Synthesis of Polylactic acid

ProductionDirect condensation of lactic acid – single step

Ring opening polymerization- Multi step process

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

Catalysts employed :

•Protonic acids•Metals•Metal Oxides•Metal halides•Organic salts of metals

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

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)

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

• 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)

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

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

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

Polymerization scheme of copolymers from L-lactic acid and D-lactic acid

Recent development of biodegradable sutures

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.

Biodegradable polymers approved for medical applications

PGA – Polyglycolic acid, PLA – Polylactic acid, PLGA – Copolymer of PLA & PGA

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.

Scheme 1 : Generalized flow sheet for the production of PLA from agricultural waste. 

Synthesis of Polylactic acid over

Solid acid catalyst

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

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

N2

Experimental set up for the synthesis of polylactic acid

Water removed through dean stark trap

Continuous purging of N2 gas

Dean stark trap

Infrared Spectral Analysis of PLA

-C=O

O

1759 1092

-C-O

CDCl3

13C NMR Analysis of PLA

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 )

3220C

Thermo Gravimetric Analysis of PLA

PLA prepared at 1500C

Differential Scanning Calorimetric Analysis of PLA

Tg = 560 C

Tm = 1300C

Thermo Gravimetric Analysis of PLA prepared at 1800C

4000C

PLA prepared at 1800C

Gel Permeation Chromatography Analysis

Wt Molecular weight - 42496

Polymerization of lactic acid by using various catalysts

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

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

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

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

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