mdo films

5/21/2018 MDO Films

1/5

tretching film in the machine

direction magnifies its prop-

ertiesnot just a little, but

a lot. MD orientation of

blown and cast films,

whether off-line or in-line

with extrusion, enhances

barrier, stiffness, flatness,

tensile strength, and poros-

ity. It reduces stretchiness

and, of course, makes two orthree times more product

with the same amount of

plastic. Because MDO films

are also very flat, they run many times

faster in downstream converting oper-

ations, adding still more value.

Given all these advantages, why

arent there more MDO film products in

the market? Because most MDO films,

beyond a few relatively simple products

like monolayer stretch film, are very,

February 2005 www.ptonline.com48

very difficult to get right. For example,

MDO can enhance nylon and EVOH

barrier properties, but it also makes

them brittle. If you know how much to

preheat, how much to stretch, and

where to anneal, you can make a suc-

cessful product, cautions Kevin Hen-

derson, technical marketing manager

at Avery Dennisons Engineered Films

Div., Concord, Ohio.

Machine builders report a growingvolume of processors asking about

MDO equipment, but these processors

often dont have any idea of what they

need or of how difficult a challenge

awaits them. Over the years, at least

three major packaging companies

invested heavily to develop MDO

films and installed multiple production

lines, only to abandon them with little

to show for their effort and expense.

Most MD orienters are used as the

By Jan H. Schut, Senior Editor

S

MDO FilmsLots of Promise,Big Challenges

Machine-direction orientation is still

discovering new market opportunities. But

the technical difficulties are so great that

some big projects never came of age.

New equipment could make it easier.

5/21/2018 MDO Films

2/5

www.ptonline.com February 2005 49

on wide lines with high outputs. Mar-

shall & Williams (one of the major

equipment providers) has sold five of its

largest MDO units4 meters wide

for making hygiene films. Davis-Stan-

dard has also built its largest units2

meters widefor hygiene films. SMLin

Austria has built MDO lines for hygiene

films up to 3.2 meters wide.

Processors typically develop new

first stage in biaxial film and sheet pro-

duction. But stand-alone MDO units

have generated innovative film products

since the 1960s, such as PET strapping,

PVC food wrap, foamed PP ribbon, and

fibrous HDPE ribbon for weaving sacks.

MDO film hit the big time in the 1990s

with breathable hygienic films for dia-

per liners, self-adhesive labels, and syn-

thetic paper. These products were made

MDO film products on full-scale pro-

duction equipment or on home-made,

half-sized R&D lines. Either way, the

machine design is usually specific to one

product and offers little flexibility.

Although lab-scale MDO lines are avail-

able from M&W and Dr. Collin GmbH

in Germany, they are of limited use to

processors because they are too narrow

to make samples that converters could

Honeywells Aclar fluoropolymer film

gets better moisture barrier from

MD orientation, making it a clear

alternative to aluminum foil.

5/21/2018 MDO Films

3/5

February 2005 www.ptonline.com50

and number of cooling rolls.

The number of preheat rollers is

determined not by the amount of stretch

desired, but by the resin and intended

throughput ratemore rollers, more

throughput. Standard preheat-rolldiameters are 12, 18, or 24 in., though

they can get as big as 30 in. Film can

be drawn once or multiple times, punc-

tuated by intermediate heating or

cooling to obtain different effects. Draw-

ing can be done hot or cold.

Drawing is relatively straightfor-

ward. A fast-draw roller turns faster

than a slow-draw roller by a specified

amount, stretching the film in the gap

between them. You just have to find

the right temperature and draw ratio,

and that can be a pain, says Eric Hat-

field, managing director of operations

at FlexTech Packaging Inc. in Cincin-

nati, which specializes in MDO films.

Short-gap stretching is typically

less than 2.5 mm, long-gap stretching

is 5 to 50 mm or more. There is evenso-called zero-gap stretching or

compression-roll drawing. The shorter

the gap, the less film neck-in occurs.

Neck-in typically reduces film width by

5% to 20%. Neck-in also reduces the

breathability that is critical to hygiene

films. SML patented the use of rubberdrawing rolls that reduce neck-in.

Annealing is the hardest part, says

Flex Techs Hatfield, because film can be

made to stretch or shrink by speeding

up or slowing down the annealing rolls.

Any change in speed or temperature

changes the resulting film properties.

MDOs ability to downgauge film

and improve its properties at the same

time is a compelling combination. Down-

gauging is a large part of why proces-

sors try so hard to make MDO work.

Honeywell Specialty Materials took sev-eral years to develop an MDO version of

its Aclar monolayer PCTFE fluoropoly-

mer film to replace metal foil with a clear

moisture barrier. Honeywell found that

monoaxially stretching Aclar film dou-

bled its moisture barrier, so 25-micron

MDO Aclar has the same moisture bar-

rier as 50-micron unoriented Aclar.

MDO Aclar is close to its first com-

mercial use in a pharmaceutical pack-

age. The film is made in

Pottsville, Pa., on three

high-temperature ori-enters from Marshall &

Williams with oil-

heated rollers that can

go up to 600 F.

Stretchingblown film

In the past few

years, the pace of new

MDO film develop-

ments has picked up,

especially those based

on blown film. Machinebuilders have respon-

ded to that interest with new hardware

designs.

Bruckner Maschinenbau GmbH in

Germany, inventor of some of the earli-

est biaxial stretching technology, has

now taken an interest in MDO. Last

year, Bruckner set up a new group to

design and build monoaxial stretching

lines for barrier and shrink films. Acom-

pany spokesman notes that these films

are gaining more and more signifi-

cance in the market.Several builders of blown film

test on full-size converting machines.

Some resin companies, however, have

found lab MDO lines useful.

There are also monoaxial films that

are stretched only in the transverse

direction to make products like shrinklabels. But TDO systems can be even

more limited in product flexibility than

MDO units.

In the past year or so, there has

been a small but significant change in

the flexibility of MDO equipment.

Processors have bought full-sized pro-

duction orienters with extra features

intended purely for R&D. These orien-

ters not only control the temperature

and speed of every roller individually,

they offer multiple web paths and mul-

tiple draw options. This uncommonlevel of flexibility should make new film

product development easier.

Too many choices?MDO equipment can have an

almost unlimited number of variables:

the number and temperature of preheat

rollers (two to a dozen or more); the type

of roll heating (water, oil, or electric); the

size of the gap between S-wrapped draw

rollers (up to 2 in.); how many times film

is drawn (one to three or more); tem-

perature and dwell time for annealingor heat-setting; and the temperature

MDO FILMS

Black Clawsons center-opening vertical

MDO unit is self-threading and easy to

reconfigure, even with different roll sizes.

5/21/2018 MDO Films

4/5


machinery have also entered the MDO

market with starter units. Addex Inc.,

for example, is building its first MDO

unit now. Dubbed MDO Light, it will

stretch coex blown film very slightly

around 3%to flatten its inherent bag-giness. MDO Light is only a four-roll

system with two 20-in. diam. heating

rolls and two 20-in. cooling rolls, all indi-

vidually driven. Tension control on the

four rollers is accomplished not with

load cells, but with fiber-optic tracking

of roll diameter, rpm, and torque.

The first of these units ships this

month to Polyexe Corp. in Brentwood,

N.H., to flatten an unslit tube of three-

layer coex PP film with a layflat of 40

in. After flattening, the film runs many

times faster through a silicone-coatingprocess. Silicone-coated release films

are a growing market for protective

backings for labels, adhesive ban-

dages, and diaper tabs.

Polyexe plans to use its MDO

Light line to develop other products

with more stretch. Well see how

much more the machine can do,

says Oliver Zoellner, technical direc-

tor. We intend to play with it.

Other blown film machine

builders have launched their own

MDO orienters. Hosokawa Alpinehas supplied a dozen MDO units to

processors in Europe, South Amer-

ica, and Asia. The first went to a

processor in France, where it runs

in-line with extrusion after the tube

is slit. That system requires two

MDO units, one for the top web

and one for the bottom. Alpines later

MDO units are used off-line and

need only one orienter.

Alpine uses individual servo drives

for heating, annealing, and cooling

rollers, any of which can be used tostretch the film. They all have individ-

ual tension control to take up both the

films expansion during heating and

its contraction during cooling, so as to

avoid wrinkles and buckling. Individ-

ual roll temperatures are needed for

coex films, where a seal layer requires

lower temperature than other layers.

At last years K 2004 show in Dus-

seldorf, Alpine demonstrated off-line

MD orienting of film fed from rolls. One

film for heavy-duty HDPE sacks was

stretched 6:1 (gauge started at 240microns and finished at 80 microns),

while a coex HDPE film for stand-up

pouches was stretched 4.5:1.

Battenfeld Gloucester Engineering

developed an MDO unit for pre-

stretched mono- and multi-layer

LLDPE hand-wrapping stretch film. Itsfirst commercial model went to a Euro-

pean processor that orients a collapsed

tube with up to 70-in.-wide layflat.

Macro Engineering & Technology

also built its first MD orienter for blown

pre-stretched (hand-wrapping) stretch

film. It orients a collapsed bubble but

uses cold drawing, which requires a

triple draw and long gap. The collapsed

bubble thins after orienting, but is

stronger because it has two layers that

are left stuck together in the finished

product. Cold drawing achieves a spe-

cial property of frozen elasticity, Macro

explains. It takes very little stretch later

to release the pent-up tension. So if a

hand-wrapper exerts 5% stretch, the

film will shrink back 20%.

Blown film vs. castMD orienters are used with cast

and blown film, but the properties and

product range are very different. M&W

says most of its blown film MDO units

are used to make diaper film. MDO castfilm is splittier in the TD than blown

film, since cast film has no initial orien-

tation. But sometimes splittiness in one

direction is desirable for films that need

a zip strip. Cast film can also be

thicker, and its gauge control is tighter.

Blown film, on the other hand, hasan upper limit on starting thickness of

about 10 to 15 mils, so after MD orient-

ing, it can be very thin indeeddown

to 0.2 mil (5 microns). Blown film also

starts with an inherent degree of biax-

ial orientation, so when strength is

needed in an oriented film product,

blown film may be the better choice.

FlexTechs blown film No. 2455 is

a paper substitute that needs biaxial

strength. It flies through printing and

converting machinery faster than paper

because orienting makes it so flat andstiff. No. 2455 is an asymmetrical

five- or seven-layer barrier film of

nylon and HDPE. Its used for stand-

up pouches of muffin mix.

Trico Industries, North Kings-

town, R.I., MD-orients cast film in

line with extrusion to make specialty

films for graphic arts and packaging,

where gauge control is critical. The

owners hail originally from M&W but

build their own machinery.

Avery Dennison in Painesville,

Ohio, makes MDO cast film for self-adhesive labels. Monoaxial stiffness

makes the labels dispense easily

because they are stiff in one direction

to enable easy peeling of the protec-

tive backing. At the same time, MDO

labels are soft in the transverse direc-

tion, so they conform well to rounded

shapes like bottles. Avery Dennison

has four MDO lines making oriented

label films in Painesville and Concord.

Says Kelly Williams in market

development for flexible packaging at

Equistar, another alternative would beMDO sheet extrusion. If you MD ori-

ent sheet, you can put out a lot more

pounds and eliminate the need to lam-

inate films for stiffness, Williams adds.

Equistar is working now with an MDO

equipment maker that also has sheet

extrusion technology.

Adding flexibilityEquipment suppliers are building

new MDO units with much more flexi-

bility than in the past. Models designed

for product development are being con-figured with multiple web paths; one-,

Marshall & Williams unusual lab line is

capable of three different draw modes.

Similar flexibility is being built for both in

production and R&D.

5/21/2018 MDO Films

5/5


Material mattersThe draw ratio of MDO film is lim-

ited by the polymer: roughly 2:1 for poly-styrene, 4:1 to 5:1 for LLDPE, 5:1 for

nylon, 6:1 to 7:1 for polypropylene, and

8:1 to 12:1 for HDPE. (HDPE homopoly-

mer can achieve 10 times the stiffness

of BOPP.) PP stretch can be extended

to 8:1 by using copolymers or blending

in some metallocene PE. LDPE isnt

often MD oriented because its broad

molecular-weight distribution gives it

too little tensile strength.

Resin suppliers are becoming more

interested in MDO, which achieves

properties that biaxial orienting cantmatch. MDO can improve EVOH bar-

rier properties, whereas biaxial orient-

ing destroys them. MDO HDPE has

great deadfold properties, which dis-

appear if the film is biaxially oriented.

Equistar Chemicals just bought a lab

MDO machine from Dr. Collin and has

created a computer model of how

MDO enhances films physical proper-

ties. Equistar is using this software to

develop new bimodal HDPEs for MDO

applications.

Bimodal HMW-HDPE allows awider range of drawing conditions and

higher draw ratios, Equistar says, such

as 12:1 or 13:1 draw instead of the usual

10:1. At such extreme draw ratios, struc-

tural changes occur in the polymer,

enhancing film properties, says Ryan

Breese, product development engineer.

MD orienting can open pores that

impart breathability to products like

hygienic liners for incontinence pads.

Such films are filled with calcium car-

bonate and other minerals. After MD

orienting, the film is shocked with a

chill roll, and then MD oriented again

to a much greater extent to open up

porosity by pulling the polymer away

from the filler particles.

A similar porosity effect occurs

when stretching film that contains hard

spherulites or beta-formation crystals

that form during annealing. The crys-

tals can be controlled to open pores of a

particular size when the film is

stretched. Depending on the crystal size,

stretching leaves film that is clear, hazy,

white, or pearlescent. Avery Dennison

uses the smallest crystals to create clar-

ity in its latest MDO label film, a coex

PP grade called GCX.

two-, and three-draw options; and self-

threading for safety. M&W is building

its most complex orienter ever. It com-

bines three styles of stretchingsingle

draw, dual draw, and zero draw gap

under compressionas well as indi-

vidual temperature and speed control

on all preheat, annealing, and cooling

rollers. The orienter is being built for

both production and R&D use.

The Zero Gap feature on this

machine is a new technology licensed

from ITW Signode and introduced last

year by M&W. Zero Gap stretching

takes place under compression between

two counter-rotating draw rolls. Itresults in less neck-in and some biax-

ial orientation, M&W says.

Vertical orienters are also being

built with new features for added flex-

ibility. Two years ago, Black Clawson

built its first vertical MD orienter (with

a 9-ft tower) and has delivered three so

far. Their vertical format is self-thread-

ing and more accessible to operators.

M&W built its first vertical MD orien-

ter in 1995 and says about 20% of its

MDO units now are vertical. Battenfeld

Gloucesters MDO unit is also a verti-cal self-threading design.

PT

NEED TO KNOW MORE?For more information, enter PTDirect code atwww.ptonline.com

Addex Inc., Stoughton, Mass.(781) 344-5800 PTDirect:274WX

Battenfeld Gloucester Engineering Co.,Gloucester, Mass.(978) 281-1800 PTDirect:837KP

Black Clawson Converting Machinery Inc.,Fulton, N.Y.(315) 593-0396 PTDirect:683CT

Bruckner Inc., Greenville, S.C.(864) 234-7111 PTDirect:343TF

Davis-Standard Film & Coating Systems,Somerville, N.J.

(908) 722-6000 PTDirect:151JBDr. Collin GmbH, Ebersberg, Germany+49 8092 20 96-0 www.drcollin.de

Equistar Chemicals, Houston(713) 652-7300 PTDirect:189PB

Hosokawa Alpine American, Natick, Mass.(508) 655-1123 PTDirect:664YD

Macro Engineering & Technology Inc.,Mississauga, Ont.(905) 507-9000 PTDirect:597VB

Marshall & Williams Plastics, Woonsocket, R.I.(401) 765-7770 PTDirect:627FK

SML Extrusion Technology Inc., Kennesaw, Ga.(770) 924-0991 PTDirect:756DM

Addex is introducing MDO Light, a four-roll MDO system that reheats blown film

and stretches it just enough to flatten it for faster downstream converting.

MDO FILMS

mdo films

Documents