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Патент USA US2409916

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Patented Oct. 22, 1946
Byron M. Vanderbilt, Cranfor‘d, and Ralph'F. '
Plowe, Elizabeth, N. J ., assignor's, -by mesne‘ as‘
signments, to Jasco, Incorporated, a corpora-i‘
tion of Louisiana
‘No Drawing. 7 Application 'November'30, 1940,
~‘Serial No. 368,106
1 Claim.
(Cl. 260-—-84.5) -
This invention relates to the polymerization of
I as buta'diene-in admixture with one or more of
ole?nic substances into plastic, elastic substances;
relates particularly to the polymerization of bu
tadiene containing mixtures in emulsion form at
moderately elevated temperatures; and relates
the other substances, in ‘which mixture the buta
diene maybe present in the‘ratio of from 30% to
the 100% of totalreactants. The butadiene, or
butadiene mixture, ‘emulsi?ed in water in the
proportion of 100 parts of butadiene‘ material or
mixture with from 100'parts to 500 parts of water.
The mixture preferably contains an emulsifying
especially to methods for speeding up the poly
merization reaction and improving the character
of the polymer obtained by the emulsion poly
'merization of diole?n containing mixtures.
agent such as sodium oleate or sodium stearate
It has been found that when butadiene and 10 or sodium palmitate or other soap, or other suit—
able emulsifying agents such as the salts of sul
similar substances are emulsi?ed in water, either
singly or in admixture with certain other unsat
fated long carbon chain amides and alcohols,
urated substances, at ordinary or elevated tem
alkylated naphthalene sulfonates, and other suit
peratures, and maintained in emulsion form for
“ able emulsifying materials. The emulsifier may
a prolonged period of time, a polymerization re 15 be present in the proportion of from 0.5 part to
action occurs to produce materials having many
20 parts per 100 parts of ole?m'c material. There
of the properties of natural rubber, but as usually
is preferably also added a, substantial amount?of
carried out, the products are of inferiorquality
a peroxide catalyst such as hydrogen peroxide,
if the reaction mixture is heated to a sufficient
benzoyl peroxide, ammonium persulfate, or other
temperature to get relatively complete ‘reaction
soluble organic or inorganic‘peroxide material
which is desirably present in the proportion of
Within a few 'hours and if the reaction is carried
out at a su?iciently low temperature in order to
‘ from 0.05 part to 3 parts per‘ 100 parts of ole?nic
get ‘a “product of high quality, the reaction time
mixture. ' The pH of the mixture is then adjusted
becomes a matter of even days or weeks and the
process is economically unfeasible.
‘ 25
The present invention provides a combination
of steps by which the polymerization reaction is
greatly speeded up, and at the increased reaction
speed a polymerizate is obtained which has a high
by the addition ofsmall quantities of certain
acidic'or basic materials'until it is ‘set at a‘ value
lying between 8 and 8.8. This mixture is con
veniently charged into a ‘metallic vessel with
means for efficient mixing of the, mixture in
order to maintain the ole?nic material in an
tensile strength, and satisfactory plastic and‘ 30._ emulsion form and to facilitate removal of‘ the
elastic properties.
“According to the present invention,1the pro
a heat of‘ reaction.
The temperature may be held
within the range of 20 to 30°.‘ C. for from 1 to 8
withinthe range of 25 to 403‘0. for a fur
of butadiene, with, or without‘auxiliary ole?nic
.polymerizable substances such as acrylonitrile 35 ther period of from 2 to 10 hours, andand a tem
' perature ranging from 30°-to‘50° C. for a further
_ and the like, in water, with an emulsifying’ agent,
period of from 4 to 12 hours. At the end of this
, preferably of the soap, type, and a catalyst of'jthe
interval the reaction vessel may be opened, any
‘peroxide type presentin optimum concentration;
, cedure consists in thepreparation of an emulsion
in which the hydrogen ion concentration ortpH
unreacted ,butadiene ,volatilized out, and the
,is accurately controlled to .a desired ‘value, and 40 , emulsion-broken by ‘the addition of suitable pre
_,the polymerization procedure is conducted ac
cipitants such as an acid‘ or water~soluble salts
:cOrding to a‘predetermined temperature‘ sched
i or both.
‘ule; by which the initial polymerization reaction
an object of the invention is to speed up
“occurs: at a relatively low temperature, and the
the polymerization reaction of ole?nic materials
, ‘final ‘polymerization reaction occurs at a substan
and obtain preferred characteristics in the poly
tiallyhigher temperature and high speed.
‘According to'the invention, thepolymeriz‘able
materials‘; are preferably selected from such sub
stances as butadiene or mixtures of butadiene
mer or interpolymer by the addition of the ole
?nic material to water containing an emulsifying
agent‘while stirring; the addition of a suitable
with such. substances as acrylonitrile, styrene, 50 catalyst and conduct of the polymerization‘ reac
tion under conditions of accurately adjusted hy
; vinyl naphthalene, unsaturated esters’, unsatu
drogen ion concentration and. the application of
rated ketones, ‘and similar polymerizable sub
a, greater? rising temperature schedule. Other
stances. These materials form the polymeriza
objects and details of the invention ‘will be ap
nble reactive component of the polymerization
‘mixture, and may be used as butadicne alone,v or‘ 55. parent from the following description.
Example .1
pounded according to the formula shown in Ex
ample l and then vulcanized, showed a tensile
strength of 3100 lbs/sq. in. and an elongation
A mixture was prepared consisting of 420 parts
of water containing 2.5% of sodium oleate by
at break of 450%.
weight andp??bapartsl-of acrylonitrilewwith good 5
Example 5
mixing. This mixture ‘was transferred to, a me
An emulsion was prepared as in Example 1,
tallic pressure vessel which was properly sealed,
and 160 parts by weight of butadiene were forced _ e ‘and, without heating, it was stirred vigorously
in by the application of nitrogenunder pressure.
to"maintainnthe?emulsion for a time interval of
Thereafter 10 parts by weight ‘of v27%»hydrpgen;10.7; =§6,_1/z~hours‘ during which the temperature was
' maintained within the range of from 15° C. to
peroxide were also forced into the bomb andthen
the bomb was sealed. The bombwasjthenhheatedh M18940.“ :At the close of this time interval, the re
.actionvessel-was opened and the butadiene was
to a temperature of 60° Csunderaconditions;of _
vigorous mechanical agitation?to maintain‘, the
wallowed tovolatilize out and was recovered. No
olefin materials in the emulsion condition, and 15 solid polymer was found in the mixture, and sub
the heating and agitation were; continued .ior ,a
Lustantially.allrof the butadiene and acrylonitrile
period of 3 hours. At the end of this timegthe ' :gwere; recovered unchanged.
unreacted butadiene was allowed to volatilize out I
This example shows the extremely slow reac
of the mixture, the residual emulsionx~was~i~re
tion rate, or lack of polymerization, at room tem
moved from the bomb and the polymerizate pre- 20 perature.
cipitatedby the applicationthereto of 2.5 volumes
' Example 6
of saturated sodium .chloridesolution. 1 imparts
- byweight oil-polymer were iobtained,v this being
1An .emulsion -was prepared‘ asrinrExample, 1
and heated according to a temperature schedule
51%‘ oflthe original reactants added to, the mix
ture, and being a.51%». yield: ofthe theoretical (.25 inwhich- the temperature was held at 25°, C.
for a time interval of. 4. hours; 30?, CLfora further
maximum yield.
time interval of: 8,hours;,_ andj40° C._ fora still
This material was washédqdried- and com
pounded on a rubber mill according to the follow
further timeinterval of 9;hours. Otherwise, the
composition of the reaction. mixture and the ex
ing- formula: ' '
\ Partsu 30 perimental conditions-were exactly as those for
the. above examples. The polymer was separated
'Polymer ______________________________ __ 10
as in Example 1 and was found to -be175 % of the
a Wood rosin ____________________________ __
. 4'v
theoretical maximum. It wasthereafter com
'Coal tar _______________________________ __
pounded according to the formula shownvinrE‘x
_, Sulfur _______________________________ __
' Stearic --acid _____________ __, ___________ __
L 11535 amplev 1 and vulcanized in ,the» 'samegmanner.
After vulcanization it had a- tensile .strength of
Ozokerite-wax _________________ _'_ ______ __
4500 ‘lbs/sq. in. and an elongation atybreak; of
Zinc oxide ____________________________ __
Carbon black _________________________ __ '45
Altax (benzo-mercaptoethiazole) ______ ___ v1.25
Diphenylguanidine' ____________________ __ 0.25-40
- "This ~material= ;wasi yulcarrizedin. a \mold at
a; temperature :of 145°,» Cwf-ora time intervalof
' The above examples shown the marked advan
tage of atime and temperature schedule in which
the temperature starts at a relatively lowrvalue
and islraised gradually during the polymerization
reaction. to yieldv a product of highsquality in'a
45 -minutes and» after being removed from the v ' relatively short time.
mold and cooled showed atensile strength of 31.00 . 45
Example 7
lbs. / sqr in.~ with, a.450%l elongation, at. break.
"Example 2
' This ,experimentwas conducted‘in‘ a pressure
.vessel or bomb equipped with a turbine mixer, by
A. similar mixtureof materials-was‘ prepared
as shown in Example _1,' and the emulsion wasm?o which suf?ciently rapid agitation could be ob
tained to bring the ole?nic materials into a-good
I heated at a/ temperature of 60°’ C.-'for 4 hours
emulsion. 2600v parts by weightgof- water were
(one hour longer ‘than‘Example 1). “The result
v placed in the reactor, together with‘65 parts by
ing polymer amounted to 60% of‘ the original re
actants, lwhich upon curing . according .to: the
~ abovev formula. yieldedlmaterialrhaving a tensile ,.
pweight of a _water, soluble soap, speci?cally
sodium_ oleate and 16 parts ,by weight of‘ 27%
(hydrogenperoxide. ' The pressure vessel wasrthen
closed and the stirrer started in-yigorous rota
tion. Thereafter a'mixture consisting (of 325
'tion at break.
._parts by. weight of 'acrylonitrile and 975pparts
Another run .usinga similar mixture polymer-,
by weight ,of butadiene was forced into the pres
ized at 60° C. fora time interval of 5 hoursgave 6Q surevessel by thenapplication of nitrogen pres
sure to thejole?nicrmixture in a suitable, con
a yield amounting to 81% of the reactants, and
tainer. 'jThepressure vessel was'?llednearly ‘full,
_ the polymer when compounded according “to ‘the
.to minimize the, amount of vaporized ‘butadiene,
“above formula and, cured had‘ a tensile strength
of " 2400 lbs.>/s'q.'_in. and- an- elongation at break,‘6 5 and when the emulsion was well formed; the tern
perature was raised to 25° C. and held'theregfor
.a time interval of 2 hours. Thereafter Ithe tem
IA similar ole?nic ~mixture~iwas? prepared - as in
~1Example> 1;»1and1';the;lmixt,ure - was-heated - with
=vigprousI stirring; to", maintain -:the- emulsion, Y. to ‘ 70
;-40"_ C._", fora time interval 014%:v hoursand then
, thestemperature. .was raised to»50° .
at vwhich _
it was maintainedien? hours- ..The yield. .0? p'o1y— '
mer was ‘581%...ofdthe ,theoretical,.maximurn;,_and .
,perature was vraised .to 30° C. for a further’ period
of.6 hours and further raised to 40° C. for-a
further period, of 3 hours, making a totalpoly
merizationtime of 716, hours. At the; end of‘ this
time interval, the pressure vessel was opened and
‘the unreacted butadiene allowed» to distill' off.
1' The residual latex was then withdrawn to a larger
“container, andthe polymerw'as-precipitated-iby ‘
the polymer upon being precipitated and com-”'75 the addition of approximately I vo1ume~0f~~salt
, 2,409,915
solution. A yield of‘1092‘parts by weight of dry
canized in the manner above shown and was then
found to have a tensile strength of 4420 lbs/sq.
in. and an elongation of approximately 550% at
polymer was ‘obtained, being approximately 84%
yield of the theoretical maximum. This material
was compounded according to the formula shown
in Example 1 and vulcanized as in Example 1.
After vulcanization, it‘was found to have a tensile
strength of 4500 1bs./ and an elongation at
Example 10
break of 500%.
This example still further shows the advan
tages to be derived from a gradually increasing 10
temperature of polymerization according to the
indicated schedule.
' _, A mixture of the following composition was
prepared in a pressure vessel of the turbine mixer
V .
Parts by weight
Igepon ‘T (sulfated
long‘ carbon ._ chain
In the above examples, the pH value‘ was ad
justed to approximately‘ 8.4 since it has been
found that the hydrogen ion value is exceedingly. 15 Butadiene _________________________ __l____*_‘ ‘.320
Hydrogen peroxide (27%) ______ __‘___‘___‘__1_; 20
I critical for the obtaining of a rapid reaction and
a high grade polymer. According to the present
invention,_it is found that the polymerization
of ‘diolefins such as butadiene or the interpoly
mixture was ‘heated at a‘ temperature of
50° C. for a time interval. of.2_2 hours‘. At the
close'of that time ‘substantially all .of the buta
merization of diole?nssuch as butadiene with 20 diene and acrylonitrile were recovered unchanged
other unsaturates such as acrylonitrile, styrene,
from the mixture and no polymer was found to
Vinyl naphthalene and the like to form vul
have been formed showing‘that no polymeriza
canizable rubberlike materials occurs at an ex
tion reaction occurred. It may bejnoted that the
tremely slow rate, or does not, occur at all if the
Igepon T is neutral and. the above mixture was
pH value of the polymerization emulsion lies.
25 neutral, having a hydrogen ion value of approx
between about 6.5 and 7.5,in the presence of
polymerization catalysts. If polymerization is
‘ Example 11
obtained at all in this pH range, the rate of re
action is slow and the polymers obtained are in
A similar mixture to ‘that of Example 10 was
ferior in nature. At elevated temperatures, 30 prepared and 2 parts by‘ weight of normal sodium
such emulsions containing butadiene alone, or
hydroxideisolution was .added. This mixture Was
,mixtures of butadiene with acrylonitrile, styrene,
heated at a temperature of 50° C. for 22 hours.
vinyl naphthalene and similar substances poly
merize either extremely slowly or not at all at
pH values between about 7.0 to 7.7.
At the close of this interval, 80% of the reactants
were found to have polymerized to a high-grade,
In the pH ‘ ‘
rubber-like polymer.
range of from 7.7 to 8.1 polymerization occurs
' at fairly rapid rate but the emulsions or latices
formed are unstable and tend to precipitate in
A similar mixture to that of ‘Example 10 was
the reactor. The preferable pH range lies be
tween the values of about 8.1 to about 8.8. With-,
in this range polymerization occurs rapidly to
form elastic polymers in good yield of high ten
sile strength and high elongation. The best re
sults are obtained at pH value of approximately
Example 12
prepared except that 2 parts by weight of nor
mal acetic acid solution Was added to the mix
ture. The emulsion was then heated to a tem
perature of 50° C. for 22 hours. At the end of this
time the reaction was 90% complete, but a rela
tively large amount of the product‘was ‘found as
As the alkalinity is raised about about 8.8,‘ r a dense coherent precipitate in the reaction
the reaction becomes progressively slower with
increasing hydroxyl concentration. The emul
Example 13 ‘
sions formed are stable but the products ob
A mixture was prepared in a pressure vessel
tained are of lower quality as compared to those
equipped with a turbine stirrer as in Example
10, consisting of the following materials:
obtained atthe preferred hydrogen ion value.
Example 8
An emulsion'of butadiene and acrylonitrile was
prepared as in Example 7 and the pH value was
Water _____ __‘_'___'_ ____ _;.___; __________ __
Dodecyl amine
raised to 9.6 by the addition of small quantities ‘ '
0.94 normal acetic acid; _______________ __‘
56. 3
of‘ sodium hydroxide solution. The emulsion was
then heated in the pressure vessel to'a tempera
Ammonium .persulf'ate __________________ __ 0. 2
ture of 25° C. for a time interval of 4 hours, then
to 30° C. for a further time interval of 8 hours,
This mixture had an initial pH value of 7.0.
then to 40° C. for a ‘still further time interval of 8‘ 60 It was heated according to the schedule of Ex
hours and then to 50° C. for an additional time
ample 8 with e?icient stirringwto maintain the
interval of 1 hour. The ‘reaction was 78%
emulsion.‘ ‘At the end of the 21 hours, the buta
complete after 21 hours and the polymer after
diene was distilled out and 155 parts of the orig
compounding and vulcanizing had a!‘ tensile, ' 1 inal 160 parts were recovered. Only a little dark
strength of 4300 lbs/sq. in.
Example 9
An emulsion was prepared as ‘in Example 7
and the pH value was adjusted to 8.45. There
‘after the mixture was heated according ‘to the‘
‘time schedule set out in Example 8. At the end
of the 21 hours'rea‘ction time, the polymer was
‘separated and the reaction ‘found to bej93%
brown oil was formed as a polymerizate.
. Example 14
' A mixture similar ‘to' that of Example 13 was
prepared but‘with 36 parts by weight of the acetic
acid solution; thereby adjusting the pH to a‘value
‘of 6.2. A 62% yield of ‘good polymer‘ was ob
tained ‘after heating identically as was Example
13, which after washing, compounding, and vul
canizing as in Example 1,‘was found to‘have- a
according to the formula given'in Example 1, vul 75 ‘tensile strength of 3900'pounds per sq. in.
complete." The polymer was washed, compounded
.1; 2,409,915
' 8
i catalyst. content :increaseslthe reaction rate ; . and
*Example 15
‘, thisais particularly so with-substantiallyall- other
: .ole?nic polymerization'reactions.
iAimixtureofgll'??parts by weight of water con
taining 8 par-ts of sodium lauryl sulfate waswell
agitated While adding-.5Qparts of styrene. Four
Example‘ )1 6
3A: mixture was prepared‘in-the pressure-reactor
parts of trisodium phosphate was then added and "
i asrin‘ Example 13 according-to the following for
“theremulsionswasifoundlto have a pl-lrofvlll.
'"I'Then mixture was placed in a pressure vessel. and
then 150 parts of butadiene containing 1 partlof
:benzoyl peroxide was added under pressure whilel 10 Water ______________________________ _'____ 380
w-mixingr ~The reactionmixturewas thenrheated
' Dodecyl amine _________________________ __ - 7.4
to 50° 1C. fora period of 17-h0urs. It Was-found
0-943 normal acetic acid ___________ __V_____ 40.8
hthat 35% - of the- total weight ofi-the-styrene and
butadiene had been converted, ‘to a rubber-‘like
~ ?cl‘ylon‘ltr-ile _________ a. ___________ __..'...__ 56.3
-~:AmmOnl11m fpersulfate _________ __-_ ______ __ 0.8
, 15 Butadiene _____________________ _; _____ _;_ v160
‘ This preparation Was 'repeated:~and modi?ed‘
’ inthatsodium bicarbonate was ,used as buifer to
“This‘ mixture .was heated, for; a,time interval
0f121. hours. according to the temperature sched
, givean initial pH of 8.5. Afterthe 17 .hour reac
ule shown in Example 8. Atthe end of'this reac
tion period at 50° .C. .-a. :concen-tratedlatex was
‘formed. which, i on coagulation .with. isopropyl. al-_ 2.0 tion'time. the unreacted butadiene wasldistilled
,01T,...the polymer. precipitated ,as before,_and the
. .cohol, gave. 152 parts of polymer: of . high tensile
strength, a '76 %‘ yield.
yield was found. to .be 61% of the theoretical
maximum. However, a considerable portion. of
the polymer was found to have precipitated in the
reac'torand the productwas discolored and gen
It. has been.v found that not .onlyare. the .hy
. drogen,v ion and temperature schedules of very
, great importance, butit. has alsobeenjoundthat 25
erallyunsatisfactory. After washing, compound
the catalyst concentration likewise, is .ofegreat
ing, andcuring asin'Example .1, it ‘was found ,to
have relatively low tensile strength andlow elon
importance in order to get polymers of high qual
ity in relatively short reaction periods. It is also
found that the peroxide. catalyst such‘ was-hydro
.agen peroxidei vbenzoyl peroxide, ammonium per
vlt'aramrde 17
.i sulfate or .the-like should be'present in an amount
A‘ similar_mixture to that in Example 16 ‘was
of. 0.105 to, 0.3% of ‘.the aqueous-phase. Athigher
prepared with only 0.2 part by weight of ammo
values than. 0.3%~ the resulting polymer ‘is: of
nium persulfate. This mixture'wasstir‘red and
lowerrtensile. strength‘ and has inferior-plastic
to react through the same time schedule
properties and the rate of reaction ismarkedly 35 allowed
as in Examples 8 and 16. At the end of the reac
decreased. On the other hand, if the initial con
tion period the unreacted butadiene was?distilled
centration of the catalyst isless than about 0.05%
off, the polymer precipitated and found to consist
in the aqueous phase, the reaction proceeds less
of approximately 80% of the original ‘reactants.
irapidlytandrwhen the catalyst concentration is
" This emulsion was'recovered from the reaction
as‘low‘ as 0.01% of ,the water-phase; the reaction 40 chamber as a latex of good color'which after pre
rate is approximately that obtained when no cat
cipitation, washing, compounding, and vulcaniz
alyst is present.
v'I'hefollowing table shows the, effect of "change
in concentration of hydrogen peroxide catalyst in
ing as in Example ‘1, was, found to have a good
tensile strength and satisfactoryelongation and
plastic properties.
. the water‘ phase when copolymerizing a mixture ?45 “The above examples utilize mainly mixtures of
of 25% of acrylonitrile and 75% butadi'ene in
emulsion at a pH of 8.4:
butadiene and acrylonitrile, but the same factors
and values apply to mixtures‘ containing ‘only
'butadiene as the reactant and to mixtures con
‘Percent'converted ‘
ketone and ‘similar unsaturates.
81 "
‘ 8-?5
- g?
‘89 ~
Likewise, while
only hydrogen peroxide-and ammonium persul
20 hrs; 21 hrs, 22 hrs_
talining'both Pufmdiene and. styrenegvinyl methyl
‘apply for 'the'other peroxidecatalysts; such as
55 sodium‘ perborate. 'Modifying agentssuch as or
ganic= sulfur'v compounds may» al'sorbe‘ addedv ‘in
order‘ .tmmodify the polymerization process in
~~~~~~ ~~ *Too‘sticggdtglfgempwnd
order to obtain more plastic products. “Similarly,
' '
' while a fewrepresentative temperatureschedules
' .i' It will be observedvfrom this table that'gtheopti
_ :mum'concentration ‘of catalyst lies :in the, :range
..o,f;about 0.05%»to0.1%.
thesame requirements: and similar molar values
94- ______
fate and benzoyl peroxide, are shown as catalysts,
aregiveng'it'will- be appreciated by‘those skilled
in‘ 'thezarti’thatidiilerent unsaturates require dif
ferent temperatures‘ for polymerization and the
"invention comprises the use of‘ anytemperature
It may ‘be. noted that -the:;.cata1yst(proportion
in this mixture, showsan optimum valueat which
~ schedule in which a progressively increasingtem
a. maximum rate of_ polymerization occurs.
course of the polymerization reaction.
It should be understood that the materials em
‘ployedin' the various examples cited above were
phenomenon is entirelycontrary to most poly
-.~ merization reactions. {In the presentrinstance, as
the catalyst;concentration is-increased from 2 or
_ 3 hundredths of ~l,%.up to approximately/0.075%,
the; reactionrrate increases Wi-thincrease in-Icon- '
.scentration; when; how_ever,-~v the;catalyst concen
._rtr_ation1isiincreaseduabove about 0.1%.»thereac
.tion 1 rate decreases. .This-isin, contrast atolmost
catalytic , processes; ; in- : which‘: an ; increase _:in the
perature is used at progressivelyilater‘timestin‘the
. of=-c0mmercial jgrade.
By ‘using diole?ns ~ and
other cop'olymerizingematerialsxof very high pu
rity, the reaction periodimay‘bev greatlyidecreased.
Forfexample; when highly purified butadiene and
acrylonitrile 'were ,:used ‘.in the processes“ as de
~ scribed above; :the copolymerization ‘reaction-was
175. <’75;%r complete‘, afterionlyi'l-hours and the‘: rubber
like material obtained was of excellent quality.
It should be appreciated that di?‘erent diole?ns,
singly and with other ole?nic materials capable
0f colwlymerizing in emulsion form, vary in their
activity at a given temperature. Vinyl naph
merization process is accomplished in a relatively
short time.
While there are above disclosed but a limited
number of embodiments of the invention, it is
possible to produce still other embodiments with
out departing from the inventive concept herein
disclosed, and it is therefore desired that only
such limitations be imposed upon the appended
thalene is less reactive with butadiene than is
styrene and a higher initial temperature is re
quired. Also acrylonitrile is more reactive with
butadiene than is styrene and mixtures of acryl
claim as are stated therein or required by the
onitrile and butadiene containing 40% acrylo 10 prior art.
nitrile are more reactive than those containing
The invention claimed is:
15% of the nitrile. Thus the optimum tempera
In an emulsion polymerization process for the
ture range employed will vary with the reactants
polymerization of a mixture of butadiene and
employed, but temperatures above about 60° C.
acrylonitrile in the ratio of about three parts by
and below about 25° C. are undesirable, regard 15 weight of butadiene for each part by weight of
less what ole?nic reactants are employed.
acrylonitrile, the steps in combination of mixing
Although we prefer to use our stepwise temper
the mixture of butadiene and acrylonitrile with
ature control, We also may use a constant reac
Water in the presence of an emulsifying agent
tion temperature. When using a constant reac
comprising a water soluble soap and a peroxide
tion temperature of about 40° C. at a pH of 8.4,
polymerization catalyst, agitating the material
a faster reaction and a superior polymerizate is
to maintain the mixture in emulsion in the water,
obtained as compared to those obtained at a like
setting the temperature of the mixture at ap
temperature outside of the 8.1-8.8 pH range.
proximately 25° C., holding the temperature at
Thus, the invention consists of an emulsion
approximately 25° C. for a time interval of ap
polymerization reaction of ole?nic materials to . proximately four hours, then raising the tem
produce rubber-like polymers in which the emul
perature to approximately 30° C. for a further
sion is maintained by a suitable emulsifying
time interval of approximately eight hours, then
agent, the polymerization reaction is promoted
raising the temperature to approximately 40° C.
by a catalyst in concentration of 0.02 to 0.3% in
for a further time interval, maintaining the pH
the water phase, ‘the pH value is maintained be 30 value of the material within the range between
tween about 8.1 and 8.8, a gradually rising tem
8.1 and 8.8 during the entire polymerization re
perature schedule for the polymerization time is
action, cooling the material at the encl of the
used to produce a very high grade polymer having
polymerization, and separating the polymer from
high tensile strength, high elongation, and other
unpolymerized ole?nic material.
desirable physical characteristics and the poly- ~'
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