Miroslav Antal

Quaternized xylans: synthesis and structural characterization

Abstract Quaternization xylans were prepared by treating xylans differing in structural and molecular properties with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHMAC) in aqueous NaOH under mild reaction conditions. The degree of substitution with quaternary ammonium groups can be monitored by altering the amount of CHMAC at optimum molar ratios of NaOH/CHMAC in the range 1·2-1·6, without changing the structure of the xylan backbones. Hot water pretreatment of the xylans in the alkaline activation step significantly enhances their reactivity. The presence of alkylammonium substituents was revealed by IR and NMR spectroscopy. The applicability of quaternized xylans as a retention aid in papermaking is demonstrated on thermomechanical pulp. Xylans, therefore, represent an important renewable resource for the production of novel cationic biopolymers.

Preparation of microcrystalline cellulose aminoderivatives

Abstract Cellulose aminoderivatives were prepared by the reaction of microcrystalline cellulose (MCC) with alkylating agents 3-chlor-2-hydroxypropyltrimethyl-ammonium chloride (CHMAC) and 1,3-bis(3-chlor-2-hydroxylpropyl) imidazolium hydrogensulphate (BCHPIHS) in an alkaline medium. The examination of the reaction parameters showed the most suitable molar ratio of NaOH/CHMAC to be 1·2(1·5 ml 17·5% NaOH/2·5 ml CHMAC per 1·00 g MCC). At this ratio, the maximum degree of MCC substitution, expressed by the exchanging capacity of trimethylammonium hydroxypropyl (TMAHP) for MCC, was obtained (0·94 mmol/g). By reaction of MCC with BCHPIHS, the optimal molar ratio NaOH/BCHPIHS was 3·00 (4·5 ml 17·5% NaOH/2·4 ml BCHPIHS per 1·00 g MCC). At this molar ratio, the maximum exchanging capacity of 1·56 mmol/g of bis(hydroxypropyl) imidazolium (BHPI) MCC was obtained. The optimal reaction time at 60°C was 2–3 hours.

Fractionation of wheat straw meal after pretreatment with acidified zinc chloride solutions

Abstract Wheat straw was treated with acidified ZnCl 2 solutions and the fractions obtained were compared with results obtained by NaOH treatments. The yields of water-soluble polysaccharides are smaller but they are less contaminated with lignin than analogous fractions obtained by NaOH treatment. The molecular weights of the ZnCl 2 fractions are greater than the NaOH-treated fractions. The arabinose and glucuronic acid residues are hydrolysed from the polysaccharides by ZnCl 2 treatment. Samples treated with ZnCl 2 could be more effectively desalted by washing with ethanol than by precipitation in acetone. NaOH-pretreated samples could not be desalted by washing with ethanol.

Novel cellulose derivative for the in-vitro adsorption of heparin from blood plasma

Abstract The new carrier, bis (hydroxypropyl) imidazolium microcrystalline cellulose (BHP MCC) is presented in this paper. The novel carrier is capable of quantitative removal of heparin from heparin-containing plasma samples. Optimal reaction parameters for the preparation of microcrystalline aminoderivative carrier are examined and application of a prepared carrier is demonstrated.

Thermooxidation of TMAHP-cellulose in dependance to its anionic form

Abstract With the help of DTA, DTG, elementar analysis of carbonised residue and ESR spectroscopy the thermooxidation of trimethylammoniumhydroxyprophyl (TMAHP)-cellulose in dependance to its anionic form was studied. At 300°C the percentage of carbon in carbonised residue run in oxidative atmosphere is higher than for sample run in inert atmosphere. The percentage of hydrogen is decreasing simultaneously. The concentration of free radicals in thermolysed residue is also increasing due to the presence of oxygen. We propose that oxygen is abstracting the hydrogen atoms from polysaccharide and unpaired electrons on carbon atoms are formed. At 400 °C the percentage of carbon in residues run at inert atmosphere is higher than for residue run at oxidative atmosphere. Also the concentration of free radicals in residues is greater in ipert atmosphere than in oxidative one. That is why we suppose that at this temperature oxygen is bonded to polysaccharide residue and free radicals are terminated. From the semiquantitative DTA we can make the following sequence of samples according to their increasing thermooxidative effect: unmodified cellulose − 4 − − − 3 2 PO − 4 3 COO − − 3 − − − .