FIELD OF THE INVENTION 0001 The present invention relates to rubber mixtures and rubber vulcanates, produced therefrom, based on uncrosslinked butyl rubber and on acrylonitrile-containing rubber particles (so-called rubber gels, gels or microgels). The rubber mixtures according to the present invention are suitable for the production of rubber vulcanates having low gas permeability and acceptable mechanical properties, the mixtures exhibiting good processability.

BACKGROUND OF THE INVENTION 0002 The vulcanates produced from the rubber mixtures according to the present invention additionally have a low density, which has an advantageous effect on the weight of the molded rubber bodies produced from the vulcanates, such as, for example, tire tubes, inner linings and gas-impermeable protective equipment, such as ABC protective clothing. 0003 It is known that conventional fillers such as carbon black or silica in rubber mixtures can be replaced quantitatively or partially by rubber gels. Because of the low density of rubber gels (p<1 g/cm3), the corresponding vulcanates have a lower weight than mixtures filled with carbon black (p <1.8 g/cm3) or with silica (p<2.1 g/cm3). In addition, when polybutadiene-based rubber gels are used (BR gels), high rebound resilience is found both at room temperature and at 70 C. Such vulcanates can be used for the production of low-damping rubber articles, especially low-damping tire components. When SBR-based rubber gels are used, the corresponding vulcanates are found to have low rebound resilience at room temperature and high rebound resilience at 70 C. Corresponding vulcanates are suitable, for example, for tire treads having an advantageous wet-skid behavior/rolling resistance relation. 0004 Reference is made in this connection, for example, to U.S. Pat. Nos. 5,124,408 and 5,395,891, DE-A 197 01 488.7, DE-A 199 29 347.3, DE-A 199 39 865.8, DE-A 199 42 620.1. 0005 The use of NBR gels in mixtures of double-bond-containing rubbers is also known (DE-A 19701487.9). The patent applications cited above do not teach the use of rubber gels, especially of NBR gels in admixture with butyl rubber, which are suitable for the production of vulcanates having low gas permeability, good processability and low weight. 0006 The gas permeability coefficients of various vulcanized rubbers, and especially the low gas permeability of butyl rubbers, are known (gas permeability coefficients according to DIN 53536, see Handbuch fr die Gummiindustrie, Bayer AG, 1991, p. 720). Because of their low gas permeability, butyl rubber and the halogenated (chlorinated and brominated) butyl rubbers are used in the production of rubber articles, such as, for example, tire tubes, inner linings as well as ABC protective equipment. The effect of the various compound constituents on the gas permeability of the vulcanized articles is also known (Handbuch fr die Gummiindustrie, Bayer AG, 1991, p. 207-230). Compromises have to be made in order to meet various target values. One such compromise is that, in order to improve the viscosity of the mixture, it is necessary to use oils, which increase the gas permeability. 0007 Mixtures based on butyl rubber have hitherto been filled with the conventional high-density fillers, such as carbon black or silica, the gas permeability of the vulcanates falling as the amount of filler increases. Polymeric fillers, such as, for example, rubber gels, have hitherto not been used, possibly because of the prejudice that polymeric fillers increase the gas permeability.

SUMMARY OF THE INVENTION 0008 The technical object was, therefore, to find measures permitting the production of rubber articles having low gas permeability, low weight and good processability of the compounds while having acceptable mechanical properties. 0009 It has been found that this aim is achieved with rubber mixtures that contain uncrosslinked butyl rubbers and nitrile-containing rubber gels. 0010 Accordingly, the present invention provides rubber mixtures comprising uncrosslinked butyl rubbers (A) and crosslinked, nitrile-containing rubber particles (B), the amount of component (B) in the mixture, based on 100 parts by weight (phr) of the rubber component (A), being from 1 to 150 parts by weight.

DETAILED DESCRIPTION OF THE INVENTION 0011 The present invention provides rubber mixtures comprising uncrosslinked butyl rubbers (A) and crosslinked, nitrile-containing rubber particles (B), the amount of component (B) in the mixture, based on 100 parts by weight (phr) of the rubber component (A), being from 1 to 150 parts by weight, preferably from 5 to 100 parts by weight. 0012 Uncrosslinked butyl rubbers (A) are to be understood as being butyl rubber (IIR), brominated butyl rubber (BIIR) and chlorinated butyl rubber (CIIR). Butyl rubbers and halogenated butyl rubbers are described in Ullmann's Encyclopedia of Industrial Chemistry, Vol. A 23 (1993) p. 288 ff and p. 314 ff. 0013 Butyl rubber IIR is a copolymer of isobutylene with dienes such as isoprene, cyclopentadiene, pentadiene, butadiene and divinylbenzene, having a diene content of approximately from 0.5 to 10 mol. %. The preferred diene component in the butyl rubber is isoprene. Halogenated butyl rubber is obtained by chlorination (CIIR) or by bromination (BIIR) of butyl rubber and has a halogen content of approximately from 0.5 to 10 mol. %. Halobutyl rubbers are also to be understood as being terpolymers which are obtained by halogenation of isobutene/isoprene/divinylbenzene terpolymers having a divinylbenzene content of approximately from 0.5 to 5 mol. %, as well as halogenated isobutylene/p-methylstyrene copolymers having p-methylstyrene contents of approximately from 0.5 to 10 mol. %. 0014 The halogenated and the unhalogenated butyl rubbers may be used individually or in a mixture with one another, the mixing ratio depending on the particular intended use of the mixtures. 0015 Nitrile-containing rubber particles (B) are to be understood as being NBR gels as described, for example, in DE-A 19701487.9. NBR gels are usually composed of the monomers acrylonitrile, methacrylonitrile, butadiene, styrene, divinylbenzene, vinylpyridine, 2-chlorobutadiene, 2,3-dichlorobutadiene, as well as bisacrylates or bismethacrylates, such as ethylene glycol dimethacrylate and butanediol dimethacrylate, as well as a carboxyl-group-containing monomer, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid. Preference is given to nitrile-containing gels that contain, in addition to the above-mentioned monomers, contents of acrylonitrile or methacrylonitrile in amounts of approximately from 5 to 80 wt. %. They include NBR gels based on butadiene/acrylonitrile copolymers (NBR) having acrylonitrile contents of from 15 to 60 wt. %, as well as the corresponding carboxylated gels (XNBR gels), which additionally contain carboxyl-group-containing monomers in amounts of approximately from 0.5 to 15 wt. %. 0016 The rubber particles to be used according to the present invention usually have particle diameters of from 5 to 1000 nm, preferably from 10 to 600 nm (data relating to diameters are according to DIN 53 206). Because they are crosslinked, they are insoluble and are swellable in suitable solvents, for example, toluene. The swelling indices of the rubber particles (QI) in toluene are approximately from 1 to 15, preferably from 1 to 10. The swelling index is calculated from the weight of the solvent-containing gel (after centrifugation at 20,000 rpm) and the weight of the dry gel, where QIwet weight of the gel/dry weight of the gel. The gel content of the rubber particles according to the present invention is usually from 80 to 100 wt. %, preferably from 90 to 100 wt. %. 0017 The rubber mixtures according to the present invention may contain further known rubber auxiliary substances and fillers. Especially suitable fillers for the production of the rubber mixtures or vulcanates according to the present invention are, for example: 0018 carbon blacks. The carbon blacks to be used have been prepared by the flame carbon black, furnace or gas carbon black process and have BET surface areas of from 20 to 200 m2/g, such as, for example, SAF, ISAF, IISAF, HAF, FEF or GPF carbon blacks and graphite. 0019 highly dispersed silica, prepared, for example, by precipitation of solutions of silicates or flame hydrolysis of silicon halides having specific surface areas of from 5 to 1000 m2/g, preferably from 20 to 400 m2/g (BET surface area) and primary particle sizes from 5 to 400 nm. The silicas may optionally also be present in the form of mixed oxides with other metal oxides, such as Al, Mg, Ca, Ba, Zn and Ti oxides. 0020 synthetic silicates, such as aluminum silicate, alkaline-earth silicates, such as magnesium silicate or calcium silicate having BET surface areas of from 20 to 400 m2/g and primary particle diameters of from 5 to 400 nm. 0021 natural silicates, such as kaolin (clay) and other naturally occurring silicas. 0022 metal oxides, such as zinc oxide, calcium oxide, magnesium oxide, aluminum oxide. 0023 metal carbonates, such as calcium carbonate, magnesium carbonate, zinc carbonate. 0024 metal sulfates, such as calcium sulfate, barium sulfate. 0025 metal hydroxides, such as aluminum hydroxide and magnesium hydroxide. 0026 glass fibers and glass fiber products (laths, threads or glass 0027 microspheres). 0028 thermoplastic fibers (polyamide, polyester, aramid). 0029 The fillers may be used in amounts of from 0.1 to 100 parts by weight, based on 100 parts by weight of the rubber component A. 0030 The mentioned fillers may be used alone or in a mixture with one another. 0031 Special preference is given to rubber mixtures containing from 10 to 100 parts by weight of crosslinked nitrile-group-containing rubber particles (component B), from 0.1 to 100 parts by weight of carbon black and/or from 0.1 to 100 parts by weight of so-called light fillers of the abovementioned type, in each case based on 100 parts by weight of the rubber component (A). When a mixture of rubber gel, carbon black and light fillers is used, the amount of fillers is not more than approximately 150 parts by weight. 0032 The rubber mixtures according to the present invention mayas mentionedcontain further rubber auxiliary substances, such as crosslinking agents, vulcanization accelerators, anti-aging agents, heat stabilizers, light stabilizers, anti-ozonants, processing aids, plasticizers, tackifiers, blowing agents, colorings, pigments, wax, extenders, organic acids, retarding agents, metal oxides, as well as filler activators, such as triethanolamine, polyethylene glycol, hexanetriol, bis-(triethoxysilylpropyl) tetrasulfide. The rubber auxiliary substances are described, for example, in Butyl and Halobutyl Compounding Guide for non-tire Applications 12/92 Rubber business group, and in Handbuch fr die Gummiindustrie, Bayer AG, 2nd edition, 1991. 0033 The rubber auxiliary substances are used in conventional amounts, which are dependent inter alia on the intended use. Conventional amounts are, for example, from 0.1 to 50 parts by weight, based on 100 parts by weight of rubber (A). 0034 The rubber mixtures according to the present invention may also contain conventional crosslinking agents, such as sulfur, sulfur donors, peroxides or other crosslinking agents, such as diisopropenylbenzene, divinylbenzene, divinyl ether, divinylsulfone, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene, N,N-m-phenylenemaleimide and/or triallyl trimellitate. In addition, there come into consideration also the acrylates and methacrylates of polyhydric, preferably from di- to tetra-hydric, C2 to C10 alcohols, such as ethylene glycol, propanediol-1,2-butanediol, hexanediol, polyethylene glycol having from 2 to 20, preferably from 2 to 8, oxyethylene units, neopentyl glycol, bisphenol A, glycerol, trimethylpropane, pentaerythritol, sorbitol with unsaturated polyesters of aliphatic diols and polyols as well as maleic acid, fumaric acid and/or itaconic acid. 0035 Crosslinking agents, which are preferably used, are sulfur and sulfur donors in the known amounts, for example in amounts of from 0.1 to 10 parts by weight, preferably from 0.5 to 5 parts by weight, based on 100 parts by weight of rubber component (A). 0036 The rubber mixtures according to the present invention may also contain vulcanization accelerators of the known type, such as mercaptobenzothiazoles, mercaptosulfenamides, guanidines, thiurams, dithiocarbamates, thioureas, thiocarbonates and/or dithiophosphates. The vulcanization accelerators, like the crosslinking agents, are used in amounts of approximately from 0.1 to 10 parts by weight, preferably from 0.1 to 5 parts by weight, based on 100 parts by weight of rubber component (A). 0037 The rubber mixtures according to the present invention can be prepared in a known manner, for example by mixing the individual solid components in apparatuses suitable therefor, such as mills, internal mixers or mixing extruders. Blending of the individual components with one another is usually carried out at mixing temperatures of from 20 to 100 C. 0038 The rubber mixtures according to the present invention can also be produced by from the latexes of the rubber component (A) and component (B) in latex form and mixing the other components into the latex mixture (components AB) and then working up the mixture by conventional operations, such as concentration by evaporation, precipitation or freeze-coagulation. 0039 The goal when producing the rubber mixture according to the present invention is, above all, to mix the components of the mixture with one another intimately and to achieve good dispersion of the fillers used in the rubber matrix. 0040 The rubber mixtures according to the present invention are suitable for the production of rubber vulcanates by corresponding crosslinking reactions with the known crosslinking agents, and are used in the production of molded bodies of all kinds, especially in the production of rubber articles such as tire tubes, inner linings, protective clothing, pharmaceutical stoppers, tank linings, damping elements, gaskets, hoses, conveyor belts and membranes.

EXAMPLES 0041

1TABLE 1Densityof theAcrylo-Dia-latexGelnitrileAmountmeterparti-con-NBRcontentof DCPd50clestentTgtypewt. %phrGelnmg/cm3%QI C.2830a)2801170.96443.311.836.52830a)283(1)1100.9697976.929OBR1085c)3945b)3901030.985982.44.9213945b)393(2)1030.999998510.5OBR1086d)a)Perbunan NT 2830 from Bayer AG (nitrile rubber containing 28 wt. % acrylonitrile, Mooney viscosity at 100 C.: 30 ME) b)Perbunan NT 3945 from Bayer AG (nitrite rubber containing 39 wt. % acrylonitrile, Mooney viscosity at 100 C.: 45 ME) c)Nitrite rubber gel based on Perbunan NT 2830 latex, obtained by crosslinking with 3 phr dicumyl peroxide (DCP) d)Nitrile rubber gel based on Perbunan NT 3945 latex, obtained by crosslinking with 3 phr dicumyl peroxide (DCP)

0042 Production of the Rubber Mixtures, Vulcanization thereof, and the Measured Physical Values of the Vulcanates 0043 In order to demonstrate the effects according to the present invention, the following compounds were used: 0044 Series of Mixtures The mixture constituents listed in the following table (amounts are given in phr) were mixed in the conventional manner in a laboratory mill. 2TABLE 2Mixture no.:123456Bromobutyl 20301)100100100100100100Carbon black N 6606060OBR 1085c)6060OBR 1086c)6060Paraffin oil2)777Resin3)444444Stearic acid111111MBTS4)1.31.31.31.31.31.3Zinc oxide333333Sulfur0.50.50.50.50.50.51)Bromobutyl rubber from Bayer Inc. Canada 2)Sunpar 2280 from Sunoco Inc. 3)Pentalyn A from Hercules Inc. 4)Dibenzthiazyl disulfide (Vulkacit DM from Bayer AG)

0045 The following parameters were determined on the unvulcanized mixture: 3TABLE 3Mixture no.:123456Compound Mooney ML6272546456661 4/100 C.Mooney relaxation5.55.18.911.2910.8MR 30 %Monsanto tack N2.22.31.41.51.21.8

0046 The vulcanization behavior of the mixtures is tested in a rheometer at 165 C. according to DIN 53 529 with the aid of the Monsanto rheometer MDR 2000E. Characteristic data such as Fa, Fmax, Fmax-Fa, t50 and t90 were thus determined. 4TABLE 4Mixture no.:123456Fa dNM1.71.81.82.21.82.3Fmax dNM7.18.03.74.33.33.9Fmax Fa dNM5.46.21.92.11.51.6t50 min.3.23.15.355.65t90 min.8.78.519.819.421.320.1According to DIN 53 529, Part 3: Fa vulcameter reading at the minimum of the crosslinkage isotherm Fmax maximum vulcameter reading Fmax Fa difference between the maximum and minimum vulcameter readings t50 time at which 50% of conversion is achieved t90 time at which 90% of conversion is achieved

0047 The mixtures were vulcanized in a press for 30 minutes at 165 C. The following properties of the vulcanates were determined: TABLE 5 5TABLE 5Mixture no.:123456Tensile strength (F) MPa8.910.511.511.58.811.8Ultimate elongation (D) %670650482521369470Tensile stress at 50% elongation0.80.91.81.43.50.8(S50) MPaTensile stress at 100% elongation1.11.72.72.14.31.5(S100) MPaTensile stress at 300% elongation4.05.46.65.47.66(S300) MPaShore A hardness, 23 C.586030332933Shore A hardness, 70 C.404723272024Rebound resilience 99181999at 23 C. (E23) %Rebound resilience293057595756at 70 C. (E70 ) %Air permeability at 70 C.3.02.34.743.22.7(DIN 53536) m2/s Pa

0048 Result: 0049 In the present series of mixtures it is shown that, when the filler carbon black is replaced by NBR gels, rubber compounds are obtained that exhibit good processability (low compound viscosities) and acceptable mechanical properties in the vulcanized state, coupled with low gas permeabilitythe gas permeability of the vulcanate falling as the acrylonitrile content of the NBR gel increases. 0050 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.