Biermann Ch. Handbook of Pulping and Papermaking

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454 22. PAPERMAKING CHEMISTRY

Table 22-1. Some TAPPI and other methods of potential interest to papermaking chemistry slurries.

Test Purpose Methodology

Test number and/or notes^

Ash, %

Chlorine

Consistency, %

Dissolved inorganic

Dissolved organic

Dyes

Filler determination

Talc

Fines content

Hardness, Ca & Mg

Inorganic anions^

SO42

H2SO3

Inorganic cations''

Ca in pulp

Zn, Cd

Melamine resin

Nitrogen (total)

Paper

Air permeability

Internal bond

Opacity

Sizing

Wet tensile

Pitch

Pulp

Carboxyl groups

Copper number

External surface

Inorganic filler, etc.

Fast analysis, 5 min

Biocide

Solids content

Fines retention

Corrosion, pulp washing

Determine retention, etc.

Retention

Qualitative analysis

Particles < 70 ptm

Particles < 70 fim

Fundamental

Scale, soap precipitation

Liquor carryover, etc.

Corrosion, buildups

Buildup interferes rosin

Added in bleach plant

Corrosion, scale, etc.

Numerous

Dissolving pulp

Discoloration

Poor pulp washing

Fillers and pigments

Wet strength papers

From PAM, amines, etc.

Formation, floe sizes

Fundamental

Formation, floe size

Fundamental

Wet strength papers

Common problem

Fiber anchor points

Oxidized cellulose

Surface for retention

Fiber length dist. Fundamental

Hemicellulose

Solubility

Water retention

Retention, total

Rosin

Starch

TiO,

Fiber bonding, colloids

Colloidal contribution

Dewatering behavior

Fundamental

Retention, buildup

Cationic should retain

Quantitative analysis

Ashing at 900°C

Ashing with oxygen

lodometry or ISE

Filtration, drying

Turbidity of white water

Specific conductance'*

Concentration, extraction

Color absorption curve

Microscopy, chemistry

Spectroscopy, etc.

Clark or Bauer-McNett

Britt jar

Paper strip, pH electrode

Chelant (EDTA) titration

Ion chromatography

Mercuric nitrate

Precipitation with Ba^"^

lodometry

Atomic absorption (AA)

ISE with F

Ashing/EDTA titration

Acid soluble/colorimetric

ISE

Polarography

HCl liberation/colorimetry

Kjeldahl digestion

T 413 om-85 (T 240 first)^

UM 496^

T611om-89(UM612)

T 240 om-88

Use with caution!^

T 252 om-90, ionic interference

GPC,

NMR, FTIR, GLC,

etc.

T 442 om-88 is loosely related

T421

om-91,

tedious^

T 665 om-89

T 233 cm-82

261

cm-90

T 252, 435, 509, 667, UM 214

T 699 om-87, T 700 om-87

T 256 cm-85 (UM 254, ISE)

UM 254, (also T 255 om-89)

T 604 cm-85

T 266 om-88

Tappi

62(2):43(1979)

T 247 cm-83

T 434 cm-83 (T 242 cm-83)

Tappi

54(12):2051(1971)

T 438 cm-90

T 493 cm-84

T 418 om-90 (NH3 ISE detect.)

Caliper & density interact T

251

cm-85, 460, 536, 547

Mechanical test

Optical

Usual tests

Wet paper tensile test

Extraction/spectroscopy

Acid-base titration

Copper reduction

Clark's silver method

Nitrogen BET absorption

Optical methods

Alkali solubility

NaOH solubility

Centrifiige/moisture

Headbox, tray, couch bal.

Various

Colorimetric

Reduction/titration

T 541 om-89

T 425

om-91,

T 519 om-91

pages 171-174

T 456 om-87

T204,

FTIR, NMR, GPC, GLC

T 237 om-88

430

om-88 (oxidized starch too)

T 226 cm-86

Dehydration may decrease area

Kajaani device

(Also

232 cm-85)

T 235 cm-85

(10-21%

NaOH)

T 212 om-88

UM256

T 269 pm-85

T 408 om-88, T

601,

T 628

T 419

om-91

(ok for low DS)

T 627; UM 408, 508 by

colorimetry^

MONITORING WET END CHEMISTRY 455

Some newer methods measure scattered light

with the Doppler effect (laser doppler velocimetry)

during electrophoresis to measure the particle

speeds without direct visual observation. These

devices give spectra (Fig. 22-6) of zeta potentials

for various particles in the suspension. Study of

the isolated components under a variety of pH

conditions and their interactions with other com-

ponents should yield a lot of useful information on

practical aspects of wet end chemistry for a given

paper machine.

Fibers are too large to easily measure their

zeta potential. Often the assumption is made that

the zeta potential behavior of fiber fines is the

same as that of the fibers. The validity of this

assumption is an area of controversy. Zeta poten-

tial is useful for determining the cationic demand,

the amount of cation necessary to cause particles

to have a zeta potential of zero.

Problems in zeta potential measurement occur

if the water has a relatively high ionic strength

since heating will occur, which induces convection

currents. Decreasing the applied vohage or

measurement time will be necessary. Samples

must

diluted with a solution of similar inorganic

electrolyte composition to see individual particles.

Samples should be analyzed without undue storage

time,

if possible.

Details of this and other procedures may be

obtained from the manufacturers of these instru-

ments.

Polyelectrolyte titrations

McDermott (1992) gives a good recipe for

polyelectrolyte titrations, sometimes called colloi-

dal titrations. Consider an anionic polymer (A,

usually the potassium salt of polyvinylsulfate) that

is used to titrate a cationic polymer (C) that is a

component of a pulp furnish. The anionic poly-

mer has an affinity for a dye indicator (I, such as

o-toluidine blue):

A + I ?^ AI

At the same time the anionic polymer should have

an even stronger affinity for the cationic polymer

than for the indicator. To increase the stability of

the complex, the titration must be done in solu-

tions of low ionic strength; Lindstrom in Roberts

(1991) gives limiting values of 0.05 MNa^,

0.005

M Ca^+, and

0.0005

M AP+ for this system.

In direct titration methods, the indicator is

added to the solution containing the cationic

polymer. Anionic polymer is added by a buret.

Initially it complexes completely with the cationic

polymer. After the cationic polymer is complexed

Notes for Table 22-1. 1) cm denotes that superior methods have superseded these. Many of these methods

would require adaptation to pulp slurries. 2) High—temperature ashing for fillers requires the use of

gravimetric factors (Unbehend, 1987). For example, CaCOj is recovered as CaO so multiply the ash by 1.785

to convert to filler. Uncalcined clay requires a conversion factor of about 1.15 for constitutional water loss.

ZnS,

1.2;

TiOj,

1.008;

various silicates,

1.05-1.10;

these can be determined by ashing pure samples of filler.

3) Changes in

flocculation

change the turbidity per unit mass; use to spot machine upsets. 4) Measured in

/xmho (backwards ohm) or mS/m; do not directly compare slurries to filtrates. Report as ppm (mg/L). 5) Other

tools for filler qualitative and quantitative analyses include SEM-EDAX, X-ray fluorescence, electron

microprobe, and X-ray diffraction. 6) Inorganic anions can be analyzed by ion chromatography. 7) Several

the

listed methods may have to be modified for wet end solutions. See a major scientific supply catalog for

the many available ISE electrodes and their limitations (CO2, CI2, O2, NH3, F, CI", T, CN', NOj", S^', Ca^^,

Cu^"*",

K^, Na"^, Pb^^). Some electrodes allow indirect determination of other species, like F for

Al.

AA works

for virtually any metal element and has very good sensitivity (below

ppm) and specificity. Ion chromatogra-

phy is another possible method. 5-7) Many of

the

wet chemical methods listed can be done by other methods

if the more complex equipment is not available (as described above).

Other tests have generic interest such as T 620

cm-83.

Analysis of industrial process water; T 656

cm-83.

Measuring, sampling, and analyzing white waters; UM 470, Sulfates, barium, titanium, aluminum, zinc,

calcium, and magnesium

coated paper (qualitative). Carbonates

can be

detected

adding HCl and observing

for bubbles (UM 531). Sulfides can be detected by HCl with smell or darkening of paper saturated with lead

acetate solution. Um 634 is used for oil absorption of bentonite.

456 22. PAPERMAKING CHEMISTRY

with the titrant, excess titrant causes a color

change (from blue to pink) in the indicator.

In an indirect titration to characterize surface

charges of solids, excess anionic polymer is

added, the solution is filtered, and the excess

anionic polymer is back—titrated with another

cationic polymer such as l,5~dimethyl—1—

diazaundecmethylene polymethobromide, hexadi-

methrine bromide (DDPM) (McDermott, 1990)

from a pink to blue endpoint. In a second set of

titrations, DDPM is used to titrate anionic polymer

in the furnish. The original solution can be

filtered of solids and directly titrated to subtract

ionic charges due to water—soluble components.

Net colloidal titrations

Halibisky (1977) developed a method where

the amount of standard cationic and anionic poly-

mer that absorbs onto the headbox furnish is

measured. The amount is measured by titration

with a colorimetric indicator. The ratio of anionic

polymer used to cationic polymer used in these

titrations is known as the colloid titration ratio or

the ionic ratio (CTR). If more anionic polymer is

absorbed than cationic polymer, the ratio is greater

than one and the surfaces presumably have a net

positive charge. Alum causes some interference.

Hubbe (1979) describes a modification of this.

Four titrations are used, titrating the filtered

solution to subtract its effect and titration of the

solids by indirect titration each with anionic and

cationic titrants.

Colloidal titrations have several disadvantag-

es.

It is hard to reproduce the method from

operator to operator without automation of the

system. The endpoint determination is not very

sharp to the unaided eye. The use of a spectro-

scopic instrument to help determine the endpoint

is useful, but adds to the complexity and cost of

the method. Many mill people feel this technique

is best left to research facilities.

Simulating the paper machine in the laboratory

Paper machine production personnel will not

let academics recreationally test ideas when the

costs can be tens of thousands of dollars an hour.

Thus,

any information one can glean from labora-

tory investigations is essential.

The papermaking system can be simulated

off—line with handsheet formation, the Britt jar

test, pilot plant paper machines, or other tools as

appropriate. Handsheet formation has the limita-

tions of very dilute solutions (typically 0.017%

consistency for Tappi Standard handsheets of 60

g/m^ in the British sheet mold), low turbulence

during formation, and air drying of the paper.

Sheet dryers are available, but the sample does not

dry under restraint. Often, all of the chemicals

can be added when the stock is at about 1%

consistency with dilution occurring only during the

sheet forming phase. A higher basis weight sheet

can be formed from lower amounts of water to

increase the consistency.

Static settling tests {jar test) are often used in

the water treatment industry. Various levels of

retention aid are added to stock solution in each of

several beakers. The stock is mixed and allowed

to settle. Materials that promote flocculation will

cause settling more quickly than in the controls.

After a given period of time, the turbidity of the

supernatant is determined.

Because of the low turbulence in the British

sheet mold and jar test, any retention aid that does

not work in the laboratory will not work on the

paper machine; however, the converse is not

necessarily true. One would at least like relative

results, but under static conditions, soft floes may

behave similarly to hard floes.

The application of the Britt jar test to reten-

tion has been discussed. This device allows one to

determine the effect of a wide range of shear

forces and turbulence on retention. It is said that

one should

able to determine first—pass retention

to within 3 or 4%. The stirring time should be

kept relatively short after addition of the additives.

Zunker (1982) described modifications to the

Britt jar that allow it to be used as a drainage

tester. He added vanes (which approximately

doubled the turbulence and decreased the vortex

formation), an electrically activated valve at the

bottom, and the use of vacuum. This apparatus

allowed the measurement of a wide variety of wet

end phenomena.

Water retention value (WRV) has been used

to predict strength and dewatering of pulp on the

paper machine. The technique has been applied to

newsprint by LeBel et al. (1979). The WRV

newsprint pulp was fairly similar to press consis-

tency in commercial newsprint machines. This is

MONITORING WET END CHEMISTRY 457

probably a good routine quality control measure

on a paper machine's thick stock since it is said to

correlate well with paper machine breaks.

The WRV procedure involves centrifuging a

50 mL sample of »3% consistency in a cup with

100 mesh screen at the bottom. The centrifuge is

operated at 840 g (g is acceleration of gravity) for

12 minutes. The moisture content of

the

pad after

centrifugation corresponds to the WRV, which is

a percentage. A procedure is given in UM 256

(900 g for 30 min).

22.8 PAPERMAKING CHEMISTRY

CONTROL

It is always desirable to optimize the perfor-

mance of the wet end. This is particularly true

with expensive paper machines where one desires

to use high speeds but must not suffer web breaks.

Too,

the extremely high cost of many paper-

making additives must not be taken lightly. The

goal is to do more with less, but there are always

tradeoffs. Chapter 20 on total quality management

should be consulted for the implementation of

papermaking chemistry control.

Control implies feedback. Feedback consists

of a few parameters of product quality at the very

minimum. The ideal would be numerous product

quality parameters in addition to the results of a

battery of continuous on—line tests and immediate

access to all mill operating data.

Variability occurs in pulp preparation, stock

refining, raw materials used in the wet end, mill

upsets, and so on and on. Variability must always

be considered! The properties of each additive are

ideally monitored separately to verify that there is

no change from batch to batch. At least some

viscosities and colloidal titrations could be per-

formed. (You say your supplier does that for you

and your supplier never has variation in the mate-

rial sent to you.)

The entire process should be viewed for what

it is, a scientific experiment. The critical step is

the development of a hypothesis; this is, unfortu-

nately, often the last step after analysis of results.

A protocol is established to test the hypothesis, the

determination of the necessary data is made, data

is collected, verification of data collection and

analysis is made, and the hypothesis is determined

to be true or false. New hypotheses usually

present themselves in well—designed experiments.

It is often helpful to make a series of graphs

relating various parameters to each other. These

graphs may show correlations between variables.

The correlations will have to be determined as

direct cause—and—effect or indirect relationships;

this may require additional experiments. (Ciga-

rette manufacturers have long argued that the

correlation between smoking and disease does not

prove cigarettes cause disease; they argue that the

type of people who choose to smoke are predis-

posed to disease.) These graphs also show which

variables are easy to control and which have high

levels of variation or obvious trends.

On—line sensors

On—line sensors are superior to off-line

measurements that take operator time and data is

available immediately to control the process.

Measurements of pH, conductivity, temperature,

flow

rates,

zeta potential, certain ions, and flow

rates are well established and do not require

operator time to collect. Flow rates are deter-

mined with ultrasonic Doppler (reflective for

solutions containing particles or bubbles or clamp-

on for solutions) or magnetic devices. On—line

sensors should be routinely calibrated.

Kortelainen (1992) discusses on—line sensors.

Off-line sensors

Off—line sensors usually require manual sam-

pling of process streams. It is critical to obtain a

representative sample. This is not easy in the case

of paper machine white water; in this case sam-

pling of more than one region may be required,

and each sample must be representative of

the

area

from which it is collected. A small study needs to

be done just to determine that a representative

sample is being obtained. Samples are generally

collected with equal time intervals between them.

Grab samples are generally useful only if the

process is in control (operating under near steady-

state conditions).

Flow rates can be measured by bucket and

stopwatch, chemical dilution

(TIS

0410-09, the old

018-3),

and flow balance methods.

Material balance of a paper machine wet end

One can monitor a particular flow (perhaps

458 22. PAPERMAKING CHEMISTRY

tray 1 white water) for routine quality control of

drainage. If new drainage aids are used, however,

one will want to do a complete balance around the

paper machine to determine where drainage is

occurring. The reason is that drainage aids work

by different mechanisms and affect components of

drainage differently. As already mentioned,

improved drainage at the flat boxes does not mean

the consistency at the couch will be improved.

Complete balances can be solved with com-

puter—based steady—state balance programs such

as GEMS or MAPPS if the data is available.

Problems and errors in material balances (such as

first—pass ash retention) occur because small

variations is headbox and tray consistencies and

ash content determinations are amplified in the

calculations. Digital analytical balances with a

precision of 1 mg or (preferably) 0.1 mg should

be used in solids determinations where the weights

(with tared vessels) are below 100 grams. (Solu-

tion volumes over 100 mL are easily measured by

weight with a precision of 0.01 g.)

22.9 OTHER CONSIDERATIONS

Wood

pitch

Pitch has been discussed on page 264. Pulp

mills that use nonalkaline processes often have

trouble with wood pitch. Wood pitch consists of

over 50% saponifiable materials that are hydro-

lyzed and solubilized under strongly alkaline

conditions. Pitch is usually anionic if it has any

charge and may contribute to anionic trash.

Calcium ions form precipitates with wood pitch.

Wood pitch is concentrated in parenchyma

cells and may be squeezed out in refining, paper

pressing, and other operations. Pitch may contrib-

ute to foam formation when the pitch molecules

attach to air bubbles. Wood pitch in bleached

sulfite pulps may be relatively abundant and of

high molecular weight. Analytical techniques for

pitch analysis are considered elsewhere (p. 434).

Cationic retention aids such as alum may help

bind wood and other pitch materials to the stock to

prevent their concentration in the system. Pitch

may be absorbed on talc if the pitch is dispersed.

Dispersants are used to keep the pitch from form-

ing aggregates, but may contribute to poor reten-

tion and foaming.

Foam

In addition to surfactants, finely divided

solids can contribute to foam problems. These

solids include fillers, alumina, fines, and other

colloids that can surround air bubbles to decrease

the surface tension. Because of their high surface

areas,

foams are thermodynamically unstable, but

may be quite stable kinetically.

Dyes

Basic dyes, unlike other dyes, are soluble in

moderately polar to nonpolar materials like the

lower alcohols and oil. They have a tendency to

work unevenly and may give a surface that ap-

pears somewhat like granite.

Because titanium dioxide and many fillers

absorb or reflect UV light, they mitigate the effect

of fluorescent brightening agents. Light color

shades tend to be direct dyes, while deep colors

tend to be basic dyes. Biocides in the white

water, such as chlorine compounds, may oxidize

dyes to change (bleach) their colors. Like phenol-

phthalein, many dyes are pH sensitive.

Refining

The level of refining can be followed with

Simons (1950) stain (TAPPI UM 17) of fibers

observed through a microscope. Even without

staining, refining can be followed qualitatively

with microscopic observation. Pulps with low

cellulose viscosity refine faster, so the refiner

operator should be aware of changes in the pulp

viscosity.

Areas of more research

The areas of colloid chemistry and electro-

chemistry are very important to papermaking

chemistry, as is coordinate chemistry, but these

areas do not receive the attention they deserve.

One area of research is the use of di— or triblock

polymers with affinities for different components

the

furnish. This would be useful, for example,

for allowing fillers to attach directly to fiber (with

the improvement in opacity mentioned above),

although one cannot help wondering what this may

do to the strength properties of the paper.

Battan (1995) shows that ammonium salts of

partially saponified styrene—maleic anhydride

copolymers are better at surface sizing than sodi-

OTHER CONSIDERATIONS 459

um salts. He attributes this to the fact that ammo-

nia is removed in the dryer section, leaving the

carboxylic acid to coordinate with cationic species

in the paper. Some rosin formulations use ammo-

nium salts.

Additional comments on internal sizing

It is interesting to consider that hydrolyzed

ASA (Hodgson, 1994) and unreacted rosin are

surfactants which, as shown by Chen and

Biermann (1993) and others, lower the level of

sizing. Therefore, using additional ASA or rosin

to try to improve sizing may have the opposite

effect.

Shimada (1996) ivestigated the use of various

carboxylic acids (in small amounts of ethanol to

help disperse them in water) with alum in the

sizing of laboratory handsheets. He found that

primary fatty acids gave good sizing when the

chain length was 12—18 carbon atoms with stearic

acid giving the best results. Larger fatty acids

gave poor results. Rosin gave better results than

stearic acid presumably because it is locked into

shape instead of having a chain that can coil to

various degrees. Oleic acid was not as useful as

stearic acid against formic acid ink because the cis

carbon—carbon double bond kinks the hydrocar-

bon tail giving a less dense surface (Shaw, 1980,

in the previous chapter).

A six carbon isocyanate gave no sizing while

an 18 carbon isocyanate was better than stearic

acid showing that a well bound six carbon moiety

does not impart sizing.

Some

parting thoughts

There are too many hard and fast rules in

alkaline papermaking chemistry. There are so

many variables in fiber types, filler types, poly-

mers among various manufacturers, and so forth.

Only with detailed characterization is it possible

that the effects (and intereffects) of all of these

parameters can be sorted out at least empirically if

not theoretically.

Therefore, authors of publications must

characterize their polymers and other additives to

as high a degree as possible. It is necessary for

papermakers to have detailed specifications of the

products of various manufactures to really be able

to maximize the attributes of their paper and paper

machine; however, manufacturers may have a

different point of view. A comprehensive, indus-

try—wide survey of who is doing what, and with

what additives, would be one of the most produc-

tive undertakings to advance papermaking chemis-

try to the level it should be at. This would include

a detailed chemical characterization of the addi-

tives (with or without the help of the manufactur-

ers).

It is unfortunate that the industry takes the

attitude that the supplier will solve all of their

problems. Suppliers sell complete systems that

were optimized in their laboratories or on some-

one else's machine at some other time. There is

no reason to assume their particular system is

optimized for your product on your machine using

your pulp.

We have not even touched on the possible

effect of molecular weight distribution (see Chap-

ter 18). Most papermaking polymers are made by

free radical polymerization techniques. This

means that a given molecular weight, without

describing the method used to determine it, is mis-

leading. A great deal more care must be paid to

detail in the papermaking chemistry literature.

I especially welcome conmients, suggestions,

pointing out of erroneous statements, and other

correspondence from the reader in this area.

22.10 AlSfNOTATED BIBLIOGRAPHY

In addition to the references below. Vol. 8,

No.

1 (1993) Nordic Pulp and Paper Research

Journal contains 40 of the 70 papers presented at

the June, 1992 Paper and Coating Chemistry

Symposium, Stockholm, in the areas of polymer

adsorption, interactions at interfaces, flocculation,

rheology, and applied paper chemistry (234 pag-

es).

There is a lot of new work and ideas in this

reference, but it is overwhelming on the first read-

ing. Similarly, Vol. 4, No. 2 (1989) issue includ-

ed 17 of the 37 papers of the September, 1988,

Paper Chemistry Symposium, Stockholm.

Battan, G.L., The effects of SMA surface

sizes on paper end—use properties,

Tappi

78(1):

142-146(1995).

Biermann, C.J., Rosin sizing with polyamine

mordants from pH 3 to 10, Tappi /.,

460

22.

PAPERMAKING CHEMISTRY

75(5):

166-171(1992).

See Subrahmanyam,

S. and C.J. Biermami, Generalized rosin

soap sizing with coordinating elements, Tappi

75(3):223-228 for the role of coordinate

chemistry in aluminum and papermaking

chemistry.

Britt, K.W., Mechanisms of retention during

paper formation, Tappi 56(10):46-50(1973).

This paper describes Britt's dynamic reten-

tion jar and its application to retention studies

with several cationic polymers.

Britt, K.W. and J.E. Unbehend, Electropho-

resis in paper stock suspensions as measured

by mass transport analysis, Tappi 57(12):81-

84(1974).

Campbell, W.B., Pulp Paper Mag. Can

38(2):

189(1937);

48(2):

104(1947);

Paper

Trade J. 95(8):29(1932). Campbell worked

out much of the theory on drainage and

forces developed between fibers. In Canadi-

an Dept. Interior, Forest Service Bull.

84(1933), he points out that the capillary

forces between fibers of 30 ptm diameter is

87 psi; of fibrils 3 jitm in diameter, 540 psi;

and of 0.3 iim fibrils, 2480 psi.

6. Campbell, W.B., The physics of water re-

moval. Pulp Paper Res. Can. 103-109, 122,

Convention Issue, 1947. One of the earliest

looks at filtration of water in the forming

web.

This work also includes water removal

by compression of the fiber mat (pressing).

Carman, Trans. Inst. Chem. Eng. (London),

15:150(1937).

8. Chen, M. and C. J. Biermann, Investigation

of the mechanism of paper sizing through a

desizing approach, Tappi J.

78(8):

120-

126(1995). A variety of inks containing

surfactants, acid, and aluminum complexing

species such as fluoride were used to test the

chemical properties of size anchoring bonds

of rosin—alum and AKD size. Rosin sizing

behaved as a coordinate bond through alumi-

num, and AKD behaved as a direct bond.

Calcium carbonate papers should not be

tested with inks containing formic acid. A

surfactant may be used to accelerate testing.

9. Davison, R.W., The sizing of paper, Tappi

58(3):48-57(1975); this has 94 references.

10.

Dean, A., Lange's Hajidbook of Chemistry

and Physics, 13th ed., McGraw-Hill, New

York, 1985, Chapter 5.

11.

Dixit, M.K., C.W. Jackowski, and T.A.

Maleike, Retention strategies for alkaline

fine papermaking with secondary fiber at

Appleton Papers, Inc., West Carrollton,

Ohio;

a case review, TAPPI 1991 Paper-

maker's Conference, 5 p. (Reprinted in

Alkaline Papermaking 1982-1992, TAPPI

Anthology, pp. 13-18.)

12.

Forsberg, S. and G. Strom, The effect of

contact time between cationic polymers and

furnish on retention and drainage, J. Pulp

Paper

Sci.

20(3):J71-J76(1994). The authors

present data indicating that maximum reten-

tion usually occurs when cationic polyacryl-

amide or starch is added 10-20 seconds

before drainage. Longer contact times de-

crease retention and drainage rates.

13.

Gess, J.M., The measurement of sizing in

paper, Tappi 64(1):35-39(1981). This paper

compares several sizing methods and the use

of different sizing test solutions.

14.

Halibisky, D.D., Wet—end control for the

effective use of cationic starch, Tappi

60(12):

125-127(1977).

15.

Hodgson, K.T., A review of paper sizing

using alkyl ketene dimer versus alkenyl

succinic anhydride, Appita 27(5):402-406

(1994).

This is a very useful review and

comparison of the two sizing methods.

16.

Horie, D. and C.J. Biermann, The applica-

tion of durable press treatment to bleached

softwood kraft handsheets, Tappi J.

77(8):

135-140(1994).

ANNOTATED BIBLIOGRAPHY 461

17.

Hubbe, M.A., A modified reporting proce-

dure for polyelectrolyte titrations, Tappi

62(8):

120-121(1979).

18.

Ingmanson, W.L., et al., Tappi 37(11):523-

534(1954); 42(6)-.449-454(1959); 42(10)840-

849(1959);

46(3):

150-155(1963).

This work

investigates drainage in terms of filtration

theory.

19.

Koethe, J.L and W.E. Scott, Polyelectrolyte

interactions with papermaking fibers: the

mechanism of surface—charge decay, Tappi

76(12):

123-133(1993).

The authors con-

tend that cationic polymers have a decreasing

effect on zeta potential with time as they

diffuse into the fibers; therefore, high mo-

lecular weight polymers are more effective at

having a sustained effect with relatively long

periods of time.

20.

Kortelainen, H., Tools for successful wet-

end chemistry control, Tappi J.

75(12):

112-

117(1992). The author describes on—line

sensors of interest to wet end chemistry and

suggests a control system (38 references).

21.

LeBel, R.G., G.C. Nobleza, and R. Paquet,

Water retention value indicates machine

runnability of pulp, Pulp Paper Can.

80(5):T135-T140(1979).

22.

Linke, W.F., Polyacrylamide as a stock addi-

tive,

ra/7;7/45(4):326-333(1962). This useful

paper describes the effect of PAM on the

papermaking process.

23.

McDermott, D., Wet end starch, alum,

anionic retention aids used in alkaline

papermaking, 1990 TAPPI Neutral—Alkaline

Papermaking Short Course Notes, 9 p.

Reprinted in Alkaline Papermaking 1982-

1992,

TAPPI Anthology, pp 304-312.

24.

Nissan, A.H., Tappi 37:640(1954).

25.

Parker, J.D., The sheet forming process,

Monograph No. 9, 1972, TAPPI Press,

Atlanta.

26.

Ranee, H.F., Ed., Handbook of Paper Sci-

ence, Elsevier, Amsterdam, Vol. 1, 298 p.,

1980;

Vol. 2, 288 p., 1982. This is a funda-

mental review of the paper physics literature

that is very well referenced and easy to read.

Many of the topics are directly or indirectly

. related to papermaking physics. Volume 1

chapter titles are Cellulose—water interac-

tions.

The fibrous raw materials of paper.

Preparation of pulp fibres for papermaking,

Forming the web of paper, and Consolidation

of the paper web; Vol. 2 titles are The

porosity of paper (including transport proper-

ties).

Mechanical properties of paper. Optical

properties of paper, and The structure of

paper.

27.

Reynolds, W.F., New aspects of internal

bonding strength of paper, Tappi

57(3):

116-

120(1974). This includes a lot of well-

graphed experimental results (no references).

28.

Roberts, J.C, Ed., Paper Chemistry,

Blackie, London, 1991, 234 p. This work

gives details of papermaking additives, chem-

istry, and control.

29.

Shimada, K., Unpublished data, 1996.

30.

Simons, F.L., A stain for use in microscopy

of beaten fibers, Tappi 33(7):312-314(1950).

Two aniline dyes, direct blue and direct

orange, have differential affinity for cellulose

fibers with beaten pulp turning orange and

unbeaten pulp turning blue. This method

was used by Blanchette et al. in their study

of biomechanical pulps

[Tappi

75(11):

121-

124(1992) with four color photographs.]

31.

Stratton, R.A. and J.W. Swanson, Electro-

kinetics in papermaking, Tappi 64(1):79-

83(1981). This is a useful paper for people

thinking about using zeta potential for control

of their paper machine.

32.

Tanaka, H., P. Luner, and W. Cote, How

retention aids change the distribution of filler

in paper, Tappi 65(4):95-99(1982).

33.

Tanaka, H., A. Awerin, and L. Odberg,

462 22. PAPERMAKING CHEMISTRY

transfer of cationic retention aid from fibers

to fine particles and cleavage of polymer

chains under wet—end papermaking condi-

tions,

Tappi

76(5):

157-163(1993). Also see

Forsberg and Strom (1994).

34.

Unbehend, J.E., Mechanism of "soft" and

"hard" floe formation in dynamic retention

measurement, Tappi 59(10):74-77(1976).

This paper demonstrates laboratory retention

with varying turbulence using retention

systems of metallic ions with varying valenc-

es,

low and high molecular weight cation-

ic polymers,

and

high molecular weight poly-

mers with and without disruptive turbulence

before drainage.

35.

Unbehend, J., Introduction to Wet—end

Chemistry, Home Study Library Vol. 14,

1987, TAPPI Press, Atlanta. This is a useful

introduction with well—referenced text (79

pages) of tables and figures and accompany-

ing audiotapes. It contains very little infor-

mation since 1982, which makes it dated in

the area of

alkaline

papermaking. The author

is not unbiased regarding the equipment he

sells.

36.

Washburn,

283(1921).

E.W., Phys. Rev, 17:273-

37.

Weisgerber, C.A., Ketene dimer sizing

composition and process for sizing paper

therwith. U.S. Patent 2,865,743 (1958).

38.

Williams, M., An alkaline experience at

Boise Cascade—Wallula, TAPPI 1991

Papermakers

Conf.,

2 p.

39.

Zhuang, J. and C.J. Biermann, Rosin soap

sizing with ferrous and ferric ions as mor-

dants,

Tappi J,

76(12):

141-147(1993). The

title ions were exceedingly effective in sizing

mechanical

pulps with rosin

(though the paper

40.

darkened) while they were completely

inef-

fective at sizing bleached chemical pulps.

Zunker, D.W., 1982 TAPPI Papermakers

Conference

Proceedings,

pp 197-204.

EXERCISES

Why would CTMP pulp produced with

sulfite be expected to behave differently than

TMP pulp in terms of papermaking chemis-

try?

What are the advantages of high first pass

retention levels? Give at least three advan-

tages.

A particular papermaking polymer has a very

high cationic charge even at pH approaching

11.

What functional group probably makes

this material cationic?

Why do fines require more wet end additives

than fibers?

5. One is using a dual polymer retention sys-

tem.

What is the concern over high levels of

hydrodynamic shear?

6. How would one prove or disprove the hy-

pothesis that formic acid decreases the sur-

face tension of water as its principlal means

of lowering HST values relative to neutral

ink?

7. Why is surface sizing used even in papers

with internal sizing? Why is internal sizing

used in papers with surface sizing?

8. Why are high molecular weight polymers

required in high—speed paper machines for

retention?

PRINTING AND THE GRAPHIC ARTS

23.1 INTRODUCTION

Papermakers must serve their customers and

know about their processes. Printing is one major

use of paper. Also, many paper converting op-

erations include printing.

International Paper (1983) is a useful (but

somewhat dated) reference on printing and provid-

ed some of the information included in this chap-

ter, although a 1989 edition exists. Glassman

(1985) is another excellent source of information.

In 1990, there were over 60,000 printing and

publishing establishments with 1.54 million em-

ployees of whom 818,000 were production work-

ers.

The annual payroll was $38.8 billion. The

total value of the publications was $157 billion.

Almost two—thirds of this was value added, a

very high ratio for any industry.

Historical context

Printing is often defined as "the use of ink to

transfer an image on a substrate such as paper"; it

implies the generation of a "large" number of

reproductions. The term "printing" was synon-

ymous for the letterpress method, which was

predominant until about 1940; now very little

letterpress printing is practiced. The use of

computers and instrumentation to generate material

must modify these traditional definitions and

implications.

Early letterpress plates were prepared by

carving wood plates corresponding to entire pages,

and these were of no use once the printing was

complete. The invention of movable type in the

western world is credited to Johannes Gutenberg

in Mainz, Germany in 1455; but a primitive

movable type made from metal was used in Korea,

China, and Japan several hundred years earlier.

Movable type consisted of individual letters

and characters that could be arranged to form an

individual line. Once a mold was made for a

particular letter, it could be filled with lead to give

the letter, cooled and separated, and filled again;

in this manner individual characters could be mass

produced. Lines of type were assembled to give

a page. When the printing job was completed, the

characters could easily be recovered for reuse.

The invention of Gutenberg's movable type was of

paramount importance to the development of

civilization, as the availability of printed material

increased by several orders of magnitude within a

relatively short period of time.

Another major advance was the invention of

linotype machines by Ottmar Mergenthaler, which

appeared in 1886. These machines automatically

assemble lines of tvpe as the characters are typed

in at a keyboard. Typesetting was common until

the late 1960s. The Linotype—Hell Company

licenses many fonts used in printing including

some used in computer printers.

Introduction

The various methods of printing high num-

bers of reproductions center on the plate which

carries the image to be printed. Plates may carry

type (text), pictures, or both (the copy material).

The purpose of the plate is to transfer the ink

(from the ink—fountain) in the form of an image

to the paper (perhaps through a blanket) to give a

clear copy of the image of interest. Three possi-

ble geometries are available and define the basic

processes (Fig. 23-1) of

letterpress,

raised printing

surface; lithography, printing and nonprinting

surfaces that are in the same plane; and gravure

(recessed printing surface). The fourth main

geometry is used in screen printing, which uses a

stencil or porous plate.

When an image is transferred by direct con-

tact, the image on the plate must be a mirror

image of the desired result. If one ink transfer is

used, the plate uses a positive image.

Many advances in printing have caused

conmion terms to be redefined. While the defini-

tion of the term was apparent at one time, the

present definition is not necessarily straightfor-

ward. A good example of this is the term ojfset.

When letterpress printing was common, offset

referred to the undesirable transfer of ink to the

blanket. In the early 1900s, it was found by

accident that when offset came in contact with

paper, a superior unage was produced. With that

463