Rubber mixtures with improved properties

Abstract

To provide an improved rubber mixture obtained by a simple method and exhibiting improved characteristics, to provide a method for producing a rubber product, and to provide the rubber product.SOLUTION: A rubber mixture comprising a rubber and a liquid polybutadiene, wherein the polybutadiene is liquid at a temperature of 20 °C. and a pressure of 98.06655 kPa, and wherein the liquid polybutadiene comprises only C and H atoms and has an average molecular weight (Mw) of from 1500 to 5000g / mol as measured by gel permeation chromatography, a method for producing a rubber product by vulcanization using the rubber mixture according to the present invention as a starting material, and a rubber product obtained by this method are provided.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention provides a rubber mixture comprising rubber and liquid polybutadiene, Polybutadiene is liquid at a temperature of 20°C and a pressure of 98.0665 kPa. the liquid polybutadiene containing only C and H atoms and having an average molecular weight (Mw) of 1500 to 5000 g / mol as measured by gel permeation chromatography as described in the specification; a method for producing rubber products by vulcanization using the rubber mixture according to the invention as a raw material, - a rubber product obtained by this method, Regarding. [Background technology]

[0002] So-called "green tires" are a trend in the automotive industry. Their main objective is to reduce rolling resistance, improve fuel economy, and improve wet grip while maintaining constant wear resistance. The addition of precipitated silica to the formulation can achieve this goal, but the silica used has poor compatibility with the rubber matrix. This challenge is currently being overcome by adding silanes as compatibilizers. Due to the covalent bond between the filler and the polymer, the wear levels of silica-filled tires are comparable to those of carbon black-filled tires.

[0003] Patent Document 1 discloses a rubber composition for tire treads that is composed of at least either natural rubber or synthetic rubber and a filler component consisting of only silica or only silica and carbon black, and the silica is composed of at least amorphous spherical silicon dioxide fine particles having an average particle size of 0.05 to 1.00 μm.

[0004] Patent Documents 2, 3 and 4 describe the functionalization of anionically polymerized polybutadiene. Patent Document 5 describes the functionalization of polybutadiene with a vinyl content of less than 2%.

[0005] Patent document 6 proposes rubber mixtures in which diene rubber is reacted with acrylamide and / or silane- or tin-modified acrylamide.The production of the systems described in the prior art is very complicated.

[0006] Patent Document 7 describes a rubber composition containing a modified liquid polybutadiene containing functional groups (eg, hydroxyl groups) with a vinyl content of less than 70% and an Mw of 1000 to 15000 g / mol.

[0007] Patent Document 8 describes a rubber composition containing a modified liquid diene-based rubber containing a functional group derived from a silane compound, with a vinyl content of less than 70% and an Mw of 15,000 to 120,000 g / mol.

[0008] Patent Document 9 describes a rubber composition for high-durability tires containing a modified liquid diene rubber containing a functional group derived from a silane compound, with a vinyl content of 30% or more and less than 70% and an Mw of 1,000 to 120,000 g / mol.

[0009] Patent Document 10 describes rubber compositions for tires and pneumatic tires containing liquid polybutadiene having a vinyl content of more than 80% and an Mw of 1000 to 18000 g / mol, most preferably 1000 to 5000 g / mol.

[0010] Patent Document 11 describes a rubber composition containing a modified liquid polybutadiene rubber containing organosilicon end groups with a vinyl content of less than 70% and an Mw of 500 to 12,000 g / mol, and a plasticizer.

[0011] US Pat. No. 5,629,999 describes a rubber composition for tire treads containing liquid polybutadiene having a vinyl content of about 85% and a Mw of 4700 g / mol.

[0012] Patent Document 13 describes a rubber composition containing a liquid polybutadiene having a vinyl content of less than 50% and an Mw of 2000 to 10000 g / mol. The composition further contains an ester plasticizer.

[0013] Patent Document 14 describes a rubber composition containing a modified liquid diene-based rubber containing a functional group derived from a silane compound, with a vinyl content of less than 70% and an Mw of 15,000 to 120,000 g / mol.

[0014] Patent Document 15 describes a rubber composition containing a modified liquid diene-based rubber containing a functional group derived from a carboxyl group-containing nitrone compound.

[0015] Many rubber compounds used in the rubber and tire industry contain plasticizers to facilitate processing and to tailor the mechanical and dynamic mechanical properties to the needs of the application.

[0016] A significant drawback of using plasticizers is that they tend to migrate out of (vulcanized) rubber products over time, and therefore the properties of the rubber products also change over time.

[0017] Externally perceptible signs of this effect are, for example, increased vulcanizate hardness and / or embrittlement accompanied by a decrease in elasticity.

[0018] Many plasticizer oils contain large amounts of aromatic compounds, and today there is a strong demand for the reduction or elimination of such materials in rubber applications for environmental and health reasons.

[0019] To solve these problems and challenges, reactive plasticizers are often used. One type of reactive plasticizer is liquid polybutadiene (see, for example, Patent Document 16). Reactive plasticizers improve the processing of rubber mixtures and have the additional advantage that they react with other parts of the rubber mixture, thereby essentially not migrating from the vulcanized rubber product.

[0020] However, the use of reactive plasticizers leads to a decrease in the rolling resistance of tires and higher fuel consumption when the tires have treads based on rubber mixtures containing these reactive plasticizers. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-031244 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-083649 [Patent Document 3] US Patent Application Publication No. 2014 / 0121316 [Patent Document 4] European Patent Application Publication No. 2266819 [Patent Document 5] European Patent Application Publication No. 1479698 [Patent Document 6] European Patent Application Publication No. 2818505 [Patent Document 7] WO 2019 / 044888 (European Patent Application Publication No. 3677637) [Patent Document 8] WO 2019 / 044889 (European Patent Application Publication No. 3677635) [Patent Document 9] WO 2019 / 044893 (European Patent Application Publication No. 3677638) [Patent Document 10] Japanese Patent Application Publication No. 2019-094463 [Patent Document 11] German Patent Application Publication No. 102015210424 [Patent Document 12] European Patent Application Publication No. 1035164 [Patent Document 13] Japanese Patent Application Laid-Open No. 2009-203288 [Patent Document 14] International Publication No. 2019 / 044891 (U.S. Patent Application Publication No. 2020 / 207957) [Patent Document 15] US Patent Application Publication No. 2018 / 072874 [Patent Document 16] U.S. Patent No. 7,411,018 Summary of the Invention [Problem to be solved by the invention]

[0022] There is therefore a need for improved rubber mixtures which are obtainable in a simple manner and which exhibit improved properties. [Means for solving the problem]

[0023] In comparing the use of various liquid polybutadienes, the inventors have surprisingly found that liquid polybutadienes containing a high amount of 1,2-vinyl groups improve not only the processing of these rubber mixtures but also the rolling resistance of tires (treads) made therewith.

[0024] The present invention therefore relates to a rubber mixture comprising a rubber and a liquid polybutadiene, the polybutadiene being liquid at a temperature of 20°C and a pressure of 98.0665 kPa, the liquid polybutadiene containing only C and H atoms and having an average molecular weight (Mw) of 1500 to 5000 g / mol as measured by gel permeation chromatography as described herein, the rubber mixture having a high amount of 1,2-vinyl groups as claimed in the claims.

[0025] The present invention also relates to a process for producing rubber products by vulcanization, using the rubber mixture according to the invention as a raw material.

[0026] The invention further relates to rubber products obtainable by the process according to the invention.

[0027] The rubber mixtures according to the invention have very good processing properties which are shown by very good dynamic mechanical properties.

[0028] The rubber products obtained by vulcanization using the rubber mixture according to the invention as raw material have the advantage of exhibiting high tensile strength values ​​and high elongation at break values.

[0029] The tires or tire treads obtained by processing and vulcanizing the rubber mixtures according to the invention have the advantage of exhibiting good rolling resistance, low wear and good driving characteristics in winter / on snow. The low rolling resistance has the advantage that the use of such tires helps to reduce the fuel consumption of vehicles.

[0030] The mixtures, methods and products / uses according to the invention are described below by way of example, without intending that the invention be limited to these exemplary embodiments. Where ranges, general formulas or groups of compounds are specified below, these are intended to be included within the corresponding ranges explicitly mentioned. It is intended to encompass not only ranges or compound groups, but also subranges and subcompound groups that can be obtained by excluding individual values ​​(ranges) or compounds. Where documents are cited in the context of this specification, their contents are fully incorporated into the disclosure of the present invention with respect to the matters specifically mentioned. The percentages specified below are % by weight unless otherwise specified. Where average values ​​are reported below, these are numerical averages unless otherwise specified. Where material properties, such as viscosity, are mentioned below, these are material properties at 25°C unless otherwise specified. Where chemical (empirical) formulas are used in this invention, the specified indices may be average values ​​as well as absolute numbers.

[0031] The present invention is a rubber mixture comprising a rubber and a liquid polybutadiene, Polybutadiene is liquid at a temperature of 20°C and a pressure of 98.0665 kPa. Liquid polybutadiene is made from 1,3-butadiene-derived monomer units:

[0032] [ka]

[0033] Including, the proportion of A in all 1,3-butadiene-derived monomer units present in the liquid polybutadiene is 55 to 70 mol %; the total proportion of B and C in all 1,3-butadiene-derived monomer units present in the liquid polybutadiene is 30 to 45 mol %, Liquid polybutadiene relates to rubber mixtures containing only C and H atoms and having an average molecular weight (Mw) of 1500 to 5000 g / mol, as determined by gel permeation chromatography as described herein.

[0034] Liquid polybutadienes contain only C and H atoms. Therefore, preferred liquid polybutadienes are non-functionalized polybutadienes. The liquid polybutadienes preferably have an average molecular weight (Mw) of 1750 to 3500 g / mol, as measured by gel permeation chromatography (as described below in the Examples section).

[0035] The liquid polybutadiene preferably has a viscosity at 23° C. measured as described in the Examples section of 1000 to 12000 mPa·s, more preferably 3000 to 9000 mPa·s, and most preferably 5000 to 7000 mPa·s.

[0036] Suitable liquid polybutadienes can be obtained by catalytic polymerization, as described in WO 2018 / 130703 (EP 3348589), in particular in Examples 1-3.

[0037] The rubber mixture according to the invention may further comprise rubber, filler, preferably precipitated silica and / or silane, preferably and carbon black, and, if necessary, further rubber auxiliaries.

[0038] Fillers that can be used in the rubber mixtures of the present invention include, for example: Carbon black: Preferred carbon blacks for use in the present invention are produced by the lamp black, furnace black, or gas black process and preferably have a BET surface area of ​​20 to 200 m / g, such as SAF, ISAF, HSAF, HAF, FEF, or GPF black, which may optionally also contain heteroatoms, such as Si. Silica, preferably precipitated silica, is prepared, for example, by precipitation from a solution of silicate, preferably water glass, or by flame hydrolysis of a silicon halide, and preferably has a specific surface area of ​​5 to 1000 m / g. The precipitated silica preferably has a BET surface area of ​​20 to 400 m / g, particularly preferably 80 to 280 m / g, very particularly preferably 150 to 210 m / g, and very particularly preferably 80 to 180 m / g. The precipitated silica may have an average primary particle size of 5 to 400 nm, preferably 7 to 100 nm, and particularly preferably 7 to 40 nm. If desired, the silica may be in the form of a mixed oxide with other metal oxides, such as oxides of Al, Mg, Ca, Ba, Zn, and titanium. - alkaline earth metal silicates, such as aluminum silicate, magnesium silicate or calcium silicate, or synthetic silicates, such as zeolites, which preferably have a BET surface area of ​​20 to 400 m / g and a primary particle diameter of 10 to 400 nm. - Natural silicates such as kaolin, mica, kieselguhr, diatomaceous earth, talc, wollastonite or clay, or other silicates of natural origin. - Glass fibres and glass fibre products (mats, strands, fabrics) or glass microbeads. Biopolymer or bio-oligomeric fillers, such as native or modified starch, cellulose, amylose, amylopectin, cellulose acetate, maltose, cellobiose, lactose, saccharose, raffinose, glycogen, pectin, chitin, or native or modified proteins. - other oxide fillers, such as aluminium oxide, aluminium hydroxide or aluminium trihydrate, zinc oxide, boron oxide, magnesium oxide or transition metal oxides (e.g. titanium dioxide), or pyrogenic silica.

[0039] The rubber mixtures of the present invention preferably contain, in each case relative to 100 parts by weight of rubber, 0 to 150 parts by weight, more preferably 10 to 150 parts by weight, of precipitated silica, 0 to 100 parts by weight, more preferably 1 to 10 parts by weight, of carbon black, and 1 to 50 parts by weight, more preferably 10 to 40 parts by weight, even more preferably 20 to 30 parts by weight, of liquid polybutadiene.

[0040] Preferred rubber mixtures of the invention contain, in each case relative to 100 parts by weight of rubber, 10 to 150 parts by weight of precipitated silica, 0 to 100 parts by weight, more preferably 1 to 10 parts by weight of carbon black, and 1 to 50 parts by weight, more preferably 10 to 40 parts by weight, even more preferably 20 to 30 parts by weight of liquid polybutadiene.

[0041] Another preferred rubber mixture of the invention contains, in each case relative to 100 parts by weight of rubber, 0 to 150 parts by weight, more preferably 0 to 10 parts by weight, of precipitated silica, 1 to 100 parts by weight, more preferably 5 to 50 parts by weight, of carbon black, and 1 to 50 parts by weight, more preferably 10 to 40 parts by weight, even more preferably 20 to 30 parts by weight, of liquid polybutadiene.

[0042] It may be advantageous if the rubber mixture according to the invention comprises one or more organosilanes, preferably in an amount of 0.5 to 20 parts by weight, preferably 1 to 16 parts by weight, particularly preferably 2 to 12 parts by weight, very particularly preferably 3 to 7 parts by weight, of organosilane per 100 parts by weight of rubber.

[0043] The organosilane may be silicone oil, alkylsilane, vinylsilane, ethoxysilyl-containing mercaptoorganylsilane, ethoxysilyl-containing thiocyanatoorganylsilane, ethoxysilyl-containing block mercaptoorganylsilane, and / or ethoxysilyl-containing di / polysulfidoalkoxysilane.

[0044] The organosilane may preferably be a triethoxyalkylsilane, triethoxyvinylsilane, triethoxytriethoxysilyl-containing mercaptoorganylsilane, triethoxysilyl-containing thiocyanatoorganylsilane, triethoxysilyl-containing block mercaptoorganylsilane, or triethoxysilyl-containing di / polysulfide alkoxysilane. Other organosilanes that may be used include mercaptoorganyl (alkoxysilanes) having a C8H17-O-, C10H21-O-, C12H25-O-, C14H29-O-, C16H33-O-, or C18H37-O- group bonded to silicon.

[0045] Other organosilanes that may be used include block mercaptoorganyl(alkoxysilanes) having silicon-bonded CH-O-, CH-O-, CH-O-, CH-O-, CH-O-, or CH-O- groups, or block mercaptoorganyl(alkoxysilanes) having silicon-bonded difunctional alcohols (diols) (e.g., silanes from Momentive's NXT LowV, NXT Ultra-LowV, or NXT Z product lines).

[0046] Another organosilane that may be used is one having the formula: EtO-Si(Me)2-CH2-CH2-CH2-S2-CH2-CH2-CH2-Si(Me)2(OEt), EtO-Si(Me)2-CH2-CH2-CH2-S3-CH2-CH2-CH2-Si(Me)2(OEt) or EtO-Si(Me)2-CH2-CH2-CH2-S4-CH2-CH2-CH2-Si(Me)2(OEt) The polysulfide alkoxysilanes include:

[0047] Other organosilanes that may be added to the rubber mixtures of the present invention include 3-mercaptopropyl(triethoxysilane) (e.g., Si263 from Evonik Industries AG), 3-thiocyanatopropyl(triethoxysilane) (e.g., Si263 from Evonik Industries AG), Examples of suitable silyl groups include bis(triethoxysilylpropyl) polysulfide (e.g., Si264 manufactured by Evonik Industries AG), bis(triethoxysilylpropyl) polysulfide (e.g., Si69 manufactured by Evonik Industries AG), and bis(triethoxysilylpropyl) disulfide (e.g., Si266 manufactured by Evonik Industries AG).

[0048] Other organosilanes that may be used include alkyl polyether alcohol-containing mercaptoorganylsilanes (e.g., Si363 from Evonik Industries AG), alkyl polyether alcohol-containing thiocyanatoorganylsilanes, and / or alkyl polyether alcohol-containing block mercaptoorganylsilanes or alkyl polyether alcohol-containing polysulfide silanes. The alkyl polyether alcohol-containing mercaptoorganyl silane has the general formula (I): (X)3Si-R3-SH (I) wherein X is an alkyl group, an alkoxy group, or an alkyl polyether group, at least one X is an alkyl polyether group, and R3 is a branched or unbranched, saturated or unsaturated, substituted or unsubstituted aliphatic, aromatic, or mixed aliphatic / aromatic divalent hydrocarbon group. The compound may be:

[0049] The alkyl polyether alcohol-containing block mercaptoorganyl silane has the general formula (II): (X)3Si-R4-SC(O)-R5 (II) wherein X is an alkyl group, an alkoxy group, or an alkyl polyether group, and at least one X is an alkyl polyether group; R4 is a branched or unbranched, saturated or unsaturated, substituted or unsubstituted, aliphatic, aromatic, or mixed aliphatic / aromatic, divalent hydrocarbon group; and R5 is a branched or unbranched, saturated or unsaturated, substituted or unsubstituted, aliphatic, aromatic, or mixed aliphatic / aromatic, monovalent hydrocarbon group, preferably a C1-C25 hydrocarbon group, particularly preferably a C2-C22 hydrocarbon group, very particularly preferably a C7-C17 hydrocarbon group, and very particularly preferably a C11-C16 hydrocarbon group. The compound may be:

[0050] The rubber in the rubber mixture of the present invention may be one type of rubber or a mixture of different types of rubber. Preferably, the rubber in the rubber mixture of the present invention is a mixture of different types of rubber. The rubber in the rubber mixture of the present invention can be selected from natural rubber and / or synthetic rubber. Preferred synthetic rubbers are described, for example, in W. Hofmann, Kautschuktechnologie [Rubber Technology], Genter Verlag, Stuttgart 1980. These include, inter alia, polybutadiene (BR), polyisoprene (IR), styrene / butadiene copolymers (SBR) with a styrene content of 1 to 60% by weight, preferably 2 to 50% by weight, isobutylene / isoprene copolymers (IIR), butadiene / acrylonitrile copolymers (NBR) with an acrylonitrile content of 5 to 60% by weight, preferably 10 to 50% by weight, partially or fully hydrogenated NBR rubber (HNBR), ethylene / propylene / diene copolymers (EPDM), and mixtures of these rubbers. Of interest for the manufacture of automobile tires are in particular anionically polymerized S-SBR rubbers, preferably those with a glass transition temperature above 50° C., and their mixtures with diene rubbers. Rubbers that are preferably used include natural rubber or mixtures of natural rubber with diene rubbers, preferably polybutadiene, polyisobutene, or styrene-butadiene copolymers.

[0051] Most preferably, the rubber in the rubber mixture according to the invention is a mixture of neodymium butadiene rubber (Nd-BR) and styrene-butadiene random copolymer (S-SBR).

[0052] The rubber mixtures according to the invention may further comprise rubber auxiliary products such as accelerators, ageing stabilizers, heat stabilizers, light stabilizers, antiozonants, processing aids, plasticizers, resins, tackifiers, blowing agents, dyes, pigments, waxes, extenders, organic acids, flame retardants, metal oxides, and / or activators known in the rubber industry, such as triethanolamine, polyethylene glycol, hexanetriol, etc.

[0053] The rubber auxiliaries are preferably used in typical amounts determined, inter alia, by the end use application. Typical amounts are, for example, 0.1 to 50 parts by weight based on the rubber. It is generally desirable to add an additional crosslinking agent. Additional known crosslinking agents that may be used include sulfur or peroxides. The rubber mixture of the present invention may additionally contain a vulcanization accelerator. Examples of suitable vulcanization accelerators are mercaptobenzothiazole, sulfenamide, guanidine, thiuram, dithiocarbamate, thiourea, and thiocarbonate. The vulcanization accelerator and sulfur or peroxide can be used in amounts of 0.1 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of rubber.

[0054] The rubber mixtures according to the present invention can be obtained by using mixing procedures and equipment known in the art. The mixing of the rubber with the liquid polybutadiene of the present invention and any fillers and any rubber auxiliaries can be preferably carried out in conventional mixing equipment such as rollers, internal mixers, and mixing extruders. The rubber mixtures according to the present invention can also be obtained by so-called liquid phase mixing, continuous liquid phase mixing, or masterbatch combinations as described in the prior art.

[0055] The addition of the liquid polybutadiene and / or, preferably, the filler is preferably carried out at a material temperature of 50°C to 200°C, more preferably 80°C to 185°C, even more preferably 100°C to 185°C, particularly preferably 130°C to 170°C, but can also be carried out at a later or very early stage at a material temperature of 40°C to 100°C, for example together with further rubber auxiliaries.

[0056] The liquid polybutadiene may be added in pure form to the mixing operation or applied to an organic or inorganic support. Preferred support materials are silica, natural or synthetic silicates, aluminum oxide, waxes, polymers, especially polyethylene or polyethylene wax, or carbon black.

[0057] The rubber mixtures according to the invention can be used for all purposes for which rubber mixtures of the prior art can also be used. They may preferably be used for the production of molded articles, in particular pneumatic tires, lightweight tires or tire treads.

[0058] Preferably, the rubber mixture of the present invention is used as a raw material in the production of rubber products by vulcanization of the rubber mixture of the present invention. Therefore, the present invention also relates to a method for producing rubber products by vulcanization of a rubber mixture using the rubber mixture of the present invention as a raw material. The vulcanization of the rubber mixture of the present invention is preferably carried out at temperatures of 100°C to 200°C, preferably 130°C to 180°C, optionally under a pressure of 10 to 200 bar. The rubber vulcanizates thus obtained are suitable for producing molded articles. The rubber mixture of the present invention may be used to produce tires, profiles, cable sheaths, hoses, drive belts, conveyor belts, tire treads, shoe soles, sealing rings, and damping elements. If necessary, the rubber mixture of the present invention can also be vulcanized for one of the above-mentioned products using other vulcanization methods, for example, using radiation (e.g., microwave ovens or hot salt baths), in a continuous or discontinuous process.

[0059] The present invention further relates to a rubber product (product) obtainable by the method according to the present invention. The rubber product according to the present invention is preferably a tire or a tire component. More preferably, the rubber product according to the present invention is a tire tread. Most preferably, the rubber product according to the present invention is an all-season tire or a snow (winter) tire or a tire tread thereof.

[0060] Without further explanation, it is believed that those skilled in the art can make full use of the above description. Therefore, the preferred embodiments and examples should be understood only as an illustrative disclosure that is not intended to be limiting in any way.

[0061] The present invention will now be described in more detail with reference to examples, which may be used to provide further embodiments of the present invention. [Example]

[0062] Raw materials used The raw materials used are shown in Table 1 below.

[0063] [Table 1]

[0064] method Microstructure measurements Infrared spectroscopy using a polybutadiene standard was used to measure the molar ratio of the monomer units according to formulas (A), (B), and (C). An 80-250 mg sample of the polybutadiene to be tested was dissolved in 10 mL of carbon disulfide (CS₂). If a large amount of monomer units according to formula (A) was expected, a lower concentration of polybutadiene (e.g., 80 mg of sample) was used. If a large amount of monomer units according to formula (C) was expected, a higher concentration of polybutadiene (e.g., 250 mg of sample) was used. Termination was performed using a 0.5 mm thick IR cuvette (KBr). The solvent was removed and the spectrum was displayed in the absorbance evaluation range of 1100-600 cm⁻¹. If the obtained absorbance value exceeded 1, the measurement was repeated using a lower concentration of polybutadiene. The absorbance above the baseline of the following signals was measured: Trans-1,4-polybutadiene: 968 cm-1 1,2-Polybutadiene: 911 cm-1 cis-1,4-polybutadiene: 730 cm-1 The molar ratio of the monomer units is calculated according to the following formula: %Comp(i)=Ext(i)*100% / (E(i)*c*d*) where Ext(i) = absorbance above baseline, E(i) = extinction coefficient (substance specific, determined by calibration measurement) [E] = L / (g*cm), d = thickness of the cuvette (in cm), c = concentration of the sample (in g / L).

[0065] Mooney Viscosity The Mooney viscosity of the crude rubber mixtures was measured at 100° C. The MS(1+4) / MU value was measured according to DIN 53523 / 3, ISO 289-1, and the ML(1+4) / MU value was measured according to DIN 53523 / 3, ISO 289-2.

[0066] Tensile strength The ultimate tensile strength, expressed in MPa, and the elongation at break, expressed in %, of the vulcanizates were measured in accordance with DIN 53504 / ISO 37. Measurements were carried out using standard dumbbell S1 specimens at a temperature of 23°C. The pulling speed was set at 500 mm / min.

[0067] Shore hardness The Shore hardness, expressed as SH, of the vulcanizates was measured at a test temperature of 23°C in accordance with ISO 7619-1.

[0068] Rebound elasticity The impact resilience, expressed as a percentage of the vulcanizate, was measured according to ASTM D 2632 using a steel ball weighing 28 g, having a diameter of 19 mm and falling from a height of 500 mm.

[0069] Viscoelasticity The viscoelastic properties of the vulcanizates were measured in accordance with ASTM D 6601-02, DIN 53513 / ISO 4664-1, and ISO 1827.

[0070] The maximum loss factor (tan δmax) was measured in accordance with ASTM D 6601-02 using an Alpha Technologies RPA2000 as described in the operating manual dated February 1997 at 60°C, 1.6 Hz, and within the elongation range of 0.28% to 42.0%.

[0071] The complex modulus E* of the vulcanizate expressed in MPa is calculated according to DIN53513 / ISO4664-1 The measurements were carried out in accordance with the above standard using a servo-hydraulic testing machine Zwick Rel 2100 manufactured by ZwickRoell GmbH & Co. KG at 16 Hz, initial force 50, amplitude force 25 N, temperature adjustment time 5 minutes, and value recording after the test time 30 seconds.

[0072] The complex shear modulus G* expressed in MPa and the dielectric tangent tanδ are calculated in accordance with ISO1827. Based on this, measurements were taken using an EPLEXOR (registered trademark) 4000N (serial number 1101, NETZSCH GABO Instruments GmbH) in temperature sweep mode at 1.6 Hz, a dynamic deformation rate of 0.2%, a static deformation rate of 0.0%, and a temperature range of -80°C to 80°C.

[0073] The molecular weight of polybutadiene was measured using gel permeation chromatography. The measurements were carried out at 40°C in tetrahydrofuran (THF) at a concentration of 1 g / L and a flow rate of 0.3 mL / min. Chromatographic separation was performed using a PSS SDV Micro 5μ / 4.6 × 30 mm precolumn and a PSS SDV Micro linear S 5μ / 4.6 × 250 mm (2×) separation column. Detection was performed using an RI detector. Calibration was performed using polybutadiene standards (PSS-Kit polybutadiene-1,4, Mp831-106000, part number: PSS-bdfkit, Mn: 1830 / 4330 / 9300 / 18000 / 33500).

[0074] viscosity The viscosity (cone-plate type) of the polybutadiene was measured in accordance with DIN53018 using a Rheometer Physica MCR 301 manufactured by ANTON PAAR Germany GmbH.

[0075] Experimental Example 1 The formulations used in the rubber mixtures are set forth in Table 2 below for stages 1, 2 and 3. In this table, the unit phr means parts by weight per 100 parts of rubber (S-SBR and Nd-BR) used. Liquid polybutadiene (LBR) is used in various amounts as a replacement for the plasticizer oil "TDAE" in the rubber mixtures of the present invention.

[0076] [Table 2]

[0077] Plasticizer oil (e.g., LBR XX%) and TDAE have low melting points and are 5.0 The mixture was applied using a treatable LDPE bag (Polybeutel 150 x 200 mm, IGEFA Handelsgesellschaft) filled with phr.

[0078] General methods for producing rubber mixtures and vulcanizates thereof are described in "Rubber Technology Handbook", W. Hofmann, Hanser Verlag (1994).

[0079] The equipment and parameters used to process each rubber mix are shown below in Table 3a for Stage 1, Table 3b for Stage 2, and Table 3c for Stage 3.

[0080] [Table 3a]

[0081] [Table 3b]

[0082] [Table 3c]

[0083] The Mooney viscosities of the rubber mixtures (sheets) obtained after the first and third stages were measured as described above, and the results are shown in Table 4.

[0084] The rubber mixture obtained after the third stage was vulcanized to obtain test plates and specimens. Vulcanization was carried out in a typical vulcanization press at a compression pressure of 130 bar for 17 minutes at a temperature of 165°C, with an optimum cure time t95. The t95 time was measured in a die rheometer (rotorless vulcanometer) at 165°C according to the DIN 53529 / 3 procedure.

[0085] Rubber testing was performed according to the test methods described above, and the results of the rubber testing are also shown in Table 4.

[0086] [Table 4]

[0087] The rubber mixture IV according to the invention has improved processability compared to the rubber mixtures I to III, which is shown by the lower Mooney viscosity values ​​of the rubber mixture IV according to the invention after the first and third stages.

[0088] Surprisingly, the rubber mixture IV used according to the invention achieves a higher reinforcing effect than all the other mixtures, since it not only has the highest tensile strength but also the highest elongation at break. The similar hardness allows a good comparison of the dynamic data. Compared to the comparative rubber mixtures I, II, and III, the rubber mixture IV according to the invention exhibits a lower hysteresis in the dynamic test at 60°C, which is important for predicting rolling resistance. This can be seen in the high rebound values ​​(i.e., improved values ​​compared to other compounds containing liquid polybutadiene) and is confirmed by the smallest maximum tan δ measured at 60°C. Therefore, when a tire is equipped with a tread based on a rubber mixture according to the invention, the rubber mixture according to the invention should result in improved rolling resistance and lower fuel consumption.

[0089] At the same time, rubber mixture IV according to the invention is able to achieve a high dynamic complex modulus (E* and G* at 60°C) measured at an elevated temperature of 60°C, which, according to the literature, is an indicator for predicting the dry traction of passenger car tires. Improved dry handling of passenger car tires equipped with tread compounds made from rubber mixture IV according to the invention can be expected, especially compared to the comparative rubber mixtures II and III. Furthermore, rubber mixture IV according to the invention shows higher loss factor values ​​at -10°C than the comparative rubber mixtures II and III. According to the relevant literature, the use of this mixture as a base for tread mixtures for winter tires improves the winter properties and / or has a positive effect on wet grip. It is not.

Claims

1. A rubber mixture comprising a rubber and a liquid polybutadiene, The polybutadiene is liquid at a temperature of 20° C. and a pressure of 98.0665 kPa; The liquid polybutadiene comprises 1,3-butadiene derived monomer units: 【Chemistry 1】 Including, a proportion of A in all of the 1,3-butadiene-derived monomer units present in the liquid polybutadiene is 55 to 70 mol %; the total proportion of B and C in all the 1,3-butadiene-derived monomer units present in the liquid polybutadiene is 30 to 45 mol %; The liquid polybutadiene contains only C and H atoms and has an average molecular weight (Mw) of 1500 to 5000 g / mol, as determined by gel permeation chromatography as described herein.

2. 2. The rubber mixture of claim 1, comprising, in each case, based on 100 parts by weight of said rubber, 0 to 150 parts by weight of precipitated silica, 0 to 100 parts by weight of carbon black, and 1 to 50 parts by weight of said liquid polybutadiene.

3. 3. A rubber mixture according to claim 1, which comprises an organosilane.

4. 4. The rubber mixture of claim 3, comprising from 0.5 to 20 parts by weight of organosilane per 100 parts by weight of said rubber.

5. A rubber mixture according to any one of claims 1 to 4, wherein the rubber is one type of rubber or a mixture of different types of rubber.

6. A rubber mixture according to any one of claims 1 to 5, wherein the rubber is selected from natural rubber and / or synthetic rubber.

7. 7. A rubber mixture according to claim 5 or claim 6, wherein the rubber is a mixture of Nd-BR and S-SBR.

8. 8. A rubber mixture according to claim 1, wherein the liquid polybutadiene has an average molecular weight (Mw) of 1750 to 3500 g / mol, as determined by gel permeation chromatography.

9. A method for producing a rubber product by vulcanizing a rubber mixture, using the rubber mixture according to any one of claims 1 to 8 as a raw material.

10. A rubber product obtainable by the method of claim 9.

11. The rubber article of claim 10, which is a tire or part of a tire.

12. The rubber article of claim 11 which is a tire tread.

13. 13. The rubber product according to claim 11 or 12, wherein the tire is an all-season tire or a snow (winter) tire.

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