1 Flexible Packaging Laminates Lesson 8 8. 2 Plasticating Extruder Fig. 10.2.

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Flexible Packaging Laminates

Lesson 8

第 8 课软包装复合材料

Plasticating Extruder

E x itport

G ear reducer

Variab le speed m o to r

F eed throa tF eed hopper

H opper throa tC oo ling jacket

S crew

H ea te r bands

Fig. 10.2

Adjustable D ie Lips

Extrusion D ie

Adjustable P ressure (Restrictor) Bar

Extruder

Cast Film and Sheet Extrusion

Fig.10.4

Extruder #1

Extruder #2

Extruder #3

M ateria l #1

M ateria l #2

M ateria l #3

Three-Layer Coextrusion

Fig.10.9

Extrusion Cast Film Line Layout

E xtrude r

E x trus ion d ie C h ill ro ll

E dge trim m er

M ate ria l ro ll

Fig.10.5

Machine Direction Orientation

R otation x 1 x 3x 2 X 4

From extruder casting ro lls

Fig.10.8

E xtrude r

C asting R o lls

A nnea ling Zone

E xtrus ion D ie

Ten te r C lips

Cross Direction Orientation

Fig.10.8

B ubble

B low -up a ir in le t

C oo ling a ir C oo ling a ir

P las tic from extrude r

D ie lip ad jus ting bo lts

D ie B ody

D ie co re

F rost line

B ubble cons tantly pu lled up

Blown-film Die Cross-Section

Fig.10.6

Three-layer Extrusion Blow Mold

Cut-away view

material 1

material 2

material 3

film bubble

E xtrude r

C ircu lar d ie

A ir ring

In te rna l bubb le coo ling

P las tic film bubb le

C o llapsing fram e

U pper n ip ro lls

S litte rD ua l ro ll w inde r

Blown Film Line With Slitter

Fig.10.7

Blown Film Line Showing Die & Bubble

Aluminum Foil

Household foil is typically 17.5 m (0.0007 inches)

Available in gauges as low as 7 m (0.00028 inches)

Pin holing is present below 12 m (0.0005 inches)

Foil is susceptible to flex cracking

Most foils are supported with plastic and/or paper

Unsupported foil used for some lid-stock & tablet push-through packaging

Intact foil is a 100% barrier to all gases

Best deadfold properties

Easily punctured (tamper evidence)

Reflective of radiant heat

Conductive (induction sealing)

Decorative appeal: all reflective metallics are aluminum

Aluminum Foil Characteristics

Foil Packaging Applications

Unsupported foil, non-sealablee.g. confection and cheese wraps

Unsupported foil, heat sealablee.g. lidding stock, pharmaceutical tabletbacking material

Supported foil, non heat sealablee.g. decorative wraps, label stock

Supported foil, heat sealablee.g. high barrier pouches and sachetslidding stock, retort pouches

Aluminum Vacuum Metallizing

Fig.14.1

Vacuum line

U nw ind ro ll

A lum inum vaporC eram ic boat

R ew ind ro ll

A lum inum w ire C hilled ro ll

Provides reflective metallic appearance

Improves moisture, aroma, light and oxygen barrier

Oxygen barrier improved: up to fifty times for OPP, up to ten times for PET

Static dissipative applications

OPP, PET, & PA (nylon) most common packaging films

Aluminum Metallized Film

Why Laminate?

There is no perfect, universal packaging material

Laminates assemble materials with individually

desirable properties to create an optimum material

Laminate: A product made by bonding together two or more materials

Mechanical properties

tensile strength stiffness

coefficient of friction use temperatures

elongation formability

Laminate Properties

Barrier properties as required

oxygen barrier essential oil barrier

water vapor barrier light barrier

Laminate Properties

Sealabilitymost flexible packaging is heat sealed

most heat seals are polyethylene based

other polymers used more critical applications

Aesthetic appearance

clarity

surface gloss

reflective metallics

Describing Packaging Laminate

Packaging laminate plies are always listed from the outside to the inside

Gravure Coating

Fig. 14.8

Wet Bond Laminator

Fig. 14.10

23Fig. 14.11

Dry Bond Laminating

Solventless Laminating

Solventless laminating uses catalyzed or or two-part reactive adhesives

Extrusion Laminating

Fig. 14.9

Extrusion d ie

C h ill ro ll

Substrate A

Substrate B

S trip -o ff ro ll

P ressure ro ll

N ip ro ll

Extrudate Three p ly lam ina te

Hot Tack

The bond strength of the seal while still hot

Critical for most form-fill-seal machines

Determines how quickly product can be dropped into a pouch

Common Heat- Seal Materials

costbond quality

ionomer (e.g. Surlyn, seals through contaminants )

acid copolymer (good foil bond, chemical resistance)

metallocene polyethylene (low temp, fast seal)

LLDPE (good hot tack, tough, wide seal temp.)

PE/EVA (soft film, low seal temperature)

medium-density polyethylene (stiffer, better barrier)

cast polypropylene (stands higher temperatures)

low-density polyethylene

Table 14.5

Source: M. Lutterotti, DuPont

Sealing Mediums Compared

120 125 130 135 140 150145 160 170 180

Oct. LLDPE

m PE F orce g / inch

Tem pera ture (deg rees C )

Hot Tack Strength

Figure 14.6

Heat Sealing Parameters

Fig. 14.7

Increasing Tem perature

H igh barpressure

M edium bar pressure

polyethylene

poly(ethylene terephthalate)

sealing medium

printed paper

sealing medium

Retort pouch Aseptic box

sealing medium

printed polypropylene

metallized polypropylene

Snack food bag

saran-coated nylon

sealing medium (Surlyn)

Luncheon meat tray

Example Laminations

See Figures 14.13 & 14.14

printed polyethylene

polyethylene

Ethylene-vinyl alcohol

High oxygen barrier

polyethylenepoly(ethylene terephthalate)

sealing medium (vinyl)

overlacquer

Single-service lidding stock

printed foil

Example Laminations

See Figures 14.13, 14.14

(For barrier applicationsfoil to the inside)

surface print

polyethylene

sealing medium

Basic food pouch laminate

Laminateroll stock

Highbarrierinsert

Finished tube1

Injected molded tip

Laminated Collapsible Tube Construction

Formed body

Clear LDPE

Sealing medium

Printed white PE

Vertical Form-Fill-Seal (VFFS)

Fig. 14.2

U nw ind

P roduc t flow

D raw -dow n be lts

Long itud ina l sea ling jaw

C ross-sea ling and cu t-o ff

F o rm ing co lla r

CoF is critical!

VFFS Pouch Seals Compared

Fig. 14.5

Fin seal Lap Seal

Seals inside surfaces

Uses more material

Don’t cover UPC!

Seals outside to inside

Both surfaces need sealing medium

Use less material

Horizontal Form-Fill-Seal (HFFS)

Fig. 14.3

U nw ind

Tens ion contro l

F o rm ing p low

Top sea l

C u t-o ff

O pen pouch

F ille r #1F ille r #2

F ille r #3C lose pouch

S ide sea l

Common HFFS Pouch Styles

Fig. 14.5

Conventional pouch has three-side seal

Can be made into various stand-up designs

Some stand-up pouches are pre-made in a separateoperation

Three-side sealed pouch

Gusseted designs

Multi-Lane Form-Fill-Seal

Fig. 14.4

Vertica l hea t sea ls H orizon ta l hea t sea ls

P roduc t d ispensers

F our-s ided sea l pouches(separated )

Stand-Up Pouch Examples

Film Thickness Measurement

Inch Gauge Mil Micrometre

0.001inch = 100 gauge = 1 mil = 25 m

0.0005 inch = 50 gauge = 1/2 mil = 13 m

ISO metric notes:“Micron” is a depreciated term for micrometre

one inch = 25.4 millimetres and

0.001 inch = 25.4 micrometres

Early Universal Barriers

PVDC is original high universal barrier polymers

EVOH laminated between high moisture barrier

polymers can also provide good universal barrier

But not high enough barrier for critical applications

Metallizing also produces a high universal barrierBut aluminum metallized films are not transparent

Recent Advances in Achieving Barrier

Monolayer polymers

poly(ethylene naphthalate) ($)

liquid crystal polymer ($$$)

Multilayered constructions

PET/PA/PET

PET/EVOH/PET

PET/MXD6/PET/ MXD6/PET

Recent Advances in Achieving Barrier

Interior coatingsSiOx (glass) coating (Glaskin)AlOx aluminum oxide coatingcarbon coating (DLC and Actis)

Exterior coatings and interior laminatesepoxy-amine coating (Sealica and Bairocade)copolyester (Amosorb: interior layer)

Nanocompositesextremely fine mineral additions

1 Flexible Packaging Laminates Lesson 8 8. 2 Plasticating Extruder Fig. 10.2.

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