(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`
`0601
`
`EX1008 (Part 3 of 3)
`Yita v. MacNeil
`IPR2020-01139
`
`

`

`8.2 Forming Thin Films
`
`585
`
`
`
`Nip Rolls
`
`Double Bubble
`
`
`
`Collapsing Frame
`
`Blown Film Bubble
`
`
`
`Frost Line
`
`
`
`External Air Fling\.
`
`Entrudar
`
`
` fill——- Internal Air Inlet
`
`Figure 8.! Typical blown film tower with optional double bubble stretching section [2]
`
`Regrind is difficult to accommodate in calendaring, and dirt, gels and contamination
`can be a problem.
`Films are also produced by solution casting. Any polymer that can be solvated or
`dissolved in a carrier can be cast
`into film. Typically, polymers that cannot be
`extruded or melt processed are solution cast into films. Examples include polyirnides.
`polyazoles and latexes. Solution casting is usually a manual batch process although
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0602
`
`0602
`
`

`

`586
`
`Producing Sheet and Film
`
`[Refs. on p. 644]
`
` Two-Flo“ Mill ° o
`
`“L" Calender Roll Stack
`
`Inverted "L" Calender Roll Stack
`
`Figure 8.2 Two calendaring roll stack configurations. Redrawn from [3] and used with permission of
`copyright owner
`
`fiwrfionum {lll’ ‘IHI’
`
`00.
`0
`
`"F” Calender Roll Stack
`
`"Z" Calender Roll Stack
`
`or copyright owner
`
`Figure 8.3 Two calendaring roll stack configura—
`tions. Redrawn from [4] and used with permission
`
`the resulting films are quite
`latex casting has been automated. With proper care.
`uniform in thickness and properties. Films having thicknesses of 1 mil, 0.001 in or
`25 pm or less are common. Solvent cast films are usually quite expensive. Residual
`solvent can be a serious problem during reheating of the film in the forming
`operation.
`Thin films are also needed when coextruded sheet is required. In this case. the
`polymer is melt-extruded with a secondary extruder into a special multilayer die. This
`is discussed below.
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0603
`
`0603
`
`

`

`The criteria for judging the quality of thin films are the same as those for heavier
`gage sheet. These are discussed below. With thin films,
`there is a greater concern
`about gels. fish—eyes and other occlusions in the sheet simply because the dimensions
`of these defects may be equal to or greater than the thickness of the film.
`
`3.3 Forming Sheet
`
`587
`
`8.3 Forming Sheet
`
`As noted, calendering is used to produce thin-gage sheet to 50 mils, 0.050 in or
`1250 um in thickness. Its use is usually restricted to polymers that require fluxing or
`masticating and those that are thermally sensitive. Polyvinyl chloride is the domi-
`nant polymer produced as calendered sheet. High molecular weight polymethyl
`methaerylate is sought for clarity and chemical resistance in pools, spas, shoWer
`stalls. and most glazing applications. It is produced by cell casting [5]. Generally,
`methyl methacrylate monomer with its hydroquinone inhibitor removed is mixed
`with benzoyl peroxide catalyst and heated to Bio-95°C. The catalyzad syrup is cast
`between two highly polished plates separated by flexible polyvinyl chloride or
`polyvinyl alcohol gaskets. The plates are held against the gaskets with carefully
`calibrated spring-loaded clips since the polymer increases in density or decreases in
`volume as its molecular weight increases. Temperature is maintained at 40°C early
`in the polymerization but gradually raised to 95-97°C after several hours to allow
`the polymerization to proceed to completion. The sheet
`is then cooled to below
`40°C. removed from the plates and annealed for up to 2 hours at 140°C to minimize
`internal stresses.
`
`Although the original batch process is still used to produce sheets with special
`sizes and thicknesses or acrylics that are lightly crosslinlced, the continuous cell-cast
`process dominates the production of most commercial glazing acrylic sheets. The
`continuous process uses a monomerXpolymer syrup containing up to 20% high-
`molecular weight polymer. Although the abrasion and chemical resistances are
`thought
`to be somewhat
`inferior to the batch cell-cast product,
`this product
`is
`substantially less expensive. Continuous cell-cast acrylic can also be croSslinked to
`improve impact strength. With proper temperature control, lower molecular weight
`polymethyl methacrylate pellets and granules are extruded into sheets using conven-
`tional single-screw extruders. Such products have lowered abrasion,
`impact and
`scratch resistances and may not have the surface quality and clarity of higher
`molecular weight acrylics. And extrusion—grade acrylics are usually not crosslinked.
`Extrusion through a slot die is
`the primary method of producing sheet
`of thicknesses from 10 mils, 0.010 in or 250 pm to 500 mils, 0.500 in or 12 mm
`or more. Table 3.2 lists the scope of continuous screw extrusion techniques.
`Plasticating single-screw extruders and twin-screw extruders dominate production of
`sheet for thermoforming. 0f the rest, two-stage and tandem extruders are used to
`produce foam sheet. This is covered in some detail in Chapter 9 on forming foam
`sheet.
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0604
`
`0604
`
`

`

`538
`
`Producing Sheet and Film
`
`[Rem on p. 644]
`
`Table 8.2 Types of Continuous Screw Extrudel’s
`Multi-screw extruders
` Singlescrew extruders
`
`
`
`Melt feel or plasticating
`Twin screw
`Single stage
`Gear pump
`
`Multistage
`Planetary gear
`
`Plastic
`Multi-screw (>2)
`Rubber
`
`
`Single~Screw Extrusion
`
`Figure 8.4 is a cut-away schematic of a conventional single-screw extruder. The basic
`elements are:
`
`Constant diameter {lighted screw.
`Constant bore barrel,
`Zoned heater bands,
`Keyed bearing block,
`Feed hopper.
`Venting ports,
`
`Barrel Screw
`
`92 . W4WW/I/IA
`!IE!“EEE-EE-EE'MAEE‘JEII‘IUTl
`Gear Box WI/f/I/IJ/M/f/I/I/Z/I/M/fl
`
`Healer Band
`
`\\\
`
`Figure 3.4 Schematic of single-screw extmdcr for [hemoplastics
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0605
`
`0605
`
`

`

`8.3 Forming Sheet
`
`589
`
`Table 8.3 Typical Compression Ratios SinglehScrew
` Extruders
`
`Polymer
`
`Compression ratio
`
`Regrind polyethylene flufl'
`Polyethylene powder
`Regrind polystyrene foam
`Other amorphous powders
`Polypropylene pellets
`PVC pellets
`Polystyrene pellets
`ABS pellets
`Crystalline PET pellets
`Polyamide (nylon) pellets
`
`4.5:l
`4.8:1
`4.0:]
`3.5:]
`3.th
`2.5:1
`2.511
`2.5.1
`2.01]
`l.S:l
`
`a Electric motor,
`
`Power coupling between motor and flighted screw, and
`a
`0 Temperature and speed controls.
`
`The most common screw is single-flighted. The screw serves to advance the polymer
`from the hopper to the die end. compressing, melting and increasing the pressure on
`it as it advances. The screw root increases along the screw. compressing and pressing
`the polymer against the heated barrel inner wall. The amount of compression is the
`compression ratio. Table 8.3 gives typical compression ratios for some polymers. The
`function of the screw is intellectually divided into three segments (Fig. 8.5) [6]:
`
`o
`
`Solids conveying, where the plastic pellets or powder is augered from the hopper
`into the barrel. Energy transfer to the polymer is minimal. Friction between the
`semi-solid polymer and the barrel and screw surfaces dominates. Typically the
`screw root dimension does not change in this zone.
`
`Motoring Section
`Transition Section
`Food Section
`r-—————-i-——-i-—————~l
`
`Shank
`
`Channel 999*"
`
`Screw Diameter
`
`\
`
`
`Iomis-sn\‘,\_n\‘\wmswm‘\u\smmw»
`
`Screw Tin
`
`
`Screw Flight
`
`Helix finale Screw Root Screw Flight
`
`Channel mum
`
`Figure 8.5 Schematic of screw for single—screw extruder with identification of various screw ele-
`ments. Redrawn from [6] and used with permission of copyright owner
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0606
`
`0606
`
`

`

`590
`
`Producing Sheet and Film
`
`[Refs on p. 644]
`
`Molten Polymer Film
`
`Barrel
`
`se\\\\
`
`
`
`Mall Pool
`
`Solid Polymer Granular Bad
`
`Screw
`
`Figure 8.6 Schematic of the interrelationship of solid and melt polymer and screw and barrel in the
`plastication region for single—screw extruder [7]
`
`0 Monitoring or melting, where the compressed cake melts against the barrel surface
`and the melt is continuously conveyed into a pool at the front of the trailing flight
`(Fig. 8.6) [7]. In this zone, the screw root dimension linearly increases.
`0 Mel: pumping, where the molten polymer is homogenized and compressed to build
`pressure necessary to flow through the extrusion sheet die. In this zone, the screw
`root dimension remains constant.
`
`These extruders are usually described in terms of screw diameter and the screw
`length—to—diarneter ratio, L/D. In the US, screw diameters are given in inches as 1,
`1%, 2, 2%, 3%, 4%, 6, 8. 10, 12 and so on. In Europe and other metric areas, screw
`diameters are given in mm as 20, 25, 30, 35, 40, 50, 60. 90, l20. I50 and so on. LID
`ratios are as low as 12:] to 16:1 for rubber and thermoplastic elastomeric polymers
`to 20:1 to 36:1 for most commercial extruders to 48:1 for certain olefinic extruders.
`
`24:1 and 30:1 extruders make up the bulk of sheet extrusion capability in the US
`while most European extruders are typically 30:! to 36:1. Increased LJD allows for
`improved solids conveying and melt homogenization but increases the residence time
`and shear history on the polymer melt. Table 8.4 gives an overview of the capacities
`of extruders of various diameters [8]. Extruder throughput rates are also dependent
`on the type of polymer, as seen in Table 8.5 [9]. These rates represent extruder
`capacity when the flow rate through the die is not controlling. This is the case for
`most heavy-gage sheet extrusion. For thin-gage sheet extrusion, on the other hand.
`extruder throughput rates may be reduced by flow resistance through the die, as seen
`in Table 8.6 for the extrusion of 15 to 80 mil, 0.015 to 0.080 in or 400 to 2000 um
`flat sheet of certain polymers [10]. Example 8.1 shows the relative output for a given
`extruder screw diameter.
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0607
`
`0607
`
`

`

`8.3 Forming Sheet
`
`591
`
`Table 8.4 Typical Extruder Capacities [8]
`
`Extruder size
`Barre] heater
`Average power
`
`
`
`
`Output
`{HP}
`(kW)
`
`(lbih) tksth}
`
`
`
`
`
`7.5
`23 .74
`50—75
`1g
`IU-IS
`
`
`
`21
`54—73
`2'i
`20—30
`120-160
`
`
`45
`113- 131
`3‘2
`40—15
`250—400
`
`75
`131-313
`4;
`30 I25
`400—700
`
`
`
`:40
`363--544
`6
`150 225
`soc—1200
`
`1500—2000 225 asohsm
`
`s
`300—500
`
`
`
`
`
`Example 8.1 Extrusion Capacity
`
`Your thermoformiflg operation requires 40 in x 52 in x 0.060 in ABS sheet. Deter-
`mine the number of 100 sheet pallets that can be produced from o 4-t'n extruder.
`Compare the output with the maximum output of that extruder. Determine the
`weight of each potter.
`
`From Table 8.6, the tlg-in extruder with a sheeting die can produce 1320 to
`1430 lblh ABS. The specific gravity of ABS is 1.05 gtcm3| = 65.5 lblft3. Thus
`the volumetric output is 20 to 22 ft3lh. The volume of each sheet is I243
`in3=0.0?2 ft3. Therefore the extruder will produce 275 to 300 sheets per
`hour or 2.?5 to 3 pallets per hour. The plastic on each pallet weighs 4'30 lb.
`According to Table 3.5, a iii-in extruder can plasticate 1170 to 1430 Ibg‘h.
`Therefore, the extruder with a sheeting die is running at maximum capacity.
`
`Many single-screw cxtruders have venting ports or vents at some location along
`the barrel. Some polymers contain small amounts of volatiles. These are removed
`prior to the sheeting die to eliminate foaming and to minimize microbubbles. pits and
`pores in the finished sheet. Venting screws usually have a decompression or let-down
`region just ahead of the vent. as seen in Fig. 8.7 [l l]. Vented or devolatilizing
`cxtruders usually have LtDs of 30:1 or more. Although vents can be plugged and the
`extruder run unvented, the screw is usually not optimum and so the polymer may be
`subjected to higher than normal shear and residence time at melt temperature. Vented
`extruders should not be used to dewater polymers. Polymers having high moisture
`level potentials should be thoroughly dried prior to being charged to the extruder.
`
`Filtering the Polymer
`
`A filter screen is usually placed between the end of the extruder and the die to catch
`contaminants. unmelted polymer and some gel particles. The generic screen is a plate
`with regularly spaced holes. Screens with different sized holes are usually grouped
`together to form a screen pack. A typical screen pack might have several 100 mesh
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0608
`
`0608
`
`

`

`592
`
`Producing Sheet and Film
`
`[Refax on 1:. 644]
`
`
`
`
`
`
`
`SEAN:82-8%camiowesalsa.2218933.8%enemies8:.8:
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`
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`ana?2:129as.as33.82Balm?8218280.0%23-2.:
`
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`soa?32.85a;Eh2:13.:3.78...83133Elma3722
`
`
`
`
`
`
`
`
`
`8m.02.83-32Enigmacan83226%onmmifimm027:5Smmiawom
`
`
`
`
`
`
`
`
`
`SmanSalaam:35:82A;Gala;8518"“oomioum£52
`
`
`
`
`
`
`
`a:a:gigOR2;Swim;omwimflms9:.52-92§.$m
`
`
`
`
`
`
`
`flan—awzofik
`
`ER...33:2E.23:3?:£3:3?:33:E<22;9::a?
`
`Emu:
`
`U>m¢
`
`3.5:
`
`
`
`on:E:33183on:353mmSR8253321328:£282-8“.”
`
`
`
`
`
`
`
`STE.Sale»:372333.22E5382-822:72;Sada.
`
`
`
`
`
`
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`
`93:0282139:192Saloon8T8».Sula23.?3:m3
`
`
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`
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`3.5308.1%:585%23-2.:o853.22132Ruinson:an.
`
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`amino.2??825.Siam0.:Ion.Etc:835Ea;
`
`2:3.33:3.9:33:Emu:33:39:33:
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`
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`3EEEn;man:
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`man—.5
`
`Hogan—EU
`
`395m
`
`
`
`5$33.....535Eu:3&5ESE”;m...2...:
`
`
`
`
`
`Salsa.Eunice“:anemia!8318:331%:E:83.$818882-3%
`
`
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`
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`
`nfllmfl
`
`Swiamm
`
`3%.arm
`
`93$?
`
`amigo?
`
`so:89
`
`03immm
`
`83on:
`
`awn_loam_cowlnnn
`39.82
`mnvmlavwm
`
`cm~i3_
`
`amine
`
`own:on”
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`w:
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0609
`
`0609
`
`
`

`

`3. 3 Forming Sheet
`
`593
`
`
`
`
`
`an[newa”?a?8,15:2:loamone.ascm::2:on?cana:-a:v2.
`
`
`
`8m[can81.?asSo33-22cum.3“cm:-82amnion.“Edlameweon.
`
`
`
`
`
`32.5.8:-82can.9mm831.23Salon:8.318%an?53321%:wa:
`
`
`
`
`
`
`
`
`
`
`
`
`
`272cmcmmlomommlomv$.5287%SW2:53:03m9.amalg—372387020mmInacomic?8._$3an8”Se-Emdam837%.
`
`
`
`3953::50%EEaw3To
`
`
`
`
`
`
`
`
`2h:23:3.3.33:BE::3:Ed:23:E::55
`
`
`
`En.mm<ma:”EQ:555:.
`
`
`
`Enamuofih305m329m
`
`
`
`a:was.iguana?3.35m.auiuaéarfi32.5
`
`
`
`
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0610
`
`0610
`
`
`

`

`594
`
`Producing Sheet and Film
`
`[Refs on p. 644]
`
`I
`
`Carmanl Taper
`
`1m C
`
`onstant Taper Screw
`
`Food
`
`Transllion
`
`Marianna
`
`
`
`MixinglMetering Screw
`
`
`Feed
`4-
`Transition
`l Metering
`
`i
`
`Transition
`
`Decompression
`
`Metering
`
`
`
`Two-Stage Vented or Gas Injection Screw
`
`Figure 3.7 Schematics of various screw configurations for single-screw extruders. Figure redrawn
`from [1 I] and used with permission of cepyright owner
`
`screens placed against several 50 mesh screens. The screen pack is then placed against
`a breaker plate. Screens can be plates with drilled holes, welded wire mesh. woven wire
`cloth or porous sintered metal. Filter screens are used throughout the sheet extrusion
`industry and are especially important when running large percentages of regrind.
`particularly if the polymer is an intrinsic gel former such as polyethylene terephthalate,
`polyarnide.
`low-density polyethylene, polypropylene and rigid polyvinyl chloride.
`Pigmented polymers can also cause substantial filtering problems, particularly in
`regrind. Pressure drop across the filter screen must be continually monitored to
`determine when the screen has clogged and needs to be replaced. Continuous screen
`changers are expensive but useful if the polymer is heavily contaminated.
`
`Flow Improvement Devices
`
`In recent years. there has been great progress in improved plastication and homoge-
`nization of the polymer melt, primarily through improved screw design and motor
`drive and thermal feedback controls. Some typical plasticating and mixing screw
`sections are shown in Fig. 8.8 [12]. Surging, the bane of quality sheet production. has
`been greatly reduced. Gear pumps and static mixers are used to further improve melt
`quality prior to the die. Figure 8.9 is a schematic of an extruder having these
`features. Static mixers are dissipative devices that
`improve laminar mixing by
`separating the melt stream into many layers.
`reorienting the layers and then
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0611
`
`0611
`
`

`

`8.3 Forming Sheet
`
`595
`
`
`
` ‘\‘\“\‘\I\‘\“\‘
`
`
`
` “WWW
`
`Double-Wav Screw
`
`NE.»
`
`
`
`UC or Maddock Mixing Screw Tip
`
` m P
`
`arallel Interrupted Flight Screw
`
`Figure 8.3 Schematics of various mixing sections for msingle-screw extrudcrs. Figure redrawn from [12] and
`
`used with permission of copyright owner
`
`Fling Barrier Screw
`
`Screw
`
`Gear Pump
`Static Mixer
`Barrel
`
`
`
`
`
`WW-‘Vl. .....
`“51'
`
`\ I--...It-..\X\m\\‘-.\‘)! 29.5:254:. r. rd :2
`
`
`
`W
`
`Die
`
`Extruder
`
`Figure 8.9 Schematic of extruderfstatic mixen‘melt pumpp’die configuration
`
`recombining the layers in a different order. There are more than 30 types of static
`mixers [13]. The mixing section of a Kenics mixer is shown in Fig. 8.10 [14].
`Improved homogenization or mixing efiiciency must be weighed against increased
`shear history and pressure loss through these devices. Today, static'mixers are used
`when the screw design is not optimum For the polymer, when the melt pumping zone
`on the screw is too short or when the overall extruder L/D is too short. The relative
`effectiveness of many of these devices is reviewed elsewhere [15-18].
`Gear pumps or melt pumps are characterized as “closely intermeshing counter-
`rotating twin screw extruder(s)" [19]. Details are shown in Fig. 8.11 [20]. One gear is
`driven. It drives the other. The polymer melt is engaged by the gear teeth and forced
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:367)(cid:349)(cid:272)(cid:286)(cid:374)(cid:400)(cid:286)(cid:282)(cid:3)(cid:410)(cid:381)(cid:3)(cid:393)(cid:437)(cid:396)(cid:272)(cid:346)(cid:258)(cid:400)(cid:286)(cid:396)(cid:3)(cid:381)(cid:374)(cid:367)(cid:455)(cid:856)
`No unauthorized disclosure or reproduction; licensed to purchaser only.
`
`0612
`
`0612
`
`

`

`596
`
`Producing Sheet and Film
`
`[Refs on p. 644]
`
`
`
`Figure 8.10 Kenics static mixer element configuration. Redrawn from [l4] and used with permission
`of copyright owner
`
`
`
`Figure B. [1 Two views of gear or melt pump showing intermeshing gear rotation relative to flow
`direction [20]
`
`against the pump wall. The remeshing of the gear teeth forces the polymer from the
`pump. Gear pumps were originally employed to counteract surging and secondary
`flow effects from screw flights. Today they are used primarily to boost melt pressure
`prior to the die. Owing to leakage between the gear teeth and pump wall and
`between the edge of the gears and the pump wall,
`the pumps are not positive
`displacement pumps. Although the typical volumetric efficiency is 90% or so, low
`viscosity melts and high pressure drops can reduce efficiencies to 50% or less [20].
`Gear pumps are high shear devices. As a result.
`it
`is not unusual
`to see melt
`temperature increases of 10°C or more as the polymer passes through the gear pump.
`These pumps are not
`recommended for
`thermally sensitive polymers such as
`polyethylene terephthalate and rigid polyvinyl chloride.
`
`Pressure and Temperature in an Extruder
`
`The stated purpose of an extruder is to plasticate or melt the polymer and to deliver
`the conditioned. homogeneous polymer melt at a constant flow rate. The majority of
`
`(cid:926)(cid:3)(cid:1005)(cid:1013)(cid:1013)(cid:1010)(cid:3)(cid:18)(cid:258)(cid:396)(cid:367)(cid:3)(cid:44)(cid:258)(cid:374)(cid:400)(cid:286)(cid:396)(cid:3)(cid:115)(cid:286)(cid:396)(cid:367)(cid:258)(cid:336)(cid:856)(cid:3)(cid:4)(cid:367)(cid:367)(cid:3)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:400)(cid:3)(cid:396)(cid:286)(cid:400)(cid:286)(cid:396)(cid:448)(cid:286)(cid:282)(cid:856)(cid:3)
`© 1996 Carl Hanser Verlag. All rights reserved.
`(cid:69)(cid:381)(cid:3)(cid:437)(cid:374)(cid:258)(cid:437)(cid:410)(cid:346)(cid:381)(cid:396)(cid:349)(cid:460)(cid:286)(cid:282)(cid:3)(cid:282)(cid:349)(cid:400)(cid:272)(cid:367)(cid:381)(cid:400)(cid:437)(cid:396)(cid:286)(cid:3)(cid:381)(cid:396)(cid:3)(cid:396)(cid:286)(cid:393)(cid:396)(cid:381)(cid:282)(cid:437)(cid:272)(cid:410)(cid:349)(cid:381)(cid:374)(cid:854)(cid:3)(cid:36