CA2140005A1 - Tire sidewall composition - Google Patents

Abstract

A tire sidewall composition having improved properties is provided. The composition comprises a halogen-containing copolymer of a C4 to C7 isomonoolefin and a para-alkylstyrene, and an unsaturated rubber, such as natural rubber. Tires comprising the sidewalls are also provided.

Description

~,'"') 94/01295 2 1 ~ O O O S PCr/US93/06488 - ' IMPROVED TIRE SIDEWALL_COMPOSITION

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BACKGROUND OF THE INVENTION

1. Field of the Invention - The present invention relates to tire sidewall ~- co~positions which exhibit improved ozone resistance and fatigue crac~ propagation resistance, as well as good sidewall adhesion to the tire carcass and good heat build-up.
~' 2. Descri~tion of Information Disclosures Rubber tires, such as pneumatic tires, include many components, such as, for example,~sidewalls, which may be decorative and may have incorporated therein a titanium dioxide pisment. Sidewalls are continuously subjected to distortion unde.r the normal road operating conditions, and the sidewalls are subjected to extensive continuous flexing and can crack under such flexing conditions. In addition to such flex cracking, such sidewalls are also subjected to atmospheric chemical action such as by ozone attack. The overall effect is that the sidewalls may erode and degrade and can even separate from the tire carcass during use and can cause the tire to fail.

Generally, the c~rrent practice in the manufacture of black sidewalls is to add chemical protectants to general purpose rubbers in an attempt to minimize ozone and flex crac~ing but they tend to be fu~ative and staining in the case of contact with white sidewalIs , . ~

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WO94/01295 2 l4 ~ ~ n ~ ~ PCT/US93/0~88;

combination. In some cases, and in particular white sidewalls, polymer blends have been used to effect~ ¦
improvement in ozone and flex resistance.

A composition which attempts to overcome these problems is disclosed in U.S. Patent No. 3,508,595 to 3 Wilson, and assigned to the General Tire & Rubber Company. This patent discloses a blend of chlorobutyl rubber, natural rubber, and ethylen~ propylene terpolymer as the protective cover for the white sidewalls used in such pneumatic tire construction.
-U.S. Patent No. 3,630,974 to Ladocsi, et al.,assigned to Exxon Research and Engineering Company, further discloses the use of terpolymers for blending into high unsaturation rubbers in order to enhance their static ozone resistance. This patent also discloses a triblend of halobutyl rubber along with a terpolymer and a high-unsaturation rubber to improve dynamic ozone resistance and heat flex resistance. The terpolymers employed by this patentee comp~ise ethylene, propylene and a diene, and the high unsaturation rubber can include natural rubber, styrene butadiene rubber, and polybutadiene rubber, etc. It is again noted that various fillers can be used in these compositions, and among the variety of materials listed are various "oils" along with resins, waxes, etc. The patentee specifically discloses the use of lO parts oil per lO0 parts of rubber in these formulated blends. This patent also discloses that the terpolymer used will not include morerthan lO or 20% of the diolefin therein. It is also notëd that while U.S.
Patent No. 3,865,763 to Feniak, assigned to Polysar Limited, is primarily concerned with stabilization of halogenated butyl rubber with boron compounds, Example 5 of that patent discloses a combination of brominated butyl rubber with both an ethylene propylene rubber and a s~yrene butadiene rubber.

,~094/01295 2 1 ~ O O 0 5 PCT/US93/0~88 U.S. Patent No. 3,830,274 to Waser, Jr., assigned to The Goodyear Tire and Rubber Company, discloses yet another elastomer blend for use in pneumatic tire sidewall compositions, which contains an ethylene propylene non-conjugated diene terpolymer along with bromobutyl rubber and a cis-l,4 polyisoprene rubber such as natural or synthetic rubber, along with a rubbery cis-l,4 polybutadiene with a specified molecular weight distribution. The patentee sates that this blend provides substantially improved hot flex-life and carcass adhesion properties for tire sidewalls.

U.S. Patent 4,224,196 discloses a sidewall composition having improved flex resistance, wherein the blend composition comprises a blend of a halobutyl rub~er, a highly unsaturated rubber and an oil extended EPDM terpolymer.

There is still a need for improvement in properties of tire sidewalls.

SUMMARY OF THE INVENTION

The present invention relates to tire sidewall compositions which comprise a blend composition of at least one highly unsaturated rubber, and a brominated copolymer of an isoolefin and~ a para-alkylstyrene, wherein the blend composi~ions exhibit improved ozone resistance and fatigue crack propagation resistance as well as good sidewall adhesion to ~he tire carcass, good heat build-up, and good aging characteristics, wherein the compositions may additionally optionally include an EPDM terpol~lmer and/or halobutyl rubber.

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wo g4/0-29s 2 1 ~ O ~ O ~ PCr/USg3/064~

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In a preferred embodiment of the present invention the sidewall composition comprises from about 10 to about I ~;
parts of a highly unsaturated rubber such as of natural rubber, and from about 10 to about 90 parts of brominated copolymer of an isoolefin and a para- ~
alkylstyrene, wherein the alkylstyrene unit is ~, -halogenated (e.g. brominated) and character~zed by the 1-formula:

H
~ CH2 ~J

R-~-X `~
R ~-! .
wherein R and Rl are independently selected from the group consisting of hydrogen, alkyl groups having about 1 to about 5 carbon atoms, and primary and secondary alkyl halides having about 1 to about 5 carbon atoms and X is selected from the halogen group consisting primarily of bromine and chlorine and mixtures thereof. Furthermore, ¦
the halogenated para-alkylstyrene unit is shown as being pendant from the isoolefin polymer chain, represented by wavy lines in the formula.
~ ~-The sidewall compositions of the present invention can be compounded by methods generally known in the rubber compounding art, such as by mixing with the uncured ~polymers various fillers such as titanium dioxide; carbon black, when black sidewalls are desired, or non-black fillers and pigments and the absence of carbon black when white sidewalls are desired; extenders such as rubber process oils; curing aids such as zinc '~'094/01295 2 1 ~ O ~ ~ 5 PCT/US93/06488 oxide, sulphur; accelerators or retarders and other additives such as anti-oxidants, and anti-ozonants. ' DETAILED DESCRIPTION OF THE INVENTION

The principal advantages realized in accordance with the present invention primarily stem from the fact that by employing the halogenated copolymer of isoolef in and para-alkylstyrene in blends with general purpose rubber (GPR), i.e., highly unsaturated, one obtains improved ozone resistance and fatigue crack propagation of these compositions as well as improved sidewall adhesion.

It has also been found that compositions having desirable characteristics can be obtained by utilizing the halogenated para-alkylstyrene copolymer with only one other unsaturated rubber such as natural rubber in the absence of other rubber components. This is particularly effective in white sidewall for~ulations.

The tire sidewall composition of the present invention comprises blend compositions of from about l0 to about 90 parts by weight per hundred of total rubber content of at least one highly unsaturated rubber selected from the group consisting of natural rubber, SBR
rubber, polyisoprene and polybutadiene rubber, preferably about 20 to about 80, more preferably about 30 to about 70; and from about l0 to about 90 parts per hundred of a halogenated copolymer of an isoolefin and a para-alkylstyrene, wherein the halogen is bonded to the para-alkyl group of the para-alkyl styrene unit, more preferably about lS to about 85 and most preferably about 20 to about 80 parts; for example, about 30 to about 70 parts. In particularly preferred compositions userul in tire sidewalls, the halogenated copolymer comprises at WO94/0129~ ' PCT/US93/~f~ ~' .

least about 35 to about 75 parts, for exampie, 40 parts, and the highly unsaturated rubber comprises natural rubber and/or polybutadiene rubber. The blend composition may also optionally include from about 1 to about 90, preferably about 5 to about 40 parts of halobutyl rubber and/or from about 1 to about 40 parts, preferably about 5 to about 20 parts per hundred of EPDM.
When white sidewalls are desired, particularly preferred compositions comprise the halogenated para-al~ylst,yrene copolymers and natural ru~ber in a weight ratio of halogenated para-alkylstyrene copolymers to natural rubber ranging from about 0.28:1 to about 3:1, prererably from about 0.67:1 to about l:l. The preferred halogenated para-alkylstyrene copolymer for the white sidewall embodiment comprises preferably from about 5 to about lS, more preferably from about 5 to ~out 10 weight percent para-alkylstyrene moieties and pre~erably from about l to about 2 wt.% more preferably about 2 weight percent halogen. In addition to the rubber components, the white sidewall tire composition may comprise additional additives such as~ non-black fillers and pigments, and processing aids.

The highly unsaturated rubbexs of the present blend compositions are selected from the group consisting of natural rubbers, polyisoprene rubber, styrene butadiene rubber (SBR) and polybutadiene rubber and mixtures thereof. The natural rubbers of the present invention are selected from ~he group consisting of Malaysian rubber such as SMR CV, SMR 5, SMR 10, SMR 20, and SMR 50 and mixtures thereof, wherein the natural rubbers have a Mooney viscosity at lOO-C (ML 1+4) of a~out 30 to about 120, môre preferably about 40 to about 65. The Mooney ,' ~iscosity test referred to herein is in accordance with ASTM D-1646. -~

~094/0l~9~ 2 1 ~ O Q ~ PCT/~S93/~88 1 ;;

The Mooney viscosity of the polybutadiene ru~ber of the present invention as measured at lOo C (ML 1+4) may range from about 40 to about 70, more preferably about 45 to about 65, and most preferable about 50 to about 60.
When both natural rubber and polybutadiene are employed in the present invention, a suita~le weight ratio of the natural rubber to the polybutadiene ranges from about lOo to 1 to 1 to 100, more preferably 5 to 1 to 1 to 5, and most preferably 2 to 1 to 1 to 2.

EPDM is the ASTM designation for a terpolymer of ethylene, propylene and a non-conjugated diolefin. In such terpolymers the ethylene and propylene form a fully saturated bac~bone of methylene linkages with the non-conjugated diolefin, e.g. dicyclopentadiene or substituted norbornene, attached so as to provide unsaturzted side chains with readily available crosslinking sites for sulphur curing. The EPDM
elastomers thus contain a fully saturated bac~bone which provides outstanding resistance to oxidation, ozone, and cracking, as well as exce~lent low temperature flexibility. The Mooney viscosity of the EPDM terpolymer as measured at 125~C is about 20 to 80, more preferably about 25 to 7S and most preferably about 40 to about 60.
The ethylene content of the EPDM terpolymers may range from about 20 to about 90 weight percent, preferably from about 30 to about 85, more preferably from about 35 to about 80 weight percent. The total diene monomer content in the EPDM terpolymers may suitably range from about 0.1 to about 15 weight percent, preferably from about 0.5 to about 12 weight percent.

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The non-conjugated dienes may be straight chain or cyclic hydrocar~on diolefins having from 6 to 15 carbon atoms, such as dicyclopentadiene, tetrahydroindene, including al~yl substituted tetrahydroindenes, 5-methylene-2-norbornene, 5-vinyl-2-norbornene, 2-methyl-WO94/01295 2 1 4 0 0 0 ~ ` PCT/USg3/~8~

norbornadiene, 2,4-dimethyl-2,7-octadiene, 1-4-hexadiene, 5-ethylidene-2-norbornene, and 3-methyl cyclopentene.
The ~ost preferred compounds include 5-methylene-2-norbornene, dicylopenta- diene, 1,4-hexadiene, 5 ethylidene-2-norbornene, and 4,7,8,9-tetrahydroindene. A
preferred EPDM terpolymer of the present invention is Vistalon0 6505 manufactured by Exxon Chemical Company.

The term "butyl rubber" as employed herein is intended to refer to a vulcanizable rubbery copolymer containing, by weight, from about 8~ to 99.5% combined - -isoolefin having from 4 to 8 carbon atoms and 0.5 to lS%
combined conjugated diolefin having 4 to 8 carbon atoms.
Such copolymers and their preparation are well known. The isoolefin, such as isobutylene, is admixed with a conjugated diolefin havin~ about 4 to 8 carbon atoms, such as butadiene or isoprene, preferably isoprene. An inert diluent selected from C4 to C8 aliphatic alkanes and chlorinated hydrocarbons such as methyl chloride, ethyl chloride, methylene chloride and ethylene dichloride are admixed therewith.~ The monomers may form - from lO to 50% by weight of the total monomer/diluent mixture. The mixture is cooled and polymerized in a reactor at a temperature in the range from about O C to about 165-C using a cationic catalyst such as aluminum chloride, aluminum bromide, aluminum ethyl dichloride, titanium tetrachloride or boron trifluoride. The polymerization reaction proceeds rapidly to produce a copolymer in the form of a slurry in the diluent. The slurry is removed from the reactor and the copolymer separateO therefrom and recovered by well-known methods.

The preferred butyl rubbers which are used to produce halogenated rubbers useful in this invention are copolymers of isobutylene and isoprene which are normally produced using methyl chloride as diluent and aluminum trich1oride catalyst. Preferably the copolymers have an I
i ~94/0~29~ 2 1 ~ ~ O~Q 5 PCT/US93~88 _ g -isobutylene oontent of from about 95 to 99.5 weight percent. The halogenated copolymer should preferably contain at least about 0.5 weight percent of combined halogen, but not more than about one atom of chlorine or three atoms of bromine per double bond present in th~
original copolymer. Preferably, it contains from about 0.5 to about 2 weight percent of chlorine or from about 0.5 to about 5 weight percent bromine. Most preferably, the halogenated polymer is a halogenated butyl rubber containing from about 1.0 to akout 1.5 weight percent chlorine or from about 1.0 to about 2.5 weight percent bromine. The halogenated isobutylene-isoprene copolymer rubber can also contain more than one halogen in its structure, e.g., chlorine and bromine.

The butyl rubber may be halo~enated ~y means known in the art. The solid rubber may be reacted in an extruder using halogen gas or on a hot rubber mill or internal mixer with a compound which releases halo~en such as N-halo-succinimide and N-halo-hydantoin.
Alternatively, the butyl rubber ~ay be dissolved in an inert hydrocarbon solvent such as pentane, hexane or cyclohexane and halogenated by addition to the solution of elemental chlorine or bromine. In a typical commerclal process, butyl rubber is dissolved in a solvent to form a solution containing from about 5 to about 30 weight percent of rubber. Elemental chlorine or bromine is added to the solution, at a temperature of 0 to about lOO~C, in sufficient quantity that the chlorinated or brominated rubber recovered contains up to 1 a~om of chlorine or up to 3 atoms of bromine per carbon-carbon double bond originally in the butyl rubber.

The Mooney viscosity of the halobutyl rubbers useful in the instant invention as measured at 125C (ML 1+4) range from about 20 to about 80, more preferably about 2S
to about 55, and most preferably about 30 to about 50.

WO94/0129~ 2 ~ S PCT/US93/~

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Suitable halogen-containing copolymers of a C4 to C7 isomonoolefin and a para-alkylstyrene for use as a component of the present tire sidewall composition comprise at least 0.5 weight percent of the para-alkylstyrene moiety. For elastomeric copolymer products, the para-alkylstyrene moiety may range from about 0.5 weight percent to about 20 weight percent, preferably from about 1 to about 20 weight percent, more preferably from about 2 to about 20 weight percent of the copolymer.
The halogen content of the copolymers may range from above zero to about 7.5 weight percent, preferably from about 1.0 to about 7.5 weight percent. The halogen may be bromine, chlorine, and mixtures thereof. Preferably, the halogen is bromine. The major portion of the halogen is chemically bound to the para-alkyl group, that is, the halogen-containing copolymer comprises para-halo alkyl groups. Particularly preferred copolymers comprise from about 5 to about 10 weight percent para-alkylstyrene, and from about 1 to about 2 weight percent halogen, for example, bromine. ~

The copolymers of the isomonoolefin and para-alkylstyrene useful to prepare the halogen-con~aining copolymers suitable as component of the tire sidewall composition of the present invention include copolymers of isomonoolefin having from 4 to 7 carbon atoms and a para-alkylstyrene, such as those described in European patent application 89305395.9 filed May 26, 1989, (Publication No. 0344021 published November 29, 1989).
The preferred isomonoolefin comprises isobutylene. The preferred para-alkylstyrene comprises para-methylstyrene.
Suitabl'e copolymers of an isomonoolefin and a para-alkylstyrene include copolymers having a number average molecular weight (Mn) of at least about 25,000, preferably at least about 30,000, more preferably at least about 100,000. The copolymers also, preferably, ~;

~ 94/OIZ95 ~ 2 1 ~ O O 0 5 PCT/US93/0~8 1 ~

have a ratio of weight average molecular weigh~ (Mw) to ~ ;
number averaqe molecular weight (Mn)l i-e-, Mw/Mn f less than about 6, preferably less than about 4, more preferably less than about 2.5, most preferably less than 1 -~
about 2. The brominated copolymer of the isoolefin and para-alkylstyrene obtained by the polymerization of these particular monomers under certain specific polymerization conditions now permit one to produce copolymers which comprise the direct reaction product (that is, in their as-polymerized form), and which have unexpectedly i homogeneous uniform compositional distributions. Thus, by utilizing the polymerization and bromination procedures set forth herein, the copolymers suitable for the practice of the present invention can be produced.
These copolymers, as determined by gel permeation chromatography (GPC) demonstrate narrow molecular weight distributions and substantia}ly homogeneous compositional distributions, or compositional uniformity over the entire range of compositions thereof. At least about 95 1 weight percent of the copolymer product has a para- -alkylstyrene content within abou~ 10 wt. percent, and preferably within about 7 wt. percent, of the average para-alkylstyrene content for the overall composition, and pref-erably at least about 97 wt. percent of the copolymer product has a para-alkylstyrene content within a~out 10 wt. percent and preferably within about 7 wt.
percent, of the average para-alkylstyrene content for the ~ r overall composition. This substantially homogeneous compositional uniformity thus particularly relates to the intercompositional distribution. That is, with the specified copolymers, as between any selected molecular weight -fraction the percentage of para-alkylstyrene therein,~or the ratio of para-alkylstyrene to isoolefin, will be substantially the same, in the manner set forth above.

~1400~ -WO94/01295 PCT/US93/0~ ~
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In addition, since the relative reactivity of para-alkylstyrene with isoolefin such as isobutylene is close to one, the intercompositional distribution of these copolymers will also be substantially homogeneous. That is, these copolymers are essentially random copolymers, and in any particular polymer chain the para-alkylstyrene and isoolefin units will be essentially randomly distributed throughout that chain.

The halogen-containing copolymers useful in the practice of the present invention have a substantially homogeneous compositional distribution and include the para-alkylstyrene moiety represented by the formula:

~ ~-CH2-~J

R-~-X
Rl ~

in which R and Rl are independently selected from the group consisting of hydrogen, alkyl preferably having from 1 to 5 carbon atoms, primary haloalkyl, secondary haloalkyl preferably having from 1 to 5 carbon atoms, and mixtures thereof and X is selected from the group consisting of bromine, chlorine and mixtures thereof, such as those disclosed in European patent application 8930595.9 filed May 26, 1989, (Publication No. 0344021 published November 29, 1989).

~ arious methods may be used to produce the copolymers of isomonoolefin and para-alkylstyrene, as described in said European publication. Preferably, the polymerization is carried out continuously in a typical continuous polymerization process using a baffled tan~-21400~
, ~vo 94/01295 PCr/US93/06488 type reactor fitted with an efficient agitation means,,such as a turbo mixer or propeller, and draft tube, external cooling jacket and internal cooling coils or other means of removing the heat of polymerization, inlet pipes for monomers, catalysts and diluents, temperature sensing means and an effluent overflow to a holding drum or quench tank. The reactor is purged of air and moisture and charged with dry, purified solvent or a mixture of solvent prior to introducing monomers and catalysts.

Reactors which are typically used in butyl ru~ber polymerization are generally suitable for use in a polymerization reaction to produce the desired para-alkylstyrene copolymers suitable for use in the process of the present invention. The polymerization temperature ,;
may range from about minus 3S C to about minus lOO C, preferably from about minus 40 to about minus 80 C.

The processes for producins the copolymers can be carried out in the form of a slurry of polymer formed in the diluents employed, or as a homogeneous solutiQn process. The use of a slurry process is, however, preferred, since in that case, lower viscosity mixtures are produced in the reactor and slurry concentration of up to 40 wt. percent of polymer are possi~le.

The copolymers of isomonoolefins and para-alkyl-styrene may be produced by admixing the isomonoolefin and the para-alkylstyrene in a copolymerization reactor under copolymerization conditions in the pre~ence of a diluent and a Lewis acid catalyst. 9 Typical examples of the diluents which may be used alone or in a mixture include propane, butane, pentane, cyclopen~an , hexane, toluene, heptane, isooctane, etc., and various halohydrocar~on solvents which are a ~.

.

WO94/01295 21 ~ Q 0 ~ ~ PCT/US93/~

particularly advantageous herein, including methylene, chloride, chloroform, carbon tetrachloride, methyl chloride, with methyl chloride being particularly preferred.

~ n important element in producing the copolymer is the exclusion of impurities from the polymerization reactor, namely, impurities which, if present, will result in complexing with the catalyst or copolymerization with the isomonoolefins or the para-alkylstyrene, which in turn will pre~ent one from producing the para-alkylstyrene copolymer product useful in the practice of the present invention. Most particularly, these impurities include the ca~alyst poisoning material, moisture and other copolymerizable monomers, such as, for example, meta-alkylstyrenes and the like. ~hese impurities should be kept out of the system.

In producing the suitable copolymers, it is preferred that the para-alkylstyrene be at least 95.0 wt.
percent pure, preferably 97.5 wt. percent pure, most preferably 99.5 wt. percent pure and that t~e isomonoolefin be at least 99.5 wt. percent pure, preferably at least 99.8 wt. percent pure and that the diluents employed be at least 99 wt. percent pure, and preferably at least 99.8 wt. percent pure.

The most preferred Lewis acid catalysts are ethyl aluminum dichloride and preferably mixtures of ethyl aluminum dichloride with diethyl aluminum chloride. The amount of such catalysts employed will depend on the desirèd molecular weight and the desired molecular weight distribution of the copolymer being produced, but will generally range from about 20 ppm to l wt. percent and preferably from about O.OOl to 0.2 wt. percent, based upon the total amount of monomer to be polymerized.
-., -'VO94/0129~ 2 1 ~ O O Q S PCT/US93/06488 j., - lS -Halogenation of the polymer can be carried out in~
the bulk phase (e.g., melt phase) or either in solution or in a finely dispersed slurry. Bulk halogenation can be effected in an extruder, or other internal mixer, suitably modified to provide adequate mixing and for handling the halogen and corrosive by-products of the reaction. The details of such bulk halogenation processes are set forth in U.S. Patent No. ~,548,995, which is hereby incorporated by reference.

Suitable solvents for solution halogenation include the low boiling hydrocarbons (C4 to C7) and halogenated hydrocarbons. Since the high boiling point para-methylstyrene makes its removal by conventional distillation impractical, and since it is difficult to completely avoid solvent halogenation, it is very important where solution or slurry halogenation is to be used that the diluent and halogenation conditions be chosen to avoid diluent halogenation, and that residual para-methylstyrene has been red~ced to an acceptable level.

With halogenation of para-methylstyrene/ isobutylene copolymers, it is possible to halogenate the ring carbons, but the products are rather inert and of little interest. However, it is possible to introduce halogen desired functionality into the para-methylstyrene/
isobutylene copolymers hereof in high yields and under practical conditions without obtaining excessive polymer breakdown, cross-linking or other undesirable side reactions.

It should be noted that radical bromination of the enchained para-methyl styryl moiety in the useful copolymers for the practice of this invention can be made highly specific with almost exclusive substitution W094/01~95 2 1 ~ O O O ~ - l6 - PCT/US93/~3~

occurring on the para-methyl group, to yield the desired benzylic bromine functionality. The high specificity of the bromination reaction can thus be maintained over a broad range of reaction conditions, provided, however, that factors which would promote the ionic reaction route are avoided (i.e., polar diluents, Friedel-Crafts catalysts, etc.).

Thus, solutions of the suitable para-methylstyrene/isobutylene copolymers in hydrocarbon solvents such as pentane, hexane or heptane can be selectively brominated using light, heat, or selected radical initiators (according to conditions, i.e., a particular radical initiator must be selected which has an appropriate half-life for the particular temperature conditions being utilized, with generally longer half-lives preferred at warmer hydrogenation temperatures) as promoters of radical halogenation, to yield almost exclusively the desired benzylic bromine functionality, via substitution on the para-methyl group, and without appreciable chain scission and/or ~rosslinking.

This reaction can be initiated by formation of a bromine atom, either photochemically or thermally (with or without the use of sensitizers), or the radical initiator used can be one which preferentially reacts with a bromine molecule rather than one which reacts indiscriminately with bromine atoms, or with the solvent or polymer (i.e., via hydrogen abstraction). The sensitizers referred to are those photochemical sensitizers which will themselves absorb lower energy photons and disassociate, thus causing, in turn, disassoc~ation of the bromine, including materials such as iodine. It is, thus, preferred to utilize an initiator which has a half life of between about 0.5 and 2500 minutes under the desired reaction condi'ions, more preferably about lO to 300 minutes. The amount of l`~'094/01295 2 1 ~ O O 0 5 PCT/US93/0~88 ~`
!:

initiator employed will usually vary between 0.02 and 1 percent by weight on the copolymer, pre~erably between about 0.02 and 0.3 percent. The preferred initiators are bis azo compounds, such as azo bis isobutyronitrile (AIBN), azo bis (2,4 dimethyl valero) nitrile, azo bis (2 methyl butyro) nitrile, and the like. Other radical initiators can also be used, but it is preferred to use a radical initiator which is relatively poor at hydrogen abstraction, so that it reacts preferentially with the bromine molecules to form bromine atoms rather than with the copolymer or solvent to form al~yl radicals. In those cases, there would then tend to be resultant copolymer molecular weight loss, and promotion of undesirable side reactions, such as crosslinking. The radical bromination reaction of the copolymers of para-methylstyrene and isobutylene is highly selective, and almost exclusively produces the desired benzylic bromine functionality. Indeed, the only major side reaction which appears to occur is disubstitution at the para-methyl group, to yield the dibromo derivative, but even this does not occur until more~than about 60 percent of the enchained para-methylstyryl moieties have been monosubstituted. Hence, any desired amount of benzylic bromine functionality in the monobromo form can be introduced into the above stated copolymers, up to about 60 mole percent of the para-methylstyrene content.

It is desirable that the termination reactions be minimized during bromination, so that long, rapid radical chain reactions occur, and so that many benzylic bromines are introduced for each initiation, with a minimum of the side reactions resulting from termination. Hence, system purity is important, and steady-state radical concentrations must be kept low enough to avoid extensive recombination and possible cross-linking. The reaction must also be quenched once the bromine is consumed, so that continued radical production with resultant W094/0l~95 ~ PCT/US93/064 secondary reactions (in the absencP of bromine) do not then occur. Quenching may be accomplished by cooling, turning off the light source, adding dilute caustic, the addition of a radical trap, or combinations thereof.
. .
Since one mole of H8r is produced for each mole of bromine reacted with or substituted on the enchained para-methylstyryl moiety, it is also desirable to neutralize or otherwise remove this HBr during the reaction, or at least during polymer recovery in order to prevent it from becoming involved in or catalyzing undesirable side reactions. Such neutralization and removal can be accomplished with a post-reaction caustic wash, generally using a molar excess of caustic on the HBr. Alternatively, neutralization can be accomplished by having a particulate base (which is relatively non-reactive with bromine) such as calcium carbonate powder present in dispersed form during the bromination reaction to absorb the HBr as it is produced. Removal of the HBr can also be accomplished by stripping with an inert gas (e.g., N2) preferably at elevated~temperatures.

The brominated, quenched, and neutralized para-methylstyrene/isobutylene copolymers can be recovered and finished using conventional means with appropriate stabilizers being added to yield highly desirable and versatile functional saturated copolymers.

In summary, halogenation to produce a copolymer useful in the present invention is preferably accomplished by halogenating an isobutylene-para-methylstyrene copolymer using bromine in a normal alkane (e.g., h~xane or heptane) solution utilizing a bis azo initiator, e.g., AIBN or VAZ0~ 52: 2,2'-azobis(2,4-dimethylpentane nitrile), at about 55 ~o 80 C, for a time period ranging from about 4.5 to about 30 minutes, followed by a caustic quench. The recovered polymer is I

`'O 94/012g~ 2 1 ~ O O O ~ PCrtUSg3/06488 :
, - 19 - ' washed in basic water wash and water/isopropanol washes, recovered, stabilized and dried.

The aromatic halomethyl groups permit facile crosslinking to be accomplished in a variety of ways, for example, either directly through the halomethyl group or by conversion to other functional groups, as indicated above, to permit the desired crosslin~ing reactions to be employed. Direct crosslinking- can ~e effected with a variety of polyfunctional nucleophilic reagents such as ammonia, amines, or polyamines; metal dicarboxylates;
metal dithiolates; promoted metal oxides ~e.g., ZnO +
zinc stearates and/or dithiocarbamates), etc.
Crosslinking can also be effected via polyalkylation reactions. The aromatic halomethyl groups thus provide a wide choice of crosslinking reactions which can be used.

Various fillers can also be used in the blend compositions of the present invention, and these include a variety of carbon blacks, clays, silicas, carbonates, oils, resins, and waxes. Carbon ~lacks preferred for use in black tire sidewall compositions of this invention include t~ose types designated N339, N774, N660, N351 and N375; the latter two types are particularly preferred.
Alternatively, non-black fillers and pigments may be used for white tire sidewalls. The blends are cured with conventional curatives for highly unsaturated or chlorobutyl rubbers, including sulphur, alkylphenol disulphide, zinc oxide, sulphenamide derivatives, guanidines, benzothiazyldisulphide (MBTS) and mercaptobenzothiazole (MBT).

The tire sidewall composition of the present invention may be vulcanized by subjecting it to heat and/or light or radiation according tO any vulcanization process. Typically, the vulcanization is conducted at a temperature _anging from about 100C to about 250C, W094/0~29~ 2 1 4 0 ~ 0 5 PCT/US93~8~

preferably from about 140C to about 200C, for a time period ranging from one minute to several hours.

The tire sidewall composition of the present invention may be used in producing sidewall for tires, for example, motor vehicle tires such as truc~ tires, bus tires, passenger automobile, motorcycle tires, and the like.

Suitable tire sidewall compositions may be prepared by using conventional mixing techniques including, e.g., kneading, roller milling, extruder mixing, internal mixing (such as with a Banbury0 mixer), etc. The sequence of mixing and temperatures employed are well known to the skilled rubber compounder, the objective being the dispersion of fillers, activators and curatives in the polymer matrix without excessive heat buildup. A
useful mixing procedure utilizes a Banbury mixer in which the rubber components, fillers, and plasticizer are added and the composition mixed for the desired time or to a particular temperature to achiev~ adequate dispersion of the ingredients. Alternatively, the rubbers and a portion of the fillers (e.g., one-third to two-thirds) is mixed for a short time (e.g., abut 1 to 3 minutes) followed by the remainder of the fillers and oil. Mixing is continued for about 5 to 10 minutes at high rotor speed during which time the mixed components reach a j temperature of about 140C. Following cooling, the -components are mixed in a second step on a rubber mill or in a Banbury mixer during which the curing agent and optional accelerators, are thoroughly and uniformly dispersed at relati~ely low temperature, e.g., about 80 to about 105C. Variations in mixing will be readiiy apparent to those s~illed in the art and the present invention is not limited to any specific mixing procedure. The mixing is performed to disperse all components of the composition thoroughly and uniformly.

~;

21~0005 -~ '094/0129~ PCT/US93/~88 !`

Tires are generally built on a drum from at least t~ee layers, namely, an outer layer comprising a tread portion and sidewalls, an intermediate layer, and an inner layer. After the uncured tire has been built on a building drum, the uncured tire may be placed in a heated mold to shape it and heat it to vulcanization temperatures and, thereby, to produce a cured unitary tire from the multi-layers.

Vulcanization of a molded tire, typically, is carried out in heated presses under conditions well known to those s~illed in the art.

Curing time will be affected by the thickness of the tire to be molded and the concentration and type of ruring agent as well as the halogen content of the halogenated copolymer. However, the vulcanization parameters can readily be established with a few experiments utilizing e.g., a laboratory characterization devic-e well known in the art, ~he Monsanto Oscillating Disc Cure Rheometer (ODR, described in detail in American Society for Testing and Materials, Standard ASTM D 2084).

The following examples are presented to illustrate the invention. All parts and percentages herein are by weight unless otherwise specified.

Exam~le 1 A tire sidewall composition was prepared by compounding the components as set forth in Table I
(Banbury size B) using a mix cycle as shown below.
Composition 1-1 is a "control" or reference composition, not a composition of the present invention.

WO94/0129~ 2 1 4 0 ~ ~ ~ PCT/USg3/~

- Table I
Compos~tion No. 1-1 1-2 1-3 1-4 BRBU 22333 ~- 45 ~~ ~~
Vistalon 6~054 -- 10 10 -- ~
BrIB-PMS A -- -- 45 55 :;
N 660 Black 50 -- -- --N 339 Black -- 25 25 25 N 774 Black -- 25 25 25 Flexon 641 Oil 10 12 12 12 :
SP 1077 Resin -- 3 5 5 -Wood Rosin FF -- 2 -~
Stearic Acid 2 1 2 2 Flectol H 2 -- -- --Santoflex 13 2 -- -- -- .
Sunolite 240 Wax l -- -- --Zinc Oxide 3 3 Sulfur 1.75 0.2 0.2 0.2 Santocure MOR 1 -- -- --Vultac 5 ~~ 0-4 0.4 0-4 MBTS -- 1.2 1.2 1.2 1. Natural Malaysian Rubber 2. BR 1207 - polybutadiene rubber-Mooney viscosity of 55 at 100-C

3. BRBU 2233 - Brominated butyl ~ubber having 2 wt.% ~:
bromine and a Mooney viscosity of 38 at 125C

4. Vistalon 6505 - EPDM terpolymer having 50 wt.% of ethylene, 50 wt.% of propylene and 9 wt.% of E~B and a Mooney viscosity of 55 at 125-C

5. Isobutylene-para-methylstyrene copolymer having 5 wt.~ para-methylstyrene, 1.1 wt.% bromine and a Mooney viscosity at 125-C of 30.

Mix C~cle O min - add polymers and stearic acid 1.0 min - add black 2.2 min - add other ingredients except ZnO and curatives ~:
4.0 min - dump 140-C
Zinc oxide and curatives added on a cool mill The; tire sidewall blend compositions (1-1 to 1-4) ~.
were tested for static ozone, dynamic ozone and fati~ue crack propagation; the results are summarized in Table 7 II.

214~3~ l 094tO129~ PCT/US93/0~88 Table II

Static Ozone ¦
100 ~Dhm. 30 C. 660kPa Stress Time to Failure, h <24 160 >300 >300 D~namic Ozone .100 ~Dhm. 0-20% ext 30 C l :
Time to Failure, h 48 >288 ~288 >288 -Fatigue Crack Propagation DC/DN at 15% Strain. 60 C
In air, Nm/cyc 30.9 26.2 20.4 16.2 In Ozone, Nm/cyc 48.5 40.8 22.9 18.0 *Dynamic ozone and fatigue crack propagation tests are described in an article by D.G. Young in Rubber Chemistry ard Technology - Vol.
58, No. 4.

Blends 1-3 and 1-4 exhibite~ better ozone resistance and low fatigue crack propagation.

ExamDle 2 Sidewall blend compositions were prepared according to the procedure of Example 1 as shown in Table III.
i~

, WO94/0129~ Q 5 PCT/USg3/~

Table III

ComPosition No. 2-1 2-2 - I'"
SMR 5 60 30 ,~
Butadiene rubber 1207 -- 30 BrIB-PMS A 40 40 N660 Black 50 50 1~
Flexon 641 Oil 12 12 .
Escorez 1102 5 5 Stearic Acid 2 2 .
Zinc Oxide 1.5 1.5 Sulfur 0.4 0.4 Vultac 5 0-4 ~ 0 4 MBTS 1.2 1.2 The sidewall blend compositions (2-1 and 2-2) were -;
tested for adhesion to general purpose rubber (GPR) ,, composition, Tan Delta and dynamic ozone; the test ~,~
results are summarized in Table IV.

Table IV
* 2-1 2-2 Control Adhesion To GPR 25-C . .
70NR/155BR/15BR, kN/m 8.9(I) 10.5(T/I)25 (T) Tan Delta 100 Hz, + 10~ strain, 60^C 0.143 0.096 0.050 .
Dynamic Ozone 100 c,~hm. 0-20% ext. 30 C
Time to Failure, h >200 >144-<168 48 *Control is formulation 1-1 f'~
The use of butadiene rubber in the blend composition !.
resulted;in some improvement in adhesion (I refers to ~
interfacial separation, T refers to tearing failure) and .
a significant reduction in Tan Delta. , , .

; -vo 94/01295 214 0 3 0 ~ ` PCrIUS93/06488 Exam~le 3 i ~.
Tire sidewall blend compositions were prepared, generally according to the procedure of Example 1, using the formulations shown in Table V. The compositions used brominated copolymers of isobutylene-paramethylstyrene, ' variations in the type and concentration of the highly unsaturated rubbers as well as variations in carbon black type and curative concentration. The variations are i within the scope of the invention and represent preferred compositions useful as tire sidewall components.
Properties of the compositions are shown in Table VI.

Table V
Composition ~o. 3-1 3-2 3-3 3-Natural Rubber (SMR 5) 30 30 25 25 BR 1207 ~ 30 30 35 40 BrIB-PMS Bl 40 -- 40 35 , -BrIB-PMS c2 -- 40 -- --N660 Black 50 50 SO --N351 Black -- ~ 40 Flexon 641 Oil 12 12 12 12 Escorez 1102 Resin 5 5 -- -- -SP 1077 Resin -- -- 5 5 Stearic Acid 2 2 Zinc Oxide 3 3 Sulfur 0.4 0.4 1.0 1.0 Vultac 5 1.5 1.5 0.8 0.8 MB~S 1.7 1.7 0.75 ~,~
0.75 1. Brominated isobutylene-paramethylstyrene copolymer: 5 wt.% paramethylstyrene, 1.95 wt.% bromine and a Mooney viscosity at 125-C of 29.
2.~ Brominated isobutylene-paramethylstyrene copolymer: 10 wt.% paramethylstyrene, 1.95 wt.% bromine and a Mooney viscosity at 125-C of 29.

W094~01295 ~l~QO~ PCT/US93/ ~ ' ~

Table VI ~;
Co~position No. 3-1 3-2 3-3 3-4 Dynamic Ozone 1onoohm~0-20%ext~
Time to failure, h 120 >216 >300 ~200 Static Ozone OO~Dhm 30 c.660kPa ure, h >216 >216 -- --~an Delta lOOHz,+5%strain,60-C 0.100 0.098 0.126 0.127 Adhesion to GPR.XN/m >35(T) ~~ '`
lOO C g.5(T) 9.8(T) 12.3(T) 19.2(T) Moonev Scorch.135-C ,~
Min. to 5 pt. rise 7.9 7.9 11.4 11.7 These compositions of the invention demonstrate outstanding resistance to ozone and are capable of developing good adhes-ion, acceptable processing safety (Nooney scorch) and tan delta (resilience). A range of preferred tire sidewall performance properties can be !
achieved using the halogenated isobutylene- para- -alkylstyrene copolymer. The specific concentrations of ingredients to be used in a formulation will be dependent on the specific needs of the tire manufacturing process and the environment in which the tire is used.

.~ .
, .
ExamDle 4 A white tire sidewall composition was prepared by compounding the components shown in Table ~II (Banbury size 3?~ using a mix cycle shown below. Compositions 4-1, 4-2, 4-3, 4-4, and 4-5 were compositions in accordance with the present invention. Composition 4-6 was a comparative composition which was not in accordance with the present invention.

21~0005 ~ YO94/012~ PCT/USg3/0~#~ , .

Copolymer A was a halogenated copolymer of isobutylene 3 .and para-methylstyrene containing 10 wt.% para-methylstyrene 3`
moieties, 2.5 wt.% bromine, a Mooney viscosity at 125C of 46, and 1.5 mole % brominated para-methylstyrene moieties.
Copolymer B was a copolymer of isobutylene and a para-methylstyrene containing 15 wt.% para-methylstyrene moieties; 2.0 wt.% bromine, a Mooney viscosity at 125C of S0, and 1.1 moIe ~ brominated para-methylstyrene moieties.

1 ~ ' ~ .

i~

:, .

: ' . ., 21~0~05 WO 94/01295 PCT/US93/~8 Table VII ¦

Com~osition No. 4-1 4-2 4-3 4-4 4-5 4-6 Vistalon 6505 -- -- -- -- -- 20 Copolymer A 70 70 -- -- -- --Copolymer B -- -- 70 60 50 --TiO2 1000 2S 25 25 25 25 25 Nucap 290 32 32 32 32 32 32 Mistron Vapor 34 34 34 34 34 } 4 Sunolite 240 Wax 3 3 3 3 3 3 Stearic Acid Ultramarine Blue 0. 2 0.2 0.2 0.2 0. 2 0.2 Escorez ll 02 4 4 4 4 4 4 Zinc Oxide 3 3 3 3 3 5 Sulfur 0.5 1.3 1.0 1.0 1.0 0.5 Vultac ~5 1.3 1.0 1.3 1.3 1.3 1.3 7 MBTS 1.0 l.O 1.0 1.0 1.0 1.0 Mix Cvcle O minute - add polymers 1.0 minute - add one half the remaining ingredients 2.2 minutes - add balance of ingredients 4.0 minutes - dump 140C r Zinc oxide and curelines added on cool mill.

Tire sidewall compositions of Table VII were tested for various properties. The results of the tests are shown in Table ~III.

~ o 94~0l2gs 2 1 ~ O O O S ~ ` ~ PCT/U593/O~WN ~ ~

- 29 - ~
,',"-TABLE VIII
Compositions ProDerties 4-l 4-2 4-3 4-4 4-5 4-6 Mooney Scorch, 135-C ~
Min. to 5pt. Rise24.3 20.3 15.0 15.2 15.8 18.8 ;
Mooney Viscosity ML - 1+4' @ 100-C 45 46 46 46 46 44 ~
Rheometer - 160-C ,i `
MH, in. - lb.43.0 43.1 45.5 42.0 43.3 39.8 ML, in. - lb. 7.5 6.8 4.5 4.8 5.0 7.0 -ts2, min. 5.8 5.9 4.7 4.7 4.6 4.7 ~-~
- tc90, min.23.2 21.8 20.8 15.2 14.8 20.8 ~`
Tensile, MPa13.1 13.4 13.2 14.2 14.1 9.3 300% Modulus, MPa4.5 6.4 6.5 5.4 5.5 4.3 % Elongation700 620 530 640 627 603 Shore A Hardness55 55 57 56 57 52 Dynamic Ozone 100 pphm, 20% Ext.500+ 500+ 500+ 500+ 500+ sOO+
Hrs. to Crack .
Static Ozone 100 pphm, Bent Loop500+ 500+ 500+ 500+ 500+ 5~0+
Hrs. to Crack `,? :
Strip Adhesion - Kn/m.
(Tc90 + 5' @ 160-C) To black sidewall:
@ RT 4.5 3.9 4.0 3.9 5.93.6 @ lOO-C 2.0 2.0 1.7 2.1 3.11.5 T T T T T T
Outdoor Flex ;
(Pierced Only)500+ 500+ 500+ ~500+ 500+ 500+

Weatherometer Hrs. to Crack700+ 700+ 700+ 700+ 700+ 700+ , WO94/01295 2 1 ~ O ~ 0 5 pCT/US93/0 64~ , , The test methods used are shown in Table IX. I ~

Table IX ~ .
', Test Test Method ~ ' Mooney Scorch ASTM D1646 ASTM D1646 . , Mooney Viscosity ASTM D1646 Tensile, MPa ASTM D412 300% modulus ASTM D412 % Elongation ASTM D412 Shore A Hardness ASTM D2240 Dynamic Ozone ASTM D339S

Static Ozone ASTM D1149 Strip Adhesion ASTM D2630 Outdoor Flex Described below :;

The outdoor flex test is performed by cutting a specimen into a strip and fastening the strip at both ends across a horizontal rod. Thereafter, the fastened specimen is repeatedly flexed in a forward and backward .
motion. The test specimen is observed at regular intervals, e.g. daily for indication of cracking. The results are reported as hours to the first indication of cracking.

As can be seen from Table VIII, the compositions of :
the present invention had improved cured adheslon and -~094/0129~ 2 1 4 0 ~ ~ 5 PCT~US93/0~88 . ". :

comparable perfor~ance in ozone and ultraviolet resistance at higher levels of natural rubber (compare Composition 4-5 of the present invention to comparative Composition 4-6).

Exam~le 5 White sidewall compositions were prepared by compounding the components shown in Table X using the mix cycle shown in Example 4. Copolymer C was a brominated copolymer of isobutylene and para-methylstyrene containing 15 wt.% para-methylstyrene moieties and 2 wt.%
bromine. Copolymer D was a brominated copolymer of isobutylene and para-methylstyrene containing 10 wt.%
para-methylstyrene moieties and 2 wt.~ bromine.
Copolymer E was a brominated copolymer of isobutylene and para-methylstyrene containing 7.5 wt.% para-methylstyrene moieties and 2 wt.% bromine. Copolymer E was a copolymer of isobutylene and para-methylstyrene containing 5 wt.%
para-methylstyrene moieties and l~wt.% bromine.

Table X

Com~osition No. 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 Copolymer C 50 -- -- -- -- -- -- 35 Copolymer D -- 60 -- 50 -- -~
Copolymer E -- -- -- -- 60 50 35 --Copolymer F -- -- 70 -- -- -- -- --Natural Rubber 50 40 30 50 40 50 65 65 Ti~2 25 25 25 25 25 25 25 25 Nucap 290 32 32 32 32 32 32 32 32 Mistron Vapor Talc 34 34 34 34 34 34 34 34 Sunolite 240 Wax 3 3 3 3 3 3 3 3 Stearic Acid 1 1 1 1 1 l 1 1 Ultramarine Blue 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Escorez 1102 4 4 4 4 4 4 4 4 Zinc Oxide 3 3 3 3 3 3 3 3 Sulfur 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Vultac '5 1.0 1.3 1.3 1.3 1.3 1.3 1.3 1.3 MBTS '.3 1.0 1.0 1.0 1.0 1.0 '.0 1.0 WO 94/0129~ 2 ~ 4 0 0 0 5 ` PCI/US93/06~ 1~

The tire sidewall compositionc of Table X were tested for various properties. The results of the tests are shown in Table XI. `~

214000~ ~
,~vo 94/0129i PCr/US93/06488 ~ I~
comDositions , j Pro~erties 5-1 5-2 5-3 5-4 5-5 5-6 5-75-8 Mooney Scorch, 135-C t ' Min. to 5 pt. rise 16.7 16.7 18.4 15.5 14.1 13.7 13.914.2 Mooney Viscosity I~L(1+4) ~ 100-C 40 38 38 38 49 49 46 38 Rheometer - 160-C
3-ARC.
Ml" lbf-in. 6.0 7.0 6.5 7.0 9.8 10.0 10.07.8 MH, lbf-in. 46.0 46.0 44.6 42.5 44.8 47.5 48.547.0 -tSa, min. 5.0 5.0 5.8 4.8 5.0 4.5 4.84.8 t'cgo, min. 11.1 15.0 17.2 13.0 14.1 12.0 11.411.0 Shore A 52 S5 S2 50 55 54 52 50 Cured Properties @
t~cgo, 160-C
Tensile, mPa 13.6 13.8 11.4 13.9 14.5 16.9 18.817.1 300% k5Odulus, mPa 6.2 6.3 4.7 5.7 6.4 6.7 6.77.3 ~c Elongation 540 528 633 557 577 575 607522 Rt Dynamic Ozone 20% Ext., 100 pphm .~ , -Hours to crack 200+ 200+ 200+ 200+ 200+ 200+ <100~100 Static Ozone Bent Loop-100 pphm Hours to crack 200+ 200+ 200+ 200+ 200+ 200+ ~100<100 Outdoor Flex DeMattia-Pierced Hours to crack 500+ 500+ 500+ 500+ 500+ 500+ <400<400 @ RT(~ 21.5 22.1 22.2 20.9 23.1 23.0 23.820.9 ,-@ 100 C 12.0 11.9 12.4 11.4 11.8 12.0 11.611.1 Strip Adhesion ~ RT 7.8 7.2 8.8 7.2 7.2 7.9 8.66.4 @ 100-C ' 2.9 2.5 2.3 2.6 1.9 2.6 2.81.9 To General Purpose ~ubber Black Sidewall @ ~T 7.1 6.8 7.0 6.5 7.2 7.2 7.25.3 @ 100-C 2.6 2,.1 2.1 2.1 2.3 2.8 3.0 RT means room temperature t ~

WO94/01295 2 1 ~l o b ~ ~ ` PCT/US93/0~ ~

As can be seen from Table XI, Compositions 5-l through 5-8, which were compositions in accordance with the present invention comprising the preferred ratios of components, had particularly improved properties, such as ozone resistance, resistance to cracking, and good adhesion to tire carcass.

A description of ingredients used in the above examples that are not otherwise described is shown in Table XII.

;-~v094/01295 . 2 1 ~ O O Q 5 PCT/US93/0~88 Table_XII
Inqredient DescriPtion Sup~l er Escorez 1102 Petroleum hydrocarbon Exxon Chemical tac~ifier resin Americas Flectol H Polymerized 1,2 dihydro- Harwick 2,2,4-trimethylquinoline Chemical Corp. :
Flexon 641 Oil Naphthenic petroleum oil Exxon Co., USA
(ASTM Type 103 Santocure MOR 2-(morpholinothio)benzo- Monsanto Chemi~
thiazole cal Co.
Santoflex 13 N,N'-phenyl-p-phenylene Monsanto Chemi-diamine cal Co.
SP 1077 Resin Alkyl phenolformaldehyde Schenectady resin Chemicals Sunolite 240 Wax Blend of petroleu~ waxes Witco Chemical Vultac 5 Alkyl phenol disu fide Pennwalt Chemi-on inert carrier c~l Wood Rosin FF Thermoplastic naval Harwick .~
stores tackifying resin Chemical Corp ~.
Nucap 290 Mercaptosilane ~ J. M. Huber functionalized hydra~ed aluminum :~
silicate :
Mistron Vapor Nagnesium Cyprus silicate organo- Industrial ~:
functional surface Minerals modified CIIR 1066 Chloro-isobutene- Exxon Chemical, isoprene USA
Ultramarine Blue Powdered pigment AKROCHEM
AD -. .~
'~; `.
'" ' W094/01295 2 1 4 0 O O ~ -36- PCT/US93/~

Exam~le 6 White sidewall compositions were prepared by ' compounding the components shown in Table XIII using the mix cycle shown in Example 4. Copolymer G was a ¦
brominated copolymer of isobutylene and para- ?
methylstyrene containing 7.5 wt.% para-methylstyrene moieties and 2 wt.% bromine. Composition 6-l was a control composition prepared from ethylene-propylene-diene rubber (Vistalon~6505) blended with chlorinated butyl rubber (Chlorobutyl 1066).

TABLE XIII

Com~osition ~o. 6-1 6-2 6-3 6-4 6-5 6-6 6-7 6-8 C~lorobutyl 1066 60 VistalonO6505 20 Copolymer G - 40 40 40 50 60 35 35 Natural Rubber 20 60 60 60 50 40 65 65 Stearic Acid 2 2 2 ~2 2 2 2 2 Ultra Marine Blue0.40.4 0.4 0.4 0.4 0.4 0.4 0.4 Sunolite 240 Wax 1 - - - - - - -Escorez 1102 4 4 4 4 4 4 4 4 Zinc Oxide 5 3 3 3 3 3 3 3 Zinc Stearate Sulfur 0.80.3 0.2 0.2 0.2 0.3 0.2 0.2 }
Vultac #5 1.31.0 1.1 1.0 1.0 1.3 1.2 1.0 MBTS 1.01.3 1.3 1.2 1.3 1.3 1.2 l.O

The tire sidewall compositions of Table XIII were tested for various properties. The results of the tests are shown in-Table XIV.

~i3Lr 1'~
C~ Jns ?~~oe~ius ~ooney Scorc~, -2.~ 11.l 11.6 11., 12.4'2.1 1.6 i35'C-min .o - -~ pt. Rise '21 C-min to 22.8 21.9 20.7 19.8 18... 18.9 19.9 21.,3 5 pt. Rise ~ooney 51 46 t8 47 48 53 54 50 Visc:~sity ~IL - 1+4 ~alOOC ~-Rheometer 3-ARC
- @150-C
MH-ML, dN-m 29.0 31.8 30.0 31.0 il.O 28.0 27.8 30.2 t'90, min 26.; 26.3 26.5 27.1 26.~ 26.1 25.6 26., al60 C
M~-b~L, dN-m 35.~ 36._ ,0.0 33.~ 30.8 37.2 35.0 30.~ -'90, ~ . '8.3 1~.8 15.8 12.9 '5.~ 16.8 '5.0 ~~.3 ;, ^ure ~-~2er~~es EIardness, Shore ~ 60 54 ~3 55 54 53 51 5;
300% Madulus ~
MPa 4.~ ~.7 6.g 6.6 6.3 7.3 5.8 5. -Tensile, ~a 9.9 17.3 17.0 16 8 14.' 14.8 18.5 16.
% ~lonaation 690 620 590 ~90 580 ~540 650 650 Dynamic Ozone Sli~ht 20% ~xl._racKing -~ -lOOo~rlm at 200 EIours .o C-ac~c ;00- 300~, 300+ 300- 300 300l hrs 300--~ ~ Static Ozone Bent loop --lOOppnm Hours ro Crac3c 300+ 300+ 300+ 300- 300+ 300~ 300~ 300-Outdoor FlexSli~At DeMattiai Crac~cin~
-Pierced at 200 Hours .o Crac~c 500+ 500+ ~00+ 500+ 500+ 500+ hrs 500-Weatherometer Hours to Crac.~ 600+600+600+ 600+ 600+ 600+ 500+ 600+

Die 3 ~ z--, ~n/M
@RT(-~ 32.7 28.9 31.7 25.4 27.1 24.9 20.8 20., ; @lOO'C ~2.8 26.g 22.6 22.7 '9.8 15.g 19.~ 7.
(1) R~ = Room ~emperature .'`.MENGED S'r.EEl 21~000~

`
~L-~ .7 - r~= ' -Cured Adhesion KN/m @RT ~o S21 12 7 lO q 17 0 i6 i~ , 10 8 11 1 '' 2 Carcass 10 2 8 8 9 7 8 ~ 9 13 7 9 1 ~ 4 Coverstrip 10 9 9 7 18 / i6 4 ~ i8 2 q 6 9 3 ~100 C =o Sel~ 2 5 13 - i3 0 '2 8 7 26 8 8 7 ~ 4 -Carcass 1 6 4 , 9 7 q 5 9 65 1 ~ _ 6 0 Cove_s.~ip 1 4 1 ~ ~ 2 ~ 9 1 5 6 ~ 5 ~ 2 ~n ddition a Green S~- ? Tac~ tes_ was pe_-~rmed ,~
c3moa_-ng the conl~ol comoosition above with ~he .wo expe-imenla~ composi_ions one contz~ning ~ 60/40 ~lend of cooolymers wi.h natu,al -ubber and .h~ other -ontzining 35/6~ _lend or copolymers wi_h natural ~ubber ~he resul-s werQ as follows Con.~ol 60/40 31end 35/6~ 31end (KN/m~ ,_0 :
SelC
~RT 0 053 0 263 0 543 r om the date shown ln Ta~ie XIV -white sidewall comoosi~ions of the inven~ion exnl~it superior proper.ies in ~he areas of green tac~, cured adhesion and Die B
te~ch .hus the control withou~ sacri'icing performances in othe~ prooerties AMENDE~ S~lE~T

Claims (11)

Claims:

1. A white sidewall tire composition comprising a brominated copolymer of isobutylene and paramethylstyrene, natural rubber, non-black filler, cross-linking agent, pigment curative, and resin characterized in that zinc stearate is employed as a cross-linking agent together with sulfur at a zinc stearate to sulfur ratio or 1:0.3 to 1:0.2.

2. The composition of claim 1 wherein said sulfur is present in an amount less than 1.0 phr, preferably 0.2-0.3 phr.

3. The composition of claim 1 or 2 wherein said non-black filler and pigment are present in an amount of 57-90 phr.

4. The composition of claim 3 wherein said non-black filler and pigment comprise 25-45 phr of TiO2 and 32-45 phr clay.

5. The composition of any of claims 1 - 4 wherein said brominated copolymer of isobutylene and paramethylstyrene is present in an amount of 35-50 phr and said natural rubber is present in an amount of 50-65 phr.

6. A white sidewall composition characterized by comprising 35-50 phr brominated copolymer of isobutylene and paramethylstyrene, 65-50 phr natural rubber and curatives consisting of a combination or stearic acid, zinc stearate, sulfur, zinc oxide, alkyl phenol disulfide and benzothiazyidisulfide.

7. The composition of claim 6 wherein said sulfur is present in an amount less than 1.0 phr, preferably 0.2 - 0.3 phr.

8. The use of a selection of curatives consisting of stearic acid, zinc stearate, sulfur, zinc oxide, alkyl phenol disulfide and benzothiazyldisulfide for the purpose of improving Die B tear and adhesion properties in white side wall tire compositions based on the combination of a brominated copolymer of isobutylene and paramethylstyrene and natural rubber.

9. The use of claim 8 wherein said sulfur is present in an amount less than 1.0 phr and said stearic acid is present in an amount greater than 1 phr.

10. The use of claim 9 wherein sulfur is present in an amount of 0.2 - 0.3 phr.

11. The use of claim 10 wherein said stearic acid is present in an amount of 2 phr.