Modified liquid diene polymer and additive for rubber

Abstract

The present invention relates to a modified liquid diene polymer comprising a structural unit derived from butadiene, having a weight average molecular weight of 4,000-150,000, and having a modifying group represented by formula (I) (in the formula, R1 represents an alkylene group or phenylene group having 1-10 carbon atoms, R2 represents a hydrogen atom or an alkyl group having 1-2 carbon atoms, and * represents a bond), wherein the amount of the structural unit derived from butadiene is 20-100% by mass based on the total amount of the modified liquid diene polymer, and the amount of 1,2-bonding units having a vinyl group, based on the total amount of the structural unit derived from butadiene, is 0-70 mol%.

Description

Modified liquid diene polymer and rubber additives

[0001] The present invention relates to a modified liquid diene polymer and a rubber additive.

[0002] Conventionally, rubber compositions in which mechanical strength is improved by compounding fillers such as silica or carbon black with rubber components such as natural rubber or styrene-butadiene rubber have been widely used in tire applications requiring abrasion resistance and mechanical strength, etc. It has been pointed out that the dispersion state of the filler in a crosslinked product of a rubber composition compounded with the filler may affect the physical properties of the crosslinked product (e.g., wet grip, abrasion resistance, etc.).

[0003] As a means for improving the dispersibility of fillers in rubber compositions, various methods using liquid rubbers having functional groups have been investigated (see, for example, Patent Documents 1 to 3).

[0004] JP 2000-344949 A JP 2013-249359 A International Publication No. 2019 / 172185

[0005] Various methods for improving the dispersibility of components in rubber compositions have been investigated, and the use of liquid rubbers having functional groups has been reported. However, the effect of improving dispersibility has sometimes been insufficient. Furthermore, when adding liquid rubbers to improve the dispersibility of components in rubber compositions, the liquid rubbers may bleed out, resulting in a decrease in stability.

[0006] Therefore, an object of the present invention is to provide a modified liquid diene polymer which, when added to a rubber composition, has the effect of improving the dispersibility of other components and also has the effect of suppressing bleed-out.

[0007] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, the present invention includes the following preferred embodiments: [1] A modified liquid diene polymer containing a structural unit derived from butadiene, having a weight average molecular weight of 4,000 to 150,000, and represented by the formula (I): [In the formula, R １ represents an alkylene group or a phenylene group having 1 to 10 carbon atoms; ２[2] A modified liquid diene polymer according to [1], wherein the average content of modifying groups represented by formula (I) is 0.5 to 10 per molecule of the modified liquid diene polymer. [3] The modified liquid diene polymer according to [1] or [2], wherein the modified liquid diene polymer does not have a terminal hydroxyl group. [4] The modified liquid diene polymer according to any one of [1] to [3], wherein the amount of cis-1,4-bond units relative to the total amount of 1,4-bond units in the butadiene-derived structural units is 20 to 100 mass %. [5] The modified liquid diene polymer according to any one of [1] to [4], wherein the amount of trans-1,4-bond units relative to the total amount of 1,4-bond units in the structural units derived from butadiene is 30 to 80 mol %. [6] The modified liquid diene polymer according to any one of [1] to [5], wherein the molecular weight distribution is 1.0 to 20.0. [7] A rubber additive comprising the modified liquid diene polymer according to any one of [1] to [6]. [8] The rubber additive according to [7], further comprising at least one selected from the group consisting of a plasticizer, an antioxidant, a filler, and a colorant. [9] The rubber additive according to [7] or [8], which is a solid rubber additive.

[0008] According to the present invention, it is possible to provide a modified liquid diene polymer that has an effect of improving the dispersibility of components in a rubber composition, such as compounding components such as a plasticizer, an antioxidant, a filler, and a colorant, and also has an effect of suppressing bleed-out when added to a rubber composition.

[0009] FIG. 10 is a diagram showing images for evaluating dispersibility for Example 3 and Comparative Example 2.

[0010] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the present invention. Furthermore, in this specification, the expression "x to y" (x and y each represent a number) representing a numerical range means "not less than x and not more than y."

[0011] (Modified Liquid Diene Polymer) The present invention provides a modified liquid diene polymer containing a structural unit derived from butadiene, the polymer having a weight average molecular weight of 4,000 to 150,000 and represented by the formula (I): [In the formula, R １ represents an alkylene group or a phenylene group having 1 to 10 carbon atoms; ２ represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, and * represents a bond, the amount of structural units derived from butadiene is 20 to 100 mass % based on the total amount of the modified liquid diene polymer, and the amount of 1,2-bond units having a vinyl group based on the total amount of structural units derived from butadiene is 0 to 70 mol %.

[0012] The modified liquid diene polymer of the present invention is a polymer containing structural units derived from butadiene, which is modified with a modifying group represented by formula (I) and is liquid at room temperature (25°C).

[0013] The amount of structural units derived from butadiene in the modified liquid diene polymer is 20 to 100% by mass relative to the total amount of the modified liquid diene polymer. When the amount of structural units derived from butadiene is 20% by mass or more, the modification point is sufficient and a decrease in productivity of the modified liquid diene polymer can be suppressed. The amount of structural units derived from butadiene is preferably 30 to 100% by mass, more preferably 35 to 100% by mass, even more preferably 40 to 100% by mass, and even more preferably 50 to 100% by mass relative to the total amount of the modified liquid diene polymer.

[0014] The amount of structural units derived from butadiene is １ H-NMR and １３It can also be calculated from C-NMR measurement or the amount of butadiene monomer in the monomer mixture used in producing the modified liquid diene polymer.

[0015] The structural unit derived from butadiene is not particularly limited as long as it is a structural unit derived from the monomer 1,3-butadiene. Examples include 1,2-bond units, 1,4-bond units (cis-1,4-bond units and trans-1,4-bond units), and structural units in which a modifying group is bonded to these. Here, the 1,2-bond units, cis-1,4-bond units, and trans-1,4-bond units each have a vinyl group in the structural unit derived from butadiene. Furthermore, examples of structural units in which a modifying group is bonded to these include structural units obtained by bonding a modifying group to a moiety derived from the vinyl group in a 1,2-bond unit, and such structural units do not have a vinyl group.

[0016] The amount of 1,2-bond units having a vinyl group relative to the total amount of structural units derived from butadiene is 0 to 70 mol %. When the amount of 1,2-bond units having a vinyl group is 70 mol % or less, it is possible to prevent the viscosity of the modified liquid diene-based polymer from becoming too high, and to prevent a decrease in handleability. The amount of 1,2-bond units having a vinyl group is preferably 5 to 70 mol %, more preferably 5 to 68 mol %. The amounts of 1,2-bond units having a vinyl group, 1,4-bond units, cis-1,4-bond units, and trans-1,4-bond units described below are, respectively: １ It can be measured by H-NMR and infrared absorption spectroscopy, specifically by the method described in the Examples.

[0017] The butadiene-derived structural unit preferably includes a structural unit obtained by bonding a modifying group represented by formula (I) to a vinyl group-derived moiety in a 1,2-bond unit. The amount of the structural unit is preferably 0.1 to 15 mol %, more preferably 1 to 10 mol %, and even more preferably 2 to 9 mol %, based on the total amount of butadiene-derived structural units. The amount of the structural unit can be calculated from the molecular weight of each monomer constituting the modified liquid diene polymer, the weight-average molecular weight of the modified liquid diene polymer, an estimated value for the number of monomers constituting the modified liquid diene polymer, an estimated value for the number of each bond unit, and the average number of modifying groups determined as described above.

[0018] The amount of 1,4-bond units relative to the total amount of structural units derived from butadiene is preferably 30 to 100 mol %, more preferably 30 to 95 mol %, and even more preferably 32 to 95 mol %, relative to the total amount of structural units derived from butadiene, from the viewpoints of handleability and productivity of the polymer having the modifying group represented by Formula (I).

[0019] In one embodiment of the present invention, the amount of cis-1,4-bonded units relative to the total amount of 1,4-bonded units in the structural units derived from butadiene is preferably 20 to 60 mol %, more preferably 30 to 50 mol %.

[0020] In one embodiment of the present invention, the amount of trans-1,4-bond units relative to the total amount of 1,4-bond units in the structural units derived from butadiene is preferably 30 to 80 mol %, more preferably 40 to 80 mol %, and even more preferably 50 to 70 mol %.

[0021] The weight-average molecular weight of the modified liquid diene polymer is 4,000 to 150,000. From the viewpoint of maintaining fluidity, the weight-average molecular weight of the modified liquid diene polymer is preferably 4,000 to 140,000, more preferably 4,500 to 135,000, even more preferably 4,500 to 125,000, even more preferably 4,500 to 100,000, and particularly preferably 4,500 to 50,000. In the present invention, the weight-average molecular weight of the liquid diene polymer is the weight-average molecular weight in terms of polystyrene determined by measurement using gel permeation chromatography (GPC). When the weight-average molecular weight of the liquid diene polymer is within the above range, it is in a liquid form at room temperature, making it easy to handle, providing excellent processability during production, and improving economic efficiency. It has been found that the weight-average molecular weight of the modified liquid diene polymer also affects the bleed-out suppression effect, and increasing the weight-average molecular weight tends to reduce bleed-out. However, the weight-average molecular weight of the modified liquid diene polymer may be adjusted to a desired range for various purposes required for the rubber composition. The modified liquid diene polymer of the present invention can exhibit the effect of reducing bleed-out compared to an unmodified liquid diene polymer having a similar weight-average molecular weight.

[0022] From the viewpoint of handleability such as stringiness, the number average molecular weight of the modified liquid diene polymer is preferably 200 to 150,000, more preferably 900 to 135,000, even more preferably 2,000 to 125,000, still more preferably 2,600 to 100,000, particularly preferably 2,600 to 50,000, and especially preferably 3,800 to 50,000. The number average molecular weight of the liquid diene polymer can also be measured by gel permeation chromatography (GPC).

[0023] The molecular weight distribution (Mw / Mn) of the modified liquid diene polymer is preferably 1.0 to 20.0, more preferably 1.0 to 15.0, even more preferably 1.0 to 10.0, even more preferably 1.0 to 5.0, particularly preferably 1.0 to 2.0, especially preferably 1.0 to 1.5, and extremely preferably 1.0 to 1.3. When Mw / Mn is within the above range, the viscosity variation of the obtained modified liquid diene polymer is small, which is more preferable. The molecular weight distribution (Mw / Mn) means the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in terms of standard polystyrene, determined by GPC measurement.

[0024] The modified liquid diene polymer has the formula (I): [In the formula, R １ represents an alkylene group or a phenylene group having 1 to 10 carbon atoms; ２ represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, and * represents a bond. Such a modifying group will hereinafter also be referred to as a modifying group (I). The modified liquid diene polymer may be modified with one type of modifying group represented by formula (I), or may be modified with two or more types of modifying groups represented by formula (I).

[0025] R in formula (I) １ represents an alkylene group having 1 to 10 carbon atoms or a phenylene group.

[0026] Examples of alkylene groups having 1 to 10 carbon atoms include methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene. The alkylene group may be linear or branched. The alkylene group preferably has 1 to 10 carbon atoms, and more preferably 2 to 6 carbon atoms. A phenylene group is a divalent group having two bonds on the phenyl ring, and the two bonds may be in the ortho, meta, or para position relative to each other. The phenylene group may also be a group in which at least one hydrogen atom bonded to a carbon atom on the phenyl ring is substituted with an alkyl group having 1 to 4 carbon atoms.

[0027] R in formula (I) １is preferably an alkylene group having 2 to 6 carbon atoms from the viewpoint of improving the dispersibility of additives such as fillers.

[0028] R in formula (I) ２ represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms. The alkyl group having 1 to 2 carbon atoms is a methyl group or an ethyl group.

[0029] R in formula (I) ２ is preferably a hydrogen atom from the viewpoint of the interaction or reactivity between the additive such as a filler and the modified liquid diene polymer.

[0030] In formula (I), * represents a bond. It is believed that the bond is preferably bonded to a structural unit derived from butadiene in the modified liquid diene polymer, more preferably to a portion derived from the vinyl group of a 1,4-bonded unit or a portion derived from the vinyl group of a 1,2-bonded unit, even more preferably to a portion derived from the vinyl group of a 1,2-bonded unit, and even more preferably to a portion derived from the side chain vinyl group of a 1,2-bonded unit. Therefore, it is believed that the modifying group represented by formula (I) is preferably contained in a side chain of the diene polymer. When * is bonded to a portion derived from a side chain vinyl group, it is believed that the side chain vinyl group and a compound that provides the modifying group represented by formula (I) have reacted to bond, and that the side chain vinyl group has become a single bond (alkylene group) due to the bond of the modifying group.

[0031] The structure of the modifying group represented by formula (I) can be analyzed, for example, by structural analysis of the resulting polymer by NMR analysis or from the structure of the modifying compound used in synthesizing the polymer.

[0032] The average number of modifying groups represented by formula (I) contained per molecule of the modified liquid diene polymer is preferably 0.5 to 10, more preferably 0.5 to 7, even more preferably 0.5 to 5, still more preferably 1 to 5, and particularly preferably 1 to 4.5, from the viewpoints of suppressing bleed-out of the modified liquid diene polymer and the like, improving affinity with additives such as fillers, and improving the dispersibility of the additives. １ It can be determined by H-NMR.

[0033] The amount of structural units derived from butadiene in the modified liquid diene polymer is 20 to 100% by mass relative to the total amount of the modified liquid diene polymer. Having the amount of structural units derived from butadiene of 20% by mass or more increases the number of modification points, thereby preventing a decrease in productivity of the modified liquid diene polymer. As long as the amount of structural units derived from butadiene is within the above range, the modified liquid diene polymer may be a homopolymer of butadiene, or a copolymer with other monomers copolymerizable with butadiene, such as conjugated diene monomers other than butadiene or aromatic vinyl compounds. Therefore, the modified liquid diene polymer may have only structural units derived from butadiene, or may have, in addition to the structural units derived from butadiene, structural units derived from conjugated diene monomers other than butadiene, structural units derived from aromatic vinyl compounds, etc.

[0034] Examples of conjugated diene monomers other than butadiene include isoprene and β-farnesene, preferably at least one selected from the group consisting of isoprene and β-farnesene, and more preferably isoprene. Examples of aromatic vinyl compounds include styrene. The amount of structural units derived from conjugated diene monomers other than butadiene, such as isoprene, is preferably 0 to 80% by mass, more preferably 0 to 65% by mass, and even more preferably 0 to 50% by mass, based on the total amount of the modified liquid diene polymer.

[0035] In one embodiment of the present invention, the total amount of structural units derived from butadiene and structural units derived from conjugated diene monomers other than butadiene in the modified liquid diene polymer is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and even more preferably 95 to 100% by mass, based on the total amount of the modified liquid diene polymer.

[0036] When the modified liquid diene polymer is a copolymer of butadiene and another monomer copolymerizable with butadiene, the copolymer may be a random copolymer or a block copolymer.

[0037] From the viewpoint of reactivity with the modifying group (I), the modified liquid diene polymer preferably does not have a terminal hydroxyl group. Whether or not the polymer has a terminal hydroxyl group can be determined by the neutralization titration method of the hydroxyl value according to JIS K 0070-1992, infrared absorption spectroscopy (IR), １ This can be confirmed by H-NMR.

[0038] The modified liquid diene polymer as described above has the effect of improving the dispersibility of additives such as fillers and also has the effect of suppressing bleed-out when added to a rubber composition, so that it is possible to sufficiently disperse additives such as fillers while maintaining the stability of the rubber composition. Therefore, it can be suitably blended into any rubber composition containing a dispersion of fillers, etc. Therefore, the modified liquid diene polymer of the present invention is preferably used as a rubber additive.

[0039] (Method for Producing Modified Liquid Diene Polymer) The method for producing the modified liquid diene polymer is not particularly limited. For example, it is preferred to produce an unmodified liquid diene polymer by polymerizing butadiene and, if necessary, other monomers copolymerizable with butadiene, for example, by solution polymerization, and then reacting the unmodified liquid polymer with a modifying compound to produce the modified liquid diene polymer.

[0040] As the solution polymerization method, a known method or a method equivalent to a known method can be applied. For example, a butadiene-containing monomer is polymerized in a solvent using a Ziegler catalyst, a metallocene catalyst, or an anionically polymerizable active metal or active metal compound, optionally in the presence of a polar compound.

[0041] Examples of the solvent include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and isooctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; and aromatic hydrocarbons such as benzene, toluene, and xylene.

[0042] Examples of the anionically polymerizable active metal include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium, and barium; and lanthanoid rare earth metals such as lanthanum and neodymium. Among the anionically polymerizable active metals, alkali metals and alkaline earth metals are preferred, and alkali metals are more preferred.

[0043] The anionically polymerizable active metal compound is preferably an organic alkali metal compound. Examples of the organic alkali metal compound include organic monolithium compounds such as methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; polyfunctional organic lithium compounds such as dilithiomethane, dilithionaphthalene, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, and 1,3,5-trilithiobenzene; sodium naphthalene, potassium naphthalene, and the like. Among these organic alkali metal compounds, organic lithium compounds are preferred, and organic monolithium compounds are more preferred.

[0044] The amount of the organic alkali metal compound used can be appropriately determined depending on the target melt viscosity, molecular weight, etc. of the modified liquid diene polymer, but it is usually used in an amount of 0.01 to 3 parts by mass per 100 parts by mass of all monomers.

[0045] The above organic alkali metal compounds can also be reacted with a secondary amine such as dibutylamine, dihexylamine, or dibenzylamine to form organic alkali metal amides.

[0046] In anionic polymerization, polar compounds are usually used to adjust the microstructure (e.g., vinyl content) of the unmodified liquid diene polymer without deactivating the reaction. Examples of polar compounds include ether compounds such as dibutyl ether, tetrahydrofuran, and ethylene glycol diethyl ether; tertiary amines such as tetramethylethylenediamine and trimethylamine; alkali metal alkoxides; and phosphine compounds. The polar compound is usually used in an amount of 0.01 to 1,000 moles per mole of the organic alkali metal compound.

[0047] The temperature for solution polymerization is usually in the range of −80 to 150° C., preferably in the range of 0 to 100° C., and more preferably in the range of 10 to 90° C. The polymerization may be carried out in either a batch or continuous manner.

[0048] The polymerization reaction can be terminated by adding a polymerization terminator. Examples of the polymerization terminator include alcohols such as methanol and isopropanol. The unmodified liquid diene polymer can be isolated by pouring the resulting polymerization reaction solution into a poor solvent such as methanol to precipitate the unmodified liquid diene polymer, or by washing the polymerization reaction solution with water, separating it, and then drying it.

[0049] The unmodified liquid diene polymer thus obtained may be modified by reacting it as it is (in an unhydrogenated state) with a compound that provides the functional group represented by formula (I). Alternatively, the unmodified liquid diene polymer may be modified by hydrogenating at least a portion of the unsaturated bonds contained in the unmodified liquid diene polymer, and then reacting it with a compound that provides the functional group represented by formula (I).

[0050] In order to more favorably exhibit the properties of the modifying group represented by formula (I), the unmodified liquid diene polymer is preferably not modified with a functional group such as a hydroxyl group. When the unmodified liquid diene polymer is not modified with another functional group, the stability of the resulting modified liquid diene polymer tends to be superior. Furthermore, the interaction (e.g., reactivity) of the functional group represented by formula (I) contained in the modified liquid diene polymer with a filler (e.g., silica) tends to be superior.

[0051] The unmodified liquid diene polymer may be, for example, a compound represented by the formula (II): [R in formula (II)] １ and R ２ are R in formula (I), respectively. １ and R ２ A modified liquid diene polymer modified with the modifying group represented by formula (I) can be produced by reacting the unmodified liquid diene polymer with one type of compound (II) or two or more types of compound (II).

[0052] The mercapto group (—SH) of compound (II) undergoes a radical addition reaction with a carbon-carbon unsaturated bond contained in the unmodified liquid diene polymer, thereby introducing the functional group represented by formula (I) into the polymer. During this radical addition reaction, it is presumed that the radical addition reaction occurs preferentially with the carbon-carbon unsaturated bond in the side chain contained in the 1,2-bonded butadiene unit of the unmodified liquid diene polymer.

[0053] R in the above formula (II) １ and R ２ The definition and specific examples of R in formula (I) １ and R ２ Specific examples of the compound represented by formula (II) above include 2-aminoethanethiol, 2-methylaminoethanethiol, 2-ethylaminoethanethiol, 2-dimethylaminoethanethiol, 2-diethylaminoethanethiol, p-aminothiophenol, p-methylaminothiophenol, and p-dimethylaminothiophenol.

[0054] The method for adding the compound represented by formula (II) to the unmodified liquid diene polymer is not particularly limited, and for example, a method can be adopted in which the compound represented by formula (II) and, if necessary, a radical catalyst are added to the unmodified liquid diene polymer, and the mixture is heated in the presence or absence of an organic solvent. There are no particular limitations on the radical generator used, and commercially available organic peroxides, azo compounds, hydrogen peroxide, etc. can be used.

[0055] Examples of the organic peroxides include methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, acetylacetone peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)butylperoxide, hexane, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, 2,5-dimethylhexane 2,5-dihydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, bis(t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxyisopropyl)benzene hydroxy)hexane, 2,5-hexanoyl peroxide, lauroyl peroxide, succinic peroxide, benzoyl peroxide and its substituted derivatives, 2,4-dichlorobenzoyl peroxide, meta-toluoyl peroxide, diisopropyl peroxydicarbonate, t-butyl-2-ethylhexanoate, di-2-ethylhexyl peroxydicarbonate, dimethoxyisopropyl peroxycarbonate, di(3-methyl-3-methoxybutyl)peroxydicarbonate, t-butyl Examples of the peroxyacetate include t-butyl peroxypivalate, t-butyl peroxyneodecanoate, t-butyl peroxyoctanoate, t-butyl peroxy 3,3,5-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxycarbonate, t-butyl peroxybenzoate, t-butyl peroxyisobutyrate, n-butyl-4,4-di(t-butylperoxy)valerate, and t-hexylperoxyisopropyl monocarbonate.

[0056] Examples of the azo compounds include 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis(2-(2-imidazolin-2-yl)propane), 2,2'- Examples include azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), 2,2'-azobis(2-hydroxymethylpropionitrile), 4,4'-azobis(4-cyanovaleric acid), dimethyl 2,2'-azobis(2-methylpropionate), 2-cyano-2-propylazoformamide, and 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile.

[0057] The organic solvent used in the above method generally includes hydrocarbon solvents and halogenated hydrocarbon solvents, and among these, hydrocarbon solvents such as n-butane, n-hexane, n-heptane, cyclohexane, benzene, toluene, and xylene are preferred.

[0058] Furthermore, when the reaction of adding the modified compound is carried out by the above method, an antioxidant may be added from the viewpoint of suppressing side reactions.

[0059] Examples of the antioxidants that can be used in this case include 2,6-di-t-butyl-4-methylphenol (BHT), 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol) (AO-40), 3,9-bis[1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyl] ... pionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (AO-80), 2,4-bis[(octylthio)methyl]-6-methylphenol (Irganox 1520L), 2,4-bis[(dodecylthio)methyl]-6-methylphenol (Irganox 1726), 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate (Sumilizer GS), 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (Sumilizer GM), 6-t-butyl-4-[3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yloxy)propyl]-2-methylphenol (Sumilizer GP), tris(2,4-di-t-butylphenyl) phosphite (Irgafos 168), di Examples of the antioxidant include octadecyl 3,3'-dithiobispropionate, hydroquinone, p-methoxyphenol, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (Nocrac 6C), bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate (LA-77Y), N,N-dioctadecylhydroxylamine (Irgastab FS042), bis(4-t-octylphenyl)amine (Irganox 5057), etc. The antioxidants may be used alone or in combination of two or more.

[0060] The amount of antioxidant added is preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, per 100 parts by mass of the unmodified liquid diene polymer.

[0061] In the modified liquid diene polymer, the position at which the functional group is introduced may be the terminal of the polymer chain or a side chain of the polymer chain, but from the viewpoint of easily introducing multiple functional groups, a side chain of the polymer chain is preferable. Furthermore, the functional group may be contained alone or in combination with two or more types. Therefore, the modified liquid diene polymer may be modified with one type of modifying compound, or may be modified with two or more types of modifying compounds.

[0062] The mixing ratio of the unmodified liquid diene polymer to the modified compound may be appropriately set, for example, so that the average number of functional groups per molecule of the modified liquid diene polymer is a desired value. For example, it is preferable to mix the unmodified liquid diene polymer to the modified compound (e.g., compound (II)) so that the mass ratio (unmodified liquid diene polymer / modified compound) is 0.3 to 50.

[0063] An effective method for producing a modified liquid diene polymer having specific properties is to carry out a radical addition reaction of a modifying compound (e.g., compound (II)) at an appropriate reaction temperature for a sufficient reaction time. For example, the temperature in the reaction of adding a modifying compound to an unmodified liquid diene polymer is preferably 10 to 200°C, more preferably 50 to 180°C. The reaction time is preferably 1 to 200 hours, more preferably 1 to 100 hours, and even more preferably 1 to 50 hours.

[0064] From the viewpoint of adjusting the melt viscosity, molecular weight distribution (Mw / Mn), etc. of the liquid diene polymer within the above ranges, it is preferred to add a radical catalyst during the modification reaction and to carry out the reaction at a low temperature for a short time.

[0065] (Rubber Additive) In a preferred embodiment of the present invention, the modified liquid diene polymer is used in a rubber additive. The present invention also provides a rubber additive containing the modified liquid diene polymer. The rubber additive may contain only the modified liquid diene polymer, or may contain the modified liquid diene polymer and other additives.

[0066] The other additives are not particularly limited and may be, for example, a plasticizer, an antioxidant, a filler, a colorant, etc. In a preferred embodiment, the rubber additive contains only the modified liquid diene polymer, or contains the modified liquid diene polymer and further contains at least one selected from the group consisting of a plasticizer, an antioxidant, a filler, and a colorant.

[0067] The amount of the modified liquid diene polymer contained in the rubber additive is not particularly limited, and may be, for example, 50 to 100 mass%, 70 to 100 mass%, 80 to 100 mass%, 90 to 100 mass%, etc., relative to the total amount of the rubber additive. When other additives are further contained, the amount of the modified liquid diene polymer may be 50 to 99 mass%, 70 to 97 mass%, 80 to 95 mass%, etc., relative to the total amount of the rubber additive.

[0068] The rubber additive is an additive used by adding it to a rubber component. The rubber component may be a solid rubber. Therefore, the rubber additive of the present invention is preferably a solid rubber additive. Furthermore, from the viewpoint of obtaining an effect of improving the dispersibility of fillers and the like, the rubber additive is preferably used together with a filler.

[0069] Examples of fillers include inorganic fillers such as carbon black, silica, clay, mica, calcium carbonate, magnesium hydroxide, aluminum hydroxide, barium sulfate, titanium oxide, glass fiber, fibrous fillers, and glass balloons; and organic fillers such as resin particles, wood flour, and cork powder. When such fillers are used together with the modified liquid diene polymer of the present invention, the resulting composition can be improved in physical properties such as mechanical strength, heat resistance, and weather resistance, and the hardness can be adjusted and the amount of rubber can be increased. From the viewpoint of improving physical properties such as mechanical strength, carbon black and silica are preferred among the fillers (C). These fillers (C) may be used alone or in combination of two or more. As the filler (C), at least one selected from the group consisting of carbon black and silica is preferred.

[0070] The amount of filler per 100 parts by mass of solid rubber is preferably 0.5 to 200 parts by mass, more preferably 20 to 180 parts by mass, even more preferably 25 to 150 parts by mass, and still more preferably 30 to 150 parts by mass. When the filler amount is within the above range, processability, rolling resistance performance, mechanical strength, and abrasion resistance are improved.

[0071] Examples of carbon black include furnace black, channel black, thermal black, acetylene black, and ketjen black. Among these carbon blacks, furnace black is preferred from the viewpoint of improving crosslinking rate and mechanical strength. These carbon blacks may be used alone or in combination of two or more.

[0072] The average particle size of carbon black is preferably 5 to 100 nm, more preferably 5 to 80 nm, even more preferably 5 to 70 nm, and even more preferably 5 to 25 nm, from the viewpoint of improving dispersibility, mechanical strength, hardness, etc. The average particle size of carbon black can be determined by measuring the particle diameters using a transmission electron microscope and calculating the average value.

[0073] Commercially available furnace black products include, for example, "Diablack" manufactured by Mitsubishi Chemical Corporation and "Seast" manufactured by Tokai Carbon Co., Ltd. Commercially available acetylene black products include, for example, "Denka Black" manufactured by Denki Kagaku Kogyo Co., Ltd. Commercially available ketjen black products include, for example, "ECP600JD" manufactured by Lion Corporation.

[0074] From the viewpoint of improving wettability and dispersibility in solid rubber, carbon black may be subjected to an acid treatment using nitric acid, sulfuric acid, hydrochloric acid, or a mixture thereof, or a surface oxidation treatment by heat treatment in the presence of air. Also, from the viewpoint of improving the mechanical strength of the crosslinked product, carbon black may be subjected to a heat treatment at 2,000 to 3,000°C in the presence of a graphitization catalyst. Examples of the graphitization catalyst include boron, boron oxide (e.g., B ２ O ２ , B ２ O ３ , B ４ O３ , B ４ O ５ etc.), boron oxoacids (e.g., orthoboric acid, metaboric acid, tetraboric acid, etc.) and their salts, boron carbides (e.g., B ４ C, B ６ C, etc.), boron nitride (BN), and other boron compounds are preferably used.

[0075] Carbon black can also be used after adjusting its particle size by pulverization, etc. For pulverization of carbon black, a high-speed rotary pulverizer (hammer mill, pin mill, cage mill), various ball mills (tumbling mill, vibration mill, planetary mill), stirring mill (bead mill, attritor, flow-tube mill, annular mill), etc. can be used.

[0076] Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these silicas, wet silica is preferred from the viewpoint of further improving processability, mechanical strength, and abrasion resistance. These silicas may be used alone or in combination of two or more.

[0077] From the viewpoint of improving processability, rolling resistance, mechanical strength, and abrasion resistance, the average particle size of silica is preferably 0.5 to 200 nm, more preferably 5 to 150 nm, even more preferably 10 to 100 nm, and even more preferably 10 to 50 nm. The average particle size of silica can be determined by measuring the diameter of particles using a transmission electron microscope and calculating the average value.

[0078] The average particle size of the aluminum hydroxide is preferably 5 to 20 nm, more preferably 5 to 15 nm, and even more preferably 5 to 10 nm. Resin microbeads are preferably added as a foaming agent. The average particle size of the resin microbeads is preferably 10 to 100 μm, and even more preferably 15 to 90 μm.

[0079] (Rubber Composition) According to the present invention, a rubber composition can be obtained that contains at least the modified liquid diene polymer of the present invention and a rubber component (preferably solid rubber).

[0080] The solid rubber (A) refers to a rubber that can be handled in a solid state at 20°C. The Mooney viscosity ML(1+4) of the solid rubber (A) at 100°C is typically 20 to 200. Examples of the solid rubber (A) include natural rubber, styrene butadiene rubber (hereinafter also referred to as "SBR"), butadiene rubber, isoprene rubber, butyl rubber, halogenated butyl rubber, ethylene propylene diene rubber, butadiene acrylonitrile copolymer rubber, chloroprene rubber, acrylic rubber, fluororubber, and urethane rubber. Among these solid rubbers (A), natural rubber, SBR, butadiene rubber, and isoprene rubber are preferred, with natural rubber and SBR being more preferred. These solid rubbers (A) may be used alone or in combination of two or more.

[0081] From the viewpoint of fully exhibiting the properties of the resulting rubber composition and cross-linked product, the number average molecular weight (Mn) of the solid rubber (A) is preferably 80,000 or more, and more preferably within the range of 100,000 to 3,000,000. Note that the number average molecular weight in this specification is the number average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0082] Examples of natural rubber include TSR (Technically Specified Rubber) such as SMR (Malaysian TSR), SIR (Indonesian TSR), and STR (Thai TSR), as well as natural rubber commonly used in the tire industry, such as RSS (Ribbed Smoked Sheet), and modified natural rubber such as high-purity natural rubber, epoxidized natural rubber, hydroxylated natural rubber, hydrogenated natural rubber, and grafted natural rubber. Of these, SMR20, STR20, and RSS#3 are preferred in terms of their low quality variation and ease of availability. These natural rubbers may be used alone or in combination of two or more.

[0083] As the SBR, a general SBR used for tires can be used. Specifically, SBR having a styrene content of 0.1 to 70 mass% is preferred, more preferably 5 to 50 mass%, and even more preferably 15 to 35 mass%. SBR having a vinyl content of 0.1 to 60 mass%, more preferably 0.1 to 55 mass% is preferred. In this specification, the "vinyl content" of SBR means the proportion of 1,2-bonds contained in the butadiene structural unit, １ It can be determined by H-NMR measurement.

[0084] The weight average molecular weight (Mw) of SBR is preferably 100,000 to 2,500,000, more preferably 150,000 to 2,000,000, and even more preferably 200,000 to 1,500,000. Within the above range, both processability and mechanical strength can be achieved. Note that the weight average molecular weight in this specification refers to the weight average molecular weight in terms of polystyrene obtained by measurement using gel permeation chromatography (GPC).

[0085] The glass transition temperature of SBR determined by differential thermal analysis is preferably −95 to 0° C., and more preferably −95 to −5° C. By setting the glass transition temperature within the above range, the viscosity of SBR can be set within a range that allows easy handling.

[0086] SBR is obtained by copolymerizing styrene and butadiene. There are no particular limitations on the method for producing SBR, and any of emulsion polymerization, solution polymerization, gas phase polymerization, and bulk polymerization can be used. Among these production methods, emulsion polymerization and solution polymerization are preferred.

[0087] Emulsion-polymerized styrene-butadiene rubber (hereinafter also referred to as E-SBR) can be produced by a known or similar ordinary emulsion polymerization method, for example, by emulsifying and dispersing predetermined amounts of styrene and butadiene monomers in the presence of an emulsifier, and then emulsion-polymerizing the resulting mixture with a radical polymerization initiator.

[0088] Solution-polymerized styrene-butadiene rubber (hereinafter also referred to as S-SBR) can be produced by a conventional solution polymerization method, for example, by polymerizing styrene and butadiene in a solvent using an anionically polymerizable active metal, optionally in the presence of a polar compound.

[0089] Examples of the solvent include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and isooctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; and aromatic hydrocarbons such as benzene and toluene. These solvents are usually preferably used in such a manner that the monomer concentration becomes 1 to 50% by mass.

[0090] Examples of the active metal capable of anion polymerization include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium, and barium; and lanthanoid rare earth metals such as lanthanum and neodymium. Among these active metals, alkali metals and alkaline earth metals are preferred, and alkali metals are more preferred. Furthermore, among alkali metals, organic alkali metal compounds are more preferably used.

[0091] Examples of organic alkali metal compounds include organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; polyfunctional organic lithium compounds such as dilithiomethane, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, and 1,3,5-trilithiobenzene; sodium naphthalene, and potassium naphthalene. Among these, organic lithium compounds are preferred, and organic monolithium compounds are more preferred. The amount of the organic alkali metal compound used is determined appropriately depending on the molecular weight of the required S-SBR. The organic alkali metal compound can also be reacted with a secondary amine such as dibutylamine, dihexylamine, or dibenzylamine to be used as an organic alkali metal amide.

[0092] The polar compound is not particularly limited as long as it is a compound that is commonly used in anionic polymerization to adjust the microstructure of butadiene moieties and the distribution of styrene in the copolymer chain without deactivating the reaction. Examples thereof include ether compounds such as dibutyl ether, tetrahydrofuran, and ethylene glycol diethyl ether; tertiary amines such as tetramethylethylenediamine and trimethylamine; alkali metal alkoxides; and phosphine compounds.

[0093] The temperature of the polymerization reaction is usually in the range of −80 to 150° C., preferably 0 to 100° C., and more preferably 30 to 90° C. The polymerization may be carried out batchwise or continuously. In order to improve the random copolymerization of styrene and butadiene, it is preferable to continuously or intermittently supply styrene and butadiene to the reaction liquid so that the composition ratio of styrene and butadiene in the polymerization system falls within a specific range.

[0094] The polymerization reaction can be terminated by adding an alcohol such as methanol or isopropanol as a polymerization terminator. After the polymerization reaction has been terminated, the solvent can be separated from the polymerization solution by direct drying or steam stripping, and the target S-SBR can be recovered. Note that, before removing the solvent, the polymerization solution and extender oil may be mixed in advance and recovered as an oil-extended rubber.

[0095] As the SBR, modified SBR in which a functional group has been introduced into SBR may be used as long as the effects of the present invention are not impaired. Examples of the functional group include an amino group, an alkoxysilyl group, a hydroxyl group, an epoxy group, and a carboxyl group.

[0096] Examples of methods for producing modified SBR include a method in which, before adding a polymerization terminator, a coupling agent capable of reacting with the active polymerization terminals is added, such as tin tetrachloride, tetrachlorosilane, dimethyldichlorosilane, dimethyldiethoxysilane, tetramethoxysilane, tetraethoxysilane, 3-aminopropyltriethoxysilane, tetraglycidyl-1,3-bisaminomethylcyclohexane, or 2,4-tolylenediisocyanate; a polymerization terminal modifier such as 4,4'-bis(diethylamino)benzophenone or N-vinylpyrrolidone; or other modifiers described in JP 2011-132298 A. In this modified SBR, the position in the polymer where the functional group is introduced may be the polymerization terminal or a side chain of the polymer chain.

[0097] Examples of butadiene rubber that can be used include commercially available butadiene rubbers polymerized using Ziegler catalysts such as titanium tetrahalide-trialkylaluminum catalysts, diethylaluminum chloride-cobalt catalysts, trialkylaluminum-boron trifluoride-nickel catalysts, and diethylaluminum chloride-nickel catalysts; lanthanoid rare earth metal catalysts such as triethylaluminum-organic acid neodymium-Lewis acid catalysts; and organic alkali metal compounds, similar to S-SBR. Butadiene rubbers polymerized using Ziegler catalysts have a high cis-isomer content and are therefore preferred. Ultra-high cis-isomer butadiene rubbers obtained using lanthanoid rare earth metal catalysts may also be used.

[0098] From the viewpoint of improving rolling resistance performance, the vinyl content of the butadiene rubber is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. There is no particular lower limit for the vinyl content. In addition, although the glass transition temperature varies depending on the vinyl content, it is preferably -40°C or less, and more preferably -50°C or less.

[0099] The weight average molecular weight (Mw) of the butadiene rubber is preferably 90,000 to 2,000,000, and more preferably 150,000 to 1,500,000. When Mw is within the above range, the processability and mechanical strength are improved.

[0100] The butadiene rubber may have a branched structure or a polar functional group by using a polyfunctional modifier, such as tin tetrachloride, silicon tetrachloride, an alkoxysilane having an epoxy group in the molecule, or an amino group-containing alkoxysilane, in part, as long as the effects of the present invention are not impaired.

[0101] Examples of isoprene rubber that can be used include commercially available isoprene rubber polymerized using Ziegler catalysts such as titanium tetrahalide-trialkylaluminum catalysts, diethylaluminum chloride-cobalt catalysts, trialkylaluminum-boron trifluoride-nickel catalysts, and diethylaluminum chloride-nickel catalysts; lanthanoid rare earth metal catalysts such as triethylaluminum-organic acid neodymium-Lewis acid catalysts; or organic alkali metal compounds, similar to S-SBR. Isoprene rubber polymerized using a Ziegler catalyst has a high cis-isomer content and is therefore preferred. Isoprene rubber with an ultra-high cis-isomer content obtained using a lanthanoid rare earth metal catalyst may also be used.

[0102] From the viewpoint of improving rolling resistance performance, the vinyl content of the isoprene rubber is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. There is no particular lower limit for the vinyl content. In addition, although the glass transition temperature varies depending on the vinyl content, it is preferably -20°C or less, and more preferably -30°C or less.

[0103] The weight average molecular weight (Mw) of the isoprene rubber is preferably 90,000 to 2,000,000, and more preferably 150,000 to 1,500,000. When the Mw is within the above range, the processability and mechanical strength are improved.

[0104] The isoprene rubber may have a branched structure or a polar functional group by using a polyfunctional modifier, such as tin tetrachloride, silicon tetrachloride, an alkoxysilane having an epoxy group in the molecule, or an amino group-containing alkoxysilane, in part, as long as the effects of the present invention are not impaired.

[0105] In the rubber composition described above, the content of the modified liquid diene polymer (B) per 100 parts by mass of the solid rubber (A) is preferably 0.1 to 50 parts by mass, more preferably 0.1 to 45 parts by mass, even more preferably 0.5 to 40 parts by mass, particularly preferably 1 to 40 parts by mass, particularly preferably 2 to 40 parts by mass, extremely preferably 3 to 35 parts by mass, and extremely preferably 5 to 30 parts by mass. When the content of the modified liquid diene polymer (B) is within the above range, the dispersion state of other components in the rubber composition, particularly the filler (C), is ideal, thereby improving the rigidity of the resulting composition and crosslinked product. For example, when the rubber composition is used in tires or the like, improved grip performance (wet grip performance and / or ice grip performance) leads to improved steering stability. Furthermore, rolling resistance performance is also improved. The content of the modified liquid diene polymer (B) per 100 parts by mass of the solid rubber (A) is preferably 5 to 25 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 10 to 20 parts by mass.

[0106] In the rubber composition described above, the content of the solid rubber (A) is preferably 20 to 90% by mass, more preferably 25 to 85% by mass, and even more preferably 30 to 80% by mass, based on the total amount of the rubber composition. When the content of the solid rubber (A) is within the above range, the rubber composition has a good balance between gripping properties and abrasion resistance.

[0107] In a preferred embodiment of the present invention, the rubber composition contains a filler (C). Examples of the filler (C) include the fillers described above, such as carbon black and / or silica.

[0108] From the viewpoint of improving the processability and abrasion resistance of the resulting rubber composition and its crosslinked product, the filler (C) preferably contains carbon black and / or silica, and more preferably contains silica.

[0109] In a preferred embodiment of the rubber composition of the present invention, the content of the filler (C) per 100 parts by mass of the solid rubber (A) is preferably 0.5 to 200 parts by mass, more preferably 20 to 180 parts by mass, even more preferably 25 to 150 parts by mass, and even more preferably 30 to 150 parts by mass. When the content of the filler (C) is within the above range, processability, rolling resistance, mechanical strength, and abrasion resistance are improved. A content of the filler (C) of at least the above lower limit, preferably 30% by mass or more, is preferred from the viewpoint of the abrasion resistance of the resulting rubber composition, while a content of at most the above upper limit, preferably 150% by mass or less, is preferred from the viewpoint of the gripping properties of the resulting rubber composition. In a preferred embodiment, the content of the filler (C) is preferably 33 to 140 parts by mass, more preferably 35 to 130 parts by mass, even more preferably 40 to 120 parts by mass, even more preferably 50 to 110 parts by mass, and extremely preferably 60 to 100 parts by mass.

[0110] The amount of filler other than silica and carbon black in the filler (C) is not particularly limited, but may be, for example, 0 to 120 parts by mass, preferably 0 to 90 parts by mass, more preferably 0 to 80 parts by mass, and even more preferably 0 to 70 parts by mass, relative to 100 parts by mass of the solid rubber (A).

[0111] The total mass of the solid rubber (A), the modified liquid diene-based polymer (B), and the filler (C) contained in the rubber composition according to a preferred embodiment of the present invention is preferably 10 to 100 mass%, more preferably 15 to 100 mass%, based on the total amount of the rubber composition.

[0112] A rubber composition according to a preferred embodiment of the present invention may further contain a crosslinking agent (D) to crosslink the rubber. Examples of the crosslinking agent (D) include sulfur, sulfur compounds, oxygen, organic peroxides, phenolic resins, amino resins, quinones and quinone dioxime derivatives, halogen compounds, aldehyde compounds, alcohol compounds, epoxy compounds, metal halides and organometallic halides, and silane compounds. Examples of sulfur compounds include morpholine disulfide and alkylphenol disulfides. Examples of organic peroxides include cyclohexanone peroxide, methyl acetoacetate peroxide, t-butyl peroxyisobutyrate, t-butyl peroxybenzoate, benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, di-t-butyl peroxide, and 1,3-bis(t-butylperoxyisopropyl)benzene. These crosslinking agents (D) may be used alone or in combination of two or more.

[0113] For example, when the rubber composition contains sulfur or a sulfur compound as a crosslinking agent (D) for crosslinking (vulcanizing) the rubber, the rubber composition may further contain a vulcanization accelerator (E). Examples of the vulcanization accelerator (E) include guanidine compounds, sulfenamide compounds, thiazole compounds, thiuram compounds, thiourea compounds, dithiocarbamic acid compounds, aldehyde-amine compounds, aldehyde-ammonia compounds, imidazoline compounds, and xanthate compounds. These vulcanization accelerators (E) may be used alone or in combination of two or more. The vulcanization accelerator (E) is preferably contained in an amount of 0.1 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the solid rubber (A).

[0114] When the rubber composition contains, for example, sulfur, a sulfur compound, or the like as a crosslinking agent (D) for crosslinking (vulcanizing) the rubber, the rubber composition may further contain a vulcanization aid (F). Examples of the vulcanization aid (F) include fatty acids such as stearic acid, metal oxides such as zinc oxide, and fatty acid metal salts such as zinc stearate. These vulcanization aids (F) may be used alone or in combination of two or more. The amount of the vulcanization aid (F) is preferably 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the solid rubber (A).

[0115] When the rubber composition contains silica as the filler (C), the rubber composition preferably further contains a silane coupling agent, such as a sulfide compound, a mercapto compound, a vinyl compound, an amino compound, a glycidoxy compound, a nitro compound, or a chloro compound.

[0116] Examples of sulfide compounds include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-trimethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, and 3-trimethoxysilylpropyl-N,N-dimethylsilyl. thiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-octanoylthio-1-propyltriethoxysilane, and the like.

[0117] Examples of mercapto compounds include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane.

[0118] Examples of vinyl compounds include vinyltriethoxysilane and vinyltrimethoxysilane.

[0119] Examples of amino compounds include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, and 3-(2-aminoethyl)aminopropyltrimethoxysilane.

[0120] Examples of glycidoxy compounds include γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycidoxypropylmethyldimethoxysilane.

[0121] Examples of nitro compounds include 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane.

[0122] Examples of chloro-based compounds include 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane.

[0123] Other compounds include, for example, octyltriethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, and hexadecyltrimethoxysilane.

[0124] These silane coupling agents may be used alone or in combination of two or more. Among these silane coupling agents, bis(3-triethoxysilylpropyl) disulfide, bis(3-triethoxysilylpropyl) tetrasulfide, and 3-mercaptopropyltrimethoxysilane are preferred from the viewpoints of the large addition effect and cost.

[0125] The amount of the silane coupling agent is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and even more preferably 1 to 15 parts by mass, relative to 100 parts by mass of silica. When the content of the silane coupling agent is within the above range, dispersibility, coupling effect, reinforcement, and abrasion resistance are improved.

[0126] A rubber composition according to a preferred embodiment of the present invention includes at least one resin. The resin may be a synthetic resin or a natural resin. These resins may be used alone or in combination of two or more.

[0127] Examples of synthetic resins include petroleum-based resins, and oligomers obtained by polymerizing raw materials consisting of C5 fractions, C9 fractions, refined components of C5 fractions, refined components of C9 fractions, or mixtures of these fractions or refined components can be used. Modified oligomers obtained in this manner, such as by hydrogenation, can also be used. Examples of C5 fractions include cyclopentadiene, dicyclopentadiene, isoprene, 1,3-pentadiene, 2-methyl-1-butene, 2-methyl-2-butene, 1-pentene, 2-pentene, and cyclopentene. Examples of C9 fractions include styrene, allylbenzene, α-methylstyrene, vinyltoluene, β-methylstyrene, and indene. Alkylphenol resins and xylene resins can also be used.

[0128] As natural resins, rosin resins or terpene resins can be used. Rosin resins are resins obtained from pine trees, and their main component is a mixture of abietic acid and its isomers. Modified versions of these resins, such as esterified, polymerized, and hydrogenated, are also included. Unmodified rosin resins include tall rosin, gum rosin, and wood rosin. Other examples include polymerized rosin, disproportionated rosin, hydrogenated rosin, maleic acid-modified rosin, fumaric acid-modified rosin, and esterified versions of these resins, such as those modified by hydrogenation. Terpene resins are oligomers obtained by polymerizing raw materials containing terpene monomers. Modified versions of these oligomers, such as those modified by hydrogenation, are also included. Examples of the terpene monomer include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrein, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, sabinene, paramentadienes, and carenes, each of which has a monoterpene, sesquiterpene, or diterpene skeleton. ８ H ６ O), vinyl aromatic compounds, phenolic monomers, etc., and the resulting oligomers may be modified by hydrogenation or the like.

[0129] The amount of resin in the rubber composition is preferably 0 to 400 parts by mass, more preferably 0 to 200 parts by mass, and even more preferably 0 to 150 parts by mass, per 100 parts by mass of solid rubber. When the rubber composition contains a resin, it is possible to impart tackiness to the rubber composition, improve processability, and improve the slipperiness of the rubber.

[0130] The rubber composition may contain, as needed, softeners such as silicone oil, aromatic oil, TDAE (Treated Distilled Aromatic Extracts), MES (Mild Extracted Solvates), RAE (Residual Aromatic Extracts), process oils such as paraffin oil and naphthenic oil, and resin components such as coumarone-indene resins, for the purpose of improving processability, fluidity, etc., within a range that does not impair the effects of the present invention. When the rubber composition contains the process oil as a softener, the content thereof is preferably less than 50 parts by mass per 100 parts by mass of the solid rubber (A).

[0131] The rubber composition may contain additives such as antioxidants, waxes, antioxidants, lubricants, light stabilizers, scorch inhibitors, processing aids, colorants such as pigments and dyes, flame retardants, antistatic agents, matting agents, antiblocking agents, UV absorbers, mold release agents, foaming agents, antibacterial agents, antifungal agents, and fragrances, as needed, to improve weather resistance, heat resistance, and oxidation resistance, as long as the effects of the present invention are not impaired. Examples of antioxidants include hindered phenol compounds, phosphorus compounds, lactone compounds, and hydroxyl compounds. Examples of antioxidants include amine-ketone compounds, imidazole compounds, amine compounds, phenol compounds, sulfur compounds, and phosphorus compounds. These additives may be used alone or in combination of two or more.

[0132] (Method for Producing Rubber Composition) The method for producing the rubber composition is not particularly limited as long as it can uniformly mix the above-mentioned components. Examples of equipment used for producing the rubber composition include tangential or intermeshing internal mixers such as kneader-ruders, Brabenders, Banbury mixers, and internal mixers, single-screw extruders, twin-screw extruders, mixing rolls, and rollers. The rubber composition can usually be produced at a temperature range of 70 to 270°C.

[0133] (Cross-linked Product) A cross-linked product can be obtained by cross-linking the above rubber composition. The cross-linking conditions for the rubber composition can be appropriately set depending on the application, etc. For example, when sulfur or a sulfur compound is used as a cross-linking agent and the rubber composition is placed in a mold and heated to cross-link (vulcanize), the cross-linking temperature can be typically 120 to 200°C and the pressure condition can be typically 0.5 to 2.0 MPa, and the cross-linking (vulcanization) can be performed.

[0134] The rubber composition and the crosslinked product of the rubber composition can also be used as at least a part of a tire. The tire obtained in this manner has excellent rolling resistance and good abrasion resistance because the dispersion state of other components such as the filler (C) is ideal (for example, the Payne effect is sufficiently reduced). Furthermore, the tire obtained from the rubber composition described above also has excellent grip performance (wet grip performance and / or ice grip performance). Furthermore, bleed-out of the modified liquid diene polymer is suppressed, resulting in excellent stability.

[0135] Examples of tire parts in which the rubber composition and the crosslinked product of the rubber composition can be used include treads (cap treads and under treads), sidewalls, rubber reinforcing layers for run-flat tires (liners and the like), rim cushions, bead fillers, bead insulation, bead apexes, clinch apexes, belts, belt cushions, breakers, breaker cushions, chafers, chafer pads, and strip apexes.

[0136] Examples of tires that can use the rubber composition and the crosslinked product of the rubber composition include pneumatic tires and non-pneumatic tires. Among these, pneumatic tires are preferred. For example, they can be suitably used as summer tires (summer tires) and winter tires (studless tires, snow tires, studded tires, etc.). Tires that can be used include passenger car tires, large passenger car tires, large SUV tires, heavy-duty tires for trucks and buses, light truck tires, motorcycle tires, run-flat tires, and racing tires (high-performance tires).

[0137] The rubber composition and the crosslinked product of the rubber composition can be used for purposes other than tires, such as packing, sheet members, hoses, belts, rubberized fabrics, footwear, and adhesives.

[0138] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0139] The physical properties of the unmodified liquid diene polymer and the modified liquid diene polymer were measured as follows.

[0140] <Weight-average molecular weight, number-average molecular weight, and molecular weight distribution> The weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the modified liquid diene polymer were determined by gel permeation chromatography (GPC) in terms of standard polystyrene equivalent molecular weight. The measurement device and conditions were as follows: Device: GPC device "HLC-8320GPC" manufactured by Tosoh Corporation Separation column: "TSKgel Super HZ4000 x 2" manufactured by Tosoh Corporation Eluent: tetrahydrofuran Eluent flow rate: 0.35 mL / min Sample concentration: 5 mg / 10 mL Column temperature: 40°C

[0141] <Amount of cis-1,4-bond units and amount of trans-1,4-bond units> 30 mg of each unmodified liquid diene polymer was dissolved in 10 mL of carbon disulfide and measured with a Fourier transform infrared spectrophotometer (FT-IR). The detected absorption peak absorbance (A Ｖ ), the absorption peak absorbance (A Ｃ ), the absorption peak absorbance (A Ｔ The composition ratio was calculated using the formula (i) from the absorption coefficient of Morero and the cis-1,4-bond (C)...1.7455*A Ｃ -0.0151*A Ｖ Trans-1,4-bond (T)...0.4292*A Ｔ -0.0129*A Ｖ -0.0454*A Ｃ 1.2-Bond (V)...0.3746*A Ｖ-0.007*A Ｃ Percentage of cis-1,4-bonds (%) = C / (C + V + T) * 100 Percentage of trans-1,4-bonds (%) = T / (C + V + T) * 100 Percentage of 1.2-bonds (%) = V / (C + V + T) * 100

[0142] <Average number of modifying groups represented by formula (I)> First, 50 mg of each unmodified liquid diene polymer was dissolved in 1 mL of deuterated chloroform, and the average number of modified groups was measured using an AVANCE 400 Nanobay (400 MHz) manufactured by Bruker Corporation, with 128 cumulative measurements. １ Next, 50 mg of each modified liquid diene polymer was dissolved in 1 mL of deuterated chloroform, and the H-NMR was measured using a Bruker "AVANCE 400 Nanobay" (400 MHz) with 128 accumulations. １ H-NMR was measured (Measurement 2). １ In the H-NMR spectrum, the peak integral values ​​of the peaks derived from 1,2-bonds and the peaks derived from 1,2-bonds and 1,4-bonds were calculated. １ In the H-NMR spectrum, the peak integration values ​​obtained in Measurement 1 were used to calculate the abundance ratio (X, Y, Z) (molar ratio) of the peak derived from 1,2-bonds, the peak derived from 1,4-bonds, and the peak derived from 2-aminoethanethiol from the ratio of the integration values. The number of monomers constituting the diene polymer was assumed from the weight-average molecular weight, and the approximate amount of functional groups in the amine-modified liquid diene polymer was calculated using the following formula: Average number of functional groups per molecule (functional groups / polymer) = Number of monomers * (Z / (X+Y))

[0143] <Amount of Structural Units Bonded with Modifying Groups / Amount of 1,2-Bond Units Having a Vinyl Group> Based on the molecular weight of the monomers constituting each modified liquid diene polymer and the weight-average molecular weight of the modified liquid diene polymer, the number of monomers constituting each modified liquid diene polymer was estimated, and the number of each bond unit was estimated. Based on these and the average number of modifying groups, the proportion (mol %) of structural units containing a modifying group relative to the total amount of structural units derived from butadiene (in the cases of the Examples and Comparative Examples, the total amount of 1,4-bond units, 1,2-bond units having a vinyl group, and structural units containing a modifying group) was calculated. Furthermore, based on the amount of 1,2-bond units in the unmodified liquid diene polymer, the proportion (mol %) of 1,2-bond units having a vinyl group relative to the total amount of structural units derived from butadiene in the modified liquid diene polymer was calculated.

[0144] <Melt Viscosity> The melt viscosity of the unmodified liquid diene polymer at 38°C was measured using a Brookfield viscometer (manufactured by BROOKFIELD ENGINEERING LABS. INC.).

[0145] 1. Synthesis of Unmodified Liquid Diene Polymer [Production Example 1: Synthesis of Diene Polymer 1] A thoroughly dried 3 L autoclave was purged with nitrogen, and 955 g of hexane and 21 g of n-butyllithium (17% by mass hexane solution) were charged. The temperature was raised to 60°C, and 770 g of butadiene was gradually added under stirring conditions to polymerize. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. Water was added to the resulting polymer solution, followed by stirring, and the polymer solution was washed with water. After stirring was stopped, separation of the polymer solution phase and the aqueous phase was confirmed, and the water was then separated. The polymer solution after washing was vacuum dried at 140°C for 3 hours to yield an unmodified liquid diene polymer 1 consisting of a butadiene homopolymer.

[0146] [Production Example 2: Synthesis of Diene Polymer 2] A thoroughly dried 3-L autoclave was purged with nitrogen, and 510 g of cyclohexane and 85 g of n-butyllithium (17% by mass hexane solution) were charged and heated to 50°C. 5 g of N,N,N',N'-tetramethylethylenediamine was then added, and 1,270 g of butadiene was gradually added under stirring conditions to polymerize while controlling the polymerization temperature to 50°C. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. Water was added to the resulting polymer solution, and the mixture was stirred. The polymer solution was washed with water. After stirring was stopped, it was confirmed that the polymer solution phase and the aqueous phase had separated, and then the water was separated. The polymer solution after washing was vacuum dried at 70°C for 24 hours to yield an unmodified liquid diene polymer 2 consisting of a butadiene homopolymer.

[0147] [Production Example 3: Synthesis of Diene Polymer 3] A thoroughly dried 5 L autoclave was purged with nitrogen, and 1200 g of hexane and 22.9 g of n-butyllithium (17 mass % hexane solution) were charged. 1260 g of butadiene was gradually added under stirring conditions to polymerize while controlling the polymerization temperature to 70°C. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. Water was added to the resulting polymer solution, followed by stirring, and the polymer solution was washed with water. After stirring was terminated, separation of the polymer solution phase and the aqueous phase was confirmed, and the water was then separated. The polymer solution after washing was vacuum dried at 70°C for 24 hours to yield an unmodified liquid diene polymer 3 consisting of a butadiene homopolymer.

[0148] [Production Example 4: Synthesis of Diene Polymer 4] A thoroughly dried 10 L autoclave was purged with nitrogen, and 4,520 g of hexane and 31.2 g of n-butyllithium (17% by mass hexane solution) were charged. 2,970 g of butadiene was gradually added under stirring conditions to polymerize while controlling the polymerization temperature to 70°C. 300 g of isoprene was further gradually added to polymerize, followed by addition of methanol to terminate the polymerization reaction, thereby obtaining a polymer solution. Water was added to the obtained polymer solution and stirred, and the polymer solution was washed with water. After stirring was stopped and it was confirmed that the polymer solution phase and the aqueous phase had separated, the water was separated. After washing, the polymer solution was vacuum dried at 70°C for 24 hours to obtain an unmodified liquid diene polymer 4 consisting of a copolymer of butadiene and isoprene.

[0149] The weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw / Mn), proportion of cis-1,4-bond units and proportion of trans-1,4-bond units in 1,4-bond units, and melt viscosity of the unmodified liquid diene polymers 1 to 4 obtained as described above were measured according to the methods described above. The results are shown in Table 1. The amount of structural units derived from butadiene in unmodified polymers 1 to 3 was 100% by mass based on the total amount of the polymer. In unmodified polymer 4, the amount of structural units derived from butadiene and structural units derived from isoprene was 90% by mass and 10% by mass, respectively, based on the total amount of the polymer.

[0150]

[0151] 2. Synthesis of Modified Liquid Diene Polymer [Production Example 5: Synthesis of Modified Liquid Diene Polymer 1-1] A thoroughly dried 1 L autoclave was purged with nitrogen, and 597 g of unmodified liquid diene polymer 1 was charged, followed by nitrogen degassing with stirring for 3 hours at 80° C. 1.5 g of 1,1-bis(t-hexylperoxy)cyclohexane and 5.1 g of 2-aminoethanethiol were added, and the mixture was reacted at 110° C. for 8 hours to obtain amine-modified liquid diene polymer 1-1.

[0152] [Production Example 6: Synthesis of modified liquid diene polymer 1-2] A thoroughly dried 1 L autoclave was purged with nitrogen, and 605 g of unmodified liquid diene polymer 1 was charged and degassed with nitrogen while stirring at 80°C for 3 hours. 1.9 g of 1,1-bis(t-hexylperoxy)cyclohexane and 12.7 g of 2-aminoethanethiol were added, and the reaction was carried out for 8 hours at 110°C. Thereafter, the reaction product was dissolved in 500 g of cyclohexane, and the solution was poured into 3,000 g of methanol for reprecipitation, thereby obtaining amine-modified liquid diene polymer 1-2.

[0153] [Production Example 7: Synthesis of modified liquid diene polymer 1-3] A thoroughly dried 1 L autoclave was purged with nitrogen, and 436 g of unmodified liquid diene polymer 1 and 187 g of toluene were charged. The mixture was stirred at 40°C to obtain a uniform polymer solution, which was then degassed with nitrogen for 3 hours. 1.6 g of 1,1-bis(t-hexylperoxy)cyclohexane and 10.1 g of 2-aminoethanethiol were added, and the mixture was reacted at 110°C for 8 hours. The reaction solution was then poured into 2000 g of methanol to cause reprecipitation, yielding modified liquid diene polymer 1-3.

[0154] Production Example 8: Synthesis of modified liquid diene polymer 2-1 A thoroughly dried 1 L autoclave was purged with nitrogen, and 607 g of unmodified liquid diene polymer 2 was charged and degassed with nitrogen while stirring at 60°C for 3 hours. 0.9 g of 1,1-bis(t-hexylperoxy)cyclohexane and 37.1 g of 2-aminoethanethiol were added, and the reaction was carried out for 8 hours at 110°C. The reaction product was then dissolved in 500 g of cyclohexane, and the solution was poured into 3,000 g of methanol for reprecipitation, yielding modified liquid diene polymer 2-1.

[0155] [Production Example 9: Synthesis of modified liquid diene polymer 2-2] A thoroughly dried 1 L autoclave was purged with nitrogen, and 125 g of unmodified liquid diene polymer 2 and 500 g of toluene were charged. The mixture was stirred at 40°C to obtain a uniform polymer solution, which was then degassed with nitrogen for 3 hours. 4.2 g of 1,1-bis(t-hexylperoxy)cyclohexane and 17.7 g of 2-aminoethanethiol were added, and the mixture was reacted at 110°C for 8 hours. The reaction solution was then poured into 2500 g of methanol for reprecipitation, yielding modified liquid diene polymer 2-2.

[0156] Production Example 10: Synthesis of modified liquid diene polymer 3-1 A thoroughly dried 1 L autoclave was purged with nitrogen, and 601 g of unmodified liquid diene polymer 3 was charged and degassed with nitrogen for 3 hours with stirring at 100°C. 1.4 g of 1,1-bis(t-hexylperoxy)cyclohexane and 4.5 g of 2-aminoethanethiol were added, and the mixture was reacted at 110°C for 8 hours. The reaction solution was then poured into 2500 g of methanol for reprecipitation, yielding modified liquid diene polymer 3-1.

[0157] [Production Example 11: Synthesis of modified liquid diene polymer 4-1] A thoroughly dried 1 L autoclave was purged with nitrogen, and 125 g of unmodified liquid diene polymer 4 and 594 g of toluene were charged, followed by nitrogen degassing for 3 hours with stirring at 100°C. 1.5 g of 1,1-bis(t-hexylperoxy)cyclohexane and 3.7 g of 2-aminoethanethiol were added, and the mixture was reacted at 110°C for 8 hours. The reaction solution was then poured into 2200 g of methanol for reprecipitation, yielding modified liquid diene polymer 4-1.

[0158] The weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw / Mn), proportion of 1,2-bond units having a vinyl group, proportion of cis-1,4-bond units, proportion of trans-1,4-bond units, average content of the modifying group represented by formula (1), and proportion of structural units having the modifying group represented by formula (1) of the modified liquid diene polymers 1-1 to 1-3, 2-1 to 2-2, 3-1, and 4-1 produced as described above were measured according to the methods described above. The results are shown in Table 2. In Table 2, proportion (a) is the proportion (mol %) of each bond unit relative to the total amount of structural units derived from butadiene in the modified liquid diene polymer, and proportion (b) is the proportion (mol %) of each bond unit relative to the total amount of 1,4-bond units in the modified liquid diene polymer. The structure of the modifying group represented by formula (1) is R １ =C ２ H ４ , R ２ =H.

[0159]

[0160] <Solid rubber> Solution polymerized styrene butadiene rubber: HPR355 (manufactured by ENEOS Material Corporation, alkoxysilyl group introduced at the end, styrene content 28% by mass, vinyl content 56% by mass) STR20: natural rubber produced in Thailand Butadiene rubber: BR01 (manufactured by ENEOS Material Corporation, Mw: 550,000, cis content 95% by mass)

[0161] <Silica / Silane Coupling Agent> Silica: ULTRASIL7000GR (manufactured by Evonik Japan, wet silica, average particle size 14 nm) Silane coupling agent: Si-75 (manufactured by Evonik Japan)

[0162] <Carbon black> N220: Diablack I (manufactured by Mitsubishi Chemical Corporation, average particle size 23 nm)

[0163] <Plasticizer> TDAE: VivaTec 500 (manufactured by H&R)

[0164] <Other ingredients> Zinc oxide: ZnO (manufactured by Sakai Chemical Industry Co., Ltd.) Stearic acid: Lunac S-20 (manufactured by Kao Corporation) Wax: Suntite S (manufactured by Seiko Chemical Co., Ltd.) Anti-aging agent: Nolac 6C (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Vulcanizing agent: Insoluble sulfur Myucron OT-20 (manufactured by Shikoku Chemical Industry Co., Ltd.) Vulcanization accelerator 1: Noccela CZ (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Vulcanization accelerator 2: Noccela D (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0165] [Examples 1 to 17 and Comparative Examples 1 to 9: Preparation of Rubber Compositions] According to the compounding ratios (parts by mass) listed in Tables 3, 4, and 5, solid rubber, polymer, filler, plasticizer, silane coupling agent, zinc oxide, stearic acid, wax, and antioxidant were each placed in an internal Banbury mixer and kneaded for 6 to 8 minutes to achieve a starting temperature of 60°C and a resin temperature of 145 to 160°C. The mixture was then removed from the mixer and cooled to room temperature. This mixture was then placed again in the internal Banbury mixer and kneaded for 4 to 6 minutes to achieve a starting temperature of 90°C and a resin temperature of 150°C. The mixture was then removed from the mixer and cooled to room temperature. The resulting mixture was then placed again in the Banbury mixer, and a vulcanizing agent and vulcanization accelerator were added. The mixture was kneaded for 75 seconds to achieve a starting temperature of 50°C and a final temperature of 75 to 95°C, yielding a rubber composition. The obtained rubber compositions were press-molded (150-170°C, 30-50 minutes) to prepare vulcanized rubber sheets (2 mm thick), and the physical properties were evaluated according to the following methods. The measurement methods for each evaluation were as follows. The obtained evaluation results are shown in Tables 3, 4, and 5.

[0166] <Rubber Hardness> Test pieces measuring 40 mm long x 5 mm wide were cut from vulcanized rubber sheets obtained by press-molding the rubber compositions prepared in the Examples and Comparative Examples, and hardness was measured using a Type A durometer in accordance with JIS K6253. To confirm the effect of the modified liquid diene polymer in improving rubber hardness, the rubber hardness values ​​shown in Tables 3, 4, and 5 are relative to the values ​​of Comparative Example 1 for Examples 1 and 2, Comparative Example 2 for Examples 3 and 4, Comparative Example 3 for Examples 5 to 7, Comparative Example 4 for Examples 8 and 9, Comparative Example 5 for Examples 10 and 12, Comparative Example 6 for Examples 13 and 14, Comparative Example 7 for Example 15, Comparative Example 8 for Example 16, and Comparative Example 9 for Example 17, all set to 100. The higher the value, the greater the hardness of the rubber composition, indicating improved hardness.

[0167] <Bleedout Suppression Effect> Three circular test pieces with a diameter of 32 mm were punched out from vulcanized rubber sheets obtained by press-molding the rubber compositions prepared in the Examples and Comparative Examples, and the weights (m1) of each were measured. A volume of toluene sufficient to completely immerse the test pieces was prepared, and the test pieces were immersed at room temperature for 48 hours. The test pieces were then removed and dried in a vacuum dryer at 80°C for 12 hours, and the weights (m2) of the dried test pieces were measured. The obtained weight measurements (m1, m2) were substituted into formula (ii) to determine the extraction ratio. Calculation formula (ii): Extraction rate (%) = (m1 - m2) / m1 * 100 In order to confirm the bleed-out suppression effect of the modified liquid diene polymer, the reciprocals of the extraction rates in the Examples and Comparative Examples were calculated, and the reciprocals of the extraction rates of Examples 1 and 2 correspond to Comparative Example 1, Examples 3 and 4 correspond to Comparative Example 2, Examples 5 to 7 correspond to Comparative Example 3, Examples 8 and 9 correspond to Comparative Example 4, Examples 10 and 12 correspond to Comparative Example 5, Examples 13 and 14 correspond to Comparative Example 6, Example 15 corresponds to Comparative Example 7, Example 16 corresponds to Comparative Example 8, and Example 17 corresponds to Comparative Example 9 are set to 100. The relative values ​​of the reciprocals of the extraction rates are shown in Tables 3, 4, and 5 as the bleed-out suppression effect. A higher value indicates less extractables and a higher bleed-out suppression effect.

[0168]

[0169]

[0170] <Evaluation of Dispersibility> The vulcanized rubber sheets obtained by press-molding the rubber compositions prepared in Comparative Example 2 and Example 3 were placed on a piece of paper with black letters printed on it, with the pressed surface of the resulting flat rubber sheet facing up, and photographed with a camera. The photographed image is shown in Figure 1. Whether the printed letters were visible in the image was evaluated according to the following criteria. Note that the higher the visibility of the letters, the higher the transparency of the rubber sheet, indicating improved dispersibility of components such as fillers contained in the rubber composition. The evaluation results were x for Comparative Example 2 and o for Example 3. (Evaluation criteria) o: Printed letters are visible x: Printed letters are not visible

[0171] As shown in Tables 3, 4, and 5, the rubber compositions containing the polymers of the present invention exhibited higher rubber hardness than rubber compositions containing diene polymers of comparable molecular weights and comparable amounts of filler. The higher rubber hardness is understood to be due to the polymers of the present invention improving the dispersibility of other components contained in the rubber composition, such as fillers. The results in FIG. 1 also show that the rubber compositions containing the polymers of the present invention have improved dispersibility of other components. Furthermore, as shown in Tables 3, 4, and 5, the polymers of the present invention not only have the above-mentioned dispersibility-improving effect, but also have a bleed-out suppressing effect.

Claims

1. A modified liquid diene-based polymer containing structural units derived from butadiene, The weight average molecular weight is 4,000 to 150,000, Formula (I): 【Chemistry 1】 [In the formula, R １ represents an alkylene group having 1 to 10 carbon atoms or a phenylene group, R ２ represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, * represents a bond. and a modifying group represented by A modified liquid diene polymer, wherein the amount of structural units derived from butadiene is 20 to 100% by mass based on the total amount of the modified liquid diene polymer, and the amount of 1,2-bond units having a vinyl group based on the total amount of structural units derived from butadiene is 0 to 70% by mole.

2. 2. The modified liquid diene polymer according to claim 1, wherein the average number of modifying groups represented by formula (I) is 0.5 to 10 per molecule of the modified liquid diene polymer.

3. 2. The modified liquid diene polymer according to claim 1, wherein the modified liquid diene polymer has no terminal hydroxyl groups.

4. 2. The modified liquid diene polymer according to claim 1, wherein the amount of cis-1,4-bond units relative to the total amount of 1,4-bond units in the structural units derived from butadiene is 20 to 60 mol %.

5. 2. The modified liquid diene polymer according to claim 1, wherein the amount of trans-1,4-bond units in the structural units derived from butadiene is 30 to 80 mol % based on the total amount of 1,4-bond units.

6. 2. The modified liquid diene polymer according to claim 1, which has a molecular weight distribution of 1.0 to 20.

0.

7. A rubber additive comprising the modified liquid diene polymer according to any one of claims 1 to 6.

8. The rubber additive according to claim 7, further comprising at least one selected from the group consisting of a plasticizer, an antioxidant, a filler, and a colorant.

9. The rubber additive according to claim 7, which is a solid rubber additive.

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