阅读说明：本技术 橡胶组合物和轮胎 (Rubber composition and tire ) 是由 田中隆嗣 于 2019-08-09 设计创作，主要内容包括：提供一种在高度保持低损耗性的同时具有优异的耐久性(耐龟裂性)和耐磨耗性的橡胶组合物和轮胎。该橡胶组合物包括改性共轭二烯系聚合物和天然橡胶,其中所述改性共轭二烯系聚合物每一个分子具有至少2个改性基团,所述改性基团各自与所述改性基团中的另一个形成分子间的非共价键,并且每一个非共价键的能量为10-200kJ/mol。该轮胎使用所述橡胶组合物。(Provided are a rubber composition and a tire having excellent durability (crack resistance) and wear resistance while highly maintaining low loss properties. The rubber composition comprises a modified conjugated diene polymer and a natural rubber, wherein the modified conjugated diene polymer has at least 2 modifying groups per molecule, each of the modifying groups forms an intermolecular non-covalent bond with another of the modifying groups, and the energy of each non-covalent bond is 10 to 200 kJ/mol. The tire uses the rubber composition.)

1. A rubber composition, comprising:

a modified conjugated diene polymer; and

the natural rubber is prepared from natural rubber,

wherein the modified conjugated diene polymer has 2 or more modifying groups per molecule, the modifying groups form non-covalent bonds between molecules, and the energy per non-covalent bond is 10kJ/mol to 200 kJ/mol.

2. The rubber composition according to claim 1, wherein a proportion of the mass of the modified conjugated diene polymer to the total mass of the modified conjugated diene polymer and the natural rubber is 20 to 90 mass%.

3. The rubber composition according to claim 1 or 2, wherein the modifying group is 1 or more selected from the group consisting of-COOM and-OM, wherein M is an alkali metal atom.

4. The rubber composition according to any one of claims 1 to 3, wherein the modifying group is 1 or more selected from the group consisting of-COOLi and-OLi.

5. The rubber composition according to any one of claims 1 to 4, wherein the modified conjugated diene-based polymer is 1 or more selected from the group consisting of a modified styrene butadiene copolymer and a modified polybutadiene.

6. The rubber composition according to any one of claims 1 to 5, wherein the modified conjugated diene-based polymer has a weight average molecular weight of 100,000 or more.

7. The rubber composition of any one of claims 1-6, further comprising a filler.

8. A tire comprising the rubber composition according to any one of claims 1 to 7.

Technical Field

The present disclosure relates to a rubber composition and a tire.

Background

In recent years, the demand for improving fuel efficiency of automobiles has become more severe. In order to meet such a demand, it is necessary to reduce rolling resistance with respect to tire performance. The most commonly employed method for reducing the rolling resistance of a tire is to use a material having lower heat build-up (better low loss property) as a rubber composition.

Examples of such a method disclosed include a method of using carbon black as a filler and modifying the polymerization active end by a tin compound (see, for example, JP S60-255838a (PTL 1)), and a method of using carbon black and introducing an amino group into the polymerization active end (see, for example, JP S62-207342A (PTL 2)).

Reference list

Patent document

PTL 1：JP S60-255838 A

PTL 2：JP S62-207342 A

Disclosure of Invention

Problems to be solved by the invention

However, in the polymer material, the lower the hysteresis loss, the more energy is generally used for fracture, and the strength (durability) is reduced.

There is also a demand for improvement in wear resistance of rubber products such as tires using the rubber composition.

Therefore, it is helpful to provide a rubber composition having excellent durability (crack resistance) and wear resistance while maintaining a low loss factor at a high level. It is also possible to contribute to providing a tire having excellent durability (crack resistance) and wear resistance while maintaining a low loss factor at a high level.

Means for solving the problems

The rubber composition according to the present disclosure is a rubber composition including a modified conjugated diene-based polymer; and a natural rubber, wherein the modified conjugated diene polymer has 2 or more modifying groups per molecule, the modifying groups form non-covalent bonds between molecules, and energy per the non-covalent bond is 10kJ/mol to 200 kJ/mol.

The rubber composition according to the present disclosure has excellent durability (crack resistance) and wear resistance while maintaining a low loss factor at a high level.

The tire according to the present disclosure is a tire including the above rubber composition.

The tire according to the present disclosure has excellent durability (crack resistance) and wear resistance while maintaining a low loss factor at a high level.

ADVANTAGEOUS EFFECTS OF INVENTION

Therefore, a rubber composition having excellent durability (crack resistance) and wear resistance while maintaining a low loss factor at a high level can be provided. It is also possible to provide a tire having excellent durability (crack resistance) and wear resistance while maintaining a low loss factor at a high level.

Detailed Description

Embodiments of the present disclosure will be described below. The following description is for exemplary purposes only and is not intended to limit the scope of the present disclosure in any way.

In the present disclosure, 2 or more embodiments may be freely combined.

Herein, the term "conjugated diene unit" means a unit derived from a conjugated diene compound in the modified conjugated diene-based polymer. Herein, the term "conjugated diene compound" means a conjugated diene-based compound.

In the present disclosure, the dissociation energy of a pair of non-covalent bonds from the modifying group in the modified conjugated diene polymer is calculated using Gaussian09 as a quantum chemical calculation program with M06/6-31G (d, p) as a basis function. The bond energy is calculated as follows: first, monomer units constituting non-covalent bonds are extracted, and then a coordination state model for calculating the energy of the coordination state is constructed. Next, the coordination state is sufficiently dissolved, and the energy of the dissociation state is calculated. The bond energy of each molecule is determined by the difference between the energy of the coordination state and the energy of the dissociation state, and then divided by the number of coordination bonds to obtain the bond energy of each bond.

In the present disclosure, the weight average molecular weight (Mw) is measured as follows: a calibration curve was prepared from monodisperse polystyrene by gel permeation chromatography (GPC: HLC-8020 manufactured by Tosoh Corporation, column: GMH-XL manufactured by Tosoh Corporation (two in series), detector: differential Refractometer (RI)), and the polystyrene-converted weight average molecular weight (Mw) of each modified conjugated diene polymer was determined. An aliquot of polymer cement (polymer) was removed from the polymerization flask and the polymerization was stopped using degassed isopropanol. Then, the Mw of the solution diluted with THF was measured to obtain a polystyrene-equivalent weight average molecular weight of the modified conjugated diene copolymer.

(rubber composition)

The rubber composition according to the present disclosure includes a modified conjugated diene-based polymer and a natural rubber, wherein the modified conjugated diene-based polymer has 2 or more modifying groups per molecule, the modifying groups form non-covalent bonds between molecules, and energy per the non-covalent bond is 10kJ/mol to 200 kJ/mol.

The rubber composition according to the present disclosure has excellent durability (crack resistance) and wear resistance while maintaining a low loss factor at a high level.

The modified conjugated diene-based polymer and the natural rubber, which are essential components of the rubber composition according to the present disclosure, and optional components of the rubber composition will be described below.

< modified conjugated diene Polymer >

The rubber composition according to the present disclosure contains a modified conjugated diene-based polymer as a rubber component. The modified conjugated diene polymer is a modified conjugated diene polymer having 2 or more modifying groups per molecule, and wherein non-covalent bonds are formed between the modifying groups and the energy per non-covalent bond is 10kJ/mol to 200 kJ/mol.

The modified conjugated diene polymer in the rubber composition according to the present disclosure has excellent low loss factor and durability. Without wishing to be bound by theory, the reason for this is presumed to be as follows: since the non-covalent bond-forming modifying group between molecules has a weak bond energy within the aforementioned specific range, in the crosslinked product of the rubber composition, the non-covalent bond is maintained to achieve an excellent low loss factor at low strain, while the non-covalent bond is broken and loss occurs to achieve an excellent durability at high strain.

In the modified conjugated diene polymer, the energy per non-covalent bond is preferably 50kJ/mol to 200kJ/mol from the viewpoint of excellent low loss factor and durability.

In one embodiment, the modified conjugated diene polymer has an energy per non-covalent bond of 10kJ/mol or more, 20kJ/mol or more, 30kJ/mol or more, 40kJ/mol or more, 50kJ/mol or more, 60kJ/mol or more, 70kJ/mol or more, 80kJ/mol or more, 90kJ/mol or more, 100kJ/mol or more, 110kJ/mol or more, 120kJ/mol or more, 130kJ/mol or more, 140kJ/mol or more, 150kJ/mol or more, 160kJ/mol or more, 170kJ/mol or more, 180kJ/mol or more, 190kJ/mol or more, or 195kJ/mol or more. In another embodiment, the energy per non-covalent bond in the modified conjugated diene polymer is 200kJ/mol or less, 195kJ/mol or less, 190kJ/mol or less, 180kJ/mol or less, 170kJ/mol or less, 160kJ/mol or less, 150kJ/mol or less, 140kJ/mol or less, 130kJ/mol or less, 120kJ/mol or less, 110kJ/mol or less, 100kJ/mol or less, 90kJ/mol or less, 80kJ/mol or less, 70kJ/mol or less, 60kJ/mol or less, 50kJ/mol or less, 40kJ/mol or less, 30kJ/mol or less, or 20kJ/mol or less.

The base polymer of the modified conjugated diene polymer, i.e., the conjugated diene polymer before modification, is a polymer containing at least a conjugated diene unit. Examples of the base polymer include a polymer composed of only conjugated diene units, and a copolymer containing at least conjugated diene units and aromatic vinyl units.

Examples of the conjugated diene compound forming the conjugated diene unit include butadiene (1, 3-butadiene), isoprene, 1, 3-pentadiene and 2, 3-dimethylbutadiene. The conjugated diene compound may be substituted or unsubstituted. In one embodiment, the conjugated diene compound has 4 to 8 carbon atoms. As the conjugated diene compound, butadiene and isoprene are preferable from the viewpoint of availability.

In one embodiment, the conjugated diene compound is 1 or more selected from the group consisting of 1, 3-butadiene and isoprene. In another embodiment, the conjugated diene compound is 1, 3-butadiene.

The content of the conjugated diene unit in the modified conjugated diene polymer is not limited, and is, for example, 20 mol% or more, 30 mol% or more, 40 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, or 95 mol% or more, and 100 mol% or less, 95 mol% or less, 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, 50 mol% or less, 40 mol% or less, 30 mol% or less, or 20 mol% or less. In one embodiment, the content of the conjugated diene unit in the modified conjugated diene-based polymer is 50 mol% to 100 mol%.

Examples of the aromatic vinyl compound forming the aromatic vinyl unit include styrene, alkylstyrene and halogenated alkylstyrene. As the aromatic vinyl compound, styrene is preferable from the viewpoint of availability.

Examples of the alkylstyrene include 4-methylstyrene, 3-methylstyrene and 2, 4-dimethylstyrene.

The number of carbon atoms of the alkyl group of the haloalkylstyrene is, for example, 1 to 5. Examples of halogen of the haloalkylstyrene include fluorine, chlorine, bromine and iodine. Examples of the haloalkylstyrenes include 4-chloromethylstyrene and 3-chloromethylstyrene.

In one embodiment, the aromatic vinyl compound is selected from 1 or more of the group consisting of styrene, alkylstyrene, and halogenated alkylstyrene.

In the case where the modified conjugated diene polymer contains an aromatic vinyl unit in addition to the conjugated diene unit, the content of the aromatic vinyl unit in the modified conjugated diene polymer is not limited, and is, for example, 0.1 mol% or more, 1 mol% or more, 5 mol% or more, 10 mol% or more, 20 mol% or more, 30 mol% or more, or 40 mol% or more, and 40 mol% or less, 30 mol% or less, 20 mol% or less, 10 mol% or less, 5 mol% or less, 1 mol% or less, or 0.1 mol% or less. In one embodiment, the content of the aromatic vinyl unit in the modified conjugated diene polymer is 0 mol% to 45 mol%.

1 kind of conjugated diene unit may be used alone, or 2 or more kinds of conjugated diene units may be used in combination. 1 kind of aromatic vinyl unit may be used alone, or 2 or more kinds of aromatic vinyl units may be used in combination.

Examples of the base polymer of the modified conjugated diene-based polymer include styrene butadiene copolymer, polybutadiene, and synthetic isoprene rubber.

The modifying group of the modified conjugated diene-based polymer is not limited as long as the modifying group can form a non-covalent bond and the energy per non-covalent bond is 10kJ/mol to 200 kJ/mol. Examples include-COOM and-OM (where M is an alkali metal atom).

Examples of the alkali metal atom (M) include Li, Na, K, Rb and Cs.

In the rubber composition according to the present disclosure, the modifying group is preferably 1 or more selected from the group consisting of-COOM and-OM (wherein M is an alkali metal atom). Therefore, a coordinate bond having an appropriate bond energy can be introduced.

In the rubber composition according to the present disclosure, the modifying group is preferably 1 or more selected from the group consisting of-COOLi and-OLi. Therefore, a coordinate bond having an appropriate bond energy can be introduced more easily.

The modified conjugated diene polymer has 2 or more of such modifying groups per molecule. In the case where the number of the modifying groups per molecule is less than 2, low loss factor, durability (crack resistance), and wear resistance are insufficient.

The number of modifying groups per molecule of the modified conjugated diene polymer is 2 or more, preferably 3 or more, and more preferably 5 or more. From the viewpoint of operability, the number of modifying groups per molecule is preferably 30 or less, more preferably 15 or less, and further preferably 10 or less.

In one embodiment, the number of modifying groups per molecule in the modified conjugated diene polymer is 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 9.5 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 20 or more, 25 or more, or 30 or more. In another embodiment, the number of the modifying group per molecule in the modified conjugated diene polymer is 30 or less, 25 or less, 20 or less, 19 or less, 18 or less, 17 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9.5 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, or 3 or less.

The molecular weight of the modified conjugated diene polymer is not limited and can be appropriately adjusted. For example, the modified conjugated diene polymer has a weight average molecular weight (Mw) of 100,000 or more or 150,000 or more and 1,000,000 or less, 500,000 or less, or 200,000 or less.

In the rubber composition according to the present disclosure, the weight average molecular weight of the modified conjugated diene-based polymer is preferably 100,000 or more. Therefore, both crack resistance and wear resistance can be achieved at a high level. The modified conjugated diene polymer preferably has an Mw of 150,000 to 250,000 from the viewpoint of crack resistance and abrasion resistance.

In the rubber composition according to the present disclosure, the modified conjugated diene polymer is preferably 1 or more selected from the group consisting of a modified styrene butadiene copolymer and a modified polybutadiene. The rubber composition has better crack resistance and abrasion resistance while keeping low loss factor at a high level.

1 kind of modified conjugated diene polymer may be used alone, or 2 or more kinds of modified conjugated diene polymers may be used in combination.

The proportion of the modified conjugated diene polymer in the rubber component can be appropriately adjusted. For example, the ratio of the mass of the modified conjugated diene polymer to the total mass of the modified conjugated diene polymer and the natural rubber is 10 mass% or more, 20 mass% or more, 30 mass% or more, 40 mass% or more, 50 mass% or more, or 60 mass% or more, and 90 mass% or less, 80 mass% or less, 70 mass% or less, 60 mass% or less, 50 mass% or less, or 40 mass% or less.

In the rubber composition according to the present disclosure, the ratio of the mass of the modified conjugated diene polymer to the total mass of the modified conjugated diene polymer and the natural rubber is preferably 20 to 90 mass%. This can further improve crack resistance while maintaining low loss properties at a high level.

< Process for producing modified conjugated diene Polymer >

The method for producing the modified conjugated diene polymer is not limited. For example, a manufacturing method including the following (i), (ii), and (iii) may be suitably used:

(i) anionic polymerization of a conjugated diene compound alone or a conjugated diene compound and an aromatic vinyl compound in the presence of an alkali metal compound as a polymerization initiator to form a conjugated diene polymer;

(ii) (ii) after (i), further adding an alkali metal compound to the conjugated diene-based polymer; and is

(iii) (iii) reacting the product obtained in (ii) with a modifying agent to introduce a modifying group into the conjugated diene-based polymer.

(i) The step of anionically polymerizing the conjugated diene compound alone or the conjugated diene compound and the aromatic vinyl compound in the presence of the alkali metal compound as a polymerization initiator to form the conjugated diene-based polymer (hereinafter also simply referred to as "step (i)") can be carried out in the same manner as the conventionally known anionic polymerization described in, for example, JP 2013-249379A, JP 2016-003246A and JP 2014-227458A. Examples of the conjugated diene compound and examples of the aromatic vinyl compound are as described above.

Herein, the compound containing at least a conjugated diene compound (optionally containing an aromatic vinyl compound described below) used for forming the conjugated diene polymer in the step (i) is also collectively referred to as "monomer".

In one embodiment, the aromatic vinyl compound preferably comprises styrene and 1 or more selected from the group consisting of alkylstyrenes and halogenated alkylstyrenes. This makes it easier to introduce modifying groups.

In one embodiment, the total content of 1 or more selected from the group consisting of alkylstyrenes and halogenated alkylstyrenes is preferably 0.1 to 3% by mass with respect to the monomers forming the conjugated diene polymer. Therefore, excellent low loss factor and durability are achieved while securing operability during manufacturing.

In one embodiment, the alkylstyrene is preferably 4-methylstyrene and the haloalkylstyrene is preferably 4-chloromethylstyrene. This makes it easier to introduce modifying groups.

The alkali metal compound used as the polymerization initiator may be a known alkali metal compound for anionic polymerization. Examples of the alkali metal atom (M) include Li, Na, K, Rb and Cs. Examples of the alkali metal compound include organic alkali metal compounds and organic alkaline earth metal compounds. The alkali metal compound is preferably an organic alkali metal compound.

Examples of the organic alkali metal compound include hydrocarbyl lithium and lithium amide compounds.

The hydrocarbyl lithium preferably has a hydrocarbyl group having, for example, 2 to 20 carbon atoms, and examples include ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, isobutyllithium, sec-butyllithium, tert-octyllithium, n-decyllithium, phenyllithium, 2-naphthyllithium, 2-butylphenyllithium, 4-phenylbutyllithium, cyclohexyllithium, cyclopentyllithium, and a reaction product of diisopropenylbenzene and butyllithium.

Examples of the lithium amide compound include lithium hexamethyleneimide, lithium pyrrolidine, lithium piperidine, lithium heptamethyleneimide, lithium dodecamethyleneimide, lithium dimethylamide, lithium diethylamide, lithium dibutylamide, lithium dipropylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium N-methylpiperazine, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide and lithium methylphenylethylamide.

The alkali metal compound used in the step (i) is preferably n-butyllithium from the viewpoint of more efficiently synthesizing the modified conjugated diene polymer according to the present disclosure.

The amount of the alkali metal compound used in the step (i) can be appropriately adjusted. For example, the amount of the alkali metal compound may be in the range of 0.2mmol to 20mmol per 100 parts by mass of the monomers forming the modified conjugated diene polymer.

In the step (ii) of further adding an alkali metal compound to the conjugated diene polymer after (i) (hereinafter also simply referred to as "step (ii)"), examples of the alkali metal atom (M) of the added alkali metal compound include Li, Na, K, Rb and Cs.

For the alkali metal compound added in the step (ii), the same description as for the alkali metal compound in the step (i) applies. The alkali metal compound in the step (i) and the alkali metal compound in the step (ii) may be the same or different.

The alkali metal compound used in the step (ii) is preferably sec-butyl lithium from the viewpoint of more efficiently synthesizing the modified conjugated diene polymer according to the present disclosure.

From the viewpoint of more efficiently synthesizing the modified conjugated diene-based polymer according to the present disclosure, it is preferable that the alkali metal compound used in the step (i) is n-butyllithium, and the alkali metal compound used in the step (ii) is sec-butyllithium.

By further adding an alkali metal compound in step (ii) subsequent to step (i), an alkali metal atom is introduced into a portion other than one end of the polymer main chain (for example, a portion between the ends of the polymer main chain) of the conjugated diene-based polymer formed in step (i) (that is, a hydrogen atom of the hydrocarbon chain is replaced by an alkali metal atom), and the introduced alkali metal atom reacts with the modifier, thereby introducing a modifying group capable of intermolecular non-covalent bond formation. Therefore, the number of modifying groups per molecule in the modified conjugated diene polymer may be 2 or more.

In the case where the step (ii) is not performed in the production method including the steps (i), (ii), and (iii), typically, the alkali metal is introduced only to the polymerization active terminal of the conjugated diene polymer, and the modifying group is introduced only to the terminal. Therefore, in the case where the step (ii) is not performed, the number of the modifying groups per molecule in the modified conjugated diene polymer is 1.

As an example, in the case where styrene is used as the aromatic vinyl compound, the portion to which the alkali metal atom is introduced in the step (ii) is a tertiary carbon atom of the portion to which styrene is bonded to the main chain of the polymer. As another example, in the case where styrene and 4-methylstyrene are used as the aromatic vinyl compound, in addition to the tertiary carbon atom of the bonding portion of styrene to the polymer main chain, an alkali metal atom is introduced into the tertiary carbon atom of the bonding portion of 4-methylstyrene to the polymer main chain and the primary carbon atom of the methyl group at the 4-position. In this case, it is considered that the alkali metal atom is preferentially introduced into the primary carbon atom because the steric hindrance of the primary carbon atom is smaller than that of the tertiary carbon atom. It is also considered that, in a polymer system not containing an aromatic vinyl compound, although the activity is lower than that in the case of the aromatic vinyl compound, an allylic hydrogen atom reacts with an alkali metal atom of an alkali metal compound additionally added, thereby introducing the alkali metal atom.

The amount of the alkali metal compound added in the step (ii) can be appropriately adjusted. For example, the amount of the alkali metal compound added in the step (ii) may be in the range of 0.2mmol to 20mmol per 100 parts by mass of the monomer for forming the modified conjugated diene polymer.

The ratio ((ii)/(i)) between the amount (mmol) of the alkali metal compound added in the step (i) and the amount of the alkali metal compound added in the step (ii) is preferably 0.5 to 100, and more preferably 0.9 to 20.

In the case where the aromatic vinyl compound contains styrene and 1 or more selected from the group consisting of alkylstyrenes and haloalkylstyrenes, the amount of the alkali metal compound added in the step (ii) is, for example, in the range of 0.1 to 3mmol, and preferably in the range of 0.1 to 1mmol, per 100 parts by mass of the monomer forming the modified conjugated diene polymer. Therefore, excellent low loss factor and durability are achieved while securing operability.

In the case of using the production method including the steps (i), (ii), and (iii), the number of modifying groups per molecule in the modified conjugated diene-based polymer is calculated according to the following expression:

(amount of substance (mmol) of the alkali metal compound added in the step (ii))/((amount (g) of monomer to be charged to form the modified conjugated diene polymer))/(number average molecular weight Mn of the modified conjugated diene polymer)).

In the production method including the steps (i), (ii), and (iii), the method of setting the number of the modifying groups per molecule in the modified conjugated diene polymer to 2 or more includes, for example, increasing the amount of the alkali metal added in the step (ii) and/or increasing the amount of the aromatic vinyl compound as a monomer.

In the step (iii) of reacting the product obtained in (ii) with a modifier to introduce a modifying group into the conjugated diene polymer (hereinafter also simply referred to as "step (iii)"), examples of the modifier used include carbon dioxide gas (carbon dioxide) and carbon disulfide.

The modifier is preferably carbon dioxide gas. This facilitates the introduction of polar groups into the non-polar polymer.

The amount of the modifier is not limited and may be appropriately adjusted. For example, in the case where carbon dioxide gas is used as the modifier, carbon dioxide gas is blown into the solution containing the product of step (ii) until the color of the solution disappears.

For example, in the case where carbon dioxide gas is used as the modifier, the modifying group is-COOM. For example, in the case where an aldehyde such as acetaldehyde is used as the modifier, the modifying group is-OM.

The following scheme shows examples of the steps (i) to (iii) in the case where butadiene is used as the conjugated diene compound, styrene and 4-methylstyrene are used as the aromatic vinyl compound, n-butyllithium is used as the alkali metal compound in the step (i), sec-butyllithium is used as the alkali metal compound in the step (ii), and carbon dioxide gas is used as the modifier in the step (iii). For the sake of simplicity, this example shows an intermediate product in which only the methyl group moiety at the 4-position of the 4-methylstyrene unit of the conjugated diene-based polymer is introduced into the Li atom in the step (ii). However, it is also possible to introduce Li atoms into the tertiary carbon atoms, labeled as ×, carbon atoms in the following formula, i.e., the bonding portion of styrene to the polymer main chain and the bonding portion of 4-methylstyrene to the polymer main chain.

[ chemical formula 1]

The modified conjugated diene-based polymer obtained in this example has-COOLi as a modifying group, and for example, an O atom of a carbonyl group in the modifying group coordinates with a Li atom in the modifying group of another modified conjugated diene-based polymer molecule to form a coordinate bond as a non-covalent bond. Since the coordination number of the Li atom is 4, O atoms of the carbonyl groups of the modifying groups in the other two modified conjugated diene polymer molecules can coordinate to the Li atom.

In the above-mentioned production method, the steps (ii) and (iii) may be carried out simultaneously, or the step (iii) may be carried out after the step (ii).

The production method may include, for example, a step of washing the modified conjugated diene polymer obtained in the step (iii) in addition to the steps (i), (ii), and (iii). The solvent used in the washing is not limited and may be appropriately selected depending on the intended use. Examples of the solvent include methanol, ethanol, isopropanol, water and buffered water.

In the present disclosure, it is preferable not to add an acid to the modified conjugated diene-based polymer. The addition of the acid may result in, for example, removal of lithium from the modified conjugated diene-based polymer and result in no coordination bond.

Instead of the step (i), the conjugated diene polymer (base polymer) may be formed by a known production method. For example, the conjugated diene polymer can be formed by using the method for producing a multipolymer described in any one of JP 2017-101181A and WO2015/190072a 1.

< Natural rubber >

The rubber composition according to the present disclosure includes natural rubber as a rubber component. Since the natural rubber is blended with the modified conjugated diene polymer, durability (crack resistance) and wear resistance can be improved while maintaining a low loss factor at a high level. 1 kind of natural rubber may be used alone, or 2 or more kinds of natural rubber may be used in combination.

< other rubber Components >

The rubber composition according to the present disclosure may or may not contain a rubber component other than the above-described modified conjugated diene-based polymer and natural rubber. Such other rubber component may be appropriately selected from known rubber components. Examples of the other rubber component include synthetic isoprene rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, a bromide of a copolymer of isobutylene and p-methylstyrene, halogenated butyl rubber, acrylonitrile-butadiene rubber, chloroprene rubber, ethylene-propylene-diene rubber, styrene-isoprene-butadiene rubber, chlorosulfonated polyethylene, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluorine rubber, and polyurethane rubber. These other rubber components may be used alone or in combination of 2 or more.

< other Components >

In addition to the aforementioned rubber components, the rubber composition according to the present disclosure may be appropriately compounded with known additives contained in the rubber composition. Examples of such additives include fillers, vulcanizing agents (crosslinking agents), vulcanization accelerators, age resistors, reinforcing agents, softening agents, vulcanization aids, colorants, flame retardants, lubricants, foaming agents, plasticizers, processing aids, antioxidants, scorch retarders, ultraviolet ray protectors, antistatic agents, color stabilizers, and oils. These additives may be used alone or in combination of 2 or more.

The rubber composition according to the present disclosure preferably further comprises a filler. This contributes to better low loss and durability. In addition, wet grip performance is improved.

< Filler >

Examples of the filler include inorganic fillers and carbon black. These may be used alone or in combination of 2 or more. Herein, carbon black is not included in the filler.

Examples of the inorganic filler include silica, aluminum hydroxide, clay, alumina, talc, mica, kaolin, glass spheres, glass beads, calcium carbonate, magnesium hydroxide, magnesium oxide, titanium oxide, potassium titanate, and barium sulfate.

In the case of using an inorganic filler, the inorganic filler may be suitably surface-treated using, for example, a silane coupling agent.

Examples of carbon blacks include those of the GPF (general furnace black), FEF (rapid extrusion furnace black), SRF (semi-reinforced furnace black), HAF (high abrasion furnace black), SAF (super abrasion furnace black) and ISAF (intermediate SAF) grades.

In the case where the rubber composition according to the present disclosure contains a filler, the content of the filler may be appropriately adjusted. For example, the filler is contained in an amount of 5 to 200 parts by mass, 10 to 200 parts by mass, or 10 to 130 parts by mass, relative to 100 parts by mass of the rubber component.

< vulcanizing agent (crosslinking agent) >

The vulcanizing agent (crosslinking agent) is not limited and may be appropriately selected. Examples of the vulcanizing agent include a sulfur-containing vulcanizing agent, an organic peroxide-containing vulcanizing agent, an inorganic vulcanizing agent, a polyamine vulcanizing agent, a resin vulcanizing agent, a sulfur compound-based vulcanizing agent, an oxime-nitrosamine-based vulcanizing agent, and sulfur.

In the case where the rubber composition according to the present disclosure contains a vulcanizing agent, the content of the vulcanizing agent may be appropriately adjusted. For example, the vulcanizing agent is contained in an amount of 0.1 to 20 parts by mass or 0.1 to 10 parts by mass per 100 parts by mass of the rubber component.

< vulcanization accelerators >

The vulcanization accelerator is not limited and may be appropriately selected. Examples of the vulcanization accelerator include guanidine-based compounds, aldehyde-amine-based compounds, aldehyde-ammonia-based compounds, thiazole-based compounds, sulfenamide-based compounds, thiourea-based compounds, thiuram-based compounds, dithiocarbamate-based compounds, and xanthate-based compounds.

In the case where the rubber composition according to the present disclosure contains a vulcanization accelerator, the content of the vulcanization accelerator may be appropriately adjusted. For example, the content of the vulcanization accelerator is 0.1 to 20 parts by mass or 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

The method for preparing the rubber composition according to the present disclosure is not limited, and a known method may be used. For example, the rubber composition is obtained by mixing all the components including the modified conjugated diene polymer and the natural rubber using a mixer such as a Banbury mixer, a roll or an internal mixer. The rubber composition may be prepared by mixing components other than the vulcanization accelerator and the vulcanizing agent in a non-production stage, and compounding and mixing the vulcanization accelerator and the vulcanizing agent in the mixture in a production stage.

(rubber product)

The rubber article obtained using the rubber composition according to the present disclosure is not limited, and examples include tires, conveyor belts, vibration-proof rubbers, vibration-isolating rubbers, rubber tracks, hoses, and foams.

The method for obtaining a rubber article using the rubber composition according to the present disclosure is not limited, and a known method may be used. The conditions for crosslinking or vulcanizing the rubber composition can be appropriately adjusted. For example, the temperature may be 120 ℃ to 200 ℃, and the heating time may be 1 minute to 900 minutes.

(tire)

The tire according to the present disclosure includes the above rubber composition. The rubber composition according to the present disclosure may be used in any portion of a tire. Examples of the portion include tread rubber, under tread rubber, sidewall reinforcing rubber, and bead filler.

The manufacturing method of the tire is not limited, and a known method may be used.

Examples

The techniques of the present disclosure will be described in more detail below by way of examples, although these examples are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. In the examples, the blending amounts are in parts by mass unless otherwise specified.

Details of the materials used in the examples are as follows:

-natural rubber: RSS # 3.

-modified conjugated diene polymer: modified SBR was prepared by the following method.

-carbon black: HAF, "N234" manufactured by Tokai Carbon co.

-an oil: "JOMO PROCESS NC300 BN" manufactured by JX Nippon Oil & Energy Corporation.

-wax: trade name manufactured by Seiko-Chemical Co., Ltd ""(SUNTIGHT is a registered trademark in japan, other countries, or both).

-anti-ageing agents: n- (1, 3-dimethylbutyl) -N' -phenyl-p-phenylenediamine, trade name manufactured by Ouchi Shinko Chemical Industrial Co., Ltd "6C "(NORAC is a registered trademark in Japan, other countries, or both).

-sulfurA promoting agent: n- (cyclohexyl) -2-benzothiazolesulfenamide, trade name manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.CZ-G "(NOCCELER is a registered trademark in Japan, other countries, or both).

In the examples, the energy of each non-covalent bond between the modifying groups in the modified conjugated diene-based polymer was determined by the aforementioned method. In the examples, the vinyl content of the butadiene fraction of the polymers (indicated as Vi in the tables) [% ]]And styrene content (expressed as St in the table) [% ]]By¹And (4) determining an integral ratio of H-NMR. The weight average molecular weight of the polymer is determined by the method described previously.

In the examples, the number of modifying groups in the modified conjugated diene-based polymer was calculated by the aforementioned method.

Preparation of COOLi-modified SBR

In step (i), cyclohexane (240g), a butadiene/cyclohexane solution (25% by mass, 194g), a styrene/cyclohexane solution (27% by mass, 46g), and 4-methylstyrene (480mg) were added to a dried bottle under an inert atmosphere, and then a 2, 2-bis- (2-tetrahydrofuryl) propane/cyclohexane solution (1M, 0.35mL) and n-butyllithium (1.6M, 0.42mL) were added thereto. The vial was slowly shaken at 50 ℃ for 1 hour to confirm completion of the polymerization. Formation of a conjugated diene polymer was confirmed.

In step (ii), N' -tetramethylethylenediamine (418mg) and sec-butyllithium (1.0M, 4.0mL) were added to the solution containing the conjugated diene polymer obtained in step (i), and the mixture was shaken at 70 ℃ for 2 hours.

In the step (iii), carbon dioxide gas is blown into the solution obtained in the step (ii) until the color disappears, to complete the modification reaction.

Subsequently, 0.5mL of an isopropanol solution of 2, 6-di-t-butyl-p-cresol (BHT) (BHT concentration: 5 mass%) was added to the obtained polymer cement, followed by precipitation with isopropanol and drying under reduced pressure to obtain the objective modified styrene-butadiene copolymer (COOLi-modified SBR).

The rubber compositions were manufactured using a typical banbury mixer according to the formulations listed in tables 1 and 2. For each rubber composition, the tensile stress at 100% elongation (expressed as 100% stress in table 2) was measured as follows in accordance with JIS K6251. Further, with respect to the rubber vulcanizate obtained by vulcanizing each rubber composition at 160 ℃ for 20 minutes, the low loss factor, the crack growth resistance and the wear resistance were evaluated as follows. The results are shown in Table 2.

[ Table 1]

[ Table 2]

< tensile stress at 100% elongation >

For each rubber composition, a JIS dumbbell No. 3 test piece was manufactured in accordance with JIS K6251, and the tensile stress (MPa) at 100% elongation was measured at a test temperature of 24 ± 4 ℃.

< Low loss factor >

Loss tangent (tan δ) was measured using a viscoelastometer manufactured by TA Instruments at a temperature of 50 ℃, a frequency of 15Hz, and a strain of 10%. The results were expressed as an index in which the value of comparative example 1 was set to 100, taking the reciprocal of the tan δ value. A larger index indicates better low loss.

< crack resistance >

A0.5 mm crack was formed in the center of a JIS3 test piece, and the test piece was subjected to repeated fatigue tests at room temperature with a set strain of 40% to 150%. The number of times until the sample broke was measured. The results are expressed as an index in which the value of comparative example 1 is set to 100. A larger index indicates better crack resistance (durability).

< wear resistance >

For each rubber vulcanizate, the abrasion loss was measured at 25% slip rate at room temperature using a lambert abrasion tester. The results were expressed as an index in which the reciprocal of the abrasion loss of the rubber vulcanizate of comparative example 1 was set to 100. A larger index indicates less wear loss and better wear resistance.

As can be seen from table 2, the examples have excellent durability (crack resistance) and wear resistance while maintaining low loss properties at a high level. The stress of the examples was also improved. Even in the case where the rubber has a high stress, the durability (crack resistance) is improved. By reducing the stress, the durability can be further improved.

Industrial applicability

It is possible to provide a rubber composition having excellent durability (crack resistance) and wear resistance while maintaining a low loss factor at a high level. It is also possible to provide a tire having excellent durability (crack resistance) and wear resistance while maintaining a low loss factor at a high level.