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Nov. 5, 1946.
A. J. GRACIA
METHOD OF REMOVING INHIBITORS
'Filed Aug. 7, 1941
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2,410,779
Patented Nov. 5, I
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2.410.719‘ -
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ivra'rnon or nmuovmo mnmrrons
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Albert J. Gracia, Cuyahoga Falls, Ohio, assignor ‘
to Wingfoot Corporation, Akron, Ohio, a cor
poration oi’ Delaware
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Application August 7, 1941, Serial No. 405,803
8 Glaims. (Cl. 202—39)
This invention relates to an improved method
of removing polymerization inhibitors from mon
omeric substances prior to the employment of the
latter in the preparation of polymers. More par
2
I to distill the butadiene.
The inhibitors usually,
employed are highly soluble in these “high boll
ers” andit is found that as much as 50 tons of
ticularly, the invention relates to the removal of
polymerization inhibitors from butadiene, a con-,
inhibited butadiene may be distilled through 5
gallons of solvent before renewal is indicated.
Among inhibitor solvents which may be thus
employed are the following: dlbutyl citrate, di
stituent of many polymers.
It is well known that the substance butadiene
enters into the composition of many copolymers,
particularly those having rubber-like properties
.
does not vaporize at the temperatures required
10
butyl phthalate, butyl stearate, dlethyl phthalate,
tributyl phosphate, tricresyl phosphate, and other
and hence important as substitutes for natural
similar esters often employed as plasticizers in
rubber. Monomeric butadlene is a gas at nor
synthetic resins and the like. In general, it may
mal temperatures and is customarily stored in
be said‘ that any stable ester having a boiling
large tanks under pressure, where it is main
point between 500 and 700° F. at atmospheric‘
tained in liquid form. Since it possesses the 15 pressure may be employed, the chief requisite
property of self-polymerization, itis necessary to
being that the solvent shall not be volatile un
incorporate therein a polymerization inhibitor
der the conditions of distillation.
,
in order that the substance shall not polymerize
The method may be carried out in any suit
during storage. Necessarily, also, this inhibitor
able apparatus, one such being illustrated in the
must be removed before the butadiene is sub 20 accompanying drawing in which a boiler l is sur
:lected to polymerizing conditions, otherwise poly
rounded at its lower end with a steam jacket
merization is prevented or is very slow and any
2 into which steam is admitted through a pipe
rubber formed will have a low extrusion plas
3 and condensate is removed ‘through an outlet
ticity indicating a dimcultly workable'materlal. 4. In the lower part of the still is a body of
Since the butadiene is a gas under normal con 25 high-boiling solvent 5 into which liquid buta
ditions, it would appear that the butadiene could
diene is conducted through a line 6, the ?ow be
be readily distilled from the inhibitor, which is
ing controlled by means of a ?oat control ‘I. The
usually a solid. However, difficulties are encoun
-butadiene or other monomer is admitted at the
tered in performing such distillation ‘and it is an
bottom of the still and bubbles up. through the
object of the present invention to overcome such 30 solvent body 5 where it loses its inhibitor content. '
The vapors of the puri?ed monomer are then led‘
When the butadlene is distilled from the ‘in
off through the duct 8 to a condenser.
hibitor, this inhibitor, such as phenyl beta naph
When the butadiene or ether monomer con
thylamine, concentrates in the undistllled bu
tains
phenyl beta naphthylamine gas inhibitor,
tadiene and gradually builds up until the limit
and at present this is the substance most widely
01’ solubility is reached, whereupon some solid in
employed as a polymerization inhibitor, tests of
hibitor is thrown down. Continued distillation
the distilled material by means of ultra violet
then results in sublimation of the inhibitor in
light show almost no ?uorescence when the pres
thecondenser where, of course, it contaminates
ent method is employed. Fluorescence under
the distilled butadiene. The presence of Water in, 40 ultra violet light is an extremely sensitive test
the still does not overcome this dimculty but,
for phenyl beta naphthylamine. Butadiene dis
instead, complicates the situation due to the fact
tilled without the aid of a solvent or in the
that water induces the formation of some small
presence of water shows pronounced ?uorescence
amount of polymerized butadiene. The water
in the condenser, thus indicating that the dis- _
does not wet the inhibitor and the solid inhibitor
tillatlon was entirely ine?‘ective for the purpose
and polymer form a gum which ?oats at the hu
indicated, namely, to remove inhibitor prior. to
tadiene-water inter phase and tends to clog up
polymerization of the butadene.
and coat the still boiler.
As will be apparent, the method is also appli
It has now been found, in accordance with the
cable to the distillation of other normally gase»
principles of this invention, that all of these
ous monomeric materials intended for use in poly
dii?cultles may be avoided and a clean separa
merlzations,
such as vinyl chloride, the solvent
tion of monomer and inhibitor e?ected ii" there
employed being selected so as to have a boiling is placed in the still a quantity of a high-belle
point well above the temperature necessary to
ing liquid, such as one of those commonly used
effect distillation of the particular monomer un
a.“ plass.ilr.~irers. Such a liquid may be any which 55 der treatment.
di?lculties.
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2,410,779 '
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While there has been described above a pre
ferred embodiment of the invention, it will be
apparent to those skilled in the art that various
modi?cations and changes may be made therein
without departing from the spirit of the inven
‘
the vapors of the puri?ed butadiene from the sur
g' face of the body of liquid and condensing the
ution or from the scope of the appended claims.
I claim:
A
_
' 1. A method of removing a. polymerization in
vapors.
~
5. A method of removing substantially vall
phenyl beta naphthylamine from butadiene which
comprises bubbling the butadiene containing the ,
phenyl beta naphthylamine up through a body of
high-boiling solvent for the phenyl beta naphthyl
amine to dissolve substantially all of the latter
hibitor from a normally gaseous monomeric sub
from the butadlene, leading 03 the vapors of
10
stancewhich comprises bubbling the monomer
the puri?ed butadiene from the surface of the
containing the inhibitor up through a body of
body of liquid and condensing the vapors.
high-boiling solventfor, said inhibitor, leading off
6. A method of removing a normally solid pcly- _
the vapors of the puri?ed monomeric substance 7
merization
inhibitor from butadiene which com
from the surface of the body of liquid and con
prises bubbling the butadiene containing the in
15
densing the vapors.
hibitor up through a body of liquid dibutyl citrate
2. A method of removing a polymerization in
to remove substantially all of the inhibitor from
- hibitor from a normally gaseous monomeric sub
the butadiene. leading off the vapors of the puri
stance which comprises bubbling the monomer
?ecl butadiene from the surface of the body of
through a heated .
'
containing the inhibitor‘up
dibutyl citrate and condensing the vapors.
'
body of high-boiling solvent for said inhibitor to 20 7. A method of removing a normally solid’poly
dissolve substantially all or the inhibitor there
merization inhibitor from butadiene which com
from, leading off the vapors of the puri?ed
prises bubbling the butadiene containing the in
fromthe
surface
of
the
monomeric substance
hibitor up through a body of liquid dibutyl phthal
body of liquid and condensing the vapors. .
ate to remove substantially all of the inhibitor
3. A method of removing a normally solid poly 25 from the butadiene, leading oi! the vapors of
merization inhibitor from a normally gaseous
the puri?ed butadiene from the surface of the
monomeric substance which comprises bubbling
body of dibutyl phthalate and condensing the
the monomer containing the inhibitor'up through ‘
vapors.
“
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a body of high-boiling solvent for said inhibitor
8. A method of removing a normally solid poly
to dissolve substantially all the inhibitor there 30 merization inhibitor from butadiene which com
from, leading 01! the. vapors of the puri?ed
prises bubbling the butadiene containing the in
monomeric substance from the surface of they
hibitor up through a body of liquid tricresyl phos
body of liquid and condensing the vapors.
~
4. A method-of removing a normally solid poly
merization inhibitor from butadienewhich com
prises bubbling‘ the butadiene containing the in
hibitor up through a body of high-boiling sol- '.
vent for said inhibitor to dissolve substantially all
of the inhibitor out of the butadien , leading oi!
phate to remove subs _ tially all of the inhibitor
from the butadiene, leading off the vapors of the
puri?ed butadiene from the surface of the body '
oi’ tricresyl phosphate and condensing the vapors.
ALBERT J. GRACIA.
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