Methods for manufacturing rubber compositions, rubber crosslinkers, tires, and rubber crosslinkers

Abstract

A rubber composition is provided, in which the silica exhibits excellent dispersibility, resulting in excellent product stability and enabling the creation of a rubber crosslinker with low fuel consumption and excellent durability. A rubber composition is provided comprising a conjugated diene polymer, silica, a sulfide silane coupling agent, and a crosslinking agent, wherein the value of tc10, a vulcanization characteristic index measured using a vibration vulcanization testing machine according to JIS K6300-2, satisfies the following formula (1): 0.8 min < tc10 < 5.0 min (1)

Description

Technical Field

[0001] The present invention relates to a rubber composition, a cross-linked rubber product, a tire, and a method for producing the cross-linked rubber product. Prior Art

[0002] In recent years, with growing environmental concerns, polymers used in automotive tires are required to exhibit excellent fuel efficiency. Tires made from rubber compositions containing conjugated diene polymers blended with silica as a filler exhibit improved fuel efficiency compared to conventional rubber compositions containing carbon black, due to their lower heat buildup.

[0003] Patent Document 1 relates to a conjugated diene polymer used to make such a tire. It describes a conjugated diene rubber containing 5% by weight or more of a structure, wherein the structure is obtained by reacting a conjugated diene polymer chain with a modifier, wherein the structure comprises three or more of the conjugated diene polymer chains bonded through the modifier, wherein at least one end of the conjugated diene polymer chain has an isoprene block comprising 70% by weight or more of isoprene monomer units, and the other end is an active terminal, and the modifier has one or more of at least one of an epoxy group and a hydrocarbyloxysilyl group per molecule, wherein the total number of epoxy groups and the number of hydrocarbyloxy groups contained in the hydrocarbyloxysilyl group per molecule is three or more.

[0004] Patent Documents Patent Document 1: International Patent Publication No. 2011 / 105362 Summary of the Invention

[0005] However, given the increasing performance requirements for automotive tires in recent years, new rubber compositions are being developed that can produce tires with both excellent low heat buildup and superior durability. Furthermore, rubber compositions are also required to have excellent silica dispersibility, resulting in excellent product stability.

[0006] The present invention has been made in view of the above-mentioned problems, and its object is to provide a rubber composition having excellent silica dispersibility, thereby having excellent product stability, and capable of producing a rubber cross-linked product having low fuel consumption characteristics and excellent durability.

[0007] The inventors of the present invention have conducted intensive research to achieve the above object, and as a result, they have found that by containing a sulfur-based silane coupling agent in addition to a conjugated diene polymer, silica, and a crosslinking agent, and controlling the value of tc10, which is an index of vulcanization characteristics, within a specific range, the above object can be achieved, thus completing the present invention.

[0008] That is, according to the present invention, the following rubber compositions can be provided.

[0009] [1] A rubber composition containing a conjugated diene polymer, silica, a sulfur-based silane coupling agent, and a crosslinking agent, wherein the value of tc10, which is an index of vulcanization characteristics, measured using a vibration vulcanization tester in accordance with JIS K6300-2, satisfies the following formula (1). 0.8 minutes < tc10 < 5.0 minutes (1)

[0010] [2] The rubber composition according to [1], wherein the conjugated diene polymer contains 25 to 99.9% by weight of 1,3-butadiene units, 0.1 to 15% by weight of isoprene monomer units, and 0 to 60% by weight of aromatic vinyl monomer units.

[0011] [3] The rubber composition according to [1] or [2], wherein the conjugated diene polymer contains 40 to 96.9% by weight of 1,3-butadiene units, 0.1 to 10% by weight of isoprene monomer units, and 3 to 50% by weight of aromatic vinyl monomer units.

[0012] [4] The rubber composition according to any one of [1] to [3], wherein the conjugated diene polymer contains an isoprene block containing 80 to 100% by weight of isoprene monomer units.

[0013] [5] The rubber composition according to any one of [1] to [4], wherein the conjugated diene polymer contains a silicon atom-containing functional group formed from a siloxane compound.

[0014] Moreover, according to the present invention, the following rubber crosslinked products and tires can be provided.

[0015] [6] A rubber crosslinked product obtained by crosslinking the rubber composition according to any one of [1] to [5].

[0016] [7] A tire comprising the rubber crosslinked product according to [6].

[0017] In addition, the present invention can provide the following method for producing a cross-linked rubber.

[0018] [8] A method for producing a rubber cross-linked product, comprising the steps of mixing a conjugated diene polymer, silica, a sulfur-based silane coupling agent, and a cross-linking agent, and then leaving the mixture to stand at room temperature for 1 to 21 days to obtain a rubber composition, and the step of cross-linking the rubber composition.

[0019] [9] A method for producing a rubber cross-linked product as described in [8], wherein the conjugated diene polymer comprises 25 to 99.9 wt% of 1,3-butadiene units, 0.1 to 15 wt% of isoprene monomer units, and 0 to 60 wt% of aromatic vinyl monomer units.

[0020]

[10] A method for producing a rubber cross-linked product as described in [8] or [9], wherein the conjugated diene polymer comprises 40 to 96.9 wt% of 1,3-butadiene units, 0.1 to 10 wt% of isoprene monomer units, and 3 to 50 wt% of aromatic vinyl monomer units.

[0021]

[11] A method for producing a rubber cross-linked product as described in any one of [8] to

[10] , wherein the conjugated diene polymer comprises an isoprene-containing block containing 80 to 100% by weight of isoprene monomer units.

[0022]

[12] A method for producing a rubber cross-linked product as described in any one of [8] to

[11] , wherein the conjugated diene polymer contains a silicon atom-containing functional group formed from a siloxane compound.

[0023] According to the present invention, a rubber composition can be provided which has excellent silica dispersibility, thereby having excellent product stability, and can produce a rubber cross-linked product having low fuel consumption characteristics and excellent durability. Simple diagram description

[0024] none Implementation Method

[0025] Rubber composition

[0026] The rubber composition of the present invention contains a conjugated diene polymer, silica, a sulfur-based silane coupling agent, and a crosslinking agent, and the value of tc10, which is an index of vulcanization characteristics measured using a vibration vulcanization tester in accordance with JIS K6300-2, satisfies the following formula (1). 0.8 minutes < tc10 < 5.0 minutes (1)

[0027] According to the rubber composition of the present invention, by containing a sulfur-based silane coupling agent in addition to the conjugated diene polymer, silica, and crosslinking agent, and controlling the value of tc10, which is an index of vulcanization characteristics, within the above-defined range, it is possible to exhibit excellent effects such as "simultaneously achieving excellent product stability accompanied by excellent dispersibility of silica and excellent low fuel consumption characteristics and durability of the obtained rubber crosslinked product".

[0028] [Conjugated diene polymer]

[0029] The rubber composition of the present invention contains a conjugated diene polymer as a rubber component.

[0030] The conjugated diene polymer used in the present invention contains at least conjugated diene monomer units. Examples of the conjugated diene compound used to form the conjugated diene monomer units include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. These conjugated diene compounds can be used alone or in combination of two or more.

[0031] When the conjugated diene polymer used in the present invention contains 1,3-butadiene units, the content of the 1,3-butadiene units is not particularly limited, but it is preferably 25 to 99.9% by weight, more preferably 40 to 96.9% by weight, still more preferably 47 to 89.8% by weight, and particularly preferably 53 to 79.8% by weight. By the content of the 1,3-butadiene units being within the above range, the balance between the dispersibility of silica and the low fuel consumption characteristics and durability of the obtained rubber crosslinked product can be further improved.

[0032] When the conjugated diene polymer used in the present invention contains isoprene monomer units, the isoprene monomer unit content is not particularly limited, but is preferably 0.1-15% by weight, more preferably 0.1-10% by weight, more preferably 0.2-5% by weight, and particularly preferably 0.2-2% by weight. By keeping the isoprene monomer unit content within this range, the balance between silica dispersibility and the resulting cross-linked rubber's low fuel consumption and durability can be further improved.

[0033] The content of the conjugated diene monomer units in the conjugated diene polymer (or the total content of multiple conjugated diene monomer units if the polymer contains such units) is not particularly limited, but is preferably 40-100% by weight, more preferably 50-97% by weight, even more preferably 52-90% by weight, and particularly preferably 55-80% by weight. By keeping the conjugated diene monomer unit content within this range, the balance between silica dispersibility and the resulting cross-linked rubber's low fuel consumption and durability can be further improved.

[0034] The vinyl bond content of the conjugated diene monomer units in the conjugated diene polymer is preferably 1-90 mol%, more preferably 10-80 mol%, more preferably 20-70 mol%, even more preferably 24-60 mol%, even more preferably 26-50 mol%, and most preferably 28-44 mol%. By keeping the vinyl bond content of the conjugated diene monomer units within this range, the silica dispersibility and the balance between the low fuel consumption and durability of the resulting cross-linked rubber can be further improved.

[0035] Furthermore, the conjugated diene polymer used in the present invention is preferably a copolymer containing aromatic vinyl monomer units in addition to conjugated diene monomer units. Examples of aromatic vinyl monomers used to form the aromatic vinyl monomer units include styrene, methylstyrene, ethylstyrene, tertiary butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylaminomethylstyrene, dimethylaminoethylstyrene, diethylaminomethylstyrene, diethylaminoethylstyrene, cyanoethylstyrene, and vinylnaphthalene. Among these, styrene is preferred. These aromatic vinyl monomers may be used alone or in combination of two or more.

[0036] The content of aromatic vinyl monomer units in the conjugated diene polymer is not particularly limited, but is preferably 0-60% by weight, more preferably 3-50% by weight, even more preferably 10-48% by weight, and particularly preferably 20-45% by weight. By keeping the content of aromatic vinyl monomer units within this range, the silica dispersibility and the balance between the low fuel consumption and durability of the resulting cross-linked rubber can be further improved.

[0037] Furthermore, the conjugated diene polymer used in the present invention may contain, in addition to the conjugated diene monomer units and, if necessary, the aromatic vinyl monomer units, units of vinyl compounds containing functional groups capable of interacting with silica.

[0038] The vinyl compound containing a functional group capable of interacting with silica used to form the unit containing the vinyl compound containing a functional group capable of interacting with silica is not particularly limited as long as it contains a functional group capable of interacting with silica and a vinyl group. For example, the compounds described in International Patent Publication No. 2019 / 073828 can be used.

[0039] Here, a functional group capable of interacting with silica refers to a functional group capable of forming a covalent bond or an intermolecular force weaker than a covalent bond (e.g., ion-dipole interaction, dipole-dipole interaction, hydrogen bonding, van der Waals forces, etc.) between the functional group and the silica surface. Such functional groups capable of interacting with silica are not particularly limited, but include nitrogen-containing functional groups, silicon-containing functional groups, and oxygen-containing functional groups. Among these, silicon-containing functional groups are preferred due to their high interaction with silica.

[0040] The content ratio of the vinyl compound units containing functional groups capable of interacting with silica in the conjugated diene polymer is preferably 0.001 to 10.000 weight %, and more preferably 0.001 to 3.000 weight %, based on the total weight of all monomers as 100 weight %.

[0041] Furthermore, conjugated diene polymers may contain other monomer units in addition to the aforementioned monomer units. Examples of other compounds constituting such other monomer units include: chain olefin compounds such as ethylene, propylene, and 1-butene; cyclic olefin compounds such as cyclopentene and 2-northene; and non-conjugated diene compounds such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-northene. The content of these other monomer units in the conjugated diene polymer is preferably 30% by weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less.

[0042] The bonding forms of the monomer units in the conjugated diene polymer can be various, such as block, tapered, and random bonding forms.

[0043] The conjugated diene polymer used in the present invention preferably comprises an isoprene-containing block (A). It is more preferred that one end of the conjugated diene polymer comprises an isoprene-containing block (A) or both ends of the conjugated diene polymer comprise isoprene-containing blocks (A). It is particularly preferred that at least one end of the conjugated diene polymer comprises an isoprene-containing block (A).

[0044] The isoprene-containing block (A) may be a polymer block composed of isoprene monomer units or a polymer block containing only isoprene monomer units. The content of isoprene monomer units in the isoprene-containing block (A) is preferably 80-100% by weight, more preferably 85-99% by weight, more preferably 88-97% by weight, and particularly preferably 90-95% by weight. By keeping the content of isoprene monomer units in the isoprene-containing block (A) within the above range, the affinity of the conjugated diene polymer with silica can be further enhanced, the dispersibility of silica can be further improved, and the product stability can be further improved. Furthermore, the low fuel consumption characteristics and durability of the resulting cross-linked rubber can be further enhanced.

[0045] The vinyl bond content of the isoprene monomer units in the isoprene-containing block (A) is preferably 1-90 mol%, more preferably 3-80 mol%, and even more preferably 5-70 mol%. By keeping the vinyl bond content of the isoprene monomer units within this range, the silica dispersibility and the balance between the low fuel consumption characteristics and durability of the resulting cross-linked rubber can be further improved. In this specification, the vinyl bond content of the isoprene monomer units refers to the ratio of the total amount of isoprene monomer units having a 1,2-structure and isoprene monomer units having a 3,4-structure in the isoprene monomer units.

[0046] The isoprene-containing block (A) preferably contains aromatic vinyl monomer units in addition to isoprene monomer units. Examples of aromatic vinyl monomers used to form the aromatic vinyl monomer units include those mentioned above, with styrene being preferred. These aromatic vinyl monomers may be used alone or in combination of two or more.

[0047] The content of the aromatic vinyl monomer units in the isoprene-containing block (A) is preferably 0-20% by weight, more preferably 1-15% by weight, even more preferably 3-12% by weight, and particularly preferably 5-10% by weight. By keeping the content of the aromatic vinyl monomer units in the isoprene-containing block (A) within this range, the balance between silica dispersibility and the resulting rubber cross-linked product's low fuel consumption and durability can be further improved.

[0048] The isoprene-containing block (A) is preferably composed solely of isoprene monomer units or solely of isoprene monomer units and aromatic vinyl monomer units, and is particularly preferably composed solely of isoprene monomer units and aromatic vinyl monomer units. However, other monomer units may be contained as desired in addition to isoprene monomer units and aromatic vinyl monomer units, as long as the essential properties of the present invention are not impaired. Examples of other monomers constituting the monomer units include conjugated diene monomers other than isoprene, such as 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Examples include the vinyl compounds containing a functional group capable of interacting with silica, which are mentioned above, and the other compounds mentioned above, which are mentioned above, as other monomer units. These other monomers may be used alone or in combination of two or more. The content of the other monomer units in the isoprene-containing block (A) is preferably 15% by weight or less, more preferably 10% by weight or less, and even more preferably 6% by weight or less.

[0049] The weight average molecular weight (Mw) of the isoprene-containing block (A), as measured by gel permeation chromatography (GPC), is preferably 500-15,000, more preferably 1,000-12,000, and particularly preferably 1,500-10,000. By keeping the weight average molecular weight of the isoprene-containing block (A) within this range, silica dispersion can be further improved, thereby further enhancing product stability and further improving the fuel efficiency and durability of the resulting cross-linked rubber.

[0050] Furthermore, the molecular weight distribution of the isoprene-containing block (A), represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn), is preferably 1.0 to 1.5, more preferably 1.0 to 1.3. When the molecular weight distribution (Mw / Mn) of the isoprene-containing block (A) is within the above range, the production of the conjugated diene polymer becomes easier.

[0051] When the conjugated diene polymer includes an isoprene-containing block (A), it is preferred that the conjugated diene polymer further include a butadiene-containing block (B), and more preferably, the isoprene-containing block (A) and the butadiene-containing block (B) are formed continuously. By using a conjugated diene polymer having such a block structure, the affinity of the conjugated diene polymer with silica can be further improved, and the dispersibility of silica can be further enhanced, thereby further improving product stability and the low fuel consumption characteristics and durability of the resulting cross-linked rubber.

[0052] The butadiene-containing block (B) is a polymer block comprising 1,3-butadiene units. The content of 1,3-butadiene units in the butadiene-containing block (B) is not particularly limited, but is preferably 30-100% by weight, more preferably 35-95% by weight, even more preferably 40-90% by weight, even more preferably 45-80% by weight, and most preferably 50-70% by weight. By maintaining the 1,3-butadiene content within this range, silica dispersibility can be further improved, and the resulting cross-linked rubber can achieve a balanced balance between low fuel consumption and durability.

[0053] The vinyl bond content in the 1,3-butadiene units of the butadiene-containing block (B) is preferably 1-90 mol%, more preferably 3-80 mol%, and even more preferably 5-70 mol%. By keeping the vinyl bond content in the 1,3-butadiene units within this range, silica dispersibility can be further improved, and the resulting cross-linked rubber can achieve a balanced balance between low fuel consumption and durability.

[0054] The butadiene-containing block (B) preferably contains, in addition to 1,3-butadiene units, aromatic vinyl monomer units and / or isoprene monomer units, and particularly preferably contains aromatic vinyl monomer units. Examples of aromatic vinyl monomers used to form the aromatic vinyl monomer units include those mentioned above, with styrene being preferred. These aromatic vinyl monomers may be used alone or in combination of two or more.

[0055] The content of the aromatic vinyl monomer units in the butadiene-containing block (B) is not particularly limited, but is preferably 0-70% by weight, more preferably 5-65% by weight, even more preferably 10-60% by weight, particularly preferably 15-55% by weight, particularly preferably 20-55% by weight, and most preferably 30-50% by weight. By keeping the content of the aromatic vinyl monomer units within this range, the silica dispersibility and the balance between the low fuel consumption characteristics and durability of the resulting cross-linked rubber can be further improved.

[0056] The content of isoprene monomer units in the butadiene-containing block (B) is not particularly limited, but the upper limit is preferably 10% by weight or less, more preferably 9% by weight or less, and even more preferably 7% by weight or less. Furthermore, when the butadiene-containing block (B) contains isoprene monomer units, the lower limit of the content is preferably 0.1% by weight or more, more preferably 1% by weight or more, and even more preferably 2% by weight or more. By keeping the isoprene monomer unit content within this range, the balance between silica dispersibility and the resulting rubber cross-linked product's low fuel consumption and durability can be further improved.

[0057] The butadiene-containing block (B) is preferably composed solely of 1,3-butadiene monomer units and aromatic vinyl monomer units, or is preferably composed solely of 1,3-butadiene monomer units, aromatic vinyl monomer units, and isoprene monomer units. It is particularly preferably composed solely of 1,3-butadiene monomer units and aromatic vinyl monomer units. However, as long as the essential properties of the present invention are not impaired, the block (B) may contain other monomer units in addition to 1,3-butadiene monomer units and aromatic vinyl monomer units as desired. Examples of other monomers used to constitute the other monomer units include conjugated diene monomers other than 1,3-butadiene, such as isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene; α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids or anhydrides such as acrylic acid, methacrylic acid, and maleic anhydride; unsaturated carboxylic acid esters such as methyl methacrylate, ethyl acrylate, and butyl acrylate; and non-conjugated dienes such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-northene. These other monomers can be used alone or in combination of two or more. The content of the other monomer units in the butadiene-containing block (B) is preferably 15% by weight or less, more preferably 10% by weight or less, and even more preferably 6% by weight or less.

[0058] When the conjugated diene polymer used in the present invention comprises an isoprene-containing block (A) and a butadiene-containing block (B), the weight ratio of the isoprene-containing block (A) to the butadiene-containing block (B) (when multiple isoprene-containing blocks (A) and butadiene-containing blocks (B) are present, the weight ratio is based on the total weight of each) as calculated as (weight of the isoprene-containing block (A)) / (weight of the butadiene-containing block (B)) in the range of 0.001 to 0.1, more preferably 0.003 to 0.070, and even more preferably 0.005 to 0.05. By keeping the weight ratio of the isoprene-containing block (A) to the butadiene-containing block (B) within the above range, the resulting cross-linked rubber can have a good balance between strength and low heat buildup.

[0059] Furthermore, the conjugated diene polymer used in the present invention preferably contains a modified group formed by a modifier at the end of the polymer chain. In other words, the conjugated diene polymer used in the present invention preferably contains a modified group formed by a modifier.

[0060] From the perspective of further enhancing silica affinity and silica dispersibility, thereby improving product stability and the resulting rubber cross-linked product's fuel economy and durability, a modifier containing a silica-interactive functional group is preferred. Here, a silica-interactive functional group is one that can form a covalent bond or an intermolecular force weaker than a covalent bond (e.g., ion-dipole interaction, dipole-dipole interaction, hydrogen bonding, van der Waals forces, etc.) between the functional group and the silica surface. Such silica-interactive functional groups are not particularly limited, but include nitrogen-containing functional groups, silicon-containing functional groups, and oxygen-containing functional groups.

[0061] As modifiers for forming modifying groups, silicon-containing modifiers and nitrogen-containing modifiers having nitrogen-containing functional groups are preferred due to their high interaction with silica, with silicon-containing modifiers being particularly preferred. In other words, the conjugated diene polymers used in the present invention preferably contain silicon-containing functional groups formed by silicon-containing modifiers or nitrogen-containing functional groups formed by nitrogen-containing modifiers, with silicon-containing functional groups formed by silicon-containing modifiers being particularly preferred. Examples of silicon-containing modifiers include siloxane compounds and hydrocarbyloxysilane compounds. Examples of nitrogen-containing modifiers include dimethylaminoethylacrylamide, diethylaminoethylacrylamide, dimethylaminopropylacrylamide, diethylaminopropylacrylamide, dimethylaminobutylacrylamide, diethylaminobutylacrylamide, (dimethylaminoethyl)methacrylamide, (diethylaminoethyl)methacrylamide, (dimethylaminopropyl)methacrylamide, (diethylaminopropyl)methacrylamide, (dimethylaminobutyl)methacrylamide, and N,N-disubstituted aminoalkyl (methyl)acrylamide. Acrylamides; amino group-containing alkoxysilane compounds such as [3-(dimethylamino)propyl]trimethoxysilane, [3-(diethylamino)propyl]trimethoxysilane, [3-(dimethylamino)propyl]triethoxysilane, [3-(diethylamino)propyl]triethoxysilane, [3-(methylethylamino)propyl]trimethoxysilane, and [3-(methylethylamino)propyl]triethoxysilane; pyrrolidone compounds such as N-phenyl-2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and 1-cyclohexyl-2-pyrrolidone.

[0062] The conjugated diene polymer used in the present invention preferably contains a silicon-containing functional group formed from a siloxane compound as a silicon-containing modifier. The siloxane compound is not particularly limited as long as it has a siloxane structure (-Si-O-) as its main chain structure, but is preferably an organosiloxane having an organic group in its side chain, and more preferably a polyorganosiloxane represented by the following general formula (4).

[0063] "Chemistry 1"

[0064] In the above general formula (4), R3 to R10 are alkyl groups having 1 to 6 carbon atoms or aryl groups having 6 to 12 carbon atoms, and these groups may be the same or different. X9 and X12 are any group selected from the group consisting of alkyl groups having 1 to 6 carbon atoms, aryl groups having 6 to 12 carbon atoms, alkoxy groups having 1 to 5 carbon atoms, and groups having 4 to 12 carbon atoms containing an epoxy group, and these groups may be the same or different. X10 is an alkoxy group having 1 to 5 carbon atoms or a group having 4 to 12 carbon atoms containing an epoxy group. When there are multiple X10s, these groups may be the same or different. X11 is a group containing 2 to 20 repeating units of alkanediol. When there are multiple X11s, these groups may be the same or different. m is an integer from 0 to 200, n is an integer from 0 to 200, k is an integer from 0 to 200, and m+n+k is 1 or greater.

[0065] In the polyorganosiloxane represented by the general formula (4), examples of the alkyl groups having 1 to 6 carbon atoms constituting R 3 to R 10 , X 9 , and X 12 in the general formula (4) include methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and cyclohexyl. Examples of the aryl groups having 6 to 12 carbon atoms include phenyl and tolyl. Among these, methyl and ethyl groups are preferred from the perspective of ease of production of the polyorganosiloxane itself.

[0066] Furthermore, in the polyorganosiloxane represented by the general formula (4), examples of the alkoxy group having 1 to 5 carbon atoms constituting X9, X10, and X12 include methoxy, ethoxy, propoxy, isopropoxy, and butoxy. Among these, methoxy and ethoxy groups are preferred from the perspective of ease of production of the polyorganosiloxane itself.

[0067] Furthermore, in the polyorganosiloxane represented by the general formula (4), as the carbon number 4-12 group containing an epoxy group constituting X9, X10, and X12, there can be mentioned, for example, a group represented by the following general formula (5). -Z 1-Z 2-E 1(5)

[0068] In the above general formula (5), Z 1 is an alkylene group or an alkylarylene group having 1 to 10 carbon atoms, Z 2 is a methylene group, a sulfur atom or an oxygen atom, and E 1 is a hydrocarbon group having 2 to 10 carbon atoms and having an epoxy group.

[0069] As the group represented by the general formula (5), Z2 is preferably an oxygen atom, more preferably Z2 is an oxygen atom and E1 is an epoxypropyl group, and particularly preferably Z1 is an alkylene group having 1 to 3 carbon atoms, or Z2 is an oxygen atom and E1 is an epoxypropyl group.

[0070] Furthermore, in the polyorganosiloxane represented by the general formula (4), X9 and X12 are preferably a group having 4 to 12 carbon atoms or an alkyl group having 1 to 6 carbon atoms among those mentioned above. Furthermore, X10 is preferably a group having 4 to 12 carbon atoms and an epoxy group among those mentioned above. Furthermore, it is more preferred that X9 and X12 are an alkyl group having 1 to 6 carbon atoms, and X10 is a group having 4 to 12 carbon atoms and an epoxy group.

[0071] Furthermore, in the polyorganosiloxane represented by the general formula (4), X 11, i.e., the group containing 2 to 20 repeating units of alkanediol, is preferably a group represented by the following general formula (6).

[0072] "Chemistry 2"

[0073] In the above general formula (6), a is an integer of 2 to 20, X 13 is an alkylene group or an alkylarylene group having 2 to 10 carbon atoms, R 11 is a hydrogen atom or a methyl group, and X 14 is an alkoxy group or an aryloxy group having 1 to 10 carbon atoms. Among these, a is preferably an integer of 2 to 8, X 13 is an alkylene group having 3 carbon atoms, R 11 is a hydrogen atom, and X 14 is a methoxy group.

[0074] In the polyorganosiloxane represented by the general formula (4), m is an integer of 0 to 200, preferably an integer of 20 to 150, and more preferably an integer of 30 to 120. If m is 200 or less, the polyorganosiloxane represented by the general formula (4) can be manufactured more easily, and its viscosity will not become too high, making it easier to handle.

[0075] Furthermore, in the polyorganosiloxane represented by the general formula (4), n is an integer of 0 to 200, preferably an integer of 0 to 150, and more preferably an integer of 0 to 120. k is an integer of 0 to 200, preferably an integer of 0 to 150, and more preferably an integer of 0 to 130. The total number of m, n, and k is 1 or more, preferably 2 to 400, more preferably 20 to 300, and even more preferably 30 to 250. If the total number of m, n, and k is 1 or more, the reaction between the polyorganosiloxane represented by the general formula (4) and the active end of the conjugated diene polymer will proceed more easily during the production process of the conjugated diene polymer. Furthermore, if the total number of m, n, and k is 400 or less, the production of the polyorganosiloxane represented by the general formula (4) itself will be easier, and its viscosity will not become too high, and the handling will also be easier.

[0076] As the modifier for forming the modifying group, a nitrogen-containing modifier having a nitrogen-containing functional group may be used, and for example, a hydrocarbyloxysilane compound containing a nitrogen atom may be used.

[0077] The nitrogen-containing hydrocarbyloxysilane compound is a silicon-containing compound having at least one nitrogen-containing group and at least one hydrocarbyloxy group. The nitrogen-containing hydrocarbyloxysilane compound is not particularly limited, but compounds described in International Patent Publication No. 2019 / 189204 can be used.

[0078] The weight-average molecular weight (Mw) of the conjugated diene polymer used in the present invention is not particularly limited, but is preferably 50,000 to 5,000,000, more preferably 75,000 to 3,000,000, and particularly preferably 100,000 to 1,000,000, based on polystyrene conversion as measured by gel permeation chromatography. A conjugated diene polymer with a weight-average molecular weight (Mw) within this range improves processability, silica dispersibility, and the balance between low fuel consumption and durability of the resulting cross-linked rubber.

[0079] The molecular weight distribution of the conjugated diene polymer used in the present invention, as indicated by the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn), is preferably 1.1-3.0, more preferably 1.2-2.5, and particularly preferably 1.2-2.2. By maintaining the molecular weight distribution (Mw / Mn) of the conjugated diene polymer within this range, processability can be improved, while silica dispersion can be further enhanced, and the resulting cross-linked rubber can achieve a balanced balance between low fuel consumption and durability.

[0080] The Mooney viscosity (ML1+4, 100°C) of the conjugated diene polymer used in the present invention is not particularly limited, but is preferably 10-200, more preferably 15-150, even more preferably 20-135, and particularly preferably 25-125. A Mooney viscosity within this range improves processability, silica dispersibility, and the balance between low fuel consumption and durability of the resulting cross-linked rubber. The Mooney viscosity (ML1+4, 100°C) is measured in accordance with JIS K6300-1.

[0081] From the perspective of operability, the conjugated diene polymer used in the present invention can be preferably used mixed with an extender oil, described below. When the conjugated diene polymer is used mixed with an extender oil, the Muni viscosity (ML1+4) of the conjugated diene polymer mixed with the extender oil (the oil-extended conjugated diene polymer) can be determined as the Muni viscosity (ML1+4) of the conjugated diene polymer. The appropriate range and measurement conditions for the Muni viscosity (ML1+4) in this case are the same as those described above.

[0082] The rubber composition of the present invention may contain a single conjugated diene polymer or two or more conjugated diene polymers. The rubber composition of the present invention preferably contains a solution-polymerized styrene-butadiene-isoprene copolymer rubber and a conjugated diene polymer other than the solution-polymerized styrene-butadiene-isoprene copolymer rubber as the conjugated diene polymer. Furthermore, the solution-polymerized styrene-butadiene-isoprene copolymer rubber is not particularly limited as long as it can be obtained by subjecting a monomer mixture containing styrene, 1,3-butadiene, and isoprene to solution polymerization.

[0083] Examples of other conjugated diene polymers other than solution-polymerized styrene-butadiene-isoprene copolymer rubber include natural rubber (which may also be modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), and grafted natural rubber), polyisoprene rubber, emulsion-polymerized styrene-butadiene copolymer rubber, polybutadiene rubber (which may also be high-cis BR or low-cis BR, and may also be polybutadiene rubber containing crystalline fibers made of 1,2-polybutadiene polymer), styrene-butadiene copolymer rubber, styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, acrylonitrile-butadiene copolymer rubber, acrylonitrile-styrene-butadiene copolymer rubber, butyl rubber (IIR), chloropin rubber, nitrile chloropin rubber, and nitrile isoprene rubber. Among these, polybutadiene rubber, natural rubber and styrene-butadiene copolymer rubber are preferred, with polybutadiene rubber being more preferred.

[0084] The conjugated diene polymer content in the rubber composition of the present invention is preferably 10-90% by weight, more preferably 20-70% by weight, and even more preferably 30-50% by weight. By maintaining the conjugated diene polymer content within this range, processability is improved, while also further enhancing the balance between fuel efficiency and durability of the resulting cross-linked rubber.

[0085] [Method for producing conjugated diene polymer]

[0086] The conjugated diene polymer used in the present invention can be obtained, for example, by polymerizing a monomer mixture containing at least a conjugated diene compound in an inert solvent using a polymerization initiator. The conjugated diene polymer used in the present invention is preferably obtained by solution polymerization.

[0087] The monomer mixture may contain any conjugated diene compound, and monomers corresponding to the monomer composition of the target conjugated diene polymer may be used.

[0088] The inert solvent used in the polymerization is commonly used in solution polymerization and is not particularly limited as long as it does not inhibit the polymerization reaction. Specific examples of inert solvents include: chain aliphatic hydrocarbons such as butane, pentane, hexane, heptane, and 2-butene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cyclohexene; and aromatic hydrocarbons such as benzene, toluene, and xylene. These inert solvents may be used alone or in combination of two or more. The amount of inert solvent used is, for example, an amount such that the monomer concentration is 1 to 50% by weight, preferably 10 to 40% by weight.

[0089] Furthermore, the polymerization initiator used in the polymerization is not particularly limited as long as it can polymerize the monomer mixture containing the conjugated diene compound. Specific examples include polymerization initiators using organic alkali metal compounds, organic alkaline earth metal compounds, and lanthanide metal compounds as primary catalysts. Examples of organic alkali metal compounds include organic lithium compounds, organic sodium compounds, and organic potassium compounds. Specifically, examples include organic monolithium compounds such as n-butyllithium, secondary butyllithium, tertiary butyllithium, hexyllithium, phenyllithium, and distyryl lithium; organic polylithium compounds such as dilithium methane, 1,4-dilithium butane, 1,4-dilithium-2-ethylcyclohexane, 1,3,5-trilithium benzene, and 1,3,5-tris(lithiomethyl)benzene; organic sodium compounds such as sodium naphthalene; and organic potassium compounds such as potassium naphthalene. Examples of organic alkaline earth metal compounds include di-n-butylmagnesium, di-n-hexylmagnesium, calcium diethoxide, calcium distearate, di(tertiary butyl)strontium, barium diethoxide, barium diisopropoxide, barium diethylmercaptobarium, di(tertiary butyl)barium, barium diphenoxide, barium diethylamino, barium distearate, and barium dicarbonyl radical. Examples of polymerization initiators using lanthanide metal compounds as the main catalyst include lanthanide metal salts formed from lanthanide metals such as lanthanum, cerium, vanadium, neodymium, samarium, and gadolinium with carboxylic acids and phosphorus-containing organic acids, and co-catalysts such as alkylaluminum compounds, organoaluminum hydrides, and organoaluminum halides. Among these polymerization initiators, organomodular lithium compounds and organopolylithium compounds are preferred, organomodular lithium compounds are more preferred, and n-butyllithium is particularly preferred. Alternatively, the organic alkali metal compound can be pre-reacted with a secondary amine compound such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, piperidine, hexamethyleneimine, and heptamethyleneimine to form an organic alkali metal amide compound. Using an organic alkali metal amide compound as a polymerization initiator can improve the low fuel consumption and mechanical strength of the resulting rubber cross-linked product. These polymerization initiators can be used alone or in combination of two or more.

[0090] The amount of the polymerization initiator used can be determined according to the molecular weight distribution curve of the target conjugated diene polymer, and is generally in the range of 1 to 50 mmol, preferably 1.5 to 20 mmol, and even more preferably 2 to 15 mmol, per 1000 g of monomer.

[0091] The polymerization temperature generally ranges from -80°C to +150°C, preferably from 0°C to 100°C, and even more preferably from 30°C to 90°C. The polymerization process can be either batch or continuous, but the batch process is preferred because it allows for easier control of the heterogeneity of the bonds between the conjugated diene monomer units and the aromatic vinyl monomer units.

[0092] Furthermore, when polymerizing a monomer mixture containing a conjugated diene compound, it is preferred to add a polar compound to an inert organic solvent to adjust the vinyl bond content of the conjugated diene monomer units in the resulting conjugated diene polymer. Examples of polar compounds include ether compounds such as dibutyl ether and tetrahydrofuran; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; and phosphine compounds. Of these, ether compounds and tertiary amines are preferred, with tertiary amines being particularly preferred, and tetramethylethylenediamine being particularly preferred. These polar compounds may be used alone or in combination of two or more. The amount of polar compound used is determined by the target vinyl bond content and is preferably 0.001 to 100 mol, and more preferably 0.01 to 10 mol, per 1 mol of the polymerization initiator. When the amount of polar compound used is within this range, the vinyl bond content of the conjugated diene monomer units can be easily adjusted and adverse effects caused by deactivation of the polymerization initiator are less likely to occur.

[0093] The conjugated diene polymer used in the present invention can also be produced by the following production method, which comprises: a step of polymerizing a monomer (a) containing isoprene in an inert solvent with a polymerization initiator to form an isoprene-containing block (A) having an active terminal; and a step of mixing the isoprene-containing block (A) having an active terminal with a monomer (b) containing 1,3-butadiene, and continuing the polymerization reaction to continuously form the isoprene-containing block (A) and the butadiene-containing block (B).

[0094] The monomer (a) for forming the isoprene-containing block (A) may be any monomer as long as it contains isoprene, and may be a monomer having a monomer composition corresponding to the isoprene-containing block (A) to be formed.

[0095] The inert solvent used to form the isoprene-containing block (A) can be the same as those described above. The amount of the inert solvent used is preferably such that the monomer concentration is 1 to 80% by weight, more preferably 10 to 50% by weight.

[0096] The polymerization initiator used to form the isoprene-containing block (A) is not particularly limited as long as it can polymerize the isoprene-containing monomer (a) to produce a polymer chain having an active terminal. Specifically, the same polymerization initiators as those described above can be used. The amount of the polymerization initiator used can be determined based on the target molecular weight, but is preferably in the range of 4 to 250 mmol, more preferably 6 to 200 mmol, and even more preferably 10 to 70 mmol per 100 g of the isoprene-containing monomer (a).

[0097] The polymerization temperature range for polymerizing the isoprene-containing monomer (a) is preferably -80°C to +150°C, more preferably 0°C to 100°C, and even more preferably 20°C to 90°C. The polymerization can be carried out in either a batch or continuous manner. Furthermore, when the isoprene-containing block (A) is formed into a copolymer chain, the bonding pattern of the monomers can be various, such as block, gradient, and random bonding patterns.

[0098] Furthermore, to adjust the vinyl bond content of the isoprene monomer units in the isoprene-containing block (A), it is preferred to add a polar compound to the inert solvent during polymerization. The polar compound can be the same as those described above. The amount of the polar compound used is determined based on the target vinyl bond content, preferably ranging from 0.01 to 30 moles, and more preferably from 0.05 to 10 moles, per 1 mole of the polymerization initiator. When the amount of the polar compound used is within this range, the vinyl bond content of the isoprene monomer units can be easily adjusted, and adverse effects caused by deactivation of the polymerization initiator are less likely to occur. Furthermore, by increasing the amount of the polar compound used within this range, the vinyl bond content of the isoprene monomer units can be increased.

[0099] The butadiene-containing block (B) can be formed continuously with the isoprene-containing block (A) by mixing the above-described isoprene-containing block (A) having active terminals with a monomer (b) containing 1,3-butadiene and continuing the polymerization reaction. The resulting butadiene-containing block (B) has active terminals. Meanwhile, the active terminals disappear from the isoprene-containing block (A).

[0100] The inert solvent used in the polymerization of the isoprene-containing block (A) and the monomer (b) containing 1,3-butadiene to form the butadiene-containing block (B) is not particularly limited, and the same inert solvents as those described above can be used.

[0101] The amount of the isoprene-containing block (A) having an active terminal used in forming the butadiene-containing block (B) can be determined according to the target molecular weight, but is preferably in the range of 0.1 to 5 mmol, more preferably 0.15 to 2 mmol, and even more preferably 0.2 to 1.5 mmol per 100 g of the monomer (b) containing 1,3-butadiene.

[0102] The method for mixing the isoprene-containing block (A) and the 1,3-butadiene-containing monomer (b) is not particularly limited. The isoprene-containing block (A) having an active terminal can be added to a solution of the 1,3-butadiene-containing monomer (b), or the 1,3-butadiene-containing monomer (b) can be added to a solution of the isoprene-containing block (A) having an active terminal. From the perspective of controlling polymerization, the method of adding the isoprene-containing block (A) having an active terminal to a solution of the 1,3-butadiene-containing monomer (b) is preferred.

[0103] When polymerizing the 1,3-butadiene-containing monomer (b), the polymerization temperature is preferably in the range of -80°C to +150°C, more preferably 0°C to 100°C, and even more preferably 20°C to 90°C. The polymerization can be carried out in either a batch or continuous manner. When the butadiene-containing block (B) is formed into a copolymer chain, a batch method is preferred because it facilitates control of the randomness of the bonds.

[0104] When the butadiene-containing block (B) is formed into a copolymer chain, the bonding pattern of the monomers can be various, such as block, gradient, and random. Of these, a random bonding pattern is preferred. A random bonding pattern further enhances the fuel efficiency of the resulting cross-linked rubber.

[0105] Furthermore, in one aspect of the present invention, to adjust the vinyl bond content of the 1,3-butadiene monomer units in the butadiene-containing block (B), it is preferred to add a polar compound to the inert solvent during polymerization, similar to the adjustment of the vinyl bond content of the isoprene monomer units in the isoprene-containing block (A). However, during the preparation of the isoprene-containing block (A), if a sufficient amount of the polar compound is added to the inert solvent to adjust the vinyl bond content of the 1,3-butadiene monomer units in the butadiene-containing block (B), the addition of the polar compound is not necessary. The polar compound used to adjust the vinyl bond content can be the same as those described above. The amount of polar compound used can be determined based on the target vinyl bond content and can be adjusted within a range of 0.01 to 100 mol, more preferably 0.1 to 30 mol, relative to 1 mol of the polymerization initiator used in the initial polymerization reaction (the polymerization reaction to form the first isoprene-containing block (A)). When the amount of polar compound used is within this range, the vinyl bond content in the 1,3-butadiene monomer units can be easily adjusted and adverse effects caused by inactivation of the polymerization initiator are less likely to occur.

[0106] In this way, a polymer chain having active terminals, including an isoprene-containing block (A) and a butadiene-containing block (B), can be obtained. From the perspective of productivity, a polymer chain having active terminals preferably consists of an isoprene-containing block (A) and a butadiene-containing block (B), with the terminal of the butadiene-containing block (B) being the active terminal. However, a polymer chain having multiple isoprene-containing blocks (A) or having other polymer blocks can also be used. For example, a polymer chain having active terminals such as an isoprene-containing block (A)-butadiene-containing block (B)-isoprene-containing block (A) can be used. In this case, the active terminal is formed at the terminal of the isoprene-containing block (A) formed subsequent to the butadiene-containing block (B). When the isoprene-containing block (A) is formed on the active terminal side of the conjugated diene polymer, the amount of isoprene used is preferably 10 to 100 mol, more preferably 15 to 70 mol, and particularly preferably 20 to 35 mol, relative to 1 mol of the polymerization initiator used in the initial polymerization reaction (polymerization reaction for forming the first isoprene-containing block (A)).

[0107] By the above operation, a conjugated diene polymer chain can be obtained in an inert solvent. Moreover, the conjugated diene polymer chain obtained by such operation usually has an active end.

[0108] Conjugated diene polymer chains containing active terminals can also be reacted with a coupling agent to form coupled polymer chains. The coupling agent is not particularly limited, but examples thereof include: silane tetrachloride, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, tin tetrachloride, methyltrichlorotin, dimethyldichlorotin, trimethylchlorotin, tetramethoxysilane, methyltrimethoxysilane, dimethoxydimethylsilane, methyltriethoxysilane, ethyltrimethoxysilane, dimethoxydiethylsilane, and methyltriethoxysilane. Silane, diethoxydimethylsilane, tetraethoxysilane, ethyltriethoxysilane, diethoxydiethylsilane, bis(trichlorosilyl)methane, 1,2-bis(trichlorosilyl)ethane, 1,3-bis(trichlorosilyl)propane, 1,4-bis(trichlorosilyl)butane, 1,5-bis(trichlorosilyl)pentane, 1,6-bis(trichlorosilyl)hexane, etc. Furthermore, among the above-mentioned modifiers, those with coupling properties are preferably used as coupling agents. The coupling agent can be selected based on the molecular weight distribution curve of the target conjugated diene polymer. A coupling agent with a trifunctional or higher functionality is preferred, and a coupling agent with a tetrafunctional or higher functionality is even more preferred.

[0109] When a coupling agent is used, it is preferred to perform a coupling reaction on a portion of the polymer chains with active ends obtained by the above-described polymerization method, thereby forming coupled polymer chains and obtaining a solution containing polymer chains with active ends and coupled polymer chains. In this case, the amount of coupling agent used is not particularly limited and can be selected based on the molecular weight distribution curve of the target conjugated diene polymer. However, the amount, calculated based on the functional groups of the coupling agent, is preferably 0.01-0.4 mol, and more preferably 0.02-0.3 mol, per 1 mol of the polymerization initiator used at the start of polymerization. The addition of the coupling agent causes the polymer chains with active ends to undergo a coupling reaction at the active ends, thereby eliminating the active ends of the polymer chains that have undergone the coupling reaction, leaving them without active ends, while the active ends of the polymer chains that have not undergone the coupling reaction remain intact.

[0110] Preferably, the modifier reacts with the active ends of the conjugated diene polymer chains obtained by polymerization or the active ends of the conjugated diene polymer chains after the coupling reaction, thereby converting the conjugated diene polymer into a conjugated diene polymer having a modified group. The modifiers described above for forming modified groups in the conjugated diene polymer used in the present invention can be used.

[0111] The amount of the modifier used when reacting the above-mentioned modifier with the active ends of the conjugated diene polymer chain is not particularly limited, but is preferably 0.01 to 10.0 mol, more preferably 0.02 to 5.0 mol, and even more preferably 0.05 to 2.0 mol, based on 1 mol of the modifier relative to the active ends of the polymer chain having active ends (when an organic alkali metal compound is used as a polymerization initiator, the amount of the modifier relative to 1 mol of the metal atom in the organic alkali metal compound). Furthermore, the above-mentioned modifiers can be used alone or in combination of two or more.

[0112] The method for reacting the modifier with the active ends of the conjugated diene polymer chains is not particularly limited, but examples include mixing the polymer chains with active ends with the modifier in a solvent capable of dissolving them. The solvent used in this process can be any of the solvents exemplified above for the polymerization of the conjugated diene polymer. Furthermore, it is preferred that the polymer chains with active ends obtained in this manner be prepared as a polymerization solution for this polymerization, as this simplifies the method for adding the modifier. Alternatively, the modifier can be dissolved in the inert solvent used in the polymerization process and added to the polymerization system, preferably at a concentration of 1 to 50% by weight. The reaction temperature is not particularly limited, but is typically 0 to 120°C. The reaction time is not particularly limited, but is typically 1 minute to 1 hour.

[0113] The timing for adding the modifier to the solution containing polymer chains with active ends is not particularly limited, but it is desirable to add the modifier to the solution before the polymerization reaction is complete and the solution containing the polymer chains with active ends still contains monomers. More specifically, it is desirable to add the modifier to the solution before the solution containing the polymer chains with active ends contains 100 ppm or more, preferably 300-50,000 ppm, of monomers. Adding the modifier in this manner suppresses side reactions between the polymer chains with active ends and impurities in the polymerization system, thereby effectively controlling the reaction.

[0114] Preferably, a polymerization terminator such as an alcohol such as methanol or isopropyl alcohol or water is added to the active ends of the conjugated diene polymer chains obtained by polymerization, or to the active ends remaining after reaction with a coupling agent or a modifier as needed, to inactivate the unreacted active ends.

[0115] After deactivating the active ends of the conjugated diene polymer chains, an anti-aging agent, such as a phenolic stabilizer, a phosphorus stabilizer, or a sulfur stabilizer, a crumb agent, and an anti-scaling agent are added to the polymerization solution as desired. The polymerization solvent is then separated from the polymerization solution by direct drying or steam distillation, and the conjugated diene polymer is recovered. Furthermore, before separating the polymerization solvent from the polymerization solution, an extender oil may be mixed with the polymerization solution to recover the conjugated diene polymer as an oil-extended conjugated diene polymer.

[0116] When recovering conjugated diene polymers as oil-extended conjugated diene polymers, extender oils include, for example, paraffinic, aromatic, and cyclic petroleum softeners, plant-based softeners, vegetable oils, and fatty acids. When using petroleum softeners, the polycyclic aromatic content extracted using the IP346 method (test method of THE INSTITUTE PETROLEUM, UK) is preferably less than 3%. When using extender oil, the amount used is preferably 1-100 parts by weight, more preferably 3-60 parts by weight, and even more preferably 5-40 parts by weight, per 100 parts by weight of the conjugated diene polymer.

[0117] [Silica]

[0118] The rubber composition of the present invention contains silica in addition to the conjugated diene polymer described above.

[0119] Examples of silica include dry-process white carbon, wet-process white carbon, colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. Among these, wet-process white carbon containing hydrous silicic acid as its main component is preferred. Furthermore, carbon-silica dual-phase fillers, in which silica is supported on the surface of carbon black, can also be used. These silicas can be used individually or in combination of two or more. The nitrogen adsorption specific surface area of ​​the silica used (measured by the BET method according to ASTM D3037-81) is preferably 20-400 m² / g, more preferably 50-220 m² / g, and most preferably 80-200 m² / g. Furthermore, the pH of the silica is preferably 5-10.

[0120] As silica, various commercially available silicas can be used. Examples include: "Hi-Sil 210," "Hi-Sil 233," and "Hi-Sil 243LD" manufactured by PPG Industries; "Zeosil 1115MP," "Zeosil 1165MP," and "Zeosil 165GR" manufactured by Solvay; "ULTRASIL VN2," "ULTRASIL VN3," "ULTRASIL 7000GR," and "ULTRASIL 9100GR" manufactured by Evonik; and "NIPSIL VN3," "NIPSIL AQ," "NIPSIL ER," and "NIPSIL RS-150" manufactured by Tosoh Silicon Chemicals.

[0121] The amount of silica incorporated into the rubber composition of the present invention is preferably 10-200 parts by weight, more preferably 20-150 parts by weight, and even more preferably 30-100 parts by weight, based on 100 parts by weight of the conjugated diene polymer in the rubber composition. By incorporating silica within this range, processability is improved, while silica dispersibility and the resulting cross-linked rubber product's balance between low fuel consumption and durability are further enhanced.

[0122] The method for adding silica to the conjugated diene polymer is not particularly limited, and a method of adding and kneading the solid conjugated diene polymer (dry kneading method) or a method of adding to a solution containing the conjugated diene polymer, solidifying it, and drying it (wet kneading method) can be applied.

[0123] The rubber composition of the present invention may also contain fillers other than silica. Examples of fillers other than silica include calcium silicate, aluminum silicate, carbon black, calcium carbonate, talc, aluminum hydroxide, aluminum oxide, clay, and mica. Carbon black is preferred among these. These fillers may be used alone or in combination of two or more. The amount of fillers other than silica that can be added is not particularly limited, as long as it does not impair the effects of the present invention.

[0124] Examples of carbon black include furnace black, acetylene black, thermal black, channel black, and graphite. Examples of channel black include EPC, MPC, and CC. Examples of furnace black include SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF. Examples of thermal black include FT and MT. Each carbon black may be used alone or in combination of two or more.

[0125] In the rubber composition of the present invention, the ratio of silica content to the total filler content (the total content of silica and fillers other than silica) is not particularly limited, but is preferably 30-100% by weight, more preferably 50-100% by weight, more preferably 70-100% by weight, and particularly preferably 80-100% by weight. By maintaining the silica content within this range, the balance between low fuel consumption and durability of the resulting cross-linked rubber can be further improved.

[0126] [Sulfur-based silane coupling agent]

[0127] The rubber composition of the present invention contains a sulfide silane coupling agent in addition to the conjugated diene polymer and silica described above.

[0128] Specific examples of sulfur-based silane coupling agents include bis[3-(triethoxysilyl)propyl] disulfide, bis[3-(triethoxysilyl)propyl] trisulfide, bis[3-(triethoxysilyl)propyl] tetrasulfide, 3-octylthio-1-propyltriethoxysilane, γ-trimethoxysilylpropylbenzothiazolyl tetrasulfide, γ-trimethoxysilylpropyldimethylaminothiomethyltetrasulfide, 3-trimethoxysilylpropyl-N,N-dimethylaminothiomethyltetrasulfide, and 3-trimethoxysilylpropyl methacrylate monosulfide. Among these, bis[3-(triethoxysilyl)propyl]tetrasulfide, bis[3-(triethoxysilyl)propyl]disulfide, and bis[3-(triethoxysilyl)propyl]trisulfide are preferred, with bis[3-(triethoxysilyl)propyl]tetrasulfide being particularly preferred. These sulfide-based silane coupling agents can be used individually or in combination of two or more.

[0129] The amount of the sulfur-based silane coupling agent incorporated is not particularly limited, but is preferably 0.1 to 30 parts by weight, and more preferably 1 to 15 parts by weight, relative to 100 parts by weight of silica. By incorporating the sulfur-based silane coupling agent within this range, the affinity between the conjugated diene polymer and silica can be further enhanced, thereby further improving the dispersibility of silica, thereby further enhancing product stability and further improving the balance between low fuel consumption and durability of the resulting cross-linked rubber.

[0130] [Crosslinking agent]

[0131] The rubber composition of the present invention contains a crosslinking agent in addition to the conjugated diene polymer, silica, and sulfide silane coupling agent described above.

[0132] As the crosslinking agent, examples thereof include sulfur, sulfur-containing compounds such as sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, alkylphenol resins having hydroxymethyl groups, and the like. Among these, sulfur is preferably used. The blending amount of the crosslinking agent is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 4 parts by weight with respect to 100 parts by weight of the conjugated diene polymer in the rubber composition.

[0133] When sulfur or a sulfur-containing compound is used as the crosslinking agent, it is preferable to use a crosslinking accelerator and a crosslinking activator in combination. As the crosslinking accelerator, examples thereof include sulfenamide-based crosslinking accelerators, guanidine-based crosslinking accelerators, thiourea-based crosslinking accelerators, thiazole-based crosslinking accelerators, aminothiocarbonyl-based crosslinking accelerators, amine dithiocarboxylic acid-based crosslinking accelerators, xanthate-based crosslinking accelerators, and the like. Among these, those containing a sulfenamide-based crosslinking accelerator are preferable. These crosslinking accelerators can be used alone or in combination of two or more. The blending amount of the crosslinking accelerator is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 4 parts by weight with respect to 100 parts by weight of the conjugated diene polymer in the rubber composition.

[0134] Examples of the crosslinking activator include higher fatty acids such as stearic acid, zinc oxide, and the like. These crosslinking activators can be used alone or in combination of two or more. The blending amount of the crosslinking activator is preferably from 0.05 to 20 parts by weight, and particularly preferably from 0.5 to 15 parts by weight with respect to 100 parts by weight of the conjugated diene polymer in the rubber composition.

[0135] Furthermore, in addition to the above components, the rubber composition of the present invention may be blended with blending agents such as antioxidants, activators, processing oils, plasticizers, lubricants, tackifiers, etc. in amounts required according to conventional methods. As the processing oil, petroleum-based softeners, plant-based softeners, vegetable oils, and fatty acids can be used, and they can be used alone or in combination of two or more.

[0136] [Vulcanization characteristic index (tc10) of the rubber composition]

[0137] The rubber composition of the present invention is measured using a vibrating vulcanization tester in accordance with JIS K6300-2, and the value of tc10, which is the vulcanization characteristic index, satisfies the following formula (1). 0.8 minutes < tc10 < 5.0 minutes (1)

[0138] The rubber composition of the present invention controls the vulcanization characteristics in such a manner that "in addition to the conjugated diene polymer, silica, and crosslinking agent, it further contains a sulfur-based silane coupling agent and the value of tc10, which is an index of vulcanization characteristics, falls within the defined range". Thereby, it is possible to simultaneously achieve excellent product stability accompanied by excellent dispersibility of silica, as well as excellent low fuel consumption characteristics and excellent durability of the obtained rubber crosslinked product. In addition, the value of tc10 of the rubber composition can be specifically measured by the method described in the examples.

[0139] The value of tc10 of the rubber composition of the present invention only needs to satisfy formula (1) and is not particularly limited, but it is preferably 0.8 minutes < tc10 < 4.5 minutes, and more preferably 0.8 minutes < tc10 < 4.0 minutes. By the value of tc10 being within the above range, the balance between the dispersibility of silica and the low fuel consumption characteristics and durability of the obtained rubber crosslinked product can be further improved. And, from the viewpoint of further improving the dispersibility of the filler and thereby further improving product stability, it is preferably satisfied that 0.8 minutes < tc10 < 3.5 minutes, and more preferably 0.8 minutes < tc10 < 3.0 minutes. On the other hand, from the viewpoint of further improving the durability of the obtained rubber crosslinked product, it is preferably satisfied that 1.0 minutes < tc10 < 4.0 minutes, more preferably 1.5 minutes < tc10 < 3.8 minutes, and even more preferably 2.0 minutes < tc10 < 3.5 minutes. The value of tc10 of the rubber composition, for example, in a suitable manufacturing method of the rubber composition described later, can be adjusted by adjusting the standing period when the rubber composition before standing is allowed to stand to manufacture the rubber composition.

[0140] [Manufacturing method of rubber composition]

[0141] The rubber composition of the present invention can be suitably manufactured by a manufacturing method in which a conjugated diene polymer, silica, sulfur-based silane coupling agent, crosslinking agent, and various blending agents used as required are mixed and then allowed to stand at room temperature (20 - 30°C) for 1 - 21 days. By allowing it to stand at room temperature (20 - 30°C) for 1 - 21 days, the rubber composition becomes one that controls the vulcanization characteristics in such a manner that it contains the above-mentioned various components and the value of tc10, which is an index of vulcanization characteristics, falls within the specific range.

[0142] When mixing a conjugated diene polymer, silica, a sulfide silane coupling agent, a crosslinking agent, and optionally other additives, it is preferable to knead the ingredients excluding thermally unstable ingredients such as the crosslinking agent or crosslinking accelerator—specifically, the conjugated diene polymer, silica, and the sulfide silane coupling agent—before adding the thermally unstable ingredients such as the crosslinking agent or crosslinking accelerator to this kneaded mixture. The kneading temperature for kneading the ingredients excluding the thermally unstable ingredients is preferably 80-200°C, more preferably 110-180°C, and the kneading time is preferably 30 seconds to 30 minutes. Furthermore, the kneaded mixture and the thermally unstable ingredients such as the crosslinking agent or crosslinking accelerator are typically mixed after cooling to below 60°C.

[0143] Furthermore, when kneading the above-mentioned components, even when the kneading machine temperature is set to a predetermined temperature, the temperature of the kneaded product often rises due to frictional forces generated by kneading. Therefore, in the present invention, taking into account such temperature rises due to frictional forces generated by kneading, it is desirable to control the temperature during kneading within the aforementioned range by adjusting the kneading machine speed so that the temperature of the kneaded product remains constant.

[0144] By the above operation, a pre-resting rubber composition is obtained by mixing a conjugated diene polymer, silica, a sulfide silane coupling agent, a crosslinking agent, and various additives as needed. After obtaining the pre-resting rubber composition, resting at room temperature (20-30°C) is initiated. By continuing the resting at room temperature (20-30°C) for 1-21 days, the rubber composition of the present invention can be preferably produced.

[0145] Furthermore, after kneading the components excluding heat-labile components such as crosslinking agents and crosslinking accelerators, when heat-labile components such as crosslinking agents and crosslinking accelerators are added to the kneaded mixture, if the mixing is performed at a temperature higher than room temperature, the rubber composition is allowed to stand at room temperature (20-30°C) before being allowed to stand after cooling to room temperature within a short period of about one hour after mixing. The standing period at room temperature (20-30°C) is not particularly limited and can be 1-21 days. However, from the perspective of further improving filler dispersibility and thus product stability, 1-18 days is preferred, 1-14 days is more preferred, 1-10 days is more preferred, and 1-7 days is particularly preferred. Furthermore, from the perspective of further improving the durability of the resulting cross-linked rubber product, 2-20 days is preferred, 3-19 days is more preferred, and 4-18 days is even more preferred.

[0146] Cross-linked rubber

[0147] The cross-linked rubber product of the present invention can be obtained by cross-linking the rubber composition of the present invention. The rubber composition of the present invention can be preferably produced by the method for producing the cross-linked rubber product of the present invention described below.

[0148] The method for producing a cross-linked rubber of the present invention comprises the steps of mixing a conjugated diene polymer, silica, a sulfide silane coupling agent, and a cross-linking agent, and then allowing the mixture to stand at room temperature for 1 to 21 days to obtain a rubber composition, and then cross-linking the rubber composition.

[0149] The cross-linked rubber product of the present invention can be produced by forming the rubber composition of the present invention into a desired shape using a molding machine, such as an extruder, injection molding machine, compressor, or roller, and then heating the rubber composition to initiate a cross-linking reaction, thereby fixing the shape in the cross-linked rubber product. In this case, cross-linking can be performed after forming or simultaneously with forming. The forming temperature is typically 10-200°C, preferably 25-120°C. The cross-linking temperature is typically 100-200°C, preferably 130-190°C. The cross-linking time is typically 1 minute to 24 hours, preferably 2 minutes to 12 hours, and particularly preferably 3 minutes to 6 hours.

[0150] Furthermore, depending on the shape and size of the cross-linked rubber, the surface may be cross-linked but the interior may not be fully cross-linked. Therefore, further heating may be performed for secondary cross-linking.

[0151] As the heating method, any method generally used for cross-linking rubber, such as pressurized heating, steam heating, oven heating, or hot air heating, may be appropriately selected.

[0152] <Method for producing cross-linked rubber>

[0153] The present invention also relates to a method for producing a cross-linked rubber.

[0154] The method for producing a cross-linked rubber of the present invention comprises the steps of mixing a conjugated diene polymer, silica, a sulfide silane coupling agent, and a cross-linking agent, and then allowing the mixture to stand at room temperature for 1 to 21 days to obtain a rubber composition, and then cross-linking the rubber composition.

[0155] The method for obtaining a rubber composition by mixing a conjugated diene polymer, silica, a sulfide silane coupling agent, and a crosslinking agent and then allowing the mixture to stand at room temperature for 1 to 21 days can be used in the manner described above. Specifically, the following method is preferred: kneading the ingredients excluding heat-labile ingredients such as a crosslinking agent or a crosslinking accelerator, then adding the heat-labile ingredients such as a crosslinking agent or a crosslinking accelerator to the kneaded mixture, and optionally cooling the mixture for a short period of time to obtain a pre-standing rubber composition, which is then allowed to stand at room temperature for 1 to 21 days.

[0156] Furthermore, the rubber composition can be cross-linked using the methods described above. Specifically, the following method is preferred: the rubber composition is formed into a desired shape using a molding machine, and then heated to initiate a cross-linking reaction, thereby fixing the shape in the form of a cross-linked rubber.

[0157] The cross-linked rubber of the present invention, obtained in this manner, is obtained by using the rubber composition of the present invention described above and therefore exhibits excellent fuel efficiency and durability. Therefore, leveraging its excellent properties, the cross-linked rubber of the present invention can be used in various applications, such as materials for various tire components, including the cap tread, base tread, carcass, sidewall, and bead portion; materials for hoses, belts, base pads, rubber cushions, and various other industrial products; resin impact resistance improvers; resin film cushioning agents; shoe soles; rubber shoes; golf balls; and toys. In particular, the cross-linked rubber of the present invention, due to its excellent fuel efficiency and durability, is suitable for use as a tire material.

[0158] 『Example』

[0159] The present invention is further described below based on detailed examples, but the present invention is not limited to these examples. Furthermore, "parts" below are by weight unless otherwise noted. Furthermore, testing and evaluation were conducted as follows.

[0160] [Weight average molecular weight and coupling ratio of conjugated diene polymer]

[0161] The weight-average molecular weight of the conjugated diene polymer is determined using a table of molecular weights calculated based on polystyrene conversion obtained by gel permeation chromatography (GPC). Specific measurement conditions for gel permeation chromatography are shown below. Measuring instrument: High-speed liquid chromatograph (manufactured by Tosoh Corporation, trade name "HLC-8320") Column: Two polystyrene columns manufactured by Tosoh Corporation (trade name "GMH-HR-H") were connected in series. Detector: Differential Refractive Index (RI) Solvent: Tetrahydrofuran Column temperature: 40℃

[0162] Furthermore, the coupling rate is determined by identifying the peak with the smallest peak molecular weight (corresponding to the peak molecular weight of the polymer chain before the coupling reaction) in the elution curve obtained by gel permeation chromatography under the above-mentioned conditions, calculating the elution area of ​​the portion having a peak molecular weight (corresponding to the peak molecular weight of the coupled polymer) that is 1.5 times or more the peak molecular weight of the peak, dividing the calculated peak area by the total elution area, and converting the result into a percentage.

[0163] [Aromatic vinyl monomer unit content and vinyl bond content of conjugated diene polymer]

[0164] The aromatic vinyl monomer unit content and vinyl bond content of the conjugated diene polymer were measured by 1H-NMR.

[0165] [Muni viscosity of oil-extended conjugated diene polymer (ML1+4, 100℃)]

[0166] The Muni viscosity (ML1+4, 100° C.) of the oil-extended conjugated diene polymer was measured using a Muni viscometer (manufactured by Shimadzu Corporation) in accordance with JIS K6300-1.

[0167] 〔tc10〕

[0168] In accordance with JIS K6300-2, a vibration-type vulcanization tester (manufactured by ALPHA TECHNOLOGIES) was used at a temperature of 160°C, a test time of 60 minutes, a vibration rate of 100 times per minute, and an amplitude angle of ±1° to measure tc10 (unit: minutes), an indicator of vulcanization characteristics.

[0169] 〔(MH-ML) Index〕

[0170] In accordance with ISO 6502, MH-ML, an indicator of vulcanization properties, was measured using a vibratory vulcanization tester (manufactured by ALPHA TECHNOLOGIES) at a temperature of 160°C, a test time of 60 minutes, a vibration rate of 100 vibrations per minute, and an amplitude angle of ±1°. The MH-ML values ​​of the Examples and Comparative Examples were calculated as an index, with the MH-ML of Comparative Example 2 set to 100. A higher (MH-ML) index indicates a higher crosslink density, resulting in a more durable rubber crosslinked product.

[0171] [60°C tanδ index of cross-linked rubber]

[0172] A 2 mm thick cross-linked rubber sheet was punched into a 4 mm wide and 40 mm long strip to obtain a test piece. The resulting test piece was measured using a viscoelasticity measuring instrument (manufactured by Ueshima Seisakusho Co., Ltd.) at a frequency of 10 Hz, an initial elongation of 10%, a strain amplitude of 2%, and a temperature of 60°C. The loss tangent (tanδ(60°C)) values ​​for each Example and Comparative Example were indexed, with the loss tangent (tanδ(60°C)) in Comparative Example 2 set to 100. This index was used to determine the fuel efficiency value. A higher fuel efficiency value indicates that the obtained cross-linked rubber product exhibits superior fuel efficiency.

[0173] Payne effect index

[0174] An uncrosslinked rubber composition was processed to produce a 3 cm square test piece weighing approximately 6 g. After preheating the test piece at 100°C for 4 minutes, the storage elastic modulus (G') was measured at 0.7% and 42% dynamic strain using a PREMIER RPA (manufactured by ALPHA TECHNOLOGIES) at 40°C and 10 Hz. The absolute value of the difference (ΔG') between the storage elastic modulus (G') at 0.7% dynamic strain and the storage elastic modulus (G') at 42% dynamic strain was calculated. The absolute value of the difference (ΔG') in the storage elastic modulus (G') of Comparative Example 2 was divided by the absolute value of the difference (ΔG') in the storage elastic modulus (G') of each Example and Comparative Example, and the resulting value was multiplied by 100 to determine the Payne effect index for each Example and Comparative Example. Furthermore, the absolute value of the difference in storage elasticity G' (ΔG') is inversely proportional to the value of the Payne Effect Index. When the absolute value of the difference in storage elasticity G' (ΔG') is equal to that in Comparative Example 2, the Payne Effect Index is 100. The smaller the absolute value of the difference in storage elasticity G' (ΔG'), the larger the Payne Effect Index becomes, and the larger the absolute value of the difference in storage elasticity G' (ΔG'), the smaller the Payne Effect Index becomes. A larger Payne Effect Index value indicates a better dispersion of the filler contained in the uncrosslinked rubber composition, and thus, superior product stability.

[0175] [Preparation of polymer block (A) having active terminals]

[0176] In an 800 mL container purged with nitrogen, 140.8 g of cyclohexane and 3.0 mmol of tetramethylethylenediamine were added, followed by 30.0 mmol of n-butyllithium. Subsequently, 113.6 g of isoprene and 9.2 g of styrene were slowly added, and the mixture was allowed to react in the container at 50°C for 120 minutes to obtain a polymerization solution containing a polymer block (A) having active terminals. The resulting polymer block (A) had a weight-average molecular weight (Mw) of 6,500, a molecular weight distribution (Mw / Mn) of 1.10, a styrene monomer unit content of 7.5%, an isoprene monomer unit content of 92.5%, and a vinyl bond content of 7.0%.

[0177] (Production Example 1 [Oil-Extended Conjugated Diene Polymer P1])

[0178] In a 20 L autoclave equipped with a stirrer, 7,956 g of industrial hexane, 1,014 g of cyclohexane, 4.25 mmol of tetramethylethylenediamine, 408 g of 1,3-butadiene, and 680 g of styrene were placed under a nitrogen atmosphere. To detoxify impurities that may contribute to the inactivation of the polymerization, a small amount of n-butyllithium was added to the autoclave as a scavenger. The polymer block (A) obtained above, which contained 7.08 mmol of lithium atoms, was then added and the polymerization reaction was allowed to proceed at 50°C. After the polymerization reaction was continued for 20 minutes, 612 g of 1,3-butadiene was continuously added over 80 minutes. After confirming that the polymerization conversion rate was within the range of 95% to 100%, the polyorganosiloxane represented by the following formula (10) was added to achieve an epoxy group content of 3.19 mmol, and the reaction was allowed to proceed for 20 minutes. Then, 2 equivalents of methanol were added as a polymerization terminator relative to the total amount of lithium in the autoclave, yielding a solution containing a conjugated diene polymer. To this solution, 0.20 parts of 2,4-bis(octylthiomethyl)-6-methylphenol were added as an anti-aging agent relative to 100 parts of the conjugated diene polymer, yielding a polymerization solution containing the conjugated diene polymer P1. Measurements of the obtained conjugated diene polymer P1 using the aforementioned method revealed a weight-average molecular weight (Mw) of 724,000, a coupling ratio of 50.7%, a styrene monomer unit content of 40.7% by weight, and a vinyl bond content within the butadiene units of 29.1 mol%.

[0179] Subsequently, 10 parts of process oil (manufactured by ENEOS, trade name: Aromax T-DAE) was added as an extender to the polymerization solution containing the conjugated diene polymer P1, relative to 100 parts of the conjugated diene polymer. The mixture was stirred, and the majority of the volatile components of the resulting polymerization solution were evaporated at room temperature over 24 hours. The solution was then dried under reduced pressure at 55°C for 12 hours, thereby obtaining the oil-extended conjugated diene polymer P1. The obtained oil-extended conjugated diene polymer P1 was measured according to the above method, and the Muni viscosity of the oil-extended conjugated diene polymer P1 was 117 (ML1+4, 100°C).

[0180] "Chemistry 3"

[0181] (Production Example 2 [Oil-Extended Conjugated Diene Polymer P2])

[0182] In a 20 L autoclave equipped with a stirrer, 7,956 g of industrial hexane, 1,014 g of cyclohexane, 4.80 mmol of tetramethylethylenediamine, 408 g of 1,3-butadiene, and 680 g of styrene were placed under a nitrogen atmosphere. To pre-detoxify impurities that may contribute to the inactivation of the polymerization, a small amount of n-butyllithium was added to the autoclave as a scavenger. Then, 6.67 mmol of n-butyllithium was added, and the polymerization reaction was initiated at 50°C. The polymerization reaction was continued for 20 minutes, and then 612 g of 1,3-butadiene was continuously added over 80 minutes. After confirming that the polymerization conversion rate was within the range of 95% to 100%, the polyorganosiloxane represented by the above formula (10) was added to achieve an epoxy group content of 3.20 mmol, and the reaction was allowed to proceed for 20 minutes. Then, 2 equivalents of methanol were added as a polymerization terminator relative to the total amount of lithium in the autoclave, yielding a solution containing conjugated diene polymer P2. To this solution, 0.20 parts of 2,4-bis(octylthiomethyl)-6-methylphenol were added as an anti-aging agent relative to 100 parts of the conjugated diene polymer, yielding a polymerization solution containing conjugated diene polymer P2. Measurements of the obtained conjugated diene polymer P2 using the aforementioned method revealed a weight-average molecular weight (Mw) of 728,000, a coupling ratio of 53.0%, a styrene monomer unit content of 41.3% by weight, and a vinyl bond content in the butadiene units of 28.5 mol%.

[0183] Subsequently, 10 parts of T-DAE (as an extender oil) was added to the polymerization solution containing the conjugated diene polymer P2, relative to 100 parts of the conjugated diene polymer. The mixture was stirred, and the majority of the volatile components of the resulting polymerization solution were evaporated at room temperature over 24 hours. The solution was then dried under reduced pressure at 55°C for 12 hours, thereby obtaining the oil-extended conjugated diene polymer P2. The obtained oil-extended conjugated diene polymer P2 was measured according to the aforementioned method, and the Muni viscosity of the oil-extended conjugated diene polymer P2 was 116 (ML1+4, 100°C).

[0184] (Example 1)

[0185] [Manufacturing and evaluation of rubber compositions and cross-linked rubber products]

[0186] In a 600 mL Brabender type kneader, 88 parts by weight (80 parts by weight as the rubber component) of the oil-extended conjugated diene polymer P1 and 20 parts by weight of polybutadiene rubber (Nipol BR1220, manufactured by Japan Zeon Co., Ltd.) were kneaded for 30 seconds. Subsequently, 80 parts by weight of silica (ULTRASIL 7000GR, manufactured by Evonik) and processing oil (Aromax, manufactured by ENEOS) were added. The conjugated diene polymer composition was further kneaded for 4.5 minutes, and the resultant mixture was discharged from a mixing / extrusion tester (LABO PLASTOMILL). The temperature of the LABO PLASTOMILL reading at the time of discharge was 160°C. After cooling the kneaded material to room temperature, it was kneaded again in a Bournfield mixer at a starting temperature of 110°C for 3 minutes. The kneaded material was then discharged from the Labo Plastic Mill. Subsequently, 1.7 parts by weight of sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd., trade name: Kinkain Micronized Sulfur 200 mesh), 1.8 parts by weight of N-cyclohexyl-2-benzothiazolesulfenamide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name: Nocceler CZ-G), and 1.7 parts by weight of 1,3-diphenylguanidine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name: Nocceler D) were added to the kneaded material. The mixture was kneaded using an open roll set to 50°C, formed into a sheet, and cooled to room temperature to obtain a rubber composition before standing. This rubber composition was allowed to stand at room temperature for one day to obtain a rubber composition. The TC10, (MH-ML) index, and Payne effect index were measured and evaluated. The resulting rubber composition was then cross-linked under pressure at 160°C for 10 minutes to produce a cross-linked rubber test piece. This test piece was used to evaluate the 60°C tan delta index. The results are shown in Table 1.

[0187] (Example 2)

[0188] A cross-linked rubber was obtained by following the same procedure as in Example 1, except that the rubber composition was allowed to stand at room temperature for 7 days instead of 1 day. The evaluation results are shown in Table 1.

[0189] (Example 3)

[0190] A cross-linked rubber was obtained by following the same procedure as in Example 1, except that the rubber composition was allowed to stand at room temperature for 14 days instead of 1 day. The evaluation results are shown in Table 1.

[0191] (Comparative Example 1)

[0192] A cross-linked rubber was obtained by following the same procedures as in Example 1, except that the rubber composition was left at room temperature for 0 days instead of 1 day (i.e., the next operation was performed immediately without leaving the rubber composition at room temperature). The evaluation results are shown in Table 1.

[0193] (Comparative Example 2)

[0194] A cross-linked rubber was obtained by the same procedure except that the oil-extended conjugated diene polymer P2 was used instead of the oil-extended conjugated diene polymer P1 in Example 1. The evaluation results are shown in Table 1.

[0195] Table 1 [surface] [1] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Composition of rubber components Oil-extended conjugated diene polymer (P1) [share] 88 88 88 88 Oil-extended conjugated diene polymer (P2) [share] 88 polybutadiene rubber [share] 20 20 20 20 20 Sulfur-based silane coupling agent (Si69) [share] 6.4 6.4 6.4 6.4 6.4 Manufacturing method During standing at room temperature [sky] 1 7 14 0 1 evaluate tc10 [minute] 0.84 2.90 3.10 0.65 0.78 (MH-ML) index 103 147 146 84 100 Payne Effect Index 109 117 105 108 100 60℃ tanδ index 106 106 109 106 100

[0196] As shown in Table 1, the rubber composition containing a conjugated diene polymer, silica, a sulfide silane coupling agent, and a crosslinking agent, and having a tc10 value satisfying the above formula (1), has excellent silica dispersion, thereby having excellent product stability, and can produce a rubber cross-linked product with low fuel consumption characteristics and excellent durability (Examples 1 to 3).

[0197] On the other hand, when the value of tc10 is too small, the durability of the obtained rubber cross-linked product may be poor, and the silica dispersibility and fuel efficiency may also be poor (Comparative Examples 1 and 2).

[0198] none

Claims

1. A rubber composition comprising a conjugated diene polymer, silica, a sulfide silane coupling agent, and a crosslinking agent, wherein the value of tc10, a vulcanization characteristic index measured using a vibration vulcanization tester according to JIS K6300-2, satisfies the following formula (1): 0.8 min < tc10 < 5.0 min (1); wherein the conjugated diene polymer comprises 25 to 99.9% by weight of 1,3-butadiene units, 0.1 to 15% by weight of isoprene monomer units, and 0 to 60% by weight of aromatic ethylene monomer units.

2. The rubber composition as claimed in claim 1, wherein the aforementioned conjugated diene polymer comprises 40 to 96.9% by weight of 1,3-butadiene units, 0.1 to 10% by weight of isoprene monomer units, and 3 to 50% by weight of aromatic ethylene monomer units.

3. The rubber composition as claimed in claim 1 or 2, wherein the aforementioned conjugated diene polymer comprises an isoprene-containing block containing 80 to 100% by weight of isoprene monomer units.

4. The rubber composition as claimed in claim 1 or 2, wherein the aforementioned conjugated diene polymer contains silicon-containing functional groups formed from siloxane compounds.

5. A rubber crosslinker formed by crosslinking a rubber composition as described in any one of claims 1 to 4.

6. A tire comprising a rubber crosslinker as described in claim 5.

7. A method for manufacturing a rubber crosslinked compound, comprising a step of mixing a conjugated diene polymer, silica, a sulfide silane coupling agent and a crosslinking agent and allowing the mixture to stand at room temperature for 1 to 21 days to obtain a rubber composition as described in claim 1, and a step of crosslinking the aforementioned rubber composition.

8. The method for manufacturing the rubber crosslinked compound as claimed in claim 7, wherein the aforementioned conjugated diene polymer comprises 40 to 96.9% by weight of 1,3-butadiene units, 0.1 to 10% by weight of isoprene monomer units, and 3 to 50% by weight of aromatic ethylene monomer units.

9. A method for manufacturing a rubber crosslink as claimed in claim 7 or 8, wherein the aforementioned conjugated diene polymer comprises an isoprene-containing block containing 80 to 100% by weight of isoprene monomer units.

10. A method for manufacturing a rubber crosslink as claimed in claim 7 or 8, wherein the aforementioned conjugated diene polymer contains a silicon-containing functional group formed from a siloxane compound.