Cellulose Ester Fiber Composition for Wet-Laid Paper Drainage

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Solution Overview

Problem

Wet laid paper production faces challenges such as slow water drainage rates, which limit production speed and increase energy consumption, and the use of synthetic fibers can lead to web breaks and operational interruptions due to agglomeration and refining issues, while also reducing wet tensile strength.

Innovation Solution

A composition comprising non-fibrillated virgin or waste/recycle cellulose fibers combined with cellulose ester staple fibers having specific features like denier per filament, cut length, crimping, or non-round shape, along with additives, to enhance drainage rates and maintain wet tensile strength, allowing for increased production speed and reduced energy consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If more refining energy is applied to improve web strength and toughness, then the freeness of the pulp is reduced, but the drainage rate of water from the web becomes slower

Engineering Contradiction:

Improveweb strength and toughnessVSAvoiddrainage rate

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

Cellulose ester staple fibers act as an intermediary substance added to the pulp slurry to modify the interaction between cellulose fibers and water. These fibers improve drainage rate by changing the physical structure of the slurry, allowing water to drain more efficiently while maintaining web strength through fiber networking.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes physical parameters of the pulp system by introducing cellulose ester fibers with specific properties (denier per filament less than 3, cut length less than 6 mm, crimping, or non-round shape). This parameter change allows the system to achieve both high strength and fast drainage without requiring excessive refining energy.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If synthetic fibers are used to improve drainage rate, then drainage rate increases, but the synthetic fibers can be damaged or melted or rolled into agglomerates in the refiner, leading to web breaks and operational interruptions

Engineering Contradiction:

Improvedrainage rateVSAvoidweb breaks and operational interruptions

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent uses cellulose ester staple fibers that are designed to be consumed or transformed during the refining process rather than surviving it intact. These fibers serve their drainage-enhancing function during slurry preparation and then break down or integrate into the web structure, avoiding the problems of synthetic fiber damage and agglomeration.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention creates a composite material system combining cellulose fibers with cellulose ester staple fibers. This composite approach leverages the benefits of both fiber types: the structural integrity of cellulose and the drainage-enhancing properties of cellulose ester, while avoiding the drawbacks of purely synthetic fiber additions.

Inventive Principle:

Principle #40Composite materials

3Strength

If synthetic fibers are added after cellulose fibers are refined to avoid refiner damage, then web strength is maintained, but process complexity increases significantly requiring additional equipment

Engineering Contradiction:

Improvewet tensile strengthVSAvoidprocess complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The invention merges the addition of cellulose ester staple fibers with the existing pulp slurry preparation process. Both cellulose fibers and cellulose ester fibers are combined in the same refiner and processed together in a single operation, eliminating the need for separate addition equipment and reducing process complexity.

Inventive Principle:

Principle #5Merging (Combining)

4Productivity

If machine line speed is increased to boost production, then productivity increases, but energy consumption in the drying section increases or product moisture specification is exceeded

Engineering Contradiction:

Improvemachine line speedVSAvoiddryer energy input

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The invention performs preliminary water removal action during the forming section by incorporating cellulose ester staple fibers that enhance drainage rate. This preliminary drainage reduces the water content before the web enters the drying section, allowing higher machine speeds without proportionally increasing dryer energy consumption.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11530516B2Composition of matter in a pre-refiner blend zone

Publication Date: 2022.12.20 EASTMAN CHEM CO

AI summary

A composition is contained a blend zone prior to refining containing non-fibrillated virgin cellulose fibers, waste/recycle cellulose fibers or both; cellulose ester fibers, water, and one or more additives comprising fillers, internal sizing agents, biocides, process anti-foaming agents, colorants, optical modifiers, or a combination thereof. An in-line mixer can be used for adding the additives, and the consistency of the composition is lowered relative to a feed of material from a hydropulper.