Peroxide Bleaching of Cellulose Pulp With Chelation-Based Viscosity Control
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Solution Overview
Problem
Existing peroxide bleaching methods for cellulose pulp are hindered by the adverse effects of heavy metals and silica, leading to viscosity loss and inefficiencies, with existing chelating agents requiring additional steps and pH adjustments, and there is a need to control viscosity for different applications.
Innovation Solution
Using disodium 3,3'-((2-ethylhexyl)azanediyl)dipropionate as a chelating agent to stabilize the peroxide bleaching process by chelating metals and controlling pH between 9.5 to 13, optionally with copper compounds to adjust viscosity, in one or two stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional peroxide bleaching is carried out without specific chelating agents, then the bleaching process is simpler, but heavy metals cause cellulose breakdown and viscosity loss
Solution Approach 1:
A specific chelating agent (disodium 3,3'-((2-ethylhexyl)azanediyl)dipropionate) is introduced as an intermediary substance to bind heavy metal ions, preventing them from catalyzing cellulose degradation. This mediator approach resolves the contradiction by protecting viscosity (improving reliability) while maintaining a relatively simple single-stage process (limiting complexity increase).
Solution Approach 2:
The invention optimizes specific parameters including pH range (9.5-13), temperature (40-90°C), and chelating agent concentration to achieve effective heavy metal chelation while preserving cellulose viscosity. By carefully controlling these parameters, the process achieves high viscosity retention without requiring multiple complex treatment stages.
2Reliability
If existing chelating agents like EDTA or DTPA are used, then heavy metals are effectively bound, but additional process steps and pH adjustments are required
Solution Approach 1:
The invention combines the chelating agent treatment and peroxide bleaching into a single integrated stage, eliminating the need for separate treatment steps required by conventional agents like EDTA or DTPA. The specific chelating agent disodium 3,3'-((2-ethylhexyl)azanediyl)dipropionate is designed to function effectively within the peroxide bleaching pH range (9.5-13), allowing simultaneous heavy metal binding and bleaching in one process step, thus improving productivity while maintaining reliable heavy metal removal.
3Productivity
If peroxide bleaching is performed at high pH to improve bleaching efficiency, then silica dissolves and forms precipitates, but the bleaching effectiveness increases
Solution Approach 1:
The invention converts the potentially harmful effect of silica dissolution at high pH into a beneficial outcome by using the chelating agent to manage metal-silica interactions. The specific chelating agent prevents harmful metal-catalyzed cellulose degradation while allowing the high pH conditions needed for effective peroxide bleaching to proceed, thus achieving high bleaching efficiency without the negative consequences of silica precipitate formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Achieves controlled production of high or low viscosity bleached pulps suitable for paper and packaging, maintaining pulp quality and efficiency by stabilizing the bleaching process and preventing impurity effects.
Implementation Method 1
treating the cellulose pulp with disodium 3,3'-((2-ethylhexyl)azanediyl)dipropionate as a chelating agent to chelate metals present in the pulp
Implementation Method 2
peroxide bleaching the cellulose pulp in at least one stage at a pH of about 9.5 to about 13
Data Source
AI summary
A method of controlling viscosity in peroxide bleaching of a cellulose pulp, comprising treating the cellulose pulp with disodium 3,3'-((2-ethylhexyl)azanediyl)dipropionate as a chelating agent to chelate metals present in the pulp; peroxide bleaching the cellulose pulp in at least one stage at a pH of about 9.5 to about 13.