JP6699686B2 - Modified isoprene polymer and rubber composition - Google Patents

Description

  The present invention relates to modified isoprene polymers and rubber compositions.

  Generally, a rubber filler containing natural rubber or the like used in tires or the like is mixed with a reinforcing filler such as carbon black or silica. On the other hand, due to the interaction between the reinforcing fillers, the reinforcing fillers may aggregate in the rubber composition and sufficient characteristics (eg, processability, low heat build-up, and abrasion resistance) may not be obtained. .

  Under such circumstances, a rubber composition in which epoxidized natural rubber or the like is mixed with natural rubber has been proposed (for example, Patent Document 1).

JP, 2010-77257, A

  The present inventors have studied a rubber composition in which an epoxidized natural rubber is mixed with a natural rubber and a reinforcing filler with reference to Patent Document 1, and as a result, the dispersibility of the reinforcing filler in the obtained rubber composition has been investigated. (Hereinafter, "dispersibility of the reinforcing filler" is also simply referred to as "dispersibility") and characteristics have not been found to satisfy the levels currently required.

  Therefore, in view of the above circumstances, the present invention aims to provide a rubber composition exhibiting excellent dispersibility, low heat build-up and abrasion resistance when used in a rubber composition containing a reinforcing filler. And

When the present inventors focused their attention on the (synthetic) isoprene polymer, it was found that the isoprene polymer having a specific functional group at the end can significantly improve the dispersibility of the reinforcing filler. It was
The present invention is based on the above findings, and its specific configuration is as follows.

(1) containing a rubber component containing a modified isoprene polymer and a reinforcing filler,
The reinforcing filler contains carbon black and/or silica,
The modified isoprene polymer has a functional group containing a nitrogen atom and a silicon atom at the terminal,
A rubber composition, wherein the modified isoprene polymer has a weight average molecular weight of 100,000 or more and 10,000,000 or less.
(2) The rubber composition according to (1), wherein the content of the modified isoprene polymer is 1 to 50 parts by mass with respect to 100 parts by mass of the rubber component.
(3) The rubber composition according to (1) or (2), wherein the content of the reinforcing filler is 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component.
(4) The nitrogen adsorption specific surface area (N ₂ SA) of the silica is 140 m ² /g or more,
The silica has a CTAB specific surface area (CTAB) of 150 m ² /g or more,
The rubber composition according to any one of (1) to (3) above, wherein the ratio of the nitrogen adsorption specific surface area to the CTAB adsorption specific surface area is 0.8 to 1.4.
(5) Containing the above silica, and further containing a silane coupling agent,
The rubber composition according to any one of (1) to (4) above, wherein the content of the silane coupling agent is 1 to 20 mass% with respect to the content of the silica.
(6) The rubber composition according to any one of (1) to (5), wherein the modified isoprene polymer has a molecular weight distribution of 2.0 or less.
(7) The rubber composition as described in any of (1) to (6) above, wherein the rubber component further contains natural rubber.

  As shown below, the present invention can provide a rubber composition exhibiting excellent dispersibility, low heat build-up and abrasion resistance.

The rubber composition of the present invention will be described below.
In addition, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

[Rubber composition]
The rubber composition of the present invention (hereinafter, also referred to as “composition of the present invention”) is
A rubber component containing a modified isoprene polymer, and a reinforcing filler,
The reinforcing filler contains carbon black and/or silica,
The modified isoprene polymer has a functional group containing a nitrogen atom and a silicon atom at the terminal,
The modified isoprene polymer has a weight average molecular weight of 100,000 or more and 10,000,000 or less.

The modified isoprene polymer contained in the rubber composition of the present invention has a functional group containing a nitrogen atom and a silicon atom (hereinafter, also referred to as “specific functional group”) at the terminal, and has a weight average molecular weight of 100,000 or more. It is an isoprene polymer (isoprene polymer) which is less than 1,000,000.
Hereinafter, the modified isoprene polymer contained in the composition of the present invention is also referred to as "specifically modified IR".

It is considered that the composition of the present invention has such a constitution that the reinforcing filler in the rubber composition exhibits excellent dispersibility.
The reason is not clear in detail, but the nitrogen atom and the silicon atom in the specific functional group of the specific modified IR interact with the reinforcing filler to prevent the reinforcing filler from aggregating, and as a result, It is speculated that the dispersibility of the reinforcing filler is greatly improved.

[Rubber component]
The composition of the present invention contains a rubber component, and the rubber component contains a specific modified IR.

[Specific modified isoprene polymer]
Hereinafter, the modified isoprene polymer (specifically modified IR) will be described in detail.
As described above, the specific modified IR has a functional group (specific functional group) containing a nitrogen atom and a silicon atom at the end, and has a weight average molecular weight of 100,000 or more and 10,000,000 or less (isoprene polymer (modified Isoprene polymer).

[Specific functional group]
As described above, the specific modified IR has a functional group (specific functional group) containing a nitrogen atom and a silicon atom at the end. The specific modified IR may have a specific functional group at least at one end of the specific modified IR.

<Preferable embodiment>
The specific functional group is not particularly limited as long as it is a functional group containing a nitrogen atom and a silicon atom, but for the reason that the effect of the present invention is more excellent, the nitrogen atom is replaced with an amino group (-NR ₂ : R is a hydrogen atom or a hydrocarbon group). And a silicon atom is preferably contained as a hydrocarbyloxysilyl group (≡SiOR:R is a hydrocarbon group).

  The specific functional group is preferably a group represented by the following formula (M) because the effect of the present invention is more excellent.

In the above formula (M), R ₁ and R ₂ each independently represent a hydrogen atom or a substituent.
In the above formula (M), L represents a divalent organic group.

The substituent is not particularly limited as long as it is a monovalent substituent, and examples thereof include a halogen atom, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an amino group, a mercapto group, an acyl group, an imide group, a phosphino group and a phosphinyl group. Group, a silyl group, a hydrocarbon group which may have a hetero atom, and the like.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.
Examples of the hetero atom of the hydrocarbon group which may have a hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom and a phosphorus atom.
Examples of the hydrocarbon group which may have a hetero atom include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a group in which these are combined.
The aliphatic hydrocarbon group may be linear, branched or cyclic. Specific examples of the aliphatic hydrocarbon group include a linear or branched alkyl group (especially 1 to 30 carbon atoms), a linear or branched alkenyl group (especially 2 to 30 carbon atoms), A straight-chain or branched alkynyl group (in particular, having 2 to 30 carbon atoms) and the like can be mentioned.
Examples of the aromatic hydrocarbon group include an aromatic hydrocarbon group having 6 to 18 carbon atoms such as a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

In the above formula (M), R ₁ is a hydrogen atom, an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably having 1 to 10 carbon atoms) for the reason that the effect of the present invention is more excellent. It is preferably an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), and more preferably a hydrogen atom.
Plural R ₁ may be the same or different.
When a plurality of R _{1 s} are different, a combination of a plurality of R ₁ s is a hydrogen atom, an alkyl group (preferably having a carbon number of 1 to 10), an alkylsilyl group (preferably C1-10) or an aromatic hydrocarbon group (preferably C6-18) is preferable, and a hydrogen atom and an alkylsilyl group (preferably C1-10) are more preferable. A combination of a hydrogen atom and a trialkylsilyl group (preferably having a carbon number of 1 to 10) is more preferable.

From the reason that the effect of the present invention is more excellent, R ₂ is preferably a hydrocarbyloxy group (—OR group: R is a hydrocarbon group), and an alkoxy group (preferably having 1 to 10 carbon atoms). More preferable.

As described above, in the formula (M), L represents a single bond or a divalent organic group.
As the divalent organic group, for example, an aliphatic hydrocarbon group (for example, an alkylene group, preferably 1 to 10 carbon atoms), an aromatic hydrocarbon group (for example, an arylene group, preferably 6 to 18 carbon atoms), _{-O -, - S -, -} SO 2 -, - N (R) - (R: alkyl group), - CO -, - NH -, - COO -, - CONH-, or a group formed by combining these (e.g. , alkyleneoxy radical _{(-C m} H 2m O-: _m is a positive integer), alkyleneoxy carbonyl group, an alkylene carbonyl group) and the like.
L is preferably an alkylene group (preferably having 1 to 10 carbon atoms) for the reason that the effect of the present invention is more excellent.

In the above formula (M), n represents an integer of 0-2.
n is preferably 2 because the effect of the present invention is more excellent.

In the above formula (M), m represents an integer of 1 to 3.
m is preferably 1 because the effect of the present invention is more excellent.

  In the above formula (M), n and m satisfy the relational expression of n+m=3.

  In the above formula (M), * represents a bonding position.

(Weight average molecular weight)
As described above, the weight average molecular weight (Mw) of the specific modified IR is 100,000 or more and 10,000,000 or less. Above all, from the reason that the effect of the present invention is more excellent, it is preferably more than 200,000 and 1,000,000 or less, and more preferably 250,000 or more and 800,000 or less.

[Number average molecular weight]
The number average molecular weight of the specific modified IR is not particularly limited as long as the weight average molecular weight of the specific modified IR is within a specific range, but for the reason that the effect of the present invention is more excellent, it is preferably 120,000 to 900,000, More preferably, it is more than 150,000 and 800,000 or less.

[Molecular weight distribution]
The molecular weight distribution (Mw/Mn) of the specific modified IR is not particularly limited as long as the weight average molecular weight of the specific modified IR is within the specific range, but is preferably 2.0 or less for the reason that the effect of the present invention is more excellent. It is more preferably 1.7 or less, further preferably 1.5 or less, and particularly preferably 1.3 or less.
The lower limit is not particularly limited, but is usually 1.0 or more.

In this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are standard polystyrene equivalent values obtained by gel permeation chromatography (GPC) measurement under the following conditions.
・Solvent: Tetrahydrofuran ・Detector: RI detector

[Micro structure]
<1,2-Structure and 3,4-Structure>
In the specific modified IR, the ratio of the 1,2-structure and the 3,4-structure is not particularly limited, but is preferably 0 to 10 mol% and 0 to 5 mol% for the reason that the effect of the present invention is more excellent. Is more preferable.
Here, the proportion of the 1,2-structure means the proportion (mol %) of the repeating units having the 1,2-structure in the repeating units derived from isoprene. Further, the proportion of 3,4-structure means the proportion (mol %) of the repeating units having the 3,4-structure in the repeating units derived from isoprene.

<1,4-transformer structure>
In the specific modified IR, the proportion of the 1,4-trans structure is not particularly limited, but is preferably 2 to 90 mol%, more preferably 5 to 70 mol% for the reason that the effect of the present invention is more excellent. preferable.
Here, the proportion of the 1,4-trans structure means the proportion (mol %) of the repeating units having the 1,4-trans structure in all the repeating units derived from isoprene.

<1,4-cis structure>
In the specific modified IR, the ratio of the 1,4-cis structure is not particularly limited, but is preferably 10 to 98 mol% and more preferably 30 to 98 mol% for the reason that the effect of the present invention is more excellent. preferable.
Here, the proportion of the 1,4-cis structure means the proportion (mol %) of the repeating units having the 1,4-cis structure in all the repeating units derived from isoprene.

  In addition, hereinafter, "total of the ratio of 1,2-structure and 3,4-structure (mol %), ratio of 1,4-trans structure (mol %), ratio of 1,4-cis structure (mol %)" Is also referred to as "1,2- and 3,4-/trans/cis".

〔Glass-transition temperature〕
The glass transition temperature (Tg) of the specific modified IR is not particularly limited, but is preferably −100 to −40° C., more preferably −90 to −50° C. for the reason that the effect of the present invention is more excellent. , -85 to -60°C is more preferable.
In the present specification, the glass transition temperature (Tg) is measured by a differential scanning calorimeter (DSC) at a temperature rising rate of 10° C./min and calculated by the midpoint method.

〔viscosity〕
The viscosity of the specific modified IR is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably more than 2,000 Pa·s, more preferably 3,000 to 100,000 Pa·s.
Further, the viscosity of the isoprene polymer before the modification of the specific modified IR is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably more than 800 Pa·s, and 1,200 to 8,000 Pa·s. Is more preferable.
Further, the viscosity of the specific modified IR is preferably 150 to 240% with respect to the viscosity of the isoprene polymer before modification because the effect of the present invention is more excellent. Hereinafter, the viscosity of the characteristic modified IR after modification with respect to the specific modified IR before modification is also referred to as “viscosity (after modification/before modification)”.
In addition, in this specification, the viscosity shall be measured using a cone-plate viscometer according to JIS K5600-2-3. In addition, the viscosity is assumed to be measured under the condition of 40°C.

[Method for producing specific modified IR]
The method for producing the specific modified IR is not particularly limited, and a conventionally known method can be used. The method of setting the molecular weight and the molecular weight distribution in a specific range is not particularly limited, and examples thereof include a method of adjusting the ratio of the amount of the initiator, the monomer and the terminating agent, the reaction temperature, the rate of adding the initiator, and the like.

<Preferable embodiment>
As a preferred embodiment of the method for producing the specific modified IR, for example, a method of polymerizing isoprene using an organolithium compound, and then terminating the polymerization using an electrophile containing a nitrogen atom and a silicon atom (hereinafter, (Also referred to as the “method of the present invention”). When the method of the present invention is used, the obtained specific modified IR exhibits more excellent dispersibility, processability, low heat build-up and abrasion resistance when used in a rubber composition containing a reinforcing filler. ..

(Organic lithium compound)
The organolithium compound is not particularly limited, but specific examples thereof include monoorganolithium compounds such as n-butyllithium, sec-butyllithium, tert-butyllithium, n-propyllithium, iso-propyllithium, and benzyllithium; 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10-dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dilithio Benzene, 1,2-dilithio-1,2-diphenylethane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, 1,3,5-trilithio-2,4,6- Examples include polyfunctional organolithium compounds such as triethylbenzene. Of these, monoorganolithium compounds of n-butyllithium, sec-butyllithium, and tert-butyllithium are preferable because the effect of the present invention is more excellent.

  The amount of the organolithium compound used is not particularly limited, but is preferably 0.001 to 10 mol% relative to isoprene for the reason that the effect of the present invention is more excellent.

(Polymerization of isoprene)
The method of polymerizing isoprene using an organolithium compound is not particularly limited, but the organolithium compound described above is added to an organic solvent solution containing isoprene, and the temperature range of 0 to 120° C. (preferably 30 to 100° C.) is used. Examples include a method of stirring.

(Specific electrophile)
In the method of the present invention, the polymerization of isoprene is stopped by using an electrophile containing a nitrogen atom and a silicon atom (hereinafter, also referred to as “specific electrophile”). By stopping the polymerization with the specific electrophile, the modified isoprene polymer having the specific functional group at the terminal can be obtained.
The specific electrophile is not particularly limited as long as it is a compound containing a nitrogen atom and a silicon atom, but for the reason that the effect of the present invention is more excellent, the nitrogen atom is replaced with an amino group (-NR ₂ : R is a hydrogen atom or a hydrocarbon group). And a silicon atom is preferably contained as a hydrocarbyloxysilyl group (≡SiOR:R is a hydrocarbon group).

  The specific electrophile is preferably silazane, and more preferably cyclic silazane, because the effect of the present invention is more excellent. Here, the silazane is intended to mean a compound having a structure in which a silicon atom and a nitrogen atom are directly bonded (a compound having a Si—N bond).

  The cyclic silazane is preferably a compound represented by the following formula (S) because the effect of the present invention is more excellent.

In the formula (S), R _{1 to} R ₃ each independently represent a hydrogen atom or a substituent. Specific examples and preferred embodiments of the substituents are the same as R ₁ and R _{2 in the} above formula (M).
In the above formula (S), L represents a divalent organic group. Specific examples and preferred embodiments of the divalent organic group are the same as L in the above formula (M).

In the above formula (S), R ₁ is an alkyl group (preferably having a carbon number of 1 to 10), an alkylsilyl group (preferably having a carbon number of 1 to 10), an aromatic group for the reason that the effect of the present invention is more excellent. A hydrocarbon group (preferably having 6 to 18 carbon atoms) is preferable, and an alkylsilyl group is more preferable.

In the formula (S), R ₂ and R ₃ are preferably each independently a hydrocarbyloxy group (—OR group: R is a hydrocarbon group), and an alkoxy group, for the reason that the effect of the present invention is more excellent. (Preferably, having 1 to 10 carbon atoms) is more preferable.

  In the above formula (S), L is preferably an alkylene group (preferably having 1 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, and further preferably 3 to 5 carbon atoms) for the reason that the effect of the present invention is more excellent. ..

Examples of the compound represented by the formula (S) include N-n-butyl-1,1-dimethoxy-2-azasilacyclopentane and N-phenyl-1,1-dimethoxy-2-azasilacyclopentane. , N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-diethoxy-2-azasilacyclopentane, and the like.
The silicon atom of the cyclic silazane is considered to exhibit electrophilicity.

  The amount of the specific electrophile with respect to the organolithium compound is not particularly limited, but for the reason that the effect of the present invention is more excellent, the molar ratio is preferably 0.1 to 10, and more preferably 1 to 5. .

(Rubber other than the specific modified IR)
The rubber component may further include a rubber other than the specific modified IR. The rubber other than the specific modified IR is not particularly limited.
The rubber other than the specific modified IR is preferably a diene rubber because the effect of the present invention is more excellent. Specific examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogen. Butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR) and the like. Among them, natural rubber, SBR or BR is preferable, and natural rubber is more preferable, because the effect of the present invention is more excellent.

  Since the basic skeleton of the specific modified IR is an isoprene polymer, a part or all of the diene rubber such as natural rubber that can be contained in the rubber composition can be replaced with the specific modified IR. By replacing a part or all of the diene rubber such as natural rubber with the specific modified IR as described above, the dispersibility of the reinforcing filler in the rubber composition can be made excellent.

  The natural rubber is not particularly limited. For example, conventionally known ones can be mentioned.

The content (styrene unit content) of the styrene unit (repeating unit derived from styrene) of the SBR is not particularly limited, but it is preferably 5 to 50 mass% for the reason that the effect of the present invention is more excellent.
The ratio of the vinyl structure of the SBR is not particularly limited, but is preferably 5 to 80%, more preferably 10 to 75%, and more preferably 20 to 70% for the reason that the effect of the present invention is more excellent. Is more preferable. Here, the proportion of the vinyl structure means the proportion (mol %) of the repeating units having a vinyl structure in the repeating units derived from butadiene.

<Weight average molecular weight>
The weight average molecular weight (Mw) of the rubber other than the specific modified IR is not particularly limited.
The method for measuring the weight average molecular weight is as described above.

(Content of specific modified IR)
The content of the specific modified IR is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the rubber component because the effect of the present invention is more excellent.
The content of the specific modified IR is preferably 1 to 40 parts by mass, and more preferably 3 to 15 parts by mass, from the viewpoint of being excellent in the effect of the present invention and being excellent in the balance of dispersibility, low heat generation property and abrasion resistance. More preferably.

<Glass transition temperature>
The glass transition temperature (Tg) of the rubber component is not particularly limited, but is preferably −60° C. or higher for the reason that the effect of the present invention is more excellent. The upper limit is not particularly limited, but is preferably 0° C. or lower and more preferably −20° C. or lower for the reason that the effect of the present invention is more excellent. The method for measuring Tg is as described above.
When the rubber component is an oil-extended product, the glass transition temperature of the rubber component is the glass transition temperature in a state in which the oil-extended component (oil) is not contained. When the rubber component contains two or more rubber components, the glass transition temperature of the rubber component is the average glass transition temperature. Here, the average glass transition temperature is the sum of the glass transition temperature of each rubber component multiplied by the mass fraction of each rubber component (the weighted average value of the glass transition temperature), and the mass fraction of all the rubber components. The total is 1.

[Reinforcing filler]
In the present invention, the reinforcing filler contained in the composition of the present invention contains silica and/or carbon black.
In the composition of the present invention, the content of the reinforcing filler is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component described above. It is preferably 50 to 100 parts by mass.
When the composition of the present invention contains two or more reinforcing fillers, the content of the reinforcing fillers means the total content.

<Silica>
The composition of the present invention preferably contains silica as a reinforcing filler because the effect of the present invention is more excellent.
The silica is not particularly limited, and any conventionally known silica can be used.
Examples of the silica include wet silica, dry silica, fumed silica, diatomaceous earth, and the like. As the above silica, one type of silica may be used alone, or two or more types of silica may be used in combination.

Although the nitrogen adsorption specific surface area (N ₂ SA) of the silica is not particularly limited, it is preferably 140 m ² /g or more, and more preferably 194 m ² /g or more for the reason that the effect of the present invention is more excellent. .. The upper limit of N ₂ SA in the silica is not particularly limited, but is preferably 300 m ² /g or less for the reason that the effect of the present invention is more excellent.
Here, N ₂ SA is a surrogate property of the surface area of silica that can be used for adsorption with rubber molecules, and the amount of nitrogen adsorbed on the surface of silica is defined in JIS K6217-2:2001 “Part 2: Determination of Specific Surface Area- It is a value measured according to "nitrogen adsorption method-single-point method".

The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of the silica (hereinafter, "CTAB adsorption specific surface area" is also simply referred to as "CTAB") is not particularly limited, but for the reason that the effect of the present invention is more excellent, 150 m ² /g It is preferably at least 185 m ² /g and more preferably at least 185 m ² /g. The upper limit of CTAB of the silica is not particularly limited, but is preferably 300 m ² /g or less for the reason that the effect of the present invention is more excellent.
Here, the CTAB adsorption specific surface area is a value obtained by measuring the amount of CTAB adsorbed on the surface of silica according to JIS K6217-3:2001 "Part 3: Determination of specific surface area-CTAB adsorption method".

The ratio of the silica nitrogen adsorption specific surface area to the CTAB adsorption specific surface area of silica (N ₂ SA/CTAB) is not particularly limited, but is preferably 0.8 to 1.4 for the reason that the effect of the present invention is more excellent.

  In the composition of the present invention, the content of silica is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 10 to 150 parts by mass with respect to 100 parts by mass of the rubber component described above, and 30 It is more preferable that the amount is ˜100 parts by mass.

<Carbon black>
The composition of the present invention preferably contains carbon black as a reinforcing filler because the effect of the present invention is more excellent. As the carbon black, one kind of carbon black may be used alone, or two or more kinds of carbon black may be used in combination.
The carbon black is not particularly limited, and examples thereof include various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF and SRF. Can be used.
The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is not particularly limited, but is preferably 50 to ²⁰⁰ m ² /g, and preferably 70 to 150 m ² /g for the reason that the effect of the present invention is more excellent. Is more preferable.
Here, the nitrogen adsorption specific surface area (N ₂ SA) is the nitrogen adsorption amount on the carbon black surface according to JIS K6217-2:2001 “Part 2: Determination of Specific Surface Area-Nitrogen Adsorption Method-Single Point Method”. It is the measured value.

  In the composition of the present invention, the content of carbon black is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the above-mentioned rubber component, It is more preferably 2 to 30 parts by mass.

〔Silane coupling agent〕
The composition of the present invention preferably further contains a silane coupling agent for the reason that the effect of the present invention is more excellent. The above silane coupling agents may be used alone or in combination of two or more.
When the composition of the present invention contains the silica as the reinforcing filler, the composition of the present invention may further include a silane coupling agent as one of preferred embodiments.
The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group.
The hydrolyzable group is not particularly limited, and examples thereof include an alkoxy group, a phenoxy group, a carboxyl group and an alkenyloxy group. Of these, an alkoxy group is preferable. When the hydrolyzable group is an alkoxy group, the alkoxy group preferably has 1 to 16 carbon atoms, and more preferably 1 to 4 carbon atoms. Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group and a propoxy group.

  The organic functional group is not particularly limited, but is preferably a group capable of forming a chemical bond with an organic compound, and examples thereof include an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a sulfide group, and a mercapto group. Of these, a sulfide group and a mercapto group are preferable.

  The silane coupling agent is preferably a sulfur-containing silane coupling agent.

  Specific examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxy. Silane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilyl Examples thereof include propyl-N,N-dimethylthiocarbamoyl-tetrasulfide, and of these, one kind may be used alone, or two or more kinds may be used in combination.

  In the composition of the present invention, the content of the silane coupling agent is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 1 to 20% by mass with respect to the content of silica described above, It is more preferably 5 to 20% by mass.

[Other ingredients]
The composition of the present invention may contain components (other components) other than the components described above, if necessary, within a range that does not impair the effect or purpose thereof.
Examples of such components include terpene resins (preferably aromatic modified terpene resins), heat-expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, waxes, processing aids, oils, Examples include liquid polymers, thermosetting resins, vulcanizing agents (for example, sulfur), vulcanization accelerators, and various other additives commonly used in rubber compositions.

[Use]
The composition of the present invention is suitable for use in tires, conveyor belts, hoses, anti-vibration materials, rubber rolls, outer hoods of railway vehicles, and the like. Among them, it is preferably used for tires.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, in this specification, Examples 3 and 6 shall be read as Reference Examples 3 and 6.

[Synthesis example]
Comparative non-modified IR1 and specific modified IR1-2 were synthesized as follows.
Here, each of the specific modified IRs 1 and 2 has a functional group represented by the formula (m1) described later that corresponds to the specific functional group at the end, and has Mw of 100,000 or more and 10 million or less. Corresponds to the above-mentioned “specifically modified IR”. On the other hand, the comparative unmodified IR1 has a Mw of 100,000 or more and 10 million or less, but does not correspond to the above-mentioned "specifically modified IR" because it does not have a specific functional group.

<Comparative unmodified IR1>
n-BuLi (n-butyllithium) (manufactured by Kanto Kagaku Co., Ltd.: 1.60 mol/L (hexane solution), 3.5 mL, 5.6 mmol) was mixed with cyclohexane (4.0 kg) of isoprene (945 g, 13.9 mol). The mixture was added to the solution and stirred at 50° C. for 6 hours. After the reaction, methanol (10 mL, 394 mmol) was added to stop the polymerization. The resulting solution was removed and concentrated under reduced pressure. The concentrated solution was poured into methanol (5.0 L) to separate a methanol-insoluble component.

<Specific modified IR1>
n-BuLi (manufactured by Kanto Kagaku Co., Ltd.: 1.60 mol/L (hexane solution), 9.0 mL, 14.4 mmol) was added to a cyclohexane (4.0 kg) mixed solution of isoprene (816 g, 12.0 mmol) to give 50. The mixture was stirred at 0°C for 6 hours. After the reaction, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (the following structure) (the following structure) (14 mL, 57.4 mmol) was added to terminate the polymerization. The resulting solution was removed and concentrated under reduced pressure. The concentrated solution was poured into methanol (5.0 L) to separate a methanol-insoluble component.

  As a result, a modified IR having a functional group represented by the following formula (m1) at a terminal (specific modified IR1) (Mn=243,000, Mw=292,000, Mw/Mn=1.20) was 92%. Obtained in yield. The IR analysis estimated 1,2- and 3,4-/trans/cis=8/0/92. Moreover, Tg was -61 degreeC. The viscosity of the specific modified IR1 was 8,100 Pa·s, and the viscosity (after modification/before modification) was 183%.

<Specific modified IR2>
n-BuLi (manufactured by Kanto Kagaku Co., Ltd.: 1.60 mol/L (hexane solution), 16.0 mL, 25.6 mmol) was added to a cyclohexane (4.1 kg) mixed solution of isoprene (805 g, 11.8 mmol) to give 50. The mixture was stirred at 0°C for 6 hours. After the reaction, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (7.0 mL, 28.7 mmol) was added to terminate the polymerization. The resulting solution was removed and concentrated under reduced pressure. The concentrated solution was poured into methanol (10 L) to separate a methanol-insoluble component. As a result, the modified IR (specific modified IR2) (Mn=15,000, Mw=150,000, Mw/Mn=1.18) having the functional group represented by the formula (m1) at the end was 97%. Obtained in yield. The IR analysis estimated 1,2- and 3,4-/trans/cis=7/0/93. Moreover, Tg was -62 degreeC. The viscosity of the specific modified IR2 was 6,900 Pa·s.

[Preparation of rubber composition]
The components shown in Table 1 below were mixed in the proportions (parts by mass) shown in the same table.
Specifically, first, of the components shown in Table 1 below, components other than sulfur and a vulcanization accelerator were mixed with a Banbury mixer at 80° C. for 5 minutes. Next, using a roll, sulfur and a vulcanization accelerator were mixed with the above mixture to obtain a rubber composition.

[Evaluation]
The obtained rubber compositions were evaluated as follows.

<Dispersibility>
Each rubber composition (unvulcanized) thus obtained was press-vulcanized in a mold (15 cm×15 cm×0.2 cm) at 148° C. for 30 minutes to prepare a vulcanized rubber sheet.
Then, with respect to the produced vulcanized rubber sheet, a strain-shear stress measuring machine (RPA2000, manufactured by α-Technology Co., Ltd.) was used to obtain a strain-shear elastic modulus G′ of strain 0.28% and a strain-shear elastic modulus G of strain 30.0%. 'And the difference G'0.28 (MPa)-G'30.0 (MPa) were calculated as the Payne effect.
The results are shown in Table 1. The smaller the difference value, the better the dispersibility of the reinforcing filler. The results are expressed as an index with Comparative Example 1 being 100. When the index is less than 100, the dispersibility is excellent.

<Low heat generation>
With respect to the vulcanized rubber sheet produced as described above, a loss tangent tan δ at a temperature of 60° C. under conditions of initial strain of 10%, amplitude of ±2% and frequency of 20 Hz using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.). (60° C.) was measured.
The results are shown in Table 1. The smaller the value of tan δ (60° C.), the better the low heat buildup. The results are shown as an index with Comparative Example 1 being 100. When the index is less than 100, low heat build-up is excellent.

<Abrasion resistance>
Regarding the vulcanized rubber sheet produced as described above, the amount of wear was measured under the conditions of a temperature of 20° C. and a slip ratio of 50% using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho) in accordance with JIS K6264-1, 2:2005. It was measured. Then, the wear resistance index was calculated from the following formula.
Abrasion resistance index=(abrasion amount of Comparative Example 1/abrasion amount of each vulcanized rubber sheet)×100
The results are shown in Table 1. The larger the index, the smaller the amount of wear and the better the wear resistance.
In the present invention, when the index exceeds 100, the abrasion resistance is excellent.

Details of each component shown in Table 1 above are as follows.
・Natural rubber: TSR20
Comparative unmodified IR1: Comparative unmodified IR1 synthesized as described above (Mw=800,000, Mw/Mn=1.21, Tg=−60° C. Comparative unmodified IR1 does not have a predetermined functional group. )

-Carbon black: Tokai Carbon Seast KH
Silica: Zeosil Premium 200MP (silica, N ₂ SA=200 m ² /g, CTAB=200 m ² /g, N ₂ SA/CTAB=1.0, manufactured by Rhodia)
・Silane coupling agent: Si69 manufactured by Evonik Degussa

Specific modified IR1: Specific modified IR1 synthesized as described above (modified IR having a functional group represented by the above formula (m1) at the end, Mw=292,000, Mw/Mn=1.20, 1,2- And 3,4-/trans/cis=8/0/92, Tg=-61° C., viscosity=8,100 Pa·s)
Specific modified IR2: Specific modified IR2 synthesized as described above (modified IR having a functional group represented by the above formula (m1) at the end, Mw=150,000, Mw/Mn=1.18, 1,2- And 3,4-/trans/cis=7/0/93, Tg=-62° C., viscosity=6,900 Pa·s)

-Stearic acid: stearic acid YR (manufactured by NOF CORPORATION)
・Processing aid: Actiplast ST (manufactured by Rhein Chemie)
-Anti-aging agent: SANTOFLEX 6PPD (manufactured by Soltia Europe)
・Oil: Extract No. 4S (manufactured by Showa Shell Sekiyu KK)
・Zinc flower: Zinc flower No. 3 (manufactured by Shodo Chemical Co., Ltd.)
・Sulfur: Oil-treated sulfur (made by Karuizawa Smelter & Refinery)
・Vulcanization accelerator CZ: NOXCELLER CZ-G (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
・Vulcanization accelerator DPG: Succinol DG: (manufactured by Sumitomo Chemical Co., Ltd.)

  In addition, in Table 1, "Tg of a rubber component" represents the above-mentioned "Tg of a rubber component."

As can be seen from Table 1, Examples 1 to 6 containing the specific modified IR exhibited excellent dispersibility, low heat build-up and abrasion resistance as compared with Comparative Example 1 containing no specific modified IR.
On the other hand, Comparative Examples 2 to 4 in which the isoprene polymer having no specific functional group at the end was blended had insufficient dispersibility, low heat buildup or abrasion resistance.

From the comparison of Examples 1 to 3, the larger the content of the specific modified IR with respect to the content of the rubber component, the better the low heat buildup.
From the comparison of Examples 1 to 3, the smaller the content of the specific modified IR relative to the content of the rubber component, the better the abrasion resistance.

Claims (9)

A rubber component containing a modified isoprene polymer, and a reinforcing filler,
The reinforcing filler contains carbon black and/or silica,
The modified isoprene polymer has a terminal functional group containing a nitrogen atom and a silicon atom,
The weight average molecular weight of the modified isoprene polymer is 100,000 or more and 10,000,000 or less,
The content of the modified isoprene polymer, the rubber component 100 parts by weight, Ri 1 to 40 parts by mass der,
In the modified isoprene polymer, the functional groups, Ru Oh a group represented by the following formula (M), the rubber composition.
In the formula (M), R ₁ and R ₂ each independently represent a hydrogen atom or a substituent,
L represents a divalent organic group,
n represents an integer of 0 to 2,
m represents an integer of 1 to 3,
n and m satisfy the relational expression of n+m=3,
* Represents a binding position.   The rubber composition according to claim 1, wherein the content of the reinforcing filler is 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. The nitrogen adsorption specific surface area (N ₂ SA) of the silica is 140 m ² /g or more,
The silica has a CTAB adsorption specific surface area (CTAB) of 150 m ² /g or more,
The rubber composition according to claim 1 or 2, wherein a ratio of the nitrogen adsorption specific surface area to the CTAB adsorption specific surface area is 0.8 to 1.4. Including the silica, further contains a silane coupling agent,
The rubber composition according to claim 1, wherein the content of the silane coupling agent is 1 to 20 mass% with respect to the content of the silica.   The rubber composition according to any one of claims 1 to 4, wherein the modified isoprene polymer has a molecular weight distribution of 2.0 or less.   The rubber composition according to claim 1, wherein the rubber component further contains natural rubber. In the formula (M), R ₁ is a hydrogen atom, an alkyl group, an alkylsilyl group or an aromatic hydrocarbon group, a plurality of R ₁ may be the same or different and claims 1-6 The rubber composition according to any one of 1 . The rubber composition according to any one of claims 1 to 7 , wherein a plurality of R _{1 s} in the formula (M) are the same and are hydrogen atoms. Glass transition temperature of the modified isoprene polymer is -50 ° C. or less, the rubber composition according to any one of claims 1-8.