Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
:.:
-- 1 --
This invention relates to the polymerizztion of
2 elastomeric isoolefinic homopol;7mexs and copolvmers, es-
3 pecially the polymerization reaction re~uired to produce
4 the isobutylene-isoprene _orm of butyl rubber. More part-
5 icularly, ~he invention relates to a method o~~ stabilizins
6 against agglomeration the polymerization slurries used in
7 the preparation of such polvmers, the medium or diluent of
such slurries being methyl chloride or certain other polar
c, chlorinated hydrocarbon diluents.
The term "butyl rubber" as used in the specifi-
11 cation and claims means copolymers of C4 - C7 isoolefins
12 and C4 - C14 conju5ated dienes which comprise about 0.5
13 to about 15 mole percent conjugatec diene and about 85
14 to 99.5 mole percent isoolefin. Illustrative examples of
15 the isoolefins which may be used in ,he preparation o. butyl
16 rubber are isobutylene, 2--methyl-1-propene, 3-methyl-1-
17 butene, 4-;nethyl-1-pentene and ~-pinene. Illustrative
18 examples of conjugated dienes which may be used n the
19 preparation of but~,~l rubber are isoprene, bu~adiene, 2,3-
20 dimethyl butadiene, piperylene, 2,5-dimethylhexa-2,~-ciene,
21 cyclopentadiene, cyclohexadiene and methylcyclopeniadiene.
22 The prepara'ion of butyl rubber is described in U.S. ~atent
23 2,356,128 and is further desc-ibed in an article bv R. M.
24 Thomas et al. in Industrial and rnsinee-ins Chemist-y,
2~ vol. 32, pp. 1283 et se~., Oc,ober, 1940. Bulyl ~ubber
.
1''~'
-- 2 --
1 genera~ly has a viscosity average molecular weight between
2 about 100,000 to about 800,000, preferably about 250,000
3 to about 600,000 and a Wljs Iodine No. of about 0.5 to
4 50, preferably 1 to 20.
The term isoolefin homopolvmers as used herein
6 is meant to encompass those homopolymers of C4 - C7 isoole-
7 fins paxticularly polyisobutylene, which have a small degree
8 of terminal unsaturation and certain elastomeric proper-
g ties. The principal commercial forms of these butyl
rubber and isoolefin polymers such as isobutylene-isoprene
11 butyl rubber and polyisobutylene, are prepared in a low
12 temperature cationic polymerization process using Lewis
13 acid type catalysts, with aluminum chloride typically being
4 employed. Boron trifluoride is also considered useful
5 in these processes. The process extensively used in
16 industry employs methyl chloride as the diluent for the
17 reaction mixture at very low temperatures, that is less
18 than minus 90~C. Methyl chloride is employed for a
19 variety of reasons, including the fact that it is a sol-
20 vent for the monomers and aluminum chloride catalyst and
21 ~ nonsolvent for the polymer product. ~lso, methyl
22 chloride has suitable freezinc and boilins points ~o
23 permit, respectively, low temperature polymerization and
24 efLective separation from ~he polymer and unreacted monomers
The slurrv ?olymeriz2tion ?rocess in methyl
,~ chloride offers a nu~ er of additional advantages in
44~
-- 3 --
1 that a polymer concentration of 2pproximatelv 30~ by
2 weight in the reaction mixture can be achieved, as opposed
3 to the concentra~ion of only about 8~ to 12~ in solution
4 polymerization. Also, an acceptable relatively low viscosity
Oc the poly~nerization mass is obtained enabling ~he heat
6 o. polymerization to be removed more e~fectively by heat
7 exchange. Slurry polymerization processes in methyl
8 chloride are used in the production of high molecular
9 weight polyisobutylene and isobutylene-isoprene butyl
rubber polymers.
11 Notwithstanding the widespread use of the slurry
12 polymerization process in methyl chloride, there are a
13 number of problems in carrying out this process which
14 are related to the tendency of the polymer product part-
icles to agglomerate, and therebv destabilize the slurry
16 dispersion. The rate of agglomeration increases rapidly
17 as -eaction temper2ture approaches -90C. It is not possible
18 to maintain a stable slurry above -80~C. These agglomerated
19 particles tend to adhere to and to arow and plate
ou~ on all surfaces thev contact, such as reacto dis-
21 charge lines, 2S well 2s reactor iniet lines and any
22 heat trans er equipment being used to remove ,he exother-
23 mic heat o~ olymeriza~ion, which is critical since low
24 temper2ture reaction conditions must be mzintained.
~ereto.o~e, no e-fCective technique o stabil-
26 izins the sl~rry has been found other than bv ope~ation
-- 4 --
below -80C and with hish agitation in the reactor. It
h2s become standard practice to desisn m2nu~2cturins
3 facilities with additional reactor equipment so that the
4 reaction process can be cycled between alternate reactor
systems so that at any given time one or more re2ctors
6 are in the process of being cleaned. If a stable slurry
7 could be produced and maintaine~ in a non-fouling condi-
8 tion, substantial economies in equipment ins,allation and
9 process techniaues could be achieved. A further limitation
imposed by the tendency of the polymer product particles
11 to agglomerate is the inefficiency of heat exchange, which
12 effectively prevents any attempt to heat exchange the cold
13 reactor effluent with the incoming feed in order to rea-
1~ lize savings in the refrigeration enercy reauired.
A general reference text which discusses the
16 heory and principles concerning dispersion pol~tteriza-
17 tion and in particular the use of block and graft co~oly-
18 mers as dispersion stabilizers is "Dispersion Po_vmeriz2-
19 ~ion in Organic Media", edited by K. E. J. Barrett, John
Wiley & Sons, 1975. While this text, tarticularly in
21 Chapter 3, discloses the use of block or gr~ft copolv-
22 mers having an insoluble comDonent, o- anchor sroup, ~nd
23 a diluent-soluble componer.t in a number o' dispersion
2~ polvmerization processes, no disclosure is made of any
stabilizer sys.em useful in the methyl chloride slurry
26 polymerization p~ocess for isoolefin homopolvltters or butyl
: .
- 5 -
.; .
1 rubber copolymers as aisclosed in accordance with the
2 present invention.
`3 In published Netherlands Application 770760
`4 (1977), filed in the U.S. on June 14, 1976, as S.N.
699,300, Markle et al disclose a non-aqueous dispersion
6 polymerization process ror conjugated diolefins in the
7 presence of a block copolymer dispersion stabilizer, at
8 least one block being soluble in the liquid organic dis-
9 persion medium and at least another block being insoluble
10 in the dispersion medium. The Markle et al disclosure
11 deals with the polymerization of a conjugated diolefin
12 monomer in a liquid hydrocarbon dis?ersion medium such
13 25 n-butane, neopentane or mixed isomeric pentanes in
1~ the presence of a Ziegler-Natta Catalyst. The conjugated
15 diolefins, particularly preferred by .~arkle et al, are
16 butadiene-1,3, isoprene and piperylene. M2rkle et al
- 17 also disclose mixtures of conjugated diolefins.
18 The process of the present invention is consi-
19 dered distinguished from the disclosure of ~arkle et al
2~ in that it relates to a c2tionic poly~erization carried
21 out in a polar chlorinated hydrocarbon diluent, such as
22 methyl chloride, utilizing stabilizers which are especially
2~ effective in that polymerization process. Markle et al
24 ceal with anionic polymerization processes concucted in
25 a non-pola~ uia hydrocarbon diluer.t.
26 So far as the inventors hereo~ are aware; no
-- 6 --
i e_fec.ive method for stabilizing me.hyl chloride slurries,
2 nor slurries in any type of diluent, used in the produc-
3 tion of isoole'in polymer ?roducts wi~h chemical additive
4 s,abilizers is kno~n or disclosed in the prior art.
In accordance with the present invention, .here
6 has been discovered a method of stahilizinq a polymeri-
7 zation slurry against aaglomeration, the slurry contain-
8 ing an isoolefin homopolymer or a butyl rubber copolymer
g in a polymerization diluent,' the diluent being methyl
1~ chloride, methylene chloride, vinyl chloride or ethyl
11 chloride, which comprises incorporating into the reac-
1~ tion mixture which com?rises the mixture Oc monomers,
13 catalyst and diluent, or into the polvmerization procuct
1~ slurrv about 0.05~ to 20~ by weight, based uPon the
15 weight OI product isoolefin homopoly~er or product butyl
1', rubber copolymer, of a stabilizing agent, the stabilizing
17 agent being (i) a prefo~med copolvmer having a lyophilic,
18 ciluent soluble portion and 2 lyophobic, ciluent insolu-
19 ble, isoole'in homopolvmer or butyl rubber soluble or
2~ adsorbable ?ortion, the stabiliz ng agent being cGpable of
21 forming an 2dsorbed solu~ilized polymer co2ti~g around the
22 precipitated isoolerin homopolymer or butyl rubber copoly-
23 mer to stabilize the slurry, or (ii) an in situ ~ormed
24 stabilizing agent co olymer formed lrom a st2bilizer pre-
25 cursor, the stabilizer precursor being a iyophilic poly-
26 mer con..aining a ~unctional crou? ca?able o~ copolvmerizing
or fo.mlns a chemic21 bond -~Ti_h '~he isoolefin polvme-
,' .
, - . . . .
3Z~
_ 7 _
1 or butyl rubber copolymer being formed in the main poly-
2 merization process, the functional sroup being a cationi-
3 cally active halogen, either ?en~ant or enchained or
4 cationically active unsaturation, the lyophobic portion
of the stabilizing agen, being 'he isoolefin homopolymer
6 o~ butyl rubber copolymer which is being formed in the
7 main polymerization process, the sLabilizins agent so
8 formed being capable of formlng an adsorbed solubilized
g polymer coating around the precipitated product polymer
to stabilize the product polymer slurry.
11 The quantity of stabilizins agent set for,h
12 above is expressed as a pereent by weight of the produet
13 isoolefin homopolymer or butyl rubber copolymer. The exaet
14 ~uantity of stabilizer agent added to the reaction mixture
is a function of the exact concentration of the feed blend
16 and the estimated degree of conversion of monomers. In a
17 typical butvl rubber reaetion process 'or manufacturing
18 isobutylene-isoprene butyl rubber, tne reactor -eed blend
19 which is prepared contains about 25% to 35% by weight
monomers, and typically 80% to 90% bv weisht o~~ monomers
21 are convertee to polymer produc,.
22 The present invention deals with two ~orms o'
23 suitable stabilizing agents, both of which are effective
24 in the polymerization diluenL and serve to stabilize
,he polymerization slurry comprised of ,he polymer or
26 copolvmer p2rticles ~hieh are ?rocueec in the basic
27 polyme-ization reaction. ~s used herein, the term "poly-
.; .
.
:l~g5~36
1 merization diluen." is meant to re_er to methyl chloride,
2 methylene chlori~e, vinyl chlori2e and ethyl chloride.
3 '~ethyl chloride is the Drefer-ec diluent in all embodi-
4 ments of this invention.
Utilization o a preformed block or sraft co-
6 ?olymer, which is both lyophilic and lyophobic in the
7 presence o~ the polymerization diluent, i..volves first
8 providing a suitable copolvmer. Generally, a preformed
9 copolymer stabilizer must have a diluent insoluble anchor
portion, which is adsorbable or soluble in polymerized
11 isoolefin or butvl rubber, as well as a diluent soluble
12 portion which functions to keep the adsorbed polymer dis-
13 persed in the polymerization diluent.
14 The pre ormed block or sraLt cop~lymer stabilizer,
subject to certain limitations as set 'orth below, may be
16 added to the reaction mixt~re and can be present ~hroushout
17 the polymerization reaction 'o prevent agglomeration at
18 reaction temperatures. Alternativelv, a portion of the
19 ?reLormed stabilizer can be added to the reaction mixture
and aàditional s~abilizer can be injected into the reactor
21 e-fluent lines to prevent aaslomeration in cownstream
22 equi?ment
23 Certain cateaories of preformec stabilizers,
24 wnile being effective as slu~ry stabilizers in the ?resen_
invention, shoula on'y be addec u?on com?letion o' the
26 pol~erization reac.ion. Thus, thev are pre~e-ablv added
27 to the reacto- e~'luen. in order ~o ?~event asclomeration
l~V~,8~
g
1 durins the inal stases of processing. These preformea
2 stabili~.er copolvmers a-e define~ as those containin~a a
3 substanti21 amount of cationicallv actlve unsaturation or
functional groups, he function~l sroups being hydroxyl,
ester, ketone, amino, aldehyde, nitrile, amido, carboxvl,
6 sulfonate, mercaptan, ether, anhydride, nitro, active
7 ailylic or ac~ive tertiary halogen. Preformed polvmeric
8 stabilizing agents which are predominantly hydrocarbon in
g nature and are lree of cationically active unsaturation
and meet the other requirements as described herein can
11 be incorporated into the slurrv during the polymerization
12 process itself by being made a component of the reaction
13 mixture.
14 The lyophilic portion of the preformed copoly-
mer stabilizing agent employèd in the present invention
16 must be completelv soluble in, or miscible with, the poly-
17 merization diluent. A suitable criterion is that the
18 lvophilic portion have a Flory-Huagins interaction para-
19 meter with the polymerization diluent of less than 0.5
20 or a Flory solvency coef~icient with the ?olymerization
21 diluent greater than 1.
22 Suitable lyo?hilic ?olv~ers which meet these
23 requirements and which do not adversely ~ffect the cat-
24 alvst or poly~.erization conditions include ?olystyrene,
25 polvvinyl chloride, ?olvvinvl bromi~e anc neoprene, with
:; 26 the pre~erred lvophilic ?ortion beins ~olystvrene, ?oly-
; 27 vinyl chloride, or pol~vinyl bromide. Also suitable a-e
-- 10 --
1 subs~ituted styrene lyophiles such as mono-, ~i- and tri-
2 subs~ituted s~vrenes, the substituents being halogen, such
3 as chlorine, or lower (C1 - C5) alkyl groups, zs illus-
4 tra.ec by alpha-methyl styrene, Rara-t-butyl-styrene,
?-chlorostyrene and similar ring chlorinated styrenes.
6 It is also suitable to employ as the lyophilic portion
7 combinations of two suitable lyophilic polymers such as
8 copolymers of styrene and vinyl chloride. Thus, the
9 term "lyophilic portion" as used herein is meant to
encompass a portion composed of one or more monomers
11 which meet the criteria 'or suitable lyophiles in the
12 practice of the present invention. This lyophilic por-
13 tion should have a desree of polymerization (D.P.) of at
14 least about 20 and up to about 5,000 or 6,000.
A number of significant factors influence the
16 selection of the lyophobic portion o~ 'he stabilizing
17 agent. The lyophobic portion is insoluble in polymeri-
18 zation diluent but shoulA have a high affinity for the
19 ~ro~uct polymer so that it is aasorbed or o he~ise
bonded onto the polymer particle. A lyophobic portion
21 composed o~ the same material beins ?roducec in the
22 cationic Lewis Acid catalyzed polymeriz2tion re2ction,
23 such as isobutvlene homopolymer or isobutylene-isoprene
24 butyl coDolymer, m2kes an ideal lyophobic portion in the
preformed stabilizer asent emDloyec in the present inven-
26 tion. Suitable lvophobic materials cenerallv include
27 ailuen. insoluble pol~,~e~s having a solu~ili.y p2r2meter
86
1 less than about 8 and a degree of polymerization (D.P.)
2 of at least about 10. Suitable materials include polyis-
3 olefins generally of C4 - C7 isoolefins, such as poly-
4 isobutvlene, butyl rubber copolymers generallv, such as
isobutylene-isoprene butyl rubber, polybutadiene, poly-
6 isop~ene, e,hylene/propylene copolymers, EPDM terpoly~ers,
7 hvdrogena~ed diene polymers, e.s. hydrogenated polybuta-
diene, SBR Rubbers, which are s~yrene/butadiene randcm
g co?olymers of low styrene content and polydimethvl silicone.
A particularly preferred prefonned stabilizer for use in the
11 production of isobutylene-isoprene butyl rubber is a pre-
1~ formed block copolvmer stabilizer asent composed of an isobu-
13 tylene-isoprene portion block or graft with about 20 to 80
14 weight percent stvrene block or graft. Also pre'erred is
a s.vrene-~PD~ preformed stabilizer.
16 In situ ~onnation of the stabilizer utilizes a
17 lyophilic polymer com?onent having a functional group
18 capable of reacting with the isoolefin or butyl rubber
19 ?olymer being fonmed in the main polymerization ?rocess.
In this embodiment, the polymer being prepared becomes
21 the lvophobic portion of the copolymer stabilizer.
22 The in situ metho~ of preparins the stabilizer
23 copolymer in ~he present invention involves irst ?roviding
24 a stabili er precursor which is a lyophilic polymer having
25 a 'unction~l sroup capable of copol~nerizinc or otherwise
26 reactinc wi,h ~he isbolefin ?olv.-"er, e.c. polvisobutylen.e
27 or isobu ylene-isoprene, being for;ned in the main pol~ner-
1 ization reaction '.o ,Grm the bloc~ or graft copolymer
2 stabilizer in accordance with the present invention.
3 The functional g~oups may be ca'ionically active pendant
4 or enchained halogen, preferably chlorine, or cationi-
cally active unsaturation.
6 Formation of these stabilizer precursors may be
7 accomplished through free radical polymerization o, 2
8 lyophile such as styrene in the presence of carbon tetra-
9 chloride or by Sree radical copolymerizztion o, a lyophile
10 such as styrene with vinyl benzyl chloride. These stab-
11 ilizer precursors will contain active halogen which lead
12 to in situ formation of the stabilizer copolymer in the
13 present invention through a chain transfer or co-initiation
14 reaction mechanism.
Formation of a stabilizer precursor containing
16 cationically active unsaturation as the functional group
17 in the lyophile can be accomplished by anionically poly-
18 merizing a lyophile such as styrene and ca~ping it with
19 'vinyl benzyl chloride or methallyl chloride whereby the
residue o~ this vinyl benzyl chloride or methallyl chloride
21 yields cationically active unsatura,ion. This stabilizer
22 precursor .her. Lorms the s~abilizer co~olymer OI the
23' p~esent invention by co~olyme~izing with the isoole in
24 polymer or butyl rubbe~ copol~er being fo-~ed in '~he mai~
25 'polymerizalion reaction.
26 rhe above'emboci~ents may be illustratec by i-s~
27 considering lvo?hilic polvs_vre~es havi~g 2 reactive
- 13 -
1 chlorlne as an end group:
2 ~C~A2 ~ C~ ~--CH2 - CE~ ~ Cl
3 ~ ~J,~ ~ I
4 or an active enchained chlorine pendant to a styrene poly-
mer chain
6 ~ C~2 CIH ~ CR2 Cl t 2
8 C 2
9 Lyophilic polystyréne stabilizer ?recursors
represented above containing terminal or enchained active
11 chlorine can be prepared, respectively by polymerizing
12 s.yrene using free radical catalysts in the presence of
13 carbon tetrachloride which acts as a transfer agent to
1~ yield a chlorine capped polystyrene znd bv copolymerizing
lS styrene with a minor amount of vinyl benzyl chloride to
16 form a polystyrene containing enchained vinyl benzyl
17 chloride.
18 These lyophilic portions containing an active
19 halosen will incorporate polystyrene into a polyisole in
or butyl rubber copolymer chain by a transfer mechanism
21 or co-initiation mechanism. Chain trans_er is best illus-
22 trated by -e~erence to an isobutylene ?olymerization. In
23 this reaction a growing isobutylene carbonium ion abstracts
24 the actlve halogen as a C ~ from the lvophilic polvstyrene
to yield a Cl~ cap?ed polyisobutylene chain and a poly-
26 styryl carbonium ion which, in the presence of isobutylene
2/ monomer, p o?cs2~es to ~orm a stabilizer block copol~er
2~'~ consistins of a polystyrene chain 2ttached to an isobuty-
29 lene chain. .~ ~raft copolymer can also be formed and in
B
:
~ 1146~286
1 D, --
l the present invention the ,erm stabilizer copolymer or
2 stabilizer polvmer may include blocks, grafts, mixtures
3 thereof or other configurations resulting from copoly-
:.
4 merization reactions. The same mechanism would 2pply to
utilization in isobu.ylene-isoprene polylnerization. The
6 mechanism is illus,rated for reaction with polyisobutylene
7 by the following ecuations:
9 ~ ca2 ~ I ~ 32 ~ ~ + ~ 32 ~ C~ ~ C32 - C~ - Cl
lO CH3 CH3 ~ ~
ll Polyisobutylene Carbonium Ion Lyophilic Polystyrene
:
l3 C'~2 ~ I ~ Cl t ~ C32 ~ ~J c~2 - 1~
16 Chlorlne-Capped Polyisobutylene ?olystyryl Carbonium Ion
17 Chain
;~ 18 +
l9 CH2 = C (CH3)2
Isobutylene M.onomer
22 ~ C32 - CIP j C32 - C ~ Ca2 - C 7 c~2 c = ca2*
23 ~ ~ CH3
24 CoDolymer Stabilize-
* Where the end group depends upon reaction
26 conditions anc may be other than that shown above.
27 Co-initiation may be illus.rated with -eference
28 to the following e~uations showing the ~.lC13 polymeriza-
29 ,ion of isobutvlene where the stabilizer precursor is
f~Z~6
-- 15 --
l 2 chlorine-containing polystyrene.
AlC13 + ~ CH2 - CIH ~ CH2 - CH - C1
3 ~ ~ J ~ ' ~
4 Aluminum Chloride L ?hiliC Functional Polystyrene
6 H
7 ~ CH2 - C~H ~ CH2 C~ [AlC14]
g (Polystyryl Carbonium Ion) (~.~uminum Tet-achloride
Gegenion)
11 ¦ L
12 ~ CH2 = C (CH3)2
13 (Isobutylene Monomer)
. . ,
~ 14 ~ ~ H ~ C13 ~ CIH3
~ CH2 - CIH T CH2 -~- ~ CH2 - f t CH2 c = CH2
16 ~ ~ J ~ ~ CH3 J
17 CopGlymer Stabilizer
18 S.abilization of ',he polvmeriz2,ion slurry can
19 be accomplishea utilizing as the stabi1izer ?recursor an
anionically polymerized lyophile, such as ?olystvrene,
21 capped wi.h .he residue of vinvl benzvl chloride molec~le
22 or a methallyl chloride molecule representec. resDec.ively
. . .
23 by Cormulas I and II below:
24 (I) ~ CH2 - CH ~ ~ CH2 ~ CH = CH2
~J~
(II) ~CH2 - C ) ~ CH3
28 ~ bei~g an integer such that the .~ln Oc the polvstyrene
29 cnain is about 25,000 to 75,000.
46~Z~
- 16 -
1 In this emboZiment of the present invention,
2 the func~ional lyophile 2S illust~ated by polystyrene is
3 capable OL copolymerlzing with isoole'in through the
4 residue of the vinyl benzyl or methallyl unit, which
contains cationicallv active unsaturation. Stabiliza-
6 tion is effected by linking the diluent soluble polymer
7 chain to the isoolefin polymer or butvl rubber copolymer
! 8 as it is formed in the polymeriz2tior, process. A vinyl
9 benzyl chloride capped polystyrene is especially preferred
in the stabiliz2tion of methyl chloride slurries containing
11 isobutylene-isoprene butyl rùbber copolymer and this
12 stabilizing agent is prepared by anionically polymerizina
13 stvrene to a molecular weight of 25,000 to 75,000 in the
14 presence of n-butvl lithium catalyst anZ then adding vinyl
benzyl chloride to cap the livina polystyrene chain anc
16 precipitate lithium chloride to form the st2bilizins agent
17 set ,orth in formula I above.
18 Fmployment of a stabilizer precursor comprising
19 the Ziluent soluble polvmer with a functional group being
capable of 'ormins a cov2ient chemiczl bonZ with the
21 isoolefin unit in the polymer product, that is, with
22 isoolefin homopolymer or with the isoolefin portion of
23 butyl rubber copolymer, means that .he insoluble or
24 lyophobic portion is not formed until Ihe stabilizer
precursor becomes attached to an isoolefin unit durins
26 ~olymerization. ~hus the stabilizing molecule is formed
27 in situ Gu~ing the polymerization process. Selection of
28 the lvophilic portion is governeZ bv the same consider-
29 ations, inciuding the degree o' polymerization values,
- 1~4~28~
- 17 -
1 described above when the preformed block copolv~er stab-
2 ilizing agent is used. ~hus, suitable pol~merlzation
3 diluent soluble polymers include polystyrene, ?olyvinyl
4 chlori~e, polyvinyl bromide, neoprene and the substituted
styrenes as described hereinabove, with ?olys,yrene being
6 particularly preferred.
. . .
7 In usins this stabilizing method, it is impor-
8 tant that the functional group be active under the cat-
9 ionic ~olymerization conaitions and that the stabilizing
a5ent and functional arouD not interfere with any aspect
11 of the basic polymerization process. In cont~ast, when
12 the pre'ormed copolymer is used, its e_fectiveness is not
13 dependent upon in situ com?letion o' the 'ormation of the
14 stabilization agent.
Suitable lyophilic polystyrenes with Lunctional
16 g~oups cz3able of bonding with .he ?roduct ?oly~er and
17 eseciallY with an iscbutylene unit in preparation o'
18 polyisobu~ylene homo?olvmer or isobutvlene-iso?rene butyl
19 rubber copolymer are those functional ?olystyrenes having
a num.ber average (.~n) molecular weight in the range of
21 about 5,000 to 150,000 and preferably in the ranse o~
22 about 25,000 to 75,000.
23 The process of the present invention offers a
24 number o' significant advantages resulting from the
achievement o' a stabilized butyl rubber slurry. These
26 include elimination of reactor equipment fouling and
27 plugging, the ability to operate at higher slurry con-
28 centrations, increased reactor production rates, the
29 capability of re'rigeration recovery by heat exchange
2~
- 18 -
1 of reactor effluent with incoming reactor eed, ir.creased
2 -eactor run length time 25 well as the ability to polymerize
3 at warmer reactor tem?eratures.
` 4 A further embodiment of the present invention
: .;
com?rises the stabilizeà slurries cf isoolefin homopolymer
6 or butyl rubber copolymer prepared in accordance with the
7 present invention containing U? to about 50% by weisht
8 isoolefin homopolvmer or butyl rubber copolvmer, parti-
9 cularly a s.hbilized slurry of isobutylene-isoprene butvl
.~.
rubbe- in methyl chloriae, said slurry containing up to
11 about 50~ by wei~ht but~l ru~ber, or a slurry containing
12 u? to abou~ 50~ by weight polyisobutylene.
13 A further embodiment of the present invention
14 is a novel me'hoa of preparing non-aoglomerzting homo-
?lYmers o~ C4 - C7 ~soolefins an~ butyl rubber copolv-
16 mers bv pol~erizing the correspondinc monomers at tem-
.. . . .
17 peratùres from about -90C to about -20C in the presence
18 of a Lewis Acid cationic polymerization catalyst in a
19 polymerization diluent selected from the group consisting
2~ of methyl chloride, methylene chloride, v-nyl chloride
21 and ethyl chloride in the presence of a stabilizer, the
22 stabilizer being either (i) a preformed copolymer having
23 a lyophilic, diluent soluble portion and a lyophobic
24 diluent insoluble but isoolefin or butyl rubber soluble
or adsorbable portion or (ii) an in situ formed stabil-
26 izer copolymer formed from a stabilizer precursor which
27 is incorporate~ into the -eaction mixture, the stabil-
28 izer precursor being a lyophilic ?olymer containins a
29 functional grou? capable of copolymerizing or otherwise
-- 19 --
1 reactins with the isoolefin or butyl rubber co?olymer
. . .
2 beins ~ormed in the main ?olymerization process, ~he
3 ~unctional srou? being a cationically active pendant or
; 4 enchained halogen or ca~ionically active unsaturation,
the lyo?hobic portion of the stabilizing agent beins the
6 isoole'in or butyl rubber polymer ormed in the main
7 poly~erization process.
8 ~. particular point of novelty is the capability
9 to form non-aaglomeratins isoolefin homopolvmer or butvl
- 10 rubber copolymer 2' .emperatures of from about -90C to
11 -20C u~ilizing AlC13 as well 2s o~he- cationic Lewis
12 Acid polymerization catalysts such as aluminum alkvls, as
13 e~emlified ~y aluminum ethyldichloride, TiC14, 3?3,
~ SnCl~, 31Br3 ~nd other Priedel-Cra~ts c2talysts.
.. ....... _ _
~ A particularly preferred embodiment of the
lh present invention resides in the preparation of non-
17 aaglomeratins isobutylene-isoprene but~yl rubber bv cat-
18 ionic polymerization of the corres?onding monomers at
19 temperatures of from about -90C to -20C utilizing as
the catalyst AlC13 or aluminum ethvl dichloride in methyl
21 chloride, methylene chloride, ethyl chloride or vinyl
22 chloride diluent utilizing the stabilizer polymers of
23 the present invention. Heretofore, it has simply not
24 been possible to prepare non-ag~lomerating butyl rubber
at temperatures warmer than about -90C. Furthermore,
26 maintenance of a s.able polvmerization slurry at such
27 ~emperatu-es enables the use of a wide varietv of cata-
28 lys,s other than AlC13 to become ?rac.icable.
- 20-
1 The invention is .urther illustrated bv the
2 following ex~mples which are not to be considered as
3 limitative o' its scope. P.ll ?ercentages reported are
4 bv weight unless otherwise stated.
Exam~le 1
6 The followins two stabilizers were evaluated
7 in a butyl rubber polymerization reaction. The stabil-
8 izers are designated as "S-l" and "5-2".
g 5-1 - a ~utyl polymer (isobutylene-isoprene) with 29
wt~ styrene arafted onto it and h2vins a viscosity
11 averase molecular weight of 588,000.
12 S-2 - a butyl polymer (isobutylene-isoprene) with 19~
13 by weight of methyl methacrvlate grafted onto it
14 and having a viscosity average molecula~ weight
o~ 330,000.
16 In conducting the batch polymerization trials~
17 a butvl feed blend was prepared and divided into three
18 aliquots and then all three were stored cold with a~i-
19 tation until the sLabilize-s had completely dissolved.
The ~eed blends were preparec and handled in a nitroaen
21 purged dry box and specially purified ana dried monomers
22 and methyl chloride were used. ~ stirred bath filled
23 wi.h 2-me~hvl pentar.e and coolea to -9~C with liquid
2' ni.rogen was built into the dry box and the _lasks con-
taining the ~eed ~lenàs were kept colc by irmersion in
26 the col~ bath. m~ he three _eeà blends p-epared were~
. . .
-` 114~32B6
-21 -
1 A (Run 3) B (Run 1) C (Run 2)
2 Isobutylene 120.0 120.0 120.0
3 ~ethvl Chloride 101~.4 1014.4 1014.4
4 Isoprene 3.71 3.71 3.71
Slurrv Stabilizer ~one (S-l) 3.60 (S-2) 3.60
6 catalyst solution consisting of 0.18% AlC13 in methyl
7 chloride was also prepared for use in initiating poly-
8 merization-
9 After the stabilïzers had completely dissolved,
a batch polymerization was run with each of the feeds.
11 The flasks containing the feed blends and fitted with
12 a stirrer, thermowells, and port through which catalyst
13 solution could be dri~ped in, were immersed in the liquid
14 nitrosen-cooled 2-methyl pentane bath ir, the dry box and
stirred and cooled to -97C. Catalvst solution was then
16 allowed to drip in slowly f~om a dropping fur.nel to
17 initiate polymerization and cause the butyl slurrv to
18 form. ~he catalyst solution was dripped in slowly to
19 keep reactor temperature from warmi;ng above -90~C. When
sufficient polymer had been for~ea, the reaction was
21 auenched bv aadition of 25 ml. of colc ~lI3K (methyl
22 isobutyl ketor.e) anc the flask containing the auenched
23 slurry and with the thermowells and stirrer in place was
24 removed -rom the dry box and placed into a standard labor-
atory hood where i' was stirrea slowly and allowed to warm.
26 500 ml. o chilled .~I~K was added to the ,lasks and the
27 methvl chloride ana unreacted moncmers we~e allowed to
- 22 -
1 vent out into the hood throush the open port into which
2 the catalvs~ had been dripped. Bv the time the flasks
3 had wzrmed to room temperature, all the monomers and
4 me,hyl chloride had flashed off and the flasks con-
tained the butyl rubber produced durinq polymerization
6 in the MIBK. The stability of the slurry was observed
7 durinc polymerization and warm-up; and then the slurry
8 in MIBK at room temperature was care'ully examin ~ D~ f,Q~
9 before the polymer was recovered for analysis.
1~ Polymerization trial 1 was conducted with feed
blend B containing S-l as the slurry stabilizer--a total
12 of 150 ml. of catalvst was used and 85~ conversion of
13 monomers to butyl polymer was achieved. ~ stable slurry
14 resulted (as cescribed more fully below) and the recovered
polvmer had a viscosity average molecular weight of 302,000
16 and an INOPO of 10. "INOPO" is a method for the deter-
17 mination of the desree of unsaturation in butvl rubber
18 as reported in Industrial and Engineering Chemistry,
19 17, '67 (19~5); i. is also referred to as the Iodine-
20 Mercuric Acetate Method.
21 Polymeriza~ion t-ial 2 w2s conductec with feed
22 blend C containing S-2 as the slurrv stabilizer. The
23 polymerization was badlv poisoned and a .otal of 600 ml.
24 of cat21yst was adced to achieve onlv 32~C conversion of
25 monomers to polymer. Nevertheless, a stable slurry
- 23 -
1 resulted (as described more fully below) and the recovered
2 polvmer had a viscosity average molecular weight of 227,000.
3 Polvmerization trial 3 was conducted with feed
4 blend .~ containing no stabilizer. A total of 125 ml. of
catalyst was added to achieve 75'~ conversion of monomers
6 to butyl polymer. The slurry was very unst2ble and com-
7 pletely aaglomerated. The recovered polymer had a vis-
8 cosity averase molecular weight of 338,000 and an I~OPO
g of 10.
The very marked improvement in slurry stability
11 produced by the stabilizers was very a?parent in this
12 experiment. In Trials 1 2nd 2, containing the stabilizers,
13 the slurry produced during polymerization appeared as a
1~. thick milk with no agglomerates apparent. Furthermore,
no polymer plated out on the stirrer or any of the wetted
16 reactor parts; a small polymer rind did form on the reac-
17 tor wall at the vapor/liquid interface in the reactor,
18 and polymer deposited on the dry reactor wall due to
19 s~lashins. In Trial 3 containing no stabilizer, a much
heavier rind of polymer formed at the vapor/liquid inter-
21 face in the reactor and many agglomerates were visible in
22 ,he thick milk which formed. Furthermore, polvmer deposited
23 on the sti~re~ and all reactor surfaces so th2t it became
24 very diL.icuit to even obse-ve the slurry by the time the
run was terminated.
The di'ferences in slurry s.ability became even
3Z~:36
- 24 -
`' .
1 more pr~nounced during warming in the hood. In Trial 3
2 containing no stabilizer, the slurry agglomerated verv
3 rapidly as it was allowed to warm. At -850C, there was
4 no longer any milk left but a clear liquid containins
large agglomerates and pieces of rubber. As warming con-
6 tinued, all the polymer agglomerated into one large mass,
7 and stirring became impossible. In Trials 1 and 2 con-
8 taining the stabilizers, a noticeable coarsening of the
9 slurry occurred during warming so that visible particles
10 could be dis~inguished, but the slurry remained as a thick
11 milk in appearance and no agglomerates of appreciable size
12 formed. At room temperature a stable slurry still remained.
13 No polymer had deposited on the wetted surfaces, and most
14 of the rind had fallen into the slurry and was dispersed
15 as small pieces. The polymer deposited on the drv reactor
16 walls, of course, remained. At room temperature, the slurry
17 from Trial 1 was still a stable milX with many visible part-
18 icles up to 1/8" in diameter; whereas, the slurry Crom Trial
19 2.was a stable milk with almost no visible particles. Both
20 stabilizers were quite effective, but`S-2, the butyl/metha-
21 crylate graft copolymer was ,he bes.. However, as expected,
22 the polymethyl methacrvlate did inter ere stronsly with the
23 polvmerization so that much more catalyst was required and
24 the butyl molecular weisht was depressed. The butyl/methyl
25 methacrylate gract copolvmer would not be suitable for use
26 as a slurry stabilizer in the reactor, but could be injected
l~VZ~3Çi
-
1 into the reactor ef luent to stabilize the slurry for heat
2 exchange.
3 The creatly improved stability of '~le slurries
4 produced in Trials 1 and 2 was also evident during poly-
S mer recovery. The slurry particles were much too fine to
6 settle or screen out of the MIBK, and it was necessarv to
7 add a large amount of methanol (a non-solvent for the
8 lyophile) before the slurry could be caused to separate
9 from the MIBK for recovery. Éven then, the rubber remained
10 partlculate an~ was easily redispersed by stirring.
11 This work shows that butyl rubber slurries in
12 methyl chloricde can be stabilized with appropriate graft
13 copolvmers containing lyophobic and lyophilic portions.
14 The stabilized slurries survive warming to room ~emperature
15 without massive agglomeration and thus could be heat ex-
16 changed to recover sensible refrigeration energy. ~ graft
17 copolymer containing 29 wt% styrene grafted onto isobuty-
18 lene-isoprene butyl and a graft copolymer containing 19%
19 methyl methacrylate grafted onto isobutylene-isopren2 butyl
20 are both effective slurry stabilizers. The styrene graft
21 copolvmer does not inactivate the butvl polymerization
22 catalyst or inte-fere with polymerization and hence can
23 be added to the butyl feed to stabilize the slurry as it
2~ forms and prevent agglomeration and fouling in the reactor.
25 Example 2
26 A batch dry box polymeriza,ion was run to eval-
27 uate a diene/styrene block copolymer as a butyl slurry
28 stabilizer in the reactor durina polvmerization. The
- 26 -
1 stabilizer was a diene/styrene block co?olymer prepared
2 via anionic polymerization and designated as S-3. The
3 diene bloc~ was an isoprene/butadiene copolymer which
4 was attached to a pure stvrene block. The overall polv-
5mer composition W2S 27 mole ~ stvrene, 34.~ mole % isoprene
6 and 38.6 mole % butadiene with an Mn of 63,000. For con-
7venience in adding it to the reactor, the block copolymer
8 was dissolved in methylene chloride to give a 0.5% solution.
9 In order to conduct the batch polymerization
10 trials, a butyl feed blend was prepared in the dry box as
ll for Example 1. The feed blend consisted of:
12 Isobutylene 230.40 g.
13 ~ethyl Chloride 19~7.50 g.
Isoprene 7.13 g.
Polymerizations were conducted in stirred 500 ml,
16 4-neck round bottom 'lasks immersed in the liquid ni'rogen
17 cooled 2-methyl pentane bath in the dry box and each flask
18 contained a .hermowell to permit monitorins polymerization
19 temperature and a port into which catalvst could be dripped
20 to initiate polymerization. 230 g. aliauots o' the feed
21 blend (consisting of 24.25 g. isobutylene, 0.75g. lso~rene and
22 205 g. methyl chloride) were weighed into the 500 ml. reac-
23 tion flzsk 'or each batch run and the flask was stirrec and
24 cooled in the 2-me.hy~ pentane ~ath tc -83 C be~ore polymer-
25 ization-was initiated~ A warmer than normal polymerization
26 temperature W2S used so that an unstabilized slurry would
27 agglomerate in the reactor during polymeriza.ion and the
28 e_ ecti~eness of the stabilizer could thus immediately be
`U~
- 2i -
1 determined. Catalyst was allowe~ to drip in slowly to
2 Xeep reactor temperature below -80C 2nd the polymeriza-
3 tions were quenched with methanol at the end of the run.
4 Exam?le 2A
Polymerization was initiated by adding diethyl
6 aluminum chloride in hexane as catalyst to the chilled
7 stirring feed and then dripping in a dilute solution of
8 chlorine in methyl chloride as co-initiator to produce
; 9 the cesired amount of polvmer. The diethyl aluminum
10 chloride (DEAC) was added as a 22.5% solution in hexane and
11 the chlorine was dripped in as a 0.036% solution in methvl
12 chloride-
13 In this control run containing no slurry stab-
14 ilizer, 5 ml. of 22.5% DEAC were added to 230 g. of feed
lS in the 500 ml. flask anc then 3.5 ml. of the 0.03G~ C12
16 solution was dripped in slowly to initiate polymerization.
17 A slurry formed 2nd then ~gglomer2ted into a ball directly
18 in the reactor. .~ 21~ conversion o- monomers to butyl was
;9 achieved to ?roduce a butyl polymer with ~v = 285,000 and
INOPO = 8.2.
21 ~xam?le 2B
22 Tn this ~un, 10 g. o' the 0.5% solution o~ S-3
23 in meth.ylene chloride was added to 230 g. of feed in the
24 500 ml. flask to give a feed blend con'aining 0.2~ stabil-
25 izer on monomers. Then 5 ml. of 22.5% DEAC was added
26 followed by drippins in 3 ml. of the 0.036% C12 solution
27 to produce the polymer. In this run, a stable, milky
28 appearing slurry was formed which showed no tendency to
-- 28
1 agglomerate durins polymerization or after ~uenchins. A
2 20% conversion of monomers to butvl poly~er was achieved.
3 The polymer was recovered bv allowing the methyl chloride
4 to flash off in the hood and then washing the deposited
5 polymer in methanol. The diene/styrene block copolymer
6 was an effective slurry stabilizer at -80C. ~lnfortun-
7 a.ely, the polymer recovered from this run contained 60%
8 gel. Apoarently, the diene copolymer chain segment part-
9 icipates in the polymerization to cause gel formation.
10 Hence, while the diene/stvrene block copolymer was an effec-
11 tive slurry stabilizer, it would not normally be desirable
12 to have it present in the reactor during polymerization.
13 It is appzrently the isoprene moieties in the diene chain
14 which partcipate in the polymerization and cause gel for-
15 mation.
16 The results of experiments of ~xample 2A and
17 2~ do show though, that a dlene/styrene block polvmer
18 contalning 27 mole ~ styrene can function as a slurry
19 stabilizer for a butyl slur-y in methyl chloriae, bu~ only
20 if added after completion OL ?olymeriz-tion.
21 Examole 3
22 A series of batch dry box runs, very similar
23 to those described in Example 2, was run to evaluate two
24 other diene/styrene block copolymers ~s butyl slurry
25 stabilizers. The block copolymers evaluated were desig-
26 nated as Stabilizers "S-4" and "5-5":
27 S-4 - A diene/stvrene block copolymer with an isoprene/
28 butadiene diene copolymer block and a pure styrene
114~'Z8~
29
1 block with an Mn of 82,000~ The overall polymer com-
2 positlon was 36 mole % styrene, 46 mole % isoprene
3 and 18 mole ~ butadiene.
4 S-5 - A diene/styrene block copolymer with an iscprene/
butadiene copolymer block and a pure styrene block
6 with an ~n o' 65,000. The overall polvmer composi-
7 tion was 51 mole % styrene, 39 mole % lsoprene, and
8 10 mole % butadlene.
9 The dlene/styrene bloc~ copolvmers were dlssolved
10 in methyl chloride as 1% solutions for addition to the
11 reactions. A feed blend was prepared as in the previous
12 examples and aliquots were placed into the 500 ml. reac-
13 tors fo- polymerizatlon runs. Eac~ run was conduc,ed wlth
14 230 c. of feed contalning 24.25 grams isobutylene, 0.75 g.
15 lsoprene and 205 g. methvl chlorlae. The slur-y stabili-
16 zer was a~ded at 2% on monomers. Polymerizations were
17 started at -83C and kept colder thzn -80C 2S in Example
18 2. Polymerization was initiated bv addins 1 ml. of 10
19 triethyl aluminum (TEAL) in hexane and then dripping in
20 1% TiC14 in methyl chloride to form the cataivst system
21 and produce the deslred amount of polymer.
22 In a control run with no stabilizer, 1 ml. of
23 10% TEAL in hexane was added and 15 ml. of 1~ TiC14 was
24 cripped in to give 61% conversion o' monomers to polymer
25 wi'h an ~v of 317,000 and an I~OPO of 10.3. A muddy brown
26 slurry formed and immediately agglomerated to give a clear
27 brown liquld contalnlng a large mass of agglomerated poly-
28 mer.
8~
- 33 -
1 In the run with S-4 as the slurry stabilizer,
2 1 ml. of 10% TFAL in hexane and 15 ml. of 1% TlC14 was
3 added to give 64~ conversion of monomers to polymer while
4 in another run with S-5 as the slurrv stabilizer, 15 ml.
5 of 1~ TiC14 was added with 1 ml. o 10~ TEAL in hexane
6 to give 62~ conversion of monomers ~o polymer. Both these
7 polymers had a high gel content and so could not be char-
8 acterized. In both these runs, 2 mudcv brown milk formed
9 and then slowly partially agglomerated. The slurries pro-
10 duced were much more stable th~n the control, but d~d not
11 persist as a fine stable milk.
12 These runs agair show that diene/styrene block
13 copolyme-s can ~unction as slurry stabilizers ~or a butyl
14 slurry in methyl chloride, but th2t diene cha ns containing
15 isoprene moieties cannot be present in the reactor during
16 Dolymerization without resulting in sel formation. But
17 these stabilizers are suitable for use when addeà to
18 reactor effluent.
19 _xample 4
A set of batch dry box runs verv similar to
21 those described in Examples 2 and 3 were run to evaluate
22 a pre'ormed diene/s~yrene block copolymer stabilizer in
23 which the diene block consisted entirely of butadiene.
24 The block copolymer W25 prep2red by anionic polvmerization
25 using n-butyl lithium catalysis anc was designated as S-6.
26 The block copolymer had the following analyses: ~4.3 mole
27 % butadiene, 55.7 mole ~ styrene [Mn=6400; Mw=9200 by GPC
28 (gel pe_meation chromotography)~.
4~ ~ 8
_ 31 _
1 In conducting the à~y box evaluations, a feed
2 blend was pre?2red as in the previous examples and ali-
3 quots were placed in'o the 500 ml. reactors for polvmer-
4 ization runs. Each run was conduc.ed with 460 g. of
5 feed containing 48.5 grams isobu~ylene, 1.5 grams isoprene
6 anà 410 sræ~s methyl chloride. The larger feed charge
7 was used sc that the 500 ml. ,lask was nearly full and
8 the arv wall area on which -ubber could plate out was
9 minimize~. In the control Run A, no slur-v stabilizer
~0 was used whereas in Run 3 2.0 grams of block copolyme-
11 S-6 was adaea to the feed ana stirred cold for abou~ 25
__
12 minutes to completely dissolve the block copolymer in the
13 'eed. ?oly~erization was inltiate~ by dri?ping a 0.18%
14 solut~or. o ~lC13 i~ met:r.vl chloride i..~o the stirred
15 _eed maintainec at a tempe-atu-e o -97 to -93~C. Af,er
16 suf ic`ient polymer had been formed, the polymerization
17 was quenchec with cold MIBK and then transferred to a
18 hood where it was allowed to warm slowly with stirring
19 and cold MIBK was added as the methyl chloride flashed
20 off. A total o' 200 ml. of MIB~ was aaced and slurry
21 stabilitv was evaluated as in the prior examples.
22 The slur-y procuced in Run B with 4~ slurry
23 stabilizer on monomers was markedly more stable than
24 that produceà in control Run A with no stabilizer. In
25 the control run much rubber deposi,ed on tne reactor
26 walls and stirrer durina polymerization and many ag~lo-
27 merates were present as the reactor was trar.s'erred cold
28 to the hood. It agglomerated very rapidly as it warmed
.. .
: - 3~ -
1 in the hood and was already a clear liquid with a larse
2 agalomer2~ed mass of rubber by the time it reached -85C -
3 u-ther s,irring was impossible. In Run B with 4~ S-6
4 on monomers as stabilizer, a stable thic~ milk formed with
5 no lating out on wetted reactor surfaces. It remained
6 stable durins warming anc at room temperature was a fine
7 dispe-sior. Os butyl rubber in ~5IBX. Average ?article
8 size was _2mm. The slurry settled slowly when stirring
9 was s'cpped but easily redispersed when stirrina was
10 s.a-ted zgain. Clearly the butaGiene/styrene block co-
11 poll~er is an ef.ective slurrv stabilizer ana producec
12 a stable slurry ',hat could survive warming to room tempe--
13 ature without m2ssive asglomerat on.
14 The polymer ~-om ~un 3 W2S recovered bv allowins
15 the slurry to settle -and decanting off the MI3K and then
16 reslurrying twice in acetone and decanting to remove as
17 much of the soluble bloc~ copolymer stabili~er as possi-
18 ble. A stable dispersion resulted during .he 2cetone
19 washes. Methanol was then added to the remaining rubber
20 and it immediately agglomerated into a mass which was
21 washed and then vacuum oven dried to recover 15.79 grams
22 of an opaque, white tough rubbery butyl polymer with an
23 ~AV of l,154,000 and an INOPO of 9.7. It was completely
24 soluble and contained no gel. Polymer recovered from the
25 control Run A was similar in appearance with an ~v of
26 l,130,000 and an INO~O of 8.3.
27 The .~IBK and acetone decants lrom Run B were
28 combined and evapora~ed to concentrate the extracted
:, .
1~ 8~
_ ~3 -
1 block copolymer which W2S recovered by adding methanol
2 to precipitate it as a soft mass which was fil~ered out
3 and then vacuum crieà to recover 1.56 g. of s~yrene/
4 butadiene block copolyme- with similar inspections to
5 ~he added copolymer. Only 79% of the copol~er stabilizer
6 was ex,racted by this procedure with the rest being con-
7 tained in the butvl as shown by the higher INO~O o' the
8 stabilized pclymer.
9 These runs show that a butaciene st-yrene bloc~
10 copolymer is an effective stabilizer ~or a butyl slurry
11 in methyl chloride and it can be present durins pol~er-
12 ization withoul causin~ gel or adverselv ~. ectins .he
13 butyl pol~er produced.
14 Example 4
A batch dry box run very similar to those o~
16 Examples 2 to 4 were run to evaluate a functional grou~
17 containing polvstyrene as a stabilizer for a butyl slurry
18 in methyi chloride. The functional polystyrene was a low
19 molecular weisht anionic polystyrene capped with vinyl
20 benzyl chloride and had the following structure:
21 - ~CH2 - CH ~ 2 ~ CH = C~2
22
23 The end functional group is cationically copoly-
24 merizable wi,h isobutylene-isoprene and can become incor-
25 porated into a growing butyl chain during pol~merization
26 to yield a butyl molecule containing one or more pencant
27 lvophilic polystyrene chains thereby to act as a slurry
28 stabilizer. ThR vinyl benzyl chloride-capped polystvrene
,,:
~4~
_ 3~, _
levaluated as a functional lyophilic stabilizer precursor
2and desisnated as S-7 in this run had the Collowing analvsis:
3Mv = 1~,800; ~n = 10,960; Mw/Mn = 1.41; Taylor I2 No. = 2.15
4 The batch polvmerization to evalu~te the s~abili-
5 zer was run in a 500 ml. round bottom flas~ as in the pre-
6vious example, bu. 2. typical butyl Dolymeriza~ion temper-
7 ature and using AlC13 as the catalyst. Also, a feed charse
8 o_ ~60 c. was used so that the ~00 ml. flask was nearly
9 full and .he dry wzll area on which rubber coulà ?late out
10 W2S minimized. The reed charged to .he flask was 48.5 g.
11 isobu.ylene, 1.5 g. isoprene anc 410 g. methyl clhloride.
12 Two grams o' the S-/ stabilizer precursor was addec to
13 the feed. The polysty~ene was added as 2 dry powder and
14 stirred in cold. It was of sucn low molecular weight
15 that it dissolved within a few seconds. No stabilizer
16 ~recursor was added in a control run. A 0.1396 solution
17 Of AlC13 in methyl chloride was added dropwise to the
18 stirred chilled feed to produce polymer as usual. Poly-
19 merization was begun when the stirred feed reached -97C
20 2nd catalyst ra~e was controlled to maintain reactor
21 tempera' ure below -90C. The polymerization was ~uenched
22 with cold MIBX and then transferred to the hood where it
23 W2S allowed to warm slowly with stirring as in Example 1,
24 and cold MIgK was added as the methyl chloride flashed
25 off. A total of 200 ml. of MIBK was added. Slurry stab-
26 ili.y was evaluated as in prior examples.
27 The slurrv produced in the run o, this example
28 with 496 sta~ilizer precursor on monomer was markedly more
.' .
`'
lstable than that producec in the control run with no
2 stabilizer precursor. A lot of polymer deposited on the
3 reactor walls and stirrer du~ing ~he control run and the
4 slurry cont2ined many visible agglomerates when examined
5 cold in the dry box. It 2sglomerated auite rzpidlv during
6 wa-ming in the hood anc was alre2dy a clea- liquid with
7 large asglomerates by ,he time it h2d warmed to -80C.
8 ~t room temperature .he rubber W25 one solid mass in clea_
9 ~IBK. In the run of this example with ~ S-7 o~ monomers
0 2S S tabilizer the slurry 'ormed as a nice s.2ble thick milk
11 with no visible par~icles and no platinc out on wetted
12reactor surfaces. It remained stable during warming and
13 at rcom temperature was still ~ very fine stable disper-
14 sion of butyl rubber particles in the MIB:~. Consiaerable
15 particle growth h2d occurred during warming and the slurry
16 would settle slowly when stirring was stopped, but easily
17 redispersed when stirring was started again. The slurry
18 particles were fine specks of rubber much less than 1 mm
19 in size. Clearly the functional polystvrene is an effec-
20 tive slurry stabilizer precursor and results in the in
21 si~u formation of 2 copolymer st2bilizer that produces a
22 stable slurry which survived warming to room temperature
23 without massive agglomeration.
24 In order to determine how much of the functional
25 polystyrene had reac,ed durino polymerization and become
26 incorporated into the butyl, the unreacted polystyrene W25
27 ex~racted 2nd recovered curing polymer workup. The slurry
28 was allowed to settle and the clear MIBR layer containing
-
1~L4~
- ~6 -
1 the dissolved unreacted polystyrene was decanted of.. The
2 slurry W25 then reslurried in 300 ml. OL acetone which is
3 a sood solvent ror the polystyrene and asain allowed to
4 se~tle and the clear acetone layer containins additional
5 dissolvec polystyrene was decan_ed and combined with the
6 decan.ed MIBK. This was -epeated twice to extract all
/ the polvstvrene not attached to the but,vl. The slurry
8 showec no tendency to aGglomerate curing this treatment.
g It redispersed rapidly when s'irred in the acetone to fine
10 p2r,icles less than l mm in size and settlec slowly. The
incorporated stabilizer had formed an effective barrier
asainst agclomeration and was maintaining the slurry stable
13as discrete particles. After the final decanting, methanol,
14 a non-solvent for polystyrene, was added to the rubber slurry
15 to agglomerate the particles sufficiently to allow recovery
16 The combined MIBK and acetone extracts were evaporated to
17 concen,rate the dissolved functional polystyrene which was
18 then recovered by adding methanol to precipitate it and then
19 filterins. 1.60 g. of functional polystyrene were recovered
20 indicating that 0.4 g. had reacted and combined with the
21 butyl. The recovered polystyrene had an ~v of 15,900 and
22 a TAYLOR I2 No. of 1.'5 showing it was similzr to the
23 charged material but slightly less functional. 36.73 g.
24 of butyl rubber were recovered with an Mv of 589,000 and
25 ~NOPO of 9.1. Thus 73,5% conversion of monomers to butvl
26 had been achieved and 20~ of the functional polvstyrene
27 had become incorporated in the rubber in non-extractable
28 form. Material balance thus indicates the but~l contained
Z~3~
_ ~7 -
1 1.1% polystyrene by weight. This was confirmed by U.V.
2 and N~ analvses. This work shows that a functional poly-
3 styrene can be che~icaliy bonded with a portion cc butyl
4 durina polymerization to effectively stabilize the re-
5 sulting slurry.
6 E~æ~ple 5
7 Batch dry box runs exactly like those described
8 in ~xa~ple ~.we~e run _o evaluate other low molecular
g weight polystvrenes 25 slur~v stabilizer precu-sors. An
10 anionically polymerized polystyrene capped with methallyl
11 chloride designated as S-8 was usec as a stabilizer pre-
12 cursor in .his example. ~his functional polystyrene had
13 the followins structure:
~ ~ CH - C )~ CH2 - C = CH2
16 and contained an end functional group capable o' becoming
17 incorporated into a growing butyl chain. This functional
18 polystyrene had the following analyses:
19 Mv = 13,300; Mn = 9,260; Mw/Mn = 1.41i INOPO = 2.96.
A comparative experiment was carried out using
21 an anionically pol~erized polysty-ene quenched with
22 methanol, and therefore, nonfunctional. This polystvrene
23 had the following structure:
24 ~ CH - CH ~ CH2 - C~
26 and did not contain a func.ional group active in cationic
27 polymerization. It had the following analyses:
2g Mv = 11,200; Mn = 9,170; Mw/Mn = 1.22; TAYLOR I2 =
114~2~3
- 38 -
1 The batch pol~erizations were run exactly 2S
2de5cribed in ~xample 4~ and ~he same worku procedures were
3used. The ?olys,yrenes were added ~o ,he _eed aliquots in
4 the 500 ml. reactors as dry ?owders and dissolved within
5a few seconcs. The ?olystyrene level was 4~ on monomers.
6 ~s described ?reviously, unstable slur-ies which
7csglomer2~ec rapidly znd completely dur ng warmup ~esulted
8 from the control runs with no stabilizer. A stable slurry
9 which survived warming to room temperature resulted from
10 the run of this example with the methallyl chloride capped
11 polystyrene, S-8, as stabilizer precursor. Some growth
12 occurred durins warming, but ~he final slurry particles
3 were all <0.1" in diameter. Of the 2.0 g. of polystyrene
14 charged, 1.66 g. were recovered by the extraction proce-
15 dure indicating 0.3~ g. had become incorporated in non-
16 extractable form into the butyl. 43.71 g. of butyl were
17 produced indicating an 87.4% conversion of monomers to
18 butyl and a 17% incorporation of he functional polystyrene.
19 The slurry was stabilized by incorporation of about 0.4%
20 incorporated functional polystyrene. The recovered poly-
21 styrene was essentially identical to the charged material:
22 Mv = lL,300; INOPO = 2.88. The butyl had an Mv = 628,500
23 and INOPO = 9.~.
24 ~he slurry which resulted from the comparative
25 run with the non-functional polystyrene as s'abilizer was
26 quite unstable but better than the control. It agglomer-
27 ated quic~ly during warmup and at room temperature the
28 rubber was in larger chunks ranging from 1/4" to 1". Of
- - 39 -
;. lthe 2.0 g. of polvstyrene ch2rsed, l.99 g. were recovered
2 unchan~ed by the extraction proce~u-e indica,ing tha. none
3 had become incorporated. 37.30 g. of butvl were recovered
4showing ~hat 74.6~ conversion of monomers to bu~vl had been
5achieved.
6 These experiments show th~, a non-~unctionzl
7polvs~yrene does not incorpora.e in~o ,he butvl durins
8polymerization and is not an effective stabilizer precursor.
9The work l~rther shows that a methallyl chloride capped ?oly-
10styrene i5 an effective stabilizer precursor with only 0.4%
llincorpor2tion into the rubber imparting very good stability.
12However, ,he methallvl chloride capped polystyrene is not as
- 13readily incorporated into the polymerizing butyl as was
14the vinyl-benzyl chloride capped polystvrene, under the
15conditions used in rxam?le 4A.
16Example 6
~7 ~nother series of batch dry box polymeriza,ion
gwas run exactly like those described in Examples 4A and 5
gexcept at a very warm polymerization temperature to prove
20that stabilized slurries would permit polymerization at
; 21higher temperatures. In this series of drv box runs poly-
22merization was initiated at a reactor temperatu~e o,~ -47C
23and the catalyst rate was controlled to keep reactor tem-
24perature below -40C. The functional polystyrenes used
2Sas stabilizer precursors were:
26S-9 in run 6(a) was a vinyl benzyl chloride capped anionic
27polystyrene wi_h the following analvses: ~v = 26,930;
.Mn = ~1,790; .Mw/~n = 1.39; TAYLOR I2 ~ = 1.10.
B~
- 40 -
1 S-10 in ~un 6(b) was a vinyl benzyl chloride c2~pec anionic
2 polystv-ene '"i.h the ollowina analyses: ~5v = 50,500
3 Mn = 34,940; Mw/Mn = 1.~6; TAYI,OR I2 r;o. = 0.66.
4 The stabilizer precu~sors were added to the ~eed
5 aliquo's 2S d-y powciers and dissolvec 21mos. instc,,tly as
6 descri;bea e2rlier. The stabilizer ?recursc-s were adGed
at only 1% on monomers in .hese runs~ The feed blend was
8 as described above in Example 2 and 0.15% AlC13 in methyl
9 chloride was used as the catalyst. In a control run with
10 no stabilizer, 10.5 ml. of catalyst were added to give
11 essenti211y complete conversion of monomers to pol,vmer
12 with an Mv of 150,000 and INOPO of 5.1. The slurr was
13 very uns.able and all of the butyl agglomerated into 2
14 large mass at once. In run 6(a) with S-9 as the stabilizer
15 precursor, 17 ml. of catalyst was used to give 83.5% con-
version of monomers to polymer with an Mv of 67,000 and
17 INOPO of 6.3. The slurry was 2 very stable thick milX and
18 survived warmins to room temper2ture and replacement of
19 the methyl chloride with MIB~ without agglomeration. Slurry
20particle size was much less than 0.1 mm. In run 6(b) with
S-10 as the stabilizer precursor, 16 ml. of catalyst gave
22 82.5% conversion of monomers to polvmer wi1:h an ~v of
23 67,000 and INOPO of 6.2. Again the slurry was a very
24stable thick milk which survived warm.ing to room temper-
25ature wi~h no agglomeration. Material balance calcula-
26 .ions and polymer analyses showed that 0.58~ by weight o~
27polystyrene h2d become incor?orated in non-ex_rac.able
28form in rur. 6 (2) and 0.64Çs o' ?olystyrene in run 6(b).
2~6
- 41 -
1Thus, good incorporation o' the Cuncl_ional ?olyslyrene
2 was achieved and excelient slurrv s~abilitv was produced.
3 Photographs taken OL the slu~ries a, rocm _empera~u-e in
4~ X showed the excellent stable slurries which were
5 achieved in .hese runs~ The cont-ol WGS a solid mass Oc
6 butyl in clear ~.IB-~; both stabilized slurries appear as
7 stable fine dispersions o' the butyl particles in MIBK.
8 These experiments shGw that ~unctional poly-
9 styrenes are very ef.ective stabilizer precursors for
10 butyl slurries and that at low (and thus economical) in-
11 corporation levels (~0.5~ on rubber) very stable slurries
12 can be achieved. Ths use of these stabilizer precursors
` 13 and subsequent in situ forma~ion of stabilizer would per-
:, .
14 mit polymerization at much warmer temperatures than can
15 now be used and would permit recovery of refrigeration
16 enercy from the cold reaction product by employing heat
17 exchange with warm reactor feed.
18 Example 7
19 This example illustrates the use of a block
20 copolymer formed in situ by a chain transfer or co-catalytic
21 initiation mechanism. A chlorine-capped polystyrene was
22prepared by racical polymerization o' styrene in carbon
23 tet_achloride at 70C using AZBN (azobisisobutyronitrile)
24as the initiator. The initial svtrene concentration was
25 43.5~ by weight and the polymeriz2'ion was carried out to
2623.5~ bv weight conversion of sty-ene. A chlorine-capped
27?olvstyre..e with a viscosity ave~age molecular weisht of
28
r I
4i~ ~
16,700 was recovered and had the followins structure:
CC13 ~ CH2 - CH ~ C~.2 - CH - Cl
3 ~ ~ J.~ ~
4 l~ was evalua.ed as a slurry stabilizer precur-
5 sor according to ~he method of rxamole 4 and yielded an
6 excelle~t stable isobutylene-isoprene butyl rubber slurry
7 which survived warming to room tem?er2ture in ~IBK as a
8 very 'ine stable slurry. A comparative conLrol polymer-
9 ization reaction containing no stabilizer agglomerated
10 completely.
11 Examole 8
12 This examole is another illustration of the use
13 of a block copolymer formed in situ by a chain transfer
14 cr co-catalytic initiation meChanism.
A sty~ene-vinyl benzyl chloride copoiymer was
16 prepared by radical polymerization in toluene at 80~C
17 using AZBN as the initiator. The feed charge was 44.3~
18 by weight monomers in toluene with 2% by weight of vinyl
19 benzyl chloride on styrene, and the pol,vmerization was
20 carried to 40.5% by weight conversion. The styrene/vinyl
21 benzvl chloride copolymer wi-~h a viscosit~ average mole-
22 cular weisht of 35,200 was recovered.
23 It was evaluated as a slurry stabilizer precur-
24 sor according to the method of Examole 4A and yielded an
25 excellent stable isobutylene-isoprene butyl rubber slurry
26 which survived warmina to room tempera.ure in .~IBK as a
27 very _ine stable slurry. A control pol~erization reaction
28 co~tainin5 no s~abilize_ agslome_ated comple.ely.
- 4 3-
1 Exam~le 9
2 This example is an illustra~ion of a block co?oly-
3 mer 'ormed in-situ bv a chain transfe- o- cocatalytic
4 initi2tion mechanism as a slurry stabilizer fo- a ?olylso-
5 butylene slurry in methyl chloride. For this series of
`~ 6 dry box runs, a fee~ blend consisting o' 10.9~ isobutylene
7 in methyl chloride was prepared and aliquots were charged
8 into the 500 ml. reactors 'or individual polymerization runs.
9 Each run was conducted with 460 grams of feed consisting of
10 50 grams of isobutylene and 410 grams of methyl chlorlde.
11 Polymerizations were initiated at a tem?erature of -45~C
12 by dripping in a 0.14% AlC13 in methyl chloride catalyst
13 solution into the stirred feea maintained at a temperature
14 of -45 ~ -40C. After sufficient poly~er had been formed,
15 the polymerizatio~ was quenched with cold MIBX and trans-
16 ferred to a hood where it was allowed to warm 5towly with
17 stirring and cold MIBK was added as the methyl chloride
18 flashed off as in the prior examples.
19 Run 9B was a control run containing no stabilizer.
20 0.5 grams of stabilizer precursor were added to the feed
21 'or Runs 9A and 9C and stirred in to dissolve the stabil-
22 izer precursor before polymerization, ,he stabilizer level
23 was 1% on the isobutvlene.
24 The stabilizer precursor used in Run 9A was a
25 chlorlne-capped polvstyrene prepared bv radical polvmeriza-
26 tion o_ styrene in carbon tetrachloride at 70C using ~.~BN
27 as the initiator. The initial sty-ene concentration was
28 6;-2~ cn~ polymerization was carriec to 40.1~ con~ersion of
i~ 36
- 44 -
1 .he s "vrene ~he chlo ine-cap?ec ?olvs.yrene had a vis-
2cositv 2ve~ase molecular weish, of 29,340, contained 2 27%
3chlorine 2n~ h~d the following s,ruc.ure
4 CC13 - ~ CH2 - CH ~ - C~2 - C H - Cl
~ @
6 The stabilizer precursor used in Run 9C W25 a stvrene/
;7 vinyl benzyl chloride copolymer prepared by radical poly-
8 merization in ,oluene at 80~C usins AZBN as ,he initiator
9 The .eed charge W25 54 4~ monomers in toluene with 0 81~
10 by weight vinyl benzyl chloride on styrene and polymeri-
11 zatlon was carried to 46 1% conversion The s.yrene/vinyl
- 12 benzyl chloride copolymer had a viscosi~y average weisnt
13 o' 40,150 and contained 0 21~ chlorine due to the incor-
14 porated vinyl benzyl chlorice Its structure was as
15 shown hereinabove (on-Pg. 13 Lines 6-8)
16 In the control run with no stabilizer (9B), the
17 polyisobutylene completely agglomerated during polymeriza-
18 tion and was removed from the dry box as a large mass of
19 polymer in clear liauid--stirrins was impossible 49 25
20 srams of polyisobutylene were recovered wit~ a viscositv
21 average molecular weight o~ 92,000
22 The runs containing in-situ formed stabilizers,
23 9A and 9C, both yielded fine stable milky dispersions which
24 survived warming to warm temperature as line stable dis-
25 persions with most par.icles too small to be visible LO
26 the naked eve Mic-oscopic examination o_ the dispersions
27 in MI3K at room _emperature showed the par.icles in both
28 were mostlv below l~ in diame.er In Run 9A, 2~ 70 srams
8~
- 45 -
1 of ~olvisobu'ylene o- ~lv - 79,200 were recovere~ ~ihile in
2 Run 9C, 3Q.l/ ~rams of polvisobutvlene o~ Iv - 58,900 were
3 -ecovered. The polyisobutylene producec in Run 9A con-
4 tzined 0.63~ unext~actable polvstyrene while ~ha. in Run
5 9C contained 0.64% unextractable polys~y-ene.
This run shows that slurry stabilizers are effec-
7 tive at stab-'lizing polyisobutylene slurries in methyl
8 chloride just as wi.h butyl rubber slurries. As little as
9 0.63% bound polystyrene on the polyisobutylene is capable
10 Of preventina agglomeration of the polyisobutylene slur-y
11 and allowing it to survive as a stable slurry up to room
.,
12 tem~erature so that the refriseration energy could be
13 recovered from the reactor effluent by heat exchange with
14 warm reactor ~~eed.
15 Example lO
16 This example is an illustration that the same
17 stabilizers which ef ectively stabilize a butyl slurrv in
18 methyl chloride are also effective stabilizers for a butyl
19 slurry in methylene chloride. For this series of dry box
20 runs a feed blend of isobutylene and isoprene in methylene
21 chloride ~-as prepared and divided in'o aliauo.s Ifor ~he
22 individual polymerization runs. A 600 sram aliquot of
23 this feed blend was charged to the 500 ml. reactors as n
24 ~he previous examples for polymerization rur.s. The feed
25 'or each run then was 97.0 grams isobu.ylene
26 3.Q arams isoprene
27 SoO.0 ar~ms me-~vlene chloride
28
B~
- 46 -
; 1 ~olvmeriz2tion ~as initiated bv dri?ping in a 0.20~ ca.a-; 2 lyst soiution o lCl3 in me.hylene chlorice in.o the
3 stirred feed at a tempçrature of -97C and maint2ining
4 reactor temperature between -97 and -92~C. After suf-
5 ficient polymer had formed the polyme-ization ~as quenched
6 with lO ml. of cold .~IBK and then transferred to a hood
r 7 and allowed to warm with slow stirring. Since methylene
8 chloride boils at 39.8C it did not boil o'f as the slurry
9 warmed and so it was not necessary .o add more MIBK. The
10 fina1 slurry at room temperature was still in the methy-
11 lene chloride pol,vmerization diluent.
12 Run lOA was a control run containins no stabili-
13 zer. Run lOB contained l.0 grams of a chlorine-capped
14 polystyrene (1~ on monomers) dissolved in the feed prior
15 to initiating polymerization and Run lOC contained ~.0
16 grams of a vinyl benzyl chloride-capped polystyrene (~%
17 on monomers) dissolved into the feed prior to initiating
18 polymerization. The chlorine-capped polystyrene used as
19 a stabilizer precursor in Run lOB was prepared by radical
20 polymerization of styrene in carbon tet~achloriàe at 70~C
21 usina AZ8N as the initiator. The initial stvrene concen-
22 tration was 80~ and polymerization was carried to ~9.9~
23 conversion. This chlorine-capped polystyrene hac a vis-
- 24 cosity averase molecular weight of 5~,010 anc contained
25 2.~.7~ chlorine.
26 The VBC-capped polystyrene used as a stabilize~
27 precursor in Run lOC was prep2red by anionic polymeriza-
2~
'
32B6
;, - 4 7 -
1 tion usins n-butyl lithium ca'alysis. I' had an Mn 0c
2 34,100 and ~w 96,300.
3 n the control polymerization (Run lOA with no
4added st2bilizer) a coarse slurry Cormec in the reactor
5with the butyl sluxry particles showing a strong tendency
6to rise to the surface and agglomerate and plate out on
7the reactor walls and stirxer. When the reactor was trans-
8~erred to the hood, the butyl rubber all rose to the sur-
9Lace and agglomerated into a mass Oc polymer so that
0stirring was impossible. However as the reactor warmed,
11the butvl rubber mass appearéd to imbibe the diluent phase
12(methylene chloride and unreacted monomers) and softened
13and ex?anded to nearly Lill the entire reactor volume.
The diluent containing polymer mass became soLt enough that
15stirring could be resumed, but the reactor contents were
an extremelv viscous gel-like mass o~ highly diluent swollen
17polymer. When stirring was sto?ped 2t room tem~erature,
18the reactor W2S almost entixely filled with a viscous gel-
19like mass OC ~iluent swollen polymer with only a small
20amount of a clear thin licuid phase (methylene chloride)
210n the top. When acetone was stirred in, the rubber mass
22immediately exuded the diluent ?hase to Lorm a normal pre-
23cipitated mass of butvl rubber which was removed and washed
- 24in alcohol prior to vacuum oven drying. 35.92 grams OL
25butyl rubber o, ~1v 273,000 were recovered (the relatively
26 low molecular weight was probablv due to poisons present
27in ~he rethylene chloride used). ~he UnS _able slurrv in
28methvlene chloride W2S quite di~-erer._ ~ror tha. in methyl
36
- 4~ -
1 cnioride because the me hylene chlcrice is much more sclu-
.. .. . . .. .. ... . . . . . ..
2 ble in .he rubber but the unslabilized slur-y in methy-
3 lene chloride i5 also badlv foulins znd could not be cooled
4 e.fectively in the reactor or heat exchanged with incoming
eed to recover -e rigerant energy.
6 In Run lOB with 1~ of the chlorine-capped poly-
7 styrer,e dissolved in the feed as sta~ilizer precursor, a
8 stzble slightly yellowish milky slurry formed in the reac-
9 tor with the yellowish tint disappearing when the MIBK
10 quench was added. The milk was nice and fluid with little
11 tendency to rise or plate out. It was transferred to the
12 hood as a fine stable milky dispersion. As it was allowed
13 to wzrm with stirring, it remained as a stable thin ~luid
14 which wzs easily stirred but changed in appearance becoming
15 more of a translucent emulsion in appearance than an opaque
16 milky dispersion. At -oom tempera~ure it remained as a
17 nice fluid stable emulsion which could be ?umped or heat
18 exchanged easily. It did not se?arate when stirring was
19 stoppeà. When acetone was stirred in, the emulsion changeà
20 in appearance and became a fine particulate dis?ersion of
21 butyl -ubber pa-ticles of size rzngina ~rom invisible to
22 ~ l ~. The dis?ersion was fluid and s~able while stirring.
23 When stirring was stopped the butyl particles slowly -ose
24 to leave z sligh~ly cloudv liquid layer a~ the bottom, but
25 easil~ redispersed when stirring wzs resumed. The rubber
26 wzs recovered bv drawing off the bot,om methylene chloride~
27 acetone laver znd reslurrvina the rubber ?a_~icles twice
28 in acelone ~o ext~zc. any uncombineG ?olvs~vrene. The
114~2~6
1 q
lrubber p2rticles reslu-ried easily in the acetone to
2 form a stable 2ispersion which set'led slowly when stir-
3 r ns was s.opped. The extracted slurry ?articles were
4 aused to agglomerate into a mass by adding methanol and
5 ,hen washed and vacuum oven dried to recover 39.65 grams
6 of butyl rubber OL Mv 217,800. The butyl rubber contained
7 0.46% unex.ractable polystyrene. This experiment shows
8 that small and economic amounts of a stabilizer are able
9 to stabilize a butyl rubber slurry in methylene chloride
10 to realize all of the benefits previously recited for
11 stabilized butyl rubber slurries in methyl chloride.
12 In Run lOC with 4~ of the vinyl benzyl chloride-
13 capped polystyrene dissolved in the -eed as stabilizer
14 precursor the behavior w2s very much as in Run lOB. A
5 stable slurry was formed and a fluid easily stirred system
16 persisted during warming as contrastedto the unstable fouling
17 viscous gel-like system which -ormed in .he cont-ol poly-
18 merization containing no stabilizers. ~owever, the final
19 dispersion of butvl rubber in ,he methyléne chloride/acetone
20 mixture of Run lOC w2s somewhat coarser th2n that of ~un
21 10~ des?ite the la~ger amount of s~abilizer precursor used.
22 The chlorine-c2ppe~ polystyrene is e~fec.ive 2t lower
23 concentrations than is the vinyl benzyl chloride ca?ped
24 polystyrene. 31.66 grams of butyl rubber of ~v = 288,200
25 were ~ecovered from ,his run. The r~ober contained 0.716
26 unextr2ctable pol~stvrene 2cting as ~he slurrv stcbilizer.
27 This experiment shows ~at '.he stabilize-s which are e~fec-
28 tive _or producina stable butyl rubber or polyisobutylene
- 50 -
lslurries in methyl chloride are also ef_ec.ive for pro-
2ducing stable butyl rubber or polyisobutylene slurries
3in methylene chloride.
4Exam~le 11
The previous examples of ~he ef~ectiveness of
6sl~rry st2bilizers have all been batch polymerizations in
7a dry box, whereas commercially produced butvl rubber and
8polyisobutylene are normally proaucec in continuous reac-
9to-s in which the slurry is pumped around through hea~
lOexchznce tubes to remove the heat of polym.erization. As
a further demonstrat-on of the practical signi~icznce of
this invention we have conducted experiments in a small
pilot Lnit con~inuous reactor to illustrate the effective-,
4ness of slurry stabilizers under continuous production
5conditions. These experiments were cor.ducted in 2 one gallon
continuous stirred dra~t tube reac~or which is a small
7~-o~otype of typical commercial butyl reactors. ~he
greactor was a modified, draCt-tube containing well-stirred
gtank type reactor of nominal one sallon capacity and con-
0taining 2.86 sc~uare feet of heat ,-~nsfer surface to remove
the heat of polymerization and maintain the reactor at
2polymerization temperature. Up to ~our feea and catalvst
3streams could be chilled and meterea continuouslv in.o
4,he reac~or and the reactor effluent was con'~inuously
over lowed through a 3/~ inch line intc chilled produc_
6slu-_v receivers or quenchi~c and ecoverv. Reactor
27temperatire wzs maintained and controlled bv circulating
2~ 2 hea~ ' ans-er flLid 2t a controlled temperature and
3Z~
~1 -
: `'
lrate through the reactor heat .ransLer surfaces.
2 Dreviously it has been found that small oilot
3 unit butyl reactors are not able to operate a. as high
4slurrv concentrations as the larger co~mercial -eactors
5 because of the much smaller size of the inle. and exit
6ports and hea. t-ansfer ?assages in the small ?ilot reac-
7tors. Typically one gallon pilot reactors are limited to
8operation wi.h a 12 to 14% slurry whereas 1700 gallon
9commercial reactors have operated wi',h 25 to 30~ slurries.
lONevertheless, improvements in the operation of the small
llpilot reactors are generally translatable to improvements
12in operation of the larger commercial reactors.
13 In a series of conventional runs wi_hout added
14stabilizers it w2s _ound that the one sallon pilot unit
lSbutyl reactor used in these experimen.s could operate
16SuccesSfully at a 12 to lG~ slurry concentrati on, but
17fouled out auite Tapidly when attem,pts were made to oper-
~ate at signiCicantly higher slurry concentratior.s. Steady-
lgstat~a o?erating conditions for a typical run, Exa~le l
20at an operable slurry concentration are show-n below:
21 The following three feeds were prep2red, chilled
22and metered into the sti-red and coole~ reactor.
23 Feed l was 3~% monomers, consis.irg Oc 3% isoprene
24anc 97% isobu.ylene ir. methyl chlorice cnd w2s ~ed into
2sthe bot,om draft tube of the reactor at 2 rate of 81.2
26 grams per minute.
27 Feed 2 W25 Z ~ure meThyl chloride stream and was
28 metered and chilled and Ihen blended with Feed l and fed
1~4~ 6
- ,2
1 into the reactor at a rate of 80 8 a~ams per minute
2 Feed 3 was the catalys. stream consisting of
8 0 20% AlC13 in methyl chloride and wzs fed into the top
4 annulus of the reactor at a rate of 10 0 grams per minute
Total reeds in grsms per minute to the reactor
6 then were
7 Isoprene - 0 83
8 Isobutylene - 26 77
9 Methyl Chloride - 14~ 37
AlC13 - 0 02
11 Total - 171 99
12 At steady-state the reac,or effluent ~-as a 14~
13 slurry of butyl rubber ln methyl chloride plus unreacted
14 monomers The reactor effluent consisted of
24 1 arams Butyl ~ubber
16 3 ; grams Monomers
17 144 37 srams ~Sethyl Chloride
18 0 02 arams AlC13
19 171 99 grams ~otal
Reac.or tempera'ure was cont-olled at -96C ana
21 the eCfluent was a thick yellowish slurry which turned
22 white upon quenching Con~7ersion o monomers ,o poly~er
23 W25 ~7~ and the reac.or was operatin at about the maxi-
24 r,um sus'ain2ble slurry concentr2tion Slow Couling was
25evidenced by the need for a slowly increasing tempera-
26 .ure ciffe~ence between the coolant and reacto- contents
27in order to maintain ter,?erature Lfforts to es'ablish a
28steady-state at a higher slu-ry concentra.ion resulted in
Z~
- 53 ~
1 very r2pid 'ouling out of the reactor.
2 In contrast to this introduction of a slurry
3 stabilizer has enabled st2ble steady-st2te oper2tion with
4 minimal fouling rates to be zchieved at much higher slurry
5 concentrations. _ _ _
6 Example llB
7 In this example,the vinyl ben~l chloride cap?ed
8 polystyrene of Example 10 C was used 2s the st2bilizer
9 precursor. lhis anionically polymerized polvs~yrene had
10 an ~n of 34,100 and an ~Iw of 46,300. It was cissolved in
11 methyl chloride to yield 2 4.76~ solution of the functional
12 polystyrene in methyl chloride as 2 feed to the -eactor.
-~ The feeds to the reactor for this example were:
l~i Feed 1 W25 51.1~ monomers, consisting of 2.38
15 isoprene and 97.62% iso~utylene, in methvl chloride and
16 was fed into the bottom draft tube of the reactor at a
17 r2te of 78.0 ~rams per minute.
18 Feed 2 was 4.76~ VBC-c2~pec polys,yrene in methvl
19 chloride and was metered and tnen blended with feed 1 zrd
20 fed into the reactor at a rate of 16.9 srz~s ~er minute.
21 Feed ~ was the c2.zlyst strezm consis~ing of
22 0.20~ A'C13 in methyl chlorie and was fed into ~he to?
^3 znnl~lus of the reactor 2t a rate o' 15.0 srams per minu.e.
4 Feed 4 was pu~e me hvl chloride 2nd was metered
chilled and then blended with feeas 1 and 2 and 'ed into
he -eactor a~ a rate of 26.9 srams per minute.
27
28
3~L4~ 36
r ~
1 Total feeds, in grams per minute, to the reac-
2 .or then were:
3 Isoprene - 0.95
4 Isobutylene - '8.91
M.ethyl Chlo~ide - 96.11
6 VBC-Capped Polystyrene - 0.80
7 AlC13 , - 0.03
8 Total - 136.80
9 The stabilizer precursor level was 2.0~ on mon-
10 cmers- At steady-state the reactor effl~ent was a 22/o
11 slur-y of butyl rubber in methvl chloride ~lus unreacte~
12 moncmers. The reactor effluent consisted of:
13 30.10 grams butyl rubber
1~ 9.76 grams monomers
96.11 grams methyl chlori~e
16 0 . 80 srams polystryene (?ar~lv bound to butvlj
17 0.03 grars AlC13
18 136.8
19 ~eactor tem?erature wzs controlled 2t -96C anc
20 the ef'luent WGS a thin ~ellow very 'ine dis?ersion o- butyl
21 rubber particles which turned whi_e upon quenching. Con-
22 version of monomers to bu~Il was /~.~5~ and the reactor
23 was opera,ing s~oothlv p~oducin~- a verv fluid stable slurry
24 with no evidences of anv reactor ~ouling. This is a much
25 higher slurry concent~a.ion than coulc be achievec without
26 the stabilizer present. As a fur_her cer,onstration of
27 the beneficial ef-ect of the ctabilizer, ~eed 2 to the
28 reactor was simply replaced with a pure methyl chloride
1~L4~
- 55 -
1 s~,ream so feea to the reactor remained unchanged except
2 that no functional polvstyrene stabilizer precursor was
3 being fed. Within a few minutes the effluent besan to
4 become coarser and to thicken 2nd very rapid reactor
5 foulins began to occur. Polymer besan to severely plate
6 out insi~e the overflow tube'and on the heat transfer sur-
7 Caces (as evidenced by an increase in the tem?erature dif-
8 ference between coolant and reactor). Within 15 minutes
9 it was no longer possible to maintain reactor temperature
10 because of the foulins insiae the rezctor and the reactor
11 beaan to warm. ~ithin 20 minutes the reac-tor had completely
12 plugsed wi.h agglomerated rubber--the stirrer j2mmed and
13 the over'low was solidly plugsed. The run hac to be
4 stopped and the rezctor solvent-washed to remove the agglo-
15 mer2ted rubber deposited within it.
16 .~cter thoroushly washing the reactor to clean
17 it, an attempt was made to restart it unae~ the same con-
18 ditions wi~h ?ure methyl chloride for ~eed 2 so there was
19 no stabilizer precursor be~ing fed. ?olymerization initiated
20 well but as slurrv concentration beaan to build in the
21 reactor, the effluent became very thick and ra?i~ fouling
22 ensuec. Wi_hin less than an hour, lons before a steady-
23 state had been achievea, the reacto_ was completeiv fouled
24 out and ~lugsed again. ClearlY this -e~cto~ cânnot o?er-
25 ate at such 2 hish slurry concentration without a sta~il-
26 izer present and the sreat benefits of VBC-c2~ped polysty-
27 rene as a slurry stabilizer precursor in a continuous
28 butvl reactor are evident.
- 114~ 6
- 5~ ~
1 Example llC
.
Ir. ~is example, a styrene/vinyl benzyl chloride
3 co?olymer produced by radical polymerization was used as
; 4 stabilizer precursor. This unctional polystyrene was
prepared by r2dically polymerizing a 54.8~ monomer (styrene
6 plus vinvl benzyl chloride) in toluene feed containins 1.0%
7 vinyl benzyl chloride on monomers to ~8.2% conversion at
~ 80C with AZBN as the initiator. The functional styrene
9 copolymer produced had an ~Iv of 42,000 and contained 0.31%
chlorine due to the copolymerizec vinyl benzvl chloride.
11 It was dissolved in methvl chloride to yield a 2.35% solu-
12 tion OL ~he functional polystyrene in methyl chlorlde as
13 a feed to the reactor. The feeds to the reactor for this
14 example were:
Feed 1 was 77.4% monomers, consisting of 2.65
16 isoprene and 97.35% isobutylene, in methyl chloride and
17 was fed into the bottom draft tube of the reactor (up the
18 propellor shaft) at a rate of 49.9 græms per minute.
lg ~eec 2 was 2.35~ of ,he styrene/vinvl benzyl
chloride copolymer stabilizer precursor in methyl chloride.
; 21 It W2S metere2, chilled, and hen blended with chilled
i .. ,
2? Feed 1 and fed in~o the reactor at a ~a_e of 23 gr2ms per
23 minute.
24 ~ eec was ~he catalvs, s~eam consisting o~
25 0.28% ~lC13 in me.hyl chloride an2 it W2S fed into the
26 to? annulus of the reactor at a rate of 10.7 ræms per
27 minute.
28
Z8f~
-- 57 --
1 Feed 4 was pure methvl chloride and was metered,
2 chilled, and then blended with ~eeds l and 2 and fed into
3 the reactor at a rate of 42.0 grams per minute. Total
4 feed in grams per minute, to the reactor t~en were:
Isoprene - 1.02
6 Isobutylene - 37.60
~ethyl Chloride - 85.91
Radical Styrene~Vinyl
9 Benzyl Chloride Copolvmer - O.54
AlCl3 - 0.03
11 Total - 125.1
12 The stabilizer precursor level was 1.4% on mono-
13 mers.
14 At steady-state the re2ctor effluent was a 30.0%
15 slurry of butyl rubber in methyl chloride plus unreacted
16 monomers. The reactor effluent consisted of:
17 ~ 37.53 grams Butyl Rubber
18 l.09 grams Monomers
19 85.91 grams Methyl Chloride
0.54 gr2ms Polystyrene (pa~tly bound to butyl)
21 0.03 srams AlCl3
22 125.1 grams ~otal
23 Reactor temperat~re wzs cont-olled at -93C and
24 the effluent was a smoothly flowln~, yellow tinted, non-
25 fouling very fine dispersion of butyl rubber particles
26 which turned white upon quenchins. Conversion of mono-
27 mers to butyl W25 97.2% and the reactor W2S operating
28
_ ~ 8 -
1 smocthly producing a stable slur-y wi`.h no evi2ences o~
2 fOuling
3 ~eed 2 to .he reactor was then sim?ly replaced
4 with a pure methyl chloride stream so thzt feed to the
5 reactor remained unchanaed except that no functional poly-
6 styrene stabilizer precursor was being fed. As in Example
7 ll B, within a Cew minutes the reactor effluent became
8 coarser and thickened and very rapid reactor fouling com-
9 menced. I~ithin 15 minutes the reactor had warmed and
10 plugged--the stirrer was jammed and the reactor was full
11 of agglomerated slurry. The run had to be stopped and the
12 reactor warmed and solvent-washed to dissolve the butyl
13 rubber deposited in it. ~his experiment again demonstrates
14 the effectiveness of a s.abilizer in improving butyl reac-
15 tor perfo-mance znd enabling the benefits cited in this
16 invention to be realized. With .he stabilizer present,
17 the reactor could be operate~ at more than double the
j 18 slurrv concentrz.ion possible without it.
19 These experiments in the continuous ?ilot unit
20 bu.yl rezctor have shown that the stabilizers which were
21 e-fective in the batch dry box runs are also effective in
22 a continuous reactor and ma~e it prac,ical .o achieve on
23 a commercial sc21e all of the benefits noted in this inven-
24 tion for the use of slurry stabilizers in tne production of
25 butvl rubber.
. .
~14~Z86
; 5
SUPPLEMENTARY DISCLOSURE
In the principal disclosure it is taught that cationically active
functionality of the stabilizer polymer or its components was in most
circumstances to be avoided.
It has since been discovered that functional groups with a low degree
of cationic activity, or present at low concentrations may be only marginally
active under typical butyl polymerization conditions. The degree to which
these groups participate in the polymerization reaction to form chemical bond
attachments to the product polymer depends upon the polymerization conditions
(monomer conversion, temperature, steady-state monomer and stabilizer
concentrations, etc.). Under some polymerization conditions marginally active
functional groups are effectively inert so that no appreclable chemical bond
attachment to the product polymer occurs and the preformed stabllizing agent
primarily functions by adsorption on the product slurry particles. Under other
polymerization conditions appreciable chemical bond attachment to the product
polymer can occur through these marginally cationically active groups. To the
extent that chemical attachment occurs, the preformed copolymer stabilizer is
acting as a functional lyophile and forms, in situ, a new stabilizer with the
product polymer as the lyophobe. Thus, as hereinbefore stated, the
effectiveness of the preferred copolymer is not dependent upon in situ
completion of the formation of the stabilization agent but some degree of in
situ participation of the preformed copolymer can occur.
If cationic activity is even higher, then extensive and multiple
attachments to the product polymer can occur and the stabilizer may become
undesirable for use during polymerization. Given that a stabilizing agent as
disclosed herein functions effectively to stabilize the product polymer slurry,
its suitability as a preformed stabilizing agent will be predicated, in part,
on formation of a gel-free polymer product; the absence of gelled material on
~'' : . .
:,'
Z86
. G~'
reactor surfaces is also a desirable feature. The end use appllcatlon to which
the product polymer will be put can have significant impact on the choice of
stabilizing agent and it~ tendency to result in gel formation under the
polymerization conditions. Some applications may require that the product be
gel-free, whereas in others the presence of gel may be tolerable or even
preferable (e.g. mastics).
For example, referring particularly to the experiments of Examples 2A
and 2B, for the purpose of illustration, it may be noted that it is not
necessary - although it is preferable - that a diene/styrene bloc~ polymer
contalning 27 mole ~ styrene be added after completion of polymerization in
order to ftnctitn :. slurry atabiliter for a butyl ~lurry in tethyl chloride.
,
:'
.~, _ . .
