Oil-extended polybutadiene polymer

Abstract

A polymer composition comprising at least 95% by weight, based on the total weight of the composition, of at least one curable, oil-extended polybutadiene polymer obtained by blending a polybutadiene polymer with at least one oil, wherein the polybutadiene polymer has a 1,4-cis content of at least 92% and comprises at least 90% by weight, preferably at least 95% by weight, based on the weight of the polymer, of units derived from butadiene, wherein the oil comprises at least one ester of a glycerol and at least one carboxylic acid. Also provided are methods for preparing such compositions.

Description

[0001] Oil-extended polybutadiene polymer

[0002] Polybutadiene polymers are a raw material for many industrial items, in particular tires. They can be prepared at large scale using catalysts or catalyst systems as described, for example, in US2002 / 0107339A1.

[0003] Depending on the catalyst used fortheir production the butadiene rubbers are classified in the art as LiBR, CoBR, GdBR, NdBR and the like.

[0004] Generally, the mechanical properties of butadiene rubbers increase with their molecular weight. However, with increasing molecular weight also the Mooney viscosity increases and makes the polymers difficult to process. Extender oils may be added to the polymers to reduce their Mooney viscosity and to facilitate their processing. For example, an SSBR extended with soybean oil is described in US 10,435,545 B2. The oil-extended polymers can be combined with other ingredients to produce a compound by tire manufacturers prior to subjecting the compound to curing for producing a rubber article, such as a tire. The addition of an extender oil, however, increases the cold flow of the polymer. Cold flow means the polymer changes its shape overtime, which leads to problems when handling or storing the polymers. For example, a high cold flow can cause stacks of polymer bales to collapse during transport or storage.

[0005] Good mechanical performance of rubber is not only attributed to its molecular weight but also to its microstructure, in particular to a high content of “cis-units” in the polymer architecture. “High-cis-polybutadienes” have a content of cis units of at least 92%.

[0006] There is a need to provide oil-extended rubbers with a high cis-content that have a reduced cold flow. Polybutadiene polymers are available as copolymers, for example copolymers of styrene and butadiene (also known as SBR) or as homopolymers (also known as polybutadiene rubbers or BR)

[0007] Summary

[0008] Therefore, in one aspect there is provided a polymer composition comprising at least 95% by weight, based on the total weight of the composition, of at least one curable, oil-extended polybutadiene polymer obtained by blending a polybutadiene polymer with at least one oil, wherein the polybutadiene polymer has a 1 ,4-cis content of at least 92 % and comprises at least 90 % by weight, preferably at least 95% by weight, based on the weight of the polymer, of units derived from butadiene, wherein the oil comprises at least one ester of a glycerol and at least one carboxylic acid.

[0009] In another aspect there is provided a method for preparing a polymer composition according to any one of the preceding claims comprising blending at least one oil with a curable polybutadiene polymer having a 1 ,4-cis content of at least 92 % and comprising at least 90% by weight, preferably at least 95% by weight, based on the weight of the polymer, of units derived from butadiene with at least one oil that comprises at least one ester of a glycerol and at least one carboxylic acid.

[0010] Detailed Description

[0011] The present disclosure will be further illustrated in the following detailed description.

[0012] In the following description certain standards (ASTM, DIN, ISO etc.) may be referred to. If not indicated otherwise, the standards are used in the version that was in force on March 1 , 2020. If no version was in force at that date because, for example, the standard has expired, then the version is referred to that was in force at a date that is closest to March 1 , 2020.

[0013] In the following description the amounts of ingredients of a composition or a polymer may be indicated interchangeably by “weight percent”, “wt. %” or “% by weight”. The terms “weight percent”, “wt. %” or “% by weight” are based on the total weight of the composition or polymer, respectively, which is 100 % unless indicated otherwise.

[0014] The term “phr” means “parts per hundred parts of rubber”.

[0015] Ranges identified in this disclosure are meant to include and disclose all values between the endpoints of the range and its end points, unless stated otherwise.

[0016] The terms “comprising”, “containing” and “having” are used in an open, non-limiting meaning. For example, the phrase “a composition comprising ingredients A and B” is meant to include ingredients A and B but the composition may also have other ingredients. Contrary to the use of “comprising”, “containing” or “having” the word “consisting of” is used in a narrow, limiting meaning. The phrase “a composition consisting of ingredients A and B” is meant to describe a composition of ingredients A and B and no other ingredients.

[0017] Polymer compositions

[0018] The polymer compositions according to the present disclosure comprise, or consist of, at least one curable, oil-extended polybutadiene. Preferably, the polymer compositions comprise at least 75% by weight or at least 95% by weight, based on the total weight of the composition, of at least one curable, oil-extended polybutadiene. Preferably, the polymer compositions comprise at least 96% by weight or 97 % by weight or even at least 99% by weight of the oil-extended polymer. The oil-extended polybutadiene can be obtained by blending a curable polybutadiene polymer with at least one oil. “Wet blending” or “dry blending” may be used but “wet blending” is preferred. “Wet blending” comprises mixing the oil into a polymer solution and removing the solvent, preferably after the blending is complete. Preferably, the oil is added to the reaction mixture obtained by the polymerization of butadiene in at least one solvent.

[0019] The polybutadiene polymer may be a homopolymer or a copolymer of butadiene. Preferably, the polymer comprises at least 91 % by weight, more preferably at least 95% by weight, based on the weight of the polymer, of units derived from butadiene.

[0020] The polybutadiene polymers are curable. They can be cured or cross-linked (“vulcanized”) upon reaction with a curing agent or a curing system comprising at least one curing agent to produce vulcanized compositions.

[0021] Preferably, the polybutadiene polymers comprise more than 90% by weight, preferably at least 95% by weight, or even at least 99% by weight of units derived from butadiene, wherein the “% by weight” are based on the total weight of the polybutadiene polymer. Suitable comonomers include, but are not limited to, conjugated dienes - other than butadiene -having from 5 to 24, preferably from 5 to 20 carbon atoms. Specific examples include, but are not limited to, isoprene, 1 ,3-pentadiene, 2,3-dimethylbutadiene, 1-phenyl- 1 ,3-butadiene, 1 ,3-hexadiene, myrcene, ocimene, farnesene and combinations thereof. The comonomers may be functionalized at one or more positions to provide functionalities other than carbon-hydrogen bonds. Such other functionalities may include cross-linking sites, for example at least one additional carbon-carbon-unsaturation, or at least one polar functional group. Suitable comonomers also include one or more other co-polymerizable monomers that introduce branches into the polymer backbone, for example non-conjugated dienes, preferably non-conjugated alpha-omega bisolefins, more preferably alpha-omega bis-dienes. Combinations of different comonomers may be used.

[0022] The butadiene monomers or the comonomers or both may be conventional materials but may also be obtained from sustainable materials, for example for reducing the carbon dioxide footprint of the polymer or the article made with the polymer. Sustainable materials include renewable or recycled materials. Renewable materials include, but are not limited to, monomers and comonomers obtained from plant-based materials or produced by bacteria, which may be genetically modified or not. Recycled materials include monomers and comonomers obtained from recycling carbon-containing waste material for example by pyrolysis of carbon-containing material, which may include plant-based materials for example pulp or fibers or carbon-containing waste material. The polybutadiene polymers according to the present disclosure may have a molecular weight distribution (MWD), i.e., a ratio of Mw / Mn, from 1.5 to 15. In one embodiment of the present disclosure the polymers have an MWD of from 1.5 to 7.5. or from 1.5 to 4. In a preferred embodiment the polymers have an MWD of 3.0 or less, for example from and including 2.0 and up to and including 3.0.

[0023] The polybutadiene polymers according to the present disclosure may have a glass transition temperature (Tg) of from -120°C to 0°C. In a preferred embodiment of the present disclosure the polymers have a Tg of from -110°C to -10°C, more preferably between -93°C and - 110°C.

[0024] The polymers according to the present disclosure may have a molecular weight (weightaverage Mw) of from 100,000 to 2,500,000 g / mole. In one embodiment the polymers have an Mw of from 450 kg / mol to 1 ,000 kg / mol. The polymers according to the present disclosure may have a number-average molecular weight (Mn) of from 105 kg / mol to 650 kg / mol.

[0025] The polybutadiene polymers used for making the oil-extended polymers may have a Mooney viscosity ML 1+4, at 100°C from 42 to 150 units, for example from50 to 120, or from 55 to 130, or from 60 to 129 units. In one embodiment of the present disclosure the polymers are provided having a low Mooney viscosity from 42 to 63 units, or, for example, from 43 to 60 units or from 46 to 58 units. In another embodiment of the present disclosure the polymers have a Mooney viscosity of 63 to 150 units, for example from 63 to 126 units, from 64 to 92 units or from 74 to 82 units. In one embodiment the modified polymers according to the present disclosure have a Mooney viscosity from 63 to 94, preferably from 63 to 86 units.

[0026] The polybutadiene polymers used for making the oil-extended polymers according to the present disclosure are preferably prepared by a polymerization using a polymerization catalyst or catalyst system comprising at least one rare earth catalyst. After the polymerization or towards the end of the polymerization the polymers may or may not be subjected to a treatment with one or more modifiers to increase the Mooney viscosity of the polymers, or their degree of branching or their shear sensitivity or a combination thereof. Rare earth catalysts include catalysts containing neodymium, praseodymium, cerium, lanthanum, gadolinium and dysprosium or a combination thereof. In a more preferred embodiment, the polymerization is carried out comprising a neodymium catalyst or a cobalt catalyst. Preferably the polybutadiene polymer is prepared by using a Ziegler-Natta type rare earth, preferably neodymium, catalyst composition. Typically, a Ziegler-Natta type catalyst system contains at least three components: a rare earth metal source (e.g., a neodymium source), a chloride source and an organo aluminum compound. Such catalyst systems are described, for example, in Canadian Patent application CA 1 ,143,71 1 A and US Patent Number 4,260,707, both incorporated herein by reference. The metal source may include an alkoxide, phosphate or carboxylate of the catalyst metal, (e.g., neodymium). Preferably, the metal source is selected from a metal carboxylate according to formula (1): wherein M represents a rare earth metal selected from cerium, neodymium, praseodymium, gadolinium, lanthanum, preferably neodymium (Nd), and wherein R1, R2, and R3, which may be the same or different, each represent an alkyl group having from 1 to 10 carbon atoms. Preferably, the sum of all the carbon atoms in the substituents R1, R2and R3is from 6 to 20. A particularly preferred metal source is neodymium versatate. A combination of different metal sources may be used also.

[0027] Suitable organo aluminum compounds include those according to the formula AI(R4)3, AI(R4)2H and AI(R4)H2wherein R4represents a aliphatic or aromatic hydrocarbon, preferably an alkyl group having from 1 to 10 carbon atoms, preferably ethyl or isobutyl. Specific examples include but are not limited to trimethylaluminum, triethylaluminum, tri-n- propylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum (TIBA), tri- t-butylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluminum, trioctylaluminum and dihydrocarbylaluminum hydrides including, for example, diethylaluminum hydride, di-n-propylaluminum hydride, diisopropylaluminum hydride, di-n- butylaluminum hydride, diisobutylaluminum hydride (DIBAH), di-n-octylaluminum hydride, diphenylaluminum hydride, di-p-tolylaluminum hydride, dibenzylaluminum hydride, phenylethylaluminum hydride, phenyl-n-propylaluminum hydride, phenylisopropylaluminum hydride, phenyl-n-butylaluminum hydride, phenylisobutylaluminum hydride, phenyl-n- octylaluminum hydride, p-tolylethylaluminum hydride, p-tolyl-n-propylaluminum hydride, p- tolylisopropylaluminum hydride, p-tolyl-n-butylaluminum hydride, p-tolylisobutylaluminum hydride, p-tolyl-n-octylaluminum hydride, benzylethylaluminum hydride, benzyl-n- propylaluminum hydride, benzylisopropylaluminum hydride, benzyl-n-butylaluminum hydride, benzylisobutylaluminum hydride, benzyl-n-octylaluminum hydride; and hydrocarbylaluminum dihydrides including, for example, ethylaluminum dihydride, n- propylaluminum dihydride, isopropylaluminum dihydride, n-butylaluminium dihydride, isobutylaluminum dihydride, and n-octylaluminum dihydride, and including combinations thereof. A preferred organo aluminum compound includes diisobutyl aluminum hydride.

[0028] The chloride source is preferably selected from an alkyl aluminum chloride, for example including but not limited to diethyl aluminum chloride, ethyl aluminum sesquichloride, ethyl aluminum dichloride and combinations thereof.

[0029] The catalyst composition may further contain a conjugated diene and may be pre-formed with it. The catalyst system may be pre-formed, i.e., generated before it is added to the polymerization reactor or its components may be added directly simultaneously or sequentially to the polymerization reactor, preferably dissolved in a solvent.

[0030] Preferably, the polybutadiene polymers prepared with a rare earth catalyst or catalyst system, for example a neodymium-based catalyst or Nd catalyst system (Nd-catalyzed polybutadienes) or a cobalt-based catalyst or Co catalyst system, or a gadolinium-based catalyst or Gd catalyst system. In one embodiment of the present disclosure the polybutadiene polymer is prepared with a neodymium-based catalyst, preferably with a Ziegler-Natta type neodymium catalyst composition comprising a neodymium catalyst, a chloride source, and an organo aluminum hydride.

[0031] During the polymerization reaction the butadiene monomer (CH2=CH-CH=CH2) can be incorporated into the growing polymer chain as “1 ,4-cis”, “1 ,4-trans” and “1 ,2-vinyl” repeat units. Units of the structure -CH2-CH=CH-CH2- are referred to as “1 ,4-cis units” or “cis-units” when both -CH2groups are on the same side of the double bond. When they are on opposite sides, the unit is referred to as “trans unit” or “1 ,4-trans unit”. A “vinyl unit” or “1 ,2-vinyl unit” has the structure -CH2-CH(CH=CH2)-. The ratio of such units making up the polymer is referred to as the microstructure of the polymer. Preferably, the polybutadiene polymer according to the present disclosure has a 1 ,4-cis content of at least 92 %, preferably at least 96%. The production of butadiene polymers with a high cis content (and thus low trans and vinyl content) is known. “High-cis-polybutadiene polymers” are known to have good dynamic mechanical properties and are commercially readily available, for example under the trade designation BUNA from ARLANXEO Deutschland GmbH.

[0032] The polymerization preferably is carried out as solution polymerization. Typical reaction temperatures for the polymerization are between 60° C and 140° C. Suitable inert solvents include, for example, aromatic, aliphatic and cycloaliphatic hydrocarbons. Specific examples include but are not limited to benzene, toluene, pentane, n-hexane, isohexane, heptane, isomeric pentanes, methyl cyclopentane and cyclohexane. The solvents may be used individually or in combination or blended with one or more polar solvents. The inert organic solvents may be used in amounts of 200 to 900 parts by weight based on 100 parts by weight of monomers. The polymerization may be carried out continuously or batchwise. Processes as known in the art may be followed generally, including the industrial processes described, for example, in US2002 / 0107339A1.

[0033] The polybutadiene polymer may be linear, but steps may be taken to create polymer branching. The degree of linearity or branching can be determined by the branching degree AS. The higher the AS value the less branched and the more linear is the polymer. In one embodiment of the present disclosure the polybutadiene polymer is at least substantially linear and has a AS of at least 25°. In another embodiment of the present disclosure the polymer is at least substantially branched and has a branching degree AS of less than 25°, preferably less than 20°. For example, the polymers may have a AS of 8 to 17 or from 6 to 13. For example, polymer branching can be created by polymerizing at elevated temperatures (thermo-induced branching) for sufficient time (polymer conversion) as described, for example in US2013 / 0172489 A1. Another way includes the use of branching-inducing comonomers in the polymerization reaction, for example using non-conjugated dienes including alpha-omega poly- or bisolefins, for example alpha-omega dienes. Yet another way involves adjusting the components of the catalyst system and their amounts as described, for example, in US201 1 / 1 12261 A1.

[0034] By generating the polymer branches in situ, i.e., during the polymerization, the branches are connected to the polymer backbone by carbon-carbon bonds and not via heteroatoms. Branching may also be introduced after the polymerization has been completed or towards the end of the polymerization, for example by using one or more coupling agent or one or more branching modifiers. Coupling agents include Si- or tin-based coupling agents. Branching modifiers include sulfur-based modifiers. The treatment with the sulfur-based modifiers may increase the Mooney viscosity of the polymers.

[0035] The sulfur-based modifiers may be used as described in the art, for example, in US patent numbers: US 9,845,366, US 9,963,519 and US 5,567,784. The treatment with a sulfur- containing modifier may lead to incorporation of sulfur atoms into the polymer and to the creation of sulfur-carbon bonds in the polymer. The terms “sulfur-based modifier” and “sulfur-containing modifier” are used herein interchangeably. They both denote a modifier that comprises sulfur. The amount of sulfur bonded to the polymer may be determined by measuring the sulfur content after the polymer has been subjected to extraction. In one embodiment, the oil-extended polybutadienes according to the present disclosure may have a content of polymer-bound sulfur (measured after Soxhlet extraction of 1 g polymer sample with 50 mL of acetone (> 99% purity) under reflux for 48 hours) of from about 12 ppm to about 20,000 ppm, preferably from about 20 ppm to about 2,000 ppm based on the total weight of the polymer, or from 200 ppm to 3,000 ppm based on the total weight of the polymer. The extraction can be carried out to distinguish between polymer-bound sulfur and sulfur that may be present in the composition as part of stabilizers like antioxidants but that is not bound to the polymer. Extraction as described in the experimental section will remove the sulfur originating from additives.

[0036] The modification treatment may be carried out, preferably, in the reaction mixture, preferably after the polymerization was stopped and, preferably, before the work up procedure. Preferably, the treatment is carried out in the reaction mixture. The polymerization may be stopped prior to the treatment with the sulfur-based modifiers or afterwards, for example by adding materials that deactivate the catalyst. Such materials include protic materials including, for example, organic acids. The modifiers may be added at the same temperature or at higher or lower temperatures than the polymerization temperature. For example, the modifiers can be added without requiring the reaction temperature to be raised or lowered or after degassing as is described in the references cited above. The sulfurbased modifier may be added as pure substance or as solution and may be added as solid, liquid or as a spray. The addition of the modifier may take place in the same polymerization reactor or in a different reactor or in a pipe. The amount of modifier to be used depends on the final branching degree AS and Mooney viscosity to be achieved as well as the initial branching degree and Mooney viscosity of the polymer. Suitable amounts can be selected to achieve the desired AS and Mooney viscosity. Preferably, an appropriate amount of one or more sulfur modifiers are used to increase the Mooney viscosity and / or reduce the branching AS such that the value of the quotient of Mooney viscosity ML 1 +4, 100°C I polymer AS is from 4.6 to 46, or from 4.6 to 26, or from 4.6 to 14. In one embodiment of the present disclosure the polymers have a ratio of polymer Mooney viscosity ML 1+4, 100°C / polymer AS of 4.6 to 8.8 or from 4.9 to 8.7. Typical amounts of modifying agent(s) may include from 0.005 to 2 parts by weight per hundred parts of polymer or from 0.007 to 0.5 parts per hundred parts of polymer or from 0.1 to 0.4 parts per hundred parts of polymer.

[0037] Suitable sulfur-containing modifiers include sulfur halides, more preferably sulfur bromides and sulfur chlorides and polysulfur halides. Preferably, the sulfur-containing modifiers have between 1 to 8 sulfur atoms per molecule, preferably one or two sulfur atoms per molecule. Suitable examples include but are not limited to S2CI2, SCI2, SOCI2, S2Br2, SOBr2. It is contemplated that also functionalized sulfur-based modifiers containing a functional group R may be used. Examples of such modifying agents are described in US2016 / 0280815 A1. Another approach to introduce functional groups into the polymer may be achieved by functionalizing the polymer with polar comonomers prior to treatment with a sulfur-based modifier as described, for example, in European Patent EP 2 819 853 B1. In one embodiment of the present disclosure the polymer does not have any functional groups other than those created by a sulfur-based modifiers, which preferably is not further functionalized to contain any organic groups, i.e., groups having carbon and hydrogen atoms. In one embodiment the polymer does not have any functionalized end groups at least no functionalized end groups and / or in-chain functional groups generated by one or more functionalizing agents other than the sulfur-based modifiers.

[0038] The polymers can be isolated as known in the art, for example by removing the solvent, for example by stripping, for example steam stripping, or by coagulation achieved for example by adding a liquid in which the polymer is not soluble. Recovered solvents and monomers can be recycled. The polymer can be dried as known in the art and shaped into granules, compressed into bales or used as crumbs or powders. Preferably, one or more oil is added to the reaction mixture comprising the polybutadiene polymer and solvent and blended with the polymer to prepare an oil-extended polymer. Preferably, the solvent is recovered after the oil-extended polymer has been prepared.

[0039] Oil

[0040] Preferably, the oil used for making the polymer compositions comprising the oil-extended polymer comprise an ester of a glycerol and carboxylic acid, preferably an ester of glycerol and at least one fatty acid. Preferably, the oil is a triglyceride oil, i.e., it comprises or consists of at least one triglyceride. Preferably, the triglyceride is an ester of glycerol with up to three carboxylic acids, preferably fatty acids, which may be identical of different. The carboxylic acid may be saturated or unsaturated and, preferably, comprises at least one unsaturated carboxylic acid, preferably an unsaturated fatty acid. The at least one unsaturated carboxylic acid can be monounsaturated or polyunsaturated. The carboxylic acid preferably has from 4 to 36 carbon atoms. Examples of fatty acids include linolenic acid, linoleic acid, and oleic acid. Preferably, the extender-oil is a sustainable or bio-based oil. The bio-based oil may originate from plants, animals or may be produced by fungi or microorganisms. Preferably, the bio-based oil is a vegetable oil. Examples of bio-based oils include but are not limited to soybean oil, sunflower oil, canola (rapeseed) oil, corn oil, coconut oil, cottonseed oil, olive oil, palm oil, nut oil and safflower oil. Preferably, the oil has a refractive index of 1 .48 or less at 10°C.

[0041] Compositions

[0042] Compositions according to the present invention comprise the polybutadiene polymer in oil- extended form. Typically, the compositions comprise from 1 % to 50% by weight of oil, based on the total weight of the composition. The addition of oil typically reduces the Mooney viscosity of the polymer. Therefore, the polymer compositions according to the present disclosure, comprising the oil-extended polybutadiene, may have a lower Mooney viscosity than the polymer used to make the composition. For example, the composition according to the present disclosure may have Mooney viscosity ML 1 +4 at 100°C of less than 60, or less than 55 Mooney units, for example from 30 to 59 Mooney units, or from 20 to 50 units.

[0043] In one embodiment of the present disclosure there is provided a polymer composition wherein the polybutadiene polymer has a AS of at least 25° and the amount of extender oil is from 1 up to 24% by weight, preferably from 5 up to 22%. In another embodiment of the present disclosure there is provided a polymer composition wherein the polybutadiene polymer has a AS of less than 25°, preferably less than 20°, and the amount of extender oil is from 1 to 50% by weight, preferably from 1 1% up to 45% by weight or up to 30% by weight. The % by weight are based on the polymer composition.

[0044] The polymer compositions according to the present disclosure have a low clod flow. In one embodiment of the present disclosure the polymer composition has a cold flow of less than 20g 1 10 min at 50°C, preferably less than 15 g / 10 min and, preferably, a AS of at least 25°, preferably at least 20°. In another embodiment of the present disclosure the polymer composition has a cold flow of less than 10g / 10 min at 50°C, preferably less than 5g / 10 min at 50°C and, preferably, has a AS of less than 20°, preferably less than 15°.

[0045] Further, the compositions may comprise additives, such as aging stabilizers. The ageing stabilizers are preferably added into the reaction mixture containing the polymer in dissolved form. They may be added prior or after the addition of the oil. In one embodiment of the present disclosure the polymer composition comprises a first and a second anti-ageing stabilizer. Preferably, the first anti-ageing stabilizer is a phenolic compound comprising at least one phenol ring having at least one thia-alkyl substituent at the phenol ring. Preferably, the second stabilizer is a phenolic comprising at least one tert-butanol substituent at the phenolic ring. The total amount of stabilizers may range between 0.1 phr and 5 phr, preferably between 0.2 to 1 .5 phr. Commercial stabilizers and stabilizers as known in the art may be used. The addition of the stabilizers may lead to less variation of the Mooney viscosity of the composition upon heat treatment compared to the use of other stabilizers, such as 6-PPD, i.e., N-(1 ,3- Dimethylbutyl)-N’-phenyl-p-phenylenediamine. Examples of suitable first and second stabilizers include but are not limited to:

[0046] The polymer compositions according to the present disclosure comprising at least one oil- extended polybutadiene polymer can be used for making rubber compounds as known in the art. The rubber compounds may typically contain from 5% to 75%, or from 7 to 50% by weight, based on the total weight of the compound, of the polybutadiene polymer composition.

[0047] The rubber compounds, for example, may be in the form of a powder, in the form of granules, extruded pellets, sheets or bales. Such rubber compounds may further contain one or more filler, one or more rubber auxiliaries, one or more curing agent, and / or one or more rubber other than the hydrogenated butadiene polymer.

[0048] Filler

[0049] Preferably, the rubber compound comprises at least one filler, preferably a filler that is suitable for application in tires, tire components and materials for making tires. Preferably, the filler contains one or more silica, one or more carbon black or a combination of one or more silica and one or more carbon black. Preferably, the filler includes silica-containing particles, preferably having a BET surface area (nitrogen absorption) of from 5 to 1 ,000, preferably from 20 to 400 m2 / g. Such fillers may be obtained, for example, by precipitation from solutions of silicates or by flame hydrolysis of silicon halides. Silica filler particles may have particle sizes of 10 to 400 nm. The silica-containing filler may also contain oxides of Al, Mg, Ca, Ba, Zn, Zr or Ti. Other examples of silicon-oxide based fillers include aluminum silicates, alkaline earth metal silicates such as magnesium silicates or calcium silicates, preferably with BET surface areas of 20 to 400 m2 / g and primary particle diameters of 10 to 400 nm, natural silicates, such as kaolin and other naturally occurring silicates including clay (layered silicas). Further examples of fillers include glass particle-based fillers like glass beads, microspheres, glass fibers and glass fiber products (mats, strands).

[0050] Polar fillers, like silica-containing fillers, may be modified to make them more hydrophobic. Suitable modification agents include silanes or silane-based compounds. Typical examples of such modifying agents include, but are not limited to compounds corresponding to the general formula (2):

[0051] (R1R2R3O)3Si-R4-X (2) wherein each R1, R2, R3is, independently from each other, an alkyl group, preferably R1, R2, R3are all methyl or all ethyl, R4is an aliphatic or aromatic linking group with 1 to 20 carbon atoms and X is sulfur-containing functional group and is selected from -SH, -SCN, - C(=O)S or a polysulfide group.

[0052] Filler based on metal oxides, other than silicon oxides, include zinc oxides, calcium oxides, magnesium oxides, aluminum oxides and combinations thereof. Other fillers include metal carbonates, such as magnesium carbonates, calcium carbonates, zinc carbonates and combinations thereof, metal hydroxides, including aluminum hydroxide, magnesium hydroxide and combinations thereof, salts of alpha-beta-unsaturated fatty acids and acrylic or methacrylic acids having from 3 to 8 carbon atoms including zinc acrylates, zinc diacrylates, zinc methacrylates, zinc dimethacrylates and mixtures thereof.

[0053] A typical rubber compound contains one or more fillers based on carbon, for example one or more carbon black. The carbon blacks may be produced, for example, by the lamp-black process, the furnace-black process or the gas-black process. Preferably, the carbon back has a BET surface area (nitrogen absorption) of 20 to 200 m2 / g. Suitable examples include but are not limited to SAF, ISAF, HAF, FEF and GPF blacks.

[0054] Other examples of suitable filler include carbon-silica dual-phase filler, lignin or lignin-based materials, starch or starch-based materials including fillers obtained from sustainable or plant-based materials and combinations thereof.

[0055] Typical amounts of filler include from 5 to 200 parts per hundred parts of rubber, for example, from 10 to 150 parts by weight, or from 10 to 95 parts by weight for 100 parts by total weight of rubber.

[0056] Fillers from a renewable or sustainable resource may be used, for example silica materials obtained from plants, like plant husks, including, for example rice husks. Carbon-based fillers may be obtained, for example, from recycled materials. Curing agents:

[0057] Preferably the rubber compounds also contain at least one curing agent for curing the polybutadiene polymer. The curing agent is capable of crosslinking (curing) the polymer and is also referred to herein as “crosslinkers” or “vulcanization agent”. Suitable curing agents include, but are not limited to, sulfur, sulfur-based compounds, and organic or inorganic peroxides. In a preferred embodiment the curing agent includes a sulfur. Instead of a single curing agent a combination of one or more curing agents may be used, or a combination of one or more curing agent with one or more curing accelerator or curing catalysts may be used. Examples of sulfur-containing compounds acting as sulfur-donors include but are not limited to sulfur, sulfur halides, dithiodimorpholine (DTDM), tetramethylthiuramdisulphide (TMTD), tetraethylthiuramdisulphide (TETD), and dipentamethylenthiuramtetrasulphide (DPTT). Examples of sulfur accelerators include but are not limited to amine derivates, guanidine derivates, aldehydeamine condensation products, thiazoles, thiuram sulphides, dithiocarbamates and thiophospahtes. Examples of peroxides used as vulcanizing agents include but are not limited to di-tert.-butyl-peroxides, di-(tert.-butyl-peroxy-trimethyl- cyclohexane), di-(tert.-butyl-peroxy-isopropyl-)benzene, dichloro-benzoylperoxide, dicumylperoxides, tert.-butyl-cumyl-peroxide, dimethyl-di(tert.-butyl-peroxy)hexane and dimethyl-di(tert.-butyl-peroxy)hexine and butyl-di(tert.-butyl-peroxy)valerate. A vulcanizing accelerator of sulfene amide-type, guanidine-type, or thiuram-type can be used together with a vulcanizing agent as required.

[0058] If added, the vulcanizing agent is typically present in an amount of from 0.5 to 10 parts by weight, preferably of from 1 to 6 parts by weight per 100 parts by weight of rubber.

[0059] Other rubbers

[0060] The rubber compounds may contain one or more additional rubber other than the polybutadiene polymers of the present disclosure. Examples of such other rubbers include but are not limited to high-vinyl polybutadienes (i.e. vinyl content of at least 10% by weight), copolymers of butadiene with C1-C4-alkyl acrylates, chloroprenes, polyisoprenes, styrenebutadiene copolymers, isobutylene-isoprene copolymers, butadiene-acrylonitrile copolymers, including those having an acrylonitrile content of from 5 wt. % to 80 wt. %, for example those with an acrylonitrile content of from 10 wt. % to 40 wt. %; partially or fully hydrogenated acrylonitrile rubber, ethylene-propylene-diene copolymers, natural rubber and combinations thereof. Typical amounts of the one or more other rubbers in the compound may include, for example, from 5 to 500 parts per hundred parts of the polybutadiene polymer. The rubber compound may contain at least one styrene-butadiene copolymer, preferably in an amount of from 5% to 65% by weight, or from 10% to 50% by weight based on the total weight of the compound. The styrene-butadiene copolymer may be modified to contain one or more than one functional group comprising one or more than one atom selected from Si, O, N and S atoms, preferably the functional group comprises Si and O atoms. The functional group may be situated at the terminal position of the polymer in case of a-, CD- or a- and ro- functionalization as described, for example, in international patent application W02021 / 009156 A1 ; US patent applications US 2016 / 0083495 A1 and US2016 / 0075809 A1 , and in European patent application EP 2847264 A1 , all incorporated herein by reference. The functional group may also be a pending group, e.g., as part of an in-chain- functional group, for example by treatment with mercapto acids, or mercapto polyethers as described, for example, in US 6,521 ,698 B2, incorporated herein by reference. Other suitable polymers that may be blended with the polymers according to the present disclosure include those described in US2016 / 0237259A1. The combination with such functionalized styrene-butadiene rubbers in a tire composition with silica filler or carbonbased fillers or both may in particular improve dynamic properties, represented by tan d 0° C I tan d 60° C, as well as tensile properties, including S300, S300 / S100, tensile strength or elongation at break or a combination thereof. Typical mass ratios of polymers according to the present disclosure to functional polymers include ratios from 3 : 1 to 1 : 3.

[0061] Rubber auxiliaries

[0062] The rubber compounds containing the polybutadiene polymers according to the present disclosure may contain one or more further rubber auxiliaries as known in the art of rubber compounding and processing. Such further auxiliaries include but are not limited to curing reaction accelerators, antioxidants, heat stabilizers, light stabilizers, processing aids, plasticizers, tackifiers, blowing agents and colorants. Processing aids include organic acids, waxes and processing oils. Examples of oils include functionalized oils, particularly epoxidized or hydroxylated oils. Activators include triethanolamine, polyethylene glycol, hexanetriol. Colorants include dyes and pigments and may be organic or inorganic and include, for example, zinc white and titanium oxides.

[0063] The further rubber auxiliaries may be used in appropriate amounts depending on the intended use as known in the art. Examples of typical amounts of individual or total amounts of auxiliaries include from 0.1 wt. % to 50 wt. % based on the total weight of rubber in the compound.

[0064] For making rubber compounds a polybutadiene polymer composition according to the present disclosure can be blended with one or more of ingredients by means known in the art of rubber processing, for example by using rolls, internal mixers and mixing extruders. The fillers are preferably admixed to the solid polybutadiene polymer composition or to a mixture of it with other rubbers as known in the art, for example by using a kneader. Fillers may be added as solids, or as slurry or otherwise as known in the art.

[0065] Vulcanizates

[0066] Rubber vulcanizates are obtainable by subjecting the rubber compounds to curing, for example to one or more curing steps. Curing can be carried out as known in the art. Curing is commonly carried out at temperatures between 100 to 200° C, for example between 130 to 180° C. Curing may be carried out in molds under pressure. Typical pressures include pressures of 10 to 200 bar. Curing times and conditions depend on the actual composition of rubber compounds and the amounts and types of curatives and curable components. In the sense of the present invention, vulcanizates may also be called Mooney-jumped polymers which may be formed after a rection with sulphur compounds, such as sulphur chlorides.

[0067] Articles

[0068] The polymer compositions can be used to make articles. Typically, the articles comprise the polybutadiene polymer compositions according to the present disclosure in a cured form, for example, as result of one or more curing reactions. Suitable articles include tires or components of tires. Typical components of tires include inner liner, treads, undertreads, carcass, and the sidewalls. Other suitable articles include seals, for example O-rings, gaskets or component of seals. The compositions according to the present disclosure may be used as impact modifiers for thermoplastics including polystyrenes and styrene-acrylonitriles. The compositions may also be used for making golf balls or components thereof. The compositions may be used to make shaped articles selected from profiles, membranes, damping elements and hoses.

[0069] The articles may be obtained by subjecting a curable composition comprising the polymer according to the present disclosure to curing and shaping. The shaping step may take place during or after the curing step or also prior to curing step. A single curing and / or shaping step may be used or a plurality of curing and / or shaping steps may be used. Additional ingredients may be added to the compositions of the present disclosure as required for making the articles. Such articles comprise the polybutadiene polymer according to the present disclosure in a cured form.

[0070] In the following the present disclosure is further illustrated by specific embodiments and examples without, however, any intention to limit the present disclosure to these specific embodiments and examples.

[0071] Methods

[0072] Content of cis, trans and vinyl units: The content of vinyl, cis and trans units in the polymer can be determined by FT-IR spectrometry using the absorbances and absorbance ratios as described in the standard ISO 12965:2000(E).

[0073] Mooney viscosity.

[0074] The Mooney viscosity of the polymer can be determined according to the standard ASTM D1646 (1999) using a 1999 Alpha Technologies MV 2000 Mooney viscometer.

[0075] Mooney stress relaxation (MSR):

[0076] Mooney Stress Relaxation (MSR) can be determined in according to ASTM D 1646-00 at a temperature of 100°C.

[0077] Molecular weight and molecular weight distribution:

[0078] Molecular weight (number averaged molecular weight (Mn), the weight averaged molecular weight (Mw)) and the molecular weight distribution (MWD = Mw / Mn)) can be determined by gel permeation chromatography (GPC). A modular system from Agilent, Santa Clara, CA, USA can be used comprising an Agilent 1260 Refractive Index Detector, Agilent 1260 Variable Wavelength Detector, 1260 ALS autosampler, column oven (Agilent 1260 TCC), Agilent 1200 Degasser, Agilent 1100 Iso Pump and a column combination of 3 PLgel 10 pm Mixed B300x7.5 mm columns from Agilent. Tetra hydrofuran (THF) can be used as solvent. Polystyrene standards from PSS Polymer Standards Service GmbH (Mainz, Germany) can be used. The polymer samples dissolved in THF can be filtered through syringe filters (0.45 pm PTFE membranes, diameter 25 mm). The measurements can be conducted at 40 °C and with a flow rate of 1 mL / min.

[0079] Glass transition temperature:

[0080] The glass transition temperatures (Tg) can be determined by differential thermoanalysis (DTA, differential scanning calorimetry (DSC)) on a 2003 Perkin Elmer DSC-7 calorimeter. 10 mg to 12 mg of the polymer are placed on a DSC sample holder (standard aluminum pan) from Perkin Elmer. Two cooling / heating cycles are conducted and the Tg is determined in the second heating cycle. The first DSC cycle is conducted by first cooling the sample down to -100°C with liquid nitrogen and then heating it up to +150°C at a rate of 20 K / min. The second DSC cycle is commenced by cooling of the sample as soon as a sample temperature of +150°C has been reached at a cooling rate of about 320 K / min. In the second heating cycle, the sample is heated up again to +150°C at a heating rate of 20 K / min. The Tg is determined from the graph of the DSC curve of the second heating operation.

[0081] Content of polymer-bound sulfur:

[0082] 1 g polymer sample is cut into smaller pieces and extracted by Soxhlet extraction with 50 mL of acetone (> 99% purity) under reflux for 48 hours. After extraction the polymer is dried at 60 °C in a vacuum oven. The subsequent quantification of the sulfur amount (bound sulfur) is conducted via Combustion Ion Chromatography (CIC). CIC machines are commercially available, for example, from Thermo Fisher Scientific (for example Fisher Scientific GmbH, Schwerte, Germany). They typically have two coupled units: one is an automated digestion unit having an autosampler, a combustion unit (electric heater) and an absorption module. The second unit is an Ion Chromatography unit for quantification. For the measurement the polymer sample is weighed into a ceramic boat and is then pyrohydrolytically oxidized in an argonoxygen atmosphere. The analyte gases are absorbed in a hydrogen peroxide solution and automatically transferred to the ion chromatograph, where sulfur is measured as sulfate anion.

[0083] Branching degree (Delta delta, AS):

[0084] The branching degree can be determined on a SIS V50 Rubber Process Analyser (RPA) in frequency mode consisting of 20 frequencies (equidistant on a logarithmical scale) starting at 0.01 Hz to 40 Hz at a temperature of 100° C and an amplitude of 0.5°. Polyamide-6,6 foil can be used. After a pre-heating phase of 5 minutes, the measurement is performed with three pre-cycles and three measurement cycles per frequency. The Delta delta (A8) is the difference in phase angle delta at 0.1 and 100 rad / s.

[0085] Refractive index

[0086] The refractive index can be determined with a refractometer, for example a digital refractometer DR6000-T from A. Kruess Optronic GmbH, Hamburg, Germany, at the specified measuring temperature.

[0087] Cold flow:

[0088] The cold flow can be determined by measuring the amount of sample that is extruded through a die at a measuring temperature of 50°C. 1 .5 g of polymer sample was inserted into a test die having a diameter of 6.4 mm diameter and 3.2 mm length. The aperture of the die was closed and die a sample were adjusted to 50°C. Then the aperture of the die was opened and the sample in the die was subjected to a force of 12.9 N for 30 min for squeezing it through the aperture of the die. The sample that was squeezed out from the die was cut off and weighed. The cold flow was determined as the amount of sample pushed out from the die / measuring time of 30 minutes.

[0089] Examples

[0090] Examples 1-27

[0091] Polymer 1 was a substantially linear polybutadiene homopolymer (Mooney viscosity ML 1 +4 at 100°C of 63; cis content > 96%, 8A of 26). Polymer 2 was a substantially branched polybutadiene homopolymer (Mooney viscosity ML 1 +4 at 100°C of 63; cis content > 96%, SA of 14). Different extender oils and in various amounts of extender oils were blended with these polymers: a mineral oil (TDAE oil, VIVATEC 500 from Hansen&Rosenthal, Germany, Oil 1 , comparative examples), canola oil (Oil 2) and sunflower oil (Oil 3). The oil-extended polymers were prepared by dissolving the polymers in hexane at room temperature to prepare a solution having about 12 wt% polymer. The oils were mixed into the polymer solutions in the desired amounts and the solutions were stirred at room temperature for about 10 minutes before the solvent was removed by steam-stripping. The oil-extended polymers were dried in an oven at 50 °C overnight. The cold flow of the samples was measured at 50°C. The results with polymer 1 are shown in table

[0092] 1 , the results with polymer 2 are shown in table 2.

[0093] Table 1 : test series with polymer 1 .

[0094] Table 2: test series with polymer 2. ‘comparative

[0095] The results in table 1 show that the cold flow is reduced when using glyceride-based oils compared to mineral oils. The finding is surprising because the cold flow increases if the viscosity of the polymer decreases. The bio-oils had a lower viscosity than the mineral oil, therefore, one would have expected that the cold flow of the polymer extended with bio-based oils would be higher than for polymers extended with mineral oil. The opposite was observed.

[0096] The results in table 2 confirm the findings also for branched polymers. The cold flow of branched polymers is generally lower than that of linear polymers but is further reduced when using biobased oils compared to mineral oils.

[0097] Examples 28-33 (comparative)

[0098] In examples 28 to 33 the effect of the extender oil on the cold flow for different polybutadiene rubbers was investigated. Polymers 3 - 5 were blended with oils 1-3 as described above for examples 1-14 at a concentration of oil of 20 weight %. The ingredients used in the experiments are shown in table 3 and the results are show in table 4.

[0099] Table 3: ingredients used for examples 28-33. Table 4: cold flow measurements for comparative oil-extended polymers 28-33 compared with the cold flow of examples 8-10 and 22-24.

[0100] ‘comparative

[0101] The results in table 4 show that LiBR and SSBR polymers extended with the biooils instead of mineral oil did not show a reduced cold flow - contrary to the high-cis polybutadienes. LiBR was a branched polybutadiene homopolymer with a low cis-unit content (< 50%). SSBR was a copolymer of styrene and butadiene with a styrene content of about 20 wt % used both in linear and non-linear architecture. The LiBR and SSBR’s had a higher cold flow when they were extended with biooil than with mineral oil.

Claims

CLAIMS1. A polymer composition comprising at least 95% by weight, based on the total weight of the composition, of at least one curable, oil-extended polybutadiene polymer obtained by blending a polybutadiene polymer with at least one oil, wherein the polybutadiene polymer (i) has a 1 ,4-cis content of at least 92 %, (ii) has a AS of at least 25° and the amount of oil is from 1 % up to 20% by weight, based on the total weight of the polymer composition, or wherein the polybutadiene polymer has a AS of less than 25°, preferably less than 20°, and the amount of oil is from 1 % to 50% by weight, preferably from 1 1 % up to 35% by weight or up to 30% by weight, based on the total weight of the polymer composition and (iii) comprises at least 90 % by weight, preferably at least 95% by weight, based on the weight of the polymer, of units derived from butadiene, wherein the oil comprises at least one ester of a glycerol and at least one carboxylic acid.

2. The polymer composition according to claiml wherein the polybutadiene polymer has a 1 ,4-cis-content of at least 96%.

3. The polymer composition according to claim 1 or 2 wherein the extender oil comprises at least one ester of glycerol and at least one C6- C36 carboxylic acid which may be linear or branched and which may be saturated or unsaturated.

4. The polymer composition according to any one of the preceding claims wherein the oil is or comprises a vegetable oil.

5. The polymer composition according to any one of the preceding claims wherein the oil has a refractive index of < 1 ,48 at 10 °C as determined according to the method specified in the experimental section.

6. The polymer composition according to any one of the preceding claims having a Mooney viscosity ML 1 +4 at 100°C of from 20 to 50 units.

7. The polymer composition according to any one of the preceding claims wherein the polybutadiene polymer used for making the oil-extended polymer has a Mooney viscosity ML 1+4 at 100°C of greater than 50 and up to 120 units.

8. The polymer composition according to any one of the preceding claims comprising a first and a second anti-ageing stabilizer, wherein the first anti-ageing stabilizer is a phenolic compound comprising at least one phenol ring having at least one thia-alkylsubstituent at the phenol ring and wherein the second stabilizer is a phenolic comprising at least one tert-butanol substituent at the phenolic ring.

9. The polymer composition according to any one of the preceding claims having a cold flow of less than 20g / 10 min at 50°C, preferably less than 15 g / 10 min and, preferably, a AS of at least 25°, preferably at least 20°.

10. The polymer composition according to any one of the preceding claims having a cold flow of less than 10g / 10 min at 50°C, preferably less than 5g / 10 min at 50°C and, preferably, having a AS of less than 20°, preferably less than 15°.

11. A method for preparing a polymer composition according to any one of the preceding claims comprising blending at least one oil with a curable polybutadiene polymer having a 1 ,4-cis content of at least 92 % and comprising at least 90% by weight, preferably at least 95% by weight, based on the weight of the polymer, of units derived from butadiene with at least one oil that comprises at least one ester of a glycerol and at least one carboxylic acid.

12. The method of claim 11 wherein the blending is carried out in a solution of the polymer in at least one solvent, and wherein the method further comprises removing the solvent after the blending.

13. The method of any one of claims 11 and 12, where the method is a method for reducing the cold flow of an oil-extended polymer.

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