| 摘要 |
<p>1. Process for bleaching chemical paper pulps using hydrogen peroxide, characterized in that the operation is carried out in a single stage at a pH of 11 to 11.5, at a temperature of 70 degrees C to 100 degrees C, with the aid of a solution containing, in addition to hydrogen peroxide, at least one alkaline agent chosen from sodium hydroxide and sodium carbonate, at least one alkali metal silicate at a concentration of at least 0.3% by weight, expressed as SiO2 , at least one magnesium salt and at least one calcium salt in such quantity that the weight concentration of each of these alkaline-earth elements is between 0.05% and 1%, these elements being maintained in the dissolved state with the aid of at least one complexing agent for alkaline-earth ions in such quantity that the total concentration of complexant does not exceed 10% by weight.</p> |
