Introduction

The work was carried out in order to continue our study1 aimed at the development of interface additives on the basis of lignin, which is produced as a multi-tonnage waste under various processings of plant raw materials. During cellulose manufacture by sulphite pulping, lignin component of plant tissue is transformed and water-soluble sulphonated lignin, so-called

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lignosulphonates (LS) passes into cooking solution. Non-controlled discharging of LS into aquatic system creates serious environmental problems. Due to surface active properties, the LS-based products have wide application as dispersants, stabilizers, adhesives, etc.2-4 However, only 5% from total LS production are used as commercial products, the rest has not found yet other application besides burning.5 LS macromolecule is negatively charged, carries sulphonate, phenolic, aliphatic hydroxyl and carboxyl functional groups (Figure 1) and shows polyelectrolyte behaviour.6

Figure 1. Schematic presentation of lignosulphonate molecule chemical structure [6].

In the last decades lignins, in particular in mixtures with conventional adhesives and flocculants and complexes with cationic polymers are considered as special additives for improvement of operating characteristics of paper and cardboard.7-9 In order to enhance the paper strength, polyelectrolyte complexes of cationic and anionic naturally originated and synthetic polymers are proposed, e.g. carboxymethyl cellulose combined with cationic polyamideamine epichlorohydrin condensate provided a significant increase in strength of the paper, compared to sheets prepared with only the cationic condensate.10 Building of polyelectrolyte multilayers on the fibre surface, when consecutive layers of cationic and anionic polymers are deposited on cellulosic fibres is a developing trend.11 The use of sulphonated kraft lignin/ PEO complexes as a dual retention system for newsprint and groundwood stocks was suggested in,12 where it was showed that the complexes improved fines retention without decreasing pulp brightness.

The present work is focused on the main features of LS adsorption onto various solid components of paper composite materials (cellulose, kaolin, calcium carbonate, titanium dioxide) and is aimed at purposeful alteration of the LS efficiency as auxiliary substances by modification with silicon-organic oligomers1 and blending with polymeric flocculants.

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