Rubber mixture containing polyethyleneimine

Abstract

The present invention relates to novel rubber mixtures based on polychloroprene rubber and polyethyleneimine, to their preparation and use, and to the vulcanizates obtainable therewith.

Description

[Technical Field]

[0001] The present invention relates to novel rubber mixtures based on polychloroprene rubber and polyethyleneimine, to a process for their production, to their use for producing rubber vulcanizates by vulcanization, and to molded articles obtainable therefrom, in particular in the form of industrial vulcanizates, such as, for example, hoses, cable sheaths or belts. [Background technology]

[0002] Polychloroprene is a useful rubber that is used in many areas.

[0003] It is known to use certain crosslinking agents to crosslink polychloroprene (CR) during vulcanization, thereby improving the properties of the vulcanizate, such as mechanical properties or reversion stability.

[0004] The use of ethylenethiourea (ETU) as a crosslinker has been a long-standing practice, however, in some applications ethylenethiourea is classified as a toxicologically problematic substance by the European Chemicals Agency (ECHA).

[0005] As an alternative to ethylenethiourea (ETU), 3-methylthiazolidine-2-thione (MTT) has also been used as a crosslinking agent. Its drawbacks are a deterioration in mechanical properties compared to ETU and, for some types of chloroprene, a shorter Mooney scorch time. This drawback compared to ETU becomes more pronounced when the vulcanization temperature is increased above 180-200°C.

[0006] Patent Document 1 discloses a substantially guanidine-free rubber mixture in which the rapidly crosslinking but toxicologically problematic secondary accelerator guanidine is replaced with polyethyleneimine, which is used in combination with sulfur, sulfenamide, and mercaptobenzothiazole, particularly in natural rubber.

[0007] The crosslinking of rubber with a sulfur vulcanization accelerator system generally offers the following advantages: by using various vulcanization accelerators and their combinations, it is possible to vary the processability and product properties over a wide range, for example, by adjusting the induction period (scorch time, which should ideally not be too short) and the reaction rate (which is preferably high and leads to a short complete vulcanization time). To adjust the induction and vulcanization times, so-called secondary accelerators can be added to the rubber mixture. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2016 / 030469 Brochure Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention was to provide a rubber mixture based on polychloroprene (CR) and a toxicologically friendly crosslinking agent. [Means for solving the problem]

[0010] It has now been found that rubber mixtures based on polychloroprene (CR) and polyethyleneimine as crosslinker overcome the above-mentioned drawbacks.

[0011] The rubber mixtures according to the invention also surprisingly exhibit improved physical stability in relation to changes in vulcanization temperature. In addition, the vulcanizates produced from the rubber mixtures according to the invention are characterized by improved aging stability in relation to the influence of oxidizing substances such as ozone or oxygen.

[0012] The present invention therefore relates to a rubber mixture comprising at least one polychloroprene rubber (CR) and at least one polyethyleneimine. DETAILED DESCRIPTION OF THE INVENTION

[0013] The unit "phr" below refers to parts by weight based on 100 parts by weight of the total amount of polychloroprene rubber present in the rubber mixture.

[0014] The rubber mixtures according to the invention generally contain polyethyleneimine in an amount of 0.01 to 20 phr, preferably 0.05 to 15 phr, particularly preferably 0.5 to 10 phr, very particularly preferably 1 to 8 phr, in particular 2 to 6 phr.

[0015] The rubber mixture according to the present invention contains at least one polychloroprene rubber (CR).

[0016] Polychloroprene rubber (CR) and its preparation have been known for a long time: it is a polymer based on 2-chloro-1,3-butadiene (chloroprene) and can be obtained by emulsion polymerization.

[0017] The rubber mixtures according to the invention include in principle all polychloroprene rubbers which are commonly used.

[0018] The various types of polychloroprene rubber available commercially vary in their structure and properties. The so-called general-purpose types are distinguished by the modifier used during polymerization: mercaptan-modified and xanthate-modified. These two types exist in uncrosslinked and precrosslinked forms. Sulfur-modified CR types are also available. Additionally, the various types of polychloroprene are characterized, in particular, by their Mooney viscosity (ML(1+4), 100°C) and their crystallization rate.

[0019] The rubber mixture according to the invention preferably comprises at least one polychloroprene rubber from the group of mercaptan- or xanthate-modified polychloroprene rubbers.

[0020] Mercaptan- and xanthate-modified polychloroprene rubbers are available as commercial products, for example under the trade name Baypren® (a commercial product of Arlanxeo).

[0021] Mercaptan-modified polychloroprene rubber is typically produced by emulsion polymerization of chloroprene in the presence of n-dodecyl mercaptan. Xanthate-modified polychloroprene rubber is typically produced by emulsion polymerization of chloroprene in the presence of xanthogen disulfide.

[0022] The rubber mixture of the present invention preferably comprises at least one mercaptan-modified polychloroprene rubber having a Mooney viscosity (ML(1+4), 100°C) between 35 and 50 MU ("Mooney units") and a crystallization rate ranging from very slow to intermediate, and / or at least one mercaptan-modified polychloroprene rubber having a Mooney viscosity between 90 and 120 MU and an intermediate crystallization rate.

[0023] Mercaptan-modified polychloroprene rubbers which are preferred in the present invention and which have a Mooney viscosity (ML(1+4), 100°C) of between 35 and 50 MU and a crystallization rate ranging from very slow to medium are available, for example, as commercial products from Arlanxeo under the names Baypren® 110, Baypren® 112, Baypren® 210, and Baypren® 211. Mercaptan-modified polychloroprene rubbers which are also preferred in the present invention and which have a Mooney viscosity of between 90 and 120 MU and a medium crystallization rate are available, for example, as commercial products from Arlanxeo under the name Baypren® 230.

[0024] The rubber mixture of the present invention has a molar mass distribution (Mw / Mn) in the range of 2 to 3, 4 × 10 5 ~1.3×10 6 Preferably, the composition comprises at least one mercaptan-modified polychloroprene rubber having an average molar mass (Mw) between 100 and 200 g / mol and a Mooney viscosity between 35 and 120 MU.

[0025] The polychloroprene present in the rubber mixtures of the present invention may have a 1,4-trans content of varying magnitude, preferably between 88% and 94%.

[0026] The rubber mixtures of the present invention contain at least one polyethyleneimine. The polyethyleneimine (PEI) present in the rubber mixtures of the present invention is preferably a homopolymer of ethyleneimine / a copolymer of ethyleneimine and one or more comonomers, in which the proportion of repeat units derived from ethyleneimine in the copolymer is at least 50% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, particularly preferably at least 95% by weight, and very particularly preferably at least 98% by weight, in each case based on the total mass of the polymer. The term "polyethyleneimine" also encompasses mixtures of homopolymers and / or copolymers of ethyleneimine, for example, with different molecular weights, degrees of branching, comonomers, etc.

[0027] Such homopolymers or copolymers typically have a weight-average molecular weight of more than 200, preferably 300 to 3,000,000, particularly preferably 400 to 800,000, very particularly preferably 500 to 100,000, more preferably 600 to 30,000 and most preferably 700 to 7000.

[0028] The polyethyleneimine present in the rubber mixtures of the present invention may have a linear or branched structure, and it is also possible to employ mixtures of linear and branched polyethyleneimine.

[0029] In one preferred embodiment, polyethyleneimine having a branched structure containing not only primary but also secondary and tertiary amino groups is employed.

[0030] It is preferred if the rubber mixture according to the invention comprises ethylenediamine-ethyleneimine copolymer / polyethyleneimine homopolymer, such as those conforming to CAS numbers 25987-06-8 and 9002-98-6.

[0031] The rubber mixtures according to the invention may contain one or more fillers.

[0032] Suitable fillers include in principle all fillers known for this purpose from the prior art, although active or reinforcing fillers are preferred.

[0033] The rubber mixtures according to the invention generally contain from 0.1 to 250 phr, preferably from 20 to 200 phr, particularly preferably from 25 to 160 phr, of at least one filler.

[0034] The rubber mixtures according to the invention preferably contain at least one oxidic filler containing hydroxyl groups and / or at least one carbon black.

[0035] The content of hydroxyl-containing oxidic fillers in the rubber mixtures according to the invention is generally 0.1 to 250 phr, preferably 1 to 200 phr, particularly preferably 5 to 180 phr, very particularly preferably 10 to 160 phr.

[0036] Suitable hydroxyl-containing oxide-based fillers preferably include those from the following group: - silica, in particular precipitated or pyrogenic silica, having a content of 5 to 1000 m 2 / g, preferably 20 to 400m 2 / g specific surface area (BET surface area) and a primary particle size of 10 to 400 nm, where the silica is optionally in the form of a mixed oxide with other metal oxides, for example oxides of Al, Mg, Ca, Ba, Zn, Zr, Ti; - Synthetic silicates, such as aluminum silicate, alkaline earth metal silicates, such as magnesium silicate or calcium silicate, from 20 to 400 m 2 / g BET surface area and a primary particle size of 10-400 nm; - Natural silicates, such as kaolin and other naturally occurring silicas, and mixtures thereof.

[0037] The hydroxyl-containing oxidic fillers from the group of silicas present in the rubber mixtures according to the invention are preferably those which can be prepared, for example, by precipitation from solutions of silicates or by flame hydrolysis of silicon halides.

[0038] The rubber mixture of the present invention comprises at least one rubber having a viscosity of 20 to 400 m 2 / g in an amount of 0.1 to 200 phr, preferably 5 to 200 phr, particularly preferably 10 to 100 phr, very particularly preferably 20 to 80 phr.

[0039] All BET values ​​relate to the specific surface area measured in accordance with DIN 66131. ​​The stated primary particle sizes refer to values ​​determined by scanning electron microscopy.

[0040] The rubber mixtures of the present invention may further comprise at least one carbon black as filler.

[0041] In the present invention, preferred is a black powder that can be obtained by the lamp black, furnace black or gas black method and has a particle size of 20 to 200 m. 2 The carbon black has a specific surface area (BET) in the range of 20 to 200 m / g, for example, SAF, ISAF, IISAF, HAF, FEF, or GPF carbon black. 2 Preferably, the composition contains at least one carbon black having a specific surface area (BET) in the range of / g.

[0042] The rubber mixtures according to the invention generally contain from 0.1 to 200 phr, preferably from 5 to 150 phr, particularly preferably from 20 to 120 phr, of at least one carbon black.

[0043] If the rubber mixture according to the invention contains carbon black and silica-based fillers as fillers, the total amount of these two types of fillers is preferably 10 to 200 phr, particularly preferably 15 to 160 phr.

[0044] In addition to the above-mentioned fillers, the rubber mixture according to the invention may contain at least one further filler, such as short fibers made from aramid, cellulose or nanocellulose, and lignin-based fillers.

[0045] The total proportion of these above-mentioned further fillers in the rubber mixture according to the invention is typically 0.1 to 160 phr, preferably 0.5 to 100 phr, particularly preferably 1 to 50 phr.

[0046] The rubber mixtures of the present invention may contain one or more reinforcing additives.

[0047] The rubber mixtures according to the invention preferably comprise at least one reinforcing additive from the group of sulfur-containing organosilanes, in particular sulfur-containing silanes containing alkoxysilyl groups, very particularly preferably sulfur-containing organosilanes containing trialkoxysilyl groups.

[0048] It is particularly preferred that the rubber mixture according to the invention comprises one or more sulfur-containing silanes from the group bis(triethoxysilylpropyl)tetrasulfane, bis(triethoxysilylpropyl)disulfane and 3-(triethoxysilyl)-1-propanethiol.

[0049] The rubber mixtures according to the invention generally contain from 1 to 20 parts by weight, preferably from 2 to 15 parts by weight, particularly preferably from 2 to 10 parts by weight, of at least one reinforcing additive, in each case calculated as 100% active ingredients and based on 100 parts by weight of all fillers present in the rubber mixture.

[0050] To improve metering and / or dispersibility, the liquid sulfur-containing silane may be absorbed onto a carrier (dry liquid), the content of the sulfur-containing silane in these dry liquids being preferably between 30 and 70 parts by weight, more preferably between 40 and 60 parts by weight, per 100 parts by weight of the dry liquid.

[0051] In one preferred embodiment, the rubber mixture according to the invention comprises 5 to 200 phr, particularly preferably 10 to 100 phr and very particularly preferably 20 to 80 phr of at least one oxidic filler containing hydroxyl groups from the group of silicas, and 1.0 to 20 phr, preferably 5 to 15 phr and very particularly preferably 2 to 10 phr of at least one reinforcing additive from the group of sulfur-containing organosilanes, particularly preferably sulfur-containing organosilanes containing alkoxysilyl groups, very particularly preferably sulfur-containing organosilanes containing trialkoxysilyl groups.

[0052] The rubber mixture according to the invention may contain one or more crosslinking agents.

[0053] In the vulcanization of polychloroprene rubber, metal oxides are particularly employed to promote crosslinking and neutralize the hydrogen chloride produced during the crosslinking reaction. Suitable metal oxides include, in principle, magnesium oxide, zinc oxide, lead oxide, and mixtures thereof.

[0054] The rubber mixtures according to the invention preferably contain at least one crosslinking agent from the group of the metal oxides, in particular magnesium oxide and / or zinc oxide.

[0055] The rubber mixture of the present invention generally contains 0.1 to 10 phr, preferably 0.1 to 8 phr, particularly preferably 0.1 to 5 phr, of at least one metal oxide.

[0056] The rubber mixture of the present invention may contain one or more vulcanization accelerators or vulcanization retarders.

[0057] They are vulcanization accelerators or vulcanization retarders from the group of the mercaptobenzothiazoles, mercaptobenzimidazoles, thiazolesulfenamides, thiurams, thiocarbamates, tolyltriazoles, xanthates, and thiophosphates.

[0058] The rubber mixture of the present invention generally contains 0 to 10 phr, preferably 0 to 8 phr, particularly preferably 0 to 5 phr, of at least one vulcanization accelerator or vulcanization retarder.

[0059] The rubber mixture of the present invention may further comprise one or more rubber auxiliaries.

[0060] Suitable rubber auxiliaries include, for example, adhesive systems, anti-aging agents, heat stabilizers, light resistance agents, antioxidants, especially antiozonants, flame retardants, processing aids, impact strength improvers, vulcanizing oils, plasticizers, tackifiers, blowing agents, dyes, pigments, waxes, extenders, organic acids, vulcanization retarders, activators, and anti-reversion agents.

[0061] These rubber auxiliaries may be added to the rubber mixtures of the present invention in amounts conventionally used for such auxiliaries and dictated by the end use of the vulcanizates produced therefrom, typically in amounts of 0.1 to 30 phr.

[0062] Antioxidants of particular interest include alkylated phenols, styrenated phenols, sterically hindered phenols such as 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol (BHT), 2,6-di-tert-butyl-4-ethylphenol, sterically hindered phenols containing ester groups, sterically hindered phenols containing thioethers, 2,2'-methylenebis(4-methyl-6-tert-butylphenol) (BPH), and even sterically hindered thiobisphenols.

[0063] If discoloration of the rubber is not a major concern, it is also possible to use amine-based ageing stabilizers such as, for example, mixtures of diaryl-p-phenylenediamines (DTPD), octylated diphenylamine (ODPA), phenyl-α-naphthylamine (PAN), phenyl-β-naphthylamine (PBN), preferably those based on phenylenediamines, such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (6PPD), N-1,4-dimethylpentyl-N'-phenyl-p-phenylenediamine (7PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD).

[0064] Further antioxidants include phosphites such as tris(nonylphenyl)phosphite, polymerized 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ), 2-mercaptobenzimidazole (MBI), methyl-2-mercaptobenzimidazole (MMBI), zinc methylmercaptobenzimidazole (ZMMBI), which are most often used in combination with the above-mentioned phenolic antioxidants.

[0065] Ozone resistance can be improved by antioxidants such as N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (6PPD), N-1,4-dimethylpentyl-N'-phenyl-p-phenylenediamine (7PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), enol ethers, or cyclic acetals.

[0066] The processing aid should be active between the rubber particles and be able to withstand frictional forces during mixing, plasticization and molding. Processing aids that may be present in the rubber mixtures of the present invention include all lubricants commonly used in plastics processing, such as hydrocarbons such as oils, paraffins and PE waxes, aliphatic alcohols having 6 to 20 carbon atoms, ketones, carboxylic acids such as fatty acids and montanic acid, oxidized PE waxes, metal salts of carboxylic acids, carboxamides, and carboxylic acid esters from alcohols such as ethanol, aliphatic alcohols, glycerol, ethanediol, pentaerythritol and long-chain carboxylic acids as acid components.

[0067] In order to suppress flammability and smoke generation during combustion, the rubber mixture composition of the present invention may contain flame retardants. Examples of compounds used for this purpose include antimony trioxide, phosphate esters, chloroparaffins, aluminum hydroxide, boron compounds, zinc compounds, molybdenum trioxide, ferrocene, calcium carbonate, and magnesium carbonate.

[0068] Before crosslinking, further thermoplastic resins may be added to the rubber mixtures according to the invention, which function, for example, as polymeric processing aids or impact modifiers. These thermoplastic resins are preferably selected from the group consisting of homopolymers and copolymers based on ethylene, propylene, butadiene, styrene, vinyl acetate, vinyl chloride, glycidyl acrylate, glycidyl methacrylate, acrylate and methacrylate homopolymers with alcohol components of branched or unbranched C1-C10 alcohols, particularly preferred polyacrylates with identical or different alcohol groups from the group of C4-C8 alcohols, in particular butanol, hexanol, octanol and 2-ethylhexanol, polymethyl methacrylate, methyl methacrylate-butyl acrylate copolymer, methyl methacrylate-butyl methacrylate copolymer, ethylene-vinyl acetate copolymer, chlorinated polyethylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer.

[0069] Known adhesive systems are the so-called RFS direct adhesive systems, which are based on resorcinol, formaldehyde, and silica. These direct adhesive systems can be used in any desired amount for the rubber mixtures of the present invention at any time during their incorporation into the rubber mixtures of the present invention.

[0070] Suitable formaldehyde donors include not only hexamethylenetetramine but also methylolamine derivatives. Potential improvements in adhesion can be achieved by adding components capable of forming synthetic resins, such as phenols and / or amines and aldehydes, or aldehyde-eliminating compounds, to known rubber mixtures. Compounds widely used as resin-forming components in rubber adhesive mixtures include resorcinol and hexamethylenetetramine (HEXA) (GB 801 928, FR 1 021 959), sometimes in combination with silica fillers (DE 1 078 320).

[0071] Preferred rubber mixtures according to the invention include: - Molar mass distribution Mw / Mn in the range of 2-3, 4 x 10 5 ~1.3×10 6 at least one polychloroprene rubber having an average molar mass (Mw) between 35 and 120 g / mol and a Mooney viscosity between 35 and 120 MU, - 0.05 to 15 phr of at least one polyethyleneimine, - 5 to 200 phr of at least one silica, in particular 5 to 1000 m 2 / g, preferably 20 to 400m 2 / g specific surface area (BET) and a primary particle size of 100 to 400 nm, and / or - 5 to 150 phr of at least one carbon black, in particular 20 to 200 m 2 / g range of specific surface area (BET).

[0072] Particularly preferred are rubber mixtures according to the invention which comprise: - Molar mass distribution Mw / Mn in the range of 2-3, 4 x 10 5 ~1.3×10 6 at least one chloroprene rubber having an average molar mass (Mw) between 35 and 120 g / mol and a Mooney viscosity between 35 and 120 MU, - 0.5 to 10 phr of at least one polyethyleneimine, - 10 to 100 phr of at least one silica, in particular 5 to 1000 m 2 / g, preferably 20 to 400m 2 / g specific surface area (BET) and a primary particle size of 100 to 400 nm, and / or - 20 to 120 phr of at least one carbon black, in particular 20 to 200 m 2 / g, - 0.1 to 5 phr of at least one crosslinking agent, in particular from the group of metal oxides, - 2 to 10 parts by weight (based on 100 parts by weight of all fillers present in the rubber mixture) of at least one reinforcing additive, in particular from the group of sulfur-containing silanes.

[0073] The present invention further provides a process for producing the rubber mixture of the present invention, which comprises intermixing at least one polychloroprene rubber and at least one polyethyleneimine, optionally in the presence of at least one filler, optionally at least one crosslinking agent, optionally at least one vulcanization accelerator or vulcanization retarder, optionally at least one reinforcing additive, and optionally one or more of the above-mentioned rubber auxiliaries, in the usual or preferred amounts for these additives, at a temperature in the range of 40°C to 200°C, particularly preferably 70°C to 130°C.

[0074] The rubber mixture of the present invention can be produced by mixing in a known mixing device, such as a roller, an internal mixer, a downstream roller mill, or a mixing extruder, for a period of 1 to 1000 seconds. -1 , preferably 1 to 100 seconds -1 The process is carried out in the usual manner at a shear rate of 100 rpm.

[0075] It is preferred to add the polyethyleneimine near the end of the mixing process at a lower temperature in the range of 40°C to 100°C, typically along with a vulcanization accelerator or retarder.

[0076] The present invention further relates to a process for producing a rubber vulcanizate by heating the rubber mixture according to the present invention at a melt temperature of 150°C to 280°C, preferably 170°C to 240°C.

[0077] The process for producing the rubber vulcanizates according to the present invention can be carried out over a wide range of pressures, preferably in the range of from 1 to 200 bar.

[0078] The present invention further provides a rubber vulcanizate obtainable by vulcanizing the rubber mixture according to the present invention.

[0079] The vulcanization of the rubber mixtures according to the invention can be carried out by the injection molding method or by the salt bath vulcanization method using a press.

[0080] Heating of the rubber mixture to produce the vulcanizates of the present invention is typically carried out by means of microwaves, by heated air, by heated steam, in a salt bath or in an autoclave.

[0081] The present invention further provides a rubber vulcanizate obtainable by vulcanizing the rubber mixture according to the present invention.

[0082] The vulcanizates of the present invention are suitable for producing a wide variety of rubber products, in particular industrial rubber articles such as hoses, molded articles, cables and conduits, belts, profiles, conveyor belts, vibration damping elements, coatings for rollers, and rubber-coated fabrics.

[0083] The rubber mixtures of the present invention can also be used to produce foams. This involves adding a chemical or physical blowing agent to the rubber mixtures of the present invention. Possible chemical blowing agents include all substances known for this purpose, such as azodicarbonamide, p-toluenesulfonylhydrazide, 4,4'-oxybis(benzenesulfohydrazide), p-toluenesulfonylsemicarbazide, 5-phenyltetrazole, and mixtures containing these substances. Examples of suitable physical blowing agents include carbon dioxide and halogenated hydrocarbons.

[0084] The present invention further provides molded articles, in particular industrial rubber articles such as hoses, cables, conduits, belts, profiles, conveyor belts, vibration damping elements, coatings for rollers and rubber coated fabrics, and also foams comprising the rubber vulcanizates of the present invention.

[0085] The following examples are used to illustrate the invention without, however, limiting it. [Example]

[0086] [Table 1]

[0087] Production of rubber vulcanizates according to the present invention Vulcanizates were prepared from the rubber compound of Example 1 and the rubber compounds of Reference Examples Comparative Examples 1 to 3 shown in Table 1. This involved mixing the ingredients set forth for Example 1 and Reference Examples in Table 1 in the amounts set forth therein (all in parts per 100 parts of rubber (phr)), in each case using the mixing process described below.

[0088] Polyethyleneimine (RHENOCURE® DR / S) in Example 1 was replaced with ethylenethiourea (ETU) (RHENOCURE® NPV / C) in Reference Example Comparative Example 2 and with 3-methylthiazolidine-2-thione (MTT) (RHENOCURE® CRV / LG) in Reference Example Comparative Example 3. Reference Example Comparative Example 1 was run without the addition of a crosslinker.

[0089] In each case, in the first mixing step, the polychloroprene rubber BAYPREN® 211 was first charged into a kneader (GK 1.5), and the additives REGAL® SRF / N772, PALMERA® A9818, and VULKANOX® 4020 / LG were added at a temperature of about 40° C. and about 40 revolutions per second. The mixture was mixed for about 3 minutes at a temperature of 100° C.

[0090] Then, in a second mixing step, the rubber mixture was added to a temperature-controlled roller and the following additives were added and incorporated into the rubber mixture: ROTSIEGEL zinc oxide, RHENOFIT® D / A, and RHENOCURE® DR / S in Example 1, RHENOCURE® NPV / C in Comparative Example 2, and RHENOCURE® CRV in Comparative Example 3. The temperature of the roller was between 30°C and 50°C.

[0091] The rubber mixtures so obtained were then fully vulcanized at 180°C and 200°C, respectively, and rolled into test plaques.

[0092] These test plaques were then used in the performance tests described below.

[0093] [Table 2]

[0094] Technical Testing The rubber mixtures and vulcanizates produced were subjected to the technical tests described below, the values ​​thus obtained being shown in Tables 2 to 4.

[0095] Measurement of rubber mixture / vulcanizate properties Measurement of Mooney Viscosity: The measurement was carried out by means of a shear disc viscometer in accordance with ASTM D1646. Viscosity can be determined directly from the force with which rubber (and rubber mixtures) resist processing. In a Mooney shear disc viscometer, a pleated disc, surrounded by the test material on both sides, is rotated in a heatable chamber at a speed of approximately 2 revolutions per minute. The force required to do so is measured as torque, which corresponds to the respective viscosity. The specimen is generally preheated to 100°C for 1 minute and then measured over 4 minutes, while the temperature is kept constant. The viscosity is reported together with the respective test conditions: e.g., ML(1+4)100°C (Mooney viscosity, rotor size L, preheating and test time (min), test temperature).

[0096] Rheometer (Vulcameter): MDR (Moving Die Rheometer) cure profiles and accompanying analytical data are measured on an MDR 2000 Monsanto rheometer according to ASTM D5289-95. The full cure time is measured when 95% of the rubber is crosslinked. The mixtures were heated at 180°C until 95% conversion was achieved. At 200°C, the cure time was 20 minutes.

[0097] Elongation at break, tensile strength, 50, 100 and 300 modulus: These measurements were carried out in accordance with DIN 53504 (tensile test, rod S2, 5 measurements).

[0098] hardness: Determination of Shore hardness (Shore A) according to DIN 53505 at 23°C (measured three times).

[0099] Resilience: Rebound resilience measured in accordance with DIN 53512 at 23°C (measured three times).

[0100] Compression set (CS): Compression set determined after 72 hours at 100° C. Measurement carried out in accordance with DIN ISO 815.

[0101] [Table 3]

[0102] [Table 4]

[0103] [Table 5]

[0104] Vulcanizates were prepared from the reference examples Comparative Example 1, Comparative Example 2 and Comparative Example 3 and from Inventive Example 1 (vulcanization temperatures of 180° C. and 200° C. in each case).

[0105] Comparing the values ​​obtained for Inventive Example 1 with those for Reference Examples Comparative Examples 1, 2, and 3, it can be seen that although the crosslinking rate (using 90% conversion time as a guide) is slower with PEI than with ETU or MTT (Examples 2 and 3, Table 2) at both 180° C. and 200° C., ultimately comparable delta-torque values ​​(ΔS′) are obtained, thus indicating comparable crosslinking levels. In contrast, Reference Example Comparative Example 1, which does not contain any added crosslinking agent, exhibits a significantly lower ΔS′ value, thus indicating a lower crosslink density in the vulcanizate.

[0106] Tensile tests were performed on all vulcanizates. Again, similar values ​​at 200 and 300 modulus indicate similar crosslink densities for Reference Examples Comparative Examples 2 and 3 and Inventive Example 1. Again, Reference Example Comparative Example 1 exhibits a significantly lower degree of crosslinking than Comparative Examples 2 and 3 and Example 1.

[0107] The elongation at break and tensile strength of Example 1 show better values ​​than those of Comparative Examples 2 and 3. As expected, the values ​​of Comparative Example 1 are at a significantly higher level due to the low degree of crosslinking.

[0108] With respect to the compression set value (72 hours, 100°C) when heated at 200°C, Example 1 is better than Comparative Examples 1 and 3, but is slightly inferior to Comparative Example 2.

[0109] The significant advantage of Example 1 over the comparative examples is also evident from its stability against heating temperature, as can be seen from the rate of change in physical properties shown in Table 2. In this case, Example 1 shows significantly lower changes than Comparative Examples 1 to 3.

[0110] [Table 6]

[0111] [Table 7]

[0112] As expected, the rubber vulcanizates solidify when stored in air at 100°C for 7 days. The vulcanizate of Example 1 shows particularly high stability to aging compared to the three comparative examples, as evidenced by the relatively small changes in physical properties, especially in modulus values, at a vulcanization temperature of 200°C (see Table 5).

Claims

1. A rubber mixture comprising at least one polychloroprene rubber (CR) and at least one polyethyleneimine in an amount of 2 to 6 phr, and at least one crosslinking agent selected from the group of metal oxides.

2. The polychloroprene rubber has a molar mass distribution Mw / Mn in the range of 2 to 3 and a molar mass distribution Mw / Mn of 4×10 ５ ~1.3 × 10 ６ 2. The rubber mixture according to claim 1, characterized in that it has an average molar mass (Mw) of between 100 and 150 g / mol.

3. 2. Rubber mixture according to claim 1, characterized in that it contains at least one oxidic filler containing hydroxyl groups in an amount of 0.1 to 250 phr.

4. 2. Rubber mixture according to claim 1, characterized in that it contains at least one carbon black in an amount of from 0.1 to 200 phr.

5. 2. Rubber mixture according to claim 1, characterized in that it contains at least one reinforcing additive from the group of sulfur-containing organosilanes.

6. 2. The rubber mixture of claim 1, further comprising at least one vulcanization accelerator from the group consisting of mercaptobenzothiazoles, mercaptobenzimidazoles, thiazolesulfenamides, thiurams, thiocarbamates, tolyltriazoles, xanthates, and thiophosphates.

7. 2. The rubber mixture according to claim 1, characterized in that it contains at least one rubber auxiliary from the group of adhesive systems, anti-aging agents, heat stabilizers, light stabilizers and antioxidants.

8. 10. A process for producing the rubber mixture of claim 1, characterized in that it comprises intermixing at least one polychloroprene rubber and at least one polyethyleneimine in the presence of optionally at least one filler, optionally at least one crosslinking agent, optionally at least one vulcanization accelerator or retarder, optionally at least one reinforcing additive, and optionally one or more rubber auxiliaries at a temperature in the range of 40°C to 200°C.

9. 10. A rubber vulcanizate obtainable by vulcanizing the rubber mixture of claim 1.

10. A process for producing a rubber vulcanizate, characterized in that at least one rubber mixture according to claim 1 is heated to a temperature ranging from 150°C to 240°C.

11. A molded article comprising the rubber vulcanizate of claim 9.

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