CA1103846A - Method for preparation of copolymers of isobutylene, which contain unsaturations and reactive halogen atoms - Google Patents

Abstract

METHOD FOR THE PREPARATION OF COPOLYMERS
OF ISOBUTYLENE WHICH CONTAIN UNSATURATIONS AND REACTIVE
HALOGEN ATOMS.

Abstract of the Disclosure Vulcanizable copolymers of isobutylene with linear trienes are prepared by halogenation of a previously prepared isobutylene-triene copolymer, The reaction is carried out preferably at subzero temperatures and in the dark due to the high react-ivity of certain halogenating agents: among these, even Haloid acids can be used, that which was impos-sible with the prior art procedures. The novel halogenated copolymers have a better behaviour when sulphur cured than the conventional chlorobutyl rubbers.

Description

This invention relates to a method for the prepara-tion of copolymers of isobutylelle ~hich contain unsatura-tions an-l reclctive halogQn atoms.
Tll~ pr~paratioll is know.n oE isobutylcne copolymers~
which col~nercially called "Butyl Rubber" and contain small percentages o~` isopreJ~e statistically distributed along the polymeric chain in order to supply residual unsatura-tions in the polymer~ susceptible of being exploited in the vulcanization processes. These copolymers have found a number o~ applications by virtue oE their impervious-ness to gases~ resistànce to ozone and to oxidizing agents in general, and the high value of the dampening coeffi-cientO A limit to the predictable applications of such products is t.heir low curing speed~ even if ultra-accele rators are used~ and to the impossibility of carrying out miscellaneous curing with them and various unsaturated elastomers~ be these latter natural or synthetic (NR~
SER~ ER and others)~ These problems have partly been off-set by a process of halogenation of such copolymers~ :
which has led to a product known in the trade as "Chloro-butyl Rubber"~ which displays properties which are consi-derably improved over those of.the starting copolymer. It. ~ -has been shown (Rubber and Plastic Age~ 42~ 500, (1961), that the halogenatlon reaction of isobutylene-isoprene copolymers takes place~ specificaIly~ on the structural isoprene moiety and is a substitution of an allyl hydro~en atom by a halogen atom~ while the evolution of a molecule of an haloid acid. The princip~l structures whi.ch are formed are : -- `..... ... .:

,

2.
~

:
~ 3~6 CH-~ C - CH - (A) ~1 Il 2 - CH2 - C - ~H - (B~

- CH2 ~ f CH _ CH - (C) Cl and these involve the presence of secondary allyl halogen atoms (A,B) or tertiary allyl halogen atoms, which are allegedly held responsible for the high reactivity of this elastomer as far as the vulcaniæation reactlon is concerned, along with the possi-bility, in the usual compounding formulas with sulfur, of the formation o~ "mixed" lattice having intermolecular bonds of the : -type -C-S-C, and -C-O- (these latter originated by curing with metal oxides). The Applicants have recently found (British patent no. 1,5~9,645) that is is possible to prepare novel copo-lymers of iso-butylene by copolymeri.zation thereof with parti~

cular linear trienes which contain the three double bonds in a conjugated arrangement, the linear trienes being an amount of from o.1% to ~ molar with respect to iso-bu-tylene and said co-polymers isobutylene-linear trienes,~These copolymers are charac-- terized in that they contain in the-polymeric chain a number of highly reactive conjugated double bonds which impart to,the po- -.lymer quite special properties and features.
During progress of the study of these materials, the Applicants have ascertained that their reactivity relative to the sulfur curing reactions can further ve enhanced by reacting such materials with halogens or with haloid acids. The reaction takes place under extremely bland condi-tions as to temperature and concentration of the reactants and involves the discharge of the conjugated ~ 3 diene system from the polymer. In addition, no formation of by-products is exper.ienced during progress of the react-ion, the latter bei.ng essentîally an addition of the halogen or the haloid acid in the 1-4 positions o~ the conjuga~ed diene sys-tenl~ the result being the formation of structures of th~ following type :

CH - C~ ~ CEI - C~l2- ~ Y2 ~ 2 1 l X X (D) CH - CH /CH = CH
10-CH -Ci ~ ~ CH-C}I +HX ~~~~ ~l2 C 2 C~ -CH2- (E) In the case of (D) structures are formed~ which are composed by a double bond with two adjoining halogen atoms in a secondary allyl position~ whereas in the case of (E) a double bond is present with a single adjoining halogen atom in a seconclary allyl position. The high reactivity o-E such halogen atoms relative to the curing with ZnO is well known~ but by comparing the structures (D) and (E) a~bove with these which are present in the ~Chlorobutyl ~o Rubber"g a fe~ differences can be seen~ More particularly~
; the products of this invention have no halogen atoms of the tertiary allyl type (C): these latter~ due to the too :
: high mobility of the halogen atom can originate spontaneous thermal degradation phenomena (~ubber and Plastic Age~ -42~ 500~ (1961). The products obtained by the present Applicants after a halogenation reaction have a curing speed higher than that of "Chlorobutyl Rubber" and produce :
vulcanizates having outstanding mechanical and heat-resi-stance features and which are oxidation-resistant.
- 3o Trienes which can be used for the synthesis of the - oopolymer are :
1~ 3~ 5 hexatriene~ 1~3~5 heptatri~ne~ 2~4~6-octatriene~
2,6-dimethyl~ 2,4~6-octatriene and others. The amount of 4- .

triene can be varied from 0.1% ~;o 8% (molar %) relati~e to isobutylene The special properties which i~entify these hovel copolymers reside7 therefore~ both in the structure of the starting copolymer and ln thc trend of the halogenation reac-tion along wltl- the possibility of carrying ou-t such a reaction with haloicl acids (tha-t which cannot be clone ill the case Oe the i.sobutylclle-isoprene-copolymcrs)~ and in the structure of the halogenatlon products which can be obta.ined and their properties rela-tive to the curing reactions as well.
The fields of use in which these copolymers can profitably be exploited are for tires~ o the tubeless type~ inner tire bags~ tire curing bags~ conveyor belts :
for hot materials~ tubes for conveying hot fluids~ con~ : -tainers for pharmaceutical products~ technical and house hold sunclries (such as gaskets and sponges), sealing and waterproofing compounds.
The worki.ng conditions adopted for carrying out the halogenation reaction require that the solution oE the copolymer is contacted with the halogenating agent (pre-ferably a halogen~ or a haloid acid) either in solution or in gaseous phase.
The reaction media to be adopted include those which are conventionally used for this kind of reaction: more ~5 particularly~ aliphatic and cycloaliphatic hydrocarbons having up to 12 carbon atoms~ the corresponding mono-or polyhalogenated compounds and CS2~ it being~ however~ -possible also to work without any solvents by direct inter-. action of the halogenating agent with the finely ground polymerO . - .
Particular examples of solvents which can be used~
are n-pentane~ n-hexane~ n-heptane~ methylene chloride~
. chloroform~ carbon tetrachlori.de~ cyclohexane5 methy~l-cyclohexane. The reaction is usually carried out in the dark~ at a temperature comprîsed between -80C and ~80C

. ' 5- ' .

3~6 by employing stoichiometrically molar quantities of the halogenating agent relative to the contents of conjugated double bonds which are containcd in the copolymer~ The contents of halogen which is f'ound in the final proclucts is thus variable and is compr:ised between 0.4% and 8 mainly o.6~ to 4%~ on molar pexc~ntage basis.
Thc halogenating agcnts to be used basically belong to t~Yo classes, viz~ :
1)' ~k~logens~ interhaloge1lic compounds or compounds which are anyhow capable of behaving as halogena-ting agents~ and 2) Haloid acidsO
Examples of the first class of compounds are :
C12~ Br29 I2~ ICl~ IBr~ S02C12~ SOC12~ N-bromo-succini~ide~
N-chloro-succinimide.
~xamples of the se¢ond class of compounds are :
HClg HBr~ HI.
The physico-chemical analysis o~ the polymers has been carried out with UV radiations (235 millimicron band attrlbuted to the conjugated double bonds of the type -~
-CH=CH-CEI=CH-) and with IR radiations (10.1 micron hand attributed to the conjugated double bonds of the trans con-figuration). The determination of the quantity of the conjugated double bonds has been carried out by UV
analysis ( k = 235 millimicrons) by employing as the pattern ':
compound 2~4-hexadiene trans~trans ( ~ - 24~500). ~ ..
The halogen contents i~ the polymer has been deter-mined by combustion of the polymer with the Schoniger method and analysis of the combustion product~ as reported by Microchimica Acta~ 480~ 1961.
The molecular weight of the polymers has been deter-mine~ on th'.~3 basis of viscosity ~easurements carried out in cyclohexane at ~30C and employing the following equation: :
ln PMV ~ 11.98 ~ 10452 ln / ~ 7 / ~_7 has been determined by extrapolating to C -~ 0 6, :. , the ma~litude ~7 /C and PM is the v.iscometric mol~wt.
~, s~c V
is the intrins.ic viscosity ~ is the specl.ic viscos:ity C is t;llC conccn~rat;ion in graltls/100 IlllS
The advantlgos o the present in~en~ion are more ~l~ta:i.lccl:Ly illustra-ted by the following nonlimiting examples thereoE.
EXAMPLE
By way of example~ there is reported the preparation of a -typical isobutylene-trienc copol~ner~ which is the starting product from the subsequent halogenation reactions~
By working wi.th similar ~rocedures~ it is also possible to prepare the several copolymers which are used in the subsequent examples.
A tubular glass reactor having a volume of 300 mls~
fitted with mechanical stirrer and a thermometric jacket~
has been previously dried and maintained in an atmosphere of dry argOn and then charged with 40 mls of liquid CH3Cl~
28.4 grams of isobutylene~ 40 mls of anhydrous n-heptane and 0.7 ml of 1~3~5-hexatriene (99% purity). The tempe-rature is brought to -75C~ whereafter there are slowly introduced 0.4 millimols of Al Et C12 dissol~ed in 5 mls of n~heptane during 13 minutes Concurrently with the addition of the catalyst~ there are introduced in the poly-merizing solution r6 addi-tional mls of 1~3~5-hexatriene7 dilu~ed with 4 mls of n-heptane~ these being evenly distributed during the period of introduction of the catalyst.
The reaction is allowed to proceed during 10 addition-al minutes by maintaining the temperature of the reaction mixture between -71C and -600C~ sO that an extremely viscous polymeric solution is obtained. The reaction is discontinued by introducing 2 mls of ammoniated CH30H~

7~

... ~ , , ~3~3f~6 the polymer is coa~ulated i.n a 50/50 (volume) mixture of methanol and acetone and dried in a vacuo.
There are thus obtainecl 8~o5 grams of cIry polymer ( yield = 20~5%)~ hav:ing a ~ .~ 7 equal to 2.01 dl/g (PMV - 420~000) and containing 1.55 mo:lar percent oE diene unsatur.Itiolls as deternl:inecl~yith`uv analysis.
EX~MPLE 2 __ .
300-ml~ three necked Ç].ask fltted with stirring mechanism and kept in the dar-k~ is charged with 100 mls of a solu-tion in n-heptane which contains 6 grams of the polymer of Example l. The flask is cooled to 0C~ where-after there are slowly introduced 8 mls of a solution of Cl2 in CCl4 which contains 1.8 millimols of Cl2~ with energetic s-tirring during 10 mins. The reaction is allow~
ed to proceed for lO additional minutes~ whereafter the polymeric solution is washed with H20 and coagulated in acetone~ The as-obtained polymer is dried in a vacuo at a temperature oE 50C overnight~ so that 5~6 grams of a dry polymer are obtainedg which has an intrin$ic viscosity in cyclohexane equal to 2.05 dl/g (PMV '.430~000).
UV and IR analyses of the product denounce the complete ~ :
discharge of the conjugated diene unsaturations~ The deter- - .
mination of the chlorine contents gives a:value of 1.63% ~.
by weight. The as-obtained polymer has been subjected to curing at the temperature of l~OC for variable times~ .
by employing the following compounding formulation :
Polymeric lOO parts by weight HAF black50 l~ tt (N 330) MBTS l tt 1~
TMTD 1 t, n .Stearic acid 3 " 11 . Ao2246 (antiox.) l ~1 " ~ ..
ZnO 5 Sulfur 2 ~ "

- 8.

. . ' . - ~ , TABLE 1 reports the rheometric data and the properties of the vulcanizates relative to the polymer described above (Sample A) and of a commer-cial sample of "Chloro-bu-tyl Rubber ~ (Sample B)~ the latter having the follo~r-ing character.istics :
Cl = :I.35%~ / ~ 7 = 1-95 dl/g T~.BLE l_ Sample A B
___ _ Rheometr.ic data (~
MV () (N.m) 1~7 106 MT (N.m) () 5~7 508 T2 (min.) 1 min 15 sec1 min 40 sec Tgo(min~) 8 min 0 sec18 min 30 sec Mechanical properties o~ the vulcanizates at room temperature for various curing t.imes : B
time (mins.) 15 min----30-~1E~ S~ 15 min.3060 minO min.
Mod~300% (M Pa) 1111~5 12.5 9-7 10.8 12.4 Tensi~le (M Pa) 22.12104 20~9 21,9 20.0 20.2 Elongation%at break . 525455 45~ 582 530 500 Tension set % 4 2 2 5 5 3 :
() At 160C in a Monsanto Model 100 Rheometer~ oscilla-tion arc 3 degreesO Readings -takes according to R~W. Wise~ G. E. Decker~ ASI~ Special Technical Publication N 383 (1965)~
, () Minimum value of Torque (Newton.meter) (~ Maximum value of Torque (Newton.meter) The data of TABLE 1 indicatetthat the sample A) shows a higher curing speed and be-tter mechanical proper- ~
. ties -than the commercial copolymer Bo EXAMPLE _ ~
With the same procedure as in Example 2~ a Çlask is charged~ in the dark~ with 100 mls of a solution in CHC13 containing 5 grams of a copolymer having the follow-ing properties : % Of conjugat~d (.louble bonds=0.99; /~7 - 2~12 dl/g;PM~-460~000. There are slowly introduced~in the clark~at a temperature of 20C~0.95 millimol oE C12 dissolved in 6 mls of CCl durin~5 minutesO The polymer as described above is .

38~
~ollec~-d an~l there are vb~ainecl 4 6 grams o a dry poly-n~er h~ving ~he ~ollow~ prop~rties:
% of conjug.a-ted double bonds = 0 ; %Cl (by ~t6) =
~ 1~1; / ~ 7 a 2/02 dl/~; ~M - 420l000.
The polymer has bcen cured accordin~ to the compound-ing formula r~ported :in l.xamplo 2 and the properties of the. v~lcani~a~es~ at room teltlperlture~ nro reportcd in TABLI3 ~. Th~ data ill(l:iCate thc forltllt:ion o a satls-Eactory vu:Lclll:iza~c~ even tl~ough :its properties are below those of the prod-lcts o~` TABLE 1.
TABL~ 2 Properties of the vulcanizate at room temperature for different curing times :
Time (mi.nutes) o-f cure15 m.in. 30 min. 60 min.
Modulus at 300% elO(MPa) 7-6. 7.8 7.6 Tensile strength (MPa). 20.0 20.5 19.6 Elong. at break~ % .585 580 590 Tension set~ ~ 8 7 7 There are used 100 mls oE the same solution of the isokutylene-1~3~5-hexatriene co~olymer as used in EXAMPLE 3. Through such a solution~ cooled to -15C~ a .
gaseous stream of IICl is bubbled during 60 minu-tes. The temperature of the mixture is allowed to rise to 0C and the reaction is allowed to proceed during 10 additional hours. The polymeric solution is washed with distilled water and the above indicated ~olymer is coa~ulated as described above. There are obtained 406 grams. of a dry - polymer having the following properties :
% of conjO double bonds~residual : 0.11 % Cl (by wt.) = 0.95 / ~ 7 - 2.20 dl/g PMV - 480~000 .:
The polymer has been cured under the conditions of Example 2 and the properties of the vulcanizates as ob tained with different curing times and measured at room 35 . temperature are repor-ted in TABLE 3 10~

TABT.E _3 Time of cure~minO 15 mins. 30 mins. 50 mins.
Modulus 300% (~IPa) 6.8 7-3 7-3 Tensile strengtll (~lI'a) ~803 18.8 19.1 Elong. at brcalc~ % 655 610 560 Tonsion set~ % ~ 8 MPA ~ gapasca:L~ SI Unît.
EXA~IPL~ 5 TO a ~olut:ion of the samo copolymer oE the previous Examplc in CHCl3 (5 grams in 100 mls.)~cooled to -10C~
there are slowly added~ with st:irring~ 3 millimols o-f anhydrous HBr dissolved in 6 mls of CCl~ 4 Stirring is continued for 2 hours after that th0 temperature of the solution has been brought to 0CO The polymer is collected as described hereinabovc and th.ere are obtained 4.7 grams thereo ; the polymer has the following properties :
% of residual conjugated doubl.e bonds : 0~07; %Br (by wt~) -- 2.1; ~ ~ 7 = 2.0 dl/g ;PMV = 420~000. The sample~
subjected to tec~mological tests~ gives a vulcanizate having mechanical properties which are akin to those of the previous sample~ but with a higher curing kineticsO

-A solution ln CHCl3 ( 5 grams in 100 mls of solution) is employed of an isobutylene-2~436-octatriene copolymer having the following properti.es :
% of conjugated double bonds = 1.64 ; / ~ 7 = 1.90 dl/g ;
PMV = 390~000 and prepared with a method simîlar to that which had been followed for the sample described în Example l. The solution is transferred to a flask3 in the dark~ at the temperature of 0C and supplemented with 105 millimols o-f Br2 dissolved in 4 mls of CC14 for a time of 20 minutes. There collected~ using the procedure as described abovea 4.7 grams of a dry polymer which has the following properties :
% of nonjugated double bonds = 0 ; Br % (by wt~) = 3.2 ;

7 - 1.75 ~Il/g ; PMV = 340~0000 With the sallle proce.dure as indicated in Example 1 an lsobutylene-1~3~5-11eptatrlerle copo]ymer is pr~pared~
having thc fo:Llo~lng properties :
% con;jugat,cd clouble boncls a 1 . 35 ; ~ ~_7 = 2.14 dl/g ;
PMv ~ 480~000. I~ solut:ion containing 5 ~rams o the copolymer in a volume oE 100 m.ls i.s placed in a flask~
in the clark~ and treated at the temperature of 0C with 1.5 millimols of S02C12 dissol~ed in 5 mls of CC14, The reaction is proceeded with for 3 hours7 whereafter the polymeric solut:ion is washed with H 0 llntil a neutral reaction is seen and the polymer is collected as described hereinabove. There are obtained 4.6 grams of a dry polymer which has the follow:ing properti.es : ~ -% conjugated double bonds : 0.05 ; Cl % (by wt.) = 1.48; ~
1 ~7 - 1.90 dl/g ; PMV = 390JOOO.
The sample~ as cured under the same conditions as for Example 2~ has a vulcanizat:ion behaviour and techno-logical properties similar to those of the sample of Example 2.

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Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for the preparation of copolymers of isobutylene containing unsaturations and reactive halogen atoms, comprising the step of reacting a halogenating agent with copolymers of isobutylene with linear trienes containing three double bonds in a conjugate arrangement, the linear trienes being in an amount of from 0.1% to 8% molar with res-pect to isobutylene and said copolymers isobutylene-linear trienes, containing in the chain conjugate double bonds in order to obtain a.copolymer of isobutylene having the follo-wing structural units:

(D) (E) X being a halogen atom; the quantity of halogenating agents can reach the sto?chiometnio? molar value with respect to the comonomer.

2. A method according to claim 1, wherein the ha-logenating agent is selected from the group constituted by the halogens and the haloid acids.

3. A method according to claims 1 or 2, wherein the halogenating agent is selected from among C12, Br2, I2, ICl, IBr, SO2C12, SOC12, N-bromosuccinimide.

4. A method according to Claims 1 or 2, wherein the haloid acid is selected from among HCl, HBr, HI.

5. A method according to Claims 1 or 2, wherein the temperature is comprised between -80?C and + 80?C.

6. A method according to Claim 1, wherein the halo-gen contents in the end product varies from 0.4% to 8% molar.

7. A method according to Claim 6, wherein the ha-logen contents in the end product varies from 0.6% and 4 molar.

8. A method according to Claims 1 or 2, wherein the reaction is caused to occur in the presence of a solvent selected from among the aliphatic and cycloaliphatic hydro-carbons having up to 12 carbon atoms, the corresponding mono-or polyhalogenated derivatives and carbon sulphide.