Extrusion Coating & Laminating

2008 Extrusion Coating Short Course, May 1, 2008 Beth Foederer OtOptex PSltiProcess Solutions, LLC

Discussi on T opi cs

z Equipment and Purpose

z Chill Water System Design and Control

z Basics of Process

z Calculations

z TblhtiTroubleshooting Extrusion Coating & Laminating

The goal in extrusion coating and/or litiitflaminating is to form a con tinuous, inclusion free polymer layer of uniform thickness, that adheres to the desired substrate(s).

EtExtrusi on C oati ng U ses

z Milk Cartons z Sugar Pouch

z Ream Wrap z Cheese Wrap

z Juice Cartons z Snacks

z Snac k F ood z Dryyes Mixes

Packaging z Lidding Stock

z Photo Paper z Multiwall Bags

z Bakery Trays z Medical Packaging

Nip R o ll z What: Water cooled (generally double shell) roll with a rubber covering z FtiFunction:

z To combine the substrate(s) and molten polymer together at the chill roll with even pressure

z It removes air from the product

z It facilitates cooling

Nip R o ll z Operation z Opens and closes with either pneumatic air cylinders or air bags. z Pressure is changed by adjusting air pressure to cylinders or bags. z Typical pressure is 150 pli but can be higher. z Both rolls open for threading and safety Nip R o ll Cover ings z Hypalon (Chlorosulfonated Polyethylene)

z Shore hardness range: 40-90

z Good release, temp resistance, ozone resistance and easily reground z Neoprene (Polychloroprene)

z Shore hardness range: 15-80

z Regrindable, not as durable, good release, inexpensive z Silicone ((yPolymethy lsiloxane)

z Shore hardness range: 40-70

z Soft, v good release, temp resistance, good for porous substances

Nip Ro ll Re lease O pti ons

z Why do the edges need more release than center?

z Teflon® Tape

z Change for different widths

z Teflon® Belts

z Adjustable but difficult to use

z Teflon® Sleeves

z Costly Nip R oll Defl ecti on z Bending of the roll due to gravity, tension and pressure

z Backing roll helps the deflection

z Function of roll diameter and construction

z Can be measured by nip impression tape OR… z Corrected by crowning the roll

z Caution: improper crowning will generate wrinkles in the nip

BkiRllBacking Roll

z What: Water Cooled

z Chrome p la te ddd dou ble s he ll

z Increases the life of the nip roll covering z FtiFunction:

z Cools surface of nip roll to reduce sticking

z Re duces bow ing /de flec tion o ffth the n ip ro ll Str ippi ng R oll z What:

z Steel, aluminum or rubber covered idler roll z Opppyened and closed with pneumatic cylinders z Function:

z Initiate even removal of product from chill roll z Location:

z Metal roll is 1” or less from chill roll z Ru bber ro ll con tac ts c hill ro ll z Opens for threading and safety

z Is adjustable if a wide variety of products is to be made

Chill Ro ll Functi on

z QhltlQuench molten polymer to strippable temperature

z StSet ext rusi on li ne spee d– LdLead section

z ItftttfilImpart surface texture to final product (extrusion coating only) Chill Roll Const ructi on z Diameter range: 18-50 inches z Mono flow z In one end, out other z Single shell desgn z Small Rolls only – not Rdd!!Recommended!! z Double shell design z Small amount of water, next to outhllter shell z Double shell spiral fluted z Most common design z Lowest delta T

Chill Roll Fini sh z Surface roughness is a measure of the smoothness or texture of the roll surface

z Ra – “Average Roughness”

z RMS – “Root Mean Square”

z 10 Ra = 11 RMS z Surface roughness determines how easily the polymer can be removed from the roll and the surface finish of an extrusion coated product. Chill Roll Fini sh es z Matte – 30-125 Ra typical z Grit blasted, plated with dull finish and good release z Gloss – 4-10 Ra typical z Precision ground and polished with good surface finish and release z Mirror – 2-4 Ra typical z BlBelt or stone po lihlish w ihhihlithhigh gloss an d poor release z Optical Mirror – 1 Ra or less

MtMateri ilCalConsid erati ons z Heat Conductivity (k) – Steady state heat transfer rate within solid or liquid materials z Thermal Expansion – Fractional change in length or volume of material for unit temperature change z Durability – resistance to dents, scratches or deformation z Weight z Cost of raw materials and fabrication MtMateri ilSlalSelecti on Coefficient of Thermal Heat Conductivity** Material Expansion*

Aluminum 12.8 1460 Brass 11.4 833 Chromiu m 343.4 480 Copper 9.8 2670 Gold 7.9 2090 I(Iron(pure) 666.6 529 Nickel 7.2 421 Silver 10.5 2910 Steel(SAE 1020) 6.6 360 Steel(SAE 1095) 5.7 360 Steel 285 Grade B 6.5 - Stainless Steel(I8-8) 9.5 - *10e-6 in/in *°F **BTU-in /(°F –ft2 –hr)

Chill Roll Temperat ure z Whatd t do I need? z The ideal chill roll temperature is cool enoughht to all ow the coa ting to re lease cleanly, but warm enough so the polymer does not cool before having a chance to wet the substrate adequately. WtWater R eci rcul ltiation S yst em

z Usually a closed loop system

z Same water is chilled and re-circulated z CliCooling can be var idied

z Based on extruder output

z BhBy chang iting tempera ture of fll rolls z Water temperature is controlled

z Usually runs at 50-85oF

Closed looppy chill roll system

Makeup Water Temperature 50°F Controller 68°F 68°F Chiller Reservoir etc 3-Way Valve

50°F Pump T 68°F T T

65°F T

65°F Shut off Valve Pump T Thermometer Pump Chill Syst em F ouli ng

z What: Any layer or deposit of extraneous material on a heat-transfer surface. This reduces thermal conductivity of surface. z Causes z Scale or mineral deposits z Algae z Rust z Prevention z Initial system treatment z Maintenance program z Removal of build-up is either chemical or mechanical

Chill Roll Temperature

600°F Melt Temp. Contact time 0.24 sec

Shell= 12mm (0.5”) 1.0 mil coating 120°F Substrate 70°F in Line Speed o 1000 ft/min 73 FoutF out

450°F 230°F 340°F EtExtrusi on P rocess V ari iblables

z Polymer Melt Temperature

z Linespeed

z Air Gap/Drawdown

z Die Position Lead

z Die Gap (not discussed)

z Chill Roll Temperature

z Nip Roll Pressure

z Nip Roll Hardness OidtiOxidation ( melt ltt temperat ure)

z All substances are either organic or inorganic

z Organi c mat eri al s w ill burn

z High temperatures promote faster oxida tion ra tes

z At some temperature the ignition point will be reached.

Bd/AdhiBond / Adhesion z All organic materials have a surface skin

z This is an oxidized layer of itself (rust) z StilitidtihSome materials resist oxidation such as stainless steel z TO OBTAIN ADHESION BETWEEN TWO MATERIALS, ONE MUST BE LIQUID!!! z Too much oxidation destroys adhesion as does too little. Air Gap

z The amount of time the molten polymer is in contact with air effects its adhesion to the substrate. z The longer the polymer is exposed to air, the cooler it becomes and tends to decrease adhesion z If th e mel t temperature i s hig h enoug h, increase d time will increase oxidation and will improve adhesion z Therefore, an optimum air gap permitting maximum adhesion exists for each set of circumstances

BdBond versus Air gap

bond

air gap MltCMelt Cur titain Ai AiGr Gap z Determined by linespeed z Raising Die z Time in air gap increases z 100ms for LDPE z TIAG=60 x ggp(ap(mm ) / linespeed (m/min) z Neck-In increases z Melt temperature drops Air Gap Line Speed z 1” increase in gap = 10oF (in) (fpm) increase in melt 7.0 up to 700 8.5 700 – 1,200 temperature 10.0 1,200 – 1,800 12.0 1,800 and up

NkNeck-In z Determined by:

z Resin properties such as molecular weight and molecular weight distribution

z Extrusion conditions such as melt temperature, line spp,peed, output rate and die pressure

z Equipment geometry such as screw design, air gap and die lip gap Die Pos ition L ead z Lead onto either substrate for improved adhesion z Issues

z Substrate burn through

z Web contraction on heavy coatweights

z Linespeed will effect z Work needs to be done to optimize location Chill Ro ll Tempera ture Se tting z Too Cold produces rapid quench rate

z Reduced adhesion z Roll mayygy sweat in high humidity z Too Warm produces slower quench rate

z Polymer may stick to roll z Bond issues or tearing with substrate z Can wrap chill roll z Uneven Temperature

z Poor or uneven strippability z Flow marks in product z Indication that chill roll may be fouling

Chill Ro ll Str ip P ositi on

If Roll to High…. …Chill Roll Surface Cannot Recover CL

CL C L If Roll to Low…. Chill Roll CL ...Poor Stripability Resulting in Quality Defects

A misaligned or Worn Roll Can Result in Wrinkles in the Product Chill Roll Recovery

600°F Melt Temp. 90°F 100°F 120°F

B A

75°F The Chill Roll needs time and distance to recover cooling of its surface ( A to B ) Davis Standard

Nip I mpressi on

z Amount of impression determined by: z Roll Hardness Impression z Roll Diameter Width z Nip Pressure z Wider nip z Improved adhesion z For heavier substrates z CtihlCan create pinholes z Even nip across the roll is important!!! Quick Calculation for Chill WtWater GPM mwxCpwx¨Tw = mp(Cppx¨Tp+hfp) x Eff

mw = Mass Flow Water, lb/hr mp= Extruder Output, lb/hr

Cpw = Specific Heat Water, BTU/lb-°F Cpp=Specific Heat Polymer, BTU/lb-°F

¨Tw= Temperature Rise Water, °F ¨Tp= Temperature Change Polymer, °F

hfp = heat of Fusion Polyy,U/mer, BTU/lb Eff = Effeciency of System

GPM = [(mp x 0.75 x ¨Tp)/(¨Tw x 500)] x 1.2

How much water do we need to pump through our chill roll if we have a rate or 1000 lb/hr LDPE, Melt Temperature 600°F, a Strip Temperature of 100°F, and 3°F Water Temperature Rise?

lb BTU Btu BTU GPM = 1000 /hr (0.55 /lb-°F x (600-100°F)+0.48 /lb) / (1 /lb x 3°F x 480) * 0.7 = 275gpm

GPM = [(1000 x 0.75 x (600-100)/(3 x 500)] x 1.3 = 325gpm

*Assuming Chill roll is of adequate size **Increase GPM to allow for Nip and Backing Roll Flow

Quick Calculation for Cooling Tonnage

Ton = [mpx0.75x¨Tp/12,000] x 1.2

Mp = Extruder Outpp,ut, lb/hr

¨Tp = Temperature Change Polymer, °F Ton = Tonnage of Refrigeration required or available at 50°F 1.2 = Efficiency of 80%

How much cooling is required if we are extruding 1000lb/hr of 600°F LDPE with a stripping Temperature of 100°F.

Ton = [1000 lb/hr x 0.75 x (600-100)°F /12,000] x 1.2 = 37.5 Ton Chill Roll Cont actTi t Time

Calculate Contact and Recover Time and Length for a Extrusion Line Having a 24 inch Chill Roll with a 220° Wrap at a Line Speed if 500fpm.

Contact Time, sec = CR Diame ter x Wrap % Line Speed x 22.93 = 24 x 220 500 x 22.93 = 0.46 sec

Recovery Time, sec = CR Diameter x (1-Wrap%) Line Speed x 22.93

= 24 x (360-220) 500 x 22.93

= 0.29 sec

Chill Roll Cont actL t Length

Calculate Contact and Recover Time and Length for a Extrusion Line Having a 24 inch Chill Roll with a 220° Wrap at a Line Speed if 500fpm.

ContactLengthft=Contact Length,ft = CR Dia. x Wrap% 1376

= 24 x 220 1376 = 3.84 ft

Recoveryyg Length,ft = CR Dia. x 3.14/12 – Contact Length

= 24x3.14/12-3.84

= 2.44 ft Troubleshooting – Problems RltdtthLRelatedto the Lami nat or z A problem with it’s causes will be listed z Solutions are based on what we have gone over ithiin this presen ttitation. z Audience will give answers by filling out work bkbook as eac h pro bliblem is g iven. z Group discussion and review of solutions.

SltiSolutions W orkb kbkook

Problem #1 #2 #3 #4 #5 #6 Solutions Increase Air Gap DAiGDecrease Air Gap Chill Roll to Die (Left/Right) Increase Chill Roll Temperature Decrease Chill Roll Temperature Increase Nip Pressure Decrease Nip Pressure Change Stripper Position Chill Roll Fouled (Clean) Call Beth Pbl#1Problem #1 z Poor Adhesion of Extrudate to base or laminated substrate. z Due to: Inadequate oxidation only z There are two solutions related to the laminator for this problem

Pbl#2Problem #2 z Poor adhesion of the polymer to the substrate. z Due to: Premature Cooling z There are three possible solutions to this problem Pbl#3Problem #3 z Poor Adhesion of the Polymer to the Substrate z Due to: Sti cki ng t o th e Chill Ro ll

z There are two possible solutions to this problem

Pbl#4Problem #4 z Excessive Odor z Due to Over-Oxidation

z There i s one so lut ion re lat ing to t he lam inator for this problem Pbl#5Problem #5 z Poor Heat Sealability z Due to: Over-Oxidation

z There i s one so lut ion re late d to t he lam inator for this problem

Pbl#6Problem #6 z Poor Adhesion Across the Web z Adhesion is good in some areas and poor in others z Due to: Reduced Thermal Conductivity

z There are two possible solutions related to this problem and one is tricky!! CliConclusion z EiEquipmen t andP urpose z Chill Water System Design andCon tro l z Basics of Process z Calculations z Troubleshooting z Thanks to Optex Process Solutions, LLC