Conjugated diene-based polymer, polymer composition, crosslinked product, and tire

Abstract

To provide a conjugated diene-based polymer which can give a crosslinked product exhibiting good rolling resistance and is excellent in filler dispersibility.SOLUTION: A conjugated diene-based polymer includes, with respect to all repeating units, 50 to 99.5% by mass of a repeating unit (a) derived from a conjugated diene compound, 0 to 40% by mass of a repeating unit (b) derived from an aromatic vinyl compound, and 0.5 to 30% by mass of a repeating unit (c) having a partial structure represented by the following formula (1): In Formula (1), n is an integer of 4 to 200, R1 represents a hydrocarbylene group having 1 to 8 carbon atoms, R2 represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and * represents a bond.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a conjugated diene-based polymer, a polymer composition, a crosslinked product, and a tire. [Background technology]

[0002] Conjugated diene polymers such as styrene butadiene rubber (SBR) have various excellent properties such as heat resistance, abrasion resistance, mechanical strength, and moldability, and are therefore widely used in various rubber products such as pneumatic tires, anti-vibration rubber, and hoses. Conjugated diene polymers are generally produced by emulsion polymerization or solution polymerization. Patent Document 1 discloses a diene rubber containing butadiene units, styrene units, and vinyl monomer units having a quaternized tertiary amino group as a conjugated diene polymer produced by emulsion polymerization.

[0003] It is known that in rubber compositions used in the manufacture of pneumatic tire treads, sidewalls, etc., fillers such as carbon black and silica are blended as reinforcing fillers together with conjugated diene polymers in order to improve the durability and abrasion resistance of the products. Furthermore, conjugated diene polymers modified with silicon- or nitrogen-containing compounds have been used in the past to increase the affinity between the conjugated diene polymers and fillers (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-182996 [Patent Document 2] International Publication No. 2008 / 123164 Summary of the Invention [Problem to be solved by the invention]

[0005] In response to growing environmental awareness among consumers, there is a demand for further reductions in the rolling resistance of rubber materials and for fuel economy in order to conserve resources. In addition to fuel economy, rubber materials with high filler dispersion are required from the perspective of further improving various properties such as strength and abrasion resistance.

[0006] The present invention has been made in view of the above problems, and a main object of the present invention is to provide a conjugated diene polymer which can give a crosslinked product exhibiting good rolling resistance and which has excellent filler dispersibility. [Means for solving the problem]

[0007] According to the present invention, there are provided the following conjugated diene-based polymer, polymer composition, crosslinked product, and tire.

[0008] [1] A conjugated diene polymer having, relative to all repeating units, 50 to 99.5 mass% of repeating units (a) derived from a conjugated diene compound, 0 to 40 mass% of repeating units (b) derived from an aromatic vinyl compound, and 0.5 to 30 mass% of repeating units (c) having a partial structure represented by the following formula (1): [ka] (In formula (1), n ​​is an integer of 4 to 200, and R 1 represents a hydrocarbylene group having 1 to 8 carbon atoms, and R 2 represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and * represents a bond. [2] The conjugated diene polymer according to [1], which has a weight average molecular weight (Mw) of 50,000 to 2,000,000 in terms of polystyrene as measured by gel permeation chromatography. [3] A polymer composition comprising the conjugated diene polymer according to [1] or [2] and a crosslinking agent. [4] The polymer composition according to [3], further containing a filler. [5] A crosslinked product obtained by curing the polymer composition according to [3] or [4]. [6] A tire in which the crosslinked body according to [5] is used at least in part. [Effects of the Invention]

[0009] The conjugated diene polymer of the present invention can provide a crosslinked product that exhibits good rolling resistance. The conjugated diene polymer of the present invention also has excellent filler dispersibility. DETAILED DESCRIPTION OF THE INVENTION

[0010] Matters related to the implementation of the present invention will be explained in detail below. In this specification, a numerical range described using "to" means that the numerical values ​​described before and after "to" are included as the lower and upper limits. A "repeating unit" refers to a unit that mainly constitutes the main chain structure, and at least two or more units are included in the main chain structure. A repeating unit is typically a monomer unit. Note that a unit obtained by reacting a monomer unit having a reactive group with a compound having a functional group capable of reacting with the reactive group is also included in the "repeating unit".

[0011] <Polymer> The conjugated diene polymer of the present disclosure contains, relative to all repeating units, 50 to 99.5 mass% of repeating units (a) derived from a conjugated diene compound, 0 to 40 mass% of repeating units (b) derived from an aromatic vinyl compound, and 0.5 to 30 mass% of repeating units (c) having a partial structure represented by the following formula (1): Hereinafter, for convenience, the conjugated diene polymer will also be referred to as "polymer (P)." [ka] (In formula (1), n ​​is an integer of 4 to 200, and R 1 represents a hydrocarbylene group having 1 to 8 carbon atoms, and R 2 represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and * represents a bond.

[0012] <Polymer (P)> Repeating unit (a) The repeating unit (a) is a structural unit derived from a conjugated diene compound. Examples of conjugated diene compounds include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, and 2-chloro-1,3-butadiene. Among these, 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene are preferred because they can improve various properties required for tire applications, and 1,3-butadiene is particularly preferred because it can improve processability and rolling resistance in a well-balanced manner. The conjugated diene compound constituting the repeating unit (a) may be one type or two or more types.

[0013] In the polymer (P), the content of the repeating unit (a) is 50 to 99.5% by mass relative to the total amount of repeating units constituting the polymer (P) (hereinafter also referred to as "total repeating units"). If the content of the repeating unit (a) is less than 50% by mass, the processability and rolling resistance tend to be insufficient when applied to tires. On the other hand, if the content of the repeating unit (a) exceeds 99.5% by mass, the content of the repeating unit (c) in the polymer (P) is low, and the effect of improving rolling resistance and filler dispersibility by introducing the repeating unit (c) cannot be fully obtained. Therefore, the content of the repeating unit (a) is preferably 55% by mass or more, more preferably 60% by mass or more, and even more preferably 65% ​​by mass or more, relative to the total repeating units of the polymer (P). On the other hand, the content of the repeating unit (a) is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, relative to the total repeating units of the polymer (P).

[0014] Repeating unit (b) The repeating unit (b) is a structural unit derived from an aromatic vinyl compound. Examples of aromatic vinyl compounds include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, t-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, vinylxylene, vinylnaphthalene, vinylpyridine, and diphenylethylene. Among these, styrene and α-methylstyrene are preferred as aromatic vinyl compounds because of their high effect of increasing the strength of the polymer (rubber). The aromatic vinyl compounds constituting the repeating unit (b) may be one type or two or more types.

[0015] The content of repeating units (b) in polymer (P) is 0 to 40% by mass based on the total repeating units of polymer (P). If the content of repeating units (b) exceeds 40% by mass, the rolling resistance tends to be insufficient when crosslinked. Therefore, the content of repeating units (b) is preferably 37% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, based on the total repeating units of polymer (P). Polymer (P) may be a polymer that does not have repeating units (b) (i.e., the content of repeating units (b) is 0% by mass). By copolymerizing polymer (P) with a conjugated diene compound unit and an aromatic vinyl compound unit, the strength of the polymer can be further increased, which is preferable. The content of repeating units (b) is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on the total repeating units of polymer (P). The content of repeating units (b) in the polymer is 1 This is a value measured by a H-NMR device.

[0016] Repeating unit (c) The repeating unit (c) has a partial structure represented by the following formula (1). [ka] (In formula (1), n ​​is an integer of 4 to 200, and R 1 represents a hydrocarbylene group having 1 to 8 carbon atoms, and R 2 represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and * represents a bond.

[0017] In the above formula (1), R 1 Examples of the hydrocarbylene group having 1 to 8 carbon atoms represented by the formula (I) include a linear or branched alkanediyl group having 1 to 8 carbon atoms, a cycloalkylene group having 5 to 8 carbon atoms, an arylene group having 6 to 8 carbon atoms, and an aralkylene group having 7 or 8 carbon atoms. R 2 Examples of the hydrocarbyl group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 5 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms.

[0018] R is advantageous in that it prevents restriction of the movement of the partial structure (i.e., side chain) represented by the above formula (1), thereby further enhancing the effect of improving the rolling resistance of the crosslinked body obtained using the polymer (P). 1 is preferably a linear or branched alkanediyl group having 1 to 8 carbon atoms. 2 is preferably a hydrogen atom or a linear or branched alkyl group having 1 to 20 carbon atoms, more preferably a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms.

[0019] In addition, R 1 , R 2 When R has a chain hydrocarbon structure, the distance between ether bonds can be flexibly changed by bond rotation, making it easier to obtain a distance suitable for interaction with the reinforcing filler. 1 , R 2It is believed that this tire exhibits better rolling resistance and filler dispersion than tires having an aromatic hydrocarbon structure.

[0020] The partial structure represented by the formula (1) may be bonded directly to the main chain of the polymer, or may be bonded via a divalent linking group. When the partial structure represented by the formula (1) is bonded to the main chain of the polymer via a divalent linking group, examples of the divalent linking group include -O-, -S-, -CO-O-, -CO-S-, -CO-NH-, and -O-(CH2). r -, -S-(CH2) r -, -CO-O-(CH2) r -, -CO-S-(CH2) r -, -CO-NH-(CH2) r -, -Ph-X 1 In this case, r is an integer of 1 to 8, Ph is a phenylene group, and X 1 is a single bond or an alkanediyl group having 1 to 8 carbon atoms.

[0021] In terms of the ease of synthesizing the polymer (P) and the ease of adjusting the amount of repeating unit (c) introduced into the polymer (P), the repeating unit (c) is preferably a structural unit derived from a monomer having a partial structure represented by the above formula (1) (hereinafter also referred to as "monomer (mc)"). The molecular weight of the monomer (mc) is preferably 200 to 20,000.

[0022] Specific examples of the monomer (mc) include polyalkylene glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate and polypropylene glycol mono(meth)acrylate; and alkoxypolyalkylene glycol (meth)acrylates such as methoxytetraethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate. The monomer (mc) constituting the repeating unit (c) may be one type or two or more types. In this specification, "(meth)acrylic" means to include acrylic and methacrylic.

[0023] The content of the repeating unit (c) in the polymer (P) is 0.5 to 30% by mass relative to the total repeating units of the polymer (P). If the content of the repeating unit (c) is less than 0.5% by mass, the effect of introducing the repeating unit (c) is less likely to be achieved, and the rolling resistance and filler dispersibility tend not to be sufficiently improved. If the content of the repeating unit (c) exceeds 30% by mass, rubber elasticity tends not to be exhibited. Therefore, the content of the repeating unit (c) is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and even more preferably 2.0% by mass or more, relative to the total repeating units of the polymer (P). Furthermore, the content of the repeating unit (c) is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, relative to the total repeating units of the polymer (P). The content of the structural unit (c) in the polymer is 1 This is a value measured by a H-NMR device.

[0024] The polymer (P) may further contain, as repeating units constituting the polymer (P), repeating units derived from compounds other than the conjugated diene compound, the aromatic vinyl compound, and the monomer (mc) (hereinafter also referred to as "other monomers"). Examples of other monomers include acrylonitrile, methyl (meth)acrylate, and ethyl (meth)acrylate. In the polymer (P), the content of repeating units derived from other monomers is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the total repeating units of the polymer (P).

[0025] The polymer (P) is preferably a random copolymer mainly composed of random copolymerized portions in which the distribution of a conjugated diene compound and an aromatic vinyl compound is irregular, in order to achieve a well-balanced improvement in hysteresis loss at low and high temperatures. When the polymer (P) is a random copolymer, the polymer (P) may further have block portions composed of a conjugated diene compound. The conjugated diene compound constituting the block portions is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on the total amount of conjugated diene compound units constituting the polymer (P). In terms of high living property in anionic polymerization, the polymer (P) is preferably a copolymer containing 1,3-butadiene, styrene, and a monomer (mc) in its monomer composition.

[0026] <Method for producing polymer (P)> The polymerization method for producing the polymer (P) is not particularly limited, and examples thereof include bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. Of these polymerization methods, emulsion polymerization, which uses an aqueous medium as the polymerization medium, is preferred. Known methods can be applied to emulsion polymerization. Specifically, for example, a method can be used in which a monomer is dispersed in an aqueous medium (preferably water) using an emulsifier, polymerized in the presence of a polymerization initiator, and, after a desired polymerization conversion rate is reached, a polymerization terminator is added to terminate the polymerization.

[0027] In producing the polymer (P), a monomer mixture containing a conjugated diene compound and a monomer (mc) as monomers and an aromatic vinyl compound as an optional component is preferably used.

[0028] Examples of emulsifiers include anionic surfactants, nonionic surfactants, and amphoteric surfactants. To obtain a stable emulsion dispersion, anionic surfactants are typically used. Examples of anionic surfactants include salts of long-chain fatty acids having 10 or more carbon atoms, rosinate salts, and linear alkyl group-containing benzenesulfonates. Specific examples include potassium salts and sodium salts of capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, octylbenzenesulfonic acid, dodecylbenzenesulfonic acid, dodecyldiphenyloxidesulfonic acid, and dodecyldiphenyletherdisulfonic acid. Fluorine-based surfactants can also be used. The emulsifiers can be used alone or in combination of two or more.

[0029] The polymerization initiator may be a radical polymerization initiator commonly used in emulsion polymerization. Examples of the polymerization initiator include organic peroxides such as benzoyl peroxide, lauroyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, pinane hydroperoxide, paramenthane hydroperoxide, trimethylbicycloheptyl hydroperoxide, di-tert-butyl peroxide, and dicumyl peroxide. Diazo compounds such as azobisisobutyronitrile, inorganic peroxides such as potassium persulfate, and redox catalysts such as combinations of these peroxides with ferrous sulfate may also be used. The polymerization initiator may be used alone or in combination of two or more. The amount of the polymerization initiator used is typically 0.01 part by mass or more, preferably 0.05 to 1.0 part by mass, per 100 parts by mass of the total amount of monomers used in the polymerization.

[0030] During polymerization, a chain transfer agent may be used to adjust the molecular weight of the polymer (P). Examples of the chain transfer agent include alkyl mercaptans such as tert-dodecyl mercaptan and n-dodecyl mercaptan, carbon tetrachloride, thioglycols, diterpenes, terpinolene, γ-terpinenes, and α-methylstyrene dimer. The chain transfer agent may be used alone or in combination of two or more. The amount of the chain transfer agent used is usually 0.05 parts by mass or more, and preferably 0.1 to 15 parts by mass, per 100 parts by mass of the total amount of monomers used in polymerization.

[0031] During emulsion polymerization, additives may be added as appropriate, such as chelating agents such as sodium ethylenediaminetetraacetate, glycine, and alanine; electrolytes such as potassium chloride, sodium phosphate, potassium phosphate, and potassium sulfate; activators such as sodium formaldehyde sulfoxylate and ferrous sulfate; pH adjusters such as ammonia, sodium hydroxide, and potassium hydroxide; and oxygen scavengers such as styrenated phenol, hindered phenol, imidazoles, paraphenylenediamine, and sodium hydrosulfite.

[0032] In producing the polymer (P) by emulsion polymerization, the polymerization method may be continuous or batchwise. The polymerization can be carried out using a reactor from which oxygen has been removed, usually at a temperature of 0 to 100°C, preferably 0 to 80°C. The polymerization time is preferably 1 to 24 hours, more preferably 2 to 12 hours. During the reaction, the operating conditions such as temperature and stirring can be appropriately changed, and a portion of the monomers can be added to the reaction vessel during the polymerization.

[0033] In the polymerization reaction, gelation may occur if the polymerization conversion rate becomes too high. Therefore, it is preferable to keep the polymerization conversion rate at 85% or less, and more preferably at 80% or less. It is particularly preferable to terminate the polymerization when the polymerization conversion rate is in the range of 30 to 70%. The polymerization can be terminated by adding a polymerization terminator when the desired polymerization conversion rate is reached. Examples of the polymerization terminator include hydroxylamine compounds such as hydroxylamine and N,N-diethylhydroxylamine; and quinone compounds such as hydroquinone. After the polymerization is terminated, if necessary, unreacted monomers can be removed from the reaction system by a method such as steam distillation to obtain a latex in which the polymer (P) is dispersed in the dispersion medium.

[0034] The weight average molecular weight (Mw) of the polymer (P) obtained by the above polymerization is preferably 5.0×10 4 or more. Mw is 5.0 × 10 4 When the Mw of the polymer (P) is 6.0×10 or more, the crosslinked product (specifically, crosslinked rubber) tends to have sufficiently high shape stability, tensile strength, and abrasion resistance. 4 More preferably, it is 7.0×10 4 The Mw of the polymer (P) is preferably 2.0×10 6 Mw is 2.0×10 6 When the Mw of the polymer (P) is 1.5×10 or less, the processability of the polymer composition containing the polymer (P) tends to be sufficiently ensured. 6 and more preferably 1.0 × 10 6 The following is the result.

[0035] The preferred range of Mw of the polymer (P) can be determined by appropriately selecting the above-mentioned preferred upper and lower limits. The preferred range of Mw of the polymer (P) is 5.0 × 10 4 ~2.0×10 6 and a more preferable range is 6.0×10 4 ~1.5×10 6 and a more preferable range is 7.0×10 4 ~1.0×10 6is.

[0036] The molecular weight distribution (Mw / Mn) of the polymer (P), which is the ratio of Mw to the number average molecular weight (Mn), is preferably 1.5 or more, more preferably 1.8 or more, from the viewpoint of ease of production. Furthermore, from the viewpoint of improving various performances of the crosslinked product, the molecular weight distribution (Mw / Mn) is preferably 8.0 or less, more preferably 7.0 or less, and even more preferably 6.0 or less. In this specification, the Mw and Mn of the polymer (P) are polystyrene-equivalent values ​​measured by gel permeation chromatography (GPC).

[0037] The vinyl bond content of the polymer (P) is preferably 5 to 25% by mass. A vinyl bond content of 5% by mass or more is preferred because it allows for sufficiently high wet grip properties when crosslinked. Furthermore, a vinyl bond content of 25% by mass or less is preferred because it allows for a crosslinked product exhibiting good rolling resistance. The vinyl bond content of the polymer (P) is more preferably 7% by mass or more, even more preferably 10% by mass or more, and even more preferably 13% by mass or more. Furthermore, the vinyl bond content of the polymer (P) is more preferably 22% by mass or less, even more preferably 20% by mass or less, and even more preferably 18% by mass or less. In this specification, the "vinyl bond content" is a value indicating the content ratio of repeating units having 1,2-bonds to the total amount of repeating units derived from butadiene in the polymer (P), 1 This is a value measured by a H-NMR device.

[0038] In addition to the above, the polymer (P) can also be produced by copolymerizing a conjugated diene compound and, if necessary, an aromatic vinyl compound with a monomer having a reactive functional group (such as (meth)acrylic acid) to obtain a copolymer, and then reacting the copolymer with a compound having a group reactive with the reactive functional group and having a hydroxyl group on the adjacent carbon.

[0039] <Polymer composition> By blending a crosslinking agent or the like with the polymer (P), it is possible to obtain a polymer composition for producing a crosslinked product (i.e., crosslinked rubber) used in the production of tires, etc. The polymer composition may contain a filler, other rubber components, etc.

[0040] (Crosslinking agent) Examples of crosslinking agents contained in the polymer composition include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, alkylphenol resins having a methylol group, etc., and sulfur is usually used. The amount of sulfur blended is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the total amount of rubber components contained in the polymer composition.

[0041] (filler) The filler is used as a reinforcing filler to increase the strength of the crosslinked body obtained by crosslinking the polymer (P). Examples of the filler include silica; carbon black; an inorganic compound represented by the following formula (2) (hereinafter also referred to as "inorganic compound (M)"); reinforcing fibers (e.g., inorganic fibers such as glass fiber and carbon fiber; organic fibers such as nylon and polyester); etc. Among these, the filler is preferably at least one selected from the group consisting of silica, carbon black, and the inorganic compound (M). nM 1 mSiO k iH2O...(2) (In formula (2), M 1 is at least one selected from the group consisting of a specific metal, which is any one of aluminum, magnesium, titanium, and calcium, an oxide of the specific metal, and a hydroxide of the specific metal. n is an integer of 1 to 5, m is an integer of 0 to 10, k is an integer of 2 to 10, and i is an integer of 0 to 10.

[0042] Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. Among these, wet silica is particularly preferred from the viewpoint of improving the fracture properties of crosslinked rubber and achieving both wet grip performance and rolling resistance. Highly dispersible silica is also preferred from the viewpoint of improving dispersibility in the polymer composition and improving physical properties and processability. Silica may be used alone or in combination of two or more. Examples of carbon black include, but are not limited to, GPF, FEF, HAF, ISAF, and SAF. Furthermore, the polymer composition may further contain various reinforcing fillers such as clay and calcium carbonate in addition to silica and carbon black as inorganic fillers.

[0043] Specific examples of the inorganic compound (M) include compounds in which the specific metal is aluminum, such as aluminum oxide, alumina monohydrate, aluminum hydroxide, aluminum carbonate, aluminum silicate, and calcium aluminum oxide (Al2O3·CaO·2SiO4, etc.); compounds in which the specific metal is magnesium, such as magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium silicate, calcium magnesium silicate (CaMgSiO4), and talc; compounds in which the specific metal is titanium, such as titanium oxide; and compounds in which the specific metal is calcium, such as calcium oxide, calcium hydroxide, calcium carbonate, and calcium silicate.

[0044] As the filler, one of silica, carbon black, and inorganic compound (M) may be used alone, or two or more of these may be used in combination. The polymer composition preferably contains silica as a filler together with the polymer (P), in view of its high effect of improving tire properties when combined with a conjugated diene polymer. Among these, wet silica, dry silica, and colloidal silica are preferably used. When a filler is incorporated, the amount of filler incorporated in the polymer composition (the total amount when two or more types are contained) is preferably 25 to 130 parts by mass, more preferably 30 to 110 parts by mass, per 100 parts by mass of the total amount of rubber components contained in the polymer composition.

[0045] (Other rubber components) The polymer composition may further contain a rubber component (hereinafter also referred to as "other rubber component") different from the polymer (P). In this specification, "rubber component" refers to a polymer that can be cured to give a cured product exhibiting rubber elasticity. The cured product exhibits the property of undergoing large deformation under small force at room temperature (for example, deformation that stretches to more than twice its original size when stretched at room temperature), and rapidly returning to almost its original shape when the force is removed.

[0046] The other rubber component may be a polymer that does not have at least one of the repeating unit (a) and the repeating unit (c), and its type is not particularly limited. Examples of the other rubber component include butadiene rubber (BR, such as high-cis BR having 90% or more cis-1,4 bonds), styrene-butadiene rubber (SBR), natural rubber (NR), isoprene rubber (IR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and modified SBR (such as nitrogen-containing SBR and terminal-modified SBR). The amount of the other rubber component is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, based on 100 parts by mass of the total amount of the rubber components (polymer (P) and other rubber components) contained in the polymer composition.

[0047] In addition to the components described above, the polymer composition may contain various additives that are generally used in polymer compositions for producing crosslinked products (i.e., crosslinked rubber), such as antioxidants, zinc oxide, stearic acid, softeners, vulcanization accelerators, silane coupling agents, compatibilizers, vulcanization aids, process oils, processing aids, scorch inhibitors, etc. The amounts of these additives added may be appropriately selected depending on the various components, as long as they do not impair the effects of the present invention.

[0048] <Production of polymer composition and crosslinked product> The polymer composition of the present invention can be produced by mixing (specifically kneading) the rubber component and other components to be blended as necessary using a kneader such as an open kneader (e.g., a roll) or an internal kneader (e.g., a Banbury mixer).

[0049] In the kneading step, first, a rubber component containing the polymer (P) and additives other than the vulcanization compounding agents (crosslinking agent, vulcanization accelerator, vulcanization aid) (hereinafter also referred to as "first additives") are melt-kneaded using a kneader (first step). The first additive preferably contains at least a filler (specifically, a reinforcing filler). The kneading temperature in the first step is appropriately set depending on the melting point, glass transition point, etc. of the rubber component. This melt-kneading allows the first additive to be mixed with the rubber component, thereby sufficiently achieving effects such as increasing the strength of the rubber product after vulcanization, improving the kneading processability of the polymer composition, and preventing deterioration of the rubber component due to radicals generated during kneading.

[0050] Next, the kneaded product obtained in the first step is returned to room temperature as necessary, and then vulcanization-related compounding agents are added to the kneaded product, followed by melt-kneading using a kneader (second step). The polymer composition obtained in the second step is molded and processed, and then crosslinked (vulcanized) to obtain a crosslinked product (vulcanized rubber).

[0051] <Cross-linked body and tire> The crosslinked product obtained using the polymer composition of the present invention can be applied to various rubber products. Specific examples of various rubber products include tire applications such as tire treads, undertreads, carcasses, sidewalls, and bead portions; sealing materials such as packings, gaskets, weatherstrips, and O-rings; interior and exterior covering materials for various vehicles such as automobiles, ships, aircraft, and railways; building materials; vibration-proof rubbers for industrial machinery and equipment; diaphragms, rolls, various hoses and hose covers such as radiator hoses and air hoses; belts such as power transmission belts; linings; dust boots; medical device materials; fenders; insulating materials for electric wires; and other industrial products.

[0052] The polymer (P) has high strength and is resistant to deterioration in strength due to heat. Therefore, the polymer (P) is particularly suitable as a material for one or both of the tread and sidewall of a tire. The polymer (P) is preferable in that the high strength of the rubber material allows the tire components to be made thinner, thereby contributing to resource conservation.

[0053] Tires can be manufactured by conventional methods, for example, by mixing the polymer (P) and other components as needed in a kneader, forming a sheet, and then arranging the sheet in a predetermined position and vulcanizing the sheet in a conventional manner to form at least one of a tread and a sidewall, thereby obtaining a pneumatic tire. [Example]

[0054] The present invention will be described in detail below based on examples, but is not limited to these examples. In the examples and comparative examples, "parts" and "%" are by mass unless otherwise specified. The methods for measuring various physical properties of the polymer are shown below.

[0055] [Repeating unit (c) content (%)], [bonded styrene content (%)] and [vinyl bond content (%)]: 400MHz 1The integral ratio was determined using a H-NMR apparatus. The integral ratio between 6.0 and 7.5 ppm was defined as A, the integral ratio between 5.1 and 6.0 ppm as B, the integral ratio between 4.5 and 5.1 ppm as C, and the integral ratio between 3.4 and 4.3 ppm as X. The number of hydrogen atoms bonded to the carbon atom adjacent to the oxygen atom was defined as m, and the molecular weight of the monomer (mc) constituting the repeating unit (c) was defined as M. The values ​​were calculated according to the following formulas. [Repeating unit (c) content (%)] = (20X / m × M) / (4A × 104) + 5(2B + C) × 54 + (20X / m) × M} × 100 [Bound styrene content (%)] = (4A × 104) / {(4A × 104) + 5(2B + C) × 54 + (20X / n) × M} × 100 [Vinyl bond content (%)] = 2C / (2C+B) x 100

[0056] [Weight average molecular weight] and [molecular weight distribution]: Using a gel permeation chromatograph (HLC-8320GPC (trade name), manufactured by Tosoh Corporation), the weight average molecular weight and molecular weight distribution were determined in terms of polystyrene from the retention time of a GPC curve obtained under the following measurement conditions. (Measurement conditions) Column: 2 pieces of "GMHXL" (manufactured by Tosoh Corporation) Column temperature: 40°C Mobile phase: tetrahydrofuran Flow rate; 0.4mL / min Sample concentration: 10mg / 20mL

[0057] 1. Synthesis of conjugated diene polymers [Synthesis Example 1: Synthesis of Conjugated Diene Polymer A] A 5 L reactor with a nitrogen-purged atmosphere was charged with 2.0 L of water, 32 g of sodium dodecyl diphenyl ether disulfonate, 0.36 g of potassium chloride, and 0.45 g of ethylenediaminetetraacetic acid sodium salt (chelating agent). Subsequently, 34 mL of water containing 0.56 g of ethylenediaminetetraacetic acid sodium salt (chelating agent), 0.23 g of ferrous sulfate, and 0.90 g of sodium methanesulfonate, 0.90 g of tert-dodecyl mercaptan, 633 g of 1,3-butadiene, 233 g of styrene, and 38 g of poly(ethylene glycol) methyl ether methacrylate (Mn≒2,000), was added. The contents were stirred at 330 rpm, and the temperature of the reactor contents was adjusted to 10°C. Then, 0.99 g of pinane hydroperoxide was added to initiate polymerization. The polymerization was carried out under temperature control (10°C). When the polymerization conversion rate reached 70%, 87.1 mL of a 6.2% aqueous solution of N,N-diethylhydroxylamine was added to terminate the polymerization reaction. After reducing the pressure to -0.1 MPa in a stripping tank, the temperature was raised to 60°C and stripping was carried out for 30 minutes to remove residual monomers. Next, 95 g of calcium chloride was added and dissolved in 9.15 L of hot water at 50°C, and the latex obtained by the above polymerization was added to the aqueous solution to coagulate the rubber component. Thereafter, the mixture was washed with water at 50°C, 50°C, and 20°C in that order, and the rubber was dried with a roll adjusted to 130°C to obtain a conjugated diene polymer A. The obtained conjugated diene polymer A was measured for bound styrene content, vinyl bond content, repeating unit (C) content, weight average molecular weight, and molecular weight distribution. The measurement results are shown in Table 1. The bound styrene content in Table 1 corresponds to the content of repeating unit (b), and the value obtained by subtracting the total amount of bound styrene content and repeating unit (c) content from 100 corresponds to the content of repeating unit (a). The content of repeating unit (a) in this conjugated diene polymer A was 72.5% by mass.

[0058] [Synthesis Example 2: Synthesis of Conjugated Diene Polymer B] Conjugated diene polymer B was obtained in the same manner as in Synthesis Example 1, except that poly(ethylene glycol) methyl ether methacrylate (Mn≈2,000) in the polymerization recipe was changed to poly(ethylene glycol) methyl ether methacrylate (Mn≈1,000).

[0059] [Synthesis Example 3: Synthesis of Conjugated Diene Polymer C] Conjugated diene polymer C was obtained in the same manner as in Synthesis Example 1, except that poly(ethylene glycol) methyl ether methacrylate (Mn≈2,000) in the polymerization recipe was changed to poly(ethylene glycol) methyl ether methacrylate (Mn≈500).

[0060] [Synthesis Example 4: Synthesis of Conjugated Diene Polymer D] Conjugated diene polymer D was obtained in the same manner as in Synthesis Example 1, except that the amount of 1,3-butadiene in the polymerization recipe was changed to 665 g and the amount of poly(ethylene glycol) methyl ether methacrylate (Mn≈2,000) was changed to 5 g.

[0061] [Synthesis Example 5: Synthesis of Conjugated Diene Polymer E] Conjugated diene polymer E was obtained in the same manner as in Synthesis Example 1, except that the amount of 1,3-butadiene in the polymerization recipe was changed to 544 g and the amount of poly(ethylene glycol) methyl ether methacrylate (Mn≈2,000) was changed to 126 g.

[0062] [Synthesis Example 6: Synthesis of conjugated diene polymer F] Conjugated diene polymer F was obtained in the same manner as in Synthesis Example 1, except that the amount of 1,3-butadiene in the polymerization recipe was changed to 454 g and the amount of poly(ethylene glycol) methyl ether methacrylate (Mn≈2,000) was changed to 216 g.

[0063] [Synthesis Example 7: Synthesis of conjugated diene polymer G] The reaction was carried out in the same manner as in Synthesis Example 1, except that the amount of 1,3-butadiene in the polymerization recipe was changed to 671 g and poly(ethylene glycol) methyl ether methacrylate (Mn≒2,000) was not used, to obtain an unmodified conjugated diene polymer G.

[0064] [Synthesis Example 8: Synthesis of conjugated diene polymer H] Conjugated diene polymer H was obtained in the same manner as in Synthesis Example 1, except that the amount of 1,3-butadiene in the polymerization recipe was changed to 668 g and the amount of poly(ethylene glycol) methyl ether methacrylate (Mn≈2,000) was changed to 3 g.

[0065] [Synthesis Example 9: Synthesis of conjugated diene polymer I] A 5 L autoclave reactor purged with nitrogen was charged with 2250 g of cyclohexane, 0.15 g of 2,2-di(tetrahydrofuryl)propane as a vinyl content adjuster (randomizer), and 180 g of styrene and 180 g of 1,3-butadiene as monomers. After adjusting the temperature of the reactor contents to 20°C, 3.30 mmol of n-butyllithium was added as a polymerization initiator to initiate polymerization. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 75°C. After the polymerization conversion rate reached 99%, 90 g of 1,3-butadiene was added as an additional monomer over 5 minutes, followed by the addition of 0.69 mmol of methoxypolyethylene glycol glycidyl ether (Mn≒1000) as a modifier, and the reaction was continued for 15 minutes. To the resulting polymer solution, 3.96 g of 2,6-di-tert-butyl-p-cresol was added, followed by steam stripping to remove the solvent, and drying with a heated roll adjusted to 110°C to obtain a conjugated diene polymer I.

[0066] 2. Preparation and evaluation of polymer compositions and crosslinked products [Examples 1 to 6 and Comparative Examples 1 to 3] Using each of the conjugated diene polymers A to I produced above, the components were blended according to the formulation shown in Table 1, and the blended mixture was kneaded to produce polymer compositions. Kneading was carried out as follows. Using a plastomill (capacity: 250 mL) equipped with a temperature control device, polymers (A to H), a vulcanization accelerator, and sulfur were blended and kneaded at a filling rate of 72% and a rotation speed of 60 rpm. The obtained polymer compositions were molded and vulcanized in a vulcanization press at 160°C for a predetermined time to obtain crosslinked products (vulcanized rubber). The obtained crosslinked products (vulcanized rubber) were evaluated for the following physical properties. The evaluation results are shown in Table 1.

[0067] [Rolling resistance (70℃ tanδ)] Using vulcanized rubber as a measurement sample, measurements were taken using an ARES-RDA (manufactured by TA Instruments) under conditions of a shear strain of 1.0%, an angular velocity of 100 radians per second, and a temperature of 70°C. The measurement results are expressed as an index, with Comparative Example 1 being set at 100, and a larger index indicates smaller energy loss and better rolling resistance (fuel economy). [Filler dispersibility (Δtanδ)] Using vulcanized rubber as a measurement sample, an ARES viscoelasticity testing device (manufactured by TA Instruments) was used to measure the elastic modulus at an angular velocity of 100 radians per second and a temperature of 50°C over a shear dynamic strain range of 0.1% to 10.0%, and the absolute value of the difference between the maximum and minimum elastic modulus values ​​was calculated as Δtanδ. The value is expressed as an index with Comparative Example 1 set to 100, and a larger value indicates better filler dispersibility.

[0068] [Table 1]

[0069] In Table 1, the details of each component are as follows: Silica: Solvay ZEOSIL 1165MP Silane coupling agent: Eponic Si75 Extender oil: ENEOS T-DAE process oil Carbon black: Mitsubishi Chemical Diablack N330 Vulcanization accelerator (a): Ouchi Shinko Chemical Industry Co., Ltd., product name "Noccela D" Vulcanization accelerator (b): Ouchi Shinko Chemical Industry Co., Ltd., product name "Noccela CZ"

[0070] The results shown in Table 1 show that the vulcanized rubbers of Examples 1 to 6, which were obtained using conjugated diene polymers A to F containing a certain proportion of repeating units (c) having a polyglycol chain, were superior in rolling resistance and filler dispersibility to the vulcanized rubbers of Comparative Examples 1 and 2, which were obtained using conjugated diene polymer G not containing repeating units (c) or conjugated diene polymer H containing less than 0.5 mass% of repeating units (c). Furthermore, the vulcanized rubbers of Examples 1 to 6 had better filler dispersibility than the vulcanized rubber of Comparative Example 3, which was obtained using conjugated diene polymer G having a terminal polyglycol chain and not containing repeating units (c), and also showed a well-balanced improvement in rolling resistance and filler dispersibility.

Claims

1. A conjugated diene polymer having, relative to all repeating units, 50 to 99.5 mass% of repeating units (a) derived from a conjugated diene compound, 0 to 40 mass% of repeating units (b) derived from an aromatic vinyl compound, and 0.5 to 30 mass% of repeating units (c) having a partial structure represented by the following formula (1): 【Chemistry 1】 (In formula (1), n ​​is an integer of 4 to 200, and R １ represents a hydrocarbylene group having 1 to 8 carbon atoms, R ２ represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and * represents a bond.

2. 2. The conjugated diene polymer according to claim 1, which has a weight average molecular weight (Mw) of 50,000 to 2,000,000 in terms of polystyrene as measured by gel permeation chromatography.

3. A polymer composition comprising the conjugated diene polymer according to claim 1 and a crosslinking agent.

4. The polymer composition according to claim 3, further comprising a filler.

5. A crosslinked product obtained by curing the polymer composition according to claim 3 or 4.

6. A tire at least partly using the crosslinked body according to claim 5.

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