UNIT TWO
PACKAGING MATERIALS AND
CONTAINER
第二单元 包装材料和容器
Lesson 3
Paper and Paperboard
第 3课 纸与纸板
Introduction
Definition of paper,
·Paper is defined as a matted or felted sheet usually
composed of plant fiber,Paper has been commercially
made from such fiber sources as rags (linen),bagasse
(sugar cane),cotton,and straw,Modern paper is made
almost exclusively from cellulose fiber derived from wood,
·Although the word,paper” is derived from the Egyptian
term,“papyrus” was not a true paper in the modern
sense,
- Invention of paper
·The invention of paper by blending cellulose fibers didn’t
occur until the beginning of the second century A.D,
Introduction
Ts’ai Lun,a member of the court of the later Han
Dynasty,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 of
boxboard 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,
Introduction
Paper and 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 per
square metre (511b per 1,000 sq,ft.) shall be known
as paperboard,U.S,practice calls material that is
more than 300(0.012 in.) thick paperboard,
Representative Papermaking Machines
Fourdrinier Machines
Fourdrinier machines (Figure 3.1) pump furnish from a
headbox directly onto a moving wire screen through
which the water is continuously drained,Fourdrinier
machines may have a second headbox (Figure
3.2)situated downstream of the first headbox to add
further quantities of furnish onto the partially dewatered
initial lay-down,
Representative Papermaking Machines
Figure 3.1 Furnish pours out of the headbox of a
fourdrinier machine and onto an endless wire or
screen where excess water can be drained,The fibers
remain trapped on the screen
Representative Papermaking Machines
Figure 3.2 Paper is dewatered at the wet end of a fourdrinier machine
Representative Papermaking Machines
Cylinder Machines
A cylinder machine (Figure 3.3) rotates a screen
drum in a vat of furnish,(The paper is sometimes
called 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,
Representative Papermaking Machines
Figure 3.3 A single cylinder station on a cylinder-type machine
Representative Papermaking Machines
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
Representative Papermaking Machines
The 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 are
common,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 several
thinner sheets,
A typical cylinder board construction (Figure 3.5),
Representative Papermaking Machines
Figure 3.5 Cylinder boards are multiply
boards,An advantage is that the plies can all
be different
Representative Papermaking Machines
Twin-Wire Machines
Vertiformers and twin-wire formers (Figure 3.6) inject the
furnish between two moving wire screens,The advantage is
that dewatering takes place on both sides of the paper and
is therefore fast,These machines can produce single and
multi-ply sheets with identical formation at both faces,
Machine Direction and Cross Direction
Depositing a fiber-and-water slurry onto a moving wire belt
tends to align fibers in the direction of travel,known as the
machine direction (MD),The direction across the
apermaking machine and across the fiber alignment is the
cross direction (CD) (Figure 3.7),Because of this fiber
alignment,paper is an anisotropic material; measured
properties differ depending on the direction in which the
property is measured,
Representative Papermaking Machines
Figure 3.6
Water can be
simultaneously
removed from
both sides of
the paper on a
twin-wire paper
former
Representative Papermaking Machines
Figure 3.7 Fibers in a manufactured paper sheet
tend to align themselves in the machine direction
Representative Papermaking Machines
Figure 3.8 shows the relationship of tear,stiffness,
and fold endurance to machine direction,Paper
specification sheets normally show physical values
measured in both directions,Package designers need
to be aware of paper's directionality,Cylinder
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,
Representative Papermaking Machines
Figure 3.8
The
relationsh
ip
between
MD and
tear,
stiffness,
and fold
enduranc
e
properties
Representative Papermaking Machines
Cylinder 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
Representative Papermaking Machines
Surface 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 the
prime 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,
Representative Papermaking Machines
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
Representative Papermaking Machines
To 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,
Representative Papermaking Machines
Paper Characterization
Caliper and Weight
In inch/pound units,
·Caliper is expressed in thousandths of an inch or in
"points." One thousandth of an inch is 1 point,(For
example,a 0.020-in,board would be 20 points.)
·Containerboard for the corrugated board industry and
most paperboards are specified by the weight in
pounds per 1,000 sq,ft.,the "basis weight."
·Fine papers can be specified by the weight in pounds
per ream,A ream is 500 sheets,but the actual sheet
size can vary depending on the product,In most
instances a ream is taken to be 3,000 sq,ft.,
Representative Papermaking Machines
In metric units,
·Caliper is expressed in "m",
·Paper mass/unit area relationship is reported as
"grammage",defined as being the mass (weight) of
paper in 1 square metre(m2),
The metric conversion factors are
lbs./l,000 sq,ft,4.88 = grams/m2
0.001 inch 25.4 = (usually rounded to 25)
1 mm = 1,000
Brightness
Brightness is a measure of the total reflectance of white
light,
Representative Papermaking Machines
Paper and Moisture Content
Paper is hygroscopic and absorbs and loses moisture according to
the ambient relative humidity (R.H.) and temperature,
The physical properties of paper vary dramatically with moisture
content,and in some applications the moisture content of the paper
during processing must be controlled,
Because physical characterization values depend on moisture
content,all paper testing must be done at a precisely controlled
temperature and humidity,Internationally,the standard conditions
are specified as 23° C and 50% R.H,
Paper is hygroexpansive,when it absorbs moisture,it expands;
when it dries out,it shrinks,Between 0 and 90% R.H.,the
dimensions can change 0.8% in the MD and 1.6% in the CD,
Representative Papermaking Machines
Paper/foil laminate Paper/foil laminate Paper/foil laminate
at 40% R.H,at 20% R.H,at 80% R.H,
Figure 3.10 Paper's hygroexpansive nature can cause unwanted
curling when paper is bonded to an environmentally
stable surface
Representative Papermaking Machines
Whenever a paper sheet is laminated to or coated with a
material that is not affected by moisture (for example,
plastic film,aluminum foil,or heavy print or varnish),
there is the potential for curling when the humidity
changes,
Viscoelasticity
Paper is more or less viscoelastic,depending on the rate
at which load is applied,Simply put,the faster a load is
applied,the greater the apparent strength,Over long
loading periods,paper fibers move and distort or "creep."
Representative Papermaking Machines
Paper Types,
Newsprint and Related Grades,
Book Papers,
Commercial Papers,
Greaseproof Papers,
Natural Kraft Paper,
Bleached Krafts and Sulfites,
Tissue Paper,
Label Paper,
Pouch Papers,
Containerboards (linerboard and medium),
Representative Papermaking Machines
Paperboard Grades,
Chipboard,Cardboard,Newsboard,
Bending Chipboard,
Lined Chipboard,
Single White-Lined (SWL) Paperboard,
Clay-Coated Newsback (CCNB),
Double White-Lined (DWL) Paperboard,
Solid Bleached Sulfate (SBS),
Food Board,
Solid Unbleached Sulfate (SUS),
Representative Papermaking Machines
Paperboard Cartons
Paperboard provides a versatile and economical material not readily
matched by other packaging mediums,One significant advantage is
the low tooling cost compared with that for materials such as plastics,
Effective paperboard package design is based partly on knowledge
of paper and product properties and partly on craftsmanship and art,
Paperboard packaging can be considered in a number of categories,
Folding Cartons,Folding cartons are by far the largest and most
important group in paperboard packaging,Folding cartons are made
as flat blanks or as preglued forms that can be flattened for shipping,
They can be made economically on high-speed production
machinery,The majority of folding carton designs can be classified
as falling into either the tube-style (Figure 3.11) or the tray-style
design families(Figure 3.12),
Representative Papermaking Machines
Figure 3.11 A gable-top carton blank and an erected gable-top carton
Representative Papermaking Machines
Figure 3.12 A six-cornered Brightwood tray,flat and assembled
Representative Papermaking Machines
The gable-top container(Figure 3.11) is basically a tube-
style carton that has found many applications,
particularly for dairy products and fruit juices,The heavily
sized and polyethylene-coated board is erected and
heat-sealed at the point of fill,Combibloc and Tetra Pak
are similar-appearing proprietary cartons made from
complex paper/foil/poly laminates,A principal application
is for aseptic beverage packaging such as juice boxes,
Representative Papermaking Machines
Setup Boxes,
Setup boxes (Figure 3.13) are rigid cartons that are
delivered erected and ready for filling,
Setup boxes are not as amenable to high-speed
production as folding cartons,and their manufacture,by
comparison,is slow and labor intensive,
Setup boxes are typically constructed from a heavy,
low-grade chipboard with no particular folding or printing
qualities,In its most elementary form,the board is cut to
shape,and the sides folded up and taped with stay tape
to form a stayed box,
Representative Papermaking Machines
Figure 3.13 Examples of setup box designs
Representative Papermaking Machines
Tubs,Trays,and Liquid-Resistant Boxes,Paperboard
can be formed into round or square tubs with paper end
seals,Such forms,constructed from food board,are
used to contain such items as ice cream and frozen
foods,Flat sheets with gusseted corners can be folded to
form food trays for frozen entrees or other food products,
In most wet food applications,the board is coated with
either polyethylene or wax,Dual-ovenable paperboard
trays are coated or laminated with an oven-temperature-
tolerant plastic such as poly(ethylene terephthalate),
PACKAGING MATERIALS AND
CONTAINER
第二单元 包装材料和容器
Lesson 3
Paper and Paperboard
第 3课 纸与纸板
Introduction
Definition of paper,
·Paper is defined as a matted or felted sheet usually
composed of plant fiber,Paper has been commercially
made from such fiber sources as rags (linen),bagasse
(sugar cane),cotton,and straw,Modern paper is made
almost exclusively from cellulose fiber derived from wood,
·Although the word,paper” is derived from the Egyptian
term,“papyrus” was not a true paper in the modern
sense,
- Invention of paper
·The invention of paper by blending cellulose fibers didn’t
occur until the beginning of the second century A.D,
Introduction
Ts’ai Lun,a member of the court of the later Han
Dynasty,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 of
boxboard 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,
Introduction
Paper and 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 per
square metre (511b per 1,000 sq,ft.) shall be known
as paperboard,U.S,practice calls material that is
more than 300(0.012 in.) thick paperboard,
Representative Papermaking Machines
Fourdrinier Machines
Fourdrinier machines (Figure 3.1) pump furnish from a
headbox directly onto a moving wire screen through
which the water is continuously drained,Fourdrinier
machines may have a second headbox (Figure
3.2)situated downstream of the first headbox to add
further quantities of furnish onto the partially dewatered
initial lay-down,
Representative Papermaking Machines
Figure 3.1 Furnish pours out of the headbox of a
fourdrinier machine and onto an endless wire or
screen where excess water can be drained,The fibers
remain trapped on the screen
Representative Papermaking Machines
Figure 3.2 Paper is dewatered at the wet end of a fourdrinier machine
Representative Papermaking Machines
Cylinder Machines
A cylinder machine (Figure 3.3) rotates a screen
drum in a vat of furnish,(The paper is sometimes
called 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,
Representative Papermaking Machines
Figure 3.3 A single cylinder station on a cylinder-type machine
Representative Papermaking Machines
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
Representative Papermaking Machines
The 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 are
common,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 several
thinner sheets,
A typical cylinder board construction (Figure 3.5),
Representative Papermaking Machines
Figure 3.5 Cylinder boards are multiply
boards,An advantage is that the plies can all
be different
Representative Papermaking Machines
Twin-Wire Machines
Vertiformers and twin-wire formers (Figure 3.6) inject the
furnish between two moving wire screens,The advantage is
that dewatering takes place on both sides of the paper and
is therefore fast,These machines can produce single and
multi-ply sheets with identical formation at both faces,
Machine Direction and Cross Direction
Depositing a fiber-and-water slurry onto a moving wire belt
tends to align fibers in the direction of travel,known as the
machine direction (MD),The direction across the
apermaking machine and across the fiber alignment is the
cross direction (CD) (Figure 3.7),Because of this fiber
alignment,paper is an anisotropic material; measured
properties differ depending on the direction in which the
property is measured,
Representative Papermaking Machines
Figure 3.6
Water can be
simultaneously
removed from
both sides of
the paper on a
twin-wire paper
former
Representative Papermaking Machines
Figure 3.7 Fibers in a manufactured paper sheet
tend to align themselves in the machine direction
Representative Papermaking Machines
Figure 3.8 shows the relationship of tear,stiffness,
and fold endurance to machine direction,Paper
specification sheets normally show physical values
measured in both directions,Package designers need
to be aware of paper's directionality,Cylinder
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,
Representative Papermaking Machines
Figure 3.8
The
relationsh
ip
between
MD and
tear,
stiffness,
and fold
enduranc
e
properties
Representative Papermaking Machines
Cylinder 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
Representative Papermaking Machines
Surface 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 the
prime 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,
Representative Papermaking Machines
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
Representative Papermaking Machines
To 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,
Representative Papermaking Machines
Paper Characterization
Caliper and Weight
In inch/pound units,
·Caliper is expressed in thousandths of an inch or in
"points." One thousandth of an inch is 1 point,(For
example,a 0.020-in,board would be 20 points.)
·Containerboard for the corrugated board industry and
most paperboards are specified by the weight in
pounds per 1,000 sq,ft.,the "basis weight."
·Fine papers can be specified by the weight in pounds
per ream,A ream is 500 sheets,but the actual sheet
size can vary depending on the product,In most
instances a ream is taken to be 3,000 sq,ft.,
Representative Papermaking Machines
In metric units,
·Caliper is expressed in "m",
·Paper mass/unit area relationship is reported as
"grammage",defined as being the mass (weight) of
paper in 1 square metre(m2),
The metric conversion factors are
lbs./l,000 sq,ft,4.88 = grams/m2
0.001 inch 25.4 = (usually rounded to 25)
1 mm = 1,000
Brightness
Brightness is a measure of the total reflectance of white
light,
Representative Papermaking Machines
Paper and Moisture Content
Paper is hygroscopic and absorbs and loses moisture according to
the ambient relative humidity (R.H.) and temperature,
The physical properties of paper vary dramatically with moisture
content,and in some applications the moisture content of the paper
during processing must be controlled,
Because physical characterization values depend on moisture
content,all paper testing must be done at a precisely controlled
temperature and humidity,Internationally,the standard conditions
are specified as 23° C and 50% R.H,
Paper is hygroexpansive,when it absorbs moisture,it expands;
when it dries out,it shrinks,Between 0 and 90% R.H.,the
dimensions can change 0.8% in the MD and 1.6% in the CD,
Representative Papermaking Machines
Paper/foil laminate Paper/foil laminate Paper/foil laminate
at 40% R.H,at 20% R.H,at 80% R.H,
Figure 3.10 Paper's hygroexpansive nature can cause unwanted
curling when paper is bonded to an environmentally
stable surface
Representative Papermaking Machines
Whenever a paper sheet is laminated to or coated with a
material that is not affected by moisture (for example,
plastic film,aluminum foil,or heavy print or varnish),
there is the potential for curling when the humidity
changes,
Viscoelasticity
Paper is more or less viscoelastic,depending on the rate
at which load is applied,Simply put,the faster a load is
applied,the greater the apparent strength,Over long
loading periods,paper fibers move and distort or "creep."
Representative Papermaking Machines
Paper Types,
Newsprint and Related Grades,
Book Papers,
Commercial Papers,
Greaseproof Papers,
Natural Kraft Paper,
Bleached Krafts and Sulfites,
Tissue Paper,
Label Paper,
Pouch Papers,
Containerboards (linerboard and medium),
Representative Papermaking Machines
Paperboard Grades,
Chipboard,Cardboard,Newsboard,
Bending Chipboard,
Lined Chipboard,
Single White-Lined (SWL) Paperboard,
Clay-Coated Newsback (CCNB),
Double White-Lined (DWL) Paperboard,
Solid Bleached Sulfate (SBS),
Food Board,
Solid Unbleached Sulfate (SUS),
Representative Papermaking Machines
Paperboard Cartons
Paperboard provides a versatile and economical material not readily
matched by other packaging mediums,One significant advantage is
the low tooling cost compared with that for materials such as plastics,
Effective paperboard package design is based partly on knowledge
of paper and product properties and partly on craftsmanship and art,
Paperboard packaging can be considered in a number of categories,
Folding Cartons,Folding cartons are by far the largest and most
important group in paperboard packaging,Folding cartons are made
as flat blanks or as preglued forms that can be flattened for shipping,
They can be made economically on high-speed production
machinery,The majority of folding carton designs can be classified
as falling into either the tube-style (Figure 3.11) or the tray-style
design families(Figure 3.12),
Representative Papermaking Machines
Figure 3.11 A gable-top carton blank and an erected gable-top carton
Representative Papermaking Machines
Figure 3.12 A six-cornered Brightwood tray,flat and assembled
Representative Papermaking Machines
The gable-top container(Figure 3.11) is basically a tube-
style carton that has found many applications,
particularly for dairy products and fruit juices,The heavily
sized and polyethylene-coated board is erected and
heat-sealed at the point of fill,Combibloc and Tetra Pak
are similar-appearing proprietary cartons made from
complex paper/foil/poly laminates,A principal application
is for aseptic beverage packaging such as juice boxes,
Representative Papermaking Machines
Setup Boxes,
Setup boxes (Figure 3.13) are rigid cartons that are
delivered erected and ready for filling,
Setup boxes are not as amenable to high-speed
production as folding cartons,and their manufacture,by
comparison,is slow and labor intensive,
Setup boxes are typically constructed from a heavy,
low-grade chipboard with no particular folding or printing
qualities,In its most elementary form,the board is cut to
shape,and the sides folded up and taped with stay tape
to form a stayed box,
Representative Papermaking Machines
Figure 3.13 Examples of setup box designs
Representative Papermaking Machines
Tubs,Trays,and Liquid-Resistant Boxes,Paperboard
can be formed into round or square tubs with paper end
seals,Such forms,constructed from food board,are
used to contain such items as ice cream and frozen
foods,Flat sheets with gusseted corners can be folded to
form food trays for frozen entrees or other food products,
In most wet food applications,the board is coated with
either polyethylene or wax,Dual-ovenable paperboard
trays are coated or laminated with an oven-temperature-
tolerant plastic such as poly(ethylene terephthalate),
