Pre-cationization of cotton fabrics: An effective alternative tool for activation of hydrogen peroxide bleaching process

New development for combined bioscouring and bleaching of cotton-based fabrics

The manganese(III)-containing tungstophosphate [MnIII3(H2O)5(A-α-PW9O34)2]9−

A series of transition metal substituted polyoxotungstates (TMSP) were tested as catalysts for the oxygen delignification of eucalypt kraft pulp. These include Mn substituted polyoxotungstates of Keggin-type, α - [ Si W ( 12 − n ) M n n III ( H 2 O ) n O ( 40 − n ) ] ( 4 + n ) − ( n  = 1 ( 1 ) or n  = 2 ( 2 )), sandwich-type α -B- [ ( P W 9 O 34 ) 2 M n ( 4 − n ) II M n n III ( H 2 O ) 2 ] ( 10 − n ) − ( n  = 1 ( 3 ) or n  = 3 ( 4 )), and the transition metal mono-substituted Keggin-type anions, such as α-[XW 11 M(H 2 O)O 39 ] n − (M = Co III , X = Si ( 5 ) and X = B ( 6 ); M = Ru IV , X = Si ( 7 ), and X = P ( 8 )). All TMSP showed a catalytic activity. The experimental results revealed high selectivity of the residual lignin oxidation during oxygen delignification catalysed by 1 – 4 , though the final kappa number of delignified pulps varied significantly. This was related to the removal of hexeneuronic acid residues at low pH diminishing the corresponding pulp kappa number counterpart. A comparison of the kappa number decrease and the delignification selectivity in conventional oxygen-alkaline bleaching process and in the TMSP-catalysed oxygen delignification showed significant advantages of the latter process. The best results, concerning both the delignification degree and the selectivity of delignification, were obtained with TMSP α-[SiW 11 Mn III (H 2 O)O 39 ] 5− ( 1 ), α -B- [ ( P W 9 O 34 ) 2 M n II M n 3 III ( H 2 O ) 2 ] 7 − ( 4 ) and α-[SiW 11 Co III (H 2 O)O 39 ] 5− ( 5 ). The application of catalysts 6 – 8 was limited by their structural instability under the delignification conditions. The practical aspects of the oxygen delignification catalysed by TMSP are discussed.

Transition metal substituted polyoxotungstates for the oxygen delignification of kraft pulp

Strong natural bast fibers, especially flax fibers, can be used to replace glass fibers in reinforced composites. The properties of natural fibers depend largely on maturity, retting and processing. Two chemical treatments were applied to retted and semiretted flax fibers to create better fiber to resin bonding and to show the effect of retting degree and successive purification processes on the mechanical properties of natural composite materials. Retted and semiretted flax fibers have been scoured and bleached with the objective of removing surface impurities and developing finer structure. To investigate the effect of adhesion promoter on the mechanical properties of natural fiber composite, a composite sample was prepared from bleached retted flax pretreated with adhesion promoter Isostearoyltitanate (ISTT). After treatments the fibers got cleaner and the measurements showed that the fiber fineness as well as the surface free energy increased. The treatments were accompanied by decrease in the fiber t...

Surface Characterization of Differently Pretreated Flax Fibers and Their Application in Fiber-Reinforced Composites

The manganese substituted heteropolytungstates α-[(Mn(H2O))SiW11O39]6− (1), α-[(Mn(H2O))2SiW10O38]8− (2), α-[(Mn(H2O))3SiW9O37]10− (3), β-[(Mn(H2O))3SiW9O37]10− (4), and α-[(Mn(H2O))3PW9O37]9− (5) were applied as catalysts for low-temperature bleaching of stained cotton cloth. The bleaching activity of this series of catalysts is correlated to the fibre-damage induced to cotton cloths during washing as well as to the stability of the catalysts under simulated washing conditions.

Michael Wohlers

Papers

Low-temperature bleaching with manganese-containing heteropolytungstates