Biermann Ch. Handbook of Pulping and Papermaking

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254 9. PAPER MANUFACTURE

electrical resistance. Thermoplastic resins are

used to make tough, flexible papers used in mask-

ing tape, book covers, artificial leather, etc.

Lamination

Lamination is the combination of two or

more films or sheets of paper, normally held

together with adhesives, to make a composite.

Corrugated

boxboard production

Box production is almost always done in

operations (called box plants) away from the paper

mill since paper mills tend to be located in rural

areas with large amoimts of wood, whereas boxes

are used in metropolitan areas with high popula-

tions.

Furthermore, corrugated boxes are neces-

sarily bulky and do not transport efficiently.

About 450,000 tons per year of cornstarch is

used as corrugated box adhesive alone in the U.S.

Cornstarch is treated with metaborate (formed by

the action of caustic on borax) to obtain the adhe-

sive for corrugated boxboard. It is important that

the viscosity of the starch-metaborate solution not

be allowed to increase too much during starch

cooking.

9.12 COATING

Coating

Coating is the treatment or application of

pigments, polymers, or other materials to one or

both surfaces of paper. Coating can be applied

on-machine or off-machine. On-machine coating

has the obvious advantages associated with de-

creased handling of the paper. Off-machine has

the advantages of providing greater flexibility in

the system including the speed of coating.

About 20% of paper is coated. Coating

improves brightness, gloss, smoothness, caliper,

and uniformity of the base paper. Coating also

improves many aspects of the printing process.

Improvements in printing are improved gloss of

the ink film (ink holdout), freedom from mottling

(uniform absorption of ink), improved resolution

of printed images, improved contrast due to ink

holdout, and decreased show-through since the ink

remains on the surface.

Fig. 9-67 shows scanning electron micro-

graphs from a base sheet at low magnification and

four types of coating papers, applied to the same

base sheet, at very high magnification. Coatings

that have high gloss must be smooth relative to the

wavelength of light (about 0.5 fim). The center

picture is at low magnification and is from the

base sheet. Its surface is quite rough compared to

the coated samples. The upper left micrograph is

from a matte coated paper (similar to the paper

used in this book) that has little gloss. The upper

right micrograph is from a dull coated paper that

has some gloss. The lower left micrograph is

from a gloss coated paper that typical of high

quality magazines. The lower right micrograph is

from a cast coated paper (machine glazed with a

Yankee dryer) that would be used in the highest

quality magazines and annual reports of large

companies. As the surface becomes more uniform

(on a jLtm scale), the gloss increases.

Coalers

Coatings are applied at the size press or with

a roll coater (Fig. 9-68), air knife, or, the most

common method, blade coater (Fig. 9-69). Coat-

ing speeds are 3000-4000 ft/min for lightweight

papers and 1200-1300 for board materials.

Coating with transfer roll coalers has the

advantages of giving an even coat weight, even

when the surface of the base sheet is somewhat

rough. It is used at speeds of 600 m/min (2000

ft/min), with high solid content coatings with high

viscosity. These coaters have low maintenance.

The disadvantages are the large space require-

ments, film splitting, high installation costs, and

the requirements of numerous adjustments. Coat-

ing weights are limited to about 10 g/m^, although

two layers are used sometimes. Reverse roll

coaters have a lower speed rate, about 50% of

other roll coaters.

Coating with an air knife has the advantages

of giving an even coat weight, being able to use

high coat

weights,

not leaving scratches, and being

versatile. These coaters have several disadvantag-

es.

They can only be used with coatings con-

taining low solid contents and having low viscosi-

ties,

they must be used at relatively low speeds

around 500 m/min (1500 ft/min), and they may

cause streaking and patterning.

Blade coaters offer the advantages of low

cost, the ability to coat two sides at once, and

COATING 255

^ •

ih^M:W^

fe'cS.^- ^•*^.

Fig. 9-67. Uncoated base paper (center), matte coated (top left), duU coated (top right), gloss

coated (bottom left), and cast coated (bottom right) papers.

256

PAPER MANUFACTURE

?S Hot Air

Coating Distributor

^ ^

<^-^£S

Oscillating

Doctor

^Xi) —-—...^_@ B!^

Coating Distributor

\^ ^ fl*%.

Oscillating

Doctor

A Schematic Diagram of tlie Faeber Coater

, Hot Air

Metering Roll

Application

Roll,

Top

Application

Roll,

Bottom

Distributing Roll

Meterinq Roll

B Double Roll Coater Showing

Simultaneous Coating of Both Sides

Cleaning Doctor/

Metering

Roll/

Puddle

Edge

Applicator

Roll

Application* or

Offset Roll

Two-side Gravure Coater

D Three-roll Nip-fed Reverse Roll Coater

Crown Zellerbach Corp., with permission.

COATING

257

Rotating

Rod to

Clean Backup Rolf

Blade

Jaw

Overflow

A Rotating

Rod

Coater

for

Paper

B Inverted Blade Coater with Multi-roll Applicator

Blade

Pneumatic

Tube

Suction Apron

Slot Lips

Air Doctor

To Dryer

Plenum

Chamber

Baffling

and

Return System

Coating

Head

D Diagram

of the Air

Doctor Coating Process

C Flexible Coater

B and C, are

Trailing Blade Coaters

Fig. 9-69. Four variations of blade coaters. Reprinted from Making Pulp and

Paper^

®1967 Crown

Zellerbach Corp., with permission.

adaptability to on-machine coating. The disad-

vantages include an orange peel surface on the

product, low speeds, the use of coatings with low

solids and viscosity, and low coating levels.

Coating

components

The coating usually consists of three catego-

ries of

compounds.

The pigment, the binder, and

additives. Pigments are materials such as clay,

calcium carbonate, titanium dioxide (the previous

three materials are described in Section 8.4 as

fillers),

silicas, and other materials. The binders

are classified as natural binders or synthetic

bind-

ers.

The natural binders include starch, carboxyl-

ated soy protein, and casein, a white milk protein

containing phosphorus, which was the mainstay

before 1955. Starch may be treated in one of a

variety of methods to give a binder. These modi-

fications include oxidation to give carboxylic acid

groups, addition of amines to make it cationic,

partial hydroxyethylation, or cyanoethylation.

Synthetic binders include styrene-butadiene rubber

(SBR) latex, polyvinylacetate latex, or vinyl-

acrylic latex. (Latexes are defined below.) SBR

is usually carboxylated and must be used with a

tackifier to make it less sticky. Crosslinking

agents such as melamine-formaldehyde, glyoxal-

based resins, and, especially for the synthetic

binders, ammonium zirconium acetate.

Latex

A latex is a water emulsion of a synthetic

258

9. PAPER MANUFACTURE

polymer (rubber or plastic). Latexes are used in

paints, and many coatings are really much like

paints. An emulsion is a suspension of mutually

insoluble materials. One of the materials is

dispersed as small droplets throughout the other.

Milk is an emulsion of fat and in water.

Drying of

coatings

The coating is dried by electrical or gas

infrared dryers (with heat transfer by radiation),

convection dryers, or conduction dryers (with heat

transfer by hot air impingement). Infra-red dryers

are usually gas fired, although electric heaters are

used occasionally. Hot air impingement uses

hoods containing air moving at high velocities.

Printing

coating

A printing coating consists primarily of a

pigment (clay, Ti02, CaCOj, etc.) and a binder

(starch, protein, synthetic resin, etc.) and is de-

signed to impart a good printing surface to the

paper. Printing coatings are used for slick mag-

azines because of the high gloss and high quality

printing reproduction imparted to the paper.

Decorative

coating

A decorative coating is applied mainly for the

sake of appearance or to act as a base for printing.

Some examples are decorative wrapping papers

and coated magazine and book stock.

Functional coatings

and other

coatings

Functional coatings are designed as barriers

to liquids and vapors such as for frozen food

containers. Often, pure polymers such as polyeth-

ylene are used to make laminates, milk cartons,

etc.

Other coatings are used to generate images

such as in photographic papers, carbon paper, or

carbonless papers (NCR or 3M).

operating parameter; how to get it and how

to keep it. Pulp Paper Can. 92(12):87-100

(1991).

This reference includes a separate

three page commentary by G.P. Chinn.

Dewatering

Hansen, V.E., Water management for the

wet end, 1991 Wet End Operations Short

Course, TAPPI Press, pp 131-192. This is

an excellent, highly detailed resource with

numerous photographs of paper machines.

This article must be in the library of anyone

responsible for dewatering at the wet end of

flat wire machines. The TAPPI copyright

figures on dewatering elements presented in

this chapter was from this article through the

courtesy of the author.

Burkhard, G. and P.E. Wrist, Investigation

of high speed paper machine drainage phe-

nomena. Pulp Paper Mag, Can.

57(4):

100-

118(1956). This is the landmark paper that

introduced foils.

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

TAPPI STAP No. 9, 104 p. (1972). This

monograph with 140 references describes

wet-process sheet formation from a dilute

fiber suspension as a ftmction of drainage,

oriented shear, and turbulence.

Headbox

design

6. Waller, M.H., Recent developments in

headboxes,

TappiJ.

70(l):33-42. (A similar

paper is

ibid.,

Twin-wire headboxes, TAPPI

Notes 1989 Twin-Wire Seminar pp 17-28.)

This excellent article is a 10-year survey of

headbox development with pictorial examples

from several suppliers.

9.13 ANNOTATED BIBLIOGRAPHY

Introduction

Ely, D.A., How to rate your paper machine

and mill performance, competitiveness. Pulp

& Paper 55(9):89-93(1981).

Newcombe, D., Demanding customers have

meant dramatic changes in headboxes, PIMA

69(10):27-34(1987). No references. The

historical development of the headbox and

present limitations of the headbox are chron-

icled here.

Mardon, J., R. Vyse, and D. Ely, Paper

machine efficiency: The most important

8. TAPPI TIS 0410-02, -03, and -04 (1988).

These are 4, 4, and 3 pages, respectively.

ANNOTATED BffiLIOGRAPHY 259

These information sheets mathematically

describe the flow from headboxes with verti-

cal, 45° angle, and nozzle with inclined

upper lip slices, respectively.

9. TIS 0410-06, Headbox piping system-gener-

al design guide. 6 p.

Forming fabrics

10.

Kobayashi, T., Latest

trend

of forming fabric

for PM, Japan Pulp Paper 27(4):73-

87(1990). This article, with numerous elec-

tron micrographs, discusses new forming

fabrics including 2 and 2.5 layer fabrics.

11.

These three references appear consecutively

in TAPPI Seminar Notes, 1989 Wet End

Operations, Fliss, T., Forming fabric design

fundamentals, pp

lOH-lll,

12.

Pitt, R. and E.M. Cordon, Wear of forming

fabrics, TAPPI Seminar Notes, 1989

Wet End

Operations

pp 229-236.

13.

Givin, W.R., Understanding fabrics through

computer technology,

TAPPI Seminar

Notes,

1989

Wet

End

Operations

pp 237-248.

Fourdrinier paper

machine

14.

Kennedy, W.H. and P.E. Wrist, The

fourdrinier

paper

machine,

in Pulp and Paper

Science and

Technology,

Volume 2, Libby,

C.E., Ed. McGraw-Hill, New York, 1962,

pp 163-208.

This chapter covers fundamental aspects of

the wet end including flow of

fiber

slurries in

circular pipes, stock distribution to the

headbox, headbox operation, slices, slice

velocities as a function of geometry, fiber

orientation, suction profiles of

table

rolls and

drainage foils, sheet formation, sheet two

sidedness, and a flow balance exercise.

15.

Strauss, R.W., Papermaking machines; the

fourdrinier, in

Pulp

and Paper

Manufacture,

Volume 3, MacDonald, R.G., Ed., McGraw-

Hill, New York, 1969, pp 245-297. A

similar type of article to the preceding one.

with many identical figures, but including

more history of the paper machine and the

twin wire formers.

16.

TAPPI TIS 0410-07 (1988), Evaluating the

drainage performance of a fourdrinier. 4 p.

17.

TIS 0410-08 (1968), Control of stock jump

on a fourdrinier wire. 3 p. This is a dated

discussion with table rolls.

Twin

wire

machines

18.

Thorp, B.A., Fundamental and commercial

overview of twin wire and multiple wire

forming, TAPPI Notes 1989

Twin-Wire

Semi-

nar, pp 1-15 (the identical article, on glossy

coated paper, is found in Tappi Notes 1989

Wet End Operations Seminar pp 191-206).

This is an extremely useful overview of twin

wire machines. Several other articles from

the

twin wire

seminar also describe twin wire

machines, but with a lot of repetition. The

entire notes are 147 pages.

19.

Baker, D.E., and K.N. Riemer, Twin-wire

gap forming: leading edge technology for

newsprint in the 90s, Pulp Paper Can,

93(6):T170-T175(1992).

Many diagrams

and

a recent list of startups are included.

20.

Sinkey, J.D. and D. Wahren, Quality com-

parisons of twin-wire and fourdrinier papers,

Tappi J.

68(9):

110-114(1986). This paper,

with 60 references, discusses the advantages

of paper made on twin wire machines, com-

pared

to paper

made on fourdrinier machines,

including improved formation, smoothness,

basis weight, and moisture profiles; reduced

two-sidedness and linting; and somewhat

higher porosity.

Multi-ply formers,

cylinder machine

21.

Nutter, J.C, Papermaking machines; cylin-

der, in

Pulp

and Paper

Manufacture,

Volume

MacDonald, R.G., Ed., McGraw-Hill,

New York, 1969, pp 297-365. This is a

detailed chapter on the equipment and opera-

tion of the cylinder wet end.

260 9. PAPER MANUFACTURE

22.

Anon., Pulp & Paper 52(14):89-104 (Dec,

1978).

"Within the last 13 years, machine

producers have introduced 20 new types of

multi-ply formers." This is perhaps the best

starting point on the subject of twin wire

formers and multi-ply board forming.

Pressing, press felts, dewatering

23.

Wahlstrom, B., A long term study of water

removal and moisture distribution

a news-

print machine press section, Part I, Pulp

Pap,

Mag. Can, 61(8):T379-T401(1960);

/Wd.,Partn, 61(9):T418-T451(1960). The

author won the 1992 TAPPI Gunnar

Nicholson Gold Medal largely for this classic

work on pressing.

24.

Busker, L.H., The effects of wet pressing on

paper quality, TAPPI

Seminar

Notes, 1985

Practical

Aspects

Pressing and

Drying,

83-95.

Wet pressing has an effect on the

final sheet density and fiber bonding, so

numerous sheet properties are affected by it.

Also,

movement of fines, sheet crushing,

consolidation,

and

felt

marking are

discussed.

The response to wet pressing is very depen-

dent on the furnish.

25.

Lewyta, J. and P. Geoghegan, Recent devel-

opments

in paper

machine clothing: wet felts,

Tappi J. 70(4):57-62(1987). A historical

look at wet felts is given. Many photographs

show the construction of modern wet felts.

26.

The next four papers are more technical

aspects of press felts.

Ballard, J., Press felt characterization,

Tappi

J. 70(7):57-61(1987).

27.

Beck, D.A., Re-examining wet pressing

fundamentals: a look inside the nip using

dynamic measurement, Tappi J.

70(4):

129-

133(1987).

28.

Jaavidaan, Y., W.H Ceckler, and E.V.

Thompson, Re-wetting in the expansion side

of press nips,

Tappi

71(3):

151-155(1988).

29.

Fekete, E.Z., The importance of felt

dewatering,

Tappi

69(12):

147-148(1986).

30.

Reese, R.A., Linerboard survey shows that

drying rates drop as press loading rises. Am,

Papermaker

54(4):42-43(1991). The results

of a survey indicate that as press loading in-

creases the rate of water removal in the dryer

section decreases.

31.

TIS 0404-01 (1983), Determination of water

removal by wet presses. There are about 10

other TIS references on pressing, press felts,

wet felt void volumes, etc. that are of related

interest.

Suction

roll shells

32.

TIS 0402-10 (1985), Guide for evaluation of

paper machine suction roll shells. This is an

extensive reference of 15 pages on the title

topic.

33.

TIS 0402-11 (1987), Liquid dye penetrant

testing of new suction roll shells. 4 p.

Drying

34.

Coveney, D.B. and G.A. Robb, in Pulp and

Paper

Manufacture,

Vol. 3, MacDonald,

R.G., Ed., McGraw-Hill, New York, 1969,

pp 405-551. This is an extensive treatise on

drying paper, with engineering and economic

calculations.

35.

Chalmers, G.J., Today's dryer section: an

overview, PIMA 70(6):45-51(June, 1988).

This is a good, introductory, nontechnical

article on drying.

36.

Siegler, D.M., Reviewing dryer section drive

methods, operating considerations, and costs,

PaperAge

107(2):

12,

13, 30(1991). This is

a useful article on drive methods for the

dryer section.

37.

TAPPI TIS 0402-16, Guidelines for the

inspection and nondestructive examination of

paper machine dryers (9 p.) and about 20

other TIS references.

ANNOTATED BIBLIOGRAPHY 261

Yankee

dryers

38.

Sloan, J.H., Yankee dryer coatings,

Tappi

74(8):

123-126(1991) with no references.

This article discusses coatings and how they

relate to drying and creping.

39.

Corby, W.G., Jr.,

Guidelines

for the Safe

Operation of Yankee Dryers, Tappi Press,

1986, 33 p. The introduction describes

yankee dryers as the class of grey cast iron

drying cylinders 10-20 ft in diameter and up

to 300 in. wide that weigh up to 380,000 lb

and operate with up to 140 psi steam pres-

sure at speeds up to and beyond 6000 ft/min.

The introduction indicates that they may

contain an energy equal to 100 lb of

TNT,

safety is very important. Since 1950, the

article indicates, there has been only one

disastrous failure in the U.S.

Moisture content profile control

40.

Roth, R.C., Electromagnetic radiation for

CD moisture profile control, Tappi J.

69(1):57-61(1986).

41.

Higham, J.D., D.A. Stockford, and J.

Egierski, Locating infra-red drying equip-

ment for moisture profiling, Appita

41(5):398-400(1988).

Impulse

drying

42.

Crouse, J.W., Y.D. Woo, and C.H.

Sprague, Delamination-a stumbling block to

implementing impulse drying technology for

linerboard,

Tappi

72(10):211-215(1989).

43.

Sprague, C.H., Impulse drying and press

drying: a critical comparison, Tappi J.

70(4):79-84(1987).

44.

Bach, E.L., Why is press drying/impulse

drying delayed?-A critical review, Tappi J.

74(3)135-147(1991), with 55 refs. A discus-

sion of this article by J. D. Lindsay with

rebuttal by the author is in Tappi 7.

74(9):238-241(1991).

45.

Orloff,

D.L, Impulse drying of linerboard:

control of delamination, J. Pulp Paper Sci.

18(1):J23-J32(1992). The author purports to

have controlled delamination, one

reason

this

process is not yet commercial.

On-line measurement

of paper properties

46.

Mercer, P.O., On-line instrumentation for

wet-end control, Appita 41(4):308-312(Jul

1988).

This is a usefiil article on measuring

grammage, moisture, mineral content, cali-

per, optical properties, and fiber orientation.

Calendering,

reeling, and

rewinding

47.

MacDonald, R.G., Ed., Pulp and Paper

Manufacture,

Volume 3, McGraw-Hill, New

York, 1969, pp 553-641. Three chapters

spanning these pages cover these areas.

48.

Schiller, F.E., Manual of Supercalender

Operations, Miller Freeman, San Francisco,

1976, 136 p. This is a operator guide.

49.

Journeaux, I., R. Crotogino, and M. Doug-

las,

The effect of actuator position on perfor-

mance of

CD calender control system. Pulp

Pap.

Can. 93(1):T17-T21(1992).

50.

Tuomisto, M.V., Upgrading groundwood

printing papers: What can soft calendering

do?.

Pulp Pap. Can. 93(2):T37-T40(1992).

Coating

and other

converting

See references 4 and 5 in Chapter 8.

51.

Satas, D., Ed.,

Web Processing and

Convert-

ing Technology and Equipment, Van Nos-

trand Reinhold Co., New York, 1984, 537 p.

There are 24 chapters including 9 chapters on

coaters and coating. There are also chapters

on some hard-to-find topics including

calendering, extrusion,

saturators,

laminating,

surface treatment, drying, IR and electron

beam curing, film orientation, winding, slit-

ting, splicing, web handling, sheeting, die

cutting, embossing, and static electricity.

52.

Gunning, J.R., Coating, in Pulp and Paper

Manufacture,

Volume 2, MacDonald, R.G.,

Ed.,

McGraw-Hill, New York, 1969, pp

457-532.

This is a good introduction to the

historical

equipment

development, methods of

coating, properties of

coated

paper,

pigments

used in coating, lists of dyes, starch, addi-

tives,

coating formulations, and finishing.

262 9. PAPER MANUFACTURE

53.

TAPPITIS 0102-01 (1985), Literature refer-

ences on the measurement of water retention

of paper coatings. 6 p. Over 40 abstracts on

are given on the title topic. The function of

water retention is "to improve the ability to

hold the vehicle (water) within coatings after

application and to decrease the migration to

the surface or into the base sheet."

54.

TAPPI TIS 0110-01 (1987), Factors to be

considered in selecting screening media for

coating processes. 2 p. TIS 0110-02 (1986),

Viscosity of coating colors at high shear

rates.

6 p.

EXERCISES

Wet

end

Why is an "S"-shaped curve used as the path

of the wires in some twin wire machines?

Why is fiber sometimes added to excess

white water prior to save-alls, i.e., what is

the purpose of sweetener stock?

Is turbulence desired in the papermaking

process? Discuss carefully!

Pressing

What are two advantages of the extended nip

press?

5. Why are the web and felt separated as quick-

ly as possible after a press nip?

6. What is roll crowning and why is it used?

7. Do press felts usually "wear

out"

per se?

8. Give at least three sources of contaminants

that may contribute to "stickles" formation in

the press felts and paper machine wire.

9. Often, the paper web is heated before the

press section for a particular purpose. What

do you think is the purpose, and what is the

theoretical basis for this action?

Drying

10.

Why are Yankee dryers used to make tissue

papers?

11.

Give two reasons why Yankee dryers are

used with various grades of paper.

12.

How do the temperatures of the early and

later dryer sections compare. Give some

actual reasonable values for them, and ex-

plain why their is a difference.

13.

What is the major advantage of a coarse

dryer felt and what is the major advantage of

a fine dryer felt?

14.

What is the typical steam economy for the

dryer section? How does this compare with

the steam economy of the multiple effect

evaporators?

Coating

15.

Besides additives, what are the two main

categories of coating constituents?

Paper properties

16.

What operations contribute to the final cali-

per of

paper

(for a given basis weight) and to

what extent is each important (relatively)?

17.

Where does the ash content tend to be higher

on filled sheets, on the wire side or on the

felt side of paper made on single-wire

fourdrinier machines? Why?

18.

What is one possible disadvantage of having

a two-sided sheet? Hint: think of how a

thermostat coil of metal ribbon works to

indicate and control temperature or how a

Bourdon tube works to indicate pressure.

19.

How do strength and bulk relate to each

other. Stated another way, how do they

interact and why do they interact that way?

(Think of refining curves and paper

strength.) Why are both desired in printing

papers? How does the use of adhesives

affect the picture?

20.

What is the difference between bonds formed

with

wet-strength adhesives and those formed

between fibers without added adhesive or

using starch as an adhesive?

21.

How is a corrugated box like an I-beam?

Sizing

22.

What is the mechanism whereby starch acts

as a sizing agent?

FIBER FROM RECYCLED PAPER

10.1 INTRODUCTION

Obtaining fiber from recycled paper is a

matter of separating impurities from the usable

fiber. This involves extensive systems for remov-

ing foreign materials including skimmers to re-

move floating items, removing heavy items at the

bottom of a repulper, and removing stringy items

such as rope and wet strength papers. Coarse

screening is used for further cleaning before using

fine screens. Vortex cleaners, through-flow

cleaners, and, for printing and tissue grades,

deinking systems are used. The steps used in

recovering fiber can be accomplished in a wide

variety of different orders.

Recycled or secondary fiber

The source of recycled fiber is recycled paper

or paperboard arising outside of the mill. It is

distinguished from broke, which is off-specifica-

tion paper produced at the mill and reused within

the mill. There may be similar considerations,

however, when using broke in a mill.

It is very important to have "pure" sources of

paper from which to recover high quality fiber.

Newspapers should not be mixed with magazines,

brown paper, or boxes. Office papers should not

be contaminated with newsprint or brown papers.

For example, in 1988 mixed waste paper was

worth about $5-25/ton, newspaper was worth $25-

45/ton, corrugated containers were worth $36-

60/ton, while clean, hard, white paper clippings

from an envelope factory were worth $390-

470/ton. In the U.S. almost 30% of the paper

consumed in 1989 was recycled, while Japan had

a recovery rate of 50%. Other developed nations

tend to have recovery rates between 30-50%.

The product with the largest recovery by

amount and percentage in the U.S. is old corru-

gated containers (OCC). Over 50% of OCC is

recovered in the U.S. One reason is that large

amounts of OCC are generated at specific sites

such as grocery stores and other retail outlets.

Newspapers and other post-consumer wastes are

much more expensive to collect and tend to be

highly contaminated with unusable papers and

trash. Still, 33% of newsprint is recovered, but

only one-third of this ends up in new newsprint.

Many U.S. states, however, have enacted (or are

working on) legislation that demands large

amounts of recycled fiber (10-50%) in newsprint.

The Garden State Paper Co. in New Jersey

was the first U.S. company to use deinked news-

print in newsprint. They started with a 90 ton per

day facility using a washing process in the 1960s.

Use of recycled paper

About 80% of all waste paper comes from

three sources: corrugated boxes, newspapers, and

office papers. Less than 20% of waste paper is

deinked to be used in newsprint, tissue, or other

bright grades. Most waste paper is used in paper-

boards, chipboard, and roofing materials where

color is not important. The percentage of deinked

newsprint and other grades is expected to increase

considerably over the next few years.

Shrinkage

Shrinkage represents the loss of material from

the original feedstock to the recovered product. A

plant that recovers 90 lb of dry fiber for every 100

lb of dry paper has a shrinkage of 10%. A plant

recovering OCC may have a shrinkage of about

8%. A plant recovering newsprint for use in

newsprint (news to news) may have a shrinkage of

15-20%

for flotation deinking and up to 30%

using combined flotation and washing deinking. A

plant recovering office paper and producing pulp

of high brightness (above 85%) may have shrink-

age of 35%. Shrinkage represents the loss of

fillers, fines, plastics, dirt, ink, and useful fiber.

10.2 RECYCLED FIBER PREPARATION

The nature of

the

contaminants and their removal

One of

the

biggest obstacles to using recycled

or secondary fiber is effective contaminant remov-

al.

Recycling of paper is a process of removing

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