w.e.chemistry

WET END CHEMISTRYWET END CHEMISTRYA QUICK REVIEWA QUICK REVIEW

Paper was invented in China more than Paper was invented in China more than 2000 years ago.2000 years ago.

Paper has become an important part in the Paper has become an important part in the development of human civilizations.development of human civilizations.

The industrialization of the world has led to The industrialization of the world has led to the continuous search for improvement in the continuous search for improvement in the quality and productivity of the paper the quality and productivity of the paper manufacturing process.manufacturing process.

INTRODUCTIOINTRODUCTIONN

WHY USE PAPER- WHY USE PAPER- MAKING ADDITIVES?MAKING ADDITIVES?

JUST WOODFIBERS, VIRGIN OR RECYCLED, PLUS WATER WILL NOT MAKE YOU THE PAPER QUALITY YOUR CLIENT REQUIRES…

A MODERN PAPER MACHINE

WET END CHEMISTRY CONTROLWET END CHEMISTRY CONTROL

INCREASE DRAINAGE & RETENTIONINCREASE DRAINAGE & RETENTION

STOCK DEAERATION AND FOAM STOCK DEAERATION AND FOAM

CONTROLCONTROL

FORMATION AIDFORMATION AID

DEPOSIT CONTROLDEPOSIT CONTROL

SIZING / LIQUID BARRIERSIZING / LIQUID BARRIER

PAPER STRENGTH ENHANCEMENTPAPER STRENGTH ENHANCEMENT

WET END CHEMISTRY CONTROLWET END CHEMISTRY CONTROL

pH ControlpH Control - agglomeration of “sticky” materials,- agglomeration of “sticky” materials,

- brightness loss,- brightness loss,- drainage / wet line variation- drainage / wet line variation

Anionic Trash ControlAnionic Trash Control- High anionic trash content can cause - High anionic trash content can cause stickies problems agglomerationstickies problems agglomeration- Also high chemicals consumption- Also high chemicals consumption

pH control AdditivespH control Additives AlumAlum Caustic SodaCaustic Soda Sulfuric AcidSulfuric Acid Sulfur DioxideSulfur Dioxide

WET END WET END CHEMISTRY CHEMISTRY ADDITIVESADDITIVES

Typical pH control ranges:Typical pH control ranges: Rosin sizing pH 4-6Rosin sizing pH 4-6 AKD ph 7-8AKD ph 7-8 ASA pH 4-8ASA pH 4-8

Note: When using calcium carbonate as filler Note: When using calcium carbonate as filler ph stabilizes at about 8.0 without need for ph stabilizes at about 8.0 without need for

any additive.any additive.


WET END CHEMISTRY WET END CHEMISTRY ADDITIVESADDITIVES

Anionic Trash ControlAnionic Trash Control ““Anionic trash” - dissolved or Anionic trash” - dissolved or

colloidally dispersed anionic colloidally dispersed anionic or non-or non-ionicionic materials which materials which inhibits the effectiveness of inhibits the effectiveness of cationic additives.cationic additives.


ATCATC or Anionic Trash or Anionic Trash Control additives, are Control additives, are therefore necessary in therefore necessary in modern paper making.modern paper making.

WET END WET END CHEMISTRY CHEMISTRY ADDITIVESADDITIVES TYPICAL ATC ADDITIVES :

ALUM / PAC ACH POLYAMINE POLYDADMAC

WET END CHEMISTRY WET END CHEMISTRY ADDITIVESADDITIVES

““Stickies” ControlStickies” Control TalcTalc BentoniteBentonite Coagulants / ATCCoagulants / ATC

Wet End Chemistry Wet End Chemistry AdditivesAdditives

Alum based ATC’s:Alum based ATC’s: BASIC ALUMBASIC ALUM POLYALUMINUM CHLORIDE (PAC)POLYALUMINUM CHLORIDE (PAC) ALUMINUM CHLOROHYDRATE (ACH)ALUMINUM CHLOROHYDRATE (ACH)


Alum, PAC, ACH are:Inorganic polymers with low

molecular weights and relatively high cationic charge.

Traditionally used as ATC’s and fixing agents for acid to neutral papermaking processes.

Very quick acting and have very high affinity to the anionic cellulose fibers and fines.


Polyamine & Polyamine & PolydadmacPolydadmac Low molecular weight Low molecular weight

high cationic charge high cationic charge organic polymers.organic polymers.

ATC’s and coagulants in ATC’s and coagulants in neutral to alkaline paper neutral to alkaline paper making processes.making processes.

Wet End Wet End Chemistry Chemistry AdditivesAdditives

• Polydadmac has relatively higher molecular weight than polyamine.

• Usually used in very high filler furnishes.

• Polyamine is used mostly in de-inked and mechanical pulp furnishes.

INCREASE DRAINAGE & RETENTIONINCREASE DRAINAGE & RETENTION

Two of the most important Two of the most important factors in papermaking which factors in papermaking which affects quality and productivity.affects quality and productivity.

They can be opposing They can be opposing variables.variables.

There are additives that which There are additives that which can control and to improve.can control and to improve.

DRAINAGE & RETENTION DRAINAGE & RETENTION HISTORYHISTORY

Single Polymer utilized anionic or cationic

flocculants which were developed in the early years for acid paper making systems.

In a way it is a dual program with “alum” as the coagulant part.

Alum is used for both sizing and as coagulant / fixing agent.


Dual Polymer developed for alkaline systems

using AKD or ASA as sizing additive.

No alum so cationic starch, polyamine or polydadmac based coagulants are used.

flocculants used can either be cationic or anionic.


Micro Particle an improvement over the dual polymer program,

this technology was developed mainly to improve not only retention but also dewatering or drainage.

micro particle used typically bentonite or colloidal silica.

How does it work?How does it work?

Charge neutralization-coagulation:Charge neutralization-coagulation:

Low molecular weight and high cationic Low molecular weight and high cationic charge solution polymers are used.charge solution polymers are used.

Anionic trash, fiber fines, and fillers Anionic trash, fiber fines, and fillers which are highly anionic are neutralized.which are highly anionic are neutralized.

Microflocs are formed.Microflocs are formed.

Bridging Mechanism:Bridging Mechanism:Most retention polymers work by forming Most retention polymers work by forming bridges between fibers, fines, and fillers.bridges between fibers, fines, and fillers.

A long chain polymer e.g. PAM, starch, A long chain polymer e.g. PAM, starch, will stick to the surface of one fiber, while will stick to the surface of one fiber, while the other end will stretch out and bond to the other end will stretch out and bond to a second fiber or filler.a second fiber or filler.

Retention Program Retention Program MechanismMechanism The main purpose of a retention The main purpose of a retention

program is to floc together the fillers program is to floc together the fillers and fines to retain these in the sheet at and fines to retain these in the sheet at the same time increase drainage.the same time increase drainage.

The smaller the The smaller the flocs, the less they flocs, the less they interfere with interfere with drainage.drainage.

Flocculants Flocculants however create however create large flocs that large flocs that hurt dewatering.hurt dewatering.

Micro Particle MechanismMicro Particle Mechanism

The main purpose of a microparticle The main purpose of a microparticle is to control floc formationis to control floc formation

Flocs are not so small but also not Flocs are not so small but also not too bigtoo big

Enough to be retained in the sheet Enough to be retained in the sheet at the same time increase drainage.at the same time increase drainage.

Micro Particle Colloidal Silica

Anionic Colloidal Silica, Reacts with the cationic

component (Starch or polymer) to create a floc structure that increases dewatering and retention, while improving formation.

It can be used to increase: PRODUCTION RETENTION FORMATION SHEET STRENGTH

Colloidal SilicaMechanism

The starch can branch out and bond together fines and fillers.

While the silica is small enough to go inside the starch or a pam polymer molecule, neutralize its charge, and make it collapse into a small floc...

Starchor Polymer Silica

FlocCollapses

FlocCollapses

FlocCollapsed

Fiber, AKD,PCC

Microparticle MechanismThe microparticle

mechanism of colloidal silicacreates:

small dense flocs that are tightly anchored to the long fibers.

small flocs that leave open area for improved drainage, pressing, and drying.

STOCK STOCK DEAERATION AND DEAERATION AND FOAM CONTROLFOAM CONTROL

A mixture of cellulose fibers, water, residual chemicals, unretained

additives, mixed with air inevitably leads to

FOAMING

A Paper machine wet end is A Paper machine wet end is mechanically designed to mechanically designed to

prevent / minimize the prevent / minimize the possibility of air entrainment. possibility of air entrainment.

Upsets in the wet end Upsets in the wet end operations and/or chemistry operations and/or chemistry

however, can happen and however, can happen and lead to foaming problems.lead to foaming problems.

Foam / Air entrainment in the stock can lead to:

Poor formation and drainage, (sub-surface foam in newsprint

grades)

Sheetbreaks Deposit problems Finished paper quality problems

DEFOAMERS / ANTIFOAM AGENTS(for paper machine applications)

Fatty Alcohol basedFatty Alcohol based

Polyol Ester (PEG ester, PPG Polyol Ester (PEG ester, PPG ester)ester)

Polyethylene Glycol basedPolyethylene Glycol based

MECHANISMS OF FOAMING & DEFOAMING:

CHOOSING THE BEST DEFOAMER FOR YOUR APPLICATION.. Screening tests parameters:Screening tests parameters: Low or no adverse effect to Low or no adverse effect to sizingsizing Minimum dosageMinimum dosage knockdownknockdown PersistencePersistence

A TYPICAL DEFOAMER TEST CHART:

230HT & 230G EVALUATION USING 1.0% BLACK LIQUORAVERAGE OF DEFOAMER EVALUATION

0.9

0.91

0.92

0.93

0.94

0.95

0.96

0.97

0.98

0.99

1

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99106113120127134141148155162TIME, SECONDS

SPECIFIC GRAVITY

FB230HT 090408-82FB230HT 120308 L-97/96FB230G 121808-90FB230G 122008-91

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