Dry Strength Alternatives:CMC and Guar Gum

Jeffrey C. PetersGlobal Applications Development Manager

Hercules IncorporatedPulp and Paper Division

Table of Contents

• Dry Strength Additive Function

• Strength Fundamentals

• Carboxymethylcellulose

• Guar Gum

Dry Strength Additive Function

• Increase ultimate strength properties

• Reduce costs

• Increase productivity

Chemical Strength Fundamentals

• Increase fiber-fiber strength– Increased net bonded area (NBA)– Increased strength per bonded area

• Anionic/cationic polymer combinations– Most effective– Net positive charge

Carboxymethylcellulose

CMC

CMC Overview

• Used over 30 years with PAE resin

• Forms: dry, liquid, fluidized suspension– Degree of substitution– Molecular weight– Particle size– Purity

• Performance - depends upon chemistry

Cellulose Gum (CMC)

OO

O

H

HH

H

H H

H

HH

HOH

OH

OH

OH

O

CH2OCH2COONa

CH2OCH2COONa

Structure of Cellulose

OO

O

HH

H

H

H H

H

HH

HOH

OH

OH

OH

O

CH2OH

CH2OHn - 2 2

CMC Types

Viscosity Type Viscosity (cPs)2% solution

Common Use

Very Low 15 Coatings

Low 40 Calender Stack

Medium 500 Internal Strength

High 20,000 Size Press

Factors Affecting Performance

• pH– Range 4 - 10

• Temperature– Minimal degradation

at 82 °C

• Water Hardness– Minimal effect <300

ppm

• Anions– Monovalent - soluble– Divalent - less soluble– Trivalent - precipitate

Recommended InternalAddition Procedures

• Prepare 1 - 2% solution– Fresh water dilute to <0.5% at point of

addition

• Cationic resin for retention

• Added before or after cationic resin– After is most widely used

Recommended InternalAddition Procedures (cont.)

• Typical dosage rates: 1 - 3 kg/T

• Chemistry balance is CRITICAL

Performance Benefits

Grade BenefitsTowelBoardSpecialties

• Dry tensile up to 40%• Double wet tensile• Wet/dry tensile – 30+%

RecycledPaperboard

• Curl control• Lint control• Coating holdout

Fine Paper(Size press withstarch)

• Taber stiffness improvement- MD 12%, CD 22%

• Tensile improvement- MD 12%, CD 23%

CMC Summary

• Advantages– Predictable results– Excellent

performance in cleansystems

– Well understoodchemistry

• Disadvantages– Dry product handling– Reduced performance

in dirty systems– Requires cationic

retention component

Guar Gum

Guar Gum Overview

• Developed in the 1950’s

• Derived from the Guar seed

• Used as a thickener, retention/drainageaid, strength aid

Non-Ionic Guar Gum

H

HO

HOH

H

OH

H

CH2OH

O

H

O

HOH

H

OH

H

CH2

O

H

O

HOH

H

OH

H

CH2OH

O

OH O

HH

H

OH

OH

CH2OH

H

H

O

• High affinity for cellulose– Chemically similar to cellulose

• Forms many hydrogen bonds– “Rigid Rod”

• Acts like a low molecular weight polymer– MW ~ 1 million (starch 1 - 10; PAM 10 - 14)

Guar Properties

Guar Properties (cont.)

• Cationic Guar– +1.2 meq/gm

• 4 - 6 times higher than starch

Factors Affecting Performance

• System Charge - Primary Affect• pH

• Temperature

• Water Hardness Minimal Affect• Conductivity

• Alkalinity/Acidity

Recommended InternalAddition Procedure

• Determine target benefit– Retention, drainage, formation or strength

• Characterize system/lab study

• Point of addition– Thick stock for strength– Thin stock for retention/drainage

Recommended InternalAddition Procedure (cont.)

• Prepare 0.75% solids solution, cleanwater

• Typical dosage level: 1 - 1.5 kg/T– Range 0.5 - 3 kg/T

Performance Benefits

Product Grade BenefitsCationic Guar0.15% dosage

Kraft CorrugatedMedium(Slightly anionic)

• STFI increase 22%• First pass retention increase 7%

Cationic Guar0.2% dosage

100% Closed OCCLinerboard(High anionic trashlevel)

• Ring crush/BW increase 11%• First pass retention increase 6%• Speed increase 25 mpm

Anionic Guar0.15% dosage

Fine Paper(High amts. alum andcat. starch- systemcationic)

• Scott bond increase 130 to 250+• First pass retention increase 10%• 5% MD and 16% CD tensile increase

AmphotericGuar0.075% dosage

100% Closed OCCLinerboard(16,000 mmhos)

• Ring crush increase 12%• First pass retention increase 10%• Speed increase 10 mpm

Guar Summary

• Advantages– Strength enhancement– Drainage, retention,

formation improvement– Adsorption not charge

dependent– Effective in high

anionic trash systems– Reduces BOD

• Disadvantages– Dry product handling– System charge

monitoring foroptimization

– Cost

CMC and Guar Summary

• Enhance dry and/or wet strength• Carboxymethylcellulose

– Cationic polymer– Clean systems

• Guar Gum– Self-retaining– “Dirty” systems

• Dry materials