Patented Apr. 11, 1950
2,503,252
UNITED STATES PATENT OFFICE
2,503,252
HALOGENATION OF POLYMERS
Maurice L. Ernsberger, Wilmington, Del, as
signor to E. I. du Pont de Nemours & Company,
Wilmington, DeL, a corporation of Delaware
No Drawing. Application June 27, 1947,
Serial No. 757,684
12 Claims. (01. 260-943)
1
This invention relates to substitution halogena
the azonitrile, increased and amounted to over
0.3 part per minute for approximately an hour
after ‘the addition of the azonitrile. The solu
tion was then poured into 800 parts of methanol
and the product which separated was further
washed with methanol and dried. The yield of
chlorinated polymer of ethylene was 42.5 parts
and the product had a chlorine content of 53.9%.
Films pressed from the product at 120° C. were
tion of high molecular weight hydrocarbon ma
terial.
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.
The substitution halogenation of ethylene poly
mer has heretofore been carried out by reac
tion of the polymer with free halogen optionally
in the presence of halogen carriers, such as alu
minum chloride or ferric chloride as described
in U. S. 2,183,556. The introduction of substan
tial amounts of halogen by the latter method re
quires periods of up to several days.
This invention has as an object an improved
process for the chlorination of ethylene polymer.
Another object is an improved process for the
substitution halogenation of aliphatic polymeric
materials which contain a plurality of -CI-Ia—
groups. Other objects will appear hereinafter.
These objects are accomplished by the halo
genation of an addition polymer containing a
v
quite pliable.
In comparison with the above example, Ex
amples 4 and 5 of Fawcett U. S. Patent 2,183,556
indicate that 100 hours is required to obtain a
chlorine content of 53.5% under comparable con
15 ditions except that no catalyst was employed.
Example II
In an opaque container were placed 480 parts
of water and 60 parts of solid ethylene‘polymer
plurality of -CH:- groups, particularly ethylene 20 (relative viscosity 1.138 measured at 85° C. using
polymer, with a halogen having an atomic num
ber of l8n-l where n is an integer from 1 to 2
0.125 gram polymer in 100 cc. of xylene) which
was su?iciently ?ne to‘ pass through a 40-mesh
(i e. chlorine or bromine), using as a catalyst or
screen. A small amount of dispersant, sodium
initiator for the reaction an azo compound hav
dodecylsulfate, was added to enable the water to
ing both valences of the azo group (—-N=N—) at 25 wet the ethylene polymer. The mixture was
tached to different carbons at least one of which
stirred and the air removed by flushing with
is a tertiary carbon aliphatic in kind which is
nitrogen. Chlorine was passed into the mixture
in turn joined to a negative monovalent radical,
and after 5 minutes, 1.2 parts of alpha,alpha'
through a carbon of said radical, which latter
azobis<alpha,gamma-dimethylvaleronitrile) was
carbon has its three remaining valences satisfied 30 added. Introduction of chlorine into the mixture
by elements of atomic number 7 to 8 (i. e. oxygen
was continued for one hour, the temperature be
and nitrogen). The negative monovalent radi
ing maintained at ?ll-63° C. The product was
cals referred to are nitrile, carbonamide, and
carbalkoxy groups all of which are hydrolyzable
to carboxyl groups.
separated and washed with water, dilute sodium
carbonate and finally with water and dried. The
mers of ethylene having a molecular weight in
excess of 1000.
as rapid.
The following examples in which parts are by
weight are illustrative of the invention.
the process of this invention are aliphatic azo
yield of chlorinated polymer of- ethylene was 70
The ethylene polymers employed in the process 35 1331:; The product had a chlorine content of
of this invention are advantageously the solid
13. 0.
high molecular weight polymers of ethylene de
when ethylene polymer is chlorinated in aque
scribed in Fawcett et a1. U. 8. 2,153,553. The
ous dispersion in the absence of an azo initiator
process is, however, applicable in general to poly
the rate of chlorine absorption is only about half
Example I
A solution of 20 parts of ethylene polymer
(melting point about 110° C.) in 584 parts of car
bon tetrachloride was heated under re?ux (about
The azo compounds generically applicable in
compounds which have both valences of the azo,
45 -N=N-, group attached to different carbons at
least one of which is a tertiary aliphatic carbon
which is in turn joined to a negative monovalent
radical through a carbon of said radical, which
latter carbon has its three remaining valences
77° C.) with stirring in an opaque container.
Chlorine was passed through the solution at the
satis?ed by elements of atomic number of seven
to eight, 1. e., oxygen and nitrogen. The negative
rate of approximately 0.6 part per minute and
monovalent radicals are the nitrile, carbalkoxy
- 0.4 part of alpha,alpha'-azobis(alpha,gamma-di
and carbonamide groups, all of which are hy
drolyzable to carboxyl groups.
methylvaleronitrile) was ‘added. _Absorption of
chlorine, which was negligible before addition of 55 Examples of the azo catalysts useful in this
9,808,! 82
3
4.
invention are alphaalphw-azobismlphaxamma
dimethylvaleronitrile), alpha,alpha'-azodiisobu
tyronitrile, dimethyl, diethyl, and dihexyl alpha,
alpha'-azodiisobutyrates, alpha,alpha’-azodiiso
butyramide, 1,1'-azodicyc1ohexanecarbonitrile,
a1pha,alpha’-azobis(alpha - cyclopropylpropioni
trile), alpha,alpha'-azobis(alpha-phenylpropio
nitrile) ,
alpha- (carbamyl-azo) isobutyronitrile,
a1pha,alpha'-azobis- (alpha-methyl,gamma - car
boxybutyronitrile), diethyl alpha,alpha'-azobis
(alphaJamma-dimethylvalerate), and alpha,
light in place of an azo initiator, chlorination
is retarded because the precipitated polymer
tends to shut off the light.
The products obtained by the process of this
invention are useful in many applications. The
speci?c application depends upon properties of
the halogenated material. For example, the hal_
ogenated long chain hydrocarbons of high mo
lecular weight are useful as electrical insulators
10 in electrical applications, and as ?lm-forming
materials more generally.
The foregoing detailed description has been
ide).
given for clearness of understanding only and
The more useful azo compounds have nitrile
no unnecessary limitations are to be understood
(cyano) groups on the carbons alpha to the axe
therefrom. The invention is not limited to the
nitrogens. The radicals which are bonded to the
exact details shown and described for obvious
we nitrogens are generally free from carbon-to
modifications will occur to those skilled in the art.
carbon unsaturation, and the more active cat
What is claimed is:
alysts have radicals of four to nine carbons at
1. In the chlorination of ethylene polymer, the
tached to each azo nitrogen. The azo compounds 20 improvement wherein there is employed as ini
are used in the halogenation process of this in
tiator for the chlorination alpha,alpha’-azobis
(alpha,gamma-dimethylvaleronitrile) .
vention in amounts of 0.005 to 5% based on the
total weight of hydrocarbon to be halogenated,
2. In the chlorination of ethylene polymer, the
although amounts of from 0.1 to 2% usually give
improvement wherein there is employed as ini
a satisfactory rate of reaction. They may be 25 tiator for the chlorination an aliphatic azo com
added all at once or portionwise during the re
pound having both valences of the azo, —N=N-,
action.
group attached to different tertiary aliphatic
The halogens particularly useful in the sub
carbons which carbons are each bonded to a nega
stitution halogenation described in this inven
tive monovalent radical through carbon of said
tion are chlorine and bromine. Halogenating 30 radical which latter carbon has its remaining
agents such as sulfuryl chloride may also be
valences satis?ed by elements of atomic number
used. In view of its availability and low cost,
of seven to eight.
chlorine is usually preferred.
3. In the chlorination of ethylene polymer in
aqueous suspensions, the'improvement wherein
While the process of this invention is of par
ticular importance in the chlorination of ethyl 86 there is employed as initiator for the chlorina
ene polymers, it is applicable in general to addi
tion an aliphatic azo compound having both
tion polymers of molecular weight of 1000 or
valences of the azo, -—-N=N—-, group attached to
over and containing a plurality of —-CH2—
different tertiary aliphatic carbons which carbons
alpha' - azobis(alpha,gamma - dimethylvaleram
groups, including polyvinyl chloride, rubber,
polychloroprene, copolymers of styrene with bu
tadiene and similar aliphatics.
In view of the
utility of halogenated polymer of ethylene, the
are each bonded to a negative monovalent radical
through carbon of said radical which latter car
bon has its remaining valences satis?ed by ele
ments of atomic number of seven to eight.
4. In the chlorination of ethylene polymer, the
improvement wherein there is employed as ini
chlorination of ethylene polymers constitutes a
preferred embodiment of this invention.
The reaction, which takes place in the liquid
tiator for the chlorination an aliphatic azo com
phase, may be carried out at room temperature
or elevated temperatures. In general the tem
pound having both valences of the azo, -—N=N--,
group attached to diiferent tertiary aliphatic
perature employed is that at which the catalyst
carbons which carbons are each bonded to a
undergoes decomposition at an appreciable rate.
nitrile group.
For the sac catalysts, this temperature is usually 50 " 5. In the replacement, by halogen of atomic
between 40 and 150° C., although temperatures
number 18n-1 where n is an integer from 1 to 2.
as high as 200° C. may be employed. Lower tem
of hydrogen of an addition polymer of molecular
peratures such as below 40° C. to as low as —50°
weight above 1000 and containing a plurality of
or lower may be used when light of wave length
--—CH-:— groups, the improvement wherein there
of between 3100 L and 4000 A. is used in con 55 is employed as initiator for the halogenation
alpha,alpha’ - azobis(allpha,gamma - dimethyl Junction with the catalyst.
valeronitrile) .
The time of reaction is dependent upon the
6. In the replacement, by halogen of atomic
temperature and the amount of halogenation de
number 18n-1 where n is an integer from 1 to 2,
sired in the product. In general, reaction periods
ranging from a few minutes to a few hours, for 60 of hydrogen of an addition polymer of molecular
weight above 1000 and containing a plurality of
example ?ve minutes to ten hours, will be em
-—-CH2—- groups, the improvement wherein there
ployed.
>
is employed as initiator for the halogenation an
The reaction- may be carried out in a solution
aliphatic azo compound having both valences of
in which the solvent for the polymer is an inert
material, such as carbon tetrachloride, trichloro 65 the azo, —N=N—, group attached to diiferent
tertiary aliphatic carbons which carbons are
ethylene, and tetrachloroethane. or the polymer
may be suspended in a medium, e. g. water, which
each bonded to a negative monovalent radical
is essentially non-reactive towards halogen un
through carbon of said radical which latter car
der the conditions employed. In the preparation
bon has its remaining valences satisfied by ele
of highly chlorinated products, e. g. chlorinated 70 ments of atomic number of seven to eight.
polymers of ethylene containing 53 to 63% chlo- ‘
7. In the replacement, by halogen of atomic
rine, by the solution method the chlorinated
number 18n-1 where n is an integer from 1 to 2,
polymer may separate from solution but this does
of hydrogen of an addition polymer of ‘molecular
not interfere with the chlorination. In contrast,
weight above 1000 and containing a plurality of
when such chlorinations are carried out using 15 --CH'.-— groups. the improvement wherein there
asoaasa
‘
.
~h employed as initiator for the halogenation an
aliphatic aao compound having both valences oi’
three remaining vaiences satis?ed by elements oi‘
the no, -N=N—, group attached to diiierent
tertiary aliphatic carbons which carbons are each
10. In the replacement, by halogen of atomic
bonded to a nitrile group.
8. In the replacement. by halogen oi’ atomic
number Ian-1 where n ‘is an integer from 1 to 2,
- of hydrogen of an addition polymer of molecular
weight above 1000 and containing a plurality of
—CH:— groups, the improvement wherein there
is employed as initiator for the halogenation an
aliphatic azo compound having both valences of
the azo, --N=N—, group attached to‘carbons at
least one of which is a tertiary aliphatic carbon
which is in turn joined to a negative monovalent
radical, through a carbon of said radical, which
latter carbon has its three remaining valences
satis?ed by elements of atomic number seven to
eiaht.
I
9. In the replacement, by halogen of atomic
number 180-1 where n is an integer from 1 to 2,
to! hydrogen of an addition polymer of molecu
-lar weight above 1000 and containing a plurality
of —CH:- groups. the improvement wherein
there is employed as initiator for the halogena
tion an arc compound having both valences of
the 830,- --N=N—, group attached to diirerent
carbons at least one of which is a tertiary carbon
aliphaticincharacterwhichisinturnjoined
to a negative monovalent radical, through a car
bonctsaidradicaLwhiehlattercarbonhasits
atomic number seven to eight.
.
number 18n-1_where n is an integer from 1 to 2,
of hydrogen of ethylene polymer, the improve
ment wherein there is employed as initiator for
the halogenation a1pha,alpha' - azobis(alpha, ~
gamma-dimethylvaleronitrile) .
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11. In the replacement, by halogen of atomic
number 18n-1 where n is an inteser'from l to 2.
of hydrogen oi’ ethylene polymer, the improve
ment wherein there is employed as initiator for.
the halogenation an aliphatic azo compound hav
ing both valences of the $10, —N=N-, group
attached to di?erent tertiary aliphatic carbons
which carbons are each bonded to a nitrile group.
12. In the replacement, by halogen of atomic
number 18n—1 where n is an integer from 1 to 2,
of hydrogen of ethylene polymer, the improve
ment whereinthere is employed as initiator for
the halogenation an aliphatic azo compound hav
ing both valence's of the am, -N=N-, group at
tached to di?erent tertiary aliphatic carbons
which carbons are each bondedto a negative
monovalent radical through carbon or said
radical, which latter carbon has its remaining
valences satisfied by elements of atomic number
of seven to eight.
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MAURICE L. ERNQBERGER.
No
cited;
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