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CPP > Ch 6 Paperboard > Flashcards

Ch 6 Paperboard Flashcards

1
Q

What is PAPER composed of

A

Commercially made of fiber sources such as rags (linen) and bagasse (sugar)

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2
Q

ISO defines PAPERBOARD as

A

Material weighing more than 250G per sq meter or thicker than 300 micrometers (0.012 in)

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3
Q

Approximate FIBER LENGTH of Cellulose used in papermaking

A

Hardwood = 2 millimeters / 0.08 inch
Softwood = 4 millimeters / 0.16 inch

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4
Q

What are the pros and cons of having LONGER FIBERS?

A

PROS - good folding ability, high tensile strength and high burst strength
CONS - produces a “Wild Formation” which is an unequal distribution of fibers resulting in rougher printing surface

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5
Q

What are SHINERS

A

Grease spots or tiny bits of color produced by water insoluble adhesives and non-removable printing inks.

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6
Q

What are LIGNINS?

A

Natural adhesive that binds cellulose fiber together. Lignins are not water soluble and cannot be removed by simple water washing.

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7
Q

Describe the MECHANICAL PULPING method

A

Process that separates cellulose fiber from wood by abrading / cutting the wood.
Typically used for lower quality papers such as newsprint or blending with more expensive pulps.

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8
Q

Describe the CHEMICAL PULPING method

A

Process where chemicals directly dissolve the natural lignin binders in wood.
This process causes the least amount of damage to the wood.
Two common chemical used for chemical pulping include alkali sulfate (common extraction process) or acid sulfites (preferred for softwoods).

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9
Q

Describe the SEMI CHEMICAL PULPING process.

A

The wood is partly digested by chemicals then is thermo-mechanically refined by heat (softening the wood).

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10
Q

What is the weakest and strongest type of pulp?

A

Strongest = Kraft Pulp at 10 Relative Strength
Weakest = Stone groundwood at 3 Relative Strength

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11
Q

What are FIBRILS?

A

Small fiber strands produced by cellulose during the REFINING process.

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12
Q

What is the purpose of CHEMICAL BLEACHING paper?
Name the most common bleaching compound?

A

Reduces strength of final paper.
Hydrogen peroxide is a common bleaching compound combined with chlorine.

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13
Q

What is PICK RESISTANCE?

A

Then tendency for fibers to pick off the paper surface.
This is usually improved by adding starches and gums (or other additivies)

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14
Q

What is FURNISH?

A

Mixture of fiber, water and additives that is fed to the paper-making machine.

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15
Q

Describe the FOURDRINER MACHINE process? What are some of its limitations?

A

These machines pump furnish from a headbox directly onto a moving wire screen through which the water is continuously drained. At the WET END of the machine, the free water is removed and dried by heating drums.

These are limited on producing heavier caliper boards unless wet pulp layers are laid out by two or more separate machines.

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16
Q

What is a COUCH ROLL?

A

This is the wet paper that has enough strength to be removed from a FOURDRINER MACHINE.

17
Q

Describe the CYLINDER MACHINE process? What are some of it’s disadvantages and advantages?

A

Machine rotates a screen drum in a vat of FURNISH. As fiber accumulates on the outside of screen it passes through further rotating cylinders each depositing another fiber layer.

ADV = Can produce higher caliper boards and low quality fiber can be used to fill the bulk of the middle of board.
DIS = Bonds between layers are weak

18
Q

What are FILLER PLIES?

A

Economical recycled pulps that have little impact on stiffness. These typically comprise the bottom liner of paperboard.

19
Q

Describe the TWIN-WIRE MACHINE process?

A

Formers inject the FURNISH between two moving wire screens. Dewatering takes place on both sides of paper and is therefore fast.

20
Q

What does MD and CD stand for? Why are they important for a carton designer?

A

MD = Machine Direction = direction of travel for fibers during papermaking
CD = Cross Direction = direction perpendicular to the papermaking machine and fiber alignment
Properties of paper vary in the CD and MD

21
Q

What is the typical tensile strength ratio for MD and CD on a:
1) Fourdrinier Machine
2) Cylinder Machine

A

1) 2:1
2) 4:1

22
Q

Improving fiber alignment ratios in the MD also improves which properties?

A

Improves fold endurance across the MD
Improves stiffness across the MD
Improves tear strength across the MD

23
Q

Describe the CALENDERING process and what is its purpose?

A

Is an operation where dried paper is passed through sets of heavy rolls. Primary purpose is to smooths out the surface improving caliper consistency and printability

24
Q

What are Machine-Glazed or Chrome-Coated Papers?

A

A type of paper formed by passing through highly polished chrome drums that are rotating counter to the paper faster than paper’s travel speed. This greatly polishes the paper.

25
Q

Describe how CLAY LIFT occurs and what it means to have HICKEY’s on paper?

A

CLAY LIFT is a situation where an adhesive has bonded well to a clay surface but the bond separated because the clay lifted away from the paper base.

In lithographic printing, HICKEY’s occur when the tacky lithographic ink picks off a small particle of the clay coating

26
Q

Paper caliper is expressed in two different units?

A

1) Points or 1 thousandths of an inch
2) Micrometers (um) or 1 thousandths of a millimeter

27
Q

Basis weight is usually specified in which units?
Grammage is usually defined as?

A

1) Pounds per 1000 square feet.
2) Weight (in any unit) / 1 square meter.

28
Q

What is the BRIGHTNESS scale? What is the brightest known material at the time? What is the newly discovered brightest material now?

A

Brightness is a scale of 1 - 100 with 0 being no color and 100 being MAGNESIUM OXIDE (brightest known material).
TITANIUM OXIDE is discovered to have an even higher brightness value at 108.

29
Q

What does it mean that paper is HYGROSCOPIC? What does a paper at 20% RH mean? What are the ideal conditions for paper testing?

A

HYGROSCOPIC means the paper absorbs and loses moisture according to ambient relative humidity (RH).
Paper at 20% RH will contain about 4% moisture.
Ideal paper testing conditions are 50% RH 23°C.

30
Q

What does HYDROEXPANSIVE mean? Which way do fibers curl at lower humidity?

A

HYDROEXPANSIVE means paper expands when it absorbs moisture and shrinks when it dries.
At low humidity (20% RH) fibers tend to curl away from the material coating.

31
Q

What do VISCOELASTIC properties refer to with paper? What is CREEP and how does it affect compressive strength?

A

VISCOELASTIC means that certain strength values will depend on the rate that a load is applied.
CREEP occurs over long loading periods as the fibers shift and distort over time. Compressive strength of a corrugate box is expected to fall to 50% within one year after being stored in a warehouse.

32
Q

Describe the composition of NEWSPRINT grade paper?

A

This grade is composed of 95% economical mechanical and groundwood pulps.
Basis Weight = 49g per m^2
Brightness = 55 to 65

33
Q

Describe GREASEPROOF paper composition and what they’re used for?

A

Papers made from chemical pulps that have been highly refined to break up fiber bundles. Typically used for snacks, cookies, butter, or oily products.

34
Q

Describe the composition of KRAFT PAPER?

A

This is the strongest of papers and is used for industrial bags, carry-out grocery bags and inner plies of multiwall bags.

35
Q

Define what CONTAINERBOARD is?

A

Refers to linerboard and medium produced for use in corrugate board.
Basis Weight = 126g per m^2

36
Q

Describe the paper grade of CHIPBOARD / NEWSBOARD?

A

Made from 100% recycled fiber and is the cheapest paperboard. Short fibers make it very suitable for printing

37
Q

Describe paperboard grade of SBS?

A

Stands for Solid Bleached Sulfate which is produced by bleached chemical pulp. Used for higher end packaging in health care, cosmetics and greeting cards.

38
Q

Describe paper grade of SUS?

A

Stands for Solid Unbleached Sulfate which is composed of brown chemical pulp. Is a maximum strength paperboard used where surface appearance is important and will sometimes be double-coated.

Example: beverage baskets (6 packs).

39
Q

Describe how minimal or high amounts of refining affects paper properties.

A
  • Minimal refining = high tear strength & absorbency but low burst strength.
  • High refining = reduced paper opacity

CPP (3 decks)

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