Current Problems in Polymerization Reaction ... - ACS Publications

5 Current Problems in Polymerization Reaction Engineering W. HARMON R A Y

Downloaded by UNIV OF ARIZONA on December 2, 2012 | http://pubs.acs.org Publication Date: July 28, 1983 | doi: 10.1021/bk-1983-0226.ch005

University of Wisconsin, Department of Chemical Engineering, Madison, WI 53706

Polymerization reaction engineering is an important area in the process industry with many diverse and challenging design problems. In this survey, an introduction to some of the key design d i f f i c u l t i e s is followed by several specific examples i l l u s t r a t ing some of the intriguing and exotic phenomena arising routinely in polymerization reactors. A survey of the recent literature indicates a strong upsurge of interest in these problems.

C u r r e n t l y some 200 b i l l i o n l b s (~100 m i l l i o n m e t r i c tons) per year of s y n t h e t i c polymers a r e produced i n the world i n a wide v a r i e t y of p o l y m e r i z a t i o n r e a c t o r s . The world c a p a c i t y and expected r a t e of growth of the 10 l a r g e s t volume polymers i s shown i n Table I . The u l t i m a t e use of these products ranges from s y n t h e t i c c l o t h i n g t o l a t e x p a i n t s . The t o t a l world sales of the raw polymer i s now approaching $100 b i l l i o n / y e a r and the s a l e s of the f i n a l product a f t e r p r o c e s s i n g , molding, compounding, e t c . i s many times t h i s f i g u r e . Thus the f i e l d of p o l y m e r i z a t i o n r e a c t i o n engineering i s of s i g n i f i c a n t economic importance. Up u n t i l a decade or two ago, polymers were l a r g e l y s p e c i a l i t y m a t e r i a l s , manufactured i n batch r e a c t o r s from f a i t h f u l l y f o l l o w e d r e c i p e s scaled up from the chemists beaker. However, w i t h the growth of demand and increased p r i c e competition ( p a r t i c u l a r l y f o r h i g h volume commodity polymers), more e f f i c i e n t p o l y m e r i z a t i o n methods have been r e q u i r e d . Manufacturers of h i g h volume polymers are now moving t o fewer product l i n e s , more uniform product and the use of continuous r e a c t o r s . S i m i l a r l y , producers of r e l a t i v e l y low volume, h i g h q u a l i t y (and value) polymers are f i n d ing that t h e i r c o m p e t i t i v e edge comes from a deeper understanding of the r e l a t i o n s h i p between p o l y m e r i z a t i o n c o n d i t i o n s and product quality. Although t h i s change from t r a d i t i o n a l p o l y m e r i z a t i o n methods r e q u i r e s a much b e t t e r understanding of the p h y s i c a l and chemical 0097-6156/83/0226-0101$09.25/0 © 1983 American Chemical Society In Chemical Reaction Engineering—Plenary Lectures; Wei, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

102

C H E M I C A L REACTION ENGINEERING

Table I. World Capacity and Expected Growth of Largest Volume P l a s t i c s (1_) Rank

Capacity, millions


1980s 1981

Resin

Mid-1980s

of l b per yr.

1981

Change

1

2

P o l y e t h y l e n e , low-density

38,047

31,702

20.0%

2

1

Polyvinyl chloride

35,339

32,430

8.9

3

3

Polyethylene, high-density

22,895

18,071

26.7

4

5

Polypropylene

17,809

15,631

13.9

5

4

Polystyrene

17,626

16,491

6.9

6

10

P o l y e t h y l e n e , l i n e a r low-density

8,081

2,669

202.8

7

6

Acrylonitrile-butadiene-styrene

4,662

4,374

6.6

8

8

Isocyanates

4,270

3,634

17.4

9

7

Polyols*

4,255

4,246

0.2

10

9

Unsaturated

3,538

3,516

0.6

Other

5

TOTAL

a

polyesters

8,006

7,359

164,528

140,123

8.8 17.4%

a Used as i n d i c a t o r s f o r d e r i v a t i v e polyurethanes. b includes a c r y l i c s , amino r e s i n s , c e l l u l o s i c s , f l u o r o p o l y m e r s , p h e n o l i c s , p o l y a c e t a l s , p o l y c a r b o n a t e s , polyphenylene o x i d e , s t y r e n e - a c r y l o n i t r i l e .

phenomena i n the polymerizing medium, (and t h i s r e q u i r e s the s e r v i c e s of more w e l l - t r a i n e d p o l y m e r i z a t i o n r e a c t o r engineers), the economic b e n e f i t s from such improved engineering can be enormous. As only one example, new processes f o r l i n e a r lowdensity polyethylene (such as the continuous f l u i d i z e d bed process of Union Carbide (2_)) present a t t r a c t i v e a l t e r n a t i v e s to the t r a d i t i o n a l high pressure processes. These new processes can operate at 300-1000 p s i g rather than the t r a d i t i o n a l 30,000-50,000 p s i g and thus can reduce the plant c a p i t a l expenditure by 50% and energy consumption by 25%. This type of new low density p o l y ethylene process i s making s i g n i f i c a n t progress against the o l d e r , more w e l l e s t a b l i s h e d technology. Because polymerization r e a c t i o n engineering i s a r e l a t i v e l y new f i e l d , i t seems probable that many other t r a d i t i o n a l polymerization processes can be comparably improved through the a p p l i c a t i o n of polymerization r e a c t i o n engineering. In preparing t h i s review of p o l y m e r i z a t i o n r e a c t i o n engineering the author i s f o r t u n a t e that there have been so many books and survey a r t i c l e s to appear i n the l i t e r a t u r e r e c e n t l y ( c f . Table II). These, taken together, provide good d e t a i l e d coverage of the e s s e n t i a l s of the f i e l d ; t h e r e f o r e , extensive delegation of d e t a i l w i l l be made to these surveys. Foremost

In Chemical Reaction Engineering—Plenary Lectures; Wei, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

5.

RAY

103

Polymerization Reaction Engineering

Table I I . Some Recent Books and Survey A r t i c l e s on Polymerization Reaction Engineering


Author(s)

T o

P

Reference

i c

Keane (1972) Ray (1972) K e i i (1972) A l b r i g h t (1974) Min and Ray (1974) Gerrens (1976) Bouton and Chappelear (1976)

S i n g l e Phase P o l y m e r i z a t i o n Mathematical M o d e l l i n g Ziegler-Natta Polymerization Polymerization Processes (Monograph) Emulsion P o l y m e r i z a t i o n P o l y m e r i z a t i o n Reactions and Reactors Continuous Reactors (ed. volume)

Piirma

Emulsion P o l y m e r i z a t i o n

and Gardon

(1976) Ray and Laurence (1977) Poehlein and Dougherty (1977) Schildknecht and S k e i s t (1977) Henderson and Bouton (1979) Boor (1979) Gerrens (1980, 1981, 1982 ) Odian (1981) Ray (19 81) Bassett and Hamielec (1982) Piirma (1982) E l - A a s s e r and Vanderhoff (1982) Sebastian and Biesenberger

Quirk (1983)

(ed. volume)

3 4 5 6 7 8 9 10

P o l y m e r i z a t i o n Reaction Engineering Continuous Emulsion P o l y m e r i z a t i o n

11 12

P o l y m e r i z a t i o n Processes

13

P o l y m e r i z a t i o n Reactors

(ed. values) (ed. volume)

14

O l e f i n Polymerization P o l y m e r i z a t i o n Technology

15 16-18

Polymerization Kinetics P o l y m e r i z a t i o n Reactor Dynamics Emulsion P o l y m e r i z a t i o n (ed. volume)

19 20 21

Emulsion P o l y m e r i z a t i o n Emulsion P o l y m e r i z a t i o n

22 23

(ed. volume) (ed. volume)

P o l y m e r i z a t i o n Engineering

24

Ziegler-Natta Polymerization

25

(1983)

among these a r e the recent reviews of Gerrens beginning w i t h h i s outstanding plenary l e c t u r e of the 1976 ISCRE meeting ( 8 ) . This has been updated and expanded i n the recent chapter on polymerizat i o n technology (16) which has n e a r l y 500 r e f e r e n c e s . Just r e c e n t l y Gerrens has summarized t h i s review i n a superb d i s c u s s i o n of p o l y m e r i z a t i o n r e a c t o r s (17,18) . The novice j u s t beginning work i n t h i s area, as w e l l as the experienced p o l y m e r i z a t i o n r e a c t i o n engineer, w i l l both f i n d Gerrens surveys p r o f i t a b l e reading. In t h i s paper, we s h a l l f i r s t provide a broad brush p e r s p e c t i v e of the f i e l d and then focus on some i n t e r e s t i n g unsolved problems which a r e the subject of current research. 1

P o l y m e r i z a t i o n K i n e t i c s and Reactor

Design

Much has been w r i t t e n about p o l y m e r i z a t i o n k i n e t i c s and the e s s e n t i a l steps a r e shown i n Table I I I f o r the three p r i n c i p a l types of mechanisms ( f r e e r a d i c a l , i o n i c and c o o r d i n a t i o n , and


104


Table I I I .

Major Classes of Polymerization Reactions

Monomer Addition: A.

Free Radical — * • 2R

I

1 \

kd R

+ M

p

T î

initiation

1

i

1 Downloaded by UNIV OF ARIZONA on December 2, 2012 | http://pubs.acs.org Publication Date: July 28, 1983 | doi: 10.1021/bk-1983-0226.ch005

P

+ M

n

P

7~+ +1 *P P

+A —• Ρ

n

k

P

P^g^tion

n

n

+

χ

+M

f ^ M ^t^*»*

chain transfer

n

+ M^ disproportionate )

R

P

m ^

Vtermination k tc

— " M_.

combination

(sometimes chain branching reactions also occur) Ionic (anionic, cationic, coordination) I

+

M

Ρ

initiation

ι P

n

+ M

P

îÇ* n+l

propagation

(sometimes chain transfer or termination mechanisms also occur) H.

Polymer Coupling (polycondensation, crosslinkLng) P

n

+

m 1Ç n4m

P

P

propagation

condensation p o l y m e r i z a t i o n ) . However, there i s not comprehensive understanding of the k i n e t i c s . o f even these simple polymerizations, p a r t i c u l a r l y w i t h heterogeneous systems. The reader should cons u l t the surveys of Table I I f o r a d i s c u s s i o n of the remaining i n t e r e s t i n g problems i n k i n e t i c s . As important as k i n e t i c mechanism are the phase changes that occur i n p o l y m e r i z a t i o n . Only a small f r a c t i o n of polymerizat i o n s are c a r r i e d out only i n one phase; thus thermodynamics, heat and mass t r a n s f e r , and the k i n e t i c s of the phase change i t s e l f a l l play a r o l e i n determining the p r o p e r t i e s of the product polymer. Table IV i n d i c a t e s the p r i n c i p a l types of k i n e t i c mechanisms and r e a c t i o n media which a r i s e i n polymerizat i o n r e a c t o r s . Each of these c l a s s e s of systems has i t s own p e c u l i a r problems so that p o l y m e r i z a t i o n r e a c t o r design can o f t e n be much more c h a l l e n g i n g than the design of r e a c t o r s f o r short chain molecules. To i l l u s t r a t e some of the c h a l l e n g i n g problems of polymeriza-



medium

2.

Suspension

c. P r e c i p i t a t i o n ( b u l k and solution)

b.

Heterogeneous a. E m u l s i o n

1. H o m o g e n e o u s ( b u l k and s o l u t i o n )

Reaction

K I N E T I C MECHANISMS AND

radical

Vinyl (PVC)

polymers

V i n y l polymers ( S t y r e n e , PVC)

V i n y l polymers ( S t y r e n e , PVC)

V i n y l polymers (Styrene, LDPE)

Free

P o l y a m i d es (Nylon interfac i a l poly . )

Polyesters, Polyamides (PET, Nylon)

Polyethers (Ethylene ox i d e)

Polyacetals (formaldehyde) Vinyls (iso-butylene-buty1 rubber)

Condensation

mechanism

Polyolef ins with insoluble catalyst ( L i q u i d and gas p h a s e processes f o r HDPE, L L D P E , polypropylene)

Polyolefins with soluble catalyst (ethylenepropylene copolymers)

Coord i n a t i o n Catalysis

I N P O L Y M E R I Z A T I O N REACTORS

Ionic

Kinetic

REACTION MEDIA EMPLOYED

TABLE IV



106

CHEMICAL

REACTION

ENGINEERING

t i o n r e a c t o r design, l e t us l i s t some of the issues which must be faced: 1. K i n e t i c s and Phase Behavior - Table IV represents a s i m p l i f i e d p i c t u r e of the s i t u a t i o n ; however, some polymerizations go through s e v e r a l phase changes i n the course of the r e a c t i o n . For example, i n the bulk polymeri z a t i o n of PVC, the r e a c t i o n medium begins as a low v i s c o s i t y l i q u i d , progresses to a s l u r r y (the PVC polymer, which i s i n s o l u b l e i n the monomer, p r e c i p i t a t e s ) , becomes a paste as the monomer disappears and f i n i s h e s as a s o l i d powder. As might be expected, modelling the k i n e t i c s of the r e a c t i o n i n such a s i t u a t i o n i s not a simple exercise. 2. M a t e r i a l Mixing and Conveying - With such a v a r i e t y of morphologies, there can be serious n o n - i d e a l i t i e s i n micromixing and macromixing, p a r t i c u l a r l y at high conv e r s i o n s . Often a large amount of mechanical energy i s required f o r mixing and conveying. Sometimes, s t i c k i n g and f o u l i n g of the r e a c t o r surfaces by polymer i s a d i f f i c u l t design problem. 3. Heat Removal - Most polymerizations r e l e a s e l a r g e amounts of heat as monomer i s converted to polymer ( c f . Table V). In a d d i t i o n , the mechanical energy required f o r mixing may be converted to heat under h i g h l y viscous c o n d i t i o n s . Removal of t h i s heat i s o f t e n d i f f i c u l t f o r high conversion p o l y m e r i z a t i o n because of high v i s c o s i t y , heat t r a n s f e r surface f o u l i n g , and change of phase during r e a c t i o n . In many i n d u s t r i a l s i t u a t i o n s , d i s a s t r o u s r e a c t o r runaway i s an ever present p o t e n t i a l hazard because of these heat removal d i f f i c u l t i e s . This presents a great challenge to the process c o n t r o l engineer as w e l l as to the r e a c t o r designer. TABLE V HEATS OF POLYMERIZATION FOR SOME COMMON MONOMERS cal/mole at 25°C Ethylene Propylene Butadiene Styrene Vinyl chloride Vinylidene chloride V i n y l acetate Methyl a c r y l a t e Methyl methacrylate Acrylonitrile Formaldehyde

-21.2 -19.5 -17.6 -16.7 -22.9 -18.0 -21.2 -18.5 -13.2 -18.4 - 7.4



5. RAY


107

4. Q u a l i t y of Polymer Product - Product q u a l i t y i s a much more complex i s s u e i n p o l y m e r i z a t i o n than i n more conventional short chain r e a c t i o n s . Because the molecular a r c h i t e c t u r e of the polymer i s so s e n s i t i v e to r e a c t o r operating c o n d i t i o n s , upsets i n feed c o n d i t i o n s , mixing, r e a c t o r temperature, e t c . can a l t e r c r i t i c a l molecular p r o p e r t i e s such as molecular weight d i s t r i b u t i o n , polymer composition d i s t r i b u t i o n , chain sequence d i s t r i b u t i o n , degree of chain branching, and s t e r e o r e g u l a r i t y . I n a d d i t i o n , the morphological form of the polymer i s o f t e n a key q u a l i t y v a r i a b l e . For example, the p a r t i c l e s i z e d i s t r i b u t i o n i n emulsion, suspension, and p r e c i p i t a t i o n p o l y m e r i z a t i o n can be a c r u c i a l product s p e c i f i c a t i o n . One of the greatest d i f f i c u l t i e s i n a c h i e v i n g q u a l i t y c o n t r o l of the polymer product i s that the a c t u a l customer s p e c i f i c a t i o n s may be i n terms of non-molecular parameters such as t e n s i l e s t r e n g t h , crack r e s i s t a n c e , temperature s t a b i l i t y , c o l o r or c l a r i t y , a b s o r p t i o n c a p a c i t y f o r p l a s t i c i z e r , e t c . The q u a n t i t a t i v e r e l a t i o n s h i p between these product q u a l i t y parameters and r e a c t o r operating c o n d i t i o n s may be the l e a s t understood area of p o l y m e r i z a t i o n r e a c t i o n engineering. Table VI summarizes both types of q u a l i t y c o n t r o l measures. Because of the l a c k of o n - l i n e measurements f o r most of these product q u a l i t y v a r i a b l e s (molecular or otherwise), c o n t r o l of polymeri z a t i o n r e a c t o r s i s a s p e c i a l challenge.

In subsequent s e c t i o n s , examples w i l l be used t o i l l u s t r a t e some of the design c o n s i d e r a t i o n s l i s t e d here. Although a number of the surveys l i s t e d i n Table I I (e.g.; 6,11,13,16-18) provide a treatment of p o l y m e r i z a t i o n r e a c t o r s and processes i n i n d u s t r i a l use, Gerrens has provided an outstanding summary of t h i s i n f o r m a t i o n i n h i s recent survey (18). Table V I I , taken from Gerrens review provides an i n d i c a t i o n o f the v a r i e t y of r e a c t o r c o n f i g u r a t i o n s found i n i n d u s t r i a l p r a c t i c e . Because the s t a t e of the l i t e r a t u r e through 1980 i s so w e l l covered by the surveys l i s t e d i n Table I I , only very recent work on p o l y m e r i z a t i o n r e a c t i o n engineering w i l l be provided here as a supplement. This i s c a t e g o r i z e d by t o p i c i n Table V I I I . This l a r g e amount of l i t e r a t u r e (which i s not exhaustive) over the l a s t 18 months i s i n d i c a t i v e of the recent e x p l o s i o n of i n t e r e s t i n these problems. T



Table VI. Some Measures of Polymer Product Q u a l i t y END USE PROPERTIES Flow P r o p e r t i e s ( F i l m Blowing, Molding, e t c . ) Strength S t r e s s Crack Resistance


•Color, C l a r i t y

MOLECULAR ARCHITECTURE Average M o l e c u l a r Weight and Molecular Weight D i s t r i b u t i o n (or Melt Index, Viscosity, etc.)

MW

Polymer Composition and Composition Distribution nlOO

•Melting P o i n t •Corrosion Resistance •Abrasion

Resistance

Chain Sequence Distribution Degree of Chain Branching

• Density

-A-A-B-A-A-A-B-Ba.

Linear:

I II !! I

-c-c-c-c-c-c-

I IIII I

•Impact Resistance b.

•Temperature Stability

Branched :

-C-C-C-C-C-C-

•Swellability • P l a s t i c i z e r Uptake •Spray Drying Characteristics •Coating and Adhesion P r o p e r t i e s

Stereoregularity (Tacticity)

a.

Isotactic:

-C-C-C-C-C-C-C-

I

A b.

I

A

I

A

I

A

Syndiotactic: A

I

-c-c-c-c-c-

I A c.

I A Atactic: A

I

-c-c-c-c-c-c-c-

I

I

i

A

A

A

Average P a r t i c l e Size D i s t r i b u t i o n

A

Size

P a r t i a l P o r o s i t y and Surface Area



38

37

36

ho 39

Fluidized bed

^

Continuous stirred tank

(Double) Loop

35

Rotating ring disc

3k

g

CO

33

32

31

30

Stirred tank cascade

Table V I I .

Stirred tank + tower

29

28

Π)

Tower or tower cascade

27

26

25

Extruder

2k

23

Mixer + conveyor 22

21

Continuous tube 18

Continuous tube with distri- 9 buted bead w 19

2-Component mixer + mold 20

16

Batch stirred tank + autoclave with gate paddle nuscer 17

15

Batch stirred tank + filter press Ik

I I

1ΘΘ

I

j I I I I

125

158

188· &Qv^O

J

rj^^è

58 H Ά

è

1

-JÛ_

I I I j I I I I [ I I 1 I j ι » ι ι I I I I I j I I I I

25

50

75

108

125

150

RESIOENCE TIME ( M I N ) Figure U. A comparison o f the steady-state v i n y l acetate model and experimental data (1U7). T~ = 20 °C; T = 25 °C; = 0.50; I = O.OUlT m o l e / l i t . 0 - s t a b l e steady s t a t e ; and 0 - unstable transient. Q

f


5.

RAY


111

Monomer H2O


Emulsifier Initiator

Polymerizing Emulsion

Figure 5· A continuous reactor.

s t i r r e d tank emulstion p o l y m e r i z a t i o n



118

C H E M I C A L REACTION

ENGINEERING

(Μ) ς S t y r o i / g Latex

K)0

80

Π&0 40 20 % Conversion

0

Figure 6. M u l t i p l e steady s t a t e s i n the emulsion p o l y m e r i z a t i o n o f styrene i n a CSTR. (Reproduced w i t h permission from Ref. 253. Copyright 1971, V e r l a g Chemie, GMBH.)


5. RAY


119


100-1

0

1 0

2 0

3 0

Residence Time

4 0

5 0

6 0

(min)

Figure 7. Isothermal m u l t i p l i c i t y f o r the emulsion p o l y m e r i z a t i o n of methyl methacrylate i n a CSTR '(20h). [ s ] = [ i ]_ = 0.03 moles/L-water; o,x - experimental steady s t a t e s ; a n d * - t h e o r e t i c a l steady s t a t e s .


120

CHEMICAL

REACTION

ENGINEERING


i n d u s t r i a l p r a c t i c e ( c f . (20,253,254) f o r a d i s c u s s i o n of t h i s ) . Experimental r e s u l t s from our l a b o r a t o r y (201,202) shown i n Figure 8 provide only one example of t h i s troublesome problem. There i s great i n t e r e s t i n developing a q u a n t i t a t i v e understanding of the fundamental nature of these o s c i l l a t i o n s so that reactor design c r i t e r i a f o r a v o i d i n g them can be developed. Recent developments by Rawlings (255) would seem to provide a f i r s t step i n t h i s d i r e c t i o n . S o l i d - C a t a l y z e d O l e f i n P o l y m e r i z a t i o n . A t h i r d area where extremely c h a l l e n g i n g p o l y m e r i z a t i o n r e a c t i o n engineering problems a r i s e i s i n t r a n s i t i o n - m e t a l c a t a l y z e d polymerization of o l e f i n s such as ethylene, propylene and t h e i r copolymers. There i s great controversy at present over issues such as ( i ) which f a c t o r s c o n t r o l the molecular weight d i s t r i b u t i o n and t a c t i c i t y , ( i i ) what causes the d e c l i n e i n c a t a l y s t a c t i v i t y observed i n these r e a c t o r s , and ( i i i ) what p h y s i c a l phenomena are o c c u r r i n g i n the pores and on the c a t a l y s t s u r f a c e . Unambiguous measurements are few, so t h e o r i e s abound. For example, o l e f i n p o l y m e r i z a t i o n with a Z i e g l e r - N a t t a type c a t a l y s t y i e l d s narrow molecular weight d i s t r i b u t i o n s when the system i s homogeneous and very broad molecular weight d i s t r i b u t i o n s when the p o l y m e r i z a t i o n becomes heterogeneous. Has the nature of the c a t a l y s t changed so that some s i t e s are producing short chains while other s i t e s produce long chains? Or, has the increased heat and mass t r a n s f e r r e s i s t a n c e of the heterogeneous polymeriz a t i o n produced the great nonuniformity i n polymer chain length? To produce some answers to these and other questions requires a combination of mathematical modelling and d i a g n o s t i c experimentation. There i s some concensus that the p h y s i c a l p i c t u r e i n s i d e the growing polymer p a r t i c l e i s as f o l l o w s . For heterogeneous c a t a l y t i c systems polymerization occurs on the c a t a l y s t s u r f a c e producing polymer chains which f i l l the pores and grow out from the a c t i v e s u r f a c e . The c a t a l y s t p a r t i c l e f r a c t u r e s i n t o t i n y fragments as the pores are ruptured by growing polymer. Monomer, which must d i f f u s e to the c a t a l y s t surface to be c a t a l y t i c a l l y i n s e r t e d i n t o the polymer chain, sees an i n c r e a s i n g path f o r d i f f u s i o n as p o l y m e r i z a t i o n progresses and the c a t a l y s t fragments become more and more encapsulated by polymer. C l e a r l y t h i s i s a very complex p h y s i c a l s i t u a t i o n and simple models are not adequate to represent a l l the important phenomena. Therefore a number of r a t h e r complex models f o r the c a t a l y s t p a r t i c l e have been developed and t e s t e d computationally with r e a l i s t i c parameters f o r heat and mass t r a n s f e r as w e l l as k i n e t i c s . F i g u r e 9 i l l u s t r a t e s some of these models while Figure 10 (taken from (256)) shows the p r e d i c t e d propylene monomer c o n c e n t r a t i o n p r o f i l e to be expected i n a polypropylene polymer p a r t i c l e over a 4 hour period i n a s l u r r y batch r e a c t o r . Figure 11 i n d i c a t e s the corresponding molecular weight d i s t r i b u t i o n to be expected. As described i n d e t a i l elsewhere (121,122, 124,256,257), these extensive modelling s t u d i e s show that


5.

RAY


Continuous p o l y m e r i z a t i o n , Run 15, R e c i p e 8, Example o f o s c i l l a t o r y b e h a v i o r [ S ] - 0 . 0 2 mo l e s / l - w a t e [I] - 0.01 mo l e s / l - w a t < ΪΓ

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Current Problems in Polymerization Reaction ... - ACS Publications

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