Note: Descriptions are shown in the official language in which they were submitted.
i9~3
~ACKG~OUND OF THE INVENTION
Ma~s or bulk polymerlzation o~ vinyl ~hloride mono-
mers to provide polyvlnyl chloride or vinyl chloride copolymers
is now commercial. Such poly~erizations are conducted in the
~bsence of any di~solving ~olvents in whlch either the vinyl
chloride and/or vinyl chloride pol,~mer ls soluble, or ~uspend- ~ing agents such as water, alcohol and the llke. Such polymeri- :
z~tions are in~tlated and carried ~orward by the u~e of free
radical formers 8uch as organic peroxy ~nitiator~. It i5 o~ten -~de~ired or nece~sary to control or stop such polymerization
reactions within a relatively short time.
Under one set o~ c~ndition~, one may wi~h to stop
the polymerization rapidly because of desired phy~ical proper-
ties o~ polymers obtained at a given percent of conver~ion,
less t~an complete conversion. Uhder other conditions, it is
de~irable, even though sub~tantial conversion of monomer to '
polymer is obtained, to co~pletely destroy the cat~ly~t. Of
more importance, however, is a safety ~actor. In mass or bulk
pol~meri~ation Or vinyl chloride monomers the reactlons ma~
run out o~ control for a variety of reasons and emeræency
shortstop condltlons are n~ces~ary due to the large volume o~
material belng polymerized. Such conditions may aris~ as a
consequence o~ fallure o~ pump~ or other equipme~t providln~ -
coollng means to the reactors, charging exces~ive ~mounts o~
catalyst to the reactor either becau~e of equlpment ~ailure
monltoring the equipm~nt, breakdown or operator error æ~d the
llke~
Whlle nitr~c oxlde has been propos~d as a ~hortstop
~or certain aqueous su9penslon polymerizations of but~diene
3o polymers and the like, it has not been u~ed com~ercially ~or
many reasons. In studie~ related to mas$ or bulk polymeriza-
tion of ~inyl chloride monomer~ the critic~l perlod ~here it
-2- ~k
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is most difficult to stop the polymerization reaction 1~ after
about 25% conversion o~ monomer to polymer has occurred, at
which time there is in the reactor a substantial solid wet
mass of material as opposed to a solution or su~pension o~
vinyl chloride polymer in vinyl ch:Loride monomer. To date,
none of the conventional shortstops for vinyl chloride poly~
merization have been found to be e~ective as a~ emergency
shortstop in mass polymerization systems under out-of-control
conditions.
SUMMARX OF THE INVENTION
r ~. . . _ __ ~ '
It has now been discovered that in the mass polymeri-
zation o~ vinyl chloride monomer~ alone or mixed with other ~
olefinically unsaturated v~nylidene monomers, for example, ;`
that when the con~ersion o~ monomer to polymer has reached
about 30% and the polymerization mass has been converted to a
~et mass with an organo peroxy ~ree radical forming catalyst,
that the polymerization reaction mæy be stopped quickly even
under emergency and out-o~-control situations wlth small amounts
of nitric oxide.
An unexpected advantage o~ the inYention is that an
amount o~ nitric oxide les~ than th~t requtred to react with
all of the initia~or or catalyst may be added so that when
this amount o~ nltric oxide ha~ reacted with ca~alyst ~ree
radicals and the nitrlc oxide is all reacted or used up, the
polymerization will begin ~g~ln and may be continued to com
pletion. The use of nltri~ oxide ha~ another advanta~e in
that one i8 not ~dding solid material~ to the ~inyl chlor~de
polymer that have to be later remo~ed. Also, the rate of
polymerization may be controlled by use o~ small amounts o~
nitric oxide.
D~TAILED DESCRIPTION
The polymers of the pre~ent in~ention are obtained
-3- ;
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1~)59~i~8
by mass polymerization of a vinyl h~lide or vinylidene halide
monomer, or mixtures thereo~, with other olefinically unsat
urated or vinylidene comonomers. The vinyl or vinylidene
hailde monomer~ corre~pond to the ~t;ructural formula
~Y ~.
H2C c\x
wherein X is a halogen ~elected from the group consisting o~
chlorine9 bromine or fluorine and Y i~ hydrogen or a halogen
the æame as de~lned ~or XO An especi~lly u~eful vinyl halide
monomer o~ the above type i8 vinyl ~hloride. The amount of
vinyl chloride mon~ner will range irom about 40~ or more~ pre-
~era~ly about 55%, to 100% by weight of the total monomer
compo~ition.
In addition to the Ylnyl chloride monomer, one or
more other polymerizable olefinically un~aturated, vinylidene ,~
comono~er~ pre~erably containing at lea~t one ter~inal methyl-
ene group (H2C=C ~) may al80 be emplo~ed ~herewith. U~ually
less than about 50~ by welght o~ the~e polymerizable co~ono-
mers i~ pre3ent. Copolymerizable co~onomer~ include dIene~ .
o~ 4 to 10 carbon at~s including such con~u~a~ed diene~ a~
butadiene, isoprene and plperylen~;~ ethylldene norbornene and
dlcyclopentadlene; ~-olefins such as ethylene, propylene, i~o-
butylene, butene-l and 4-methylpentene-1, pre~erably contain-
:ing 1 to 8 carbon atoms, vinyl bromide, ~inyhidene chloride,
vinyl rluoride; vinyl e~ters such as vlnyl acetate, vinyl
laurate and vin~rl chloroacetate, vin~rl aromatics euch as sty- :.rene,~ chlorostyrene? ~methyl 3tyrene, vinrl tolu~ne ~nd ~inyl
naphthalene, alkyl v~ nyl ether~ and ketone~ 3uch ~ ethyl
vinyl ether, lsobutyl vlnyl ether, N-butyl vinyl ether, chloro- -
eth~rl vinyl el;her, methyl Yinyl ketone and ieobutyl vinyl
3o ether; a"B-olefinically un~aturated nitrile~ such as acrylo-
nitrile ~ ~thacrylonitrlle; cyanoalkyl acrylates such as a-
. .
,
-.. ~, ... .. . . ......................... . . .
- . ,
~ 69 ~ ,
cyanomethyl acrylate and the ~ and y-cyanopropyl acryl-
ates; olef~nically unsaturated carboxylic acids as acrylic
acid, methacrylic acid and the l$kle; ester~ of olefinically
unsaturated carboxylic acid~ including ~ ole~inically un-
saturated a¢ids such as methyl acrylate, ethyl acrylate where- .
in the alkyl groups contain 1 to 8 rarbon atoms, chloropropyl
acrylate, methyl methacrylate, et~yl methacrylate, 2~ethyl-
hexyl acrylate, cyclohexyl acrylatls, phenyl æcrylate, glycidyl
acrylate, glycidyl methacrylate, ethoxyethyl acrylate, esters
of maleic and fumaric acid, amideæ of the a,~ olefinically
unsaturated carboxylic acids, and the like; polyfunctional
monomers such as methylene bis-acrylamide, ethylene glycol
dimethacrylate, diethylene glycol diacrylate, di~nyl benzene
and allyl pentaerythritol; bis(~-haloalkyl)alkenyl phosphon-
ates such as bis(~-chloroethyl)~lnyl phQsphonate; ~,~-ole~
finically uns~turated ~-alkylol amides or ~ ole~inlcally
unsaturated N-alkoxyalkyl amide of the formula
0 H
CH2=C-C-X~ ( CH2 )n~Rl
wherein R is hydrogen or an alkyl group containing ~r~m 1 to
4 carbon atoms, Rl i8 hydrogen or an alkyl group:containing .-.
from 1 to 8 carbon atoms and n is an integer from 1 to 4,
~ncluding N-met4ylol acrylamide, ~-~ethylol methacrylamlde;
amide monomer~ derived ~rom an ~ oleMnically un~aturated
carboxylic acid and havln~ th~ 8tructural ~ormula
0 ,R4
C~ =C-C-N R3
R2
wherein R2 i~ hydrogen or an al}url group containing from 1 to
4 carbon atoms and R3 and R4 are hydrogen or a radical con-
t~ning ~rom 1 to 12 carbon atoms and more preferably an alkyl
-5-
~L~596~8
group containing ~rom 1 to 8 carbon atoffl~ ~ncluding acrylamide
and methacrylamide, ~-propyl acrylamid~, diacetone ~crylamlde
and the like. Pre~erably, the copolymers have a softening
point above the temperature o~ polymerlzation.,
In carrying out the polymerization reaction there
is u~ed the u~ual catalyst or initlator~ which normally are
~ree radical forming ineluding organlc peroxide~ and aliphatic ~-
8ZO compounds. Such materials include, ~or exam~le, ~
azodii~obutyronltrile and the like; organic peroxides includ-
ing diacyl peroxides ~uch as acetyl pero~ide in dimethyl
phth~late, benzoyl peroxide, 2,4-dichlorobenzoyl p~roxlde~
lauroyl peroxide, pelargonyl peroxide; p~roxy~st~r~ ~uch as
ester-butyl peroYyacetate, ter-butyl peroxyisobutyrat6, tert-
but~l peroxyisobutyrate, tert-butyl peroxgpivalate, tert-butyl -
pero~y(2-et~yl;hexanoate), alkyl peroxides ~uch a~ ~,a'-bis-
(t-butylperoxy)dl~opropylben~ene~ n-buty~-4,4-bis~tert- :
butylp~ro ~ )vale~ate, di~.tert-~myl pero~lde, dicumyl per~ide,
2,5-dimethyl-2,5-bl~(tert b~tylperoxy)hexyne 3; hydroperoxide~ .
~uch a~ tert-butyl hydroperoxide~ 1,1,3,3-tetrame~hyl butyl
hydroperoxlde, cumene hydroperoxide, 2,5-dlmethylhexan0_2,5
dihydroperoxide, dii~opropylbenzene hydropercxide; ketone per~
oxides such a~ met~yl ethyl ketone peroxides~ sul~onyl acyl
peroxldes 8uch a3 ~cetyl cyclohexyl ~ul~onyl peroxide; ~cetyl
sec-heptylsulfonyl peroxide; peroxy carbonat~s such a~ tert-
butylperoxy i80p~pyl carbonate; peroxy dic&rbonate~ such as
bis(4-t-butylcyclohexyl3pero~y dicarbonate, dicyclohexyl per-
oxydicarbonate, dli~opxopyl perox~dicarbonate; tertiary alkyl
perketals ~uch as 2,2-bi~(tert-butylper~xy3bu~n~; mixtures
thereor and the like. Fou~d use~ul are lauroyl per~xide,
30 di-(2-~thyl hexyl)peroxydlc~rbonate, dl-ethyl peroxydicarbonate~ -
di (n-propyl )pero~rdlcarbonate, dii~opropyl p~roxydicarbonate,
di(sec-butyl)p~roxydicarbonAte and acetyl cycloh~x~ne sul~o~lyl
_6- :~
1~5~69~ '
peroxide.
The nitric oxide preferably iB sub~tantially free
of nltrogen dioxide, i.e., less than about 0,2% and i~ added
to the polymerization reactor and quickly and thoroughly mixed
throughout the polymeri~atlon ma~s, preferably being inserted
at more than one point in the reaction ~ystem. While even a
~ew ppm nitric oxide have an e~ect on the reaction r~te,
amounts ~rom abvut 0.005 to 0.3 weight parts per one weight
part of free radical cataly~t, or fro~ 2 mill~mol to a mol
ratlo o~ about 2 mol~ of nitric oxide per mol of catalyst a~
~n organo pero~y cataly~t will normally be u~ed. Whlle larger
amount~ o~ nitric oxlde may be u~ed, they are not nece~sa~y
and it is pre~erred that no ~cre than about 2 mole o~ nitric
oxide per mol o~ organo-peroxy catalyst be charged. Largar
amounts can be addad in an ~mer~sncy.
The present inve~tion ls u~e~ul in any bulk or mas~
polymerlzation ~stem, ~or ex~mple, in pipe, autoclav~ and the
l~ke. It has been ~ound to be especially use ~ 1 ln ~ystems
where the ~ass polymerizatlon i begun ln one ~t~ge and carried :~
to low conversion generally with high ~g~tatlon, and then
tran~ferred to another stage with lo~er agitation, whsrein
the mas i~ ~onrerted into a subst~ntially dry state ~nd re-
mo~ed ~rom this ~tage in the ~or~ of ~i~yl chloride poly~er
particles. 0~ course, there may be more thAn o~e ~tage.
Example~ o~ ~uch ~ystems are found dascribed ln detail in U.S. ~ i
Patents 3,522~227, 3~562,237 and 3,687,919. . :::
In e~3~ence, the~ ~othg~8 lie in prep~rin~ m~s .-
polymer~ and copolymer~ o~ vinyl chloride ln the ~rm o~ gr~n- .
ule~ or sphere3 b~ polymerlzing the monomer~ in a plurality
Q~ 8tage8, gener~lly sequ~ntla~ly, whlch m ~ be und~r sim~lar
or varying conditlons of pres~ure, temp~r~ture and cataly3i~
In any e~nt, there 1~ a~ lsa~t a ~lrst stage ~h0re the con- ;
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~sg69~ '
version o~ monomers is conducted to about 7 to 12%, pre~erably
with high agitation or agitation of high turbulence, and then ~^
at least one additional stage dur~ng ~lch st~3e the polymeri-
zation is conducted generally in the pre8ence of addit;ional
and o~ten di~srent type~ catalyst and at lower agitation or
absence of high turbulence to complet~on of the reaction. In
3 j562,237 the second stage ls ~ondueted ~n an autoclave pro~ :
vided with a rlbbon blade activator extending hellcally about
its axis of rotation, contiguou8 to the wall8 o~ the autoclave
and radially 5ps,ced ~rom ~aid a~
~ormally, there i~ no necessity ~or ~topping the
polymerization of vinyl chloride in the early stage~ such as
pr~or to 12 to 1~% conver~on of monomers to polymer in the
ab~ence of some severe mech~ic~l breakdown or overcharge o~ :
cataly8t. ~ore usuall~, the out-o~control r~action ~ill
occur in the latter ~tages ~hen the conversion i8 going up ~rcm ~-
about 12 to 15% to any sub~equent degree o~ cor~ver~ion up to
and including 100% conversion. I~, at any point during this
part o~ the react~on, lt i6 necessary to 510w down or stop
the pol~rmerization, nitric oxide i~ added at point~ in the ~yste~n
to obt~in maximum r~pld mixing and contact as wlll be readily : .
evident to tho~e skilled in the art, depending mos~ly on the
type of equipment that i~ being u~ed. To be most Qf`f~3CtiVe,
the mass oi the nitric oxide i~ preferably disper~ed through
the v~ ctiloride monomer~vin~rl chlo~ide polymer mas~. The ;~
reaction between nitric oxid& and initiator i~ rapld in ~uit-
able ~y~tems with efficient d1 stributlon of nitric oxide by
adequate point~ of entry ~d/or a~itation. It wlll b~ obv~ous,
of course, th~t the ~vai1~bility Or increased agitatioal during
the lntroduction o:~ the nltric oxide 7rould be ad~rantageou~.
It i~ pre~rred that æ subatantially o~ygen~rree
polymeriz~tion syst~m be used, other than uxygen sourco ~rom
~8~
;'.
~5~69~3
the catalyst which is minimal. Usual precautions in excluding
oxygen ~rom such ~inyl chloride polymerizatlon systems are
generally adequate to prevent the .~ormation of excess ~mounts
o~ nitrogen dioxide which are not desired.
A~ter the polymerization the ~ass may be expelled
from the rea~tion system ~nd the wnreacted nitric oxide and
~lnyl chloride vented under proper safety condltions prior to
~urther processing of the vinyl chloride polymer. When minimum
amount~ of nitric oxide~ are added to only 810w the polymeri-
zation to the desired degree or ~n exact equi~olar a~ount has
been added to react wlth the catalyst, the polymerization may
be reiniti~ted under controlled condition~ with additional
desired ~ree radical catalyst~ to continue the polymerization
i~ this 18 desirsd.
Enough nitric oxide may be added to a particular
polymerization to produce ~ precalculated ti~e delay ln the
polymerization. To determlne th~ amount o~ nitrlc o~ide ne-
cessary ~or such delay or retardatlon~ the amount o~ initlator
~hat wlll decompose during the del~y i~ calculat~d, or in
other word~, one c~lculat~s the amount of nitr~c ox~de required - i
to react qu3ntitatively wlth ~ree radicals rormed during a
~iven p~rlod of ti~e.
~.
A qimple equatio~ bas~d on rir3t order de~ompo~itlon
kinetic~ i8 u3ed ~or the~e eimple calculations and one r~quires
only the lnltlal catalyst concentration, polymeri~a~ion time,
nitric oxlde lnduced delay ti~e snd half-lire o~ the lnitlator
in vinyl ehlorid~ at the polymeri~tion te~p~rature. mus,
the a~ount u~ed depends upon the inltlator halr;li~e ~nd con-
centrat~on, ~he t~mperature, the ti~e to beginnlng o~ the delay
in polymeri~tion ~nd length o~ the del~y, E~h ~ol~cule o~
dceompo~ing initiator produces two free r~d~cal~ and, there~ ,~
~ore, two ~ol~ o~ nltric oxide are required ~or co~plete re~c~
-9- .
1~5~69~3 '
tlon with one mol o~ cataly~t. For control pu ~ oses of course,
much less than two mol~ o~ nitric oxide may be used depend~ng
upon the degree of control and t~ml3 del~y deslred.
To demonstr~te th~ proce~s of thi~ invention, poly-
merizations are conducted ln 30 ga:Llon ~talnless st~e~, Jacketed
pressure ~28~el8 equipped with vertical ~nchor agitator and a
brine cooled condenser. A pr~ssure controller regulate~ the
brine ~low to the condenser controlling ths internal reactor
pres~ure. A temperature rlse in the re~ctor measured at con-
~tant pre~sure ~8 used a~ an lndic~tlon o~ the beginning o~ a
pre~ure drop. ~ gas chro~stograph i~ used to ~onitor con~er
eion in the re~ctor. A small qu~ntity of n-butane, about one `.
part per 100, i~ used as ~ r~Perence materi~
In one ~mbodimen~ o~ the inventlon there wa~ charged
to the reactor 100 weight ~arta of ~inyl chloride ~ono~er9 43 ~:
weight p~rts o~ polyvinyl chlorid~ o~ a~out 200 ~icrons di~-
meter and ha~ing a vi~co~ity ~ cycldhexane o~ o.g6, 0.07 part
of secondary butyl peroxydicarbonate and the system ~luæhed
with 1.42 parts o~ n-but~ne. At about 35 minutes ~ter reac-
.1 20 tion a~ a t ~ era~ure of 5BC., at which time the co~ver~ion
of monomer to pol~mer had reached about 66%, 0.0039 weight
part Or ni~ric oxide (o.436 ~ol per m~l of catalyst) ~a~ added ;~
to the polym~rl~atlon reaction and the ~onversion measured at
15 mlnute l~t~rvals thereafter. The pol~erlzation coaYa~ion
re~alned con~t~nt at about 6 ~ ~or 1-3/4 hours. APter one
hour and ~orty~ minutes, the polymerization react~on beg~n
again and w~nt to grea~r than 80~ conv~rsion in le~s than
four hours. The r~sultlng poly~ nYl chlorido wae reco~ered
and ~r~ed Or mono~er ~ d dried and ~ound to be acc~pt~le
quality ~or c~ ercial U80 and had a vlsco~ity o~ abou~ 0.95.
The polymerlzati~n rate b~rore adding shortstop ln thi~ reae
tlon ~B 8 ~ p~r hour, a~d a~ter the t~o hours d~l~y the r~te
-10-
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1-~596g~ '
a~ter the reactlon began again was 36% per hour, which ls
readily increased ~y ~dding additional initiator to the reac-
tion.
In another demonstration of the practice o~ the
invention ~n the same equlpment, 100 welght parts o~ vinyl
chlorlde mono~er, 1.2 parts o~ sod:~um dodecyl benzene ~ulfonate,
0.05 weight parts o~ secondary butyl peroxyd~carbonate and
1.0 part o* n-butane were ch~rged to the reactor. In thi~ Ex-
ample~ 50 pound~ o~ vinyl chlorlde monomer were u~ed. After
the polymerization had been under way for 1.5 h~urg, 20.6
millimol~ (0.0027 weight parts or 0.425 mol per mol o~ initia-
tor) of nitric oxide W&S charged to the poly~erization directly
into the poly~erizer and polymerlzation wa~ ~mmediately stopped
and remained ~topped ~or 2 hours. Therearter th~ polymeriza-
tion re~umed and reached a percent conv~rsion o~ 66 a~ter about
a total o~ 7 hour~. In thi~ example, the nitric oxide was
added to the polymerizer v~por spare and ~mmediate st~pp~ge
o~ the vinyl chloride maæ polymerization wa~ obser~ad. In
addition to the constant conYersion ~igure noted during the
delay period9 the stopp ~ e o~ polymerizatlon was also re~lected
by the sudden reduction in coollng requ~r~ment and dropplng ~f
; t~mper~ture and pressure i~ide the poly~erizer. The nitri¢
oxide may be add~d below t~e top level o~ the reactlon mass
so long ~ precautlon~ are taken to pr~vent blockin~ oP any
25 5uch en~ry point. The nitric oxlde may al~o be ln~ected into
the reactor by puttlng th~ nitrl~ oxide in agit~tor se~l ~atèr .~:
and overpressuring the system ~o that th0 ~ater containing ` -
the nitric oxide is introduced lnto the rea~tor. ~a~y oth~r
entry points to ob~ain rapid mlxing ln the polymerizatio~ mix ~.
~111 b~ obviou~ to thnse skilled in the art.
On a l~rgsr scal~ poly~erizatlon ln ~ co~merclal
plant9 i~ the roactlon oP about 20,000 pound~ o~ vinyl chlorlde
.
3L~59~
containing about o~o68 weight part of initiator, aft~r th~
v~nyl chloride had polymerlzed 2 hour~ and 15 minutes, which i8
wlthin the tlme range when many out-o~-control re~ction~ have
occurred, 165 grams (0.002 weight part per 100 w2ight parts of
vinyl chloride monomer, about o.36 mol~ol lnitiator) wa~
added to the reaction. On the addiLtlon, the reactio~ ~topped
immediately. Be~ore the addition the ~utocalve ~a~ taking
full eooling wa~sr and a~ soon a~ th~ nitric axide ~as added
the pres~ure controller cut o~ the coollng ~a~er and was un-
able to maint n the pres3ure in the re~ctor ~hich was decre~-
ing rapidly. This polymerlzatlon and th~ ~toppin~ ther~o~ ~a~
repeated with only 6B gr~s o~ nltr~c ~x~d~ und again thls
amount o~ nitrlc oxid~, 1 weight part p~r 100 ~e~ghg p6rts of
inlti~tor, ~ more than snough to co~pl~tely stop th~ re~c
tion which did not begln ag~in. The poly~er reco~red ~ro~
these reactor~, although having incr~as~d porosit~ bec~u~e of
le~ than essentinlly co~plet~ c~nverslon ~a8 otherwis~ ~atis- ~;
P~ctory ror proc-~sing into usenul articles.
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