SPE Polyolefins Conference 2005 Low Density and Linear Low Density Polyethylene Presentation Presented by J. Bayley NOVA Chemicals Corporation Note: The content of this presentation is intended for basic learning, the content may not describe or encompass all aspects of materials and processes
Overview of Presentation Topics • Feed Feedst stoc ock k for for the the Manu Manufa fact ctur uree of of Pol Polye yeth thyl ylen enee • Polyethylene Ba Basics Unit nit 1 - LDPE LDPE
Uni Unit 2 - LL LLD DPE
• Manufacturing Pr Processes
• Molecular Information
• Properties
• Comonomer Information
• Applications
• Properties
• Future for LDPE
• Catalyst vs Properties • Manufacturing Pr Processes • Applications • Future of LLDPE
Natural Gas to Ethane to Ethylene….
Ethane Supply System Gas Field
Gas Plant
Pipeline
Reprocessing Plant
Ethane
Residue Natural Gas
Petrochemical Industry
Energy Markets
Natural Gas Components Pipeline System
Export
Post Gas Plant
Post Straddle Plant
C1
Methane
90 – 100%
> 98%
C2
Ethane
3 – 10%
< 2%
C3
Propane
C4
Butane
< 1%
0
C5+
Pentane plus
H20
Water
0
H2S
Sulphur
0
CO2
Carbon dioxide
2%
< 2%
Gas Plan Plantt - Sep Separa arate te Comp Compon onen ents ts Methane / Ethane / Carbon Dioxide
Ethane / Propane
Water
Ethane
Methane Butane Pentanes
B u t a n e / P e n t a n e s
N i t r o g e n / P r o p a n e / B u t a n e
Propane Pentanes
Water
Carbon Dioxide
Natural Gas Pipeline
Nitrogen Liquids Pipeline
Natural Gas Field Contains many components in varying proportions
Reinjected underground
Pipeline Straddle Plant Extraction and Fractionation
r e z i n a h t e m e D
r e z i n a p o r p e D
r e z i n a h t e e D
r e z i n a t u b e D
Methane r o t a r d y h e D
s a G l a r u t a N
r e d n a p x e o b r u T
Ethane & C02 Propane Butane
Pentane Plus
W a t e r
Natural Gas to Fuel Markets
Ethylene Manufacturing from Ethane H H
H
C C H
H
Ethane (C2 H6) •
C C
H
H
H
800° C then fractionate -160° C
H
H2
Co-products
H
Ethylene (C2 H4) hydrogen
In simp simple le term termss Eth Ethan anee is is con conve vert rted ed into into Ethy Ethyle lene ne (the (therm rmal al decomposition) at high temperature in a steam steam furnace or cracker • Refrig Refrigera eratio tion n is is used used to separa separate te the variou variouss comp compone onents nts,, co-p co-prod roduct ucts, s, etc. • The The furn furnac acee and and auxi auxili liar ary y comp compon onen ents ts are are des desig igne ned d to eff effic icie ient ntly ly produce as much Ethylene as possible and as few co-products as possible • Co-P Co-Pro rodu duct ctss such such as as Hydr Hydrog ogen en,, CO2 CO2 etc. etc. can can be be sold sold for for oth other er use usess
Brief History of Polyethylene • PE synthe synthesis sis discov discovere ered d acci acciden dental tally ly in 1932 1932 by Imper Imperial ial Chemi Chemical cal Company (ICI) Scientists • Firs Firstt High High Pres Pressu sure re LDPE LDPE plan plantt buil builtt in 1939 1939 • In 1953, 1953, large large advanc advanceme ement ntss were were made made by Scient Scientist ist Carl Carl Zieg Ziegler ler,, inventor of a new catalyst system. system. A scientist scientist named named Giulio Giulio Natta also shares credit for this catalyst development • Known Known today today as the the Zieg Ziegler ler-Na -Natta tta Cataly Catalyst st (Z/N) (Z/N),, this this cataly catalyst st facilitated polymer synthesis at lower temperatures and pressures High Density Polyethylene (HDPE) materials were introduced soon after • In the the late late 1970’s 1970’s LLDPE LLDPE materi materials als were were intr introdu oduced ced to the market market • Signi Signific ficant ant Cataly Catalyst st advanc advances es since since that that time time wit with h the the advent advent of single-site catalysts
Polyethylene is ... • A pol polym ymer er of ETHY ETHYLE LENE NE or a cop copol olym ymer er of ethy ethyle lene ne and a comonomer • ETH ETHYLEN LENE - a gas gas compo ompossed of of two two carb carbon onss and and four four hydrogen molecules. Formula: C2H4 The monomer unit for polyethylene forms the backbone of the compound: H2C=CH2
Some Basic Definitions • Monomer - A chemica chemicall compoun compound d that that can undergo undergo polymerization. polymerization. The basic basic building block of a polymer
• Comonomer - One of the constitue constituents nts of a copolyme copolymer r • Copolymer - A produc productt of of copol copolyme ymeriza rization tion • Copolymerization - Polymerization Polymerization of two different monomers
• Homopolymer - Manufactured with no comonomer, with ethylene only
Practical Illustration of Polyethylene Designations LDPE (0.917 to 0.935 g/cc)
HDPE (0.955 to 0.970 g/cc)
LLDPE (0.905 to 0.955 g/cc)
Polyethylene Designations Polyethylene Polyethylene is classified by density ranges, as defined by ASTM: • LDPE
Type I
0.910 - 0.925 g/cc
• MDPE
Type II
0.926 - 0.940 g/cc
• HDPE
Type III 0.941 - 0.960 g/cc (Copolym (Copolymer) er)
• HDPE
Type IV >0.961 g/cc (Homopolymer)
Unit 1 PE Introduction and LDPE Overview
LDPE • Mole Molecu cula larr Str Struc uctu ture re LDPE LDPE - Long Long Chai Chain n Bra Branc nchi hing ng (LCB (LCB)) results in unique polymer properties
LDPE Manufacturing Processes Two main LDPE manufacturing processes in use: •
High Pressure Tubular Reactors
•
High Pressure Autoclave Reactors
LDPE Tubular Reactors (Simplified) • A tub tubul ular ar LDPE LDPE Reac Reacto torr is is a lon long g hea heatt exc excha hang nger er • Free Free Radi Radical cal polym polymeri erizat zation ion uses uses Pero Peroxid xidee init initiat iators ors or Oxyg Oxygen en to promote polymerization reactions • Ethy Ethyle lene ne is circ circul ulat ated ed thro throug ugh h a com compres presso sorr - the the mai main n pressurization of the feed stream is accomplished by a hyper compressor • Initi Initiato ators rs are intro introduc duced ed at vari variou ouss poin points ts along along the the leng length th of the the tube - Zone tempera temperature turess are accurately accurately controlle controlled d • No backm backmixi ixing ng takes takes plac placee in in the the tubul tubular ar system system,, resid residenc encee tim timee is is limited/short • The exoth exotherm ermic ic heat heat of of react reactio ion n is is rem remove oved d via via wate waterr jack jackets ets on the outside walls of the tube • Upon Upon exi exiti ting ng the the rea react ctor or the the mat mater eria iall pass passes es thr throu ough gh med mediu ium m pressure and low pressure separators (separates Ethylene from PE), PE moves to the extruder
Resin Manufacturing High Pressure Tubular PREHEATER
Primary Compressor
Secondary Compressor
Initiator Telogen
TUBULAR REACTOR Coolers
RAW PRODUCT SILO
Wax Drum HOPPER
To Disposal
To Finishing
Gear Pump and Pelletizer
Knockout Pots
S E P A R A T O R
LDPE Autoclave Reactors (Simplified) • Free Free radi radical cal type type of polym polymeri erizat zatio ion n uses uses Pero Peroxi xide de init initiat iators ors typica typicall lly y • Syst System em util utiliz izes es a stir stirre red d cyli cylind ndri rica call ves vesse sell • Ethyle Ethylene ne feed feed gas gas and Peroxi Peroxide de are intro introduc duced ed to to a compre compresso ssorr and and then then pumped with Peroxide initiator into the stirred autoclave vessel • Propr Propriet ietary ary desig designs ns baff baffle le or or part partiti ition on the reacto reactorr into into discre discreet et zon zones es enabling control of molecular species and amount of LCB of polymer in these zones • Back Backmi mixi xing ng does does take take plac placee in in the the auto autocl clav avee sys syste tem m • Walls Walls of the the autoc autoclav lavee unit unit are thick thick to accom accommo modat datee hig high h pres pressur suree Heat of reaction is removed by the introduction introduction of fresh feed • Upon Upon exit exiting ing the the react reactor or the the mate materi rial al pass passes es thro through ugh mediu medium m pres pressur suree and low pressure separators (separates Ethylene from LDPE polymer) • Poly Polyme merr ente enters rs the the pel pelle leti tiza zati tion on pro proce cess ss to to be pel pelle leti tize zed d
Resin Manufacturing High Pressure Autoclave VA Monomer
Telogen
Primary Compressor
Secondary Compressor
REACTOR
Voluntary Purge
MA Monomer
Initiator
SEPARATOR
Methane to Flare RAW PRODUCT SILO
To Finishing
Hourly Hold-Up Hoppers
< C3
HOPPER D E M E T H A N I Z E R
C 2 S P L I T T E R
Gear Pump and Pelletizer Ethane to Flare
C2
D E P R O P A N I Z E R
Solvent/Monomer Removal
Comparison of High Pressure Autoclave and Tubular LDPE Manufacturing Processes Information
Autoclave
Tubular
Length
20 ft
Up to 1 mile
Internal Diameter
3 ft
1-3 inches ID
Rx Temperature Range (°F)
350-500
350-600
Pressure within Rx (PSI)
15000-30000
20000-50000
Initiator Types
Organic Peroxide
Organic Peroxide or Oxygen
Typical Polymer Conversion Ranges per pass
Approx. 22% (varies with product mix)
Approx. 35% (varies with product mix)
Back Mixing Capability
Yes
No
General Observation
More precise tailoring of MW, MWD and Long chain branching (LCB)
Less capable of molecular tailoring and less uniform long chain branching (LCB)
General Observation
Comb-like LCB structure
Root-like LCB structure
(Note: This table provides general information. Technology may exist that is not encompassed by or include in this table. The information is intended for basic learning purposes only.)
Properties of LDPE Materials
LDPE Materials
Softness
Softer and more pliable than other PE types
Permeability
Higher, due to long chain branching and lower % crystallinity
Clarity
Available in high clarity for film applications - Improves clarity of LLDPE when blended with LDPE in low amounts
Processing
Shear thins in extrusion - processes easily at lower amps and pressures relative to LLDPE or HDPE
Equipment Needs
Screw/Die designed for LDPE required if extruding 100% LDPE
Melt Strength
Much higher than LLDPE due to presence of long chain side branched molecules molecules - (Important for film blowing, foam etc.)
Other Pros
Less prone to melt fracture than LLDPE or HDPE
Suit Suitab abil ilit ity y as a Blen Blend d Re Resin sin
Goo Good, com commonl monly y use used, can can be detr detriiment mental al to phy physi sica call pro prope pert rtiiesesLDPE is generally blended to improve ease of extrusion, increase melt strength or improve clarity of the end product
Shrink Properties
Possesses desirable biaxial shrink properties for shrink film
Limitations
Absolute physical properties lowest in class - extensional limitations or drawdown limitations limitations exist - LLDPE and HDPE can be drawn much thinner in blown or cast film processes
LDPE Applications • LDPE LDPE is still till an imp import ortant ant PE PE ty type • The The uni uniqu quee att attri ribu bute tess of of LDPE LDPE due due to LCB LCB prov provid idee desirable properties for some specific product applications • LDPE LDPE is used used at 100% 100% in some some appl applic icat atio ions ns such such as conventional Shrink Film, Extrusion Coating, Wire and Cable Jacketing, LDPE Foam etc. • LDPE LDPE is is use used d as as a pro prope pert rty y mod modif ifie ierr in film film and and she sheet etin ing g applications and is often blended with LLDPE (to improve clarity, processability, processability, output rates, etc.)
2002 APC-LDPE Volume by End Use Process Process (based on Am ercian ercian Plastics Cou ncil 2002 Data) Blow Molding Sheet (greater than 12 1% mil) Injection Molding 1% 6% Other Extruded Extruded P roducts 9%
Extrusion Extrusion C oating 16%
Other (R esellers, esellers, Compounders) 23%
Film Film (less than than 12 m il) 44%
LDPE Common Applications • Film Applications - Garment Garment Films, Films, Indust Industrial rial Liner, Liner, Lamination films, Coextruded Food Packaging, Bakery Films, Film Blends (with LLDPE) for food packaging, Shrink Overwrap, Kitchen Cling Film, etc. • Extrusion Coating Applications - Paper Paper Board Board Coatin Coating, g, Package Coating, Coating of other substrates (Examples foil coating, drink box coating, etc.) • Injection Molding - Lids, Lids, Caps Caps and and Clos Closure uress • Other Examples - Wire and Cable Cable applicat applications ions,, PE Foam, Foam, Pipe and Conduit, Non-abrasive films, Blow Molded squeeze bottles, etc.
The Future of LDPE • Conv Conven enti tion onal al LDPE LDPE has has exi exist sted ed for for man many y yea years rs and and was was predicted to be replaced by LLDPE • LDPE LDPE fut futur uree cap capac acit ity y gro growt wth h is like likely ly to be be less less than than for for LLDPE, though demand continues to be strong for LDPE • LDPE LDPE is valu valued ed as perf perfor orma manc ncee mod modif ifie ierr for for extr extrus usio ion n processing or to obtain desired physical properties such as clarity • Manu Manufa fact ctur urer erss can can be expe expect cted ed to push push the the bou bound ndar arie iess of of their processes and exploit existing technology, but significant advances in resin morphology are not widely expected to occur in this class of materials
Unit 2
Introduction to LLDPE
LLDP LLDPE E - Gener General al Info Inform rmat atio ion n • Line Linear ar Low Low Den Densi sity ty Poly Polyet ethy hyle lene ne (LLD (LLDPE PE)) is made made by the the copolymerization of ethylene and a comonomer - (Example: (Example: Ethylene Ethylene and Octene Octene copolymer copolymerized ized - can be be describ described ed as an Ethylene-Octene Copolymer)
• LLDP LLDPE E is is com compo pose sed d of of lon long g lin linea earr mol molec ecul ules es,, the the main main polymer chain is composed of long strings of repeating Ethylene units - Short side side chains chains (from comonomer) link onto onto the main polymer chains • LLDP LLDPE E typ typic ical ally ly has has no no lon long g cha chain in bran branch chin ing g (LC (LCB) B) • LLDPE LLDPE materi materials als are typic typicall ally y copoly copolymer merss but terpol terpolym ymers ers and quatropolymers have also been made • LLDP LLDPE E typi typica call lly y has has a nar narro row w dis distr trib ibut utio ion n of of main main cha chain in molecule lengths (LDPE and HDPE tend to be broader)
LLDP LLDPE E - Mole Molecu cula larr Diag Diagra ram m • LLDP LLDPE E cons consis ists ts of lon long g lin linea earr mole molecu cule less wit with h sho short rt sid sidee chain branches (SCB) • SCB SCB len lengt gth h is is a func functi tion on of como comono nome merr typ typee emp emplo loye yed d
Polyethylene Comonomers Commonly Used • Butene - A four carbon long molecule Formula: C4H8 H2C=CH-CH2-CH3 • Hexene - A six ca carbon long mo molecule Formula: C6H12 H2C=CH-CH2-CH2-CH2-CH3 • Octene - An eight carbon long molecule Formula: C8H16 H2C=CH-CH2-CH2-CH2-CH2-CH2-CH3
Como Comono nome merr Type Type - Prod Produc uctt Prope Propert rtie iess • • • •
•
Shor Shortt side side chai chain n bran branch chin ing g type type infl influe uenc nces es pro produ duct ct toug toughn hnes esss (Example: Butene, Hexene, Octene) Shor Shortt side side cha chain ins, s, lik likee thos thosee made made wit with h bute butene ne com comon onom omer er are are les lesss effective at disrupting chain folding Long Longer er sid sidee chai chains ns,, like like tho those se for forme med d with with hex hexen enee and and octe octene ne are are longer and result in superior physical properties Z/N cataly catalysts sts tend tend to to have have more more diff difficu iculty lty than than sing single le-si -site te catal catalyst ystss in in placing comonomer on the longer chain (higher molecular weight) portion of the polymer thus more comonomer ends up on the shorter chains Como Comono nome merr add addit itio ion n lev level elss are are used used to cont contro roll res resin in dens densit ity y (Example: Increased Increased comomomer comomomer content content increases increases short short chain branch branch conten contentt - (Example: and results in reduced resin density)
Effect of Comonomer Type on Physical Properties M e l t I n de x De nsity Com onom e r Type Da rt Im pa ct (gra m s/ mi l) Low Fricti on P uncture (J/m m) El me ndorf Te a r Stre ngth MD (gra m s/m il El me ndorf Te a r Stre ngth TD (gra m s/m il Te nsil e Stre ngth MD (psi ) Te nsil e Stre ngth TD (psi)
1.0 0. 919 bute ne
1.0 0.918 he x e ne
1.0 0.920 octe ne
100 34 100 300 4800 3700
200 50 300 650 5300 4500
335 56 400 710 6800 6400
Properties of LLDPE Materials
LLDPE Materials
Softness
Softer relative to HDPE but not as soft and pliable as LDPE
Permeability
Higher % crystallinity relative to LDPE-Barrier Properties dependant on part thickness and resin density to a large degree
Clarity
Clarity not as good as for LDPE in most most cases- LDPE can be blended to improve clarity
Processing
Stiff in shear during extrusion- Narrow molecular weight distribution, distribution, processes at higher amps and head pressures relative to LDPE
Equipment Needs
Screw/Die designed for LLDPE required if extruding-Extruders, Screws, Dies and Air Rings need to be designed for LLDPE
Melt Strength
Much lower than LDPE due to NO long chain side branched molecules, only short chain branching generally
Suitability as a Blend Resin
Can be blended blended into LDPE where desired- Eg: Can be blended into shrink film to modify shrinkage properties
Shrink Properties
Long linear molecules tend to orient highly in the machine directionshrinkage as a result is more imbalanced relative to LDPE
Strengths of LLDPE
High physical properties possible depending on comonomer used, catalyst used and molecular architecture- Very good elongational elongational ability, can be drawn down thinner as a film than LDPE, higher strength than LDPE permits downgaging
Limitations of LLDPE
Prone to surface melt fracture in blown film and sheet extrusion-Process Conditions and Process aid additives are used to off-set this problem
Catalyst Information • Metal Metal based based catal catalys ysts ts facili facilita tate te the reacti reactions ons requir required ed to polymerize and convert Ethylene to PE • Z/N Z/N cat catal alys ystt is in com commo mon n use use toda today y thou though gh mod modif ific icat atio ions ns and improvements have been made • Next Next gene generat ration ion cataly catalysts sts known known as single single-si -site te cataly catalysts sts and Metallocene catalysts also exist and are used in the production of mLLDPE, sLLDPE and HDPE *Note: Metallocene catalysts fall into the single-site catalyst family
Catalyst Influence on LLDPE Properties • A conv conven enti tion onal al Z/N Z/N cat catal alys ystt has has a vari variet ety y of act activ ivee reac reacti tion on sites producing varied polymer molecules • The result result is a hete heterog rogen eneou eouss dist distrib ributi ution on of molec molecule uless havi having: ng: – broader broader distribut distribution ion of molecula molecularr weigh weightt (mole (molecula cular r lengths) – varied varied como comonom nomer er incorp incorpora oratio tion n levels levels acro across ss the the molecular weight distribution (MWD)
Catalyst Influence on LLDPE Properties • New New adva advanc nced ed Z/N Z/N cat catal alys ysts ts imp impro rove ve com comon onom omer er pla place ceme ment nt comonomer is more uniformly distributed, less bias for the low molecular weight (MW) range • Impr Improv oved ed com comon onom omer er pla place ceme ment nt res resul ults ts in in impr improv oved ed phy physi sica call properties • MWD MWD of of LLD LLDPE PE is ofte often n nar narro row w to to max maxim imiz izee fin finis ishe hed d physical properties • Narr Narrow owin ing g the the MWD MWD can can make make the the pol polym ymer er cha chall llen engi ging ng to to process (less shear thinning) therefore MWD is an important consideration in resin design
Properties for Products Manufactured using Advanced Ziegler-Natta Catalyst Dart Impact *
Hexene Gas Phase Z/N
Hexene Gas Octene Octene Phase Solution Z/N Solution Advanced Z/N Advanced Z/N
*These are are typical values values – advances advances in technology technology have significa significant nt improvements improvements to product product properties. properties.
Properties for Products Manufactured using Advanced Ziegler-Natta Catalyst MD Elmendorf Tear Stength *
Hexene Gas Phase Z/N
Hexene Gas Octene Octene Phase Solution Z/N Solution Advanced Z/N Advanced Z/N
*These are typical typical values values – advances advances in technology technology have significan significantt improvements improvements to product product properties. properties.
Properties for Products Manufactured using Advanced Ziegler-Natta Catalyst Melt Index Density Comonomer T ype Process Catalyst T ype Dart Impact (grams/mil) Elmendorf T ear Strength MD (grams/mil) Elmendorf T ear Strength T D (grams/mil) T ensile Strength MD (psi)
1.0 0.918 Hexene Gas Phase Z/N 200 300 650 5300
1.0 0.920 Octene Solution Z/N 335 400 710 6800
0.8 0.916 Super hexene Gas Phase Advanced Z/N 500 400 600 6100
0.6 0.916 Octene Solution Advanced Z/N 620 450 750 7400
Single-Site Catalyst (SSC) Information • Ever Every y cata cataly lyst st rea react ctio ion n site site is is the the same same,, thus thus the the mol molec ecul ules es produced are more uniform • Ever Every y pol polym ymer er mole molecu cule le cont contai ains ns the the sam samee amo amoun untt of of comonomer (can result in improved properties) • Redu Reduct ctio ion n in low low mol molec ecul ular ar weig weight ht poly polyme merr com compo pone nent nt historically resulted in extrusion challenges largely addressed now by resin design and extrusion equipment improvements improvements • Metal Metalloc locen enee cata catalys lysts ts are a subset subset of the broade broaderr sing singlele-sit sitee family • Sing Single le-s -sit itee cata cataly lyze zed d mate materi rial alss tend tend to to have have red reduc uced ed low low molecular weight grease levels
Molecular Weight Distribution by GPC Z/N versus SSC 1.6
SSC polymer MI=1.9 MI=1.9 PD=2.3 1.4
Z/N polymer MI=5.0 MI=5.0 PD=5.8 PD =5.8
1.2
. ) w m ( g o L d / W d
1
0.8
0.6
0.4
0.2
0 2
2. 5
3
3. 5
4
4. 5
Log(mw)
5
5. 5
6
6. 5
7
Physical and Optical Properties for Materials Made Using Single-Site Catalyst Comonome r Type Me lt Inde x (gra ms/10 minute s) De nsity Me lt Flow Ra tio (I21/I2)
Supplie r A octe ne 0.97 0.9171 22.3
Supplie r A octe ne 0.94 0.9172 27.5
Supplie r B he x e ne 1.14 0.9168 16
Supplie r C he x e ne 1.08 0.9193 16.2
Z/N octe ne 0.95 0.9203 27.2
Amps Volts Pre ssure (psi) Spe cific Pow e r (lbs/hr./a mp) Da rt Impa ct (gra ms) Frictionle ss Puncture (J/mm) Elme ndorf Te a r MD (gra ms) Elme ndorf Te a r TD (gra ms) Ha ze (%) 45 Gloss (%) He x a ne Ex tra cta ble s (%) Se a l Initia tion Te mpe ra ture (C)
34 156 2925 1.19 990 118 255 325 2 88 0.3 103
32 144 2640 1.26 1050 93 265 370 2 87 0.4 103
39 142 3070 1.04 1200 114 190 330 3 87 0.4 99
36.5 137 3120 1.09 920 91 235 320 7 57 0.5 103
31.1 143 2810 1.29 180 45 430 730 15 40 1.1 111
Resin Manufacturing Processes • LLDPE Processes: – Gas Phase – Solv Solven entt Base Based d / Solu Soluti tion on – Slurry Lo Loop • Most Most LLDP LLDPE E is is pro produ duce ced d in in sin singl glee rea react ctor or syst system ems, s, but but some processes used to manufacture LLDPE do use multiple reactors
Gas Phase Process (Simplified) • Feed Feed gas gases es suc such h as Eth Ethyl ylen ene, e, But Buten enee or Hex Hexen ene, e, Hyd Hydro roge gen n etc. etc. are are introduced to the fluidized bed in the base of the gas phase reactor • Cata Cataly lyst st is intr introd oduc uced ed to the the reac reacto tor r • The exoth exotherm ermic ic heat heat of of reac reactio tion n is is cont control rolled led by the the fres fresh h feed feed gas circulation • High High Rx throu through ghput put rates rates and low low con conver versio sion n rate ratess per per pass pass are are typically achieved - feed gases recycle through the reactor entering at the base and exiting at the top • Granu Granular lar PE produc productt is is prod produce uced d in in the the reacto reactorr and and inter intermi mitte ttent ntly ly discharged out of the reactor into a purge bin, hydrocarbons are removed, granular materials conveyed to pelletization followed by pellet conveying to finishing area
Example of Gas Phase Process (Simplified) Compressor
Comonomer Recovery Unit
Reactor
Cooling Water Exchanger
Catalyst Preparation
Product Discharge System
Ethylene
Product
Dryer
Butene Railcar
Flare
Degassing and Drying
Degassing and Drying
Nitrogen Hydrogen Isopentane Co-Catalyst
Hexene Railcar
Solution Polymerization Process (Simplified) • All All asp aspec ects ts of reac reacti tion on take take plac placee in in sol solut utio ion n • All raw ingre ingredi dient entss incl includi uding, ng, Ethyl Ethylene ene feed, feed, Hydrog Hydrogen, en, etc. etc. are are dissolved into a solvent resulting resulting in a solution solution composed composed of the raw ingredients required • Cata Cataly lyst st is intr introd oduc uced ed to the the rea react ctor or/s /s • Soluti Solution on is introd introduce uced d int into o one one or more more sti stirre rred d auto autocla clave ve reac reacto tors rs temperature, residence time and mixing are controlled • Polym Polymer er soluti solution on exits exits the the reac reacto tor/ r/s, s, solven solventt is is flas flashed hed off in a separator and returns to distillation distillation • Polym Polymer er passes passes throu through gh a low low pressu pressure re separa separato torr into into an extrud extruder er • A devo devolat latiza izatio tion n extu extuder der is used used in in som somee case casess to to remo remove ve resid residual ual hydrocarbons while stripping vessels (post-extrusion) may also be used in some processes to accomplish this task
Low Pressure Solution Process (Simplified) Recycle Stream Catalyst
Ethylene Hydrogen Comonomer
Catalyst
5
1
2 Vapors
4 Pelletized Product
1. Stirred Autoclave Reactors 2. Separator 3. Separator
4. Pelletizer 5. Compressor
3
Slurry Process Description (Simplified) • Descri Descripti ption on is simpli simplifie fied d but but based based on the Phill Phillips ips Slurry Slurry loop loop design that can produce LLDPE, MDPE, HDPE, mLLDPE • The reacto reactorr is a cir circul culati ation on loop, loop, water water jacket jacketed ed to remove remove heat heat • A hyd hydoc ocar arbo bon n carr carrie ierr cir circu cula late tess the the reac reacti tive ve ingr ingred edie ient ntss aro aroun und d the the loop reactor • The The reac reacti tion on of of Ethy Ethyle lene ne,, Como Comono nome mer, r, Hyd Hydro roge gen, n, etc. etc. resu result ltss in polymer particles forming, suspended on the carrier • Polym Polymer er settle settless out out and is remove removed d from from the the reac reacto torr into into a flas flash h vessel that separates granular polymer from residual hydrocarbon • Polym Polymer er granu granules les exit exit the the flash flash vessel vessel into into a pur purge ge vessel vessel where where hydrocarbons are removed • Addit Additive ivess are are incorp incorpora orated ted,, gran granul ular ar mater material ial is extrud extruded ed and pelletized
Low Pressure Slurry Process (Simplified) Circulating Pump
Operating Conditions 200 - 250 o F 500 - 600 psi Ethylene Hydrogen Comonomer
LOOP REACTOR
Flash Tank
Catalyst
Vapors DRYER
Granular Polyethylene RECYCLE STREAM
2002 APC-LLDPE Volume by End Use Process (based on Amercian Plastics Council 2002 Data) Sheet (greater than 12 mil) Other Extruded Products 1% Pipe and Conduit 3% 1% Injection Molding 7% Film (less than 12 mil) 65%
All Other Uses 23%
LLDPE by Market in N.A. • 65% Film (12 mils or less) • 7% Injection Molding • The The rema remain inde derr is spre spread ad out out over over a var varie iety ty of pro produ duct ctio ion n processes such as: – Pipe an and Co Conduit – Sheeting – Blow Molding – Compounding
Source: APC Resin Statistics
Typical Applications • LLDPE – Grocery sa sacks – Garbage bags – Stre Strettch wrap rap fil film m – Agri Agricu cult ltur ural al fil film m and and tubi tubing ng – Milk po pouches – Wire Wire and and cab cable le coa coati ting ngss – Housewares – Larg Largee outd outdoo oorr toys toys – Chem Chemic ical al sto stora rage ge tan tanks ks – Landf andfiill cove covers rs
Future Development/Outlook • The The PE PE Indus Industry try is conti continuo nuous usly ly impr improvi oving ng produc productt performance by: – New New Cat Catal alys ystt deve develo lopm pmen ents ts – New react reactor or config configurat urations ions and manuf manufact acturin uring g process improvements – Tech Techno nolog logy y Lice Licens nsin ing g - exis existi ting ng tech techno nolog logie iess licensed to operate on new technology platforms => could result in novel Polyethylene materials
– Polyet Polyethyl hylene ene is evolvi evolving ng Stay Tuned!
References and Acknowledgements
• • • • • • • •
NOVA OVA Che Chemi mica cals ls Inte Intern rnaal Lite Litera ratture ure Kirk Kirk Othm Othmer er Ency Encycl clop oped edia ia of Chem Chemic ical al Tech Techno nolo logy gy American Plastics Council Chem Sy Systems (2003) Comm Commod odit ity y Ther Thermo mopl plas asti tics cs (JP (JP Arli Arlie) e) Judy Judy We Webb bb-B -Bar arre rett tt (NOV (NOVA A Chem Chemic ical als) s) Lan Ng Nguyen (N (NOVA Ch Chemicals) Chris Foy (NOVA Chemicals)
Questions?