Rubber compound for a vibration dampening device

FIELD OF THE INVENTION

[0001] The present invention relates to an article useful to dampen and/or isolate vibrations generated by mechanical devices, wherein the article contains at least one peroxide curable compound containing a substantially gel-free butyl polymer. The present invention also relates to a substantially gel-free compound containing at least one polymer having repeating units derived from at least one isomonoolefin monomer, at least one multiolefin monomer or β-pinene, at least one multiolefin crosslinking agent and at least one chain transfer agent, at least one filler and a peroxide curing system. The present invention further relates to a compound containing a substantially gel-free polymer.

BACKGROUND OF THE INVENTION

[0002] Machines such as automobile, truck or jet engines, compressors and industrial air conditioners, automotive exhaust systems and similar dynamic devices generate significant vibration during operation. This vibration is transmitted directly to support structures where the dynamic devices is mounted or associated, e.g., an automobile or aircraft frame, a compressor frame, or a floor or rooftop. In order to minimize transfer of vibration from the operating dynamic device to the associated support structure, i.e., isolate the vibrations, it is common to interpose vibration damping and/or isolation means between the dynamic device and the associated support structure. Examples of such vibration damping and/or isolation means would be vibration-absorbing, elastomeric automobile or truck engine mounts placed between the brackets which are used to bolt the engine to the associated auto or truck frame, exhaust hangers, pads interposed between an air conditioner or compressor and a frame or floor and the like.

[0003] Another area where vibration damping is important is in the electronics industry, e.g., acoustic, computer-associated and game devices. The vibration from motorized equipment often radiates from the object as audible noise and potentially reduces performance or damages the instrument. Most portable electronics, CD drives and vehicle-mounted electronics are especially sensitive to vibration and shock and must be isolated from that energy to ensure proper performance.

[0004] Isolation mounts reduce the transmission of energy from one body to another by providing a resilient connection between them. Selecting an improper mount for an application, however, can actually make the problem worse. The incorrect mount may reduce the high frequency vibration, but resonant conditions at lower frequencies can actually amplify the induced vibration. During an impact, the mount deflects and returns some of the energy by rebounding. Preventing this energy return can extend product life and prevent performance problems such as skipping in a CD drive and read/write errors on a hard drive.

[0005] Adding dumping to a resilient mount greatly improves its responses. Damping reduces the amplitude of the resonant vibration by converting a portion of the energy into low-grade heat. Damping also dissipates shock energy during an impact.

[0006] Vibration damping and/or isolation materials known in the art include vulcanized objects in various shapes; e.g., squares, rectangles or cylinders prepared from vulcanized rubber. These dampening and/or isolation devices can be solid rubber, foamed rubber or solid rubber enclosing a fluid-containing cavity. Suitable rubbers which have been used in such applications include halogenated and non-halogenated butyl rubber, natural rubber and synthetic elastomeric polymers and copolymers of butadiene.

[0007] High damping properties of butyl rubber are well known and utilized. A large number of methyl groups along the macromolecular chains of the rubber interfere mechanically with one another and reduce the speed with which the molecules respond to deformation.

[0008] In many of its applications, a butyl rubber is used in the form of cured compounds. Vulcanizing systems usually utilized for butyl rubber include sulfur, quinoids, resins, sulfur donors and low-sulfur high performance vulcanization accelerators. However, sulfur residues in the compound are often undesirable, e.g., they promote corrosion of parts in contact with the compound.

[0009] The preferred vulcanization system is based on peroxides since this produces an article free of detrimental residues. In addition, peroxide-cured compounds offer higher thermal resistance compared to that of sulfur-cured materials. For example, engine mounts associated with modem engines must be able to withstand temperatures as high as 150° C. for periods in the range of 1,000 to 5,000 hours without significant loss of dynamic properties, in order to meet current and anticipated automotive standards. See U.S. Pat. Nos. 6,197,885-B1 and 5,904,220. It is recognized, however, that the sulfur-cured butyl rubber system has thermal stability of up to 120° C. vs. 150° C. for peroxide-cured butyl-based polymers. See JP-A-172547/1994.

[0010] If peroxides are used for crosslinking and curing of conventional butyl rubbers, the main chains of the rubber degrade and satisfactorily cured products are not obtained. As an alternative, pre-crosslinked butyl rubber such as commercially available Bayer® XL-10000 (or, formerly XL-20 and XL-50) can be crosslinked with peroxides, e.g., see Walker et al., “Journal of the Institute of the Rubber Industry”, 8 (2), 1974, 64-68. This specialty rubber is partially crosslinked with divinylbenzene in the polymerization stage, which proceeds via a cationic mechanism.

[0011] While said commercial pre-crosslinked polymers exhibit excellent properties in many applications in which they are used today, they have a gel content of at least 50 wt. % which sometimes makes the even dispersion of fillers and curatives normally used during vulcanization difficult. This increases the likelihood of under- and over-cured areas within the rubbery article, rendering its physical properties inferior and unpredictable. Also, the Mooney viscosity of this rubber is high, usually 60-70 units ML (1+8@125° C.) which may cause significant processing difficulties, especially in mixing and sheeting stages. To overcome this problem, processability-improving polymers are often added to the pre-crosslinked butyl rubber. Such polymers are particularly useful for improving the mixing or kneading property of a rubber composition. They include natural rubbers, synthetic rubbers (for example, IR, BR, SBR, CR, NBR, IIR, EPM, EPDM, acrylic rubber, EVA, urethane rubber, silicone rubber, and fluororubber) and thermoplastic elastomers (for example, of styrene, olefin, vinyl chloride, ester, amide, and urethane series). These processability-improving polymers may be used in the amount of up to 100 parts by weight, preferably up to 50 parts by weight, and most preferably up to 30 parts by weight, per 100 parts by weight of a partially crosslinked butyl rubber. However, the presence of other rubbers dilutes the desirable properties of butyl rubber.

[0012] In some special applications it is desirable to have a vibration-damping material with very low hardness. To lower the hardness of the article, large amounts of an extender component (50-200 parts) like paraffin process oil are added to the formulation. The damping characteristics of the extender may not be as good as of the rubber itself or the extender introduces its own undesirable characteristics to the final product (e.g., bleeding of oil).

[0013] Co-Pending Canadian Application CA-2,316,741 discloses polymers of isobutylene, isoprene, divinylbenzene (DVB) and a chain-transfer agent, such as diisobutylene, which are substantially gel-free and have an improved processability. However, this application is silent about peroxide curing and vibration dampening properties.

[0014] The rubbers utilized in the present invention display much lower Mooney viscosity (even below 10 units) and a very high solubility, including totally soluble materials. Due to these characteristics their processability is improved compared to commercial pre-crosslinked butyl polymers (ML ca. 60-70 units, solubility <50 wt. %). At the same time, this rubber modified with a chain-transfer agent is peroxide curable and imparts to the compounds the advantages of peroxide-cure system over sulfur-cure system.

SUMMARY OF THE INVENTION

[0015] The present invention provides a compound containing at least one elastomeric polymer comprising repeating units derived from at least one C4to C7 isomonoolefin monomer, at least one C4 to C14 multiolefin monomer or β-pinene, at least one multiolefin cross-linking agent and at least one chain transfer agent, said polymer containing less than 15 wt. % of solid matter insoluble within 60 min in cyclohexane boiling under reflux, at least one filler and a peroxide curing system.

[0016] The present invention relates to a compound comprising a substantially gel free polymer.

[0017] The present invention also relates to a substantially gel free compound.

[0018] The present invention also relates to a vulcanized rubber part useful to dampen and/or isolate vibrations generated by mechanical devices containing preferably a substantially gel-free peroxide-curable compound.

[0019] The present invention is also directed to a mechanical device containing a dynamic means which generates heat and/or vibrations and a static structure which supports the dynamic means and which is connected to the dynamic means and having a vulcanized rubber part containing the substantially gel-free peroxide-curable compound interposed between the dynamic means and the static structure at the point of connection.

[0020] Also, the present invention is directed to a motor or engine mount containing the substantially gel-free peroxide-curable compound.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention relates to butyl rubber polymers. The terms “butyl rubber”, “butyl polymer” and “butyl rubber polymer” are used throughout this specification interchangeably. While the prior art in using butyl rubber refers to polymers prepared by reacting a monomer mixture containing a C4to C7 isomonoolefin monomer and a C4 to C14 multiolefin monomer or β-pinene, the present invention relates to elastomeric polymers containing repeating units derived from at least one C4 to C7 isomonoolefin monomer, at least one C4 to C14 multiolefin monomer or β-pinene, at least one multiolefin cross-liking agent and at least one chain transfer agent. The butyl polymer of the present invention may be halogenated.

[0022] In connection with the present invention the term “substantially gel-free” is understood to denote a polymer containing less than 15 wt. % of solid matter insoluble within 60 min in cyclohexane boiling under reflux, preferably less than 10 wt. %, in particular less than 5 wt. %.

[0023] The present invention is not restricted to any particular C4 to C7 isomonoolefin monomers. Preferred C4 to C7 monoolefins include isobutylene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 4-methyl-1-pentene and mixtures thereof The more preferred C4 to C7 isomonoolefin monomer is isobutylene.

[0024] Furthermore, the present invention is not restricted to any particular C4 to C14 multiolefin. However conjugated or non-conjugated C4 to C14 diolefins are useful. Preferred C4 to C14 multiolefin monomers include isoprene, butadiene, 2-methylbutadiene, 2,4-dimethylbutadiene, piperyline, 3-methyl-1,3-pentadiene, 2,4-hexadiene, 2-neopentylbutadiene, 2-methly-1,5-hexadiene, 2,5-dimethly-2,4-hexadiene, 2-methyl-1,4-pentadiene, 2-methyl-1,6-heptadiene, cyclopentadiene, methylcyclopentadiene, cyclohexadiene, 1-vinyl-cyclohexadiene or mixtures thereof. The more preferred C4 to C14 multiolefin monomer is isoprene.

[0025] The present invention is also not restricted to any multiolefin cross-linking agent. Preferably, the multiolefin cross-linking agent is a multiolefinic hydrocarbon compound. Examples of these include norbornadiene, 2-isopropenylnorbornene, 5-vinyl-2-norbornene, 1,3,5-hexatriene, 2-phenyl-1,3-butadiene, divinylbenzene, diisopropenylbenzene, divinyltoluene, divinylxylene or C1 to C20 alkyl-substituted derivatives of the above compounds. More preferably, the multiolefin crosslinking agent is divinylbenzene, diisopropenyl-benzene, divinyltoluene, divinylxylene or C1 to C20 alkyl substituted derivatives of these compounds. Most preferably the multiolefin crosslinking agent is divinylbenzene or diisopropenylbenzene.

[0026] One skilled in the art will recognize the chemical formula for preferred multiolefin monomers and multiolefin cross-linking agents overlap. One skilled in the art will also appreciate that the difference between these compounds is a functional one. While a monomer is prone to propagating the chain in one dimension, a cross-linking agent will be prone to reacting with two or more chains instead. If a chemical compound reacts under the given conditions rather as a cross-linking agent or as a monomer is easily, unmistakably and directly available through some very limited preliminary experiments. While an increase in concentration of cross-linking agent will result in a directly related increase in cross-linking density in the polymer, an increase in concentration of a monomer will usually not affect the cross-linking density in the same way. Preferable multiolefin monomers will not result in crosslinking if present in an amount of up to 5 mol % in the reaction mixture.

[0027] The present invention is not restricted to any chain transfer agent. However, the chain transfer agent should preferably be a strong chain transfer agent i.e., it should be capable of reacting with the growing polymer chain, terminate its further growth and subsequently initiate a new polymer chain. The type and amount of chain transfer agent is dependent upon the amount of crosslinking agent. At low concentrations of crosslinking agent low amounts of chain transfer agent and/or a weak chain transfer agent can be employed. As the concentration of the crosslinking agent is increased, however, the chain transfer agent concentration should be increased and/or a stronger chain transfer agent should be selected. Use of a weak chain transfer agent should be avoided because too much can decrease the polarity of the solvent mixture and also would make the process uneconomical. The strength of the chain transfer agent may be determined conventionally, see, for example, J. Macromol. Sci.-Chem., A1(6) pp. 995-1004 (1967). A number called the transfer constant expresses its strength. According to the values published in this paper, the transfer constant of 1-butene is 0. Preferably, the chain transfer agent has a transfer coefficient of at least 10, more preferably at least 50. Non-limiting examples of useful chain transfer agents include piperylene, 1-methylcycloheptene, 1-methyl-1-cyclopentene, 2-ethyl-1-hexene, 2,4,4-trimethyl-1-pentene, indene and mixtures thereof. The most preferred chain transfer agent is 2,4,4-trimethyl-1-pentene.

[0028] Preferably, the monomer mixture to be polymerized contains in the range of from 65% to 98.98% by weight of at least one C4 to C7 isomonoolefin monomer, in the range of from 1.0% to 20% by weight of at least one C4 to C14 multiolefin monomer or β-pinene, in the range of from 0.01% to 15% by weight of a multifunctional cross-linking agent, and in the range of from 0.01% to 10% by weight of a chain-transfer agent. More preferably, the monomer mixture contains in the range of from 70% to 98.89% by weight of a C4 to C7 isomonoolefin monomer, in the range of from 1.0% to 10% by weight of a C4 to C14 multiolefin monomer or β-pinene, in the range of from 0.05% to 10% by weight of a multifunctional cross-linking agent, and in the range of from 0.05% to 10% by weight of a chain-transfer agent. Most preferably, the monomer mixture contains in the range of from 85% to 98.85% by weight of a C4 to C7 isomono-olefin monomer, in the range of from 1.0% to 5% by weight of a C4 to C14 multiolefin monomer or β-pinene, in the range of from 0.1% to 5% by weight of a multifunctional cross-linking agent, and in the range of from 0.05% to 5% by weight of a chain-transfer agent. It will be apparent to one skilled in the art that the total of all monomers will result in 100% by weight.

[0029] The monomer mixture may contain minor amounts of one or more additional polymerizable co-monomers. For example, the monomer mixture may contain a small amount of a styrenic monomer. Preferred styrenic monomers include p-methylstyrene, styrene, α-methyl-styrene, p-chlorostyrene, p-methoxy-styrene, indene (including indene derivatives) and mixtures thereof If present, it is preferred to use the styrenic monomer in an amount of up to 5.0% by weight of the monomer mixture. The values of the C4 to C7 isomonoolefin monomer(s) and/or the C4 to C14 multiolefin monomer(s) or β-pinene will have to be adjusted accordingly to result again in a total of 100% by weight.

[0030] The use of even other monomers in the monomer mixture is possible provided, of course, that they are copolymerizable with the other monomers in the monomer mixture.

[0031] The present invention is not restricted to a special process for preparing/polymerizing the monomer mixture. This type of polymerization is well known to those skilled in the art and usually includes contacting the reaction mixture described above with a catalyst system. Preferably, the polymerization is conducted at a temperature conventional in the production of butyl polymers, e.g., in the range of from −100° C. to +50° C. The polymer may be produced by polymerization in solution or by a slurry polymerization method. Polymerization is preferably conducted in suspension (the slurry method), see, for example, Ullmann's Encyclopedia of Industrial Chemistry (Fifth, Completely Revised Edition, Volume A23; Editors Elvers et al., 290-292).

[0032] The present inventive polymer preferably has a Mooney viscosity ML (1+8@125° C.) in the range of from 5 to 40 units, more preferably in the range of from 7 to 35 units.

[0033] As an example, the polymerization is conducted in the presence of an inert aliphatic hydrocarbon diluent (such as n-hexane) and a catalyst mixture containing a major amount (in the range of from 80 to 99 mole percent) of a dialkylaluminum halide (for example diethylaluminum chloride), a minor amount (in the range of from 1 to 20 mole percent) of a monoalkylaluminum dihalide (for example isobutylaluminum dichloride), and a minor amount (in the range of from 0.01 to 10 ppm) of at least one of a member selected from the group of water, aluminoxane (for example methylaluminoxane) and mixtures thereof. Of course, other catalyst systems conventionally used to produce butyl polymers can be used to produce a butyl polymer which is useful herein, see, for example, “Cationic Polymerization of Olefins: A Critical Inventory” by Joseph P. Kennedy (John Wiley & Sons, Inc.© 1975, 10-12).

[0034] Polymerization may be performed both continuously and discontinuously. In the case of continuous operation, the process is preferably performed with the following three feed streams:

[0035] I) solvent/diluent+isomonoolefin(s) (preferably isobutene)

[0036] II) multiolefin(s) (preferably diene, isoprene), multifunctional cross-linking agent(s)and chain-transfer agent(s)

[0037] III) catalyst

[0038] In the case of discontinuous operation, the process may, for example, be performed as follows: The reactor, pre-cooled to the reaction temperature, is charged with solvent or diluent and the reactants. The initiator is then pumped in the form of a dilute solution in such a manner that the heat of polymerization may be dissipated without problem. The course of the reaction may be monitored by means of the evolution of heat.

[0039] The polymer may be halogenated. Preferably, the halogenated butyl polymer is brominated or chlorinated. Preferably, the amount of halogen is in the range of from 0.1 to 8%, more preferably from 0.5% to 4%, most preferably from 1.0% to 3.0%, by weight of the polymer. The halogenated tetrapolymer will can be produced by halogenating a previously-produced tetrapolymer derived from the monomer mixture described hereinabove. However, other possibilities are well known to those skilled in the art. One method to produce a halogenated tetrapolymer is disclosed in U.S. Pat. No. 5,886,106. The halogenated butyl rubber may be produced either by treating finely divided butyl rubber with a halogenating agent such as chlorine or bromine, or by producing brominated butyl rubber by the intensive mixing, in a mixing apparatus, of brominating agents such as N-bromosuccinimide with a previously made butyl rubber. Alternatively, the halogenated butyl rubber may be produced by treating a solution or a dispersion in a suitable organic solvent of a previously made butyl rubber with corresponding brominating agents. See, Ullmann's Encyclopedia of Industrial Chemistry (Fifth, Completely Revised Edition, Volume A23; Editors Elvers et al., 314, 316-317). The amount of halogenation during this procedure may be controlled so that the final polymer has the preferred amounts of halogen described hereinabove.

[0040] The compound further contains at least one active or inactive filler. The filler is preferably:

[0041] highly dispersed silicas, prepared e.g., by the precipitation of silicate solutions or the flame hydrolysis of silicon halides, with specific surface areas of in the range of from 5 to 1000 m2/g, and with primary particle sizes of in the range of from 10 to 400 nm; the silicas can optionally also be present as mixed oxides with other metal oxides such as those of Al, Mg, Ca, Ba, Zn, Zr and Ti;

[0042] synthetic silicates, such as aluminum silicate and alkaline earth metal silicate like magnesium silicate or calcium silicate, with BET specific surface areas in the range of from 20 to 400 m2/g and primary particle diameters in the range of from 10 to 400 nm;

[0043] natural silicates, such as kaolin and other naturally occurring silica;

[0044] glass fibers and glass fiber products (matting, extrudates) or glass microspheres;

[0045] metal oxides, such as zinc oxide, calcium oxide, magnesium oxide and aluminum oxide;

[0046] metal carbonates, such as magnesium carbonate, calcium carbonate and zinc carbonate;

[0047] metal hydroxides, e.g. aluminum hydroxide and magnesium hydroxide;

[0048] carbon blacks; the carbon blacks to be used here are prepared by the lamp black, furnace black or gas black process and have preferably BET (DIN 66 131) specific surface areas in the range of from 20 to 200 m2/g, e.g. SAF, ISAF, HAF, FEF or GPF carbon blacks;

[0049] rubber gels, especially those based on polybutadiene, butadiene/styrene copolymers, butadiene/acrylonitrile copolymers and polychloroprene;

[0050] or mixtures thereof

[0051] Examples of preferred mineral fillers include silica, silicates, clay such as bentonite, gypsum, alumina, titanium dioxide, talc, mixtures of these, and the like. These mineral particles have hydroxyl groups on their surface, rendering them hydrophilic and oleophobic. This exacerbates the difficulty of achieving good interaction between the filler particles and the tetrapolymer. For many purposes, the preferred mineral is silica, more preferably silica made by carbon dioxide precipitation of sodium silicate. Dried amorphous silica particles suitable for use in accordance with the present invention may have a mean agglomerate particle size in the range of from 1 to 100 microns, preferably between 10 and 50 microns and more preferably between 10 and 25 microns. It is preferred that less than 10 percent by volume of the agglomerate particles are below 5 microns or over 50 microns in size. A suitable amorphous dried silica moreover usually has a BET surface area, measured in accordance with DIN (Deutsche Industrie Norm) 66131, of in the range of from 50 and 450 square meters per gram and a DBP absorption, as measured in accordance with DIN 53601, of in the range of from 150 and 400 grams per 100 grams of silica, and a drying loss, as measured according to DIN ISO 787/11, of in the range of from 0 to 10 percent by weight. Suitable silica fillers are available under the trademarks HiSil® 210, HiSil® 233 and HiSil® 243 from PPG Industries Inc. Also suitable are Vulkasil S and Vulkasil N, from Bayer AG.

[0052] It might be advantageous to use a combination of carbon black and mineral filler in the present inventive compound. In this combination the ratio of mineral fillers to carbon black is usually in the range of from 0.05 to 20, preferably 0.1 to 10. For the rubber composition of the present invention it is usually advantageous to contain carbon black in an amount of in the range of from 20 to 200 parts by weight, preferably 30 to 150 parts by weight, more preferably 40 to 100 parts by weight.

[0053] The compound further contains at least one peroxide curing system. The present invention is not limited to a special peroxide curing system. For example, inorganic or organic peroxides are suitable. 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-trimethylcyclohexane, benzoylperoxide, tert.-butylcumylperoxide and tert.-butylper-benzoate. 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 preferably in a polymer-bound form Suitable systems are commercially available, such as Polydispersion T(VC) D-40 P from Rhein Chemie Rheinau GmbH, D (polymerbound di-tert.-butylperoxy-isopropylbenzol).

[0054] Even if it is not preferred, the compound may further contain other natural or synthetic rubbers such as BR (polybutadiene), ABR (butadiene/acrylic acid-C1-C4-alkylester-copolymers), CR (polychloroprene), IR (polyisoprene), SBR (styrene/butadiene-copolymers) with styrene contents in the range of 1 to 60 wt. %, NBR (butadiene/acrylonitrile-copolymers with acrylonitrile contents of 5 to 60 wt. %, HNBR (partially or totally hydrogenated NBR-rubber), EPDM (ethylene/propylene/diene-copolymers), FKM (fluoropolymers or fluororubbers), and mixtures of the given polymers.

[0055] The rubber composition according to the present invention can contain further auxiliary products for rubbers, such as reaction accelerators, vulcanizing accelerators, vulcanizing acceleration auxiliaries, antioxidants, foaming agents, anti-aging agents, heat stabilizers, light stabilizers, ozone stabilizers, processing aids, 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, for example, from 0.1 to 50 wt. %, based on rubber. Preferably the composition further 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.

[0056] The ingredients of the final compound are 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. For compounding and vulcanization see also, Encyclopedia of Polymer Science and Engineering, Vol. 4, p. 66 et seq. (Compounding) and Vol. 17, p. 666 et seq. (Vulcanization).

[0057] Furthermore, the present invention provides shaped rubber parts, either solid, foamed, or fluid filled useful to isolating vibrations and dampening vibrations generated by mechanical devices containing the present inventive compound. The present invention also provides mechanical devices containing a dynamic means which generates heat and/or vibrations, e.g., an automotive engine, an electric motor, and a static structure which supports said dynamic means, e.g., an automotive frame, and which is connected to said dynamic means, e.g., by bolting together brackets attached to the frame and engine, and having a vulcanized rubber vibration, isolation, and/or damping part interposed between said dynamic means and said static structure at said point of connection, e.g., one or more disc-shaped rubber parts sandwiched between the engine and frame brackets. The improvement provided by the present invention includes the utilization as the rubber part of a shaped, vulcanized composition containing the peroxide curable rubber compound. Vulcanization of a molded article, for example a motor mount, may be carried out in heated presses under conditions well known to those skilled in the art. Curing time will be affected by the thickness of the article and the concentration and type of curing agent as well as the initial halogen content of the halogenated polymer in case a halogenated polymer is to be used. However, the vulcanization parameters can readily be established with a few experiments utilizing e.g., a laboratory characterization device well known in the art, the Monsanto Oscillating Disc Cure Rheometer (described in detail in American Society for Testing and Materials, Standard ASTM D 2084). Alternatively, the curable composition can be injection molded to form shaped articles and held in the mold for a sufficient time to form a cured, shaped article.

[0058] The composition of the present invention may be used in producing vibration damping and/or isolation parts used to isolate or decrease the effect of vibrations from motor, engines and the like. It is preferably suitable for use in the production of elastomeric mountings for control of vibration, for example automotive body and engine mounts; automotive exhaust hangers; dynamic absorbers (e.g., shock absorbers); bushings; automotive suspension bumpers, and the like.

[0059] The compositions are especially useful in the assembly of automotive engine mounts, which are subjected to high operating temperatures of up to about 150 deg.C. In such an application, molded parts in the shape of discs are interposed between motor and auto frame brackets prior to bolting the brackets together to secure the motor to the frame. For especially high-quality isolation use of hydromounts, i.e., rubber enclosing a fluid, is desirable. The enclosed liquids are generally high boiling. Typically, the liquids are selected from glycols such as ethylene glycol and propylene glycol. The compositions are also useful as part of electronic systems subjected to vibration and high operating temperatures of up to ca. 150° C., e.g., in vehicle-mounted electronics.

[0060] The present invention is further illustrated by the following examples.

EXAMPLES

[0061] Methyl chloride (Dow Chemical) serving as a diluent for polymerization and isobutylene monomer (Matheson, 99%) were transferred into a reactor by condensing a vapor phase. Aluminum chloride (99.99%), isoprene (99%) and 2,4,4-trimethyl-1-pentene (97%) were from Aldrich. The inhibitor was removed from isoprene by using an inhibitor removing disposable column from Aldrich. Commercial divinylbenzene (ca. 64%) was from Dow Chemical.

[0062] The mixing of a compound with carbon black (IRB #7) and peroxide (DI-CUP 40C, Struktol Canada Ltd.) was done using a miniature internal mixer (Brabender MIM) from C. W. Brabender, consisting of a drive unit (Plasticorder® Type PL-V151) and a data interface module.

[0063] The Mooney viscosity test was carried out according to ASTM standard D-1646 on a Monsanto MV 2000 Mooney Viscometer ML (1+8@ 125° C.).

[0064] The Moving Die Rheometer (MDR) test was performed according to ASTM standard D-5289 on a Monsanto MDR 2000 (E). The upper die oscillated through a small arc of 1 degree.

[0065] The solubility of a polymer was determined after the sample refluxed in cylohexane over 60-minute period.

[0066] Curing was done using an Electric Press equipped with an Allan-Bradley Programmable Controller.

[0067] Stress-strain tests were carried out using the Instron Testmaster Automation System, Model 4464.

Example 1

[0068] A commercially available pre-crosslinked butyl polymer (XL-10000) having a content of a soluble fraction of 25.2 wt. % and Mooney viscosity of 63.6 units ML (1+8@125° C.) was compounded using the following recipe:

[0069] Polymer: 100 phr

[0070] Carbon black (IRB#7): 50 phr

[0071] Peroxide: (DI-CUP 40C): 1.0 phr

[0072] The mixing was done in a Brabender internal mixer (capacity ca. 75 cc). The starting temperature was 60° C. and the mixing speed 50 rpm. The following steps were carried out:

[0073] 0 min: polymer added

[0074] 1.5 min: carbon black added, in increments

[0075] 7.0 min: peroxide added

[0076] 8.0 min: mix removed

[0077] The obtained compound was passed through a mill (6″×12″) six times with a tight nip gap.

[0078] The compound (Compound 1) was subsequently cured at 160° C. and tested. The Shore A2 hardness was 58 points and the ultimate elongation 152%.

Example 2

[0079] To a 50 mL Erlenmeyer flask, 0.45 g of AlCl3 was added, followed by 100 mL of methyl chloride at −30° C. The resulting solution was stirred for 30 min at −30° C. and then cooled down to −95° C., thus forming the catalyst solution.

[0080] To a 2000 mL glass reactor equipped with an overhead stirrer, 900 mL of methyl chloride at −95° C. were added, followed by 100.0 mL isobutylene at −95° C., 3.0 mL of isoprene at room temperature, 1.96 mL of commercial DVB at room temperature, and 1.82 mL of 2,4,4-trimethyl-1-pentene at room temperature. The reaction mixture was cooled down to −95° C. and 10.0 mL of the catalyst solution was added to start the reaction.

[0081] The reaction was carried out in MBRAUN® dry box under the atmosphere of dry nitrogen. The reaction was terminated after 5 minutes by adding into the reaction mixture 10 mL of ethanol containing some sodium hydroxide.

[0082] The obtained polymer was steam coagulated and dried on a 6″×12″ mill at ca. 105° C. followed by drying in a vacuum oven at 50° C. to a constant weight. The Mooney viscosity of the rubber was 8.1 units (1′+8′@125° C.) and the solubility in cyclohexane was 97.9 wt. %.

[0083] The polymer was compounded using the same recipe and methodology given in Example 1. The compound (Compound 2) was subjected to curing at 160° C. and tested. The Shore A2 hardness was 26 points and the ultimate elongation 699%.

[0084] This example demonstrates that the substantially gel-free polymer can be used to obtain a peroxide cured compound with a significantly lower hardness compared to the one based on commercial XL-10000. Since this polymer with low Mooney viscosity becomes chemically incorporated upon curing it could be used instead of a process oil without any bleeding problems associated with the use of ‘traditional’ extenders.

Example 3

[0085] Polymer 3 was obtained in the same way as Polymer 2 described in Example 2, except that 4.0 mL of DVB and 3.0 mL of 2,4,4-trimethyl-1-pentene were used in the present case. The Mooney viscosity of the rubber was 7.5 units (1′+8′@125° C.) and the solubility in cyclohexane was 98.0 wt. %. Therefore, these two raw polymer characteristics were virtually identical for Polymer #2 and Polymer #3.

[0086] The polymer 3 was compounded using the same recipe and methodology given in Example 1. The compound (Compound 3) was subjected to curing at 160° C. and tested. The Shore A2 hardness was 41 points and the ultimate elongation 284%.

[0087] This example shows that although the Mooney viscosity and solubility of the polymer 3 were very similar to those of polymer 2, the properties of the cured compounds were quite different. In the present case, the Shore A2 hardness was much higher and the ultimate elongation was much lower than the corresponding properties for the Compound #2. Therefore, by properly adjusting the composition of the reaction feed (in particular, the content of DVB and the chain transfer agent) it is possible to prepare a range of easily processible, peroxide-curable materials with designed properties for specific applications.

[0088] Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Rubber compound for a vibration dampening device

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