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Patented Nov. 5, 1946
2,410,408 '
PATENT orric'
John R. Durland, Nitro, w. V8", assignor to Mon
santo Chemical Company, St. Louis, Mo., a cor
poration of Delaware
No Dra. Application March 1, 1944,
Serial No. 524,637
8 Claims. (Cl. 260-6685)
The present invention relates to the stabiliza
tion of vinyl compounds and to the stabilized
compounds have been found to possess mar
inhibiting action when incorporated into mono
compositions so produced.
meric styrene. It is to be understood that the
- It is well known that vinyl ‘compounds as for
above are merely illustrative of the invention and
example vinyl esters, and vinyl aromatic com Cl other phenolic sul?des can be usedwhere con
pounds such as styrene, its homologues and
venient or desirable. ,
analogues tend to polymerize on standing. In
The phenolic sul?des do not discolorvinyl com
the manufacture of vinyl polymers premature
pounds and are therefore eminently suitable for
polymerization even to a very slight extent may
incorporating into the compositions prior to stor
render the monomer un?t for use since it may
age. In addition, they are e?ective at elevated
seriously a?ect the properties of the ?nally polyf
merized product. For this and other reasons it
temperatures as for example 100° (It-200° C. as
well as at storage temperatures and effectively
is essential to prevent premature polymerization
prevent polymerization during distillation. They
and for this purpose it is common practice to add
are easily removed during distillation of the vinyl
compound and in noway a?ect the polymeriza
tion of the distilled products. The amount oi’ in
hibitor to be used will of course vary according
to the particular composition and conditions un
an inhibiting agent to the liquid monomer. An
object'of this invention is to provide a new and
improved class of inhibiting agents.
A further object of the invention is to provide
a class of cheap materials' which are effective _ der which it is to be used'but in general propor
inhibiting agents. A still further ‘object is to 20 tions within the range of 0.001 to 5% are satis
provide a class of inhibiting agents which are
easily removable from the liquid monomer after
which the polymerization reaction can be carried
out in a normal manner. Other and further ob
jects will be apparent from the description fol
In accordance with this invention it has been
found that phenolic sul?des e?ectively inhibit the
polymerization of vinyl compounds during stor- ~
Often the merest traces are sumcient
to prevent polymerization entirely.
_ .
Among vinyl monomers which can be preserved
by incorporating therein a phenolic sul?de are
. vinyl acetate, divinyl benzene, ¢~methyl styrene,
p-methyl styrene, ethyl vinyl benzene, vinyl
naphthalene, p-chloro styrene and the like.
Asspeci?c examples of the invention which il
lustrate the inhibiting power of phenolic sul?des
age, shipment and distillation. The monosul?des 30 but which are not to be taken as limitative of the
are the most effective and are therefore preferred
invention, 0.250 part by weight of inhibitor was
but higher sul?des as for example disul?des and
polysul?des of phenols can be used with good rile-l"
suits. One or more hydroxy groups may be pres
charged with 25 parts by weight of freshly dis
, tilled styrene into screw cap bottles of suitable
capacity having the caps lined with tin foil. The
samples were then immersed in a boiling water
stituents such as alkoxy, alkyl and halogen
‘bath for a total of 20 hours. Viscosity tests were
groups. In general, the phenolic sul?des possess
then made at25° C. with a 10 ml. analytical
the type formula
= pipette measuring the time of ?ow from the up—
per mark to a lower mark just below the bulb.
where :c and n are integers or polymers or this 40 For monomeric styrene the time of ?ow was 11.5
seconds. The viscosities in the table below are
expressed as relative values with monomeric
ent in the aromatic nucleus as well as other sub
Typical examples of phenolic sul?des which
can be used in the practice of this invention com
styrene as one. As afurther measure of the in
I hibiting action the polystyrene content was deter
45 mined by distillation.
prise the following: di-(o-benzyl phenol) mono
sul?de; di~(p. t-butyl catechol) monosul?de; di
carvacrol monosul?de; di-catechol disul?de; dl~
catechol monosulilde: di-m-cresol monosul?de;
may] catechol) mono'sul?de--.“ 1
dl-o-cresol monosul?de; di(di-t-butyl catechol) 50 Dl-(p.
Dl-catechol monosul?de.._ _
monosul?de; di-?-hydroxy naphthyl disul?dc;
(ii-phenol monosulflde; di-thymol monosuliide:
percent '
0. so
1. 02
0. 45
l. 02
l. 10
0. 85
O. 50
Di-thymol monosulilde ................ . -
l. 03
0. 00
Di-m-cresol monosul?dc____
Dl-o-cresol' monosul?de.__
monosul?de of catechol monobenzyl ether; di
Monosuliide cl cstechol monobenzyl
ether .......... -. .............. ..‘ .... _.
hydroquinone disul?de and di(2-methyl, 4 t
butyl) phenol disul?de. All of the foregoing 65
By way of comparison styrene without an in
Other polymerizable vinyl compounds can be
hibitor was too viscous for test after heating for
stabilized with the new inhibitors and other
the same length or time.
phenolic sul?des used. The method of adding
Storage tests were carried out employing
the inhibitor can be varied widely. This inven
phenolic sul?des as storage inhibitors. Freshly 5 tion is limited solely by'the claims attached here
distilled styrene was stored in the dark at ap
to as part of the present speci?cation.
proximately 25" C. in contact with 24 gauge sheet
What is claimed is:
steel. 0.01% oi’ inhibitor was incorporated into ’
1. A liquid composition comprising a styrene
the styrene and samples tested periodically for
monomer and a proportion of a monosul?de of a.
increase in viscosity. The condition _ of the i0 dihydric phenol su?icient'to inhibit polymeriza
styrene showed no change after many months
storage. The results are summarized below:
2.'A liquid composition comprising a styrene
monomer and a proportion of a monosul?de of a
monohydrocarbon substituted dihydric phenol
.5 ‘suiiicient
to inhibit polymerization.
‘ _3. A liquid composition comprising styrene
monomer and a proportion of a, di-(p-tert. butyl
None........................ -- swam.-." Visoousliquid.
catechol) monosulilde sufficient to inhibit poly-- ‘
Di-g?tsbutylcatechol) mono- wmonths ._ Noapparentchange.
Di-mcesol monosuliide ..... .. 10 months -Di-o-cresolmonoslniide ...... .- 10 mon
Di-thymol mouosul?de ...... __ lilmonths---
"Dig-Iggy] m-cresol
10 mon
Di-carva'crol monosul?de ____ _. 10 months--.
4. A liquid composition comprising styrene
monomer and a proportion 01’ di-catechol mono- '
sul?de su?lcient to inhibit polymerization.
5. The method of preventing polymerization of
a styrene monomer which comprises incorporat
It was iurther noted that the addition-oi the 25 ing therein a, proportion of a monosulilde of a
inhibitor caused no discoloration and after ten
months storage the styrene compositions contain- >
diihydric phenol su?icient to inhibit polymeriza
t on.
ing the inhibitor were still perfectly colorless
6. The method of preventing polymerization of
watery liquids. These results show that very
a styrene monomer which comprises incorporat
small proportions oi phenolic sul?des effectively 80 ing therein a proportion of a monosul?de of a
preserve-styrene during storage. In this connec
monohydrocarbon substituted dihydric phenol
tion, mention should be made of the fact that
vsu?icient to inhibit polymerization.
the inhibitors may be employed in proportion
'I.‘ The method of preventing polymerization of
su?icient to stabilize the vinyl compound at room
styrene monomer which comprises incorporating
temperature, or thereabout, but in proportion in- 35 - therein a proportion 01' di-(p-tert. butyl catechol)
suilicient to stabilize the composition at elevated
monosulfide su?icient to inhibit polymerization.
temperature in which case the stabilizing agent
8. The method of preventing polymerization of
need not be removed. The composition may when
styrene monomer which comprises incorporating
desired be heated to produce polymeric products
therein a proportion of di-catecho'l monosul?de
without removal of the stabilizing agent.’
40 su?icient to inhibit polymerization.
Again, the invention is not limited to the com
positions set] forth to illustrate the invention.
JOHN R. em.
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