Segmented Wood Pulp Refining for Low-Density Paperboard

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Solution Overview

Problem

Conventional paperboard production methods result in high fiber density due to excessive refining, leading to reduced bulk and strength properties, while attempting to achieve lower densities with comparable strength is challenging.

Innovation Solution

A selective refining approach where a portion of wood pulp fibers is refined to high energy levels (at least 150 kWh/metric ton) and another portion is kept unrefined or refined at low energy levels (up to 10 kWh/metric ton), creating a fiber blend that optimizes bonding and retains fiber strength, allowing for lower density paperboard production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If wood pulp fibers are refined to conventional energy levels (20-120 kWh/ton), then fiber bonding is improved, but fiber density increases and bulk decreases

Engineering Contradiction:

Improvefiber bondingVSAvoidbulk

Core Design Contradiction:

StrengthVSVolume of stationary object

Solution Approach 1:

The fiber population is segmented into two distinct groups: a first amount of fibers refined to high energy levels (at least 150 kWh/ton) and a second amount of fibers refined to low energy levels (at most 10 kWh/ton). This segmentation allows different fibers to serve different functions - highly refined fibers provide bonding while unrefined fibers maintain bulk and strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different refining levels are applied to different portions of the fiber population. The first amount of fibers receives intensive refining treatment locally to maximize bonding, while the second amount of fibers receives minimal or no refining to preserve their bulk and strength properties. This local differentiation resolves the contradiction between bonding and bulk.

Inventive Principle:

Principle #3Local quality

2Strength

If wood pulp fibers are refined to high energy levels (at least 150 kWh/ton), then fiber bonding is significantly improved, but energy consumption increases

Engineering Contradiction:

Improvefiber bondingVSAvoidenergy consumption

Core Design Contradiction:

StrengthVSUse of energy by moving object

Solution Approach 1:

Instead of refining all fibers to high energy levels, only a portion (the first amount) is subjected to excessive refining (at least 150 kWh/ton). The remaining fibers (the second amount) are refined minimally (at most 10 kWh/ton). This partial application of excessive refining achieves the necessary bonding while avoiding the energy waste of over-refining all fibers.

Inventive Principle:

Principle #16Partial or excessive action

3Ease of manufacture

If conventional refining is applied to all fibers, then processing is simplified, but paperboard density increases and production efficiency decreases

Engineering Contradiction:

Improveprocessing simplicityVSAvoidproduction efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The fiber stream is divided into two streams with different refining treatments. The first stream undergoes high-energy refining while the second stream undergoes low-energy refining. This segmentation enables the production of lower density paperboard with improved production efficiency while maintaining manageable processing through a systematic two-stage approach.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11629460B2Fiber blend, method for producing fiber blend, and paperboard product comprising fiber blend

Publication Date: 2023.04.18 WESTROCK MWV LLC

AI summary

A fiber blend includes a first amount of wood pulp fibers refined in an amount of at least about 150 kWh per metric ton of gross refining energy, and a second amount of wood pulp fibers refined in an amount of at most about 10 kWh per metric ton of gross refining energy.