synthesis of polylactic acid. production direct condensation of lactic acid – single step ring...
TRANSCRIPT
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Synthesis of Polylactic acid
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ProductionDirect condensation of lactic acid – single step
Ring opening polymerization- Multi step process
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Feasible process for the commercial production of PLA by Direct Condensation
Kinetic control over the reaction
Efficient removal of Water : Reletively high temperatures Reduced pressure Entraining agent such as various solvents
Suppresion of Depolymerization
Equilibrium between free acid , Water, and polyesters
Difficulty in removing the trace amount of water in the late stages of polymerization generally limit the ultimate molecular weight achievable by this approach
To overcome the above
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Catalysts employed :
•Protonic acids•Metals•Metal Oxides•Metal halides•Organic salts of metals
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General properties of Polylactic acid
[CH-C-O]n
O
CH3
Transperancy
Glass Transition temperature 50-600C
Melting Point 130-1800C
Crystallinity : 35-40 %
Tensile Strength : 4-6 Kg/mm2
Elongation : 3-4 %, brittle
Flexural Strength : 9~11 Kg/mm2
Impact Strength :~50 Kg-cm/cm2
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Production of Polylactic acid (PLA) polymer from corn sugar replaces petroleum feedstock.
PLA can replace PET, polyesters and polystyrene.
PLA is compostable.
PLA is carbon neutral – CO2 is recycled.
In the future, PLA will be made from ligno-cellulosic biomass.
Bio-Polymer Production (Cargill-Dow, USA)
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Background on P.L.A.
Used for 30 years in medicine:
• Encapsulation of vaccines
• Carrier for slow release medication - treatment of prostate cancer and infertility
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• A polymer made from cornstarch fermentation, declared a new generic fiber by the US FTC
• Competitive in price and performance with fossil fuel derived polymers: PE, PS, PP, polyester
• Can be engineered to be biodegradable
• Can be used in carpet tiles
• Cargill Dow's new facility in Blair, Nebraska, will use up to 40,000 bushels of corn each day and can produce more than 300 million pounds of PLA each year
Polylactic Acid (PLA)
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Cargill-Dow LLC Plant. Blair, Nebraska. November, 2001. Completed
The School of
PackagingRAA, © 2002Mechanical, Physical and Barrier
Properties of Poly(Lactic Acid)
August, 2001 August, 2001
September, 2001
September, 2001
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Main Producers
Producer 2000
Million lb/yr*
2001
Million lb/yr **
2002
Million lb/yr**
Cargill – Dow LLC 16 300 300
Mitsui Chemicals 1.3 1.3 1.3
Cost U$S / lb 1.5/2.0 1.0 0.5
* Chemical Week V162, 2000 & Plastics Week, Jan17, 2000
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Polylactic acid (PLA) for plastics production
Corn
Starch
Unrefined
Dextrose
Polymer Polymer ProductionProductionPLA
Lactide
Monomer Monomer ProductionProduction
Lactic AcidFermentatioFermentationn
Polymer GradesPolymer Grades
FiberFiber
Film Film
ThermoformingThermoforming
BottleBottle
WovenWoven
Non-wovenNon-woven
Etc.Etc.
PolymerPolymer ModificationModification
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Polymerization scheme of copolymers from L-lactic acid and D-lactic acid
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Recent development of biodegradable sutures
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Non-Solvent Process to Prepare PLANon-Solvent Process to Prepare PLA
Dextrose
Lactic
Acid
Fermentation
PrepolymerLactide
Formation
Dis
tilla
tio
nD
isti
llati
on
Meso
Lactide
Low D
Lactide
PolymerizationPLA
Polymer
Unconverted Polymer
Cargill Dow LLC Process. Gruber, et. al. 2000. Corn
Coordination / Insertion Propagation
By heating catalyst.
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Biodegradable polymers approved for medical applications
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PGA – Polyglycolic acid, PLA – Polylactic acid, PLGA – Copolymer of PLA & PGA
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Initial cost of PLA was too high that has limited its packaging applications to high value films, thermoformed containers, and coated papers .
PLA has a largest potential market because it is a compostable and biodegradable thermoplastic.
Derived from annually renewable agricultural resources .
New technologies for mass production of PLA promiseto lower its cost and widen its packaging applications,to include food packaging .
PLA can be fabricated on a variety of familiar processes .
There is a need to better understand its behavior and properties to be fully adapted in packaging applications.
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Scheme 1 : Generalized flow sheet for the production of PLA from agricultural waste.
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Synthesis of Polylactic acid over
Solid acid catalyst
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Experimental Section
Lactic acid (LA) is a 85% aqueous solution of the monomer
Catalyst Tungastophosphoric acid H3 [ P(W3O10) 4 ] x H2O (HPA) is heated at 1500C for 3 hours.
The following products were used without any further treatment
Chloroform-d1 with TMS (1%) (deuteration degree not less than 99.5%) from Merckfor NMR measurements.
Characterization of Polylactic acid :
IR, TGA, DSC 13C NMR and GPC
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10 gms of Lactic Acid 40 mg of HPAH3 [ P(W3O10) 4 ]
Stirred at 1500C for 3 hrsContinuous flow of N2
Precipitate
Viscous liqiud
Poured into 100ml of methanol
Filterd & Dried
PLA
Vessel with Dean Stark Trap
Schematic Representation
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N2
Experimental set up for the synthesis of polylactic acid
Water removed through dean stark trap
Continuous purging of N2 gas
Dean stark trap
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Infrared Spectral Analysis of PLA
-C=O
O
1759 1092
-C-O
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CDCl3
13C NMR Analysis of PLA
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13C NMR of PLA ( Solvent CDCl3)
δ 169.5 (
δ 69.0 ( O=C O C H-)
δ 16.6 (
13C NMR Analysis of PLA
C=O )
CDCl3
CH3 )
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3220C
Thermo Gravimetric Analysis of PLA
PLA prepared at 1500C
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Differential Scanning Calorimetric Analysis of PLA
Tg = 560 C
Tm = 1300C
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Thermo Gravimetric Analysis of PLA prepared at 1800C
4000C
PLA prepared at 1800C
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Gel Permeation Chromatography Analysis
Wt Molecular weight - 42496
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Polymerization of lactic acid by using various catalysts
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Catalyst Temperature
(0C)
Mw(g/mol)
GPC
H2SO4*
(Conventional)
HPW#
180
200
220
150
31000
30600
32600
42496
Comparison with conventional catalyst
* reaction duration -12 h # reaction duration -3 h
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Table 1 Summary of the catalysts used for polymerization of Lactic acid Condensation polymerization
S.NoCatalyst Weight % of
catalystsTemp K MW(g/mol)
123456
Tolune sulphonic acidSulphuric acidBoric acidPhosphoric acidNafion-HMethyl sulphonic acid
1,2.50.1to 1.5,2.510.1,2.52.02.5
373-423,403373,403358-393453,473,433403
145810000031000,650003800,6500400020000
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Ringopening polymerization
1234567891011121314151617181920212223242526272829303132
ZnCl2
Al(acac)Sn(II)octoateSb2O3
Ti(IV)butylateTi(IV)isopropylateDibutyltin dilaurate (DBTL)Stannous octoateTetraphenyltinStannous octoateMgAlZnSnTiO2
ZnOGeO2
ZrO2
SnOSnCl2
SnCl4
Mn(AcO)2
Fe2(LA)3
Co(AcO)2
Ni (AcO)2
Cu (AcO)2
Zn(LA)2
Y(OA)3
Al(iPrO)3
Ti (BuO)4
TiO(acac)2
(Bu)2SnO
0.10.10.10.10.10.10.10.05
0.010.50.50.50.50.830.620.720.680.570.801.101.571.701.501.512.751.862.923.793.552.741.05
353353353353353353353
451
433433433433433433433433433403403433433433433433433433433403403403
47003600800010800150009000670037000-7600014000-100,00014000-350,0002100540035000230000160020000130015002300002300002900019000270003200014000001900200002000015008000700013000
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Table .2. Typical applications of PLA
Processes End Products
Non woven fibres Personal hygiene, protective clothing, filtration
Oriented films Container labels, tape
Extrusion coatings Dinnerware, food packaging, mulch film
Flexible film Food wrap, trash bags, shrink wrap
Cast sheet Delivery trays
Injection moulding Rigid containers, Dairy containers
foam Clam shells, meat trays
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Developed process utilizes a noncorrosive, environmentally friendlySolid acid catalyst
The reaction temperature is decreased from 1800C to 1500C
The reaction duration is three hours – obtained required Molecular weight
The solid acid can be completely recovered and regenerated.
The physico-chemical properties of PLA can be widely tunned accordingto the requirements i.e by changing various solid acid strength
Salient features
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