JP7370734B2 - Manufacturing method of polybutadiene rubber - Google Patents

Description

The present invention relates to a method for producing polybutadiene rubber, and more specifically to a polybutadiene rubber that can effectively reduce tackiness at high temperatures and provide a crosslinked rubber product with low heat build-up and excellent wet grip properties. Relating to a method for manufacturing. The present invention also relates to a polybutadiene rubber obtained by this production method, a rubber composition containing the polybutadiene rubber, and a crosslinked rubber product thereof.

In recent years, there has been a strong demand for automobile tires to have low fuel consumption due to environmental and resource issues. A crosslinked rubber composition containing silica as a filler has a lower heat build-up than a crosslinked rubber composition containing carbon black, and therefore has lower rolling resistance when used in a tire. Therefore, by constructing a tire using a crosslinked rubber composition containing silica, a tire with excellent fuel efficiency can be obtained.

However, on the other hand, even if silica is blended with conventional rubber, the affinity between rubber and silica is insufficient, so the silica tends to aggregate with each other. The processability of the composition is poor, and the crosslinked rubber product obtained by crosslinking the composition has insufficient low heat generation properties.

Therefore, in order to improve the affinity between rubber and silica, it has been proposed to add various silane coupling agents to rubber compositions, such as those disclosed in Patent Document 1 and Patent Document 2. . However, handling the silane coupling agent requires advanced processing technology, and since the silane coupling agent is expensive, there is a problem in that when the amount of the silane coupling agent is increased, the manufacturing cost of the tire increases.

In order to solve such problems, for example, as disclosed in Patent Document 3 and Patent Document 4, when obtaining a rubber polymer by a solution polymerization method, a modifier is reacted with the active end of the polymer chain. Techniques are being considered to make rubber itself compatible with silica. However, due to the increasing demand for low fuel consumption and wet grip properties for automobile tires in recent years, further improvements in low heat generation properties and wet grip properties are desired. In addition, the rubber polymers obtained by the techniques of Patent Documents 3 and 4 have high tackiness at high temperatures, so during production, the rubber polymers are removed from the polymer solution through steam stripping, etc. After recovering the polymer, when drying the remaining water in the rubber polymer, the stickiness of the rubber polymer becomes high under high temperatures, resulting in it sticking to the walls and floors of the equipment or clogging. There was also a problem that drying became unstable due to the occurrence of drying.

Japanese Patent Application Publication No. 2011-46640 Japanese Patent Application Publication No. 2012-17291 Japanese Patent Application Publication No. 2013-139504 International Publication No. 2018/092716

The present invention has been made in view of the above circumstances, and can provide a rubber crosslinked product that effectively reduces tackiness under high temperatures and has excellent low heat build-up and wet grip properties. , aims to provide a method for producing polybutadiene rubber.

As a result of intensive research in order to achieve the above object, the present inventors reacted a specific polyorganosiloxane as a modifier to a polybutadiene polymer chain having an active end having a specific molecular chain length, and thereby By making the resulting polybutadiene rubber have a molecular weight within a specific range, tackiness at high temperatures can be effectively reduced, and the rubber crosslinked product obtained using this can also have a low heat generation property. The present inventors have discovered that it has excellent wet grip properties, and have completed the present invention.

（一般式（１）中、Ｒ^１～Ｒ^８は、炭素数１～６のアルキル基、または炭素数６～１２のアリール基であり、これらは互いに同一であっても相違していてもよい。Ｘ^１およびＸ^４は、炭素数１～６のアルキル基、炭素数６～１２のアリール基、炭素数１～５のアルコキシ基、および、エポキシ基を含有する炭素数４～１２の基からなる群より選ばれるいずれかの基であり、これらは互いに同一であっても相違していてもよい。Ｘ^２は、炭素数１～５のアルコキシ基、またはエポキシ基を含有する炭素数４～１２の基 であり、複数あるＸ^２は、互いに同一であっても相違していてもよい。Ｘ^３は、２～２０のアルキレングリコールの繰返し単位を含有する基であり、Ｘ^３が複数あるときは、それらは互いに同一であっても相違していてもよい。ｍは３～２００の整数、ｎは０～２００の整数、ｋは０～２００の整数であり、ｍ＋ｎ＋ｋは３以上である。) That is, according to the present invention, a first step of polymerizing a monomer containing 1,3-butadiene using a polymerization initiator in an inert solvent to obtain a polybutadiene chain having an active end;
A method for producing polybutadiene rubber, comprising a second step of reacting the polybutadiene chain having an active end with a polyorganosiloxane represented by the following general formula (1),
The peak top molecular weight (Mp1) detected by gel permeation chromatography of the polybutadiene chain having an active end is 250,000 to 350,000,
The polybutadiene rubber has a peak top molecular weight (Mp2) in a range of 1.5 times or more and less than 2.5 times the peak top molecular weight (Mp1) when the molecular weight is measured by gel permeation chromatography. The ratio of the area ratio (X) of the peak portion to the total elution area and the area ratio (Y) to the total elution area of the peak portion having a peak top molecular weight (Mp3) in a range of 2.5 times or more is X:Y =75:25 to 55:45 is provided.

(In general formula (1), R ¹ to R ⁸ are an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and these may be the same or different. .X ¹ and X ⁴ are an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a group having 4 to 12 carbon atoms containing an epoxy group. ^These groups may be the same or different from each other. 12 groups, and a plurality of X ² may be the same or different. X ³ is a group containing 2 to 20 alkylene glycol repeating units, and there is ^a plurality of m is an integer from 3 to 200, n is an integer from 0 to 200, k is an integer from 0 to 200, and m+n+k is 3 or more. .)

（一般式（２）中、Ｒ^９は、ヒドロカルビル基であり、Ａ^１は、活性末端を有するポリブタジエン鎖とポリオルガノシロキサンとの反応により生成した反応残基と反応しうる基であり、Ａ^２は、窒素原子を含有する基であり、ｐは０～２の整数、ｑは１～３の整数、ｒは１～３の整数、ｐ＋ｑ＋ｒ＝４である。）
本発明の製造方法において、前記一般式（２）のＡ^１が、－ＯＲ^１０（Ｒ^１０は水素原子またはヒドロカルビル基）で表される基であることが好ましい。
本発明の製造方法において、前記第１工程が、不活性溶媒中で、イソプレン、またはイソプレンおよび芳香族ビニル化合物を含む単量体を、重合開始剤により重合し、イソプレン単量体単位８０～１００重量％、および芳香族ビニル単量体単位０～２０重量％を含む活性末端を有する重合体ブロック（Ａ）を形成させる工程と、前記活性末端を有する重合体ブロック（Ａ）と、１，３－ブタジエンを含む単量体と、を混合して重合反応を継続させ、１，３－ブタジエン単量体単位を９５重量％以上含む活性末端を有する重合体ブロック（Ｂ）を、重合体ブロック（Ａ）と一続きにして形成させることにより、活性末端を有するポリブタジエン鎖を得る工程とを備えるものであることが好ましい。 In the production method of the present invention, the polybutadiene rubber preferably has a Mooney viscosity (ML1+4, 100°C) of 60 to 90.
Preferably, the production method of the present invention further includes a third step of reacting a compound represented by the following general formula (2) with the polybutadiene chain reacted with the polyorganosiloxane obtained in the second step.

(In general formula (2), R ⁹ is a hydrocarbyl group, A ¹ is a group capable of reacting with a reactive residue produced by the reaction of a polybutadiene chain having an active end with a polyorganosiloxane, and A ² is a group containing a nitrogen atom, p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, p+q+r=4.)
In the production method of the present invention, A ¹ in the general formula (2) is preferably a group represented by -OR ¹⁰ (R ¹⁰ is a hydrogen atom or a hydrocarbyl group).
In the production method of the present invention, in the first step, isoprene or a monomer containing isoprene and an aromatic vinyl compound is polymerized using a polymerization initiator in an inert solvent to obtain 80 to 100 isoprene monomer units. % by weight, and a step of forming a polymer block (A) having an active end containing 0 to 20 wt % of aromatic vinyl monomer units; the polymer block (A) having an active end; - A monomer containing butadiene is mixed to continue the polymerization reaction, and a polymer block (B) having an active end containing 95% by weight or more of 1,3-butadiene monomer units is converted into a polymer block ( It is preferable that the method comprises a step of forming a polybutadiene chain having an active end by forming the polybutadiene chain continuously with A).

Further, according to the present invention, there is provided a polybutadiene rubber obtained by the above manufacturing method.
Further, according to the present invention, there is provided a rubber composition containing 10 to 120 parts by weight of silica to 100 parts by weight of the rubber component containing the above-mentioned polybutadiene rubber in a proportion of 15 to 50% by weight. .
The rubber composition of the present invention preferably further contains a crosslinking agent.

Further, according to the present invention, there are provided a crosslinked rubber product obtained by crosslinking the above rubber composition, and a tire comprising the crosslinked rubber product.

According to the present invention, a polybutadiene rubber that can effectively reduce tackiness at high temperatures and provide a crosslinked rubber product with low heat build-up and excellent wet grip properties, a rubber composition containing the polybutadiene rubber, It is possible to provide a crosslinked rubber product obtained by crosslinking the rubber composition and exhibiting low heat build-up and excellent wet grip properties, and a tire comprising the crosslinked rubber product.

FIG. 1 is a diagram showing an example of a chart obtained when gel permeation chromatography measurement is performed on polybutadiene rubber obtained by the manufacturing method of the present invention.

<Production method of polybutadiene rubber>
The method for producing polybutadiene rubber of the present invention includes a first step of polymerizing a monomer containing 1,3-butadiene using a polymerization initiator in an inert solvent to obtain a polybutadiene chain having an active end;
a second step of reacting the polybutadiene chain having the active end with a polyorganosiloxane described below;
The peak top molecular weight (Mp1) detected by gel permeation chromatography of the polybutadiene chain having an active end is 250,000 to 350,000,
The polybutadiene rubber has a peak top molecular weight (Mp2) in a range of 1.5 times or more and less than 2.5 times the peak top molecular weight (Mp1) when the molecular weight is measured by gel permeation chromatography. The ratio of the area ratio (X) of the peak portion to the total elution area and the area ratio (Y) to the total elution area of the peak portion having a peak top molecular weight (Mp3) in a range of 2.5 times or more is X:Y =75:25 to 55:45.

<First step>
The first step of the production method of the present invention is a step of polymerizing a monomer containing 1,3-butadiene using a polymerization initiator in an inert solvent to obtain a polybutadiene chain having an active end.

In the first step of the production method of the present invention, a monomer mainly containing 1,3-butadiene is used as a monomer to obtain a polybutadiene chain having an active end, and usually substantially 1,3-butadiene is used. A compound consisting only of 3-butadiene is used. That is, the proportion of 1,3-butadiene in the monomer used to obtain a polybutadiene chain having an active end is usually 100% by weight. On the other hand, monomers other than 1,3-butadiene may be used as long as they do not impede the effects of the present invention. The proportion of monomers other than 1,3-butadiene in the monomer is preferably 5% by weight or less, more preferably 1% by weight or less. That is, the content of 1,3-butadiene in the monomer used to obtain a polybutadiene chain having an active end is preferably 95% by weight or more, more preferably 99% by weight or more.

Monomers other than 1,3-butadiene may be any compound copolymerizable with 1,3-butadiene, and are not particularly limited, but include isoprene, 2,3-dimethyl-1,3-butadiene, 2- Phenyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3- Conjugated diene compounds such as octadiene; styrene, methylstyrene, ethylstyrene, t-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorstyrene, bromostyrene, methoxystyrene, dimethylaminomethylstyrene, dimethylamino Aromatic vinyl compounds such as ethylstyrene, diethylaminomethylstyrene, diethylaminoethylstyrene, cyanoethylstyrene, and vinylnaphthalene; Chain olefin compounds such as ethylene, propylene, and 1-butene; Cyclic olefin compounds such as cyclopentene and 2-norbornene; 1. Non-conjugated diene compounds such as 5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, 5-ethylidene-2-norbornene; methyl (meth)acrylate, ethyl (meth)acrylate, ) (meth)acrylic acid esters such as butyl acrylate; other (meth)acrylic acid derivatives such as (meth)acrylonitrile and (meth)acrylamide; and the like.

The inert solvent used in the polymerization is not particularly limited as long as it is commonly used in solution polymerization and does not inhibit the polymerization reaction. Specific examples of inert solvents include chain aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; can be mentioned. These inert solvents may be used alone or in combination of two or more. The amount of the inert solvent used is not particularly limited, but it is an amount such that the concentration of the monomer containing 1,3-butadiene is, for example, 1 to 50% by weight, preferably 10 to 40% by weight. be.

The polymerization initiator used in the polymerization is not particularly limited as long as it can polymerize a monomer containing 1,3-butadiene to provide a polybutadiene chain having an active end. Specific examples thereof include polymerization initiators whose main catalysts are organic alkali metal compounds, organic alkaline earth metal compounds, and lanthanum series metal compounds. Examples of organic alkali metal compounds include organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbene lithium; dilithiomethane, 1,4-dilithiobutane, 1,4 -Organic polyvalent lithium compounds such as dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-tris(lithiomethyl)benzene;Organic sodium compounds such as sodium naphthalene;Organic compounds such as potassium naphthalene Potassium compounds; and the like. Examples of organic alkaline earth metal compounds include di-n-butylmagnesium, di-n-hexylmagnesium, diethoxycalcium, di-t-butoxystrontium, diethoxybarium, diisopropoxybarium, and diethylmercaptobarium. , di-t-butoxybarium, diphenoxybarium, diethylaminobarium, diketylbarium and the like. Polymerization initiators using lanthanum series metal compounds as main catalysts include, for example, lanthanum series metals consisting of lanthanum series metals such as lanthanum, cerium, praseodymium, neodymium, samarium, and gadolinium, carboxylic acids, and phosphorus-containing organic acids. Examples include polymerization initiators comprising a salt of 1 as a main catalyst and a co-catalyst such as an alkyl aluminum compound, an organoaluminum hydride compound, or an organoaluminum halide compound. Among these polymerization initiators, organic monolithium compounds and organic polyvalent lithium compounds are preferably used, organic monolithium compounds are more preferably used, and n-butyllithium is particularly preferably used. Note that the organic alkali metal compound is used as an organic alkali metal amide compound by reacting it with a secondary amine compound such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, piperidine, hexamethyleneimine, and heptamethyleneimine in advance. You may. These polymerization initiators may be used alone or in combination of two or more.

Examples of the organic alkali metal amide compound include those obtained by reacting an organic alkali metal compound with a secondary amine compound. Among them, in the production method of the present invention, the compound represented by the following general formula (3) is used. Compounds can be suitably used.

The alkyl group is not particularly limited, but an alkyl group having 1 to 20 carbon atoms is preferable, and an alkyl group having 1 to 10 carbon atoms is more preferable. Examples of such alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, and n-hexyl group. group, n-heptyl group, n-octyl group, n-decyl group, etc.

The cycloalkyl group is not particularly limited, but a cycloalkyl group having 3 to 20 carbon atoms is preferred, and a cycloalkyl group having 3 to 12 carbon atoms is more preferred. Examples of such a cycloalkyl group include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a cyclododecyl group.

The aryl group is not particularly limited, but an aryl group having 6 to 12 carbon atoms is preferable, and an aryl group having 6 to 10 carbon atoms is more preferable. Examples of such aryl groups include phenyl, 1-naphthyl, and 2-naphthyl groups.

The aralkyl group is not particularly limited, but an aralkyl group having 7 to 13 carbon atoms is preferable, and an aralkyl group having 7 to 9 carbon atoms is more preferable. Examples of such aralkyl groups include benzyl groups and phenethyl groups.

The protecting group for the amino group is not particularly limited and may be any group that acts as a protecting group for the amino group, such as an alkylsilyl group. Examples of such alkylsilyl groups include trimethylsilyl, triethylsilyl, triphenylsilyl, methyldiphenylsilyl, ethylmethylphenylsilyl, and tert-butyldimethylsilyl.
In addition, when R ¹¹ and/or R ¹² is a protecting group for an amino group, by removing the protecting group for the amino group, at one end of the polymer chain forming the obtained polybutadiene rubber, the following A structure in which R ¹³ and/or R ¹⁴ in general formula (5) is a hydrogen atom can be introduced.

The group that can be hydrolyzed to produce a hydroxyl group is not particularly limited, and may be any group that can produce a hydroxyl group when hydrolyzed in the presence of an acid, such as an alkoxyalkyl group, an epoxy group, etc. Examples include groups containing .
Examples of the alkoxyalkyl group include a methoxymethyl group, an ethoxymethyl group, an ethoxyethyl group, a propoxymethyl group, a butoxymethyl group, a butoxyethyl group, a propoxyethyl group, and the like.
Examples of the group containing an epoxy group include a group represented by the following general formula (4).
-Z ¹ -Z ² -E ¹ (4)
In the general formula (4), Z ¹ is an alkylene group or 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 glycidyl group.

Furthermore, R ¹¹ and R ¹² may be bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, and in this case, R ¹¹ and R ¹² and the nitrogen atom to which they are bonded form a ring structure. Specific examples of structures include azetidine ring (R ¹¹ and R ¹² are propylene groups), pyrrolidine ring (R ¹¹ and R ¹² are butylene groups), piperidine ring (R ¹¹ and R ¹² are pentylene groups) , hexamethyleneimine ring (R ¹¹ and R ¹² are hexylene groups), and the like.
When R ¹¹ and R ¹² are bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, the ring structure is preferably a 4- to 8-membered ring structure.

In addition, in general formula (3), ^M1 is an alkali metal atom, and such alkali metal atoms include lithium atom, sodium atom, potassium atom, etc. Among these, from the viewpoint of polymerization activity, , lithium atoms are preferred.

In the first step of the production method of the present invention, when a compound represented by general formula (3) is used as a polymerization initiator, the amine structure forming the organic alkali metal amide compound is at the polymerization initiation terminal of the polymer chain. It will remain connected to the Therefore, when a compound represented by the general formula (3) is used as a polymerization initiator, a structure represented by the following general formula (5) is introduced at one end of the polymer chain forming the resulting polybutadiene rubber. be done.

In general formula (5), R ¹³ and R ¹⁴ are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, a protecting group for an amino group, or can be hydrolyzed to produce a hydroxyl group. R ¹³ and R ¹⁴ may be bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, and when forming the ring structure, in addition to the nitrogen atom to which they are bonded, , these may form a ring structure together with a heteroatom other than the nitrogen atom to which they are bonded.

Examples of alkyl groups, cycloalkyl groups, aryl groups, aralkyl groups, protecting groups for amino groups that can become R ¹³ and R ¹⁴ , and groups that can be hydrolyzed to produce hydroxyl groups include R ¹¹ and R ¹² in general formula (3). In addition, when R ¹³ and R ¹⁴ are bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, R ¹¹ , R 12 and R ¹² in general formula (3) can be mentioned. can be the same.
Note that the hydrogen atoms that can become R ¹³ and R ¹⁴ are introduced by removing the protecting group of the amino group.

In the production method of the present invention, when an organic alkali metal amide compound is used as a polymerization initiator, the resulting polybutadiene rubber has an amine structure at one end and a specific polymer derived from a modifier at the other end. It can have the following structure. As a result, due to the effects of such an amine structure, the resulting crosslinked rubber product using polybutadiene rubber has lower heat build-up and excellent wet grip properties.

The method of adding the organic alkali metal amide compound as a polymerization initiator to the polymerization system is not particularly limited, and may be carried out by reacting the organic alkali metal compound with a secondary amine compound in advance to obtain the organic alkali metal amide compound. A method can be employed in which this is mixed with a monomer containing 1,3-butadiene to allow the polymerization reaction to proceed. Alternatively, the organic alkali metal amide compound and the secondary amine compound can be separately added to the polymerization system, and mixed with a monomer containing 1,3-butadiene, thereby adding the organic alkali metal amide compound to the polymerization system. You may adopt the method of advancing a polymerization reaction by making it produce|generate. Reaction conditions such as reaction temperature are not particularly limited, and may be in accordance with the intended polymerization reaction conditions, for example.

The amount of the secondary amine compound to be used may be determined depending on the amount of the desired polymerization initiator added, but it is usually 0.01 to 1.5 mmol, preferably 0.1 mmol per 1 mmol of the organic alkali metal compound. ~1.2 mmol, more preferably 0.5-1.0 mmol.

The amount of the polymerization initiator used may be determined depending on the molecular weight of the target polybutadiene chain, but it is usually 1 to 50 mmol, preferably 1.5 to 20 mmol, more preferably 2 to 20 mmol, per 1000 g of monomer. It is in the range of 15 mmol.

The polymerization temperature is usually in the range of -80 to +150°C, preferably 0 to 100°C, more preferably 30 to 90°C. As the polymerization mode, any mode such as batch mode or continuous mode can be adopted.

In addition, when polymerizing a monomer containing 1,3-butadiene, a polar compound is added to an inert organic solvent in order to control the vinyl bond content in the 1,3-butadiene monomer unit in the resulting polybutadiene chain. may be added. Examples of the polar compound include ether compounds such as dibutyl ether, tetrahydrofuran, and 2,2-di(tetrahydrofuryl)propane; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; phosphine compounds; and the like. Among these, ether compounds and tertiary amines are preferred, tertiary amines are more preferred, and tetramethylethylenediamine is particularly preferred. These polar compounds may be used alone or in combination of two or more. The amount of the polar compound to be used may be determined depending on the desired vinyl bond content, and is preferably 100 mol or less, more preferably 10 mol or less, per 1 mol of the polymerization initiator. When the amount of the polar compound used is within this range, it is easy to control the vinyl bond content in the 1,3-butadiene monomer unit, and problems due to deactivation of the polymerization initiator are less likely to occur.

The vinyl bond content in the 1,3-butadiene monomer units in the polybutadiene chain having an active end obtained in the first step of the production method of the present invention is preferably 1 to 90% by weight, more preferably 3 to 90% by weight. 80% by weight, particularly preferably 5 to 70% by weight. By controlling the vinyl bond content in the 1,3-butadiene monomer unit to be within the above range, the resulting rubber crosslinked product can have an excellent low heat generation property.

The active terminal-containing polybutadiene chain obtained in the first step of the production method of the present invention preferably contains 95% by weight or more of 1,3-butadiene monomer units, more preferably 99% by weight of all monomer units. It is at least 100% by weight, more preferably 100% by weight.

In the production method of the present invention, the polybutadiene chain having an active end obtained in the first step has a peak top molecular weight (Mp1) detected by gel permeation chromatography in the range of 250,000 to 350,000. The peak top molecular weight (Mp1) is preferably in the range of 260,000 to 340,000, more preferably in the range of 280,000 to 320,000. Note that the peak top molecular weight (Mp1) can be measured as a value in terms of polystyrene. If the peak top molecular weight (Mp1) is too low, the effect of reducing tackiness at high temperatures will not be obtained, while if it is too high, the processability will be poor when a reinforcing agent such as silica is blended and kneaded. The peak top molecular weight (Mp1) of the polybutadiene chain having an active end can be adjusted by controlling the polymerization conditions (for example, the amount of polymerization initiator used).

The polybutadiene chain having an active end obtained in the first step of the production method of the present invention may have a peak top molecular weight (Mp1) within the above range, and the weight average molecular weight (Mw) is not particularly limited, but is preferably 200. ,000 to 400,000, more preferably 230,000 to 380,000, still more preferably 250,000 to 350,000. By controlling the weight average molecular weight (Mw) of the polybutadiene chain having an active end within the above range, the resulting rubber crosslinked product can have an excellent low heat build-up property.

Furthermore, the molecular weight distribution expressed by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw/Mn) of the polybutadiene chain having an active end obtained in the first step of the production method of the present invention is also Although not particularly limited, it is preferably 1.0 to 3.0, more preferably 1.0 to 2.5. When the molecular weight distribution (Mw/Mn) of the polybutadiene chain having an active end is within the above range, the production of polybutadiene rubber becomes easy. Note that the weight average molecular weight (Mw) and number average molecular weight (Mn) can be determined as values measured by gel permeation chromatography in terms of polystyrene.

Further, in the manufacturing method of the present invention, the first step may be the following step from the viewpoint of improving the affinity with reinforcing agents such as silica.
That is, in an inert solvent, isoprene or a monomer containing isoprene and an aromatic vinyl compound is polymerized using a polymerization initiator to obtain 80 to 100% by weight of isoprene monomer units and aromatic vinyl monomer units. forming a polymer block (A) having an active end containing 0 to 20% by weight;
The polymer block (A) having an active end and a monomer containing 1,3-butadiene are mixed to continue the polymerization reaction, and the polymer block (A) containing 1,3-butadiene monomer units is 95% by weight or more. The method may also include a step of forming a polymer block (B) having an active end in a continuous manner with the polymer block (A) to obtain a polybutadiene chain having an active end.

By employing such a step, the polybutadiene chain having an active end obtained in the first step can be converted to a polybutadiene chain containing 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units. It may include a polymer block (A) and a polymer block (B) containing 95% by weight of 1,3-butadiene monomer units formed in a continuous manner.
Such an aspect will be explained below.

[Polymer block (A)]
The polymer block (A) in the polybutadiene chain according to one aspect of the present invention contains 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units in the polymer block (A). However, it is preferable that it contains 85 to 95% by weight of isoprene monomer units and 5 to 15% by weight of aromatic vinyl monomer units, and 89 to 95% by weight of isoprene monomer units and More preferably, it contains 5 to 11% by weight of aromatic vinyl monomer units. If the content ratio of isoprene monomer units and aromatic vinyl monomer units is within the above range, when silica is blended with polybutadiene rubber, the affinity between polybutadiene rubber and silica will be good, and it will be possible to use this. The low heat generation property of the rubber crosslinked product obtained can be further improved.

As the aromatic vinyl compound used to constitute the aromatic vinyl monomer unit contained in the polymer block (A), the same aromatic vinyl compounds as mentioned above can be used, and among these, styrene is preferable. In addition, these aromatic vinyl compounds may be used individually by 1 type, and may be used in combination of 2 or more types.

The polymer block (A) preferably consists of only isoprene monomer units, or isoprene monomer units and aromatic vinyl monomer units, but if desired, it may contain isoprene monomer units or isoprene monomer units. In addition to the monomer unit and the aromatic vinyl monomer unit, it may contain other monomer units. Other compounds used to constitute other monomer units include 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-butadiene, - Conjugated diene compounds other than isoprene such as pentadiene and 1,3-hexadiene; α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carbons such as acrylic acid, methacrylic acid, and maleic anhydride Acids or acid anhydrides; unsaturated carboxylic acid esters such as methyl methacrylate, ethyl acrylate, and butyl acrylate; 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and - non-conjugated dienes such as ethylidene-2-norbornene; and the like. Among these, 1,3-butadiene is preferred. These other monomers can be used alone or in combination of two or more. The content of other monomer units in the polymer block (A) is preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 6% by weight or less. preferable.

In the present invention, the polymer block (A) in the polybutadiene chain is formed by polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound using a polymerization initiator in an inert solvent. The formed polymer block (A) has an active end.

As the inert solvent used in the polymerization of isoprene or a monomer containing isoprene and an aromatic vinyl compound to form the polymer block (A), the same inert solvent as mentioned above can be used. can. The amount of inert solvent used is such that the monomer concentration is preferably 1 to 80% by weight, more preferably 10 to 50% by weight.

As the polymerization initiator used to form the polymer block (A), isoprene or a monomer containing isoprene and an aromatic vinyl compound may be polymerized to give a polymer chain having an active end. There is no particular limitation as long as it is possible. As a specific example, the same polymerization initiator as mentioned above can be used.

The amount of the polymerization initiator to be used may be determined depending on the desired molecular weight, but is preferably 4 to 250 mmol, more preferably 6 mmol per 100 g of isoprene or a monomer containing isoprene and an aromatic vinyl compound. ~200 mmol, particularly preferably from 10 to 70 mmol.

The polymerization temperature when polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound is preferably in the range of -80 to +150°C, more preferably 0 to 100°C, and still more preferably 20 to 90°C. be. As for the polymerization mode, any mode such as batch mode or continuous mode can be adopted. Furthermore, various bonding styles can be used, such as block, tapered, and random.

Furthermore, in the production method according to one embodiment of the present invention, a polar compound is added to the inert solvent during polymerization in order to adjust the vinyl bond content in the isoprene monomer units in the polymer block (A). It is preferable. As the polar compound, the same polar compounds as mentioned above can be used. The amount of the polar compound to be used may be determined depending on the desired vinyl bond content, and is preferably 0.01 to 30 mol, more preferably 0.05 to 10 mol, per 1 mol of the polymerization initiator. When the amount of the polar compound used is within the above range, it is easy to control the vinyl bond content in the isoprene monomer unit, and problems due to deactivation of the polymerization initiator are less likely to occur. Furthermore, by increasing the amount of the polar compound used within the above range, the vinyl bond content in the isoprene monomer unit can be increased.

The vinyl bond content in the isoprene monomer units in the polymer block (A) is preferably 5 to 90% by weight, more preferably 5 to 80% by weight. By controlling the vinyl bond content in the isoprene monomer unit to be within the above range, the low heat build-up property of the resulting rubber crosslinked product can be further improved. In addition, in this specification, the vinyl bond content in the isoprene monomer unit refers to the isoprene monomer unit having a 1,2-structure and the isoprene monomer unit having a 3,4-structure in the isoprene monomer unit. It refers to the percentage of the total amount of isoprene monomer units.

The weight average molecular weight (Mw) of the polymer block (A) is preferably 500 to 15,000, and preferably 1,000 to 12,000 as a polystyrene equivalent value measured by gel permeation chromatography. is more preferable, and particularly preferably from 1,500 to 10,000. When the weight average molecular weight of the polymer block (A) is within the above range, the low heat generation property of the resulting rubber crosslinked product can be further improved.

Further, the molecular weight distribution expressed by the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polymer block (A) is preferably 1.0 to 1.5, More preferably, it is 1.0 to 1.3. When the molecular weight distribution value (Mw/Mn) of the polymer block (A) is within the above range, production of polybutadiene rubber becomes easier. Note that the weight average molecular weight (Mw) and number average molecular weight (Mn) can be determined as values measured by gel permeation chromatography in terms of polystyrene.

[Polymer block (B)]
The polymer block (B) in the polybutadiene chain according to one aspect of the present invention may contain 95% by weight or more of 1,3-butadiene monomer units in the polymer block (B). ,3-butadiene monomer units in an amount of 99% by weight or more, and more preferably 1,3-butadiene monomer units in an amount of 100% by weight.

The polymer block (B) preferably consists of only 1,3-butadiene monomer units, but if desired, 1,3-butadiene monomer units may be added as long as the essential properties of the present invention are not impaired. In addition to the mer unit, it may contain other monomer units. As other monomers used to constitute other monomer units, the same compounds as those exemplified in the above-mentioned polymer block (A) (excluding 1,3-butadiene) are used. be able to. Moreover, in the polymer block (B), isoprene can also be used as another monomer. The content of other monomer units in the polymer block (B) is preferably 5% by weight or less, more preferably 1% by weight or less.

In one embodiment of the present invention, the polymer block (B) in the polybutadiene chain is polymerized by mixing the above-described polymer block (A) having an active end and a monomer containing 1,3-butadiene. By continuing the reaction, it is formed continuously with the polymer block (A). The formed polymer block (B) has an active end. On the other hand, the active end disappears from the polymer block (A).

In order to form the polymer block (B), the inert solvent used in the polymerization of the polymer block (A) and the monomer containing 1,3-butadiene is not particularly limited, and the above-mentioned inert solvents may be used. The same active solvent can be used.

The amount of the polymer block (A) having an active end to be used in forming the polymer block (B) may be determined depending on the desired molecular weight, but monomers containing 1,3-butadiene The amount 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.

The method of mixing the polymer block (A) and the monomer containing 1,3-butadiene is not particularly limited. A) may be added, or a monomer containing 1,3-butadiene may be added to the solution of the polymer block (A) having an active end. From the viewpoint of polymerization control, a method of adding a polymer block (A) having an active end to a monomer solution containing 1,3-butadiene is preferred.

The polymerization temperature when polymerizing a monomer containing 1,3-butadiene is preferably in the range of -80 to +150°C, more preferably 0 to 100°C, and even more preferably 20 to 90°C. As for the polymerization mode, any mode such as batch mode or continuous mode can be adopted.

Further, in one embodiment of the present invention, in order to adjust the vinyl bond content in the 1,3-butadiene monomer unit in the polymer block (B), isoprene monomer units in the polymer block (A) are used. It is preferable to add a polar compound to the inert solvent during polymerization, as well as when adjusting the vinyl bond content in the polymer. However, when preparing the polymer block (A), an amount of polar compound sufficient to adjust the vinyl bond content in the 1,3-butadiene monomer units in the polymer block (B) is added to the inert solvent. is added, there is no need to add a new polar compound. As the polar compound used to adjust the vinyl bond content, the same polar compounds as mentioned above can be used. The amount of the polar compound to be used may be determined depending on the desired vinyl bond content, and the amount of the polar compound used in the initial polymerization reaction (polymerization reaction to form the first polymer block (A)) The amount may be adjusted preferably within the range of 0.01 to 100 mol, more preferably 0.1 to 30 mol, per mol of the agent. When the amount of the polar compound used is within this range, it is easy to control the vinyl bond content in the 1,3-butadiene monomer unit, and problems due to deactivation of the polymerization initiator are less likely to occur.

The vinyl bond content in the 1,3-butadiene monomer units in the polymer block (B) is preferably 1 to 90% by weight, more preferably 3 to 80% by weight, particularly preferably 5 to 70% by weight. be. By controlling the vinyl bond content in the 1,3-butadiene monomer units in the polymer block (B) to be within the above range, the resulting rubber crosslinked product can have excellent low heat generation properties.

In this way, a polybutadiene chain with active ends can be obtained, which has a polymer block (A) and a polymer block (B). In one embodiment of the present invention, from the viewpoint of productivity, the polybutadiene chain having an active end is composed of a polymer block (A) and a polymer block (B), and the terminal of the polymer block (B) is Although it is preferable to have an active end, it may have a plurality of polymer blocks (A) or may have other polymer blocks. Examples include polybutadiene chains with active ends, such as polymer block (A)-polymer block (B)-polymer block (A). In this case, an active end will be formed at the end of the polymer block (A) formed following the polymer block (B). When forming a polymer block (A) on the active terminal side of a polybutadiene chain, the amount of isoprene used is the same as that used in the initial polymerization reaction (polymerization reaction to form the first polymer block (A)). The amount is preferably 10 to 100 mol, more preferably 15 to 70 mol, and particularly preferably 20 to 35 mol per mol of polymerization initiator.

Weight ratio of polymer block (A) and polymer block (B) in a polybutadiene chain having an active end obtained in one embodiment of the present invention (a plurality of polymer blocks (A) and polymer blocks (B) exist) If so, the weight ratio (based on the total weight of each) shall be (weight of polymer block (A))/(weight of polymer block (B)) from 0.001 to 0.1. is preferable, more preferably 0.003 to 0.07, particularly preferably 0.005 to 0.05. By setting the weight ratio of the polymer block (A) and the polymer block (B) within the above range, the resulting rubber crosslinked product has a good balance between wet grip properties and low heat build-up. I can do it.

The vinyl bond content in the isoprene monomer units and in the 1,3-butadiene monomer units in the active-terminated polybutadiene chain having polymer block (A) and polymer block (B) is as described above. The vinyl bond content in the 1,3-butadiene monomer unit in the polymer block (B) is preferably within the same range.

一般式（１）中、Ｒ^１～Ｒ^８は、炭素数１～６のアルキル基、または炭素数６～１２のアリール基であり、これらは互いに同一であっても相違していてもよい。Ｘ^１およびＸ^４は、炭素数１～６のアルキル基、炭素数６～１２のアリール基、炭素数１～５のアルコキシ基、および、エポキシ基を含有する炭素数４～１２の基からなる群より選ばれるいずれかの基であり、これらは互いに同一であっても相違していてもよい。Ｘ^２は、炭素数１～５のアルコキシ基、またはエポキシ基を含有する炭素数４～１２の基 であり、複数あるＸ^２は、互いに同一であっても相違していてもよい。Ｘ^３は、２～２０のアルキレングリコールの繰返し単位を含有する基であり、Ｘ^３が複数あるときは、それらは互いに同一であっても相違していてもよい。ｍは３～２００の整数、ｎは０～２００の整数、ｋは０～２００の整数であり、ｍ＋ｎ＋ｋは３以上である。 <Second process>
The second step of the production method of the present invention is a step of reacting the polybutadiene chain having an active end obtained in the first step with a polyorganosiloxane represented by the following general formula (1).

In the general formula (1), R ¹ to R ⁸ are an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and these may be the same or different. X ¹ and X ⁴ are composed of an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a group having 4 to 12 carbon atoms containing an epoxy group. It is any group selected from the group, and these may be the same or different from each other. X ² is an alkoxy group having 1 to 5 carbon atoms or a group having 4 to 12 carbon atoms containing an epoxy group, and multiple X ² groups may be the same or different. X ³ is a group containing 2 to 20 alkylene glycol repeating units, and when there is a plurality of X ³ s, they may be the same or different. m is an integer of 3 to 200, n is an integer of 0 to 200, k is an integer of 0 to 200, and m+n+k is 3 or more.

In the polyorganosiloxane represented by the general formula (1), the alkyl group having 1 to 6 carbon atoms that can constitute R ¹ to R ⁸ , X ¹ and X ⁴ in the general formula (1) includes, for example, methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, pentyl group, hexyl group, and cyclohexyl group. Examples of the aryl group having 6 to 12 carbon atoms include phenyl group and methylphenyl group. Among these, methyl groups and ethyl groups are preferred from the viewpoint of ease of manufacturing the polyorganosiloxane itself.

Further, in the polyorganosiloxane represented by the general formula (1), examples of the alkoxy group having 1 to 5 carbon atoms that can constitute X ¹ , X ² and X ⁴ include a methoxy group, an ethoxy group, a propoxy group, Examples include isopropoxy group and butoxy group. Among these, methoxy groups and ethoxy groups are preferred from the viewpoint of ease of manufacturing the polyorganosiloxane itself.

Further, in the polyorganosiloxane represented by the general formula (1), examples of the group having 4 to 12 carbon atoms containing an epoxy group that can constitute X ¹ , X ² and X ⁴ include the following general formula (6 ).
-Z ³ -Z ⁴ -E ² (6)
In the general formula (6), Z ³ is an alkylene group having 1 to 10 carbon atoms or an alkylarylene group, Z ⁴ is a methylene group, a sulfur atom, or an oxygen atom, and E ² is a carbon having an epoxy group. It is a number of 2 to 10 hydrocarbon groups.

The group represented by general formula (6) is preferably one in which Z ⁴ is an oxygen atom, more preferably one in which Z ⁴ is an oxygen atom and E ² is a glycidyl group, and Z ³ is a carbon Particularly preferred are alkylene groups of number 1 to 3, in which Z ⁴ is an oxygen atom and E ² is a glycidyl group.

In addition, in ^the polyorganosiloxane represented by the general formula (1), X ¹ and Groups are preferred. Furthermore, as X ² , among the above groups, a group having 4 to 12 carbon atoms and containing an epoxy group is preferable. Furthermore, it is more preferable that X ¹ and X ⁴ are alkyl groups having 1 to 6 carbon atoms, and X ² is a group containing epoxy group and having 4 to 12 carbon atoms.

一般式（７）中、ｔは２～２０の整数であり、Ｘ^５は炭素数２～１０のアルキレン基またはアルキルアリーレン基であり、Ｒ^１５は水素原子またはメチル基であり、Ｘ^６は炭素数１～１０のアルコキシ基またはアリールオキシ基である。これらの中でも、ｔが２～８の整数であり、Ｘ^５が炭素数３のアルキレン基であり、Ｒ^１５が水素原子であり、かつ、Ｘ^６がメトキシ基であるものが好ましい。 Furthermore, in the polyorganosiloxane represented by the general formula (1), as the group containing X ³ , ie, 2 to 20 alkylene glycol repeating units, a group represented by the following general formula (7) is preferable.

In the general formula (7), t is an integer of 2 to 20, X ⁵ is an alkylene group or alkylarylene group having 2 to 10 carbon atoms, R ¹⁵ is a hydrogen atom or a methyl group, and X ⁶ is a carbon It is an alkoxy group or an aryloxy group of number 1 to 10. Among these, those in which t is an integer of 2 to 8, X ⁵ is an alkylene group having 3 carbon atoms, R ¹⁵ is a hydrogen atom, and X ⁶ is a methoxy group are preferred.

In the polyorganosiloxane represented by the general formula (1), m is an integer of 3 to 200, preferably an integer of 20 to 150, more preferably an integer of 30 to 120. When m is 3 or more, the coupling rate of the obtained polybutadiene rubber becomes high, and as a result, it has excellent hot flow properties. Moreover, when m is 200 or less, the polyorganosiloxane itself represented by the general formula (1) can be manufactured more easily, and its viscosity does not become too high, making it easier to handle.

Further, in the polyorganosiloxane represented by the general formula (1), n is an integer of 0 to 200, preferably an integer of 0 to 150, more preferably an integer of 0 to 120. k is an integer of 0 to 200, preferably an integer of 0 to 150, more preferably an integer of 0 to 130. The total number of m, n and k is 3 or more, preferably from 3 to 400, more preferably from 20 to 300, particularly preferably from 30 to 250. When the total number of m, n, and k is 3 or more, the reaction between the polyorganosiloxane represented by the general formula (1) and the polybutadiene chain having an active end tends to proceed, and furthermore, the number of m, n, and k is 3 or more. When the total number is 400 or less, the polyorganosiloxane itself represented by the general formula (1) can be easily produced, and its viscosity will not become too high, making it easy to handle.

In the second step of the production method of the present invention, by reacting polyorganosiloxane as a modifier with the active end of the polybutadiene chain having an active end obtained in the first step, the polybutadiene chain is This method introduces a modified structure using siloxane. The polybutadiene chain after the reaction obtained in the second step of the production method of the present invention includes one in which a modified structure with siloxane is introduced at the end of the polymer chain, but in addition to this, polybutadiene chains include polyorganosiloxane. It may contain unmodified polybutadiene chains that have not been modified by.

The amount of polyorganosiloxane used in the second step of the production method of the present invention is the total amount of epoxy groups and alkoxy groups contained in the polyorganosiloxane with respect to 1 mole of the polymerization initiator used for polymerization in the first step. An amount in which the molar ratio is preferably 0.2 to 1.0 mol, more preferably 0.3 to 0.9 mol, and even more preferably 0.45 to 0.75 mol. be. By using the amount of polyorganosiloxane within this range, in addition to being able to introduce a modified structure with siloxane at the end of the obtained polybutadiene rubber, coupling reactions (dimerization reactions and trimerization reactions) starting from polyorganosiloxane can be carried out. quantification reaction or further quantification reaction) can proceed appropriately.

The method of reacting the polyorganosiloxane and the polybutadiene chain having an active end is not particularly limited, but examples include a method of mixing them in a solvent in which each of them can be dissolved. As the solvent used in this case, those exemplified as the inert solvent used in the first step mentioned above can be used. Moreover, in this case, a method of adding polyorganosiloxane to the polymerization solution used for polymerization to obtain a polybutadiene chain having an active end is simple and preferred. Further, in this case, the polyorganosiloxane is preferably dissolved in an inert solvent and added to the polymerization system, and the solution concentration is preferably in the range of 1 to 50% by weight. The reaction temperature is not particularly limited, but is usually 0 to 120°C, and the reaction time is also not particularly limited, but is usually 1 minute to 1 hour.

The timing of adding polyorganosiloxane to a solution containing polybutadiene chains with active ends is not particularly limited, but if the polymerization reaction has not been completed and the solution containing polybutadiene chains with active ends has no monomers. More specifically, the solution containing polybutadiene chains with active ends contains 100 ppm or more, more preferably 300 to 50,000 ppm of the monomer. It is desirable to add polyorganosiloxanes. By adding the polyorganosiloxane in this manner, side reactions between the polybutadiene chain having an active end and impurities contained in the polymerization system can be suppressed, and the reaction can be well controlled.

In addition, in the second step of the production method of the present invention, in the state before reacting the polybutadiene chain having an active end with the polyorganosiloxane represented by the general formula (1), the effect of the present invention is not inhibited. Within this range, a part of the active end of the polybutadiene chain having an active end may be coupled or modified by adding a conventionally commonly used coupling agent or modifier into the polymerization system. In this case, the amount of the coupling agent used is 0.05 mol or less per 1 mol of the polymerization initiator used in the polymerization in the first step, from the viewpoint of not inhibiting the effects of the present invention. It is preferable that the coupling agent be substantially not used.

一般式（２）中、Ｒ^９は、ヒドロカルビル基であり、Ａ^１は、活性末端を有するポリブタジエン鎖とポリオルガノシロキサンとの反応により生成した反応残基と反応しうる基であり、Ａ^２は、窒素原子を含有する基であり、ｐは０～２の整数、ｑは１～３の整数、ｒは１～３の整数、ｐ＋ｑ＋ｒ＝４である。 <3rd process>
Furthermore, in the production method of the present invention, a third step is further provided in which the polybutadiene chain reacted with the polyorganosiloxane obtained in the second step described above is reacted with a compound represented by the following general formula (2). Good too. By reacting the compound represented by the following general formula (2), the resulting rubber crosslinked product can be made to have low heat build-up and excellent wet grip properties.

In general formula (2), R ⁹ is a hydrocarbyl group, A ¹ is a group capable of reacting with a reactive residue produced by the reaction of a polybutadiene chain having an active end with polyorganosiloxane, and A ² is , a group containing a nitrogen atom, p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, and p+q+r=4.

The polybutadiene chain reacted with polyorganosiloxane used in the third step of the production method of the present invention may be one that has undergone the second step described above. The polybutadiene chain may include a polybutadiene chain having an active end into which a modified structure with polyorganosiloxane has been introduced, and may also include a polybutadiene chain having an unmodified active end that has not been modified with polyorganosiloxane. It's something you get. Furthermore, it may also include a polybutadiene chain into which a siloxane-modified structure has been introduced, in which the active end of the polybutadiene chain has an active end into which a polyorganosiloxane-modified structure has been introduced, and the active end has been converted into a hydroxyl group. It is something. Hereinafter, in the description of the third step, the polybutadiene chain reacted with polyorganosiloxane will be abbreviated as "polybutadiene chain" as appropriate.

In the compound represented by the general formula (2), R ⁹ in the general formula (2) is a hydrocarbyl group, such as an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group, etc. , is preferably an alkyl group having 1 to 6 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, pentyl group, hexyl group, etc. Among these, methyl group and ethyl group are more popular. preferable.

In the compound represented by the general formula (2), A ¹ in the general formula (2) is a reactive residue (typically, -O ^{-M +} ), and is preferably a group represented by -OR ¹⁰ (R ¹⁰ is a hydrogen atom or a hydrocarbyl group). Examples of the hydrocarbyl group that can constitute R ¹⁰ include alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, aralkyl groups, etc.; Preferably, it is an alkyl group of 6. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, pentyl group, hexyl group, etc. Among these, methyl group and ethyl group are more popular. preferable.

In the compound represented by general formula (2), A ² in general formula (2) is a group containing a nitrogen atom, and is not particularly limited as long as it is a group containing a nitrogen atom. Preferably, it is an organic group, such as a 3-aminopropyl group, 4-aminobutyl group, 3-(2-aminoethylamino)propyl group, 2-dimethylaminoethyl group, 3-dimethylaminopropyl group, 3- Diethylaminopropyl group, 3-dipropylaminopropyl group, 3-dibutylaminopropyl group, 3-phenylmethylaminopropyl group, 3-(4-methylpiperazinyl)propyl group, N,N-bis(trimethylsilyl)aminopropyl group, N,N-bis(triethylsilyl)aminopropyl group, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyl group, and the like. Among these, 3-aminopropyl group, 4-aminobutyl group, 3-(2-aminoethylamino)propyl group are used because they can further improve the low heat build-up and wet grip properties of the obtained crosslinked rubber product. A group containing a primary amino group having an active hydrogen atom and/or a secondary amino group having an active hydrogen atom, such as a group, is preferable. Note that the term "active hydrogen atom" refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably has a lower bond energy than a carbon-hydrogen bond in a polymethylene chain.

In the compound represented by general formula (2), p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, and p+q+r=4. From the viewpoint of reactivity with the reactive residue produced by the reaction of a polybutadiene chain having an active end with a polyorganosiloxane, preferably p is an integer of 0 to 1, q is an integer of 2 to 3, and r is an integer of 2 to 3. It is an integer of 1 to 2, more preferably p=0, q=3, and r=1. In addition, when p is 2, the two groups represented by ^R9 contained in one molecule of the compound represented by general formula (2) may be the same or different from each other. It may be. Similarly, when q is 2 or 3, multiple groups represented by ^A1 contained in one molecule of the compound represented by general formula (2) may be the same or mutually They may be different, and when r is 2 or 3, a plurality of groups represented by ^A2 contained in one molecule of the compound represented by general formula (2) may be the same. They may be different from each other.

Specific examples of the compound represented by general formula (2) are not particularly limited, but for example, A ² in general formula (2) represents a primary amino group having an active hydrogen atom and/or an active hydrogen atom. Examples of compounds that are groups containing a secondary amino group include 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropyl Compounds having a 3-aminopropyl group as ^A2 such as methyldiethoxysilane and 3-aminopropyltriethoxysilane; 4-aminobutyldimethylmethoxysilane, 4-aminobutylmethyldimethoxysilane, 4-aminobutyltrimethoxysilane , 4-aminobutyldimethylethoxysilane, 4-aminobutylmethyldiethoxysilane, 4-aminobutyltriethoxysilane, etc. Compounds having a 4-aminobutyl group as ^A2 ; 3-(2-aminoethylamino)propyl Dimethylmethoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propyldimethylethoxysilane, 3-(2-aminoethylamino)propyldimethylethoxysilane Examples of ^A2 include compounds having a 3-(2-aminoethylamino)propyl group, such as -aminoethylamino)propylmethyldiethoxysilane and 3-(2-aminoethylamino)propyltriethoxysilane.

In addition, as a compound in which A ² in general formula (2) is a group other than a group containing a primary amino group having an active hydrogen atom and/or a secondary amino group having an active hydrogen atom, 3-dimethylamino Propyltrimethoxysilane, 3-dimethylaminopropylmethyldimethoxysilane, 3-dimethylaminopropyldimethylmethoxysilane, 3-dimethylaminopropyltriethoxysilane, 3-dimethylaminopropylmethyldiethoxysilane, 3-dimethylaminopropyldimethylethoxysilane Compounds having a 3-dimethylaminopropyl group as ^A2 such as; 3-diethylaminopropyltrimethoxysilane, 3-diethylaminopropylmethyldimethoxysilane, 3-diethylaminopropyldimethylmethoxysilane, 3-diethylaminopropyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, A compound having a 3-diethylaminopropyl group as ^A2 such as diethylaminopropylmethyldiethoxysilane, 3-diethylaminopropyldimethylethoxysilane; 3-dipropylaminopropyltrimethoxysilane, 3-dipropylaminopropylmethyldimethoxysilane, 3 -dipropylaminopropyldimethylmethoxysilane, 3-dipropylaminopropyltriethoxysilane, 3-dipropylaminopropylmethyldiethoxysilane, 3-dipropylaminopropyldimethylethoxysilane, etc. as ^A2 , 3-dipropylamino Compounds having a propyl group; 3-dibutylaminopropyltrimethoxysilane, 3-dibutylaminopropylmethyldimethoxysilane, 3-dibutylaminopropyldimethylmethoxysilane, 3-dibutylaminopropyltriethoxysilane, 3-dibutylaminopropylmethyldiethoxy Compounds having a 3-dibutylaminopropyl group as ^A2 such as silane, 3-dibutylaminopropyldimethylethoxysilane; 3-phenylmethylaminopropyltrimethoxysilane, 3-phenylmethylaminopropylmethyldimethoxysilane, 3-phenylmethyl 3-phenylmethylaminopropyl group as ^A2 of aminopropyldimethylmethoxysilane, 3-phenylmethylaminopropyltriethoxysilane, 3-phenylmethylaminopropylmethyldiethoxysilane, 3-phenylmethylaminopropyldimethylethoxysilane, etc. Compounds with; 3-(4-methylpiperazinyl)propyltrimethoxysilane, 3-(4-methylpiperazinyl)propylmethyldimethoxysilane, 3-(4-methylpiperazinyl)propyldimethylmethoxysilane, 3- (4-methylpiperazinyl)propyltriethoxysilane, 3-(4-methylpiperazinyl)propylmethyldiethoxysilane, 3-(4-methylpiperazinyl)propyldimethylethoxysilane, etc. as ^A2 , 3 -(4-methylpiperazinyl) compound having a propyl group;

N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(trimethylsilyl) A compound having an N,N-bis(trimethylsilyl)aminopropyl group as ^A2 such as aminopropylmethyldiethoxysilane; N,N-bis(triethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl) Aminopropyltriethoxysilane, N,N-bis(triethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(triethylsilyl)aminopropylmethyldiethoxysilane ^etc. ) Compounds having an aminopropyl group; N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N,N',N'-tris(trimethylsilyl) -N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N, A ² such as N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N,N',N'-tris(trimethylsilyl)-N-( Compounds having a 2-aminoethyl)-3-aminopropyl group; and the like.

The amount of the compound represented by general formula (2) is not particularly limited, but is preferably 0.1 to 5 mol, more preferably 0.1 to 5 mol, per 1 mol of the polymerization initiator used in the first step. .2 to 2 mol, more preferably 0.4 to 1.5 mol. By controlling the amount of the compound represented by the general formula (2) within the above range, the resulting rubber crosslinked product can have excellent low heat generation properties and wet grip properties.

The time to add the compound represented by general formula (2) to the solution containing polybutadiene chains is after the polyorganosiloxane represented by general formula (1) is added in the second step mentioned above. Not particularly limited. For example, as in the second step described above, a state in which the polymerization reaction is not completed and the solution containing polybutadiene chains also contains monomers, more specifically, the solution containing polybutadiene chains is However, the compound represented by general formula (2) can be added to this solution while containing 100 ppm or more of the monomer, more preferably 300 to 50,000 ppm. By adding the compound represented by general formula (2) in this way, it is possible to suppress side reactions between the polybutadiene chains and impurities contained in the polymerization system, and to control the reaction well. Become. Alternatively, before or after adding the compound represented by the general formula (2) to a solution containing a polybutadiene chain, water or an alcohol such as methanol is added to the solution, so that the general formula (1 ) The reaction residue formed by the reaction with the polyorganosiloxane represented by ) may be hydrolyzed and converted into a hydroxyl group, and then the modification reaction may be performed. When adding the compound represented by the general formula (2) to a solution containing polybutadiene chains, the compound represented by the general formula (2) may be added after being dissolved in an inert solvent, or the compound represented by the general formula (2) may be added after being dissolved in an inert solvent. It may be added directly without being dissolved in a solvent. The reaction temperature and reaction time are the same as in the first step.

After reacting the compound represented by general formula (2), if necessary, a known polymerization terminator or the like is added to deactivate the reaction system, and then, if desired, a phenol stabilizer is added. Antioxidants such as , phosphorus stabilizers, sulfur stabilizers, crumbling agents, and scale inhibitors are added to the reaction solution, and then the polymerization solvent is separated from the reaction solution by direct drying or steam stripping. to recover polybutadiene rubber. Note that, before separating the polymerization solvent from the reaction solution, an extender oil may be mixed with the polymerization solution, and the polybutadiene rubber may be recovered as an oil extender rubber.

Extending oils used when recovering polybutadiene rubber as oil-extended rubber include, for example, paraffinic, aromatic and naphthenic petroleum softeners, vegetable softeners, and fatty acids. When a petroleum-based softener is used, it is preferable that the content of polycyclic aromatics extracted by the method IP346 (testing method of THE INSTITUTE PETROLEUM in the UK) is less than 3%. When an extender oil is used, the amount used is preferably 5 to 100 parts by weight, more preferably 10 to 60 parts by weight, even more preferably 20 to 50 parts by weight, based on 100 parts by weight of polybutadiene rubber.

In the production method of the present invention, when the molecular weight of the polybutadiene rubber produced is measured in terms of polystyrene by gel permeation chromatography, the peak top molecular weight (Mp1) of the polybutadiene chain obtained in the first step is determined. ), the area ratio (X) of the peak portion with the peak top molecular weight (Mp2) in the range of 1.5 times or more and less than 2.5 times to the total elution area, and the peak top molecular weight in the range of 2.5 times or more A specific relationship is established between the area ratio (Y) of the peak portion having (Mp3) to the total elution area. That is, the ratio of the area ratio (X) of the peak portion having the peak top molecular weight (Mp2) to the total elution area to the area ratio (Y) of the peak portion having the peak top molecular weight (Mp3) to the total elution area is expressed as :Y=75:25 to 55:45.

Here, FIG. 1 shows an example of a chart obtained when performing gel permeation chromatography measurement on polybutadiene rubber obtained by the manufacturing method of the present invention. As shown in FIG. 1, the polybutadiene rubber obtained by the production method of the present invention has a peak having a peak top molecular weight (Mp1') on the lowest molecular weight side and a peak having a peak top molecular weight (Mp1') on a higher molecular weight side than the peak top molecular weight (Mp1'). has a peak having a peak top molecular weight (Mp2) and a peak having a peak top molecular weight (Mp3).

In FIG. 1, the peak having a peak top molecular weight (Mp1') is mainly a peak derived from a polymer chain that has not been coupled with polyorganosiloxane, and therefore It corresponds to the peak of the chain peak top molecular weight (Mp1). In addition, the peak having the peak top molecular weight (Mp2) is mainly a peak derived from a polymer chain dimerized by coupling with polyorganosiloxane, and the peak top molecular weight (Mp2) is usually determined by the first step. It appears in a range of 1.5 times or more and less than 2.5 times the peak top molecular weight (Mp1) of the obtained polybutadiene chain (that is, the peak top molecular weight (Mp1') on the lowest molecular weight side). Furthermore, the peak having the peak top molecular weight (Mp3) is mainly a peak derived from a polymer chain trimerized or further multimerized by coupling with polyorganosiloxane, and the peak top molecular weight (Mp3) is usually It appears in a range of 2.5 times or more of the peak top molecular weight (Mp1) of the polybutadiene chain obtained in the first step (that is, the peak top molecular weight (Mp1') on the lowest molecular weight side).

In the present invention, the peak top molecular weight (Mp1) of the polybutadiene chain obtained in the first step (that is, the peak top molecular weight (Mp1') on the lowest molecular weight side) is in the range of 250,000 to 350,000. and the ratio of the area ratio (X) of the peak portion having the peak top molecular weight (Mp2) to the total elution area to the area ratio (Y) of the peak portion having the peak top molecular weight (Mp3) to the total elution area. , X:Y=75:25 to 55:45, thereby making it possible to effectively reduce the tackiness of the resulting polybutadiene rubber at high temperatures. The rubber crosslinked product obtained using the above method can be made to have low heat build-up and excellent wet grip properties. The ratio of the area ratio (X) of the peak portion having the peak top molecular weight (Mp2) to the total elution area to the area ratio (Y) of the peak portion having the peak top molecular weight (Mp3) to the total elution area is :Y=75:25 to 55:45, preferably X:Y=73:27 to 58:42, more preferably X:Y=70:30 to 60:40. The ratio of the area ratio (X) of the peak portion having the peak top molecular weight (Mp2) to the total elution area to the area ratio (Y) of the peak portion having the peak top molecular weight (Mp3) to the total elution area is within the above range. Although the method is not particularly limited, it can be adjusted by controlling the polymerization conditions (for example, polymerization temperature, etc.) and the reaction conditions in the second step (for example, the amount of polyorganosiloxane used, etc.).

The area ratio (X) of the peak portion having the peak top molecular weight (Mp2) to the total elution area can be calculated, for example, by the following method. That is, first, the peak having the peak top molecular weight (Mp1) of the polybutadiene chain (that is, the peak top molecular weight (Mp1') on the lowest molecular weight side) and the peak having the peak top molecular weight (Mp2) shown in FIG. The part included in the range from the minimum point α between the peak with the peak top molecular weight (Mp2) and the minimum point β between the peak with the peak top molecular weight (Mp3) is defined as the peak top molecular weight (Mp2). It is calculated as the elution area of the peak portion. Then, by dividing the elution area of the peak portion having the calculated peak top molecular weight (Mp2) by the total elution area, the area ratio (X) of the peak portion having the peak top molecular weight (Mp2) to the total elution area is determined. be able to.

Further, the area ratio (Y) of the peak portion having the peak top molecular weight (Mp3) to the total elution area can be calculated, for example, by the following method. That is, first, the range on the higher molecular weight side than the minimum point β between the peak having the peak top molecular weight (Mp2) and the peak having the peak top molecular weight (Mp3) shown in FIG. ) is calculated as the elution area of the peak portion. Then, by dividing the elution area of the peak portion having the calculated peak top molecular weight (Mp3) by the total elution area, the area ratio (Y) of the peak portion having the peak top molecular weight (Mp3) to the total elution area is determined. be able to.

The coupling rate of the polybutadiene rubber obtained by the production method of the present invention (i.e., the area ratio (X) of the peak portion having the peak top molecular weight (Mp2) to the total elution area and the peak having the peak top molecular weight (Mp3)) The total area ratio (Y) of the portion to the total elution area (unit: area %) is not particularly limited, but is preferably 40 to 80 area %, more preferably 45 to 75 area %, particularly preferably 50 ~70 area%. When the coupling rate is within the above range, the tackiness of the polybutadiene rubber at high temperatures can be further reduced.

Furthermore, the weight average molecular weight (Mw) of the polybutadiene rubber obtained by the production method of the present invention is preferably 300,000 to 2,000,000, more preferably 400,000 to 1,000,000, and particularly preferably 500,000 to 2,000,000. ,000 to 800,000. By setting the weight average molecular weight of the polybutadiene rubber within the above range, silica can be easily blended into the polybutadiene rubber, the processability of the rubber composition can be further improved, and furthermore, the resulting crosslinked rubber product has a low heat generation. It is possible to further improve grip properties and wet grip properties.

The molecular weight distribution of the polybutadiene rubber obtained by the production method of the present invention, expressed as the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw/Mn), is preferably 1.1 to 3.0. It is preferably from 1.2 to 2.5, more preferably from 1.2 to 2.2. By controlling the molecular weight distribution (Mw/Mn) of the polybutadiene rubber within the above range, it is possible to further improve the low heat build-up and wet grip properties of the resulting crosslinked rubber product. Note that the weight average molecular weight (Mw) and number average molecular weight (Mn) can be determined as values measured by gel permeation chromatography in terms of polystyrene.

Further, the Mooney viscosity (ML1+4, 100°C) of the polybutadiene rubber obtained by the production method of the present invention is preferably 60 to 90, more preferably 62 to 88, particularly preferably 65 to 85. In addition, when polybutadiene rubber is used as an oil-extended rubber, it is preferable that the Mooney viscosity of the oil-extended rubber is within the above range.

The polybutadiene rubber thus obtained by the production method of the present invention can be suitably used for various purposes after adding compounding agents such as fillers and crosslinking agents. In particular, when silica is blended as a filler, a rubber composition capable of providing a rubber crosslinked product with low heat build-up and excellent wet grip properties is provided.

<Rubber composition>
The rubber composition of the present invention contains a rubber component containing 15 to 50% by weight of polybutadiene rubber obtained by the production method of the present invention described above, and silica, and the amount of silica is based on 100 parts by weight of the rubber component. It is a composition of polybutadiene rubber containing 10 to 120 parts by weight.

Examples of the silica used in the present invention include dry process white carbon, wet process white carbon, colloidal silica, and precipitated silica. Among these, wet process white carbon containing hydrated silicic acid as a main component is preferred. Further, a carbon-silica dual phase filler in which silica is supported on the surface of carbon black may be used. These silicas can be used alone or in combination of two or more. The nitrogen adsorption specific surface area (measured by the BET method according to ASTM D3037-81) of the silica used is preferably 50 to 300 m ² /g, more preferably 80 to 220 m ² /g, particularly preferably 100 to 170 m ² /g. It is g. Further, the pH of silica is preferably 5 to 10.

The amount of silica blended in the rubber composition of the present invention is 10 to 200 parts by weight, preferably 30 to 150 parts by weight, more preferably 50 to 100 parts by weight, based on 100 parts by weight of the rubber component in the rubber composition. Department. By setting the blending amount of silica within the above range, the processability of the rubber composition becomes excellent, and the wet grip properties and low heat build-up of the resulting rubber crosslinked product can be further improved.

The rubber composition of the present invention may further contain a silane coupling agent from the viewpoint of further improving low heat generation properties. Examples of the silane coupling agent include vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 3-octanoylthio- 1-propyl-triethoxysilane, bis(3-(triethoxysilyl)propyl)disulfide, bis(3-(triethoxysilyl)propyl)tetrasulfide, γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide, and γ -trimethoxysilylpropylbenzothiazyl tetrasulfide and the like. These silane coupling agents can be used alone or in combination of two or more. The blending amount of the silane coupling agent is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight, based on 100 parts by weight of silica.

Further, the rubber composition of the present invention may further contain carbon black such as furnace black, acetylene black, thermal black, channel black, and graphite. Among these, furnace black is preferred. These carbon blacks can be used alone or in combination of two or more. The amount of carbon black blended is usually 120 parts by weight or less per 100 parts by weight of the rubber component in the rubber composition.

Note that the method of adding silica to the rubber component containing polybutadiene rubber obtained by the production method of the present invention is not particularly limited, and there is a method of adding silica to a solid rubber component and kneading it (dry kneading method), a method of adding silica to a solid rubber component and kneading it, A method of adding it to a solution containing rubber, coagulating and drying it (wet kneading method), etc. can be applied.

Moreover, it is preferable that the rubber composition of the present invention further contains a crosslinking agent. Examples of the crosslinking agent include sulfur, halogenated sulfur, organic peroxides, quinone dioximes, organic polyvalent amine compounds, and alkylphenol resins having a methylol group. Among these, sulfur is preferably used. The amount of the crosslinking agent to be blended is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, particularly preferably 1 to 4 parts by weight, based on 100 parts by weight of the rubber component in the rubber composition. It is.

Furthermore, in addition to the above-mentioned components, the rubber composition of the present invention also contains a crosslinking accelerator, a crosslinking activator, an anti-aging agent, a filler (excluding the above silica and carbon black), an activator, and a process oil. , plasticizers, lubricants, tackifiers, compatibilizers, and other compounding agents can be added in necessary amounts.

When using sulfur or a sulfur-containing compound as a crosslinking agent, it is preferable to use a crosslinking accelerator and a crosslinking activator together. Examples of crosslinking accelerators include sulfenamide crosslinking accelerators; guanidine crosslinking accelerators; thiourea crosslinking accelerators; thiazole crosslinking accelerators; thiuram crosslinking accelerators; dithiocarbamic acid crosslinking accelerators; Examples include crosslinking accelerators; and the like. Among these, those containing a sulfenamide crosslinking promoter are preferred. These crosslinking accelerators may be used alone or in combination of two or more. The amount of the crosslinking accelerator is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, particularly preferably 1 to 4 parts by weight, based on 100 parts by weight of the rubber component in the rubber composition. Department.

Examples of the crosslinking activator include higher fatty acids such as stearic acid; zinc oxide; and the like. These crosslinking activators may be used alone or in combination of two or more. The amount of the crosslinking activator to be blended is preferably 0.05 to 20 parts by weight, particularly preferably 0.5 to 15 parts by weight, based on 100 parts by weight of the rubber component in the rubber composition.

Furthermore, the rubber composition of the present invention may contain other rubbers other than the polybutadiene rubber obtained by the above-described production method of the present invention. Other rubbers include, for example, natural rubber, polyisoprene rubber, emulsion polymerized styrene-butadiene copolymer rubber, solution polymerized styrene-butadiene copolymer rubber, and polybutadiene rubber (high cis-BR, low cis-BR). Also, polybutadiene rubber containing crystal fibers made of 1,2-polybutadiene polymer may be used), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, acrylonitrile-butadiene Among copolymer rubbers, acrylonitrile-styrene-butadiene copolymer rubbers, etc., it refers to those other than the polybutadiene rubber obtained by the production method of the present invention described above. Among these, natural rubber, polyisoprene rubber, polybutadiene rubber, and solution polymerized styrene-butadiene copolymer rubber are preferred, and solution polymerized styrene-butadiene copolymer rubber is preferred. In addition, from the viewpoint of further improving low heat build-up and wet grip properties, among solution-polymerized styrene-butadiene copolymer rubbers, it is possible to obtain a compound obtained by modifying using the above general formula (1) as a modifier. , solution-polymerized modified styrene-butadiene copolymer rubber is particularly preferred. These rubbers can be used alone or in combination of two or more.

In the rubber composition of the present invention, the polybutadiene rubber obtained by the production method of the present invention preferably accounts for 15 to 50% by weight, more preferably 20 to 40% by weight of the rubber component in the rubber composition. , more preferably accounts for 25 to 35% by weight. By including the polybutadiene rubber obtained by the production method of the present invention in the rubber component in such a proportion, a crosslinked rubber product with improved low heat build-up and wet grip properties can be obtained.

In order to obtain the rubber composition of the present invention, each component may be kneaded according to a conventional method. For example, after kneading components other than heat-labile components such as a crosslinking agent and a crosslinking accelerator with polybutadiene rubber, A desired composition can be obtained by mixing thermally unstable components such as a crosslinking agent and a crosslinking accelerator into the kneaded product. The kneading temperature of the components excluding thermally unstable components and the polybutadiene rubber is preferably 80 to 200°C, more preferably 120 to 180°C, and the kneading time is preferably 30 seconds to 30 minutes. Further, the kneaded material and the heat-unstable components are mixed together usually after cooling to 100° C. or lower, preferably 80° C. or lower.

<Rubber crosslinked product>
The crosslinked rubber product of the present invention is obtained by crosslinking the rubber composition of the present invention described above.
The rubber crosslinked product of the present invention can be obtained by molding the rubber composition of the present invention using a molding machine corresponding to a desired shape, such as an extruder, an injection molding machine, a compressor, a roll, etc., and then heating the product. It can be manufactured by performing a crosslinking reaction and fixing the shape as a crosslinked product. In this case, the crosslinking may be performed after pre-forming or at the same time as the molding. The molding temperature is usually 10 to 200°C, preferably 25 to 120°C. The crosslinking temperature is usually 100 to 200°C, preferably 130 to 190°C, and the crosslinking time is usually 1 minute to 24 hours, preferably 2 minutes to 12 hours, particularly preferably 3 minutes to 6 hours. .

Further, depending on the shape, size, etc. of the crosslinked rubber product, even if the surface is crosslinked, the inside may not be sufficiently crosslinked, so secondary crosslinking may be performed by further heating.

As the heating method, a general method used for crosslinking rubber such as press heating, steam heating, oven heating, hot air heating, etc. may be appropriately selected.

The rubber crosslinked product of the present invention thus obtained is obtained using the polybutadiene rubber obtained by the production method of the present invention described above, and therefore has excellent low heat build-up and wet grip properties. Utilizing these characteristics, the crosslinked rubber product of the present invention can be used, for example, in tires for various parts of the tire, such as the cap tread, base tread, carcass, sidewall, and bead; hoses, belts, mats, and tires. It can be used for various purposes such as materials for swing rubber and other various industrial products; impact resistance improvers for resins; resin film cushioning agents; shoe soles; rubber shoes; golf balls; toys; In particular, the rubber crosslinked product of the present invention can be suitably used in various tire parts such as treads, carcass, sidewalls, and bead parts in various tires such as all-season tires, high-performance tires, and studless tires. In particular, since it has excellent low heat generation properties, it can be particularly suitably used for treads of fuel-efficient tires.

Hereinafter, the present invention will be explained based on more detailed examples, but the present invention is not limited to these examples. In addition, in the following, "parts" are based on weight unless otherwise specified. In addition, the tests and evaluations were conducted in accordance with the following.

[Weight average molecular weight, peak top molecular weight, coupling rate]
The weight average molecular weight, peak top molecular weight, and coupling rate were obtained by gel permeation chromatography (GPC) to obtain a chart based on the molecular weight in terms of polystyrene, and based on the obtained chart. The specific measurement conditions for gel permeation chromatography were as follows.
Measuring instrument: High performance liquid chromatograph (manufactured by Tosoh Corporation, product name "HLC-8220")
Column: Two polystyrene columns manufactured by Tosoh Corporation, trade name "GMH-HR-H" were connected in series.
Detector: Differential refractometer Eluent: Tetrahydrofuran Column temperature: 40°C
Regarding the peak top molecular weight, the area ratio of the peak portion having a peak top molecular weight (Mp2) of 1.5 times or more and less than 2.5 times the peak top molecular weight (Mp1') indicated by the peak with the smallest molecular weight. (X) and the area ratio of the peak portion having a peak top molecular weight (Mp3) that is 2.5 times or more and less than 3.5 times the peak top molecular weight (Mp1') shown by the peak derived from the polymer with the smallest molecular weight ( Y) was calculated according to the method described above. Further, the sum of the determined area ratio (X) and area ratio (Y) was determined as a coupling rate (unit: area %). Furthermore, as a result of GPC measurement, the peak top molecular weight (Mp1') shown by the peak with the smallest molecular weight is substantially the same as the peak top molecular weight (Mp1) of the polybutadiene chain having an active end before reacting with the polyorganosiloxane. Therefore, in this example, the peak top molecular weight (Mp1') shown by the peak with the smallest molecular weight was taken as the peak top molecular weight (Mp1) of the polybutadiene chain having an active end.

[Aromatic vinyl monomer unit content, vinyl bond content]
The aromatic vinyl monomer unit content and the vinyl bond content were measured by ¹ H-NMR.

[Mooney viscosity of polybutadiene rubber (ML1+4, 100℃)]
It was measured using a Mooney viscometer (manufactured by Shimadzu Corporation) in accordance with JIS K6300.

[Tackiness (adhesiveness of polybutadiene rubber)]
Tackiness was evaluated by measuring the loss modulus in shear mode at a temperature of 130° C., a dynamic strain of 10%, and a shear rate of 30S ⁻¹ using RPA-2000 (manufactured by Alpha Technologies). The value of the loss modulus was expressed as an index with the measured value of Comparative Example 1 as 100. The smaller the index, the lower the tackiness of the polybutadiene rubber at high temperatures, which means that the operability during drying is more stable.

[Low heat build-up of cross-linked rubber products]
Using ARES-G2 (manufactured by TA Instruments), the tan δ at 30°C was determined for a test piece with a length of 50 mm, a width of 12.7 mm, and a thickness of 2 mm under the conditions of a dynamic strain of 2.5% and a frequency of 10 Hz. Low heat generation was evaluated by measurement. The value of tan δ was expressed as an index with the measured value of Comparative Example 7 as 100. The higher this index is, the better the low heat generation property is.

[Wet grip properties of cross-linked rubber products]
Using ARES-G2 (manufactured by TA Instruments), a test piece with a length of 50 mm, a width of 12.7 mm, and a thickness of 2 mm was heated from -100°C to 20°C under the conditions of a dynamic strain of 0.5% and a frequency of 10 Hz. The wet grip property was evaluated by raising the temperature stepwise at intervals of 4° C. and measuring the value of the tan δ peak. The peak value of tan δ was expressed as an index with the measured value of Comparative Example 7 as 100. The higher this index is, the better the wet grip property is.

[Example 1]
After charging 5,670 g of cyclohexane and 700 g of 1,3-butadiene in an autoclave equipped with a stirrer under a nitrogen atmosphere, the amount of n- Butyl lithium was added, and 6.25 mmol of n-butyl lithium was added for use in the polymerization reaction, and polymerization was started at 45°C. Twenty minutes after the start of polymerization, 300 g of 1,3-butadiene was continuously added over 30 minutes. The maximum temperature during the polymerization reaction was 72°C. After the continuous addition, the polymerization reaction is continued for another 10 minutes, and after confirming that the polymerization conversion rate is in the range of 95% to 100%, a polyorganic compound represented by the following formula (8) is added to the polymerization solution. 20% by weight of 3.78 mmol of siloxane (the values of m and k are average values) (an amount equivalent to 0.6 times the mole of n-butyllithium used in polymerization in terms of epoxy groups contained in polyorganosiloxane) It was added in the form of a xylene solution and reacted for 20 minutes. Next, 6.25 mmol of 3-aminopropyltrimethoxysilane (equivalent to 1 mole of n-butyllithium used in polymerization) was added in the form of a 25% by weight cyclohexane solution, and the mixture was reacted for 15 minutes. Thereafter, methanol in an amount equivalent to twice the molar amount of n-butyllithium used in the polymerization was added as a polymerization terminator to obtain a solution containing polybutadiene rubber.

Next, 0.3 parts of 2,4-bis(n-octylthiomethyl)-6-methylphenol was added as an antiaging agent per 100 parts of the rubber component to the solution containing the obtained polybutadiene rubber. The solvent was removed from this solution by steam stripping, and the solution was vacuum dried at 60° C. for 24 hours to obtain a solid polybutadiene rubber (BR1). Regarding the obtained polybutadiene rubber (BR1), weight average molecular weight, peak top molecular weight (area ratio of peaks corresponding to each peak top molecular weight (X, Y)), coupling rate, vinyl bond content, Mooney viscosity and tackiness were measured. The results are shown in Table 1.

[Example 2]
Polybutadiene rubber (BR2) was obtained in the same manner as in Example 1, except that 3-aminopropyltrimethoxysilane was not added, and measurements were carried out in the same manner. The results are shown in Table 1.

[Example 3]
335.0 g of cyclohexane and 0.80 mmol of tetramethylethylenediamine were added to a pressure-resistant glass container with a capacity of 800 ml that was purged with nitrogen, and further, 7.98 mmol of n-butyllithium was added. Next, 28.79 g of isoprene and 2.33 g of styrene were slowly added and reacted in a 50° C. water bath for 120 minutes to obtain a polymer block (A) having an active end. This polymer block (A) has a weight average molecular weight (Mw) of 6,680, a molecular weight distribution (Mw/Mn) of 1.10, a styrene monomer unit content of 7.5% by weight, and an isoprene monomer unit. The content was 92.5% by weight, and the vinyl bond content was 7.7% by weight.

Next, in an autoclave equipped with a stirrer, 5,670 g of cyclohexane and 700.0 g of 1,3-butadiene were charged under a nitrogen atmosphere, and then the amount necessary for neutralizing impurities that inhibit polymerization contained in cyclohexane and 1,3-butadiene was added. n-butyllithium was added thereto, and the entire amount of the polymer block (A) having an active end obtained above was added, and polymerization was started at 45°C. After 20 minutes had passed since the start of polymerization, 300.0 g of 1,3-butadiene was continuously added over 30 minutes. The maximum temperature during the polymerization reaction was 72°C. After the continuous addition, the polymerization reaction was continued for another 20 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, the polyorganosiloxane (m and The value of k is an average value) 3.78 mmol (an amount equivalent to 0.6 times the mole of n-butyllithium used in polymerization in terms of epoxy groups contained in polyorganosiloxane)) was added to a 20% by weight xylene solution. The mixture was added in this condition and reacted for 30 minutes. Next, 6.25 mmol of 3-aminopropyltrimethoxysilane (equivalent to 1 mole of n-butyllithium used in polymerization) was added in the form of a 25% by weight cyclohexane solution, and the mixture was reacted for 30 minutes. Thereafter, as a polymerization terminator, methanol was added in an amount equivalent to twice the mole of n-butyllithium used to obtain a solution containing polybutadiene rubber.

Next, 0.3 parts of 2,4-bis(n-octylthiomethyl)-6-methylphenol was added as an antiaging agent per 100 parts of the rubber component to the solution containing the obtained polybutadiene rubber. The solvent was removed from this solution by steam stripping, and the solution was vacuum dried at 60° C. for 24 hours to obtain solid polybutadiene rubber (BR3). Regarding the obtained polybutadiene rubber (BR3), each measurement was performed in the same manner as in Example 1. The results are shown in Table 1.

[Comparative example 1]
After charging 5,670 g of cyclohexane and 700 g of 1,3-butadiene in an autoclave equipped with a stirrer under a nitrogen atmosphere, the amount of n- Butyl lithium was added, and 8.33 mmol of n-butyl lithium was added for use in the polymerization reaction, and polymerization was started at 50°C. Twenty minutes after the start of polymerization, 300 g of 1,3-butadiene was continuously added over 30 minutes. The maximum temperature during the polymerization reaction was 72°C. After the continuous addition, the polymerization reaction was continued for another 20 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.333 mmol of 1,6-bis(trichlorosilyl)hexane (polymerization (equivalent to 0.04 times the mole of n-butyllithium used in the above) was added in the form of a 40% by weight cyclohexane solution, and the mixture was reacted for 30 minutes. Furthermore, 2.92 mmol (in terms of epoxy groups contained in the polyorganosiloxane) of the polyorganosiloxane represented by the above formula (8) (m and k are average values) was added to the polymerization solution. An amount equivalent to 0.35 times the mole of n-butyllithium) was added in the form of a 20% by weight xylene solution, and the mixture was reacted for 30 minutes. Next, 8.33 mmol of tetramethoxysilane (equivalent to 1 mole of n-butyllithium used in the polymerization) was added in the form of a 25% by weight cyclohexane solution, and the mixture was reacted for 30 minutes. Thereafter, as a polymerization terminator, methanol was added in an amount equivalent to twice the mole of n-butyllithium used to obtain a solution containing polybutadiene rubber.

Next, 0.3 parts of 2,4-bis(n-octylthiomethyl)-6-methylphenol was added as an antiaging agent per 100 parts of the rubber component to the solution containing the obtained polybutadiene rubber. The solvent was removed from this solution by steam stripping, and the solution was vacuum dried at 60° C. for 24 hours to obtain solid polybutadiene rubber (BR4). Regarding the obtained polybutadiene rubber (BR4), each measurement was performed in the same manner as in Example 1. The results are shown in Table 1.

[Comparative example 2]
After charging 5,670 g of cyclohexane and 700 g of 1,3-butadiene in an autoclave equipped with a stirrer under a nitrogen atmosphere, the amount of n- Butyl lithium was added, and 8.33 mmol of n-butyl lithium was added for use in the polymerization reaction, and polymerization was started at 50°C. Twenty minutes after the start of polymerization, 300 g of 1,3-butadiene was continuously added over 30 minutes. The maximum temperature during the polymerization reaction was 80°C.
After the completion of the continuous addition, the polymerization reaction was continued for another 20 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, the polyorganic compound represented by the above formula (8) was added to the polymerization solution. 20% by weight of 3.75 mmol of siloxane (the values of m and k are average values) (an amount equivalent to 0.45 times the mole of n-butyllithium used in polymerization in terms of epoxy groups contained in polyorganosiloxane) It was added in the form of a xylene solution and reacted for 30 minutes. Next, 8.33 mmol of 3-(2-aminoethylamino)propyltrimethoxysilane (equivalent to 1 mole of n-butyllithium used in polymerization) was added in the form of a 25% by weight cyclohexane solution, and the mixture was allowed to react for 30 minutes. Ta. Thereafter, as a polymerization terminator, methanol was added in an amount equivalent to twice the mole of n-butyllithium used to obtain a solution containing polybutadiene rubber.

Next, 0.3 parts of 2,4-bis(n-octylthiomethyl)-6-methylphenol was added as an antiaging agent per 100 parts of the rubber component to the solution containing the obtained polybutadiene rubber. The solvent was removed from this solution by steam stripping, and the solution was vacuum dried at 60° C. for 24 hours to obtain a solid polybutadiene rubber (BR5). Regarding the obtained polybutadiene rubber (BR5), each measurement was performed in the same manner as in Example 1. The results are shown in Table 1.

[Comparative example 3]
Polybutadiene rubber (BR6) was obtained in the same manner as in Example 3, except that the polymerization initiation temperature was 50°C. In addition, in Comparative Example 3, the maximum temperature during the polymerization reaction was 80°C. Then, the obtained polybutadiene rubber (BR6) was subjected to various measurements in the same manner as in Example 1. The results are shown in Table 1.

[Reference example 1]
After charging 5,670 g of cyclohexane, 170 g of styrene, 430 g of 1,3-butadiene, and 10.0 mmol of tetramethylethylenediamine in an autoclave equipped with a stirrer under a nitrogen atmosphere, the polymerization contained in cyclohexane, styrene, and 1,3-butadiene was inhibited. n-butyllithium was added in the amount necessary to neutralize impurities. Thereafter, 5.6 mmol of n-butyllithium was added for use in the polymerization reaction, and polymerization was started at 40°C. Ten minutes after starting the polymerization, 40 g of styrene and 360 g of 1,3-butadiene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 70°C. After the continuous addition was completed, the polymerization reaction was continued for another 10 minutes, and after confirming that the polymerization conversion was in the range of 95% to 100%, a small amount of the polymerization solution was sampled. A small amount of the sampled polymer solution was added with excess methanol to stop the reaction, and then air-dried to obtain a polymer, which was used as a sample for gel permeation chromatography analysis. The weight average molecular weight of the sampled polymer was 248,000.

Immediately after sampling a small amount of the polymerization solution, 0.278 mmol of tin tetrachloride as a coupling agent was added in the form of a 20% by weight cyclohexane solution, and the mixture was reacted at 65° C. for 10 minutes. Next, 0.024 mmol of polyorganosiloxane represented by the above formula (8) was added as a modifier in the form of a 40% by weight xylene solution, and the mixture was reacted at 65° C. for 20 minutes. Thereafter, as a polymerization terminator, methanol was added in an amount equivalent to twice the mole of n-butyllithium used in the polymerization reaction to obtain a solution containing modified styrene-butadiene rubber.

Then, 0.2 parts of 2,4-bis(n-octylthiomethyl)-6-methylphenol was added as an antiaging agent per 100 parts of the rubber component to the solution containing the obtained modified styrene-butadiene rubber. did. Next, the solvent was removed by steam stripping, and the solid rubber was collected, dehydrated by rolling, and further dried in a hot air dryer to obtain a modified styrene-butadiene rubber. As a result of measuring the amount of bound styrene, vinyl bond content of the butadiene unit portion, weight average molecular weight, glass transition temperature (Tg), and Mooney viscosity (ML1+4,100°C) of the obtained modified styrene-butadiene rubber, the amount of bound styrene was determined. was 21%, the vinyl bond content of the butadiene unit portion was 63%, the weight average molecular weight was 449,000, and the Mooney viscosity (ML1+4,100°C) was 62.

[Example 4]
Using a Banbury mixer with a capacity of 250 ml, 30 parts of the polybutadiene rubber (BR1) obtained in Example 1 and 70 parts of the modified styrene-butadiene rubber obtained in Reference Example 1 were masticated for 30 seconds, and then silica ( Product name "ULTASIL 7000GR", manufactured by Evonik; BET specific surface area = 175 m ² /g) 53.3 parts, silane coupling agent (bis(3-(triethoxysilyl)propyl) disulfide, product name "Si75", manufactured by Evonik) 6.4 parts (manufactured by JXTG Energy Corporation) and 30 parts of process oil (t-DAE; manufactured by JXTG Energy Corporation) were added and kneaded for 1.5 minutes at a starting temperature of 80°C. To this kneaded material, 26.6 parts of silica (trade name "ULTASIL 7000GR", manufactured by Evonik; BET specific surface area = 112 m ² /g), 3 parts of zinc oxide, 2 parts of stearic acid, and an anti-aging agent (trade name " 2 parts of "Nocrac 6C" (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) were added and kneaded for an additional 2.5 minutes, and the rubber kneaded product was discharged from the Banbury mixer. The temperature of the rubber kneaded product at the end of kneading was 150°C. After the rubber kneaded product was cooled to room temperature, it was kneaded again in the Banbury mixer for 3 minutes, and then the rubber kneaded product was discharged from the Banbury mixer. Next, using an open roll at 50°C, the obtained rubber kneaded product, 1.8 parts of sulfur, and crosslinking accelerators (1.7 parts of N-cyclohexyl-2-benzothiazylsulfenamide and 1 part of diphenylguanidine) were mixed together. After kneading the rubber composition (mixture with .7 parts), a sheet-like rubber composition was taken out.
Then, the obtained rubber composition was press-crosslinked at 160° C. for 15 minutes to prepare a test piece, and the obtained test piece was evaluated for fuel efficiency and wet grip property. The results are shown in Table 2.

[Example 5, 6]
The same procedure as in Example 4 was carried out, except that the polybutadiene rubber (BR2) and polybutadiene rubber (BR3) obtained in Examples 2 and 3 were used in place of the polybutadiene rubber (BR1) obtained in Example 1. Rubber compositions and crosslinked rubber products were obtained and evaluated in the same manner. The results are shown in Table 2.

[Comparative Examples 4 to 6]
Except that the polybutadiene rubber (BR4), polybutadiene rubber (BR5), and polybutadiene rubber (BR6) obtained in Comparative Examples 1 to 3 were used in place of the polybutadiene rubber (BR1) obtained in Example 1, respectively. A rubber composition and a crosslinked rubber product were obtained in the same manner as in Example 4, and evaluated in the same manner. The results are shown in Table 2.

[Comparative example 7]
Except that polybutadiene rubber (trade name "Nipol BR1220", manufactured by Nippon Zeon Co., Ltd., polybutadiene rubber not reacted with polyorganosiloxane) was used in place of the polybutadiene rubber (BR1) obtained in Example 1. Rubber compositions and crosslinked rubber products were obtained in the same manner as in Example 4, and evaluated in the same manner. The results are shown in Table 2.

From the results in Tables 1 and 2, the following points can be confirmed.
That is, the polybutadiene rubber obtained by the method for producing polybutadiene rubber of the present invention had low tackiness, and the rubber crosslinked product obtained using the same had excellent low heat build-up and wet grip properties ( Examples 1 to 3, Examples 4 to 6). Therefore, the polybutadiene rubber obtained by the method for producing polybutadiene rubber of the present invention can effectively prevent the rubber polymers from adhering to each other at high temperatures, and the rubber composition obtained using the polybutadiene rubber of the present invention It can be said that the product and its rubber crosslinked product have low heat build-up and good wet grip properties, and can be suitably used for tire applications such as tire treads.
In contrast, the area ratio (X) of the peak portion having the peak top molecular weight (Mp2) to the total elution area and the area of the peak portion having the peak top molecular weight (Mp3) to the total elution area in a range of 2.5 times or more Polybutadiene rubber whose ratio (Y) is outside the range specified in the present invention, and polybutadiene rubber that has not been modified with polyorganosiloxane, have low heat build-up and wet grip properties when made into a rubber crosslinked product. They were inferior (Comparative Examples 1 to 3, Comparative Examples 4 to 6). Moreover, the polybutadiene rubbers obtained in Comparative Examples 1 and 2 had high tackiness, and the rubber polymers were likely to stick together at high temperatures.

Claims (10)

A first step of polymerizing a monomer containing 1,3-butadiene using a polymerization initiator in an inert solvent to obtain a polybutadiene chain having an active end;
A method for producing polybutadiene rubber, comprising a second step of reacting the polybutadiene chain having an active end with a polyorganosiloxane represented by the following general formula (1),
The peak top molecular weight (Mp1) detected by gel permeation chromatography of the polybutadiene chain having an active end is 250,000 to 350,000,
The polybutadiene rubber has a peak top molecular weight (Mp2) in a range of 1.5 times or more and less than 2.5 times the peak top molecular weight (Mp1) when the molecular weight is measured by gel permeation chromatography. The ratio of the area ratio (X) of the peak portion to the total elution area and the area ratio (Y) to the total elution area of the peak portion having a peak top molecular weight (Mp3) in a range of 2.5 times or more is X:Y A method for producing polybutadiene rubber in which the ratio is 75:25 to 55:45.

(In general formula (1), R ¹ to R ⁸ are an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and these may be the same or different. .X ¹ and X ⁴ are an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a group having 4 to 12 carbon atoms containing an epoxy group. X ² is a group selected from the group consisting of 4 to 12 carbon atoms containing an epoxy group, and these groups may be the same or different from each other. ² may be the same ^or different. X ³ is a group containing 2 to 20 alkylene glycol repeating units, and when there is a plurality of (m is an integer from 30 to 120 , n is an integer from 0 to 200, k is an integer from 0 to 200, and m+n+k is 30 or more.) The method for producing polybutadiene rubber according to claim 1, wherein the polybutadiene rubber has a Mooney viscosity (ML1+4, 100°C) of 60 to 90. The polybutadiene rubber according to claim 1 or 2, further comprising a third step of reacting a compound represented by the following general formula (2) with the polybutadiene chain reacted with the polyorganosiloxane obtained in the second step. Production method.

(In general formula (2), R ⁹ is a hydrocarbyl group, A ¹ is a group capable of reacting with a reactive residue produced by the reaction of a polybutadiene chain having an active end with a polyorganosiloxane, and A ² is a group containing a nitrogen atom, p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, p+q+r=4.) The method for producing polybutadiene rubber according to claim 3, wherein A ¹ in the general formula (2) is a group represented by -OR ¹⁰ (R ¹⁰ is a hydrogen atom or a hydrocarbyl group). The production of polybutadiene rubber according to claim 3 or 4, wherein A ² in the general formula (2) is a group containing a primary amino group having an active hydrogen atom and/or a secondary amino group having an active hydrogen atom. Method. The first step is
In an inert solvent, isoprene or a monomer containing isoprene and an aromatic vinyl compound is polymerized using a polymerization initiator to obtain 80 to 100% by weight of isoprene monomer units and 0 to 0 to 100% by weight of aromatic vinyl monomer units. forming a polymer block (A) having an active end containing 20% by weight;
The polymer block (A) having an active end and a monomer containing 1,3-butadiene are mixed to continue the polymerization reaction, and the polymer block (A) containing 1,3-butadiene monomer units is 95% by weight or more. and forming a polymer block (B) having an active end in a continuous manner with the polymer block (A) to obtain a polybutadiene chain having an active end. A method for producing polybutadiene rubber. A step of obtaining butadiene rubber by the production method according to any one of claims 1 to 6, and adding 10 to 120 parts by weight of silica to 100 parts by weight of the rubber component containing the polybutadiene rubber in a proportion of 15 to 50% by weight. A method for producing a rubber composition , comprising the step of mixing parts by weight. The method for producing a rubber composition according to claim 7 , further comprising adding a crosslinking agent. A method for producing a crosslinked rubber product, which comprises obtaining a rubber composition by the production method according to claim 8 and crosslinking the obtained rubber composition . A method for producing a tire, comprising obtaining a rubber composition by the production method according to claim 8 and crosslinking the obtained rubber composition to produce a tire containing a rubber crosslinked product of the rubber composition.

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