Background

Butyl rubber and related polymers are generally derived from at least one isoolefm monomer and at least one copolymerizable monomer. Commercial butyl rubbers comprise a major portion of isoolefm and a minor amount of a conjugated multiolefm. One example of butyl rubber is poly(isobutylene-co-isoprene), or IIR, which has been prepared since the 1940's through random cationic copolymerization of isobutylene with small amounts of isoprene. The backbone structure of IIR, which is mostly comprised of polyisobutylene segments, imparts superior air impermeability, oxidative stability and excellent fatigue resistance to this material (see, for example, Chu, C.Y. and Vukov, R., Macromolecules, 18, 1423-1430, 1985).

In the production of articles made of rubber, curatives are used to toughen or harden the rubber. To achieve an appropriate mechanical properly, curatives, often in the form of small molecules, metal oxides, or metal ions, are added to uncured rubbers (this process is also known as compounding) followed by compression molding at an elevated temperature. During the compression molding process, the curatives react to form crosslinks between the polymer chains of the rubber leading to a cured rubber article with meaningful mechanical properties. Such properties include good tensile strength combined with a high elongation and an appropriate compression set.

Conventional cure systems include a sulfur cure, a zinc oxide cure and a peroxide cure. In all three systems the curatives that are added, or byproducts thereof, remain in the cured rubber article after curing. The curatives, or byproducts thereof, could potentially leach out of the article and contaminate the user or the surroundings of the cured rubber article. For example, sulfur-cured rubber articles contain organic or inorganic sulfides and peroxide -cured rubber articles contain alcohols or ketones (and potentially unreacted coagents) that pose the risk of leaching and contaminating adjacent materials. This risk is particularly relevant to the variety of pharmaceutical and consumer goods applications of cured rubber articles (i.e. the sterile solution next to a pharmaceutical stopper or the stopper part of a syringe; the baby food next to the sealing ring of a jar lid).

Accordingly, there remains a need for a "clean" process for curing butyl rubber which reduces or eliminates the use of curatives in curing systems thereby reducing the potential for contaminant leaching. In addition, the use of fillers in butyl rubber often results in hard polymers with a density greater than that of water. It would be desirable in many applications to obtain a filled cured elastomer compound with lower density than conventionally available, for examples less than 1 g/cm ³ . It would be particularly advantageous if this low density compound could be obtained without the use of additional blowing agents or foaming agents, as these can serve as sources of contamination to the finished product. Finally, it would be desirable to obtain a filled cured rubber compound with a low durometer for use in certain sealing applications. There remains a need for filled cured compounds with these low density, low durometer and/or clean characteristics.

Summary of the Invention

According to the present invention, there is provided a process for preparing a filled cured copolymer comprising at least the steps of:

a) providing at least one azidated copolymer comprising repeating units derived from at least one isoolefin monomer, repeating units derived from at least one copolymerizable monomer comprising a multiolefin monomer, divinyl aromatic monomer, alkyl substituted vinyl aromatic monomer, or mixtures thereof and one or more azide groups substituted onto a plurality of the repeating units derived from the at least one copolymerizable monomer; b) mixing at least one filler with said azidated copolymer to obtain a compound; and, c) heating said compound at a temperature suitable to effect curing by decomposition of the azide groups.

According to another aspect of the invention, there is provided a filled, cured azidated copolymer comprising repeating units derived from at least one isoolefin monomer, repeating units derived from at least one copolymerizable monomer comprising a multiolefin monomer, divinyl aromatic monomer, alkyl substituted vinyl aromatic monomer, or mixtures thereof and one or more azide groups substituted onto a plurality of the repeating units derived from the at least one copolymerizable monomer.

In one embodiment the compound is cured by heating to a temperature of from 100°C to 250°C. In another embodiment the compound is cured by heating to a temperature of from 130°C to 220°C. In yet another embodiment the compound is cured by heating to a temperature ofl60°C to 200°C.

In one embodiment the process is conducted in the absence of additional curing agents or curatives. For example, the process may be conducted in the absence of peroxide curing agents, sulfur curing agents, zinc oxide curing agents, resin-based curing agents, etc. In one embodiment the filler is selected from the group consisting of silica, silicates, clay, mica, talc, gypsum, metal oxides, metal hydroxides, metal carbonates, starch wood, glass fibers, glass fiber products, glass microspheres and carbon black. In another embodiment the filler is selected from the group consisting of silica, silicates, clay, mica, talc, gypsum.

The filler may have an aspect ratio of greater than or equal to 1 :3. The filler may comprise a carbon black with an aspect ratio of greater than or equal to 1 :3.

The azide groups may be distributed throughout the repeating units derived from the at least one copolymerizable monomer. The azide groups may be attached to the repeating units derived from the at least one copolymerizable monomer through a C-N bond. The filled cured copolymer may have a density of less than 1 g/cm ³ . The ratio between the actual density of the copolymer and the calculated density of the copolymer may be less than 1, for example in the range of from 0.20 to 0.99, 0.30 to 0.95, 0.40 to 0.90 or a range comprising any combination of values selected from the following values: 0.99, 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, 0.55, 0.50, 0.45, 0.40, 0.35, 0.30, 0.25, 0.20.

The filled cured azidated copolymer may contain micropores. The micropores may be created in situ during curing via release of nitrogen from the azide groups. The micropores may be created without the use of foaming agents, blowing agents, or additional blown gases. The micropores may have a size in the range of from 2 μηι to 100 μηι, in the range of from 2 μηι to 70 μηι, or in the range of from 5 μηι to 50 μηι. The micropores may contain a gas comprising equal to or greater than 80% nitrogen gas.

The filled cured azidated copolymer may exhibit one or more of reduced density, reduced durometer, or reduced leachable/extractable components as compared with conventional cured filled butyl rubber compounds created without micropores.

Detailed Description of the of the Invention

An azidated copolymer for use in the present invention is created for example by reacting a copolymer comprising repeating units derived from at least one isoolefin monomer and repeating units derived from at least one olefinic monomer with an azidation reagent to functionalize the copolymer with at least one azide group. The azide groups are preferably located on the repeating units derived from the at least one olefinic monomer. The azide groups are preferably distributed throughout the repeating units derived from the at least one olefmic monomer and not merely located on the ends of the copolymer. The azide groups may be randomly distributed. The azidated copolymer is then mixed with at least one filler, and then cured e.g. by heating at a suitable temperature.

It has been found unexpectedly that heating azidated copolymer even in the absence of any curatives, results in a cure of the copolymer to a commercially useful form. The omission of curatives in the curing process means that the cured polymer article is free from the risk of contaminant leaching.

The term "curative" as used herein encompasses any non-polymeric substance or agent that effects cross-linking between polymer chains. The term "curing agent" may also be used. Examples of conventional curatives include sulfur curatives, zinc oxide curatives and peroxide curatives. A further advantage of the process of the present invention is that since no curatives are used, curing can, in one embodiment, be achieved in the absence of additives such as coagents, cure accelerators and cure retarders.

It has further been found that azidated copolymers in the presence of at least one filler form foamed material even in the absence of any blowing agent and/or foaming agent. This further reduces contaminant leaching. Thus, a foamed cured filled azidated copolymer is provided.

The terms "blowing agent" and "foaming agent" as used herein encompass any non-polymeric substance or agent that generates low volatility compounds and gases upon heating or facilitates the introduction of externally produced gases.

The term "contaminant" as used herein encompasses any excessive cure agents or blowing agent or foaming agent or any of their (at standard conditions) non-gaseous reaction products that remain in the cured polymer after the curing process

Any heating methods and/or devices that are known by persons skilled in the art to be suitable for heating uncured polymers, rubbers or rubber compounds can be used in the present invention to heat the azidated copolymers. In one embodiment, the azidated copolymer is heated at a temperature of from about 100°C to about 250°C to cause curing. In one embodiment, the azidated copolymer is heated at a temperature of from about 130°C to about 220°C to cause curing. In one embodiment, the azidated copolymer is heated at a temperature of from about 160°C to about 200°C to cause curing. In one embodiment, the azidated copolymer is heated for a time of at least 5 minutes. Other suitable times and conditions may be selected by those of skill in the art. The azidated copolymers of the present invention comprise repeating units derived from at least one isoolefin monomer and repeating units derived from at least one copolymenzable monomer, wherein one or more of the repeating units derived from the at least one copolymerizable monomer comprise at least one, preferably one azide group. In one embodiment, an azide group is linked to a carbon atom of the repeating units derived from the at least one copolymerizable monomer through a C-N bond.

In one embodiment, the average number of azide groups per copolymer chain is greater than 2 or more, alternatively 3 or more, alternatively 4 or more, alternatively 5 or more alternatively 10 or more.

In one embodiment, the nitrogen content of the azidated copolymer is from 0.02 to 5 wt.-%, preferably 0,1 to 2 wt.-%. The at least one isoolefin monomer used in preparing the azidated copolymer of the present invention is not limited to a particular isoolefin. In one embodiment, the suitable isoolefins have from 4 to 7 carbon atoms, such as isobutylene, 2 -methyl -1 -butene, 3 -methyl- 1 -butene, 2-methyl-2- butene, 4-methyl-l -pentene and mixtures thereof. A particularly prefened isoolefin comprises isobutylene (isobutene).

The at least one copolymerizable monomer used in preparing the azidated copolymer of the present invention may comprise olefmic monomers, for example a multiolefin monomer, a divinyl aromatic monomer, alkyl substituted vinyl aromatic monomer, or mixtures thereof. The copolymerizable multiolefin monomers used in preparing the azidated copolymers of the present invention are not limited to a particular multiolefin monomer. Suitable multiolefms have from 4 to 14 carbon atoms. One class of suitable multiolefms comprises conjugated dienes. Examples of such multiolefms include isoprene, butadiene, 2-methylbutadiene, 2,4- dimethylbutadiene, piperyline, 3-methyl-l ,3-pentadiene, 2,4-hexadiene, 2-neopentylbutadiene, 2- methyl- 1 , 5 -hexadiene, 2,5-dimethyl-2,4-hexadiene, 2-methyl-l ,4-pentadiene, 4-butyl-l,3- pentadiene, 2,3 -dimethyl -1,3 -pentadiene, 2,3-dibutyl-l,3-pentadiene, 2-ethyl-l,3-pentadiene, 2- ethyl- 1,3 -butadiene, 2-methyl-l ,6-heptadiene, cyclopentadiene, methylcyclopentadiene, cyclohexadiene, 1 -vinyl -cyclohexadiene and mixtures thereof. In one embodiment, the conjugated diene comprises isoprene.

Alkyl substituted vinyl aromatic monomers and divinyl aromatic monomers useful in the present invention can have an aromatic core such as benzene, naphthalene, anthracene, phenanthrene or biphenyl.

In one embodiment, the divinyl aromatic monomer used in the present invention is vinyl styrene. In one embodiment, the alkyl-substituted vinyl aromatic monomer is a Ci-C ₄ alkyl substituted styrene. In one embodiment, Ci-C ₄ alkyl substituted styrene includes, for example, o-methyl styrene, ^-methyl styrene, or w-methyl styrene.

In one embodiment the azidated copolymer of the present invention comprises copolymers of isoolefm and a multiolefm (hereinafter referred to as isoolefm-multiolefin copolymers).

In such an embodiment, one or more of the repeating units derived from the multiolefm monomers comprise an azide moiety. In one embodiment one or more of the repeating units derived from the multiolefm monomers comprise an allylic azide moiety. In one embodiment the azidated copolymer of the present invention comprises copolymers of isobutylene and isoprene. In one such embodiment the repeating units derived from isoprene comprise allylic azide moiety.

In one embodiment, the monomer mixture used in preparing the isoolefm-multiolefin copolymer comprises from about 80% to about 99.5% by weight of at least one isoolefm monomer and from about 0.5% to about 20% by weight of at least one multiolefm monomer. In one embodiment, the monomer mixture comprises from about 83% to about 98% by weight of at least one isoolefm monomer and from about 2.0% to about 17% by weight of a multiolefm monomer. In one embodiment, the isoolefm-multiolefin copolymer comprises at least 0.5 mol% repeating units derived from the multiolefm monomers. In one embodiment, the repeating units derived from the multiolefm monomers are at least 0.75 mol%. In one embodiment, the repeating units derived from the multiolefm monomers are at least 1.0 mol%. In one embodiment, the repeating units derived from the multiolefm monomers are at least 1.5 mol%. In one embodiment, the repeating units derived from the multiolefm monomers are at least 2.0 mol%. In one embodiment, the repeating units derived from the multiolefm monomers are at least 2.5 mol%. In one embodiment, the isoolefm-multiolefin copolymer comprises at least 3.0 mol% repeating units derived from the multiolefm monomers. In one embodiment, the repeating units derived from the multiolefm monomers are at least 4.0 mol%. In one embodiment, the repeating units derived from the multiolefm monomers are at least 5.0 mol%. In one embodiment, the repeating units derived from the multiolefm monomers are at least 6.0 mol%. In one embodiment, the repeating units derived from the multiolefm monomers at least 7.0 mol%.

In one embodiment, the repeating units derived from the multiolefm monomers are from about 0.5 mol % to about 20 mol %. In one embodiment, the repeating units derived from the multiolefm monomers are from about 0.5 mol % to about 8 mol %. In one embodiment, the repeating units derived from the multiolefm monomers are from about 0.5 mol % to about 4 mol %. In one embodiment, the repeating units derived from the multiolefm monomers are from about 0.5 mol % to about 2.5 mol %. The preparation of a isoolefin-multiolefin copolymer having at least about 2.0 mol % repeating units derived from at least one multiolefm monomer is described, for example, in Canadian Patent No. 2,418,884, which is incorporated herein by reference in its entirety.

In one embodiment, the azidated copolymers of the present invention comprise copolymers of at least one isoolefin and one or more alkyl substituted aromatic vinyl monomers. In such an embodiment, one or more of the repeating units derived from the aromatic vinyl monomers comprise the azide moiety.

In one embodiment, the azidated copolymers of the present invention comprise repeating units derived from isobutylene and ^-methyl styrene, wherein one or more repeating units derived from the /7-methyl styrene bear a benzylic azido group.

In one embodiment, the copolymers of isoolefms monomers and alkyl aromatic vinyl monomers comprise repeating units derived from the alkyl aromatic vinyl moieties from about 0.5 weight percent to about 25 weight percent of the copolymer. In one embodiment, the alkyl aromatic repeating units are from about 1 to about 20 weight percent. In one embodiment, the alkyl aromatic repeating units are from about 2 to about 10 weight percent.

In one embodiment, the azidated copolymer of the present invention comprises copolymers of isobutylene and ^-methyl styrene, as described in U.S. Patent. No. 5,013,793, which is incorporated herein by reference in its entirety. In one embodiment, the azidated copolymer of the present invention comprises copolymers of at least one isoolefm, one or more multiolefm monomers, and one or more alkyl substituted aromatic vinyl monomers. In such an embodiment, one or more units derived from the multiolefm monomers comprise an allylic azide moiety and/or one or more units derived from said the substituted aromatic vinyl monomers comprise an azide alkyl moiety.

In one embodiment, the azidated copolymer of the present invention comprises a terpolymer of isobutylene, isoprene and alkyl substituted styrene, wherein one or more repeating units derived from the isoprene have an allylic azido moiety and/or one or more repeating units derived from said /7-methyl styrene have a benzylic azido group.

In one embodiment, the azidated copolymer comprises terpolymers of isobutylene, isoprene, and p- methyl styrene as described in U.S. Patent. No. 6,960,632, which is incorporated herein by reference in its entirety.

In one embodiment, the monomer mixture used in preparing the copolymer of isoolefm, the multiolefm and the alkyl substituted aromatic vinyl monomers comprise from about 80% to about 99% by weight of isoolefm monomers, from about 0.5% to about 5% by weight the multiolefm monomers, and from about 0.5% to about 15% by weight of the alkyl substituted aromatic vinyl monomers. In one embodiment, the monomer mixture comprises from about 85% to about 99% by weight of isoolefm monomer, from about 0.5% to about 5% by weight the multiolefm monomer and from about 0.5% to about 10% by weight alkyl substituted aromatic vinyl monomer.

In one embodiment, the azidated copolymer of the present invention comprises terpolymers of isobutylene, isoprene, and divinyl styrene, as described in U.S. Patent. No. 4,916,180, which is incorporated herein by reference in its entirety.

The mixture used to produce multiolefm butyl rubber polymer may further comprise a multiolefm cross-linking agent. The term cross-linking agent is a term known to persons skilled in the art and is understood to denote a compound that causes chemical cross-linking between the polymer chains as opposed to a monomer that will add to the chain. Examples of suitable cross -linking agents include norbornadiene, 2-isopropenylnorbornene, 2-vinyl-norbornene, 1,3,5-hexatriene, 2-phenyl- 1,3-butadiene, divinylbenzene, diisopropenylbenzene, divinyltoluene, divinylxylene and Ci to C ₂ o alkyl-substituted derivatives thereof. More preferably, the multiolefm cross-linking agent is divinyl-benzene, diiso-propenylbenzene, divinyltoluene, divinyl-xylene and Q to C ₂ o alkyl-substituted derivatives thereof, and/or mixtures of the compounds given. Most preferably, the multiolefm cross-linking agent comprises divinyl-benzene and diiso-propenylbenzene. In one aspect of the present invention, the azidated copolymer is a star branched copolymer linked to a branching moiety In one embodiment, the branching moiety is a polymeric branching moiety.

The polymeric branching moiety useful in the formation of the star branched polymer of the present invention includes polymers and copolymers comprising functional groups capable of copolymerizing or forming a covalent bond with the active chain end of a growing polymeric chain of the copolymer used in the formation of the halogenated polymer. The functional group comprises cationically active unsaturation. Non— limiting examples of such polymeric moieties include polydienes, partially hydrogenated polydienes, such as polybutadiene, polyisoprene, polypiperylene, natural rubber, styrene-butadiene rubber, ethylene-propylene diene monomer rubber, styrene-butadiene-styrene and styrene-isoprene-styrene block copolymers. Star branched polymers of the present invention can be prepared by first linking the polymeric chains with the branching moiety followed by halogenations of the polymeric chains. Preparation of starch branch polymers is described in U.S. Patent No. 5,182,333 and European Publication No., 0 320 263, which are incorporated herein by reference in their entirety. Preparation of Azidated copolymers

The azidated copolymers of the present invention can be prepared by reacting the copolymer of at least one isoolefin and at least one copolymerizable monomer with an azidation reagent. This reaction is referred to as azidation reaction. The azidation reagent can be an azide salt, a covalent azide compound, or mixtures thereof.

Examples of suitable covalent azide compounds include, but are not limited to, trimethylsilyl azide (Me ₃ SiN ₃ or TMSN ₃ ), p-toluene sulfonyl azide or tosyl azide (TsN ₃ ), trifluoromethanesulfonyl azide and hydrogen azide (HN ₃ ).

Suitable azide salts for use in the azidation reaction include both organic and inorganic azide salts, as would be known and understood by persons skilled in the art. Examples of suitable azide salts include, but are not limited to, sodium azide (NaN ₃ ), potassium azide (KN ₃ ), ammonium azide (NH ₄ N ₃ ), and tetraalkylammonium azide, such as, tetrabutylammonium azide (TBAN ₃ ).

In one embodiment, the azidation reaction is carried out by reacting the azidation reagent with a copolymer of isoolefin and at least one copolymerizable monomer, wherein one or more of the repeating units derived from the copolymerizable monomer are functionalized with one or more oxygen containing functional groups.

In one embodiment the oxygen containing functional group is an epoxide group.

In one embodiment the copolymer comprising the epoxide group is a copolymer of at least one isoolefm monomer and one or more multiolefin monomers, or divinyl aromatic monomer, or both. Non-limiting examples of these monomers are as discussed above. In one embodiment, the azidation reaction is carried out by reacting the azidation reagent with a copolymer of an isoolefm and at least one copolymerizable monomer, wherein the copolymer is functionalized with one or more leaving groups. In one embodiment, one or more of the repeating units derived from the at least one copolymerizable monomer are functionalized with the leaving group.

The leaving group can be halogen, amine, PR ₃ , ether, diazonium, oxonium, nonaflate, triflate, fluorosulfonate, tosylate, mesylate, conjugate acid of an alcohol, conjugate acid of an ether, nitrate, phosphate, SR' ₂ , ester, acid anhydride, phenoxide, alcohol, carboxylic acid, or mixtures thereof. Preferably, the leaving group is halogen such as chloride or bromide, amine, PR ₃ , or mixtures thereof. Ever more preferably the leaving group is bromide.

In one embodiment, substantially all of the repeating units derived from the at least one copolymerizable monomer are covalently bound to leaving groups. In one embodiment, only some of the repeating units derived from the at least one copolymerizable monomer are covalently bound to leaving groups.

In one embodiment the copolymer comprising the leaving group is a copolymer of at least one isoolefm monomer and a multiolefin monomer, a divinyl aromatic monomer, an alkyl substituted vinyl aromatic monomer, or mixtures thereof. Non-limiting examples of these monomers are as discussed above.

In one embodiment the leaving group is a halogen. In one embodiment, a halogenated copolymer used in the formation of the azide functionalized copolymer of the present invention comprises at least one allylic halogen moiety, at least one halo alkyl moiety, or both. In one embodiment, the halogenated copolymer comprises repeating units derived from at least one isoolefm monomer and repeating units derived from one or more multiolefm monomers. In such an embodiment, one or more of the repeating units derived from the multiolefm monomers comprise an allylic halogen moiety. In one embodiment, the halogenated copolymer is halogenated butyl rubber polymer or halobutyl polymer.

In one embodiment, the halogenated polymer is obtained by first preparing a copolymer from a monomer mixture comprising one or more isoolefins and one or more multiolefms (also referred to as multiolefm butyl rubber polymer), followed by subjecting the resulting copolymer to a halogenation process to form the halogenated polymer. Halogenation can be performed according to the process known by those skilled in the art, for example, the procedures described in Rubber Technology, 3rd Ed., Edited by Maurice Morton, Kluwer Academic Publishers, pp. 297 - 300 and further documents cited therein.

During halogenation, some or all of the multiolefm content of the copolymer is converted to units comprising allylic halides. The total allylic halide content of the halogenated polymer cannot exceed the starting multiolefm content of the parent copolymer. When the multiolefm butyl rubber polymer is halogenated, there may then be both allylic halides, which are derived from the original multiolefm content, and non -halogenated multiolefms present within the same polymer, especially when high multiolefm butyl rubber polymers are used as the starting material for the halobutyl polymer. In one embodiment, the halogenated isoolefm-multiolefin coplolymer may comprise at least about 0.1 mol % allylic halides and/or repeating units derived from allylic halides. In one embodiment, the halogenated isoolefm-multiolefin coplolymer may comprise at least about 0.2 mol %, allylic halides and/or repeating units derived from allylic halides. In one embodiment, the halogenated isoolefm-multiolefin coplolymer may comprise at least about 0.5 mol % allylic halides and/or repeating units derived from allylic halides. In one embodiment, the halogenated isoolefm- multiolefin coplolymer may comprise at least about 0.8 mol % allylic halides and/or repeating units derived from allylic halides. In one embodiment, the halogenated isoolefm-multiolefin coplolymer may comprise at least about 1.0 mol % allylic halides and/or repeating units derived from allylic halides.

In one embodiment, the halogenated copolymer of the present invention comprises copolymers of at least one isoolefm and one or more alkyl substituted aromatic vinyl monomers. In such an embodiment, one or more of the repeating units derived from the aromatic vinyl monomers comprise a halo alkyl moiety.

In one embodiment, these type of halogenated polymers are obtained by first preparing a copolymer from a monomer mixture comprising one or more isoolefms and one or more alkyl substituted aromatic vinyl monomers, followed by subjecting the resulting copolymer to a halogenation process to form the halogenated polymer. During halogenation, some or all of the alkyl groups of the repeating units derived from the aromatic vinyl monomers are halogenated. In one embodiment, the halogenated polymers of the present invention comprise co-polymers of isoolefm and methyl styrene, wherein after halogenations, methyl group of some or all of the repeating units derived from the methyl styrene are converted to benzylic halides. The total benzylic halide content of the halobutyl polymer cannot exceed the starting styrenic content of the parent butyl compound. In one embodiment, the copolymers of isoolefms monomers and alkyl aromatic vinyl monomers comprise repeating units derived from the alkyl aromatic vinyl moieties from about 0.5 weight percent to about 25 weight percent of the copolymer. In one embodiment, the alkyl aromatic repeating units are from about 1 to about 20 weight percent. In one embodiment, the alkyl aromatic repeating units are from about 2 to about 10 weight percent.

In one embodiment, the halogenated polymer of the present invention comprises copolymers of isobutylene and ^-methyl styrene, as described in U.S. Patent. No. 5,013,793, which is incorporated herein by reference in its entirety. In one embodiment, the halogenated polymer of the present invention comprises copolymers of isobutylene and ^-methyl styrene having styrene content from about 5% to 7% and halogen content from about 0.5 to 1.5%.

In one embodiment, the halogenated polymer of the present invention comprises copolymers of at least one isoolefm, one or more multiolefm monomers, and one or more alkyl substituted aromatic vinyl monomers. In such an embodiment, one or more units derived from the multiolefm monomers comprise an allylic halogen moiety and/or one or more units derived from the the substituted aromatic vinyl monomers comprise a halo alkyl moiety.

These type of halogenated polymers can be formed by first preparing a copolymer from a monomer mixture comprising the isoolefm, the multiolefm and the alkyl substituted aromatic vinyl monomers, followed by subjecting the resulting copolymer to halogenation process to halogenate the repeating units derived from the multiolefm monomers and/or the alkyl group of the repeating units derived from aromatic vinyl monomers. In one embodiment, the monomer mixture used in preparing the copolymer of isoolefm, the multiolefin and the alkyl substituted aromatic vinyl monomers comprise from about 80% to about 99% by weight of isoolefm monomers, from about 0.5% to about 5% by weight the multiolefin monomers, and from about 0.5% to about 15% by weight of the alkyl substituted aromatic vinyl monomers. In one embodiment, the monomer mixture comprises from about 85% to about 99% by weight of isoolefm monomer, from about 0.5% to about 5% by weight the multiolefin monomer and from about 0.5% to about 10% by weight alkyl substituted aromatic vinyl monomer. In one embodiment, the halogenated polymer comprises terpolymers of isobutylene, isoprene, and /7-methyl styrene as described in U.S. Patent. No. 6,960,632, which is incorporated herein by reference in its entirety.

In one embodiment, the amount of azidation reagent reacted with the copolymer functionalized with the leaving group or the oxygen containing functional groups to produce azidated copolymer can range from about 50 to about 0.05 molar equivalents, preferably about 15 to about 0.05 molar equivalents, more preferably about 7 to about 0.05 molar equivalents and even more preferably about 1.5 to about 0.1 molar equivalents, based on the total molar amount of functional groups in the copolymer.

The azidation reaction to synthesize azidated copolymer can be carried out in solution or in bulk (i.e. in the absence of a solvent).

When the reaction is carried out in solution, the process comprises the step of adding the starting copolymer and the azidation reagent to a solvent to form a reaction mixture.

Suitable solvents include, but are not limited to, tetrahydrofuran (THF), dichloromethane, chlorobenzene, dichlorobenzenes, toluene and chloroform. The addition of a second solvent to the reaction mixture, such as Ν,Ν-dimethylformamide (DMF), can be used to facilitate the solubilization of the azidation reagent and it is particularly helpful to add DMF when using NaN ₃ .

Persons skilled in the art would know how to control the ratio between the first solvent and the additional second solvent to avoid unwanted polymer precipitation.

In one embodiment, the reaction between the starting copolymer and the azidation reagent is carried out in bulk using conventional mixers. Examples of suitable mixers include, but are not limited to, a Banbury mixer, a miniature internal mixer (such as a Haake or Brabender mixer), a two roll mill mixer, and extruders (such as single screw and twin screw extruders). In one embodiment, when the azidation reaction is carried out in solution, the starting copolymer can be present in an amount of at least about 0.5%, preferably at least about 2%, more preferably at least about 4%, and even more preferably at least about 10% by weight of the reaction mixture.

In one embodiment the azidation reaction is carried out at room temperature and in solution.

Without limitation to a particular hypothesis, it is considered that the synthesis of azidated copolymer, when a halogenated copolymer is reacted with an azidation reagent (such as azide salt), proceeds by nucleophilic displacement of a halogen atom by the azido group derived from the azidation reagent. Without limitation to a particular hypothesis, it is considered that when the halogenated polymer is a terpolymer comprising repeating units derived from an isoolefin and two different copolymerizable monomers, the nucleophilic displacement may occur only to the halogens of the halogenated units of the copolymerizable monomer.

In one embodiment, azidated and non-azidated (e.g. halogenated) units may both be present in the same azidobutyl polymer.

In one embodiment, the number-average molecular weight of the azidated copolymer is greater than 20000 g mol ¹ , in one embodiment, the number-average molecular weight of the azidated copolymer is greater than 30000 g mol ^"1 , in one embodiment, the number-average molecular weight of the azidated copolymer is greater than 40000 g mol ^"1 , in one embodiment, the number-average molecular weight of the azidated copolymer is greater than 50000 g mol ^"1 , in one embodiment, the number-average molecular weight of the azidated copolymer is greater than 60000 g mol ^"1 .

In one embodiment, the azidated copolymer shows a thermal self-curing behavior.

In one embodiment, the Mooney viscosity (ML 1+8 at 125 °C, ASTM 1646) of the azidated copolymer is greater than 5, In one embodiment, the Mooney viscosity of the azidated copolymer is greater than 10, In one embodiment, the Mooney viscosity of the azidated copolymer is greater than 15, In one embodiment, the Mooney viscosity of the azidated copolymer is greater than 20.

In one embodiment, when subjected to characterisation with a Moving Die Rheometer and conforming to ASTM D5289, 1 °arc, 1.7 Hz, 200 °C, 30 min test time, the azidated copolymer shows an increase in torque in the range of 0.1 - 30 dNm, preferably 0.2 - 20 dNm, more preferably 0.5 - 15 dNm. In one embodiment, when subjected to characterisation with a Moving Die Rheometer and conforming to ASTM D5289, 1 °arc, 1.7 Hz, 200 °C, 30 min test time, the azidated copolymer shows an increase in torque (M _h - M) in the range of 0.1 - 30 dNm, preferably 1 - 20 dNm, more preferably 2 - 15 dNm.

In one embodiment, when subjected to characterisation with a Moving Die Rheometer and conforming to ASTM D5289, 1 °arc, 1.7 Hz, 200 °C, 30 min test time, the azidated copolymer shows an increase in torque (M _h - ) in the range of 0.1 - 30 dNm, preferably 1 - 20 dNm, more preferably 2 - 10 dNm. In one embodiment, when subjected to characterisation with a Moving Die Rheometer and conforming to ASTM D5289, 1 °arc, 1.7 Hz, 200 °C, 30 min test time, the azidated copolymer shows a miniumum torque ( ) in the range of 0.5 - 5 dNm, preferably 0.6 - 4 dNm, more preferably 0.7 - 3 dNm. In one embodiment, the azidated copolymer is derived from bromobutyl rubber, wherein a compound prepared according to ASTM D3985 containing 100 phr of said bromobutyl rubber, 40 phr of IRB #7 black (carbon black), 1 phr of stearic acid and 5 phr of zinc oxide shows M _L in the range of 1 - 10 dNm, M _H in the range of 8 - 25 dNm wherein M _L and M _H are determined according to ASTM D5289 at 160°C, 1° arc, 1.7 Hz die oscillation, 30 min running time, without preheat.

In one embodiment, the azidated copolymer is derived from chlorobutyl rubber, wherein a compound prepared according to ASTM D3985 containing 100 phr of said chlorobutyl rubber, 40 phr of IRB #7 black (carbon black), 1 phr of stearic acid and 5 phr of zinc oxide shows M _L in the range of 1 - 10 dNm, M _H in the range of 8 - 25 dNm wherein M _L and M _H are determined according to ASTM D5289 at 160°C, 1° arc, 1.7 Hz die oscillation, 30 min running time, without preheat.

In one embodiment, the azidated copolymer is derived from a brominated polymer comprising isobutylene and paramethylstyrene (BIMS), wherein a compound prepared according to ASTM D3985 containing 100 phr of said BIMS, 40 phr of IRB #7 black (carbon black), 1 phr of stearic acid and 5 phr of zinc oxide shows ML in the range of 1 - 10 dNm, MH in the range of 8 - 25 dNm wherein ML and MH are determined according to ASTM D5289 at 160°C, 1° arc, 1.7 Hz die oscillation, 30 min running time, without preheat.

The cured polymers according to the invention are filled i.e. contain at least one filler. Suitable fillers include silica, silicates, clay, mica, talc, gypsum, metal oxides, metal hydroxides, metal carbonates, organic fillers (e.g. starch or wood), glass fibers, glass fiber products, glass microspheres or carbon black. The at least one filler is preferably present and used in an amount of from 1 to 200 phr, preferably of from 1 to 120 phr, more preferably of from 1 to 80 phr.

In one embodiment, the filler is carbon black or modified carbon black. In one embodiment, the filler is reinforcing grade carbon black present at a level of from 10 to 150 phr, preferably 10 to 100 phr, of the composition, preferably from 30 to 120 phr, more preferably 40 to 80 phr. Useful grades of carbon black are described in RUBBER TECHNOLOGY 59-85 (1995) and range from Nl 10 to N990. More desirably, embodiments of the carbon black useful in, for example, tire treads are N229, N351, N339, N220, N234 and N110 provided in ASTM (D3037, D1510, and D3765). Embodiments of the carbon black useful in, for example, sidewalls in tires, are N330, N351, N550, N650, N660, and N762. Embodiments of the carbon black useful in, for example, innerliners or innertubes are N550, N650, N660, N762, N990, and Regal 85 (Cabot Corporation, Alpharetta, GA) and the like.

Modified carbon blacks may also be suitable as fillers. Such "modified carbon black" is disclosed in, for example, US 3,620,792; 5,900,029; and 6,158,488. The modified carbon black may comprise carbon black that has been subjected to treatment with a gas such as a nitrogen oxide, ozone, or other gas which may impart improved properties to the surface of the carbon black. The modified carbon black may also comprise, for example, a carbon black that has been contacted with a silanol-containing compound and/or a hydrocarbon radical such as an alkyl, aryl, alkylaryl and arylalkyl. The modified carbon black contacted with a silanol-containing compound can be prepared, for example, by contacting an organosilane such as an alkyl alkoxy silane with carbon black at an elevated temperature. Representative organosilanes include tetraakoxysilicates such as tetraethyoxysilicate. Alternatively, the modified carbon black can be prepared by co -fuming an organosilane and an oil in the presence of the carbon black at an elevated temperature. In yet another example preparing a modified carbon black, a diazonium salt can be contacted with the carbon black either with or without an electron source or with or without a protic solvent. Diazonium salts are known in the art and may be generated by contacting a primary amine, a nitrile and an acid (proton donor). The nitrile may be any metal nitrile, desirably a lithium nitrile, sodium nitrile, potassium nitrile, zinc nitrile, or some combination thereof, or any organic nitrile such as isoamylnitrile or ethylnitrile, or some combination of these.

As used herein, the term carbon black includes carbon black such as channel black, furnace black, thermal black, acetylene black, lamp black and the like. Reinforcing grade carbon black is most preferred. The typically used and recommended carbon blacks are those furnace blacks meeting ASTM designations (ASTM D 1765-1979) and falling into the following classes: N550 FEF, N650 GPF, N762 SRF and N683 APF. Among these, N650/683 and N762 are closely defined as standard blacks in ISO/DIN 6809. Several documents disclose the use of specific carbon black fillers. In U.S. Pat. No. 4,722,971, carbon black N650 is used in an amount of 140 phr. In U.S. Pat. No. 4,792,595, the use of 80 phr of "high abrasion furnace black" is disclosed. U.S. Pat. No. 3,884,993 teaches that 10-200 phr of carbon black, as a conventional filler, can be used to improve processability of rubber. GB 1 543 821 exemplifies the use of 70 parts "FEF black". GB 2 032 443 teaches that up to 300% by weight of fillers, including carbon black, can be used in improving processability of rubbery copolymers and exemplifies the use of a carbon black SEAST H.RTM. (TOKAI Carbon Co., Japan) in the amount of 67 parts by weight. The above documents are incorporated by reference herein in their entirety. Silicas include highly dispersable silicas, prepared e.g. by the precipitation of silicate solutions or the flame hydrolysis of silicon halides, with specific surface areas of 5 to 1000, preferably 20 to 400 m2/g (BET specific surface area), and with primary particle sizes of 10 to 400 nm; the silicas can optionally also be present as mixed oxides with other metal oxides such as Al, Mg, Ca, Ba, Zn, Zr and Ti; Silicates include synthetic silicates such as aluminum silicate and alkaline earth metal silicate; magnesium silicate or calcium silicate, with BET specific surface areas of 20 to 400 m2/g and primary particle diameters of 10 to 400 nm or natural silicates, such as kaolin and other naturally occurring silica;

Clays include natural clays, such as montmorillonite and other naturally occurring clays; organophilically modified clays such as organophilically modified montmorillonite clays (e.g.

Cloisite® Nanoclays available from Southern Clay Products) and other organophilically modified naturally occurring clays;

Further fillers include glass fibers and glass fiber products (matting, extrudates) or glass microspheres; metal oxides, such as zinc oxide, calcium oxide, magnesium oxide and aluminum oxide; metal carbonates, such as magnesium carbonate, calcium carbonate and zinc carbonate; metal hydroxides, e.g. aluminum hydroxide and magnesium hydroxide.

In one embodiment fillers may be present or used in any combination of the aforementioned fillers. In one embodiment, the fillers comprise high aspect ratio fillers.

As used herein the term "high aspect ratio" means an aspect ratio of at least 1 :3, whereby the aspect ratio is defined as the ratio of mean diameter of a circle of the same area as the face of the plate to the mean thickness of the plate. The aspect ratio for needle and fiber shaped fillers is the ratio of length to diameter. The fillers may include acircular or nonisometric materials with a platy or needle-like structure. Preferable high aspect ratio fillers have an aspect ratio of at least 1 :3, more preferably at least 1 :5, even more preferably 1 :7, yet more preferably from 1 :7 to 1 :250.

In one embodiment such high aspect ratio fillers have a mean particle size in the range of from 0.001 to 100 microns, preferably of from 0.005 to 50 microns and more preferably of from 0.01 to

10 microns.

In another embodiment such high aspect ratio fillers have a BET surface area, measured in accordance with DIN (Deutsche Industrie Norm) 66131, of from 5 to 200 square meters per gram.

In a preferred embodiment the high aspect ratio fillers are selected from the group consisting of nanoclays, preferably an organically modified nanoclay. This embodimentis not limited to a specific nanoclay; however, natural powdered smectite clays, such as sodium or calcium montmorillonite, or synthetic clays such as hydrotalcite and laponite are preferred as starting materials. Organically modified montmorillonite nanoclays are especially preferred.

The clays are preferably modified by substitution of the transition metal for an onium ion, as is known in the art, to provide surfactant functionality to the clay that aids in the dispersion of the clay within the generally hydrophobic polymer environment. Preferred onium ions are phosphorus based (eg: phosphonium ions) and nitrogen based (eg: ammonium ions) and contain functional groups having from 2 to 20 carbon atoms (eg: NR ₄ ^{+ "} MMT).

The clays are preferably provided in nanometer scale particle sizes, preferably less than 25μηι by volume, more preferably from 1 to 50 μηι, still more preferably from 1 to 30 μηι, yet more preferably from 2 to 20 μηι.

In addition to silica, the preferred nanoclays may also contain some fraction of alumina. The nanoclays may contain from 0.1 to 10 wt.-% alumina, preferably 0.5 to 5 wt.-%, more preferably 1 to 3 wt.-% alumina. Examples of preferred commercially available organically modified nanoclays suitable for use as high aspect ratio fillers according to the present invention are sold under the tradenames Cloisite® clays 10A, 20A, 6A, 15A, 30B, or 25A and Nanomer® 1.44P, 1.44PS, and 1.34TCN. Other examples of high aspect ratio fillers include Polyfil 80™, Mistron Vapor™, Mistron HAR™, Mistron CB™ as well as hydrotalcite clays such as Perkalite LD, or Perkalite F100. The filled cured polymers according to the invention may include other components, such as one or more auxiliary components common in the rubber compounding arts. In one embodiment, the process of the present invention further comprises the step of adding one or more auxiliary components to the azidated copolymer prior to step c). Suitable auxiliary components include, but are not limited to, antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ozone stabilizers, processing aids, plasticizers, tackifiers, dyestuffs, pigments, waxes, extenders, organic acids, inhibitors, metal oxides, and activators such as triethanolamine, polyethylene glycol, hexanetriol, etc. Such auxiliary components for rubbers are known to persons skilled in the art. The auxiliary components are used in conventional amounts, which depend on the intended use. Conventional amounts are, for example, for about 0.1 to about 50 phr. However, it is typical that these auxiliary components are provided in a minor amount relative to the azidated copolymer.

Secondary Rubber Component

A secondary rubber component may optionally be added prior to step c) included in filled cured compounds comprising the azidated copolymers. These rubbers include, but are not limited to, natural rubbers, polyisoprene rubber, poly (styrene-co-butadiene) rubber (SBR), polybutadiene rubber (BR), poly (isoprene-co-butadiene) rubber (IBR), styrene-isoprene- butadiene rubber (SIBR), ethylene-propylene rubber (EPM), ethylene-propylenediene rubber (EPDM), polysulfide, nitrile rubber, propylene oxide polymers, starbranched butyl rubber and halogenated star -branched butyl rubber, brominated butyl rubber, chlorinated butyl rubber, star-branched polyisobutylene rubber, starbranched brominated butyl (polyisobutylene/isoprene copolymer) rubber ; poly (isobutylene-co p-methylstyrene) and halogenated poly (isobutylene-co-p- methylstyrene), such as, for example, terpolymers of isobutylene derived units, methylstyrene derived units, and p- bromomethylstyrene derived units, and mixtures thereof.

A desirable embodiment of the secondary rubber component present is natural rubber. Natural rubbers are described in detail by Subramaniam in RUBBER TECHNOLOGY 179-208 (Maurice Morton, Chapman & Hall 1995). Desirable embodiments of the natural rubbers of the present invention are selected from 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 100 C (ML

1+4) of from 30 to 120, more preferably from 40 to 65. The Mooney viscosity test referred to herein is in accordance with ASTM D-1646.

Polybutadiene (BR) rubber is another desirable secondary rubber useful in the composition of the invention. The Mooney viscosity of the polybutadiene rubber as measured at 100 C (ML 1+4) may range from 35 to 70, from 40 to about 65 in another embodiment, and from 45 to 60 in yet another embodiment. Some commercial examples of these synthetic rubbers useful in the present invention are NATSYNTM (Goodyear Chemical Company), and BUDENE 1207 or BR 1207 (Goodyear Chemical Company). A desirable rubber is high cis-polybutadiene (cis-BR). By"cis- polybutadiene"or"high cis-polybutadiene", it is meant that 1, 4cis polybutadiene is used, wherein the amount of cis component is at least 95%.

An example of high cis-polybutadiene commercial products useful as a secondary rubber herein is BUDENE™ 1207.

Rubbers of ethylene and propylene derived units such as EPM and EPDM are also suitable as secondary rubbers. Examples of suitable comonomers in making EPDM are ethyliden norbornene, 1, 4-hexadiene, dicyclopentadiene, as well as others. These rubbers are described in RUBBER TECHNOLOGY 260-283 (1995). A suitable ethylene-propylene rubber is commercially available as VISTALON (ExxonMobil Chemical Company, Houston TX). In another embodiment, the secondary rubber is a halogenated rubber as part of the terpolymer composition. The halogenated butyl rubber is brominated butyl rubber, and in another embodiment is chlorinated butyl rubber. General properties and processing of halogenated butyl rubbers is described in THE VANDERBILT RUBBER HANDBOOK 105-122 (Robert F. Ohm ed., R. T. Vanderbilt Co., Inc. 1990), and in RUBBER TECHNOLOGY 311 -321 (1995). Butyl rubbers, halogenated butyl rubbers, and star-branched butyl rubbers are described by Edward Kresge and H.C. Wang in 8 KIRK-OTHMER ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY 934-955 (John Wiley & Sons, Inc. 4th ed. 1993).

The secondary rubber component includes, but is not limited to at least one or more of brominated butyl rubber, chlorinated butyl rubber, star-branched polyisobutylene rubber, star-branched brominated butyl (polyisobutylene/isoprene copolymer) rubber ; halogenated poly (isobutylene-co- p- methylstyrene), such as, for example, terpolymers of isobutylene derived units, p- methylstyrene derived units, and p-bromomethylstyrene derived units (BrIBMS), and the like halomethylated aromatic interpolymers as in US 5,162,445; US 4,074,035; and US 4,395,506; halogenated isoprenes and halogenated isobutylene copolymers, polychloroprene, and the like, and mixtures of any of the above. Some embodiments of useful halogenated rubber secondary components are also described in US 4,703,091 and US 4,632,963. All of the above documents are incorporated herein by reference. In one embodiment of the invention, a so called semi-crystalline copolymer ("SCC") is present as the secondary"rubber"component. Semicrystalline copolymers are described in WO00/69966. Generally, the SCC is a copolymer of ethylene or propylene derived units and a-olefm derived units, the a-olefin having from 4 to 16 carbon atoms in one embodiment, and in another embodiment the SCC is a copolymer of ethylene derived units and a-olefm derived units, the a- olefin having from 4 to 10 carbon atoms, wherein the SCC has some degree of crystallinity. In a further embodiment, the SCC is a copolymer of 1 -butene derived units and another a-olefin derived unit, the other a-olefm having from 5 to 16 carbon atoms, wherein the SCC also has some degree of crystallinity. The SCC can also be a copolymer of ethylene and styrene. WO00/69966 is incorporated herein by reference.

The secondary rubber component may be present in a range from 1 phr up to 90 phr in one embodiment, from 1 phr up to 50 phr in another embodiment, from 1 phr up to 40 phr in another embodiment, and from 1 phr up to 30 phr in yet another embodiment. In the foregoing ranges, the secondary rubber may be present in a minimum quantity of from at least 2 phr in one embodiment, from at least 5 phr in another embodiment, from at least 5 phr in yet another embodiment, and from at least 10 phr in still another embodiment. A desirable embodiment may include any combination of any upper phr limit and any lower phr limit. For example, the secondary rubber, either individually or as a blend of rubbers such as, for example NR and BR, may be present from 5 phr to 90 phr in one embodiment, and from 10 to 80 phr in another embodiment, and from 30 to 70 phr in yet another embodiment, and from 40 to 60 phr in yet another embodiment, and from 5 to 50 phr in yet another embodiment, and from 5 to 40 phr in yet another embodiment, and from 20 to 60 phr in yet another embodiment, and from 20 to 50 phr in yet another embodiment, the chosen embodiment depending upon the desired end use application.

Mixing The compound (also referred to as uncured composition) may be prepared in step b) by using conventional mixing techniques including, e.g., kneading, roller milling, extruder mixing, internal mixing (such as with a BanburyM) 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 copolymer rubber, carbon black and plasticizer are added and the composition mixed for the desired time or to a particular temperature to achieve adequate dispersion of the ingredients. Alternatively, the rubber and a portion of the carbon black or filler (e.g., one-third to two thirds) is mixed for a short time (e.g., about 1 to 3 minutes) followed by the remainder of the carbon black or filler and optionally oil. Mixing is continued for about 5 to 10 minutes at high rotor speed during which time the mixed components reach a temperature of about 140 °C. Following cooling, the components are mixed in a second step on a rubber mill or in a Banbury mixer during which the components are uniformly dispersed at relatively low temperature, e.g., about 80 to about 105 °C, to avoid premature curing of the composition. Variations in mixing will be readily apparent to those skilled in the art and the present invention is not limited to any specific mixing procedure. The mixing is performed to preferably disperse all components of the composition thoroughly and uniformly.

Foaming

Upon curing the azidated copolymers at elevated temperatures, azide groups of the azidated copolymer are decomposed and nitrogen gas is evolved.

By curing in a closed mold and by selecting fillers that reduce the permeability of the elastomer composition to nitrogen gas during curing, for example high aspect ratio fillers such as high aspect ratio carbon black, high aspect ratio clays, high aspect ratio silica and other fillers that reduce nitrogen permeability, the evolved nitrogen gas is trapped within the copolymer matrix to form micropores. The cured copolymer comprising micropores may be referred to as a foamed elastomer; however, it should be noted that the foamed elastomers described herein are formed in the absence of added blowing agents, foaming agents, or externally introduced gases. This leads to a clean cured elastomer with reduced density and/or durometer as compared with conventional non-foamed butyl rubber elastomers.

The micropores may comprise an elevated level of nitrogen gas, for example greater than or equal to 75%, or in another embodiment greater than or equal to 80% nitrogen gas, greater than or equal to 85% nitrogen gas, greater than or equal to 90% nitrogen gas or greater than or equal to 95% nitrogen gas. The nitrogen gas content of the micropores decreases slowly following curing. The micropores vary in size from 2 μηι to 100 μηι. Without wishing to be limited by theory, it is believed that this is dependent on the permeability of the cured copolymer to nitrogen gas. The presence of the micropores reduces the density of the foamed elastomer as compared with conventional non-foamed butyl rubber elastomers. Additionally or alternatively, the presence of micropores reduces the durometer of the foamed elastomer as compared with conventional non- foamed butyl rubber elastomers.

The density of the foamed elastomers may be less than 1 g/cm ³ . The calculated density (compound density) of the foamed elastomers may be greater than the actual density of the foamed elastomers. The ratio between the actual (experimentally determined) density of the copolymer and the calculated density of the copolymer may be less than 1, for example in the range of from 0.20 to

0.99, 0.30 to 0.95, 0.40 to 0.90 or a range comprising a combination of values selected from the following values: 0.99, 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, 0.55, 0.50, 0.45, 0.40, 0.35, 0.30, 0.25, 0.20. Compound densities or the density of filled copolymers may be calculated by methods known to persons of skill in the art and density of polymers may be determined experimentally by a variety of methods, for example pycnometry. The filled cured polymers according to the present invention are useful in foamed and non-foamed shaped articles including but not limited to tire inner liners, foamed and non-foamed pharmaceutical closures, foamed and non-foamed pharmastoppers, foamed and non-foamed components of medical devices including syringe plungers, foamed and non-foamed noise vibration and harshness damping materials, foamed and non-foamed lightweight gas barrier materials, personal flotation devices, buoys, mats, such as sports mats, yoga mats and sleeping pads, padding for grips, handles, handle bars, sports rackets, consumer goods, shopping cart handles, steering bars, steering wheels, weather stripping, condenser caps, golf balls, foamed and non-foamed shoe soles, seals and gaskets including but not limited to in-place gaskets, thermal insulation, bullet-proof vests, seat pillows, orthopedic devices, extruded profiles, components for tanks containing pressurized gases and pressurized liquids, energy absorbing foams, elastic foam for safety pneumatic tire and runflat tires.

The invention will now be described with reference to specific examples. It will be understood that the following examples are intended to describe embodiments of the invention and are not intended to limit the invention in any way.

Examples

Materials

Bromobutyl 2030 was received from LANXESS. Tetrahydrofuran and tetrabutyl ammonium azide was purchased from Aldrich. Sunpar 2280 is a paraffinic oil and was supplied by Sunoco. Pentalyn A is the pentaerythritol ester of refined wood rosin and was supplied by Eastman. Polyfil DLX was supplied by KaMin, Mistron Vapor and Mistron HAR was supplied by Imerys Talc, HiSil532EP was supplied by PPG industries, Sterling® V carbon black was supplied by Cabot. Table 1 is an overview of the fillers that were employed in the examples. Bromobutyl 2030 is a brominated isobutylene-isoprene rubber having a bromine content of 1,8 ± 0,2 wt-% and a Mooney viscosity of 32 ± 4 MU.

Table 1.

Spec, Particle Skeletal

surface size density Aspect

Filler pH

(mV) ( πι) g mL-1 ratio

Polyfil DLX 7 12 6.7 2.6 >3: 1

Mistron Vapor 9.5 13 3.7 2.7 - 2.8 >3: 1

Mistron HAR 9 21 1.1 2.7 - 2.9 >3: 1

HiSil 532EP 8 60 15 2.1 Y<3: 1

STERLING® V

8.5 36 1.8 <3: 1 carbon black

Polyfil DLX is a delaminated kaolin clay. Mistron Vapor and Mistron HAR are clays. HiSil 532EP is a synthetic precipitated amorphous silica, STERLING® V carbon black is a medium reinforcing carbon black, ASTM grade N660.

Example 1. Bromobutyl 2030 (111 g) was dissolved in tetrahydrofuran (669 g) and tetrabutylammonium azide (6.3 g) was added to the solution. The mixture was then shaken at room temperature for 2 days. Then acetone was added and the precipitated elastomer was separated from the solvent and dried. The conversion of allylic bromide to allylic azide units was quantitative according to ¾ NMR. This azidated butyl rubber, or azidobutyl rubber, was used as the basis for further compounding experiments.

Examples 2-7 Elastomer compounding

Examples 2 - 7 were mixed in a 85 mL Brabender miniature internal mixer equipped with Banbury rotors at 60°C and 60 rpm. The mixing procedure was as follows: add approximately half of the azidated butyl rubber, followed by all of the filler, and then the remainder of the rubber. The compound was allowed to mix until a steady torque was obtained, at which point it was dumped from the mixing chamber. The compounds were then refined on a room temperature 4 x 6 two-roll mill. Each compound was subjected to a minimum of 6 ¾ cuts and 6 endwise passes. Small samples of each compound were analyzed according to ASTM D 5289 using an MDR with a 1° arc at 190°C for 60 minutes and 200°C for 60 or 30 minutes.

Elastomer characterization

Stress-strain on test specimen cured at 190 °C were performed according to ASTM D 412. Permeability to oxygen was characterized according to ASTM D 3985. The density of vulcanized compounds was measured according to ASTM D 297 except that the test temperature s 22°C +/- 1°C instead of 25°C +/- 0.5°C

Table 2 describes the composition and test results of azidobutyl compounds and vulcanizates.

Examples 2 and 3 comprised compounding two high aspect ratio fillers, Mistron HAR and Polyfil DLX, into azidobutyl and subjecting the resulting compound to curing.

Example 4 comprised compounding silica HiSil532, into azidobutyl and subjecting the resulting compound to MDR measurements. Upon opening of the MDR mold the vulcanizate disintegrated, therefore no further characterizations were performed with material prepared according to Example 4. Example 5 comprised compounding HiSil532EP and Mistron Vapor (one spherical and one high- aspect ratio filler) into azidobutyl.

Examples 6 and 7 comprised compounding Carbon Black N660 into azidobutyl. Example 7 furthermore contains the plasticizer and process aids mentioned in Table 1. Table 2.

Example 1 2 3 4 5 6 7

Example 1, phr

100 100 100 100 100 100 100

High aspect ratio

Mistron Polyfil Mistron

filler, type none

HAR DLX Vapor

High aspect ratio

60 60 45

filler, phr

Carbon Carbon

HiSil HiSil

Spherical filler type Black Black

532EP 532EP

N660 N660

Spherical filler, phr 60 15 60 60

Stearic acid, phr 1

Pentalyn A, phr 4

Sunpar 2280, phr 7

MDR, 190 °C, 1.7 Hz, 1° Arc, 60 min

M _H (dN-m) 5.7 8.2 7.4 4.2 3.8 19.9 9.7

M _L (dN-m) 1.2 1.6 1.6 4.2 1.5 3.3 2.2

M _H - M _L (dN-m) 4.4 6.7 5.8 0.0 2.3 16.7 7.5 t ₉₀ (min) 20.2 27.1 21.1 60.0 47.4 15.1 13.3

MDR, 200 °C, 1.7 Hz, l° Arc

Test Duration (min) 60 30 30 30 60 60 15

M _H (dN-m) 5.2 7.2 6.8 3.5 3.1 19.1 8.9

M _L (dN-m) 1.1 1.3 1.5 3.5 1.4 3.0 2.0

M _H - M _L (dN-m) 4.1 5.9 5.4 0.0 1.7 16.1 6.9 t ₉₀ (min) 9.3 5.3 4.3 30.0 23.7 8.0 6.9

Physical properties, cured at 190 °C for t ₉₀ + 5 min

Cure Time (min) 35 33 27 n.d. 53 21 18

Hardness Shore A2

27 28 23 n.d. 13 61 n.d. (pts.)

Ultimate Tensile

0.22 3.25 2.24 n.d. 1.09 12.68 4.56 (MPa)

Ultimate Elongation

205 491 445 n.d. 381 244 223 (%)

Stress @ 100 (MPa) 0.42 1.11 0.65 n.d. 0.15 3.61 2.11

Stress @ 200 (MPa) 0.55 1.58 1.01 n.d. 0.24 10.03 4.37

Stress @ 300 (MPa) - 1.97 1.36 n.d. 0.41 - -

MDR data in Table 2 shows that crosslinking of the unfilled and filled azidobutyl compounds took place when heated to 190 and 200 °C. Stress-strain data in Table 2 shows that a vulcanizate with meaningful physical properties results via the crosslinking.

Surprisingly, the vulcanizate appearance and density could be tuned by the type of filler or filler combination that was mixed into the azidobutyl compound. Vulcanizates according to Example 1 contained only a few gas bubbles visible to the eye. Vulcanizates containing high-aspect ratio fillers (Examples 2 and 3) led to resilient, closed-cell foams with specific gravities in the range of d _exp , = 0.7 - 0.8 g mL ^"1 (vs. a calculated value for the non- vulcanized compound of d _ca\c. = 1.23 g mL ^"1 , thus a value for r as defined in Table 2 of 60 - 62%).

Surprisingly, the combination of silica with a high-aspect ratio fillers led to a foam with reduced density (d) vs. non-silica containing examples (Example 5 vs. Example 2 and 3), dexp. ⁼ 0.42, r = 34%; surprisingly compounding and curing according to Example 4 led to a vulcanizate that disintegrated into a crumbly material upon pressure release, which was not characterized further. Incorporation of non-high aspect ratio carbon black leads to solid vulcanizates that do not contain any macroscopic or microscopic gas bubbles with a density around 1 g ml ^"1 .

Without wishing to be bound by theory, it is speculated that silica acts as an adsorbent for the nitrogen that is released during the crosslinking process. Upon mold opening, the pressure decrease leads to nitrogen release and thereby to disintegration of the vulcanizate to a crumbly matter (as in Example 4), or a low density foam (see Example 5).

Surprisingly, the azidobutyl-based foamed vulcanizates containing high aspect ratio fillers (Examples 2 and 3) according to the present invention show a decreased permeability to gases compared to the azidobutyl-based non-foamed vulcanizates (Examples 6 and 7). This makes the azidobutyl based foams particularly useful in gas barrier applications like tire inner liners and pharmaceutical closures.