Dissolving Wood Pulp Production via Acid Prehydrolysis and Peroxide Bleaching

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Solution Overview

Problem

Current methods for producing dissolving wood pulps are costly due to the need for extensive prehydrolysis and the use of hypochlorite, which poses environmental concerns, and they struggle to achieve the required purity and properties for applications like viscose fibers without excessive chemical usage.

Innovation Solution

A method involving acid prehydrolysis followed by kraft cooking and a multi-stage bleaching process, including an oxidation stage with peroxide and metal catalysts under acidic conditions, to produce medium-purity dissolving wood pulps with improved reactivity, filterability, and reduced viscosity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If extensive prehydrolysis is used to increase alpha cellulose content, then purity is improved, but yield decreases and production cost increases

Engineering Contradiction:

Improvealpha cellulose contentVSAvoidyield

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The invention changes the severity parameters of prehydrolysis (temperature, time, acid concentration) to achieve optimal alpha cellulose content while minimizing yield loss. By carefully controlling prehydrolysis conditions rather than using extensive treatment, the process achieves sufficient purity without excessive yield penalty.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention applies partial prehydrolysis rather than extensive treatment, achieving sufficient alpha cellulose content improvement without the diminishing returns and excessive yield loss associated with more severe prehydrolysis. This partial action approach balances purity gain with yield preservation.

Inventive Principle:

Principle #16Partial or excessive action

2Manufacturing precision

If hypochlorite is used for viscosity reduction and purification, then pulp quality is improved, but environmental harm increases due to chlorinated organic byproducts

Engineering Contradiction:

Improvepulp qualityVSAvoidchlorinated organic byproducts

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The invention replaces harmful hypochlorite oxidation with beneficial peroxide-based oxidation systems (H2O2, CO2, O2) that produce environmentally benign byproducts. This converts a harmful chemical process into a beneficial one, maintaining pulp quality improvement while eliminating chlorinated organic contamination.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The invention uses inexpensive, environmentally friendly oxidizing agents like hydrogen peroxide, carbon dioxide, and oxygen that decompose into water and gas, replacing expensive and harmful hypochlorite. These short-living reagents leave no persistent harmful residues in the pulp or environment.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If traditional high-purity dissolving pulps are produced, then reactivity and filterability are improved, but production cost increases

Engineering Contradiction:

ImprovereactivityVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention optimizes multiple process parameters including prehydrolysis severity, kraft cooking conditions, and peroxide oxidation dosage to achieve the minimum necessary reactivity and filterability for dissolving pulp applications. By tuning these parameters rather than maximizing them, the process achieves sufficient performance at lower cost.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces mechanical/chemical intensive purification methods (extensive prehydrolysis, hypochlorite treatment) with a more efficient peroxide-based oxidation system that achieves the necessary reactivity and filterability improvements more economically and with fewer process steps.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This method reduces production costs, minimizes environmental impact, and produces pulps suitable for various applications, including viscose fibers, with enhanced properties such as filterability and reduced clogging values, while avoiding the need for excessive prehydrolysis and hypochlorite use.

Implementation Method 1

subjecting a cellulosic material to an acid prehydrolysis process

Methodology Applied

Scientific EffectHydrolysis: Hydrolysis

Implementation Method 2

oxidizing the pulp with at least one peroxide and at least one iron or copper catalyst under acidic conditions

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentEP3755839B1Novel dissolving wood pulps and methods of making and using the same

Publication Date: 2024.08.21 GP CELLULOSE GMBH

AI summary

This disclosure relates to methods of making novel dissolving wood pulps by processes comprising acid prehydrolysis, pulping, and a multi-stage bleaching process comprising oxidation with a catalyst and peroxide under acidic conditions, as well as to products made therefrom having a combination of medium-purity, low viscosity, and improved reactivity, filterability, and/or clogging that can be used as a substitute for traditional high-purity dissolving pulps in a wide variety of applications.