Silicate Replacement by DTPMPA in Peroxide Bleaching of Industrial Chemimechanical Pulps

56. BARBOZA, O.M., AREA, M.C., FELISSIA, F.E., VENICA, A.D.

Belo Horizonte, MG, Brazil

Simposio; 7TH Brazilian Symposium on the Chemistry of Lignins and Other Wood Components; 2001

Universidade de Viçosa

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin-top:6.0pt; margin-right:0cm; margin-bottom:6.0pt; margin-left:0cm; text-align:justify; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES-AR; mso-fareast-language:ES;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The objective is to evaluate the bleaching performance of an industrial chemimechanical pulp when the silicate is replaced by DTPMPA in peroxide bleaching liquor. The raw material was a hardwood cold soda chemimechanical pulp (25 % poplar and 75 % eucalyptus), from Celulosa Argentina S.A. Zárate mill. The bleaching experiences where accomplished on DTPMPA pretreated pulps, following a binary mixture design with Silicate / DTPMPA relations of: 5/0; 3/0.2; 1/0.4; 0/0.6. Pretreatment conditions were: 20 minutes, 60 ºC, 0.5 % of chelant (on o.d. pulp) at 3 % of consistency. The bleaching liquor was composed of hydrogen peroxide (6 %), sodium hydroxide (1.6 %), sodium silicate and DTPMPA, in agreement with the corresponding ratios of the experimental design. Bleaching experiences were completed at 75 ºC during 2 hours. The pulps were neutralized and washed, and the handsheets for optical tests were made immediately after. Brightness and L*, a*, b* color parameters were determined. The reversion by effect of time and temperature were also determined. The results indicate that it is possible to partially replace silicate, combining 1 % of silicate and 0.4 % of DTPMPA. The presence of this chelant in the bleaching liquor produces a brighter pulp, greater brightness stability and lower peroxide consumption. The possible reasons of this behavior are discussed.