Polymerization Reactions and New Polymers

3

Novel Heat Resistant Plastics from Hydrogenation of Styrene Polymers

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J. F . P E N D L E T O N and D . F . H O E G Roy C. Ingersoll Research Center, Borg-Warner Corp., Des Plaines, Ill. 60018 E . P. G O L D B E R G Xerox Corp., Rochester Research Center, Webster, N.Y.

The

combination of polymer preparation by anionic tech-

niques and hydrogenation

technology

based

on soluble

transition metal catalysts has allowed the facile hydrogenation of polystyrene

and styrene-diene

block

copolymers.

Problems encountered in hydrogenation of polymers using conventional techniques have been avoided.

Polystyrene is

hydrogenated to poly(vinylcyclohexane) (PVCH) a heat distortion temperature 60°C PVCH, ing

however, has low impact strength.

styrene-diene

in the diene

hydrogenation

By hydrogenat-

block copolymers, materials with heat

and impact resistance resulted. polystyrene

which has

higher than polystyrene.

By varying the level of

block copolymers

products of

ranged from rubbery to rigid materials all

of which were clear, tough, and heat resistant.

/ ^ h e m i c a l m o d i f i c a t i o n of p o l y m e r s ( I ) , s u c h as h a l o g e n a t i o n , e p o x i d a t i o n , a n d c h l o r o s u l f o n a t i o n , has g i v e n the i n d u s t r y u s e f u l p r o d u c t s w h i c h i n most cases c o u l d n o t b e m a d e d i r e c t l y f r o m m o n o m e r merization.

poly

H y d r o g e n a t i o n , a m o r e esoteric f o r m of p o l y m e r m o d i f i c a

t i o n , w h i l e b e i n g as o l d as p o l y m e r c h e m i s t r y , has n o t g i v e n c o m m e r cially useful polymers until recently.

S t a u d i n g e r , i n t h e 1920's, u s e d

the h y d r o g e n a t i o n o f r u b b e r ( 2 ) a n d l o w m o l e c u l a r w e i g h t p o l y s t y r e n e (3)

t o p r o v e that t h e m a c r o m o l e c u l e s

were composed

of long chains

w i t h p r i m a r y v a l e n c e b o n d s as o p p o s e d t o the c u r r e n t theories a t t h a t t i m e w h i c h c o n s i d e r e d " p o l y m e r s " as association complexes o f l o w m o l e c u l a r w e i g h t species (4).

S i n c e that t i m e h y d r o g e n a t i o n s o f polystyrenes 27

Platzer; Polymerization Reactions and New Polymers Advances in Chemistry; American Chemical Society: Washington, DC, 1973.

28

POLYMERIZATION REACTIONS A N D N E W POLYMERS

a n d p o l y d i e n e s h a v e b e e n s t u d i e d i n the h o p e of o b t a i n i n g c o m m e r c i a l l y attractive p o l y m e r d e r i v a t i v e s (5, 6, 7, 8, 9 ) . b y M o b e r l y (10)

a n d W i c k l a t z (11)

T w o r e v i e w s i n this area

discuss the d e v e l o p m e n t of n e w

techniques b o t h i n synthesis a n d catalysis for the h y d r o g e n a t i o n of p o l y dienes a n d s t y r e n e - d i e n e c o p o l y m e r s .

W h i l e the b u l k of research d i s

cussed i n these r e v i e w s has b e e n i n v o l v e d w i t h p o l y d i e n e s , some i n t e r esting w o r k w i t h n o n - d i e n e p o l y m e r s s h o u l d be m e n t i o n e d . n i t r i l e has b e e n h y d r o g e n a t e d b y J . H . P a r k e r (12)

u s i n g a 15% n i c k e l catalyst i n the presence of a m m o n i a . (13)

Polyacrylo-

to the p o l y a l l y l a m i n e Gluesenkamp

r e p o r t e d the p a r t i a l h y d r o g e n a t i o n of p o l y ( v i n y l c h l o r i d e ) i n d i


m e t h y l a c e t a m i d e a g a i n w i t h a h i g h l e v e l of catalyst ( P d / C ) . hofer (14)

Stein-

a n d W a r n e r ( 1 5 ) , u s i n g h i g h concentrations of n i c k e l c a t a

lysts, h y d r o g e n a t e d p o l y s t y r e n e h o m o p o l y m e r to p o l y ( v i n y l c y c l o h e x a n e ) . A s o b s e r v e d i n a l l the references, the use of n o b l e m e t a l a n d t y p i c a l t r a n s i t i o n m e t a l h y d r o g e n a t i o n catalysts r e q u i r e d l o n g r e a c t i o n times, h i g h catalyst concentrations, a n d h i g h t e m p e r a t u r e .

T h i s was a c c o m

p a n i e d b y p r o b l e m s i n catalyst r e m o v a l a n d i n most cases some m o l e c u l a r b r e a k d o w n of the p o l y m e r d u r i n g h y d r o g e n a t i o n .

P r o b l e m s are

c o m p o u n d e d w h e n the p o l y m e r to be h y d r o g e n a t e d is c r o s s l i n k e d or not c o m p l e t e l y s o l u b l e i n the h y d r o g e n a t i o n solvent. so-called

soluble

alkylaluminums review,

t r a n s i t i o n m e t a l catalysts m a d e

T h e recent use of by

the r e a c t i o n

a n d t r a n s i t i o n m e t a l salts is d e s c r i b e d

a n d these

systems, at least i n p o l y d i e n e

of

in Moberly's

a n d styrene

diene

c o p o l y m e r s , a v o i d the p r o b l e m s e n c o u n t e r e d w i t h t y p i c a l heterogeneous catalysts.

W o r k i n o u r l a b o r a t o r y confirms that residence

times are

short, catalyst concentrations are l o w , a n d p r o d u c t w o r k u p is easy.

In

fact, the a c t i v i t y of s u c h systems is t r u l y c a t a l y t i c i n that as m u c h as 4 k g of a s t y r e n e - b u t a d i e n e c o p o l y m e r c a n be h y d r o g e n a t e d c o m p l e t e l y u s i n g a s o l u b l e catalyst c o n t a i n i n g o n l y 1 g r a m of cobalt. T h e i m p e t u s for this research was generated f r o m the e x t r a o r d i n a r y properties

established for h y d r o g e n a t e d

poly (vinylcyclohexane) I.

(PVCH).

amorphorus

polystyrene—i.e.,

T h e s e properties are s h o w n i n T a b l e

B y c o m p l e t e h y d r o g e n a t i o n of p o l y s t y r e n e , density is decreased

by

10%, hardness is s i g n i f i c a n t l y i m p r o v e d , c l a r i t y is m a i n t a i n e d , a n d w i t h this heat resistance is d r a m a t i c a l l y i m p r o v e d .

A n increase of 6 0 ° C i n

A S T M heat d i s t o r t i o n is d e m o n s t r a t e d ; this, of course, is reflected i n the h i g h tensile strengths at elevated temperatures s h o w n i n T a b l e I.

Un

f o r t u n a t e l y , the b r i t t l e c h a r a c t e r of p o l y s t y r e n e system was not i m p r o v e d on hydrogenation.

T h i s was the s t a r t i n g p o i n t for this

research—to

d e v e l o p a t o u g h p r o d u c t w h i l e m a i n t a i n i n g the i n h e r e n t heat resistance of the P V C H . S i n c e v i n y l c y c l o h e x a n e c o u l d not b e p o l y m e r i z e d b y c o n v e n t i o n a l free r a d i c a l i n i t i a t i o n , i n o u r l a b o r a t o r y , the o p t i o n of p o l y m e r i z a t i o n i n


3.

Heat Resistant

PENDELTON ET AL.

T a b l e I.

P h y s i c a l P r o p e r t i e s of P o l y s t y r e n e ( P S ) Poly (vinylcyclohexane) (PVCH)

Property

PS

Specific g r a v i t y

0.94

116.0

* P / C dl/gram

125.5

0.78 ( C H ) 6

M o l e c u l a r weight (M ) (light scattering) D i e l e c t r i c constant U l t i m a t e tensile X psi

0.61

6

265,000

w

10

vs. PVCH

1.04

R o c k w e l l hardness, " R " scale


29

Plastics

(C H ) 6

1 2

235,000

2.58

2.56

4.5 2.9 2.0 0.05 —

3.9 1.9 1.5 1.4 1.2

3

25°C 60°C 80°C 100°C 120°C Heat distortion temperat u r e , °C ( A S T M - 6 4 8 , 264 psi)

81.5

D y n s t a t i m p a c t i}/2 unnotched)

142.5

2.9 kg c m / c m

2.9 kg c m / c m

2

2

the presence of r u b b e r as d o n e to p r e p a r e i m p a c t styrene w a s not v i a b l e . M e l t b l e n d i n g of

PVCH

w i t h rubbery polymers

d i d not i m p a r t the

degree of toughness that c o u l d b e o b t a i n e d i n m e l t b l e n d i n g p o l y s t y r e n e w i t h rubbers.

T h e fact that n o i m p a c t m o d i f i c a t i o n w a s o b t a i n e d e v e n

w h e n the b l e n d e d r u b b e r was almost c o m p l e t e l y saturated i n d i c a t e d t h a t n o g r a f t i n g o n the r u b b e r w a s a c c o m p l i s h e d as is a s s u m e d i n p o l y s t y r e n e - r u b b e r b l e n d i n g to p r o d u c e i m p a c t polystyrene.

T h e s e factors p l u s

the l a c k of a n e c o n o m i c a l source of v i n y l c y c l o h e x a n e s h o w e d t h a t the best m e t h o d of m o d i f y i n g P V C H was to m o d i f y p o l y s t y r e n e a n d h y d r o genate this to the P V C H d e r i v a t i v e . W e b e l i e v e that a r u b b e r - m o d i f i e d p o l y s t y r e n e c o u l d not b e h y d r o genated efficiently.

E v e n a styrene-butadiene emulsion copolymer w i t h

l o w gel content c o u l d o n l y b e p a r t i a l l y h y d r o g e n a t e d

and then only

v e r y s l o w l y f o l l o w e d b y difficult catalyst r e m o v a l . Soluble copolymers

of styrene w e r e c o n s i d e r e d

h y d r o g e n a t i o n to i m p a c t P V C H

materials.

as c a n d i d a t e s

A n i o n i c diene

w i t h styrene w e r e chosen for s t u d y b e c a u s e the structure of

for

copolymers polydiene

portions c o u l d b e c o n t r o l l e d to g i v e flexible r u b b e r y segments o n h y d r o -


30


genation.

T h e p o l y d i e n e structures l i s t e d i n T a b l e I I a l l g i v e

flexible

to r u b b e r y p r o d u c t s on h y d r o g e n a t i o n . P o l y i s o p r e n e o n h y d r o g e n a t i o n gives a r u b b e r d i r e c t l y — a n a l t e r n a t ing ethylene-propylene polymer.

Polybutadiene can give polyethylene

o n h y d r o g e n a t i o n i f it is a l l 1,4 i n structure or a v a r i e t y of

flexible-to-

r u b b e r y e t h y l e n e - b u t e n e c o p o l y m e r s as the 1,2 content of the p o l y b u t a d i e n e is increased.

T h e s e p o l y d i e n e structures c a n b e i n c o r p o r a t e d as

segments i n a n i o n i c styrene c o p o l y m e r s . H y d r o g e n a t e d Diene P o l y m e r s

Table II. Downloaded by COLUMBIA UNIV on September 19, 2017 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0129.ch003

CH3

I

CH3

I

H

CHoC

CHCH2

C H 2 C H CH2CH2 n

>

n

Poly(L4-isoprene)

Alternating E P rubber H

—CH2CH=CHCH2—

—CH2CH2CH2CH2—

>

n

P o l y (1,4-butadiene)

Polyethylene H

—CH CH=CH—CH2— 2

—CH2CH—

n

>

m

I

CH CH Random

2

1,4-1,2-polybutadiene

CH2CH2CH2CH2

n

CH CH 2

m

I

CH

2

CH

3

R a n d o m e t h y l e n e - b u t e n e elastomer I n a d d i t i o n to the v a r i a t i o n i n d i e n e c o m p o s i t i o n a n d m i c r o s t r u c t u r e , a n i o n i c techniques also a l l o w a v a r i e t y of b l o c k c o p o l y m e r structures. W e i n v e s t i g a t e d three basic types of b l o c k structure.

U s i n g styrene a n d

b u t a d i e n e as the m o d e l system, t w o b l o c k structures s t u d i e d w e r e p u r e d i - a n d t r i b l o c k p r e p a r e d b y s e q u e n t i a l a d d i t i o n of t h e m o n o m e r s i n a butyllithium

initiated

styrene-butadiene-styrene

system, g i v i n g s t y r e n e - b u t a d i e n e ( S B S ) block polymers.

block polymers ( S B ) were hydrogenated. M

(SB)

and

In addition, mixed

T h i s t y p e of s t a r t i n g p o l y

m e r was p r e p a r e d b y a l k y l l i t h i u m i n i t i a t i o n w i t h b o t h m o n o m e r s present. T h e first b l o c k is a m i x t u r e of m o s t l y p o l y b u t a d i e n e w i t h some of the styrene r a n d o m l y d i s t r i b u t e d i n this segment (10 to 35% of t o t a l styrene c h a r g e d , d e p e n d i n g on c o m p o s i t i o n ) c o m p r i s i n g the second b l o c k

(16,

w i t h the r e m a i n i n g styrene o n l y T h e letter designations

17).

used

here for the v a r i o u s p r o d u c t s are b a s e d o n the d e s i g n a t i o n f o r the u n h y d r o g e n a t e d p r o d u c t s — S B S , S B , or S B

M

for s t y r e n e - b u t a d i e n e systems

w h e r e B is the t y p i c a l 90% 1,4- /10% 1-2-polybutadiene f r o m b u t y l l i t h i u m


3.

PENDELTON ET AL.

Heat Resistant

initiation i n hydrocarbons.

F o r p o l y b u t a d i e n e of h i g h e r 1,2 content the

d e s i g n a t i o n is, for e x a m p l e , S B ( 1 , 2 ) S . (1,2)

31

Plastics

I n a l l h i g h v i n y l products the

percent i n the p o l y b u t a d i e n e segment is a b o u t 50%.

The number

p r e c e d i n g the letters is the o v e r a l l styrene content p r i o r to h y d r o g e n a tion.

T h e hydrogenated

product

carries a n R after the

composition

i d e n t i f i c a t i o n , a n d this refers to c o m p l e t e h y d r o g e n a t i o n of b o t h the d i e n e a n d styrene portions.

F o r e x a m p l e as 2 5 S B - R is a f u l l y h y d r o M

g e n a t e d m i x e d b l o c k p o l y m e r of 25% styrene a n d 75% b u t a d i e n e . T h e h y d r o g e n a t e d p o l y m e r s i n a l l ranges w e r e transparent a n d h a d heat s t a b i l i t y far s u p e r i o r to the s t y r e n e - b u t a d i e n e counterparts.

The


i n h e r e n t t h e r m a l o x i d a t i v e s t a b i l i t y was d e m o n s t r a t e d b y r e p e a t e d ex t r u s i o n of u n s t a b i l i z e d p r o d u c t s w i t h o u t loss of c l a r i t y or decrease i n viscosity. and

T h e l e v e l of styrene content s t u d i e d was f r o m 10% t o 90%,

the properties of the h y d r o g e n a t e d

derivatives generally ranged

f r o m t o u g h r u b b e r y p r o d u c t s at l o w styrene to t o u g h , r i g i d , heat resistant p r o d u c t s at h i g h styrene content.

T h e p r o d u c t s o b t a i n e d i n these t w o

areas are d e s c r i b e d b e l o w . Laboratory

Procedure

A l l operations w e r e c a r r i e d out i n the absence of a i r u n d e r a r g o n . Styrene B l o c k P o l y m e r Synthesis. G L A S S W A R E . A l l glassware w a s d r i e d at 130°C i n a f o r c e d a i r o v e n o v e r n i g h t a n d c o o l e d to r o o m t e m p e r a t u r e u n d e r a n a r g o n p u r g e . T h e 12 oz a n d 28 oz " p o p " bottles w e r e c a p p e d i m m e d i a t e l y after c o o l i n g u n d e r a n a r g o n p u r g e , w i t h a neoprene l i n e r a n d a m e t a l p e r f o r a t e d c r o w n c a p . T h e 12-oz bottles are b o r o s i l i c a t e glass, a n d the 28-oz bottles w e r e soft glass. I n a l l cases, contents w e r e a d d e d to the bottles b y s y r i n g e needle. S O L V E N T S . Tetrahydrofuran (THF). T H F ( D u p o n t ) was d i s t i l l e d i n a s i m p l e d i s t i l l a t i o n setup, w h i c h h a d b e e n flamed out u n d e r a r g o n . To 1500 m l of the T H F , w h i c h was passed t h r o u g h m o l e c u l a r sieves, w e a d d e d 20 m l . styrene a n d e n o u g h 1.52V b u t y l l i t h i u m s o l u t i o n i n hexane to g i v e a p e r m a n e n t y e l l o w collor. A s m a l l f o r e r u n was d i s c a r d e d , a n d the T H F d i s t i l l e d d i r e c t l y i n t o 28-oz bottles, w h i c h w e r e c a p p e d a n d pressured w i t h argon. Cyclohexane. Pure grade cyclohexane (Phillips Petroleum C o . ) was passed t h r o u g h a c t i v a t e d L i n d e 3 A m o l e c u l a r sieves u n d e r a r g o n i n t o a stainless steel o x y g e n b o m b ( 9 g a l ) . It was d i s p e n s e d u n d e r pressure t h r o u g h a v a l v e c o n n e c t e d to p o l y e t h y l e n e t u b i n g w i t h a s y r i n g e needle attached. M O N O M E R S . Styrene. S t y r e n e ( E a s t m a n w h i t e l a b e l ) , 1200 m l , was p l a c e d i n a d r y 2-liter R . B . flask c o n t a i n i n g a T e f l o n - c o v e r e d m a g n e t i c stirrer. W h i l e s t i r r i n g u n d e r a r g o n , d i e t h y l ether, 200 m l ( a n h y d r o u s ) , and b e n z o p h e n o n e , 12 grams, w e r e a d d e d a n d t h e n 1.0 g r a m of s o d i u m i n s m a l l pieces. O n s t i r r i n g o v e r n i g h t , a d e e p b l u e c o l o r develops, i n d i c a t i n g that a l l i m p u r i t i e s are p u r g e d . W i t h o u t s t o p p i n g the s t i r r i n g , the flask was a t t a c h e d to a d r y , v a c u u m d i s t i l l a t i o n setup. T h e system was t h e n e v a c u a t e d a n d filled w i t h a r g o n t w i c e , a n d the v a c u u m was



32


b r o u g h t e v e n t u a l l y to 40 m m as the v a p o r pressure of t h e ether p e r m i t s . T h e ether was c o l l e c t e d i n the d r y ice t r a p a n d a f o r e r u n of 25-50 m l was c o l l e c t e d at 5 0 ° C a n d 40 m m . P u r e styrene was t h e n c o l l e c t e d ( 5 0 ° C / 4 0 m m ) , y i e l d i n g a p p r o x i m a t e l y 1 liter. T h i s was t r a n s f e r r e d to 12-oz c a p p e d bottles b y s y r i n g e needles, p u r g e d w i t h a r g o n , a n d stored i n a d r y ice chest. Butadiene. P h i l l i p s s p e c i a l p u r i t y b u t a d i e n e (99.5 m o l e %) w a s d i s t i l l e d f r o m the c y l i n d e r i n t o a d r y ice c h i l l e d 1700-cc b o m b . T h i s b o m b was t h e n i n v e r t e d a n d c o n n e c t e d to a 4' x 2 " stainless steel c o l u m n p a c k e d w i t h 3 A m o l e c u l a r sieves. ( 4 A sieves cause p o l y m e r i z a t i o n ; 3 A d o not.) T h e l i q u i d b u t a d i e n e was passed t h r o u g h this c o l u m n a n d m e t e r e d out s l o w l y (150 grams i n 15 m i n u t e s ) t h r o u g h a v e r n i e r needle v a l v e c o n n e c t e d to a syringe n e e d l e i n t o the p o l y m e r i z a t i o n bottles. Isoprene. M a t h e s o n p u r e g r a d e isoprene was passed s l o w l y t h r o u g h 3 A m o l e c u l a r sieves i n t o a d r y R . B . flask. T o this (500 m l ) w e a d d e d 50 m l of a 25% t r i i s o b u t y l a l u m i n u m s o l u t i o n i n hexane. T h e i s o p r e n e was d i s t i l l e d i n a s i m p l e d i s t i l l a t i o n setup a n d c o l l e c t e d i n 12-oz bottles w h i c h are c a p p e d a n d m a i n t a i n e d at 10 p s i a r g o n . A d d i t i o n to p o l y m e r i z a t i o n bottles was a c c o m p l i s h e d b y syringe. PURGING

SOLUTION

AND CATALYST

PREPARATION.

TO

a

dry,

12-oz

c a p p e d b o t t l e w e a d d e d 100 m l of b e n z e n e , 5 m l of «-methylstyrene a n d 5 m l of 1.52V b u t y l l i t h i u m i n hexane. T h i s m i x t u r e was w a r m e d to 50° C for one-half h o u r or u n t i l the d e e p r e d #-methylstyrene a n i o n color f o r m e d . It was k e p t u n d e r 10 p s i a r g o n a n d stored w i t h the styrene i n the d r y ice chest. T h e catalyst s o l u t i o n was p r e p a r e d b y a d d i n g 25 m l 1.5N b u t y l l i t h i u m ( F o o t e M i n e r a l C o . , i n h e x a n e ) to 250 m l of argon-degassed c y c l o h e x a n e i n a 12-oz bottle. T h e active b u t y l l i t h i u m c o n c e n t r a t i o n was d e t e r m i n e d b y the m e t h o d of G i l m a n ( 1 8 ) , except that T H F was u s e d instead of d i e t h y l ether. T h e r e a c t i o n flasks (50 m l E r l e n m e y e r ) w e r e d r y , a r g o n - f i l l e d , a n d c a p p e d w i t h s e r u m stoppers. T o each was a d d e d 10 m l T H F a n d 1 m l b e n z y l c h l o r i d e . F o u r m l of catalyst s o l u t i o n w e r e a d d e d to t w o of these and 8 m l to t w o more. A f t e r at least one m i n u t e , the solutions w e r e p o u r e d i n t o d i s t i l l e d w a t e r (100 m l ) , a n d the L i O H was t i t r a t e d w i t h s t a n d a r d a c i d to a p h e n o l p h t h a l e i n e n d p o i n t . T h e difference b e t w e e n the 4 m l a n d 8 m l a l i q u o t samples is the i n a c t i v e content of the catalyst s o l u t i o n . T h i s takes i n t o a c c o u n t a n y i m p u r i t i e s w h i c h m a y h a v e b e e n present i n the T H F or b e n z y l c h l o r i d e . T o t a l l i t h i u m content was deter m i n e d b y q u e n c h i n g 4 m l of the catalyst s o l u t i o n i n 100 m l of w a t e r a n d t i t r a t i n g w i t h s t a n d a r d a c i d . T h e m o l a r i t y of the catalyst s o l u t i o n i n a c t i v e b u t y l l i t h i u m is s i m p l y the t o t a l L i O H a c i d t i t r e less the i n a c t i v e L i O H titre. P O L Y M E R I Z A T I O N P R O C E D U R E . T h e bottles u s e d to store styrene, isoprene, p u r g i n g s o l u t i o n , catalyst s o l u t i o n , cyclohexane, a n d T H F are all m a i n t a i n e d u n d e r a p p r o x i m a t e l y 15 p s i a r g o n pressure. I n r e m o v i n g samples b y s y r i n g e , the bottles are i n v e r t e d , a n d the solutions are pressured i n t o the syringe. T h i s eliminates a n y c h a n c e of c o n t a m i n a t i o n b y a i r seepage a r o u n d the b a r r e l of the s y r i n g e , as sometimes h a p p e n s in normal syringe operation. A l l l a b o r a t o r y p o l y m e r i z a t i o n s w e r e r u n i n 28-oz bottles c o n t a i n i n g a T e f l o n - c o v e r e d m a g n e t i c s t i r r i n g b a r . C y c l o h e x a n e , 550 m l , was p r e s s u r e d



3.

PENDELTON ET AL.

Heat Resistant

Plastics

i n t o t h e bottle, a n d t h e solvent was degassed b y i n s e r t i n g a l o n g , 18 gage n e e d l e to t h e b o t t o m of the b o t t l e a n d b l o w i n g a r g o n t h r o u g h the r a p i d l y s t i r r i n g solvent a n d out a n 18 gage n e e d l e at t h e top. A t pressures b e t w e e n 10 a n d 25 p s i , t h e m a x i m u m flow rate i n s u c h a sys t e m is a p p r o x i m a t e l y 3 l i t e r s / m i n u t e . T h i s flow c o n t i n u e d f o r at least 15 m i n u t e s . T h e p r o p e r a m o u n t of styrene was a d d e d b y s y r i n g e , a n d a r g o n p u r g i n g was c o n t i n u e d for a f e w minutees longer. T h e m i x t u r e was t h e n c o o l e d to a p p r o x i m a t e l y 10 ° C , a n d , w h i l e s t i r r i n g , t h e p u r g i n g s o l u t i o n was a d d e d c a r e f u l l y u n t i l a s l i g h t c o l o r c h a n g e was o b s e r v e d — w a t e r w h i t e to a l i g h t y e l l o w or t a n . T h e b o t t l e was t h e n s h a k e n t o ensure t h a t all impurities were purged. If this is to b e a m i x e d b l o c k synthesis, b u t a d i e n e is a d d e d at this p o i n t a n d t h e n the catalyst. T h e f o l l o w i n g p r o c e d u r e describes a p u r e A B A b l o c k synthesis. W i t h t h e styrene p u r g e d , catalyst is a d d e d b y s y r i n g e i n a n a m o u n t w h i c h depends o n the final m o l e c u l a r w e i g h t d e s i r e d a c c o r d i n g t o the following equation: M o l e c u l a r weight

=

grams monomer moles c a t a l y s t

T h e b o t t l e is t h e n p l a c e d i n a 50 ° C w a t e r b a t h a n d is s t i r r e d b y a m a g n e t i c s t i r r i n g m o t o r u n d e r the b a t h for 3 hours. It is r e m o v e d a n d c o o l e d to n e a r r o o m t e m p e r a t u r e , w e i g h e d , a n d b u t a d i e n e is a d d e d f r o m the b u t a d i e n e d r y i n g c o l u m n . W h e n the d e s i r e d w e i g h t of b u t a d i e n e has b e e n i n t r o d u c e d , t h e b o t t l e is r e t u r n e d to t h e b a t h , a n d t h e p o l y m e r i z a t i o n is a l l o w e d to p r o c e e d for 5 hours. F o r the last b l o c k , a s t y r e n e - i n - c y c l o h e x a n e s o l u t i o n is p r e p a r e d a n d p u r g e d s i m i l a r to the s t a r t i n g s o l u t i o n , a n d the p r o p e r a m o u n t is a d d e d b y s y r i n g e d i r e c t l y i n t o the p o l y m e r i z a t i o n b o t t l e at 5 0 ° C . T h i s p o r t i o n of the p o l y m e r i z a t i o n is a l l o w e d to p r o c e e d for a n a d d i t i o n a l 3 hours a n d is t e r m i n a t e d b y t h e a d d i t i o n of a f e w m i l l i l i t e r s of m e t h a n o l . T h e p o l y m e r s are p r e c i p i t a t e d i n m e t h a n o l i n a W a r i n g B l e n d o r , s t a b i l i z e d w i t h 1% N - p h e n y l - j 8 - n a p h t h y l a m i n e a n d d r i e d i n a v a c u u m oven. If the p r o d u c t is h y d r o g e n a t e d , the q u e n c h w i t h m e t h a n o l is n o t d o n e a n d the c y c l o h e x a n e s o l u t i o n of the p o l y m e r is u s e d d i r e c t l y . H y d r o g e n a t i o n C a t a l y s t P r e p a r a t i o n . A 0 . 0 8 1 M s o l u t i o n of h y d r o g e n a t i o n catalyst (based o n cobalt) was p r e p a r e d b y a d d i n g 23.6 grams of c o b a l t ( I I ) 2-ethylhexanoate c y c l o h e x a n e s o l u t i o n (12.0% c o b a l t w / w , H a r s h a w C h e m i c a l C o . ) over a p e r i o d of 90 m i n u t e s t o a s o l u t i o n of 18.8 grams (0.165 m o l e ) of t r i e t h y l a l u m i n u m i n 495 grams of c y c l o h e x a n e ( T e x a s A l k y l s ) . A d d i t i o n is to a c a p p e d b o t t l e w i t h v e n t i n g . T h e a l u m i n u m - t o - c o b a l t r a t i o w a s 3:1. A n i c k e l - b a s e d system c a n b e p r e p a r e d b y s u b s t i t u t i n g n i c k e l ( I I ) 2-ethylhexanoate f o r the c o b a l t octoate. H y d r o g e n a t i o n P r o c e d u r e . N i n e t y - f i v e p o u n d s of a c y c l o h e x a n e solution c o n t a i n i n g 12.5 p o u n d s of a 40 S B S p o l y m e r (rj = 0.79 d l / g r a m , b e n z e n e 2 3 ° C ) w e r e c h a r g e d to a 2 0 - g a l autoclave. T h e reactor was p r e s s u r i z e d t w i c e to 50 p s i g w i t h h y d r o g e n a n d 750 m l of a 0 . 1 9 M c o b a l t catalyst was a d d e d . T h e h y d r o g e n a t i o n w a s c o n d u c t e d at a h y d r o g e n pressure of 3500 p s i at 2 5 0 ° C f o r 80 m i n u t e s . T h e p r o d u c t sWc


34


i n s o l u t i o n at 5 0 ° - 6 0 ° C was m i x e d w i t h 10% aqueous n i t r i c a c i d to extract catalyst residues a n d p r e c i p i t a t e d i n m e t h a n o l . T h e w h i t e p r o d u c t h a d a viscosity of 0.85 d l / g r a m i n D e c a l i n at 135°C (rj ). T h e r e was n o u n s a t u r a t i o n , either a l i p h a t i c or a r o m a t i c , d e t e c t e d b y i n f r a r e d analysis o n a P e r k i n - E l m e r r e c o r d i n g g r a t i n g spectrophotometer. A film was cast f r o m hot c y c l o h e x a n e o n t o N a C l plates, a n d n o a b s o r p t i o n was o b s e r v e d at 960 c m (£rans-l,4-polybutadiene), 910 c n r (1,2p o l y b u t a d i e n e ) , or 690-695 c m ( p o l y s t y r e n e ) . P r e p a r e d standards s h o w e d that less t h a n 0.5% a l i p h a t i c or a r o m a t i c u n s a t u r a t i o n c a n be r e a d i l y observed. SX)/c

1

1

- 1


T a b l e III.

R e t e n t i o n of T e n s i l e S t r e n g t h at E l e v a t e d T e m p e r a t u r e s Tensile

Polymer

Vsp/c

T, °C

psi

1,4-PBde-R

1.73

25 75

3160 1180

10SB -R

1.72

25 75

3440 1940

15SB -R

1.64

25 75

4240 2740

20SB -R

1.74

25 75

2770 2000

25SBS-R

1.62

25 75

3030 2420

40SBS-R

1.10

25 100

4500 1500

M

M

M

Results Flexible

Hydrogenated

Styrene-Diene

Polymers.

These

hydro

genated styrene b u t a d i e n e p o l y m e r s w i t h less t h a n 50% styrene are t o u g h , p u n c t u r e resistant, clear, elastomeric properties.

flexible

complete

alphatic.

h a v e true

T h e heat resistance i m p a r t e d b y the P V C H seg

ments is s h o w n i n T a b l e I I I . shows

plastics; c e r t a i n m e m b e r s

A s i n d i c a t e d e a r l i e r the d e s i g n a t i o n - R

h y d r o g e n a t i o n of a l l u n s a t u r a t i o n , b o t h a r o m a t i c a n d

T h e r e t e n t i o n of tensile s t r e n g t h at e l e v a t e d temperatures is

d i r e c t l y r e l a t e d to the increase i n P V C H content.

A t 40% P V C H

the 40 S B S - R ) a tensile strength of 1500 p s i g was o b s e r v e d

(for

e v e n at

100°C. T h e effects of b l o c k s t r u c t u r e a n d m i c r o s t r u c t u r e a n d the o v e r a l l effect of

hydrogenation

illustrated i n T a b l e I V .

i n the l o w

styrene c o n t a i n i n g p o l y m e r s

are

T h e d a t a s h o w that the u n h y d r o g e n a t e d

SB


3.

PENDELTON ET AL.

Table IV.

Heat Resistant

35

Plastics

Effect of Hydrogenation and Block Structure in 2 5 % Styrene-Diene Polymers Tensile

Yield, psi

Vsp/ci


No.

Polymer

dl/gram

Elongation,

Ultimate, psi

IER,°

%

%

1

25SB

0.98

—

30

1300

6

25SBS-R

1.62

1780

4550

800

75

7

25SB(1,2)S-R

.94

180

>2570

>1300

94

1.39

240

1390

1000

97

8

M

25SIS-R

High

Immediate elastic recovery from 100% extension

a

Table V .

Physical Properties Rigid Hydrogenated SB Polymers Tensile

No.

Polymer

Vsp/c, Yield, dl/gram psi

Ultimate, psi

Elongation,

%

Flex. Mod. HDT, °C psi X 10

a

3

Impact, ft lbs/in

6

1

56SB -R

1.67

2200

3500

445

—

114

NB

1.47

3400

3800

100

150

129

1.9 1.9

M

2

70SB -R

3

75SB -R

2.10

3560

3610

20

160

136

4

80SB -R

1.13

—

4800

10

260

138

.9

5

90SB -R

.89

5560

5

—

132

.2

6

70SB-R

.86

— —

4730

5

320

140

.4

M

M

M

M

7

70SBS-R

1.29

—

4690

6

280

138

1.1

8

70SB(1,2)S-R

1.31

3480

3190

9

200

140

1.3

9

75SBS-R

1.10

4750

Polymerization Reactions and New Polymers

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