6 Polymzn process (251050).pdf

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By Dr. Walaiporn Prissanaroon-Ouajai

411317 Polymer chemistry (2-2552)411317 by Dr. Walaiporn Prissanaroon-Ouajai (IC-KMUTNB)

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Polymerization Process Polymerization Process

Polymerization ReactionPolymerization Reaction

1. Chain-Growth Polymerization

2. Step-Growth Polymerization

( Methods or Techniques of Polymerization

411317 by Dr. Walaiporn Prissanaroon-Ouajai (IC-KMUTNB)

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1. Bulk Polymerization

2. Solution Polymerization

3. Suspension Polymerization

4. Emulsion Polymerization

Techniques of Polymerization Techniques of Polymerization


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1. Organic Substance1. Organic Substance* Toxicity

Acryonitrile

Styrene-Acryronitrile Copolymer (SAN)

Maximal Concentration : 20 ppm for 8 hr-Exposure

Design Criteria Design Criteria

CHCH22=CH=CHCNCN

Polyacryonitrile-CH2-CH-CN

n

-CH2-CH-CH2-CH-CN

n


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Design Criteria1. Organic Substance

Ziegler Catalyst (Complex of TiCl3-AlR3)

Acrylate Monomer Ester

* Flammability

* Odor

Ex. CH3

H2C=C

O=C-O-CH3

Methylmethacrylate (MMA)


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Monomer + Initiator + Solvent + Catalyst

PolymerizationPolymerization

Polymer + Starting Material DistillationDistillationExtractionExtractionCrystallizationCrystallization

2. Polymer Product2. Polymer Product* Purity



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Exothermic Reaction

3. Reaction3. Reaction* Heat of Polymerization


CH2=CHX -CH2-CHX-n

--∆∆HHpp


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-∆Hp of Various Polymers


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--∆∆HHpp

RepeatingUnit

Monomer

16.7 kcal/mol16.7 kcal/mol

-CH2-CH-

Styrene


CH3

-CH2-CH-

α-methyl styrene


CH3

-CH2-CH-CH3

Isobutylene

-CH2-CH-CH3

Propylene


High Pendent Group

SterricSterric ReplusionReplusion Difficult to occur Difficult to occur PolymerizationPolymerization

Lower -∆Hp


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Problems of Heat

--∆∆HHpp = 10 kcal/mol= 10 kcal/mol

ExampleExample

MonomerMonomer PolymerPolymer MW = 100MW = 100Specific Heat = 0.5 Specific Heat = 0.5 cal/cal/ooCC--gg

∆∆H = CH = Cpp∆∆T T

= 200 = 200 ooCC

∆∆T = T = ∆∆H = 10,000 cal/molH = 10,000 cal/molCCpp 0.5 0.5 cal/cal/ooCC--gg

∆∆T = 10,000 cal/molT = 10,000 cal/mol0.5 x 100 cal/0.5 x 100 cal/ooCC--molmol

MW decrease


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PolymerizationPolymerization

Increasing Viscosity

Design Criteria3. Reaction

* Viscosity

Auto-accelerationor Trommsdroff Effect


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Rpincrease

PropagationPropagation

kkpp constantconstant

A + A*

TerminationTermination A* + A*

kktt decreasedecrease

MW increase


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Types of Polymerization ProcessesTypes of Polymerization Processes


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Types of Polymerization ProcessesTypes of Polymerization Processes

Homogeneous reactions

Heterogeneous reactions


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1. Bulk Polymerization1. Bulk Polymerization(Mass or Block Polymerization)

MonomerMonomer ++ InitiatorInitiator

Polymer Unreacted MonomerUnreacted Initiator

++ ImpurityImpurity

CriteriaCriteria%% Initiator and Polymer must be able to dissolve Initiator and Polymer must be able to dissolve

in Monomer.in Monomer.


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AdvantageAdvantage Polymer with very high purity

DisadvantageDisadvantage High Conversion High Viscosity

\ Difficult to release heatHigh MWD

Hard to control reaction rate

Low MW

\ Auto-acceleration(from high viscosity)

High MW


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Applications

[ Chain-Growth Polymerization

[ Step-Growth Polymerization

Only Clear Products (PE/PS/PMMA/PC)

Most



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1.1 Quiescent Bulk Polymerization

Monomer CastingMonomer Casting Ex. Phenol-formaldehyde Polymer

PMMA Sheet

High MW Product Tough Polymer

Monomer + Initiator

Advantages

Shaped Product


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1.1 Quiescent Bulk Polymerization

Mold Mold filled with M or casting syrup

Mold sealed and clamped

Mold placed in oventime and temp. depend on sheet thickness, type of M

Sheets removed and cooled

Cast sheets annealed and preshrunk at > 145oC

Molds cooled and disassembled


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Major ProblemsMajor Problems

1. Heat Removal

2. Conversion

3. Shrinkage (~21%)

Solution

Add low MW polymer (Syrup)10-30%


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1. Bulk Polymerization1.2 Stirred Bulk Polymerization

PMMA & PS Continuous Stirred Tank Reactor(CSTR)

CSTRCSTR

Heat Removal

Melt Polymer

MoldingMonomer

Initiator

Polymer < 70% conversion


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1.2 Stirred Bulk Polymerization

Nylon 66

High MW Polymer

Die HeadDie Head : : SpinneretSpinneret


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2. Solution Polymerization2. Solution Polymerization

MonomerMonomer++ InitiatorInitiator++SolventSolvent

Q Release Heat of Reaction

Q Reduce Viscosity Avoid Autoacceleration Effect

Problems of SolventProblems of Solvent

ø Purity

ø Chain Transfer Reaction by Solvent


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4 Types of Solution Polymerization 4 Types of Solution Polymerization

ComponentsComponentsTypeType

11SolubleSoluble

SolubleSoluble

SolubleSoluble

22SolubleSoluble

InsolubleInsoluble

SolubleSoluble

33SolubleSoluble

InsolubleInsoluble

InsolubleInsoluble

44SolubleSoluble

SolubleSoluble

InsolubleInsoluble

Monomer andMonomer andsolventsolvent

InitiatorInitiator

PolymerPolymer


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2.2 Insoluble Initiator 2.2 Insoluble Initiator

Initiator = Solid

Ex. Cr-SiO2-AlO3 Catalyst

Isooctane (liq)Ethylene (g)

Catalyst bed

Separator

Polymer

Recycle


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2.3 Insoluble Initiator & Polymer 2.3 Insoluble Initiator & Polymer 2. Solution Polymerization

Heterogeneous Reaction

monomer + solvent initiator

solution

polymerization

polymercooling

suspension

separatorUnreactedmonomer

Isooctane

Ethylene

Polymer

T < 150 oC

Catalyst

liquidCooling coil

Unreacted ethylene(gas)

Separatorsuspension


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2.4 Insoluble Polymer 2.4 Insoluble Polymer 2. Solution Polymerization

Interfacial PolymerizationO O

Cl-C-(CH2)8-C-Cl

in CCl4

H2N-(CH2)6NH2

in H2O

+O O

-C-(CH2)8-C-HN-(CH2)6NH-

amide bond

insoluble polymer


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3. Suspension Polymerization3. Suspension Polymerization

MonomerMonomer ++ InitiatorInitiator ++ HH22OO

Suspension

+ Suspending Agent+ Suspending Agent

Medium for heat removal

Polymz in suspended beads

Stirred

Suspended beads of polymer O 0.01-0.5 cm

Ø Initiator must be soluble in Monomer

¤ Heterogeneous Polymerization

[ Ex. PVAL & Gelatin


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Mechanism : Bulk Polyzn

Rate : Faster than Bulk

O 0.01-0.5 cm

α Stirring Rate α Suspending Agent

Size of beads ordroplets of polymer


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Polymer Suspend in H2O

If Tg of Polymer > Troom

Temp

glassy state

rubb

ery s

tate

Tg

Solid

If Tg of Polymer < Troom Rubber

Glue

Dried Granules

Application

PSPMMAPAN

Clear solid (Amorphous)


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4. Emulsion Polymerization4. Emulsion Polymerization

MonomerMonomer ++InitiatorInitiator++ HH22OO

+ Emulsifier-Stabilize colloid system

-Form Micelle

¤ Heterogeneous Polymerization

Suspension

Micelle Polyzn in Micelle

Polymer in Latex form Direct ApplicationK Paint & coating agent


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Comparison btw Emulsion & Suspension Polyzs

Composition

Initiator

Product

Product size

Emulsion

M + I + H2O + EM

soluble in H2O

Latex

0.05-5 µm

Suspension

M + I + H2O + SA

soluble in M

Suspended droplets

0.01-0.5 cm


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Mechanism of Emulsion Polymerization

Emulsifier : Surfactant R-COO- Na+

-----R---COO-

Hydrophobicsegment

Hydrophilicsegment

CMC

in H2O

Micell~ 50-100 molecules

H2O

Polymerization

CMC = critical micell conc.surface tension

viscosity

[surfactant][CMC]


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Polymerization SystemPolymerization SystemMonomer droplet (non-polar)stabilized by surfactant (1-10 µm)

I soluble in H2O

surfactant

micelle after CMC (10-3-10-4 µm)

I and M diffuse into micelle

polyzn in micelleM droplet decrease in size

Swollen micelleboth polymer & unreacted monomer

Zero when 50-80% conversion

No monomer in micelle

Rp decreaseLatex

colloid of polymerin H2O

(0.05-5 µm)(monomer-polymer particle)411317 by Dr. Walaiporn Prissanaroon-Ouajai (IC-KMUTNB)

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Kinetic of Emulsion Polymerization

v polymerization in micelle

Rp = kp [M][M*]

unreacted monomer

propagating molecule

%conversion < 70%

[M] ~ constantH2O

M


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[M*] = conc. of propagating chain (with active species)

Rate of Initiator diffusion into micelle ~ 10 sec/radical

[M*] = Np

2No. of swollen micelle

in swollen micelle

swollen micellewith active radicalwith inactive radical

H2O

M


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Rp = kp [M] Np

2Emulsion polymerization

Degree of polymerization

DP = 2 γ = 2 Rp

Ri

const.Rp α Np α [EM]

Ri = 2fkd[I]

DP = kp [M] Np

2fkd [I] DP α Np

[I]

Kinetic of Emulsion Polyzn


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Comparison btw Emulsion & Bulk Polyzs

Kinetic of Emulsion Polyzn

Emulsion

Bulk

Rp α Np α [EM] DP α Np[I]

Rp α [M] [I]1/2 DP α [M][I]1/2

[I] increase

Emulsion

Rp & DPBulk

Rp const. & DP

If High MW is wanted ?411317 by Dr. Walaiporn Prissanaroon-Ouajai (IC-KMUTNB)

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Advantage of Emulsion polymerization

Obtain High Rp and High MW in the same time byincreasing [EM]

Seeded Polymerization

Complete Latex Dilute

I + M

High MW Latex


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Comparison of 4 types Polymerization Process

System

Mechanism

Temp Control

Product

Purity

MW

Bulk

M+I

difficult

Shaped product

Very High

High MWD

Solution

M+I+solt

easier

Any

High

Lower

Rp α [M] [I]1/2

DP α [M]/[I]1/2

suitable for step polyzn

Suspension

M+I+solt+SA

easy

granule

Lower

High

Emulsion

M+I+solt+EM

easy

colloid or Latex

Lower

High

suitable for chain polyzn

Rp α Np α [EM] DP α Np/[I]


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6 Polymzn process (251050).pdf