CA2557217A1 - Curing bladders containing a peroxide curable rubber compound - Google Patents

Abstract

The present invention relates to a curring bladder containing a peroxide curable rubber compound prepared with a peroxide curing system, and a polymer having a Mooney viscosity of at least 25 Mooney-units and a gel content of less than 15 wt.%
containing repeating units derived from at least one isoolefin monomer, more than 4.1 mol% of repeating units derived from at least one multiolefin monomer, as well as optionally further copolymerizable monomers, and repeating units derived from at least one multiolefin cross-linking agent containing no transition metal compounds and no organic nitro compounds.

Description

CURING BLADDERS CONTAINING A PEROXIDE CURABLE RUBBER
COMPOUND
FIELD OF THE INVENTION
The present invention relates to a curring bladder containing a peroxide curable rubber compound prepared with a peroxide curing system, and a polymer having a Mooney viscosity of at least 25 Mooney-units and a gel content of less than 15 wt.%
containing repeating units derived from at least one isoolefin monomer, more than 4.1 mol% of repeating units derived from at least one multiolefin monomer, as well as optionally further copolymerizable monomers, and repeating units derived from at least one multiolefin cross-linking agent containing no transition metal compounds and no organic nitro compounds.
BACKGROUND OF THE INVENTION
Butyl rubber is understood to be a copolymer of an isoolefin and one or more, preferably conjugated, multiolefins as comonomers. Commercial butyl comprise a major portion of isoolefin and a minor amount, not more than 2.5 mol %, of a conjugated multiolefin. The preferred isoolefin is isobutylene. However, this invention also covers polymers optionally comprising additional copolymerizable co-monomers.
Butyl rubber or butyl polymer is generally prepared in a slurry process using methyl chloride as a vehicle and a Friedel-Crafts catalyst as part of the polymerization initiator. The methyl chloride offers the advantage that AIC13, a relatively inexpensive Friedel-Crafts catalyst, is soluble in it, as are the isobutylene and isoprene comonomers. Additionally, the butyl rubber polymer is insoluble in the methyl chloride and precipitates out of solution as fine particles. The polymerization is generally carried out at temperatures of about -90°C to -100°C. See U.S. Patent No. 2,356,128 and Ullmanns Encyclopedia of Industrial Chemistry, volume A 23, 1993, pages 288-295.
The low polymerization temperatures are required in order to achieve molecular weights which are sufficiently high for rubber applications.

' CA 02557217 2006-08-24 Peroxide curable butyl rubber compounds offer several advantages over conventional, sulfur-curing, systems. Typically, these compounds display extremely fast cure rates and the resulting cured articles tend to possess excellent heat resistance. In addition, peroxide-curable formulations are considered to be "clean" in that they do not contain any extractable inorganic impurities (e.g. sulfur). The clean rubber articles can therefore be used, for example, in condenser caps, biomedical devices, pharmaceutical devices (stoppers in medicine-containing vials, plungers in syringes) and possibly in seals for fuel cells.
It is well accepted that polyisobutylene and butyl rubber decompose under the action of organic peroxides. Furthermore, US 3,862,265 and US 4,749,505 teach us that copolymers of a C4 to C~ isomonoolefin with up to 10 wt. % isoprene or up to 20 wt.
para-alkylstyrene undergo a molecular weight decrease when subjected to high shear mixing. This effect is enhanced in the presence of free radical initiators.
One approach to obtaining a peroxide-curable butyl-based formulation lies in the use of conventional butyl rubber in conjunction with a vinyl aromatic compound like DVB
and an organic peroxide (see JP-A-107738/1994). In place of DVB, an electron-withdrawing group-containing polyfunctional monomer (ethylene dimethacrylate, trimethylolpropane triacrylate, N,N'-m-phenylene dimaleimide) can also be used (see JP-A-172547/1994).
A commercially available terpolymer based on IB, IP, and DVB, Bayer XL-10000, is curable with peroxides alone. However, this material does possess some significant disadvantages. For example, the presence of significant levels of free DVB can present serious safety concerns. In addition, since the DVB is incorporated during the polymerization process a significant amount of crosslinking occurs during manufacturing. The resulting high Mooney (ca. 60-75 MU, M~1+8@125 °C) and presence of gel particles make this material extremely difficult to process.
For these reasons, it would be desirable to have an isobutylene based polymer which is peroxide curable, completely soluble (i.e. gel free) and contains no, or trace amounts of, divinylbenzene in its composition.

U.S. Patent No. 5,578.682 claims a process for obtaining a polymer with a bimodal molecular weight distribution derived from a polymer that originally possessed a monomodal molecular weight distribution. The polymer, e.g., polyisobutylene, a butyl rubber or a copolymer of isobutylene and para-methylstyrene, was mixed with a polyunsaturated crosslinking agent (and, optionally, a free radical initiator) and subjected to high shearing mixing conditions in the presence of organic peroxide. This bimodalization was a consequence of the coupling of some of the free-radical degraded polymer chains at the unsaturation present in the crosslinking co-agent. It is important to note that this patent was silent about any filled compounds of such modified polymers or the cure state of such compounds.
U.S. Patent No. 5,994,465 discloses a method for curing regular butyl, with isoprene contents ranging from 0.5 to 2.5 mol %, by treatment with a peroxide and a bismaleimide species.
Co-Pending application CA 2,418,884 discloses a continuous process for producing polymers having a Mooney viscosity of at least 25 Mooney-units and a gel content of less than 15 wt. % comprising repeating units derived from at least one isoolefin monomer, more than 4.1 mol % of repeating units derived from at least one multiolefin monomer and optionally further copolymerizable monomers in the presence of AIC13 and a proton source and/or cationogen capable of initiating the polymerization process and at least one multiolefin cross-linking agent wherein the process is conducted in the absence of transition metal compounds. These polymers are well suited for the inventive rubber formulations of this invention and with regards to jurisdictions allowing for this method are enclosed by reference herein.
Co-Pending application CA 2,458,741 discloses a peroxide curable rubber compound containing polymers with a Mooney viscosity of at least 25 Mooney-units and a gel content of less than 15 wt.% comprising repeating units derived from at least one isoolefin monomer, more than 4.1 mol% of repeating units derived from at least one multiolefin monomer, as well as optionally further copolymerizable monomers, and repeating units derived from at least one multiolefin cross-linking agent containing no transition metal compounds and no organic nitro compounds.

Conventional resin curing systems are difficult to use in making a curing bladder.
The result is a curing bladder with inferior physical properties due to incomplete cure.
An ultimate elongation of less than 700% is desirable, with lower ultimate elongation values being indicative of more complete curing. It would further be desirable to achieve more complete curing using an alternate curing system that does not impart extractable impurities to the curing bladder.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a curing bladder comprising a peroxide curable rubber compound preferably prepared with polymers having a Mooney viscosity of at least 25 Mooney-units and a gel content of less than 15 wt.%
containing repeating units derived from at least one isoolefin monomer, more than 4.1 mol% of repeating units derived from at least one multiolefin monomer, as well as optionally further copolymerizable monomers, and repeating units derived from at least one multiolefin cross-linking agent containing no transition metal compounds and no organic nitro compounds.
In another aspect, the present invention provides a curing bladder made by:
providing a peroxide curable rubber compound comprising repeating units derived from at least one isoolefin monomer, at least 4.1 mol% of repeating units derived from at least one multiolefin monomer, and repeating units derived from at least one multiolefin cross-linking agent; adding a peroxide curing system to the compound comprising at least a thermally activated peroxide and a peroxide curing co-agent; forming the curing bladder from the peroxide curable rubber compound with the added peroxide curing system; and, peroxide curing the curing bladder.
The curing bladder preferably has a greater degree of cure than that obtained using resin based curing systems. Preferably, the curing bladder exhibits an ultimate elongation of less than 700%.
Further features of the invention will now be described in greater detail with reference to preferred embodiments of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The Mooney viscosity of a polymer suitable for use in rubber compounds for curing bladders can be determined using ASTM test D1646 using a large rotor at °C, a preheat phase of 1 min, and an analysis phase of 8 min (ML1+8 @
125 °C).
The polymer used in preparing the peroxide curable rubber compound preferabl has a multiolefin content of greater than 4.1 mol%, and a gel content of less than 10 wt.% and have been produced at conversions ranging from 70 % to 95%.
Preferably, suitble polymers for use in curing bladder rubber compounds have a Mooney viscosity in the range of from 25-70 MU, more preferably 30-60 MU, even more preferably MU.
The isoolefin of the polymer suitable in the present invention is not limited to a special isoolefin. However, isoolefins within the range of from 4 to 16 carbon atoms, preferably 4-7 carbon atoms, such as isobutene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 4-methyl-1-pentene and mixtures thereof are preferred. Most preferred is isobutene.
Likewise the multiolefin of the polymer suitable in the present invention is not limited to a special multiolefin. Every multiolefin copolymerizable with the isoolefin known by the skilled in the art can be used. However, multiolefins within the range of from 4-14 carbon atoms, such as isoprene, butadiene, 2-methylbutadiene, 2,4-dimethylbutadiene, piperyline, 3-methyl-1,3-pentadiene, 2,4-hexadiene, 2-neopentylbutadiene, 2-methyl-1,5-hexadiene, 2,5-dimethyl-2,4-hexadiene, 2-methyl-1,4-pentadiene, 2-methyl-1,6-heptadiene, cyclopentadiene, methylcyclopentadiene, cyclohexadiene, 1-vinyl-cyclohexadiene and mixtures thereof, in particular conjugated dienes, are preferred. Isoprene is most preferred.
In the present invention, ~3-pinene can also be used as a co-monomer for the isoolefin.
As optional monomers every monomer copolymerizable with the isoolefins and/or dienes known by the skilled in the art can be used. a-methyl styrene, p-methyl styrene, chlorostyrene, cyclopentadiene and methylcyclopentadiene are preferred. Indene and other styrene derivatives may also be used in the present invention.
The multiolefin content of suitable polymers for using the curing bladder rubber compounds is at least greater than 4.1 mol%, more preferably greater than 5.0 mol%, even more preferably greater than 6.0 mol%, yet even more preferably greater than 7.0 mol%.
Preferably, the monomer mixture for the polymer suitable in the present invention contains in the range of from 80% to 95% by weight of at least one isoolefin monomer and in the range of from 4.0% to 20% by weight of at least one multiolefin monomer and in the range of from 0.01 % to 1 % by weight of at least one multiolefin cross-linking agent. More preferably, the monomer mixture contians in the range of from 83%
to 94%
by weight of at least one isoolefin monomer and in the range of from 5.0% to 17% by weight of a multiolefin monomer and in the range of from 0.01 % to 1 % by weight of at least one multiolefin cross-linking agent. Most preferably, the monomer mixture contains in the range of from 85% to 93% by weight of at least one isoolefin monomer and in the range of from 6.0% to 15% by weight of at least one multiolefin monomer and in the range of from 0.01 % to 1 % by weight of at least one multiolefin cross-linking agent.
The weight average molecular weight, MW, is preferably greater than 240 kg/mol, more preferably greater than 300 kg/mol, even more preferably greater than 500 kg/mol, yet even more preferably greater than 600 kg/mol.
In connection with the present invention the term "gel" is understood to denote a fraction of the polymer insoluble for 60 min in cyclohexane boiling under reflux. The gel content is preferably less than 10 wt.%, more preferably less than 5 wt%, even more preferably less than 3 wt%, yet even more preferably less than 1 wt%.
There are no organic nitro compounds or transition metals present in the butyl polymer for the rubber compounds for curing bladders of the present invention.

The butyl polymer may further contain units derived from one or more multiolefin cross-linking agents. The term cross-linking agent is known to those skilled in the art and is understood to denote a compound that causes chemical cross-linking between the polymer chains in opposition to a monomer that will add to the chain. Some easy preliminary tests will reveal if a compound will act as a monomer or a cross-linking agent. The choice of the cross-linking agent is not particularly restricted.
Preferably, the cross-linking agent contains a multiolefinic hydrocarbon compound.
Examples include norbornadiene, 2-isopropenylnorbornene, 2-vinyl-norbornene, 1,3,5-hexatriene, 2-phenyl-1,3-butadiene, divinylbenzene, diisopropenylbenzene, divinyltoluene, divinylxylene and C~ to C2o alkyl-substituted derivatives thereof. More preferably, the multiolefin crosslinking agent is divinylbenzene, diisopropenylbenzene, divinyltoluene, divinyl-xylene and C~ to C2o alkyl substituted derivatives thereof, and or mixtures of the compounds given. Most preferably the multiolefin crosslinking agent contains divinylbenzene and diisopropenylbenzene.
The polymerization preferably is performed in a continuous process in slurry (suspension), in a suitable diluent, such as chloroalkanes as described in U.S. Patent No. 5,417,930.
The monomers are generally polymerized cationically, preferably at temperatures in the range from -120°C to +20°C, preferably in the range from -100°C to -20°C, and pressures in the range from 0.1 to 4 bar.
The use of a continuous reactor as opposed to a batch reactor seems to have a positive effect on the polymer. Preferably, the process is conducted in at least one continuos reactor having a volume of between 0.1 m3 and 100 m3, more preferable between 1 m3 and 10 m3.
Inert solvents or diluents known to the person skilled in the art for butyl polymerization may be considered as the solvents or diluents (reaction medium). These comprise alkanes, chloroalkanes, cycloalkanes or aromatics, which are frequently also mono- or polysubstituted with halogens. Hexane/chloroalkane mixtures, methyl chloride, dichloromethane or the mixtures thereof may be mentioned in particular.
Chloroalkanes are preferably used in the process according to the present invention.

Said polymers with a Mooney viscosity of at least 25 Mooney-units and a gel content of less than 15 wt.% containing repeating units derived from at least one isoolefin monomer, more than 4.1 mol% of repeating units derived from at least one multiolefin monomer, as well as optionally further copolymerizable monomers, and repeating units derived from at least one multiolefin cross-linking agent containing no transition metal compounds and no organic nitro compounds may be partially or fully chlorinated or brominated.
Bromination or chlorination can be performed according to the procedures known to those skilled in the art, such as as described in Rubber Technology, 3~d Ed., Edited by Maurice Morton, Kluwer Academic Publishers, pp. 297 - 300 and references cited within this reference.
The rubber compounds for cutting bladders according to the present invention may contain other rubbers, such as NR, BR, HNBR, NBR, SBR, EPDM or fluororubbers.
The preparation of rubber compounds is known to those skilled in the art. In most cases carbon black is added as filler and a peroxide based curing system is used.
Suitable compounding and vulcanization processes are known to those skilled in the art, such as the process disclosed in Encyclopedia of Polymer Science and Engineering, Vol. 4, S. 66 et seq. (Compounding) and Vol. 17, S. 666 et seq.
(Vulcanization).
The present invention is not limited to a special peroxide curing system. For example, inorganic or organic peroxides are suitable. Preferably, the peroxides are thermally activated. Preferred are organic peroxides such as dialkylperoxides, ketalperoxides, aralkylperoxides, peroxide ethers, peroxide esters, such as di-tert.-butylperoxide, bis-(tert.-butylperoxyisopropyl)-benzol, dicumylperoxide, 2,5-dimethyl-2,5-di(tert.-butylperoxy)-hexane, 2,5-dimethyl-2,5-di(tert.-butylperoxy)-hexene-(3), 1,1-bis-(tert.-butylperoxy)-3,3,5-trimethyl-cyclohexane, benzoylperoxide, tert.-butylcumyl-peroxide and tert.-butylperbenzoate. Usually the amount of peroxide in the compound is in the range of from 1 to 10 phr (= per hundred rubber), preferably from 1 to 5 phr.
Subsequent curing is usually performed at a temperature in the range of from 100 to 200°C, preferably 130 to 180°C. Peroxides might be applied advantageously in a polymer-bound form. Suitable systems are commercially available, such as Poly-dispersion T(VC) D-40 P from Rhein Chemie Rheinau GmbH, D (= polymerbound di-tert.-butylperoxy-isopropylbenzene).
The peroxide curing system may further comprise one or more peroxide curing co-agents. The co-agent may include bis dieneophiles. Suitable bis dieneophiles include m-phenyl-bis-maleinimide and m-phenylene-bis-maleimide. The co-agent may include triallyl isocyanurate (TAIC), commercially available under the trademark DIAK~
7 from DuPont, or N,N'-m-phenylene dimaleimide, known as HVA-2 (DuPont Dow), triallyl cyanurate (TAC) or liquid polybutadiene known as Ricon~ D 153 (supplied by Ricon Resins). Other suitable compounds that are known to cure halobutyl elastomers include phenolic resins, amines, amino acids, peroxides, zinc oxide and the like.
Combinations of the aforementioned curatives may also be used. The rubber compounds may further contain a co-agent such as zinc diacrylate. Amounts can be equivalent to the peroxide curative or less. Particulary suitable co-agents include the commercially available co-agents HVA-2, SR-633, or combinations thereof.
An antioxidant may also be included in the compound, suitably in an amount up to 4 phr, preferably about 2 phr. Examples of suitable antioxidants include p-dicumyl diphenylamine (Naugard~ 445), Vulkanox~ DDA (a diphenylamine derivative), Vulkanox~ ZMB2 (zinc salt of methylmercapto benzimidazole), Vulkanox~ HS
(polymerized 1,2-dihydro-2,2,4-trimethyl quinoline) and Irganox~ 1035 (thiodiethylene bis(3,5-di-tert.-butyl-4-hydroxy) hydrocinnamate or thiodiethylene bis(3-(3,5-di-tert.-butyl-4-hydroxyphenyl)propionate supplied by Ciba-Geigy. Vulkanox is a trademark of Lanxess Inc.
The rubber compound according to the present invention can contain further auxiliary products for rubbers, such as reaction accelerators, vulcanizing agents, vulcanizing accelerators, vulcanizing acceleration auxiliaries, antioxidants, foaming agents, anti-aging agents, heat stabilizers, light stabilizers, ozone stabilizers, processing aids, resins, plasticizers, tackifiers, blowing agents, dyestuffs, pigments, waxes, extenders, organic acids, inhibitors, metal oxides, and activators such as triethanolamine, polyethylene glycol, hexanetriol, etc., which are known to the rubber industry. The rubber aids are used in conventional amounts, which depend inter alia on the intended use. Conventional amounts are e.g. from 0.1 to 50 wt.%, based on rubber.
Preferably the compound furthermore contains in the range of 0.1 to 20 phr of an organic fatty acid, preferably a unsaturated fatty acid having one, two or more carbon double bonds in the molecule which more preferably includes 10% by weight or more of a conjugated diene acid having at least one conjugated carbon-carbon double bond in its molecule. Preferably those fatty acids have in the range of from 8- 22 carbon atoms, more preferably 12-18. Examples include stearic acid, palmic acid and oleic acid and their calcium-, zinc-, magnesium-, potassium- and ammonium salts.
The ingredients of the final compound can be mixed together, suitably at an elevated temperature that may range from 25 °C to 200 °C.
Normally the mixing time does not exceed one hour and a time in the range from 2 to 30 minutes is usually adequate. The mixing is suitably carried out in an internal mixer such as a Banbury mixer, or a Haake or Brabender miniature internal mixer. A two roll mill mixer also provides a good dispersion of the additives within the elastomer. An extruder also provides good mixing, and permits shorter mixing times. It is possible to carry out the mixing in two or more stages, and the mixing can be done in different apparatus, for example one stage in an internal mixer and one stage in an extruder. However, it should be taken care that no unwanted pre-crosslinking (= scorch) occurs during the mixing stage.
A curing bladder is made from the compound by first providing the peroxide curable rubber compound, incorporating the components of the peroxide curing system to the compound, forming the bladder using a mold or other suitable means and peroxide curing the curing bladder. The bladder may be peroxide cured by elevating the temperature of the bladder to a temperature sufficient to thermally activate the peroxide. The curing temperature of the curing bladder is typically in the range of 100 to 200 °C, preferably 130 to 180 °C.
The following Examples are provided to further illustrate the present invention and are meant to be construed in a non-limiting sense.

EXAMPLES
The Inventive Example compounds of the present invention are compared to a standard resin cure recipe (Comprative Compound). The standard cure formuation is disclosed in Table 1. Mixing was accomplished with the use of an internal mixer (black Banbury), consisting of a drive unit (Plasticorder~ Type PL-V151 ) and a data interface module. Cure characteristics were determined with a Moving Die Rheometer (MDR) test carried out according to ASTM standard D-5289 on a Monsanto MDR 200(E). The upper disc oscillated though a small arc of 1 degree. Curing was achieved with the use of an electric Press equipped with an Allan-Bradley Programmable Controller.
Table 1: Comparative Compound Butyl Rubber (LANXESS Butyl RB30195 phr ) Chloroprene (Baypren~ 116) 5 phr Carbon black (N330 Vulcan 3) 47 phr castor oil 5 phr Pentalyn~ A 3 phr Stearic Acid 0.5 phr Resin SP-1045 8 phr Zn0 6 phr Preparation of Polymers 1 and 2 Polymer 1 The monomer feed composition was comprised of 2.55 wt. % of isoprene and 27.5 wt. % of isobutene. The monomer feed was introduced into the continuous polymerization reactor at a rate of 5900 kg/hour. In additon, DVB was introduced into the reactor at a rate of 5.4 to 6kg/hour. Polymerization was initiated via the introduction of an AIC13/MeCI solution (0.23 wt. % of AICI3 in MeCI) at a rate of 204 to 227 kg/hour.
The internal temperature of the continuous reaction was mainted between -95 and -100 °C through the use of an evaporative cooling process. Following suffecient residence within the reactor, the newly formed polymer crumb was separated from the MeCI diluent with the use of an aqeous flash tank. At this point, ca. 1 wt. %
of stearic acid was introduced into the polymer crumb. Prior to drying, 0.1 wt. % of Irganox~ 1010 was added to the polymer. Drying of the resulting material was accomplished with the use of a conveyor oven.
Polymer 2 The monomer feed composition was comprised of 4.40 wt. % of isoprene and 25.7 wt. % of isobutene. The monomer feed was introduced into the continuous polymerization reactor at a rate of 5900 kg/hour. In additon, DVB was introduced into the reactor at a rate of 5.4 to 6 kg/hour. Polymerization was initiated via the introduction of an AICI3/MeCI solution (0.23 wt. % of AICI3 in MeCI) at a rate of 204 to 227 kg/hour.
The internal temperature of the continuous reaction was mainted between -95 and -100 °C through the use of an evaporative cooling process. Following suffecient residence within the reactor, the newly formed polymer crumb was separated from the MeCI diluent with the use of an aqeous flash tank. At this point, ca. 1 wt. %
of stearic acid was introduced into the polymer crumb. Prior to drying, 0.1 wt. % of Irganox~ 1010 was added to the polymer. Drying of the resulting material was accomplished with the use of a conveyor oven.
Inventive Compounds The formulations for Inventive Compounds in Examples 1, 2, 3 and 4 are disclosed in Tables, 2, 3, 4 and 5. Mixing was accomplished with the use of a miniature internal mixer (Brabender MIM) from C. W. Brabender, consisting of a drive unit (Plasticorder~ Type PL-V151 ) and a data interface module as disclosed in Tables 2-5.
Cure characteristics were determined with a Moving Die Rheometer (MDR) test carried out according to ASTM standard D-5289 on a Monsanto MDR 200(E). The upper disc oscillated though a small arc of 1 degree. Curing was achieved with the use of an electric Press equipped with an Allan-Bradley Programmable Controller.

Table 2: Example 1 (Inventive Compound 1~
Polymer 1 (5.0 mol % IP) 100 phr (0 min) Carbon black (N330 Vulcan~47 phr (1 min) 3) Peroxide (DI-CUP 40 C) 4 phr (4 min) Co-agent (HVA-2) 2.5 phr (4 min) Table 3: Example 2 (Inventive Compound 2~
Polymer 1 (5.0 mol % IP) 100 phr (0 min) Pentalyn~ A 3 phr (1 min) stearic acid 0.5 phr (1 min) Carbon black (N330 Vulcan~ 47 phr (1 min) 3) Peroxide (DI-CUP 40 C) 4 phr (4 min) Co-agent (SR-633) 14 phr (4 min) Table 4: Example 3 Inventive Compound 3~
Polymer 1 (4.2 mol % IP) 100 phr (0 min) Carbon black (N330 Vulcan~50 phr (1 min) 3) Peroxide (DI-CUP 40 C) 4 phr (4 min) Co-agent (HVA-2) 2 phr (4 min) Table 5: Example 5 Inventive Compound 5~
Polymer 2 (7.5 mol % 100 phr (0 IP) min) Carbon black (N550) 50 phr (4 min) carnauba wax 2 phr (8 min) Vulkanox~ 4020 LG (6PPD 1 phr (8 min) Vulkanox~ ZMB-2/C5 (ZMMBI)1 phr (8 min) Peroxide (DI-CUP 40 C) 4 phr (9 min) ' CA 02557217 2006-08-24 Co-agent (HVA-2) 3 phr (10 min) Table 6: Results Example ts1 ts2 t'90 4(MH-ML)Ult. Ult. M200 M300 M300/
[min][min] [min] [dN.m] Ten. Elong [MPa] [MPa] M100 [MPa] [%]

Comparativ3.66 6.72 45.61 8.68 11.21 825 2.34 3.42 2.19 a Example 0.72 0.96 3.76 9.35 5.69 289 3.69 - -Example 216 2.88 6.03 6.07 3.20 695 1.42 1.98 2.14 Example 0.90 1.38 4,90 8.05 8.10 442 2.82 5.43 4.72 Example 1.44 2.28 20.49 14.21 9.45 291 6.58 Compared to a typical resin cure recipe (Comparative), Examples 1-4 show much faster cure properties. Example 4 is slower in cure properties than the 3 other examples. Given that this seems to be induced by the addition of anti-oxidants (Vulkanox 4020LG, Vulkanox ZMB-2 C5), this provides an additional handle by which one can influence compound cure reactivity.
In addition to faster cure properties, peroxide cure systems have the benefit of not requiring the use of resins, which are inherently difficult to incorporate into the formulation.
The examples containing HVA-2 as a co-agent, i.e. Examples 1, 3 and 4, appear to present a superior degree of reinforcement, by evidence of M200 and M300/M100, when compared to the standard compound (Comparative).
Example 3 contains SR633 as a co-agent. The addition of SR633 seems to result in an increased ultimate elongation and a comparable degree of reinforcement (M300/M100), when compared to the standard.
These results indicate that using a mixture of co-agents might result in superior degree of reinforcement and ultimate elongation.

Further aspects or sub-combinations of the present invention will be evident to persons skilled in the art and are meant to be encompassed by the following claims.

Claims (19)

1. A curing bladder comprising a peroxide curable rubber compound comprising a peroxide curing agent and a polymer, wherein the polymer has a Mooney viscosity of at least 25 Mooney-units and a gel content of less than 15 wt.% and comprises repeating units derived from at least one isoolefin monomer, more than 4.1 mol%
of repeating units derived from at least one multiolefin monomer, as well as optionally further copolymerizable monomers, and repeating units derived from at least one multiolefin cross-linking agent containing no transition metal compounds and no organic nitro compounds.

2. The curing bladder according to Claim 1, wherein the polymer comprises greater than 5 mol % of repeating units derived from a multiolefin and a gel content of less than 10 wt. %.

3. The curing bladder according to Claim 1, wherein the polymer comprises greater than 7 mol % of repeating units derived from a multiolefin and a gel content of less than 5 wt. %.

4. The curing bladder according to Claim 1, wherein the isoolefin monomer is isobutene.

5. The curing bladder according to Claim 1, wherein the multiolefin crosslinking agent is divinylbenzene.

6. The curing bladder according to Claim 1, wherein the polymer is halogenated.

7. The curing bladder according to Claim 1, wherein the compound further comprises at least one filler.

8. A curing bladder made by:
a. providing a peroxide curable rubber compound comprising repeating units derived from at least one isoolefin monomer, at least 4.1 mol% of repeating units derived from at least one multiolefin monomer, and repeating units derived from at least one multiolefin cross-linking agent;
b. adding a peroxide curing system to the compound comprising at least a thermally activated peroxide and a peroxide curing co-agent;

c. forming the curing bladder from the peroxide curable rubber compound with the added peroxide curing system; and, d. peroxide curing the curing bladder.

9. The curing bladder according to claim 8, wherein the thermally activated peroxide comprises

10. The curing bladder according to claim 8, wherein the peroxide curing co-agent comprises HVA-2, SR-633, or a combination thereof.

11. The curing bladder according to claim 8, wherein the bladder is cured in the absence of an anti-oxidant.

12. The curing bladder according to claim 8, wherein the bladder has an ultimate elongation of less than 700%.

13. The curing bladder according to claim 8, wherein the bladder is cured at a temperature of from 130 to 180 °C.

14. The curing bladder according to claim 8, wherein the compound comprises greater than 5 mol % of repeating units derived from a multiolefin and a gel content of less than 10 wt. %.

15. The curing bladder according to claim 8, wherein the compound comprises greater than 7 mol % of repeating units derived from a multiolefin and a gel content of less than 5 wt. %.

16. The curing bladder according to claim 8, wherein the isoolefin monomer is isobutene and wherein the multiolefin monomer is isoprene.

17. The curing bladder according to claim 8, wherein the multiolefin crosslinking agent is divinylbenzene.

18. The curing bladder according to claim 8, wherein the compound comprises a halogenated butyl rubber polymer.

19. The curing bladder according to claim 8, wherein the compound further comprises at least one filler.