozānu.