l04 msc nutra paper 1

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M.Sc.(Nutraceuticals) 2011 CSP TRG AIDS


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DEFINITION OF PAPER

Paper is defined as a matted or felted sheet usuallycomposed of plant fiber. Paper has been commerciallymade from such fiber sources as rags (linen), bagasse

(sugar cane), cotton, and straw.

Modern paper is made almost exclusively from cellulosefiber derived from wood. Although the word paper isderived from the Egyptian term, papyrus was not a

true paper in the modern sense.

INVENTION OF PAPERThe invention of paper by blending cellulose fibers didnt

occur until the beginning of the second century A.D.

PAPER


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HISTORY

Tsai Lun, a member of the court of the later HanDynasty, is generally credited with developing the first

real papermaking process in 105 A.D.

The Fourdrinier machine was the first on the market

and produced a homogenous (single-ply) sheet ofboxboard in various thicknesses. It was soon joined by

the Cylinder machine which formed a multi-layered

(multi-ply) type of paperboard. These machines were first

installed in the United States around 1830.


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PAPER & PAPERBOARD

Paperboard, boxboard, cardboard, and cartonboard are all

terms used to describe heavier paper stock.

The International Organization for Standardization (ISO)

states that material weighing more than 250 grams persquare metre shall be known as paperboard.

U.S. practice calls material that is more than 300 micron

(0.30mm) thick paperboard.


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PAPER MANUFACTURE

Basic principles of paper and paperboard making have not

changed for more than two thousand years. Fibres taken

from timber are evenly distributed in water. Multiple layers

of furnish are applied one after another on a wire. Water isdrained from the pulp and the layers are formed into a

strong fibre mat. Smooth surface is achieved by coatings and

calendering.


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50%CELLULOSE

25% HEMICELLULOSE + 25%LIGNIN

WOOD

PAPER

PAPER MANUFACTURE

PAPER IS A CELLULOSIC MATERIAL. WOOD HAS 50%

CELLULOSE & 50% MIXTURE OF HEMI CELLULOSECOMPOUND & LIGNIN WHICH BIND CELLULOSIC FIBRES

TOGETHER

LIGNIN IS A PHENOLIC COMPOUNDWHICH GIVES THE COLOUR TO PAPER AND BINDS

THE HEMI CELLULOUSE & CELLOLOSE


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PAPER MANUFACTURE

WOOD

HARD WOOD

SOFT WOOD

CONIFEROUSTEMPERATE

3.5-4 mm

DECIDIOUSTROPICAL1 1.5mm

FOR PAPER MAKING,THESE FAIBRES ARE SEPERATED FROM EACH OTHER TO BECOME DISCRETE ENTITIES THROUGH A DRASTICACTION AND LATER MATTED


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PAPER MANUFACTUREPULPING SECTION PAPER MAKING SECTION

WOOD

DEBARKINGSOAKING

CHIPPINGDIGESTING

BEATING

FILLERSSIZING

REFINING

STAGE 1MAKE READY

STAGE 2PULPING

STAGE 3STOCK

PREPARATION

FORMATION

PRESSING & DRYING

COATING

STAGE 4SHEETING

STAGE 5FINISHING

CALENDERING

WINDING


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PAPER MANUFACTURE

PAPER MILLS CAN TAKE UP TWO ROUTES

1. INTEGRATED

FROM STAGE 1 TO STAGE 5

1. NON INTEGRATED

FROM 3 TO 5

NON INTEGRATED MUST BRING THE PULP EITHER

SLURRY FORM OR SOLID FORM FOR PAPER MAKING


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PAPER MANUFACTURESTAGE 1 MAKE READY

WOOD

DEBARKING

SOAKING

TO STAGE 2

SOAKED TO MAKE IT SOFT

DRY OUTSIDE LAYER (BARK) REMOVED

TREE CUT TO LOGS TIMBER


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PAPER MANUFACTURESTAGE 2 PULPING

CHIPPING

PULPING

TO STAGE 3

FROM STAGE 1

(DIGESTER/ COOKING)

MECHANICAL, CHEMICAL & SEMI-CHEMICAL PROCESSES

CUT TO SMAILL PIECES FOR EASY COOKING


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PAPER MANUFACTURE

PULPING SECTION

MECHANICAL CHEMICAL SEMI CHEMICAL KRAFT PULPING

PROCESS OF CHANGING WOOD INTO AN AQUEOUS PULP SOLUTION


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PAPER MANUFACTURE

MECHANICAL PULPING

SIMPLY GRINDING WOOD

CRITICAL AS FIBRES GET DESTROYED

NO PURIFICATION OF PULPCOMPOSITION OF WOOD UNCHANGED

LIGNIN PRESENT

LESS STRENGTH

YIELD 90% OF WOOD MASSe.g. Newsprint paper


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PAPER MANUFACTURE

CHEMICAL PULPING

PROCESS FOR MOST PAPER PRODUCED

FULL CHEMICAL TREATMENT

REMOVE NON CELLULOSE

KEEP CELLULOSE INTACTIN PRACTICE, 100% NOT POSSIBLE

YIELD 50% WOOD MASS YIELD

BETTER STRENGTH

EASY BLEACHING BECAUSE LIGNIN REMOVEDe.g. Most of paper used


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PAPER MANUFACTURE

SEMI CHEMICAL PULPING

SOME MECHENICAL AGITATION AFTER CHEMICAL

DISINTEGRATE THE WOOD CHIP

RECOGNISED AS YIELDING BETTER QUALITYYIELD 60% OF WOOD MASS

BETTER STRENGTH THAN CHEMICAL PULP

e.g. Most of todays papers


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PAPER MANUFACTUREKRAFT PULPING

MOST OF PAPER MAKINGS IN USALOG COVERTED TO EVEN SIZE CHIPS

CHIPS AND CHEMICAL SOLUTION ARE COOKED

CHEMICALSOLUTION IS WHITE LIQUOR

COOKING IN DIGESTER(HIGH TEMP & PRESSURE)

COOKING DISSOLVES 50% OF MASS (LIGNIN)

WASHING AFTER COOKING SEPERATES LIGNIN

WASHED OUT LIQUID IS BLACK LIQUORRECOVERY OF SPENT LIQUOR POSSIBLE

YIELD 50% OF WOOD MASS


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PAPER MANUFACTURESTAGE 3 - STOCK PREPARATION

STOCK PREPARATION IS THE PROCESS OF MECHANICALLY

BEATING THE PULP SO AS TO MAKE THE FIBRES MORE

READILLY SUITED FOR LAYING IT IN A UNIFORM WEB AND TOINTER CONNECT SO AS TO MAKE IT STRONGER SHEET. e.g.

FIBRES CAN BE KINKED/CURLED, CUT/SHORTENED, MADE

FLEXIBLE, FIBRILLATE TO LOOK FUZZY. ALL THESE AFFECT

THE WAY FIBRES BOND TOGATHER IN SHEET. IT STRONGLYINFLUENCES STRENGTH AND ITS LIGHT SCATTERING

PROPERTIES.

TO STAGE 4ROM STAGE 2 BEATING REFINING SIZING FILLERS


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UNBEATEN BEATEN FIBRILLATED

TO STAGE 4ROM STAGE 2 BEATING REFINING SIZING FILLERS


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TO STAGE 4ROM STAGE 2


THE FURNISH (AS ITS REFERRED TO NOW), CAN ALSO

BE TREATED WITH MANY CHEMICAL ADDITIVES LIKERESINS FOR STRENGTH AND DYES AND PIGMENTS FOR

COLOUR., FILLERS LIKE TALC AND CLAY TO IMPROVE

OPTICAL PROPERTIES, SIZING AGENTS TO CONTROL

PENETRATION OF LIQUIDS AND IMPROVE PRINTINGPROPERTIES.

BEATING REFINING SIZING FILLERS


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PAPER MANUFACTURESTAGE 4 SHEETING

TO STAGE 5ROM STAGE 3 FORMATION PRESSING & DRYING


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Fourdrinier Machines

Fourdrinier machines pump furnish from a headboxdirectly onto a moving wire screen through which the

water is continuously drained. Fourdrinier machines may

have a second head box situated downstream of the first

head box to add further quantities of furnish onto thepartially dewatered initial lay-down.


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Furnish

Headbox


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PAPER MANUFACTURE


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PAPER MANUFACTURE

Cylinder Machines

A cylinder machine (Figure 3.3) rotates a screen

drum in a vat of furnish. (The paper is sometimescalled vat paper.) As the water pours through the

screen, fiber accumulates on the outside of the

screen. This thin layer of matted fiber is transferred onto

a moving felt belt that passes sequentially over further

rotating cylinders, each of which deposits another fiber

layer.

A single cylinder station on a cylinder-type machine


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PAPER MANUFACTURE

A single cylinder station on a cylinder-type machine


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PAPER MANUFACTURE

Cylinder machines dewater furnish at the cylinder and paste a thin layer of fiberagainst the felt.

A cylinder machine with six cylinders at which a paper layer can

be formed


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PAPER MANUFACTURE

The fibers of subsequent layers do notintermingle, andtherefore the bond between the layers isweak. The dry end is similar to that of thefourdrinier machine.Cylinder machines do not have the fourdriniermachine's limitation on the number ofstations, and six-or seven-station machines

are common. Higher-caliper boards forfolding and setup cartons are usually cylinderboards.Generally, papers are made on fourdrinier ortwin-wire formers, whereas heavierpaperboard products are made on cylinder-type machines. Extremely heavy boards are

made by laminating several thinner sheets.A typical cylinder board construction (Figure3.5):

Cylinder boards are multiplyboards. An advantage is that the

plies can all be different


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PAPER MANUFACTURE

Twin-Wire Machines

Vertiformers and twin-wire formers (Figure3.6) inject thefurnish between twomoving wire screens.The advantage isthat dewatering takesplace on both sides ofthe paper andis therefore fast. Thesemachines can producesingle andmulti-ply sheets withidentical formation atboth faces.

Water can be simultaneously removed

from both sides of the paper on a

twin-wire paper former


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PAPER MANUFACTURE

Surface or Dry-End, Treatments and

CoatingsAfter the paper is formed and dried, it isusuallypassed between multiple sets of heavyrolls (Figure 3.9.).This "calendering" operation has manyvariations, but the

prime objective is to iron and smooth outthe surface ofthe paper stock to make it more suitable forprinting.Calendering also compresses the papersheet, giving a

denser product and a glossier surface.Starch is a typical surface sizing used tofill surfacevoids and reduce liquid penetration rate.


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PAPER MANUFACTURE

Calendering consists of passing the formed dried paper between

sets of heavy rolls.

The paper surface may be dampened to help in smoothing it


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PAPER MANUFACTURESTAGE 5 FINISHING

FROM STAGE 4 COATING CALENDERING WINDING


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PAPER MAKING AT A GLANCE


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DRYERS


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FOURDRINIER PAPER MACHINE


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FOURDRINIER PAPER MACHINE Invented by Nicholas Louis Robert of France in 1798 the

continuous paper machine was not placed into commercial

operation until about 1804, though debate exists between

the dates of 1804 and 1807, in England by the Fourdrinier

brothers and has since been known as the Fourdrinier paper

machine.

Fourdrinier machine comprised of 4 sections:

first the wet end,

the press section,

the drier section, and

the calendar section.

Hendry

Fourdriner

(17661854)


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FOURDRINIER PAPER MACHINE

Paper Machine - Wet End

The wet end of the machine is where the refined pulp, spilling

from the headbox section is laid out to align its fibers across

the width of the wire or screen of the wet end to begin theprocess of aligning fibers in the machine running direction

and to remove water from the refined pulp which is a much

as 99% water content at this stage of production. Various

configurations of the wet end of the machine exist today toservice different paper grade requirements but all adhere to

the same principles of manufacturing.


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FOURDRINIER PAPER MACHINE Paper Machine - Press SectionThe press section can comprise of two or more presses. Thestill wet web of paper is transferred from the wire of the wetend onto the felt at the couch roll, and is then carried throughthe presses on the felts; the texture and character of the feltsmay vary depending on the various surface structures whichcan be applied here. Sometimes a linen pattern or other typesof surface structure are introduced to the paper depending on

the grade of paper being made. The main function of the pressis to continue to remove water from the pulp fibers and tosmooth the surface characteristics of the felt and wire sides(top and bottom sides) of the paper web running the length ofthe machine.


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FOURDRINIER PAPER MACHINE Paper Machine - Drier sectionThe drier section consists of a series of driers, which are normally steam-heated cylinders. The web of paper is transported firmly against the driersby the fabric drier felts which are used to move the paper continuouslyalong the length of the paper machine once past the wet end. As the web

passes from one drier to another, first the felt side (top side) and then thewire side (bottom side) are pressed against the heated surface of the drier.The web of paper enters the drier section with water content ofapproximately 65%; most of the remaining water is removed in this sectionof the paper machine. Within the drier section there can be a breaker stackused for imposing a finish to the paper surface and for the final machinedrying stage. The breaker stack normally consists of a pair of chilled metalor rubber-surfaced rollers. The cooling process of the chilled rollers bringsthe paper web into a more normal temperature range. When the papermanufacturing process is completed the paper will typically have amoisture range of 4-7% depending on the grade of paper beingmanufactured and on the end use requirements of the grade.


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FOURDRINIER PAPER MACHINE Paper Machine - Calender section

The calender section, the final section, consists of calenderstacks with a winding mechanism for gathering the paper webonto a roll as it leaves the end of the paper machine. The

calender section smoothes the paper and imparts, finish,thickness, or gloss. Water or starch, may also be used withinthe calender section to obtain specific surface finishes andimprove printing and other application characteristics. Afterthe calender stack the paper web exits the paper machine

and is rolled into a master machine roll where it can beremoved from the end of the paper machine and sent to aconverting station where the paper will be either slit intosmaller rolls or where it may be sheeted for use in offset

printing.


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Representative Papermaking Machines

Figure 3.3 A single cylinder station on a cylinder-type machine


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Cylinder machines dewater furnish at the cylinder and paste a thin

layer of fiber against the felt. (Figure 3.4.)

Figure 3.4 A cylinder machine with six cylinders at which

a paper layer can be formed


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Representative Papermaking MachinesThe fibers of subsequent layers do not intermingle, and

therefore the bond between the layers is weak. The dry end is

similar to that of the fourdrinier machine.

Cylinder machines do not have the fourdrinier machine's limitation

on the number of stations, and six-or seven-station machines arecommon. Higher-caliper boards for folding and setup cartons are

usually cylinder boards.

Generally, papers are made on fourdrinier or twin-wire formers,

whereas heavier paperboard products are made on cylinder-type

machines. Extremely heavy boards are made by laminating severalthinner sheets.

A typical cylinder board construction (Figure 3.5):


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Figure 3.5 Cylinder boards are multiply

boards. An advantage is that the plies can allbe different


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Representative Papermaking MachinesTwin-Wire Machines

Vertiformers and twin-wire formers (Figure 3.6) inject thefurnish between two moving wire screens. The advantage isthat dewatering takes place on both sides of the paper andis therefore fast. These machines can produce single andmulti-ply sheets with identical formation at both faces.

Machine Direction and Cross DirectionDepositing a fiber-and-water slurry onto a moving wire belttends to align fibers in the direction of travel, known as themachine direction (MD). The direction across theapermaking machine and across the fiber alignment is thecross direction (CD) (Figure 3.7). Because of this fiber

alignment, paper is an anisotropic material; measuredproperties differ depending on the direction in which theproperty is measured.


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Representative Papermaking MachinesFigure 3.6

Water can be

simultaneously

removed from

both sides of

the paper on a

twin-wire paper

former


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Figure 3.7 Fibers in a manufactured paper sheet

tend to align themselves in the machine direction


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Representative Papermaking MachinesFigure 3.8 shows the relationship of tear, stiffness,and fold endurance to machine direction. Paperspecification sheets normally show physical valuesmeasured in both directions. Package designers needto be aware of paper's directionality. Cylindermachines tend to align fibers more than fourdrinier

machines. Tensile strength ratios in MD and CD for atypical fourdrinier board are about 2:1, whereas for acylinder board the ratio might be 4:1 or higher,meaning that the MD tensile strength is four timesgreater than the CD tensile strength. The greater thedegree of fiber alignment, the greater the difference

in a given property when measured in MD and CD.The ratio of a property in the two directions is oftenused as a gauge of fiber alignment.


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Representative Papermaking MachinesFigure 3.8The

relationsh

ip

betweenMD and

tear,

stiffness,

and fold

enduranc

e

properties


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Representative Papermaking MachinesCylinder machines tend to align fibers more than

fourdrinier machines. Tensile strength ratios in MD and

CD for a typical fourdrinier board are about 2:1, whereas

for a cylinder board the ratio might be 4:1 or higher,meaning that the MD tensile strength is four times

greater than the CD tensile strength. The greater the

degree of fiber alignment, the greater the difference in a

given property when measured in MD and CD. The ratio

of a property in the two directions is often used as a

gauge of fiber alignment


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Representative Papermaking MachinesSurface or Dry-End, Treatments and Coatings

After the paper is formed and dried, it is usually

passed between multiple sets of heavy rolls (Figure 3.9.).

This "calendering" operation has many variations, but theprime objective is to iron and smooth out the surface of

the paper stock to make it more suitable for printing.

Calendering also compresses the paper sheet, giving a

denser product and a glossier surface.Starch is a typical surface sizing used to fill surface

voids and reduce liquid penetration rate.


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Figure 3.9 Calendering consists of passing the

formed dried paper between sets of heavy rolls.

The paper surface may be dampened to help in

smoothing it


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Representative Papermaking MachinesTo meet the highest opacity, gloss, brightness, and printing-detail requirements, papers are coated with pigments such as

clay, calcium carbonate, and titanium dioxide.

Coated papers are usually called "clay-coated" regardless of

the actual formulation. Coated papers are calendered to

maintain a high-quality, smooth surface.

In addition, highly sized and clay-coated boards can be

difficult to bond with water-based adhesive because of poor

liquid penetration and the inability of the adhesive to bond to

the underlying fibers. Where necessary, coated boards should

have perforations in the adhesive-bond areas so that adhesive

can penetrate to the body of the paper.


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END OF LECTURE 04

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l04 msc nutra paper 1

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