POLYMER LETTERS VOL. 2, PP. 873-876 (1964)

THE PYROLYSIS OF ELASTOMER-METAL HALIDE MIXTURES

W e have surveyed the behavior upon pyrolysis of elastomers mixed with a variety of inorganic compounds. The chlorides of nickel, cobalt, and copper were reduced t o the free metals by this treatment, and a sub- stantial carbonaceous, hydrogen-poor residue was retained in these cases . The mixtures of cis-4 polybutadiene (Phillips Petroleum Co.) or EPR-404 (60% ethylene - 40% propylene copolymer, Enjay Chemical Co.) with the inorganics were prepared by a conventional milling procedure. The pyrolyses were carried out in a simple tube furnace, either under ni- trogen or in vacuum, at temperatures at which the elastomers normally are degraded. The residues from the pyrolysis were weighed and ana- lyzed for carbon and hydrogen by combustion techniques. X-ray diffrac- tion using a standard goniometer was employed to identify the inorganic components of the residues.

A few easily reducible compounds of metals near the end of the first transition ser ies behaved in an interesting manner, a s shown in Table I. The chlorides of copper, cobalt, and nickel were reduced t o the free metal. Accompanying th i s reduction was the retention of considerable organic matter in the residues, which assumed the form of black, brittle solids, easily ground to fine powders. Extensive dehydrogenation oc- curred, as is shown by the increase in carbon to hydrogen weight ratios above the eight t o one of polybutadiene or the six t o one of the ethylene- propylene rubber. The sharpness of the peaks in the x-ray diffraction traces indicated that the metals were not present in extremely fine parti- c le s i zes . When mixtures of fine metallic powders with the elastomers were pyrolyzed, no appreciable retention of organic material occurred. On treatment under our conditions in the absence of polymer, nickel(I1) chloride, cobalt(I1) chloride, and copper(1) chloride were unchanged, but copper(I1) chloride was converted to copper(1) chloride.

of behavior was shown by iron(I1) chloride, iron(II1) oxide, cobalt(II1) ox- ide, and vanadium(V) oxide. These compounds were not converted to the free metal, but appreciable retention of dehydrogenated organic mat- ter did occur.

Since many of the inorganic compounds showed appreciable volatility under our conditions, the amount of residue has little significance. The composition of the residues varied only slightly with large increases in the initial metal halide-polymer ratio. Both the saturated and unsaturat- ed polymers behaved in the s a m e fashion, and the change from a nitrogen atmosphere to a vacuum did not alter the course of the reaction.

Particularly noticeable in the reduction of copper(1) chloride was the

Copper(1) oxide was reduced to the free metal, and an intermediate type

873

TA

BL

E I

Pyro

lysi

s of

Met

al H

alid

e-E

last

omer

Mix

ture

s (4

OO

0C.,

1 hr

., in

vac

uum

)

%C

%

H

C/H

g.

ino

rgan

ic

mol

es i

norg

anic

g

. re

sidu

e x

100

Met

al (

a)

or

10 g

. po

lym

er

mol

es p

olym

er

g. (

poly

mer

+ in

orga

nic)

co

mpo

und

in r

esid

ue

Cis

-4 +

CuC

12

1.5

3.0

4.5

6.0

1.5

g. C

uCl2

+ 1.

5 g.

NiC

12

EPR

-404

+ C

uC12

1.

5 3.

0 (C

u2C

12)

4.5

6.0

1.5

g. C

uC12

+ 1.

5 g.

NiC

12

Cis

-4 +

NiC

12

1.5

3.0

4.5

6.0

.06

.12

.18

.24

.12

.04

.08

.12

.16

.08

.06

.12

.18

.24

6.7

13

17

20

15 6.7

8.7

12

13

12 6.4

20

17

20

cu

cu

c

u

Cu

+ N

i

cu

(b)

cu

c

u

cu

c

u

Ni +

Cu

25.8

0 34

.09

24.6

5 25

.26

34.1

6

19.1

2 10

.39

20.7

6 22

.58

18.4

8

28.8

3 39

.15

30.1

4 32

.29

1.16

22

.2

2.53

13

.5

1.41

17

.5

1.30

19

.5

2.05

16

.7

1.33

14

.4

0.47

22

.2

1.26

16

.5

1.39

16

.3

P 4

1.31

14

.1

F 6 r

1.41

20

.4

1.56

25

.2

2 1.

54

19.6

1.

56

20.7

EPR

-404

+ N

iClz

1.

5 3.

0 4.

5 6.

0

Cis

-4

3.0

g. C

uzC

Iz (d

)

3.0

g. N

iCIz

(dl

.04

.08

.12

.16

.08

.12

6.7

10

14

20

25

25

V

0

Ni

24.3

5 1.

24

19.6

r cc

Ni

19.6

9 0.

70

28.1

N

i 25

.60

0.94

27

.2

W

Ni

25.7

7 1.

02

25.3

4

+I

m

cu

44

.16

1.61

27

.5

Ni

45.7

5 2.

05

22.4

Cis

-4

3.0

g. C

oClz

.1

2 23

c

o

48.3

4 1.

82

26.7

3.

0 g.

FeC

lz

.13

19

FeC

l 18

.86

1.79

11

.5

3.0

g. C

U~

O(

~)

.1

1 (g

) c

u

9.75

0.

53

18.4

3.

0 g.

Fe2

03

.. 1

0 13

A

mor

phou

s 9.

27

0.66

14

.0

3.0

g. C

0203

.1

0 22

A

mor

phou

s 18

.75

0.77

24

.4

3.0

g. VzO5

.09

20

Am

orph

ous

13.1

7 0.

88

15.0

3.

0 g.

NiC

Iz'"

) .1

2 20

N

i 35

.47

1.30

27

.3

3.0

g. N

iCIz

(f)

.12

25

Ni

47.2

9 3.

94

12.0

(")I

dent

ifie

d by

x-r

ay t

echn

ique

. (b

)Chl

orin

e = 0

.91%

(ini

tial

ly 1

2.2%

).

(')C

hlor

ine

= 0

.50%

(ini

tial

ly 1

2.6%

).

(dl N

itrog

en a

tmos

pher

e.

("Si

x ho

urs.

(f

) 35

OoC

. (g

)Flo

wed

out

of w

eigh

ed t

ube.

876 POLYMER LETTERS

formation of a copper mirror within the pyrolysis tube. Whether the cop- per chloride itself migrated and was reduced on the walls of the tube or whether volatile reduced copper species were formed is not clear. It is reasonable that the reductions are caused by free radicals from the poly- mer decomposition, perhaps through formation of unstable metal alkyls.

Most of the inorganic materials surveyed were largely unaffected by this treatment. Their residues consisted of the starting material or thermal degradation products; carbon usually amounted to less than five percent of t hese samples. The compounds exhibiting th i s behavior in- cluded lithium chloride, potassium chloride, calcium chloride, calcium oxide, boric acid, aluminum chloride, aluminum oxide, tin(I1) chloride, zinc chloride, mercury(I1) chloride, lanthanum chloride, titanium dioxide, chromium(II1) chloride, manganese(I1) chloride, manganese dioxide, and nickel(I1) oxide.

M. Berger T. A . Manuel

Central Basic Research Laboratory E s s o Research and Engineering Company Linden, New Jersey

Received May 14, 1964 Revised June 8, 1964