Co-refining Cellulose Ester Staple Fibers for Wet Laid Drainage

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Solution Overview

Problem

Wet laid paper production faces challenges such as slow water drainage rates, reduced tensile strength, and increased energy consumption due to the limitations of refining cellulose fibers, which can be exacerbated by the use of synthetic fibers that may damage or agglomerate in refiners, leading to web breaks and operational interruptions. Additionally, there is a need for improved air and water permeability, reduced basis weight, and increased bulk without compromising product properties.

Innovation Solution

A process incorporating cellulose fibers and cellulose ester staple fibers, where the cellulose ester fibers have specific features like denier per filament less than 3.0, cut length less than 6 mm, and crimped shape, are co-refined with cellulose fibers to enhance drainage rates, tensile strength, and permeability, while allowing for reduced energy consumption and increased production speed without altering the final product's moisture content.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If more refining energy is applied to cellulose fibers, then the strength and toughness of the web is improved, but the drainage rate of water from the web is reduced

Engineering Contradiction:

Improveweb strengthVSAvoiddrainage rate

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The patent combines cellulose fibers with synthetic fibers (polyester, nylon, acrylic) to create a composite web structure. The synthetic fibers serve as drainage promoters that do not require refining, allowing the cellulose fibers to be sufficiently refined for strength while maintaining high drainage rates through the composite structure.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies different fiber types in specific locations and proportions within the web. Synthetic fibers are incorporated at controlled levels (5-50% by weight) to perform specific drainage functions in certain regions of the web, while cellulose fibers provide the bulk structural strength.

Inventive Principle:

Principle #3Local quality

2Productivity

If machine line speed is increased to boost production, then productivity is improved, but dryer energy consumption increases

Engineering Contradiction:

Improveproduction rateVSAvoiddryer energy input

Core Design Contradiction:

ProductivityVSUse of energy by stationary object

Solution Approach 1:

The patent converts the potential harm of high-speed operation (insufficient drying time) into a benefit by using synthetic fibers that enable faster drainage. The improved drainage from synthetic fiber incorporation pre-dries the web before it enters the dryer, reducing the energy burden on the dryer even at high line speeds.

Inventive Principle:

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

Solution Approach 2:

The synthetic fibers perform a preliminary drainage function before the web reaches the dryer section. By accelerating water removal during the forming and pressing stages through the drainage-promoting synthetic fibers, the web enters the dryer with lower moisture content, reducing the energy required for final drying.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If synthetic fibers are added to improve drainage rate, then water drainage is improved, but wet tensile strength drops and web processing becomes difficult

Engineering Contradiction:

Improvedrainage rateVSAvoidwet tensile strength

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent carefully controls the parameters of synthetic fiber incorporation, including fiber type, diameter, length, and most importantly the weight percentage (5-50%). By optimizing these parameters, the patent achieves sufficient drainage improvement while maintaining adequate wet tensile strength for web processing.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent distributes synthetic fibers non-uniformly or in specific zones within the web structure to maximize drainage benefits in water-rich areas while preserving strength-critical regions with higher cellulose fiber content. This localized approach allows drainage optimization without sacrificing overall web integrity.

Inventive Principle:

Principle #3Local quality

4Quantity of substance

If basis weight is reduced to improve air and water permeability, then permeability is improved, but product strength may be compromised

Engineering Contradiction:

Improvebasis weightVSAvoidproduct strength

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The patent creates a lightweight composite structure by incorporating synthetic fibers that have different density and structural properties than cellulose. This composite approach allows reduced basis weight while maintaining strength through the synergistic combination of fiber types, where synthetic fibers provide structural support despite lower overall material quantity.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS11401659B2Process to produce a paper article comprising cellulose fibers and a staple fiber

Publication Date: 2022.08.02 EASTMAN CHEM CO

AI summary

The present invention provides compositions comprising cellulose fibers and cellulose ester fibers and wet laid articles made from the compositions, as well as wet laid processes to produce these compositions. More specifically, the present invention provided compositions comprising cellulose fibers and cellulose acetate fibers and wet laid articles made from these compositions as well as wet laid processes to produce these compositions. The present invention also relates to developing a composition, process, wet laid product, or articles exhibiting any one of many desired benefits.