WO2016039004A1 - Polybutadiene and rubber composition - Google Patents

Abstract

One embodiment of the present invention relates to a polybutadiene which is characterized by having: a ratio of the 5% toluene solution viscosity (Tcp) as measured at 25°C to the Mooney viscosity (ML₁₊₄) at 100°C, namely (Tcp/ML₁₊₄) of from 1.3 to 5.0 (inclusive); a molecular weight distribution (Mw/Mn) of 2.0 or more but less than 4; and a cold flow rate (CF) of 5.5 mg/min or less.

Description

Polybutadiene and rubber composition

The present invention relates to polybutadiene. The present invention also relates to a rubber composition containing this polybutadiene and a tire rubber composition.

Polybutadiene has a so-called microstructure that includes a bond portion (1,4-structure) formed by polymerization at the 1,4-position and a bond portion (1,2-structure) formed by polymerization at the 1,2-position. Coexist in the molecular chain. The 1,4-structure is further divided into two types, a cis structure and a trans structure. On the other hand, the 1,2-structure is a structure having a vinyl group as a side chain. It is known that polybutadienes having different microstructures are produced by a polymerization catalyst, and they are used in various applications depending on their properties.

In particular, polybutadiene having a high molecular linearity (linearity), that is, having a small degree of branching, has excellent characteristics in terms of wear resistance, low heat generation, and rebound resilience. As an index of linearity, Tcp / ML _{1 + 4,} which is a ratio of a 5% toluene solution viscosity (Tcp) measured at 25 ° C. and a Mooney viscosity (ML _{1 + 4} ) at 100 ° C., is conventionally used. Tcp indicates the degree of molecular entanglement in the concentrated solution, and it is considered that the greater the Tcp / ML _{1 + 4} , the smaller the degree of branching and the greater the linearity (linearity).

However, polybutadiene having such a large Tcp / ML _{1 + 4 and} a high molecular linearity (ie, a low degree of branching) exhibits a relatively high cold flow property and a relatively low storage stability. Problems may arise during storage and transport.

As methods for improving cold flow, Patent Documents 1 to 3 describe that a specific compound (modifier) is reacted with a conjugated diene polymer obtained by polymerizing a conjugated diene compound such as polybutadiene (modification). Discloses a method for improving cold flow characteristics (ie, reducing cold flow).

Patent Document 4 discloses a modified polybutadiene obtained by modifying a raw material polybutadiene having specific characteristics in the presence of a transition metal catalyst as a polybutadiene having improved cold flow characteristics.

Further, in Patent Document 5, silica is used as a polymer composition such as polybutadiene that does not require a modification step and can be manufactured at low cost and has improved cold flow resistance (that is, cold flow is suppressed). A polymer composition is disclosed that is dispersed in a polymer (existing in a highly dispersed state) at a content of more than 0 part by weight and not more than 5 parts by weight with respect to 100 parts by weight of the polymer.

JP 2001-114817 A JP 2001-139633 A JP 2009-120757 A JP 2002-302512 A JP 2014-1315 A

An object of the present invention is to provide a polybutadiene having a comparatively large Tcp / ML _{1 + 4} which is an index of molecular linearity (linearity) and excellent in cold flow characteristics.
Another object of the present invention is to provide a polybutadiene having excellent properties possessed by a polybutadiene having a low degree of branching, for example, excellent wear resistance, low heat build-up, rebound resilience, and excellent cold flow properties. To do.

The present invention relates to the following matters.
1. The ratio (Tcp / ML _{1 + 4} ) of 5% toluene solution viscosity (Tcp) measured at 25 ° C. and Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is 1.3 or more and 5.0 or less,
The molecular weight distribution (Mw / Mn) is 2.0 or more and less than 4,
A polybutadiene having a cold flow rate (CF) of 5.5 mg / min or less.
2. 2. The polybutadiene according to item 1, wherein the Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is 25 or more and 60 or less.

3. The number of long chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of hydrogenated polybutadiene (provided that the long chain branch points are formed from two or more butadiene units). Is a branch point where a branched chain having 6 or more carbon atoms is bonded to the main chain.) Is 9 or less,
Concentration-converted G ″ and concentration-converted G ′ obtained from measurement of the angular frequency dependence of the storage elastic modulus G ′ and the loss elastic modulus G ″ of a liquid paraffin 50% by mass and 10% by mass solution X = Y ratio G ′ / C ² = 20,000 Pa when Y = G ′ / C ² (where C represents the solution concentration) [Y _(50%) / Y _{(10% ) (where, Y (50%)} is the value found from the measured values of liquid paraffin 50 wt% _{solution, Y (10%)} is a value determined from the measured values of the liquid paraffin 10 wt% solution.)] is, Polybutadiene characterized by being greater than 2.

4). The number of long chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of hydrogenated polybutadiene (provided that the long chain branch points are formed from two or more butadiene units). Is a branch point where a branched chain having 6 or more carbon atoms is bonded to the main chain.) Is 9 or less,
A polybutadiene having a cold flow rate (CF) of 5.5 mg / min or less.

5. The ratio (Tcp / ML _{1 + 4} ) of 5% toluene solution viscosity (Tcp) measured at 25 ° C. to Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is 1.3 or more,
Concentration-converted G ″ and concentration-converted G ′ obtained from measurement of the angular frequency dependence of the storage elastic modulus G ′ and the loss elastic modulus G ″ of a liquid paraffin 50% by mass and 10% by mass solution X = Y ratio G ′ / C ² = 20,000 Pa when Y = G ′ / C ² (where C represents the solution concentration) [Y _(50%) / Y _{(10% ) (where, Y (50%)} is the value found from the measured values of liquid paraffin 50 wt% _{solution, Y (10%)} is a value determined from the measured values of the liquid paraffin 10 wt% solution.)] is, Polybutadiene characterized by being greater than 2.

6). Item 6. The polybutadiene according to any one of Items 1 to 5, wherein the cis-1,4-structure content is 90% or more.

7). A rubber composition comprising the polybutadiene according to any one of items 1 to 6.
8). A tire rubber composition comprising the polybutadiene according to any one of items 1 to 6.
9. Item 9. The rubber composition for tires according to Item 8, comprising a diene polymer other than polybutadiene and a rubber reinforcing agent.
10. Item 10. The tire rubber composition according to Item 9, wherein the diene polymer is at least one of natural rubber, styrene-butadiene rubber, and polyisoprene.
11. Item 11. The tire rubber composition according to Item 9 or 10, wherein the rubber reinforcing agent is carbon black and / or silica.
12 12. A tire comprising the rubber composition for tire according to any one of items 8 to 11 as a rubber base material.

According to the present invention, it is possible to provide a polybutadiene having a relatively large Tcp / ML _{1 + 4} that is an index of molecular linearity (linearity) and having excellent cold flow characteristics. In addition, according to the present invention, it is possible to provide a polybutadiene having excellent properties of a polybutadiene having a low degree of branching, for example, excellent wear resistance, low heat generation, rebound resilience, and excellent cold flow properties. it can. The polybutadiene of the present invention is excellent in wear resistance, low heat build-up, rebound resilience, and the like, and is also excellent in cold flow characteristics, so that it can be suitably used for rubber compositions, particularly tire rubber compositions.

<Polybutadiene of the first aspect of the present invention>
The polybutadiene of the first aspect of the present invention is
The ratio (Tcp / ML _{1 + 4} ) of 5% toluene solution viscosity (Tcp) measured at 25 ° C. and Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is 1.3 or more and 5.0 or less,
The molecular weight distribution (Mw / Mn) is 2.0 or more and less than 4,
The cold flow rate (CF) is 5.5 mg / min or less.

As described above, Tcp / ML _{1 + 4,} which is a ratio of 5% toluene solution viscosity (Tcp) measured at 25 ° C. and Mooney viscosity (ML _{1 + 4} ) at 100 ° C., is conventionally used as an index of linearity. It is considered that the larger / ML _{1 + 4, the} smaller the degree of branching and the greater the linearity (linearity). The polybutadiene of the first aspect of the present invention is an unmodified unmodified polybutadiene, but has a relatively large Tcp / ML _{1 + 4} of 1.3 or more and a cold flow rate (CF) of 5.5 mg / min. The following is small. Such a polybutadiene has not existed in the past, and can be obtained by performing polymerization using a specific catalyst, as will be described later.

The Tcp / ML _{1 + 4} of the polybutadiene according to the first aspect of the present invention is 1.3 or more, preferably 1.5 or more, and particularly preferably 1.7 or more. Further, Tcp / ML _{1 + 4} of the polybutadiene of the first aspect of the present invention is 5.0 or less, preferably 4.0 or less, more preferably 3.5 or less, and particularly preferably 3.0. It is as follows.

The cold flow rate (CF) of the polybutadiene of the first aspect of the present invention is 5.5 mg / min or less, preferably 5.0 mg / min or less, more preferably 4.8 mg / min or less, Especially preferably, it is 4.6 mg / min or less.

The molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn), of the polybutadiene of the first aspect of the present invention is 2.0 or more, preferably 2.3 or more. Yes, particularly preferably 2.5 or more. Further, the molecular weight distribution (Mw / Mn) of the polybutadiene of the first aspect of the present invention is less than 4, preferably 3.8 or less, more preferably 3.5 or less, and particularly preferably 3. 2 or less.

The polybutadiene of the first aspect of the present invention satisfying the physical property values as described above has excellent properties such as wear resistance, low heat build-up, and rebound resilience, and also has excellent cold flow properties, that is, storage (storage). Excellent stability.

The Mooney viscosity (ML _{1 + 4} ) at 100 ° C. of the polybutadiene of the first aspect of the present invention is preferably 25 or more and 60 or less. The ML _{1 + 4} of the polybutadiene of the first aspect of the present invention is more preferably 30 or more, and particularly preferably 35 or more. In addition, ML _{1 + 4} of the polybutadiene of the first aspect of the present invention is more preferably 57 or less, and particularly preferably 55 or less.

The number average molecular weight (Mn) of the polybutadiene according to the first aspect of the present invention is not particularly limited, but is preferably 50,000 or more and 300,000 or less, more preferably 100,000 or more and 250,000 or less. The weight average molecular weight (Mw) of the polybutadiene of the first aspect of the present invention is not particularly limited, but is preferably 300000 or more and 700000 or less, more preferably 350,000 or more and 600000 or less.

The polybutadiene of the first aspect of the present invention preferably has a cis-1,4-structure content of 90% or more. The cis-1,4-structure content of the polybutadiene according to the first aspect of the present invention is more preferably 92% or more, more preferably 93% or more, still more preferably 94% or more, and further preferably 94.5% or more. Particularly preferred is 95% or more or more than 95%.

Further, the intrinsic viscosity (intrinsic viscosity measured at 25 ° C. in toluene) [η] of the polybutadiene according to the first aspect of the present invention is not particularly limited, but is preferably 0.1 to 10, more preferably 1 to 7. Particularly preferably, it can be controlled to 1.2 to 5.

The polybutadiene of the first aspect of the present invention may be a copolymer, and in addition to the butadiene monomer, isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethylbutadiene, Conjugated dienes such as 2-methylpentadiene, 4-methylpentadiene, 2,4-hexadiene, ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 4-methyl-1-pentene, 1-hexene, Acyclic monoolefins such as 1-octene, cyclic monoolefins such as cyclopentene, cyclohexene and norbornene, and / or aromatic vinyl compounds such as styrene and α-methylstyrene, dicyclopentadiene, 5-ethylidene-2-norbornene, Other monomers such as non-conjugated diolefins such as 1,5-hexadiene Small amount (e.g., in an amount of 10 mol% or less) may be copolymerized using.

The polybutadiene of the first aspect of the present invention has excellent characteristics and is excellent in storage (storage) stability, and therefore can be suitably used for various applications, for example, rubber applications, particularly tires. It can be suitably used for a rubber composition. The rubber composition for tires containing the polybutadiene of the first aspect of the present invention can be suitably used particularly for low fuel consumption tires. The rubber composition containing the polybutadiene of the first aspect of the present invention can be suitably used for rubber belts, rubber crawlers, golf balls, footwear, fenders and the like.

<Polybutadiene of the Second Aspect of the Present Invention>
The polybutadiene of the second aspect of the present invention is
The number of long chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of hydrogenated polybutadiene (provided that the long chain branch points are formed from two or more butadiene units). Is a branch point where a branched chain having 6 or more carbon atoms is bonded to the main chain.) Is 9 or less,
Concentration-converted G ″ and concentration-converted G ′ obtained from measurement of the angular frequency dependence of the storage elastic modulus G ′ and the loss elastic modulus G ″ of a liquid paraffin 50% by mass and 10% by mass solution X = Y ratio G ′ / C ² = 20,000 Pa when Y = G ′ / C ² (where C represents the solution concentration) [Y _(50%) / Y _{(10% ) (where, Y (50%)} is the value found from the measured values of liquid paraffin 50 wt% _{solution, Y (10%)} is a value determined from the measured values of the liquid paraffin 10 wt% solution.)] is, Greater than 2.

Here, the above Y _(50%) / Y _(10%) is an index of molecular linearity (linearity). When the degree of branching of polybutadiene is small and the linearity is high, the difference between Y _(50%) and Y _(10%) is small, that is, Y _(50%) / Y _(10%) is close to 1, and the degree of branching is large. If linearity is low, Y _(50%) / Y _(10%) increases.

In the polybutadiene of the second aspect of the present invention, Y _(50%) / Y _(10%) is larger than 2, while the number of long chain branching points is 9 or less and small. Such a polybutadiene has not existed in the past, and can be obtained by performing polymerization using a specific catalyst, as will be described later.

The polybutadiene according to the second aspect of the present invention that satisfies the physical property values as described above has excellent properties such as wear resistance, low heat build-up, and rebound resilience, and also has excellent cold flow properties, that is, storage ( Storage) Excellent stability.

The number of long-chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of the polybutadiene of the second aspect of the present invention is 9 or less, preferably 8 or less. Further, the number of long chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of the polybutadiene of the second aspect of the present invention is not particularly limited, but is preferably 2 or more. The method for obtaining the number of long chain branch points will be specifically described in Examples.

Concentration-converted G ″ obtained from measurement of the angular frequency dependence of the storage elastic modulus G ′ and loss elastic modulus G ″ of the liquid paraffin 50% by mass and 10% by mass solution of polybutadiene of the second aspect of the present invention. The ratio of Y defined as Y = G ′ / C ² (where C represents the solution concentration) when X = G ″ / C ² = 20,000 Pa with respect to the concentration conversion G ′ [Y _{( 50%)} / Y _(10%) ] is larger than 2, preferably 2.3 or more, particularly preferably 2.5 or more. Further, Y _(50%) / Y _(10%) of the polybutadiene of the second aspect of the present invention is not particularly limited, but is preferably 4.5 or less, more preferably 4.0 or less, particularly Preferably it is 3.8 or less. The method for obtaining Y _(50%) / Y _(10%) will be specifically described in the examples.

The cold flow rate (CF) of the polybutadiene of the second aspect of the present invention is not particularly limited, but is preferably 5.5 mg / min or less, more preferably 5.0 mg / min or less, more preferably 4 0.8 mg / min or less, particularly preferably 4.6 mg / min or less.

The number average molecular weight (Mn) of the polybutadiene of the second aspect of the present invention is not particularly limited, but is preferably 50,000 or more and 300,000 or less, more preferably 100,000 or more and 250,000 or less. The weight average molecular weight (Mw) of the polybutadiene of the second aspect of the present invention is not particularly limited, but is preferably 300000 or more and 700000 or less, more preferably 350,000 or more and 600000 or less.

The molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), of the polybutadiene of the second aspect of the present invention is preferably 2.0 or more, more preferably 2. 3 or more, particularly preferably 2.5 or more. The molecular weight distribution (Mw / Mn) of the polybutadiene according to the second aspect of the present invention is preferably less than 4, more preferably 3.8 or less, more preferably 3.5 or less, particularly preferably. Is 3.2 or less.

The Mooney viscosity (ML _{1 + 4} ) at 100 ° C. of the polybutadiene of the second aspect of the present invention is preferably 25 or more and 60 or less. The ML _{1 + 4} of the polybutadiene of the second aspect of the present invention is more preferably 30 or more, and particularly preferably 35 or more. Moreover, ML _{1 + 4} of the polybutadiene of the second aspect of the present invention is more preferably 57 or less, and particularly preferably 55 or less.

The Tcp / ML _{1 + 4} of the polybutadiene of the second aspect of the present invention is preferably 1.3 or more, more preferably 1.5 or more, and particularly preferably 1.7 or more. Further, Tcp / ML _{1 + 4} of the polybutadiene of the second aspect of the present invention is preferably 5.0 or less, more preferably 4.0 or less, more preferably 3.5 or less, and particularly preferably 3.0 or less.

The polybutadiene of the second aspect of the present invention preferably has a cis-1,4-structure content of 90% or more. The cis-1,4-structure content of the polybutadiene according to the second aspect of the present invention is more preferably 92% or more, more preferably 93% or more, still more preferably 94% or more, and further preferably 94.5% or more. Particularly preferred is 95% or more or more than 95%.

Further, the intrinsic viscosity (intrinsic viscosity measured at 25 ° C. in toluene) [η] of the polybutadiene according to the second aspect of the present invention is not particularly limited, but is preferably 0.1 to 10, more preferably 1 to 7. Particularly preferably, it can be controlled to 1.2 to 5.

The polybutadiene of the second aspect of the present invention may be a copolymer, and in addition to the butadiene monomer, isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethylbutadiene, Conjugated dienes such as 2-methylpentadiene, 4-methylpentadiene, 2,4-hexadiene, ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 4-methyl-1-pentene, 1-hexene, Acyclic monoolefins such as 1-octene, cyclic monoolefins such as cyclopentene, cyclohexene and norbornene, and / or aromatic vinyl compounds such as styrene and α-methylstyrene, dicyclopentadiene, 5-ethylidene-2-norbornene, Other monomers such as non-conjugated diolefins such as 1,5-hexadiene Small amount (e.g., in an amount of 10 mol% or less) may be copolymerized using.

The polybutadiene of the second aspect of the present invention has excellent characteristics and is excellent in storage (storage) stability, and therefore can be suitably used for various applications, such as rubber applications, particularly tires. It can be suitably used for a rubber composition. The rubber composition for tires containing the polybutadiene of the second aspect of the present invention can be suitably used particularly for low fuel consumption tires. The rubber composition containing the polybutadiene of the second aspect of the present invention can be suitably used for rubber belts, rubber crawlers, golf balls, footwear, fenders and the like.

<Polybutadiene of the third aspect of the present invention>
The polybutadiene of the third aspect of the present invention is
The number of long chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of hydrogenated polybutadiene (provided that the long chain branch points are formed from two or more butadiene units). Is a branch point where a branched chain having 6 or more carbon atoms is bonded to the main chain.) Is 9 or less,
The cold flow rate (CF) is 5.5 mg / min or less.

As described above, Tcp / ML _{1 + 4,} which is a ratio of 5% toluene solution viscosity (Tcp) measured at 25 ° C. and Mooney viscosity (ML _{1 + 4} ) at 100 ° C., as an index of molecular linearity (linearity). However, polybutadiene, which has a large Tcp / ML _{1 + 4} , that is, a low degree of branching and high linearity, tended to exhibit a relatively high cold flow.

The polybutadiene of the third aspect of the present invention has a small number of long-chain branching points of 9 or less and a cold flow rate (CF) as small as 5.5 mg / min or less. Such a polybutadiene has not existed in the past, and can be obtained by performing polymerization using a specific catalyst, as will be described later.

The polybutadiene according to the third aspect of the present invention satisfying the physical property values as described above has excellent properties such as wear resistance, low heat build-up, and rebound resilience, and also has excellent cold flow properties, that is, storage ( Storage) Excellent stability.

The number of long-chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of the polybutadiene of the third aspect of the present invention is 9 or less, preferably 8 or less. Further, the number of long chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of the polybutadiene of the third aspect of the present invention is not particularly limited, but is preferably 2 or more.

The cold flow rate (CF) of the polybutadiene of the third aspect of the present invention is 5.5 mg / min or less, preferably 5.0 mg / min or less, more preferably 4.8 mg / min or less, Especially preferably, it is 4.6 mg / min or less.

The number average molecular weight (Mn) of the polybutadiene of the third aspect of the present invention is not particularly limited, but is preferably 50,000 or more and 300,000 or less, more preferably 100,000 or more and 250,000 or less. Although the weight average molecular weight (Mw) of the polybutadiene of the 3rd aspect of this invention is not specifically limited, Preferably it is 300000-700000, More preferably, it is 350,000-600000.

The molecular weight distribution (Mw / Mn) which is the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polybutadiene of the third aspect of the present invention is preferably 2.0 or more, more preferably 2. 3 or more, particularly preferably 2.5 or more. Further, the molecular weight distribution (Mw / Mn) of the polybutadiene of the third aspect of the present invention is preferably less than 4, more preferably 3.8 or less, more preferably 3.5 or less, particularly preferably. Is 3.2 or less.

The Mooney viscosity (ML _{1 + 4} ) at 100 ° C. of the polybutadiene of the third aspect of the present invention is preferably 25 or more and 60 or less. The ML _{1 + 4} of the polybutadiene of the third aspect of the present invention is more preferably 30 or more, and particularly preferably 35 or more. Further, ML _{1 + 4} of the polybutadiene of the third aspect of the present invention is more preferably 57 or less, and particularly preferably 55 or less.

The Tcp / ML _{1 + 4} of the polybutadiene according to the third aspect of the present invention is preferably 1.3 or more, more preferably 1.5 or more, and particularly preferably 1.7 or more. Further, Tcp / ML _{1 + 4} of the polybutadiene of the third aspect of the present invention is preferably 5.0 or less, more preferably 4.0 or less, more preferably 3.5 or less, particularly preferably. 3.0 or less.

The polybutadiene of the third aspect of the present invention preferably has a cis-1,4-structure content of 90% or more. The cis-1,4-structure content of the polybutadiene of the third aspect of the present invention is more preferably 92% or more, more preferably 93% or more, still more preferably 94% or more, and further preferably 94.5% or more. Particularly preferred is 95% or more or more than 95%.

The intrinsic viscosity (intrinsic viscosity measured in toluene at 25 ° C.) [η] of the third aspect of the present invention is not particularly limited, but is preferably 0.1 to 10, more preferably 1 to 7. Particularly preferably, it can be controlled to 1.2 to 5.

The polybutadiene of the third aspect of the present invention may be a copolymer, and in addition to the butadiene monomer, isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethylbutadiene, Conjugated dienes such as 2-methylpentadiene, 4-methylpentadiene, 2,4-hexadiene, ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 4-methyl-1-pentene, 1-hexene, Acyclic monoolefins such as 1-octene, cyclic monoolefins such as cyclopentene, cyclohexene and norbornene, and / or aromatic vinyl compounds such as styrene and α-methylstyrene, dicyclopentadiene, 5-ethylidene-2-norbornene, Other monomers such as non-conjugated diolefins such as 1,5-hexadiene Small amount (e.g., in an amount of 10 mol% or less) may be copolymerized using.

The polybutadiene of the third aspect of the present invention has excellent characteristics and is excellent in storage (storage) stability, and therefore can be suitably used for various applications, for example, rubber applications, particularly tires. It can be suitably used for a rubber composition. The rubber composition for tires containing the polybutadiene of the third aspect of the present invention can be suitably used particularly for low fuel consumption tires. The rubber composition containing the polybutadiene of the third aspect of the present invention can be suitably used for rubber belts, rubber crawlers, golf balls, footwear, fenders and the like.

<Polybutadiene of the fourth aspect of the present invention>
The polybutadiene of the fourth aspect of the present invention is
The ratio (Tcp / ML _{1 + 4} ) of 5% toluene solution viscosity (Tcp) measured at 25 ° C. to Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is 1.3 or more,
Concentration-converted G ″ and concentration-converted G ′ obtained from measurement of the angular frequency dependence of the storage elastic modulus G ′ and the loss elastic modulus G ″ of a liquid paraffin 50% by mass and 10% by mass solution X = Y ratio G ′ / C ² = 20,000 Pa when Y = G ′ / C ² (where C represents the solution concentration) [Y _(50%) / Y _{(10% ) (where, Y (50%)} is the value found from the measured values of liquid paraffin 50 wt% _{solution, Y (10%)} is a value determined from the measured values of the liquid paraffin 10 wt% solution.)] is, Greater than 2.

Here, the above Y _(50%) / Y _(10%) is an index of molecular linearity (linearity). When the degree of branching of polybutadiene is small and the linearity is high, the difference between Y _(50%) and Y _(10%) is small, that is, Y _(50%) / Y _(10%) is close to 1, and the degree of branching is large. If linearity is low, Y _(50%) / Y _(10%) increases.

On the other hand, as described above, as an index of molecular linearity (linearity), conventionally, the ratio of the 5% toluene solution viscosity (Tcp) measured at 25 ° C. to the Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is Tcp / ML _{1 + 4} is used, and it is considered that the greater the Tcp / ML _{1 + 4} , the smaller the degree of branching and the higher the linearity.

The polybutadiene of the fourth aspect of the present invention has a high Tcp / ML _{1 + 4} of 1.3 or more (that is, a low degree of branching and high linearity), while Y _(50%) / Y _(10%) Is greater than 2 (ie, indicates a high degree of branching and low linearity). Such a polybutadiene has not existed in the past, and can be obtained by performing polymerization using a specific catalyst, as will be described later.

The polybutadiene according to the fourth aspect of the present invention satisfying the physical property values as described above has excellent properties such as abrasion resistance, low heat build-up, and rebound resilience, and also has excellent cold flow properties, that is, storage ( Storage) Excellent stability.

The Tcp / ML _{1 + 4} of the polybutadiene according to the fourth aspect of the present invention is 1.3 or more, preferably 1.5 or more, and particularly preferably 1.7 or more. The Tcp / ML _{1 + 4} of the polybutadiene of the fourth aspect of the present invention is preferably 5.0 or less, more preferably 4.0 or less, more preferably 3.5 or less, and particularly preferably 3.0 or less.

Concentration-converted G ″ obtained from measurement of the angular frequency dependence of the storage elastic modulus G ′ and loss elastic modulus G ″ of the liquid paraffin 50% by mass and 10% by mass solution of polybutadiene of the fourth aspect of the present invention. The ratio of Y defined as Y = G ′ / C ² (where C represents the solution concentration) when X = G ″ / C ² = 20,000 Pa with respect to the concentration conversion G ′ [Y _{( 50%)} / Y _(10%) ] is larger than 2, preferably 2.3 or more, particularly preferably 2.5 or more. Further, Y _(50%) / Y _(10%) of the polybutadiene of the fourth aspect of the present invention is not particularly limited, but is preferably 4.5 or less, more preferably 4.0 or less, particularly Preferably it is 3.8 or less.

The cold flow rate (CF) of the polybutadiene of the fourth aspect of the present invention is not particularly limited, but is preferably 5.5 mg / min or less, more preferably 5.0 mg / min or less, more preferably 4 0.8 mg / min or less, particularly preferably 4.6 mg / min or less.

The number average molecular weight (Mn) of the polybutadiene according to the fourth aspect of the present invention is not particularly limited, but is preferably 50,000 or more and 300,000 or less, more preferably 100,000 or more and 250,000 or less. Although the weight average molecular weight (Mw) of the polybutadiene of the 4th aspect of this invention is not specifically limited, Preferably it is 300000 or more and 700000 or less, More preferably, it is 350,000 or more and 600000 or less.

The molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn), of the polybutadiene of the fourth aspect of the present invention is preferably 2.0 or more, more preferably 2. 3 or more, particularly preferably 2.5 or more. The molecular weight distribution (Mw / Mn) of the polybutadiene according to the fourth aspect of the present invention is preferably less than 4, more preferably 3.8 or less, more preferably 3.5 or less, particularly preferably. Is 3.2 or less.

The Mooney viscosity (ML _{1 + 4} ) at 100 ° C. of the polybutadiene of the fourth aspect of the present invention is preferably 25 or more and 60 or less. The ML _{1 + 4} of the polybutadiene of the fourth aspect of the present invention is more preferably 30 or more, and particularly preferably 35 or more. Moreover, ML _{1 + 4} of the polybutadiene of the fourth aspect of the present invention is more preferably 57 or less, and particularly preferably 55 or less.

The polybutadiene of the fourth aspect of the present invention preferably has a cis-1,4-structure content of 90% or more. The cis-1,4-structure content of the polybutadiene according to the fourth aspect of the present invention is more preferably 92% or more, more preferably 93% or more, still more preferably 94% or more, and further preferably 94.5% or more. Particularly preferred is 95% or more or more than 95%.

Further, the intrinsic viscosity (intrinsic viscosity measured at 25 ° C. in toluene) [η] of the polybutadiene according to the fourth aspect of the present invention is not particularly limited, but is preferably 0.1 to 10, more preferably 1 to 7. Particularly preferably, it can be controlled to 1.2 to 5.

The polybutadiene of the fourth aspect of the present invention may be a copolymer, and in addition to the butadiene monomer, isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethylbutadiene, Conjugated dienes such as 2-methylpentadiene, 4-methylpentadiene, 2,4-hexadiene, ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 4-methyl-1-pentene, 1-hexene, Acyclic monoolefins such as 1-octene, cyclic monoolefins such as cyclopentene, cyclohexene and norbornene, and / or aromatic vinyl compounds such as styrene and α-methylstyrene, dicyclopentadiene, 5-ethylidene-2-norbornene, Other monomers such as non-conjugated diolefins such as 1,5-hexadiene Small amount (e.g., in an amount of 10 mol% or less) may be copolymerized using.

The polybutadiene of the fourth aspect of the present invention has excellent characteristics and is excellent in storage (storage) stability, and therefore can be suitably used for various applications, for example, rubber applications, particularly tires. It can be suitably used for a rubber composition. The rubber composition for tires containing the polybutadiene of the fourth aspect of the present invention can be suitably used particularly for low fuel consumption tires. The rubber composition containing the polybutadiene of the fourth aspect of the present invention can be suitably used for rubber belts, rubber crawlers, golf balls, footwear, fenders, and the like.

<Method for producing polybutadiene>
The polybutadiene of the first aspect, the second aspect, the third aspect, and the fourth aspect of the present invention (hereinafter referred to as “polybutadiene of the present invention”) can be produced, for example, as follows. . However, the polybutadiene of the present invention is not limited to those produced by the following production method.

As a catalyst for polybutadiene polymerization, a nonmetallocene metal compound (A) represented by the following general formula (1), an ionic compound comprising a non-coordinating anion and a cation, or an alumoxane (B), and a periodic table An organometallic compound (C) of an element selected from Group 2, Group 12, and Group 13 is preferably used.

（但し、Ｒ^１、Ｒ^２、Ｒ^３はそれぞれ、水素又は炭素数１～１２の置換基を表す。Ｏは酸素原子を表し、ＭはＧｄ（ガドリニウム原子）、Ｔｂ（テルビウム原子）、Ｄｙ（ジスプロシウム原子）、Ｈｏ（ホルミウム原子）、Ｅｒ（エルビウム原子）、又はＴｍ（ツリウム原子）を表す。）

(However, R ¹ , R ² and R ³ each represent hydrogen or a substituent having 1 to 12 carbon atoms. O represents an oxygen atom, M represents Gd (gadolinium atom), Tb (terbium atom), Dy ( Dysprosium atom), Ho (holmium atom), Er (erbium atom), or Tm (thulium atom).

Specific examples of the substituent having 1 to 12 carbon atoms in R ¹ to R ³ of the general formula (1) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, Isobutyl, t-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl Group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, saturated hydrocarbon group such as dodecyl group, unsaturated hydrocarbon group such as vinyl group, 1-propenyl group, and allyl group, cyclohexyl Group, alicyclic hydrocarbon group such as methylcyclohexyl group, and ethylcyclohexyl group, and phenyl group, benzyl group, toluyl group, phenethyl group, etc. And aromatic hydrocarbon groups. Furthermore, those in which a hydroxyl group, a carboxyl group, a carbomethoxy group, a carboethoxy group, an amide group, an amino group, an alkoxy group, a phenoxy group and the like are substituted at an arbitrary position are also included. Of these, a saturated hydrocarbon group having 1 to 12 carbon atoms is preferable, and a saturated hydrocarbon group having 1 to 6 carbon atoms is particularly preferable.

R ¹ to R ^{3 in} the general formula (1) are as follows: R ² is hydrogen or a substituent having 1 to 12 carbon atoms (preferably a saturated hydrocarbon group), and R ¹ and R ³ are substituents having 1 to 12 carbon atoms ( A saturated hydrocarbon group is preferred. In particular, R ² is hydrogen or a substituent having 1 to 6 carbon atoms (preferably a saturated hydrocarbon group), and R ¹ and R ³ are each a substituent having 1 to 6 carbon atoms (preferably a saturated hydrocarbon group). preferable.

Specific examples of the nonmetallocene metal compound (A) of the general formula (1) in which M is Gd (gadolinium atom) include tris (2,2,6,6-tetramethyl-3,5-heptanedionato) gadolinium, Tris (2,6,6-trimethyl-3,5-heptanedionato) gadolinium, tris (2,6-dimethyl-3,5-heptanedionato) gadolinium, tris (3,5-heptanedionato) gadolinium, tris (2,4- Pentandionato) gadolinium, tris (2,4-hexanedionate) gadolinium, tris (1,5-dicyclopentyl-2,4-pentandionato) gadolinium, tris (1,5-dicyclohexyl-2,4-pentane) (Dionato) gadolinium and the like.

Among them, preferably, tris (2,2,6,6-tetramethyl-3,5-heptanedionato) gadolinium, tris (2,6-dimethyl-3,5-heptanedionato) gadolinium, tris (2,4-pentanedioated) Nato) gadolinium and the like. Particularly preferred are tris (2,2,6,6-tetramethyl-3,5-heptanedionato) gadolinium and tris (2,6-dimethyl-3,5-heptanedionato) gadolinium.

Specific examples of the nonmetallocene metal compound (A) of the general formula (1) in which M is Tb (terbium atom) include tris (2,2,6,6-tetramethyl-3,5-heptanedionato) terbium, Tris (2,6,6-trimethyl-3,5-heptanedionato) terbium, Tris (2,6-dimethyl-3,5-heptanedionato) terbium, Tris (3,5-heptanedionato) terbium, Tris (2,4- Pentandionato) terbium, tris (2,4-hexanedionate) terbium, tris (1,5-dicyclopentyl-2,4-pentandionato) terbium, tris (1,5-dicyclohexyl-2,4-pentane) (Dionato) terbium and the like.

Among them, preferably, tris (2,2,6,6-tetramethyl-3,5-heptanedionato) terbium, tris (2,6-dimethyl-3,5-heptanedionato) terbium, tris (2,4-pentanedioated) Nato) terbium. Particularly preferred are tris (2,2,6,6-tetramethyl-3,5-heptanedionato) terbium and tris (2,6-dimethyl-3,5-heptanedionato) terbium.

Specific examples of the nonmetallocene-type metal compound (A) of the general formula (1) in which M is Dy (dysprosium atom) include tris (2,2,6,6-tetramethyl-3,5-heptanedionato) dysprosium, Tris (2,6,6-trimethyl-3,5-heptanedionato) dysprosium, Tris (2,6-dimethyl-3,5-heptaneedionato) dysprosium, Tris (3,5-heptaneedionato) dysprosium, Tris (2,4- Pentanedionate) dysprosium, tris (2,4-hexanedionato) dysprosium, tris (1,5-dicyclopentyl-2,4-pentanedionato) dysprosium, tris (1,5-dicyclohexyl-2,4-pentane And diatoprosium).

Among them, preferably, tris (2,2,6,6-tetramethyl-3,5-heptanedionato) dysprosium, tris (2,6-dimethyl-3,5-heptaneedionato) dysprosium, tris (2,4-pentanedioe) Nato) dysprosium. Particularly preferred are tris (2,2,6,6-tetramethyl-3,5-heptanedionato) dysprosium and tris (2,6-dimethyl-3,5-heptanedionato) dysprosium.

Specific examples of the nonmetallocene metal compound (A) of the general formula (1) in which M is Ho (holmium atom) include tris (2,2,6,6-tetramethyl-3,5-heptanedionato) holmium, Tris (2,6,6-trimethyl-3,5-heptanedionato) holmium, Tris (2,6-dimethyl-3,5-heptanedionato) holmium, Tris (3,5-heptanedionato) holmium, Tris (2,4- Pentandionato) holmium, Tris (2,4-hexanedionate) holmium, Tris (1,5-dicyclopentyl-2,4-pentandionato) holmium, Tris (1,5-dicyclohexyl-2,4-pentane) And diato) holmium.

Among them, preferably, tris (2,2,6,6-tetramethyl-3,5-heptanedionato) holmium, tris (2,6-dimethyl-3,5-heptanedionato) holmium, tris (2,4-pentanedioated) Nato) holmium and the like. Particularly preferred are tris (2,2,6,6-tetramethyl-3,5-heptanedionato) holmium and tris (2,6-dimethyl-3,5-heptanedionato) holmium.

Specific examples of the nonmetallocene metal compound (A) of the general formula (1) in which M is Er (erbium atom) include tris (2,2,6,6-tetramethyl-3,5-heptanedionato) erbium, Tris (2,6,6-trimethyl-3,5-heptanedionato) erbium, Tris (2,6-dimethyl-3,5-heptanedionato) erbium, Tris (3,5-heptanedionato) erbium, Tris (2,4- Pentandionato) erbium, Tris (2,4-hexanedionate) erbium, Tris (1,5-dicyclopentyl-2,4-pentandionato) erbium, Tris (1,5-dicyclohexyl-2,4-pentane (Dionato) Erbium.

Among them, preferably, tris (2,2,6,6-tetramethyl-3,5-heptanedionato) erbium, tris (2,6-dimethyl-3,5-heptanedionato) erbium, tris (2,4-pentanedioated) Nato) Erbium. Particularly preferred are tris (2,2,6,6-tetramethyl-3,5-heptanedionato) erbium and tris (2,6-dimethyl-3,5-heptanedionato) erbium.

Specific examples of the nonmetallocene-type metal compound (A) of the general formula (1) in which M is Tm (thulium atom) include tris (2,2,6,6-tetramethyl-3,5-heptanedionato) thulium, Tris (2,6,6-trimethyl-3,5-heptanedionato) thulium, Tris (2,6-dimethyl-3,5-heptaneedionato) thulium, Tris (3,5-heptaneedionato) thulium, Tris (2,4- Pentandionato) thulium, tris (2,4-hexanedionate) thulium, tris (1,5-dicyclopentyl-2,4-pentanedionato) thulium, tris (1,5-dicyclohexyl-2,4-pentane) (Dionato) thulium and the like.

Among them, preferably, tris (2,2,6,6-tetramethyl-3,5-heptanedionato) thulium, tris (2,6-dimethyl-3,5-heptaneedionato) thulium, tris (2,4-pentanedioated) Nato) thulium. Particularly preferred are tris (2,2,6,6-tetramethyl-3,5-heptanedionato) thulium and tris (2,6-dimethyl-3,5-heptaneedionato) thulium.

The nonmetallocene metal compound (A) may be used alone or in combination of two or more.

In the ionic compound comprising the non-coordinating anion and cation as the component (B), examples of the non-coordinating anion include tetra (phenyl) borate, tetra (fluorophenyl) borate, and tetrakis (difluorophenyl). Borate, tetrakis (trifluorophenyl) borate, tetrakis (tetrafluorophenyl) borate, tetrakis (pentafluorophenyl) borate, tetrakis (3,5-bistrifluoromethylphenyl) borate, tetrakis (tetrafluoromethylphenyl) borate, tetra ( Triyl) borate, tetra (xylyl) borate, triphenyl (pentafluorophenyl) borate, tris (pentafluorophenyl) (phenyl) borate, tridecahydride-7,8-dicar Undekaboreto, tetrafluoroborate, hexafluorophosphate and the like.

On the other hand, examples of the cation include a carbonium cation, an oxonium cation, an ammonium cation, a phosphonium cation, a cycloheptatrienyl cation, and a ferrocenium cation.

Specific examples of the carbonium cation include trisubstituted carbonium cations such as a triphenylcarbonium cation and a tri-substituted phenylcarbonium cation. Specific examples of the tri-substituted phenylcarbonium cation include tri (methylphenyl) carbonium cation and tri (dimethylphenyl) carbonium cation.

Specific examples of the ammonium cation include trialkylammonium cations, triethylammonium cations, tripropylammonium cations, tri (n-butyl) ammonium cations, tri (i-butyl) ammonium cations, and the like, N, N-dimethyl N, N-dialkylanilinium cations such as anilinium cation, N, N-diethylanilinium cation, N, N-2,4,6-pentamethylanilinium cation; di (isopropyl) ammonium cation, dicyclohexylammonium cation, etc. And dialkylammonium cations.

Specific examples of phosphonium cations include triphenylphosphonium cation, tetraphenylphosphonium cation, tri (methylphenyl) phosphonium cation, tetra (methylphenyl) phosphonium cation, tri (dimethylphenyl) phosphonium cation, tetra (dimethylphenyl) phosphonium cation, etc. Of arylphosphonium cations.

As the ionic compound (B), those arbitrarily selected and combined from the non-coordinating anions and cations exemplified above can be preferably used.

Among these, as the ionic compound (B), a boron-containing compound is preferable, and among them, triphenylcarbenium tetrakis (pentafluorophenyl) borate, triphenylcarbeniumtetrakis (fluorophenyl) borate, N, N-dimethylaniline are particularly preferable. Nitrotetrakis (pentafluorophenyl) borate, 1,1′-dimethylferrocenium tetrakis (pentafluorophenyl) borate and the like are preferable. An ionic compound (B) may be used independently and may be used in combination of 2 or more type.

Also, alumoxane (aluminoxane) may be used in place of the ionic compound composed of the non-coordinating anion and cation as component (B). The alumoxane is obtained by bringing an organoaluminum compound and a condensing agent into contact with each other, and has a general formula (—Al (R ′) O—) n (R ′ is a hydrocarbon group having 1 to 10 carbon atoms). Including a partly substituted with a halogen atom and / or an alkoxy group, where n is the degree of polymerization, and is 5 or more, preferably 10 or more). . Examples of R ′ include a methyl group, an ethyl group, a propyl group, and an isobutyl group, and a methyl group is preferable. Examples of the organoaluminum compound used as a raw material for alumoxane include trialkylaluminums such as trimethylaluminum, triethylaluminum, and triisobutylaluminum, and mixtures thereof. Among these, alumoxane using a mixture of trimethylaluminum and triisobutylaluminum as a raw material can be suitably used.

Typical examples of the condensing agent used in the production of alumoxane include water, but other than that, any of the above-described organoaluminum compounds that undergo a condensation reaction, for example, adsorbed water such as inorganic substances, diols, and the like.

As the organometallic compound of an element selected from Group 2, Group 12 and Group 13 of the periodic table as the component (C), for example, organic magnesium, organic zinc, organic aluminum, and the like are used. Among these compounds, preferred are dialkylmagnesium; alkylmagnesium halides such as alkylmagnesium chloride and alkylmagnesium bromide; dialkylzinc; trialkylaluminum; dialkylaluminum chloride, dialkylaluminum bromide; alkylaluminum sesquichloride, alkylaluminum sesquibromide Organic aluminum halogen compounds such as alkylaluminum dichloride; organoaluminum hydride compounds such as dialkylaluminum hydride.

Specific compounds include alkyl magnesium halides such as methyl magnesium chloride, ethyl magnesium chloride, butyl magnesium chloride, hexyl magnesium chloride, octyl magnesium chloride, ethyl magnesium bromide, butyl magnesium bromide, butyl magnesium iodide, and hexyl magnesium iodide. Can be mentioned.

Furthermore, dialkyl magnesium such as dimethyl magnesium, diethyl magnesium, dibutyl magnesium, dihexyl magnesium, dioctyl magnesium, ethyl butyl magnesium, ethyl hexyl magnesium and the like can be mentioned.

Furthermore, dialkyl zinc such as dimethyl zinc, diethyl zinc, diisobutyl zinc, dihexyl zinc, dioctyl zinc, didecyl zinc and the like can be mentioned.

Further examples include trialkylaluminums such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, tridecylaluminum.

Furthermore, dialkylaluminum chlorides such as dimethylaluminum chloride and diethylaluminum chloride, organoaluminum halogen compounds such as ethylaluminum sesquichloride and ethylaluminum dichloride, and hydrogenated organoaluminum compounds such as diethylaluminum hydride, diisobutylaluminum hydride and ethylaluminum sesquihydride. Can be mentioned.

These organometallic compounds (C) of elements selected from Groups 2, 12, and 13 of the periodic table can be used alone or in combination of two or more.

Among them, an organometallic compound of a group 13 element is preferable, among which organic aluminum is preferable, and examples thereof include trimethylaluminum, triethylaluminum, and triisobutylaluminum. Particularly preferred is triethylaluminum.
Component (A) (nonmetallocene-type metal compound), component (B) (ionic compound comprising non-coordinating anion and cation) and component (C) (second periodic table) of the polybutadiene polymerization catalyst of the present invention The ratio of the organometallic compound of an element selected from Group 12, Group 12 and Group 13) is not particularly limited, but the amount of component (B) is 0.5 to 10 moles per mole of component (A) 1 to 5 mol is particularly preferable. The amount of component (C) is preferably 10 to 10,000 moles, and particularly preferably 50 to 7000 moles per mole of component (A).

In the present invention, polymerization can be carried out using a catalyst comprising the above-mentioned components (A), (B) and (C), but the polybutadiene obtained is within the range not impeding the effects of the present invention other than the above. The molecular weight regulator and the like can be added.

As the molecular weight regulator, a compound selected from hydrogen, a metal hydride compound, and a hydrogenated organometallic compound can be used.

Metal hydride compounds include lithium hydride, sodium hydride, potassium hydride, magnesium hydride, calcium hydride, borane, aluminum hydride, gallium hydride, silane, germane, lithium borohydride, sodium borohydride , Lithium aluminum hydride, sodium aluminum hydride and the like.

Examples of hydrogenated organometallic compounds include alkylboranes such as methylborane, ethylborane, propylborane, butylborane, and phenylborane; dialkylboranes such as dimethylborane, diethylborane, dipropylborane, dibutylborane, and diphenylborane; methylaluminum dihydride Alkyl aluminum dihydrides such as ethyl aluminum dihydride, propyl aluminum dihydride, butyl aluminum dihydride, phenyl aluminum dihydride; dimethyl aluminum hydride, diethyl aluminum hydride, dipropyl aluminum hydride, dinormal butyl aluminum hydride, diisobutyl aluminum hydride, Diphenyl aluminum hydra Dialkyl aluminum hydrides such as methyl silane, ethyl silane, propyl silane, butyl silane, phenyl silane, dimethyl silane, diethyl silane, dipropyl silane, dibutyl silane, diphenyl silane, trimethyl silane, triethyl silane, tripropyl silane, tributyl silane, triphenyl Silanes such as silane; methyl germane, ethyl germane, propyl germane, butyl germane, phenyl germane, dimethyl germane, diethyl germane, dipropyl germane, dibutyl germane, diphenyl germane, trimethyl germane, triethyl germane, tripropyl germane, tributyl germane, Examples thereof include germanes such as triphenyl germane.

Among these, diisobutylaluminum hydride and diethylaluminum hydride are preferable.

In the present invention, each catalyst component can be supported on an inorganic compound or an organic polymer compound.

In the method for producing polybutadiene of the present invention, the order of addition of the above catalyst components [components (A), (B) and (C)] is not particularly limited, and can be performed, for example, in the following order.

(1) Add component (C) in the presence or absence of monomers in an inert organic solvent, and add components (A) and (B) in any order.

(2) Add component (C) in the presence or absence of monomers in an inert organic solvent, add the molecular weight regulator described above, and then add components (A) and (B) in any order. Added.

(3) Add component (A) in the presence or absence of monomers in an inert organic solvent, add component (C) and the molecular weight regulator described above in any order, and then add component (B). Added.

(4) Add component (B) in the presence or absence of monomers in an inert organic solvent, add component (C) and the molecular weight regulator described above in any order, and then add component (A). Added.

(5) In the inert organic solvent, the component (C) is added in the presence or absence of the monomer, the component (A) and the component (B) are added in an arbitrary order, and then the molecular weight regulator described above is added. Added.

Here, the monomer added first may be the total amount of the monomer or a part thereof.

As described above, the polybutadiene of the present invention may be copolymerized using a small amount of other monomers in addition to 1,3-butadiene. Examples of monomers other than 1,3-butadiene as raw materials include isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethylbutadiene, 2-methylpentadiene, 4-methylpentadiene, 2 Conjugated dienes such as 1,4-hexadiene, acyclic monoolefins such as ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, cyclopentene , Cyclic monoolefins such as cyclohexene and norbornene, and / or aromatic vinyl compounds such as styrene and α-methylstyrene, non-conjugated diolefins such as dicyclopentadiene, 5-ethylidene-2-norbornene and 1,5-hexadiene Etc. These monomer components may be used individually by 1 type, and may be used in combination of 2 or more type.

The polymerization method is not particularly limited, and bulk polymerization (bulk polymerization) or solution polymerization using a monomer such as 1,3-butadiene as a polymerization solvent can be applied. Solvents for solution polymerization include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene, Examples thereof include olefinic hydrocarbons such as the above olefin compounds and cis-2-butene and trans-2-butene. Among them, benzene, toluene, xylene, cyclohexane, or cis-2-butene and trans-2-butene. And the like are preferably used. These solvent may be used individually by 1 type, and may be used in combination of 2 or more type.

The polymerization temperature is preferably in the range of −30 to 150 ° C., more preferably in the range of 0 to 100 ° C., and particularly preferably in the range of 10 to 80 ° C. The polymerization time is preferably 1 minute to 12 hours, more preferably 3 minutes to 5 hours, particularly preferably 5 minutes to 1 hour.
The amount of the polybutadiene polymerization catalyst of the present invention is not particularly limited, but the concentration of the component (A) (metal compound) is preferably 1 to 100 μmol / L, and preferably 2 to 50 μmol / L. It is particularly preferred.

After performing the polymerization for a predetermined time, the inside of the polymerization tank is released as necessary, and post-treatment such as washing and drying steps is performed. In this way, the polybutadiene of the present invention can be obtained.
In one embodiment, obtained by polymerizing 1,3-butadiene using a catalyst containing the nonmetallocene metal compound (A) represented by the general formula (1), wherein M is Gd (gadolinium atom). The resulting polybutadiene can be removed.

<Rubber composition (tire rubber composition)>
The polybutadiene of the present invention can be suitably used for, for example, a rubber composition, particularly a tire rubber composition.

The rubber composition of the present invention is characterized by containing one or more of the polybutadienes of the present invention.

Specifically, the polybutadiene of the present invention is blended alone or blended with other synthetic rubber or natural rubber, and if necessary, is oil-extended with process oil, and then a filler such as carbon black, a vulcanizing agent. Vulcanization accelerators and other ordinary compounding agents can be added to vulcanize the tires, hoses, belts, and other industrial products that require mechanical properties and wear resistance. it can. It can also be used as a plastic material modifier, for example, a high impact polystyrene modifier.

The tire rubber composition of the present invention comprises one or more of the polybutadienes of the present invention, the polybutadiene of the present invention (hereinafter referred to as “polybutadiene (α)”), and a diene polymer other than polybutadiene. (Hereinafter referred to as “diene polymer (β)”) and a rubber reinforcing agent (hereinafter referred to as “rubber reinforcing agent (γ)”).

The tire rubber composition includes a polybutadiene (α), a rubber component (α) + (β) composed of a diene polymer (β) other than (α), and a rubber reinforcing agent (γ). The rubber reinforcing agent (γ) is preferably contained in an amount of 30 to 80 parts by mass with respect to 100 parts by mass of the rubber component (α) + (β). That is, the blending amount of the rubber reinforcing agent (γ) is preferably based on 100 parts by mass of the rubber component (α) + (β) composed of polybutadiene (α) and a diene polymer (β) other than (α). Is 30 to 80 parts by mass, more preferably 40 to 70 parts by mass. Further, the mass ratio of the rubber component (α) + (β) of the tire rubber composition is 90 to 5 parts by mass of polybutadiene (α) and 10 to 95 parts by mass of a diene polymer (β) other than polybutadiene (α). It is preferable that

The diene polymer (β) other than polybutadiene used in the rubber composition for tires of the present invention is preferably a vulcanizable rubber. Specifically, natural rubber, ethylene propylene diene rubber (EPDM), nitrile rubber ( NBR), butyl rubber (IIR), chloroprene rubber (CR), polyisoprene, high cis polybutadiene rubber, low cis polybutadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber, chlorinated butyl rubber, brominated butyl rubber, acrylonitrile Examples thereof include butadiene rubber. In the case of a tire rubber composition, the diene polymer (β) is preferably at least one of natural rubber, styrene-butadiene rubber, and polyisoprene. These rubbers may be used alone or in combination of two or more.

Examples of the rubber reinforcing agent (γ) used in the tire rubber composition of the present invention include various types of carbon black, silica, activated calcium carbonate, ultrafine magnesium silicate, talc, mica and the like. The rubber reinforcing agent (γ) of the tire rubber composition is preferably at least one of carbon black and silica. The rubber reinforcing agent may be used alone or in combination of two or more.

In particular, when silica is used as the rubber reinforcing agent (γ), a silane coupling agent can be used as an additive. The silane coupling agent used as an additive is an organosilicon compound represented by the general formula R ⁷ _n SiR ⁸ _4-n , where R ⁷ is a vinyl group, acyl group, allyl group, allyloxy group, amino group, epoxy group, An organic group having 1 to 20 carbon atoms having a reactive group selected from a mercapto group, a chloro group, an alkyl group, a phenyl group, hydrogen, a styryl group, a methacryl group, an acrylic group, a ureido group, and the like; R ⁸ is a chloro group , An alkoxy group, an acetoxy group, an isopropenoxy group, an amino group, and the like, and n represents an integer of 1 to 3. The R ⁷ of the above silane coupling agent, those containing a vinyl group and / or a chloro group are preferable.

The addition amount of the additive silane coupling agent is preferably 0.2 to 20 parts by mass, more preferably 3 to 15 parts by mass, and particularly preferably 5 to 15 parts by mass with respect to 100 parts by mass of the filler. If it is less than the above range, it may cause scorching. Moreover, when more than said range, it may become a cause of a deterioration of a tensile characteristic and elongation.

Fullerenes as disclosed in JP-A-2006-131819 may be used as the rubber reinforcing agent (γ) blended in the tire rubber composition. Examples of fullerenes include C60, C70, a mixture of C60 and C70, and derivatives thereof. Fullerene derivatives include PCBM (Phenyl C61-butylic acid methylester), PCBNB (Phenyl C61-butyric acid n-butyester), PCBIB (PhenylC61-ButyCyclicBhicC71-BictyPc) ester) and the like. In addition, fullerene hydroxide, fullerene oxide, hydrogenated fullerene, and the like can also be used.

The rubber composition for tires according to the present invention can be obtained by kneading the above components using a conventional banbury, open roll, kneader, biaxial kneader or the like.

In the tire rubber composition according to the present invention, a vulcanizing agent, a vulcanization aid, an anti-aging agent, a filler, a process oil, zinc white, stearic acid, and the like, which are usually used in the rubber industry, if necessary. An agent may be kneaded.

As the vulcanizing agent, known vulcanizing agents such as sulfur, organic peroxides, resin vulcanizing agents, metal oxides such as magnesium oxide, and the like can be used. The vulcanizing agent is preferably blended in an amount of about 0.5 to 3 parts by mass with respect to 100 parts by mass of the rubber component (α) + (β).

As the vulcanization aid, known vulcanization aids such as aldehydes, ammonia, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates and xanthates can be used.

Anti-aging agents include amine / ketone series, imidazole series, amine series, phenol series, sulfur series and phosphorus series.

Examples of the filler include inorganic fillers such as silica, calcium carbonate, basic magnesium carbonate, clay, Lissajous, and diatomaceous earth, and organic fillers such as carbon black, recycled rubber, and powder rubber.

Process oil may be any of aromatic, naphthenic and paraffinic.

Hereinafter, the present invention will be further described with reference to examples and comparative examples. In addition, this invention is not limited to a following example.

Measured / evaluated methods such as catalyst activity, physical properties of polybutadiene and physical properties of the composition are as follows.

Catalyst activity: Polymer yield (g) per hour of polymerization time per 1 mmol of the central metal of the catalyst used in the polymerization reaction. For example, when the catalyst is a gadolinium compound, it is the polymer yield (g) per hour of polymerization time per 1 g of gadolinium metal of the gadolinium compound used in the polymerization reaction.

(Evaluation of polybutadiene)
Microstructure: Performed by infrared absorption spectrum analysis. The microstructure was calculated from the absorption intensity ratio of cis 734 cm ⁻¹ , trans 967 cm ⁻¹ and vinyl 910 cm ⁻¹ .

Number average molecular weight (Mn) and weight average molecular weight (Mw): Calibration performed from a molecular weight distribution curve obtained by GPC (manufactured by Shimadzu Corporation) at a temperature of 40 ° C. using polystyrene as a standard material and tetrahydrofuran as a solvent. The number average molecular weight and the weight average molecular weight were calculated using a line.

Molecular weight distribution: Evaluated by Mw / Mn, which is a ratio of weight average molecular weight Mw and number average molecular weight Mn obtained from GPC using polystyrene as a standard substance.

Mooney viscosity (ML _{1 + 4} , 100 ° C.): According to JIS-K6300, pre-heated at 100 ° C. for 1 minute using a Mooney viscometer manufactured by Shimadzu Corporation, and then measured for 4 minutes to determine the Mooney viscosity (ML _{1 + 4} , 100 ° C).

Toluene solution viscosity (Tcp): After 2.28 g of the obtained polybutadiene was dissolved in 50 ml of toluene, a standard solution for calibrating viscometer (JIS-Z8809) was used as a standard solution. 400 was used and measured at 25 ° C.

Cold flow rate (CF): The obtained polybutadiene is kept at 50 ° C., sucked in a glass tube having an inner diameter of 6.0 mm with a differential pressure of 325 mmHg for 10 minutes, and the weight of the sucked polymer is measured per minute. It was determined as the amount of polymer sucked (mg / min).

Measurement of the number of long chain branch points of polybutadiene:
1 g of polybutadiene prepared in 100 mL of p-xylene and 2.5 mol equivalent of p-toluenesulfonyl hydrazide (p-TSH: hydrogen generator) were added and reacted at 150 ° C. for 5 hours. Then, hydrogenated polybutadiene was obtained through the steps of hot filtration, reprecipitation (poor solvent: methanol), and washing (cleaning medium: ethanol). The hydrogenation reaction was confirmed using FT-IR and ¹ H-NMR to confirm the progress of the reaction.

Polybutadiene is converted to polyethylene by hydrogenation while maintaining its branched structure, with long chain branching (branched chain having 6 or more carbon atoms) and short chain branching (ethyl group) derived from the vinyl-1,2 structure. The Here, the cis-1,4, trans-1,4, vinyl-1,2 structure contained in polybutadiene and the structure after hydrogenation are shown.

　得られた水素化ポリブタジエン７０ｍｇをＮＭＲ測定管にサンプリングし、ＯＤＣＢ（オルトジクロロベンゼン）／Ｃ_６Ｄ_６（４／１（体積比））を０．７ｍＬ添加した後、封管した。その後、ヒーティングブロックとヒートガンを用いて、試料を加熱溶解することにより均一化し、^１３Ｃ－ＮＭＲ測定に供した。

70 mg of the obtained hydrogenated polybutadiene was sampled into an NMR measuring tube, 0.7 mL of ODCB (orthodichlorobenzene) / C ₆ D ₆ (4/1 (volume ratio)) was added, and the tube was sealed. Thereafter, the sample was homogenized by heating and dissolving using a heating block and a heat gun, and subjected to ¹³ C-NMR measurement.

¹³ C-NMR measurement was performed using EX-400 manufactured by JEOL Ltd.

First, in order to determine the short chain branching point (vinyl content), ¹³ C-NMR (normal single pulse) measurement was performed at a measurement temperature of 130 ° C. and an integration number of 54,000 times.

In this normal ¹³ C-NMR measurement, the long chain branching point present in a small amount in the polymer cannot be quantified due to the dynamic range caused by the main chain methylene peak. The short chain branch point based on can be quantified sufficiently. That is, the quantitative relationship between the number of methylene carbons and the number of methine carbons can be obtained from the ratio of the peak area of the short chain branching point methine carbon peak to the peak area of the main chain methylene carbon peak. The number of branch points (number of short chain branch points / 10,000 monomer units) can be determined.

The main peaks of ¹³ C-NMR (single pulse) spectra of hydrogenated polybutadiene and their chemical shifts are shown in the following table. The chemical shift is a value based on TMS (tetramethylsilane).

　主鎖メチレンのピーク面積Ｓ_Ｍ＝ピーク群［Ｍ１，Ｍ２，Ｍ３］のピーク面積の和、
　短鎖分岐点メチンのピーク面積Ｓ_Ｂ＝ピーク［Ｂ１］のピーク面積、としたとき、
ｃｉｓ－１，４構造およびｔｒａｎｓ－１，４構造に基づくメチレン炭素数は、Ｓ_Ｍ－Ｓ_Ｂ（に比例する数）となり、ｃｉｓ－１，４構造およびｔｒａｎｓ－１，４構造のモノマーユニット数は、（Ｓ_Ｍ－Ｓ_Ｂ）／４（に比例する数）となる。
ｖｉｎｙｌ－１，２構造のモノマーユニット数、即ち短鎖分岐点の数は、Ｓ_Ｂ（に比例する数）となる。

Peak area S _M of main chain methylene = sum of peak areas of peak group [M1, M2, M3],
When the peak area S _B of the short chain branching point methine is the peak area of the peak [B1],
The number of methylene carbons based on the cis-1,4 structure and the trans-1,4 structure is S _M -S _B (number proportional to), and the number of monomer units of the cis-1,4 structure and the trans-1,4 structure Is (S _M −S _B ) / 4 (a number proportional to).
The number of monomer units having the vinyl-1,2 structure, that is, the number of short chain branch points, is S _B (number proportional to).

Therefore, the number of short chain branch points per butadiene monomer unit (number of short chain branch points / 1 monomer unit) is
S _B / [(S _M −S _B ) / 4 + S _B ] × 100 (mol%) (1)
Can be calculated as

Subsequently, ¹³ C-NMR DEPT 90 ° measurement was performed at a measurement temperature of 130 ° C., an observation range of 10 to 42 ppm, and a cumulative number of 64,000 times in order to determine the ratio between the long chain branch points and the short chain branch points and the long chain branch points. .

The DEPT (Distortionless Enhancement by Polarization Transfer) method is a method for discriminating the series of carbons using the intensity change of the ¹³ C-NMR spectrum with respect to the pulse angle (θ) to be irradiated. In the DEPT 90 ° measurement (irradiating a pulse giving θ = 90 °), the methyl and methylene carbon peaks disappear or greatly attenuate, and the methine carbon peak can be observed. That is, since the peak based on methylene carbon of the main chain of the hydrogenated polymer disappears or is greatly attenuated by DEPT 90 ° measurement, the dynamic range due to the main chain methylene peak having a large peak intensity, which is a problem in ordinary NMR measurement, is reduced. The problem is solved. As a result, a long chain branching point present in a minute amount in the polymer can be detected with high sensitivity.

As a result of DEPT 90 ° measurement, the methine carbon at the short chain branch point and the methine carbon at the long chain branch point are observed as different peaks with quantifiable sensitivity (intensity, S / N ratio). That is, the ratio of the number of long chain branch points to the number of short chain branch points (number of long chain branch points / short chain) from the ratio of the peak area of the short chain branch point methine carbon peak to the peak area of the methine carbon peak of the long chain branch point. The number of branch points can be obtained.

The main peaks of the ¹³ C-NMR (DEPT 90 °) spectrum of hydrogenated polybutadiene and their chemical shifts are shown in the following table. The chemical shift is a value based on TMS (tetramethylsilane).

　短鎖分岐点メチンのピーク面積（Ｓ_Ｂ ^＊）＝ピーク［Ｂ１^＊］のピーク面積、
　長鎖分岐点メチンのピーク面積（Ｓ_Ｌ）＝ピーク［Ｌ］のピーク面積、としたとき、
　短鎖分岐点数に対する長鎖分岐点数の比率（長鎖分岐点数／短鎖分岐点数）は、
　　Ｓ_Ｌ／Ｓ_Ｂ ^＊　　（２）
として算出できる。

Peak area of short chain branching point methine (S _B ^* ) = peak area of peak [B1 ^* ],
When the peak area of long chain branching point methine (S _L ) = peak area of peak [L],
The ratio of the number of long-chain branches to the number of short-chain branches (the number of long-chain branches / the number of short-chain branches) is
S _L / S _B ^* (2)
Can be calculated as

And the number of short chain branch points per butadiene monomer unit calculated by the above formula (1) (number of short chain branch points / 1 monomer unit) and the ratio of the long chain branch points to the short chain branch points calculated by the above formula (2) The number of long chain branch points per 10,000 butadiene monomer units can be calculated from (number of long chain branch points / number of short chain branch points).
That is, the number of long chain branch points per 10,000 butadiene monomer units is
(Number of long chain branch points / number of short chain branch points) × (number of short chain branch points / 1 monomer unit) × 10,000
Can be calculated as

Viscoelasticity measurement (measurement of Y _(50%) / Y _(10%) ):
7.5 g of polybutadiene was dissolved in 200 ml of toluene. Next, 7.5 g of liquid paraffin was added to this solution and stirred until uniform. The obtained solution was poured onto a stainless steel tray covered with a PET film, and then vacuum-dried at 60 ° C. for 8 hours using a vacuum dryer. The obtained liquid paraffin 50 mass% solution of polybutadiene was 15 g.

Polybutadiene 1.5g was dissolved in toluene 200ml. Next, 13.5 g of liquid paraffin was added to this solution and stirred until uniform. The obtained solution was poured onto a stainless steel tray covered with a PET film, and then vacuum-dried at 60 ° C. for 8 hours using a vacuum dryer. The liquid polyparaffin 10 mass% solution obtained was 15g.

The angular frequency dependence of the storage elastic modulus G ′ and loss elastic modulus G ″ of the obtained polybutadiene in liquid paraffin 50% by mass and 10% by mass was measured. The measurement was performed in a nitrogen stream using ARES manufactured by TA Instruments equipped with a parallel plate having a diameter of 25 mm or 7.9 mm. The measurement frequency range is 100 to 0.01 rad / s, and the measurement temperatures are 0 ° C., 20 ° C., 40 ° C., 60 ° C., 80 ° C., and 100 ° C. J. et al. D. The frequency-dependent master curve of G 'and G' 'in a wide frequency range is obtained by superposition of temperature-time described in Ferry, "Viscoelastic Properties of Polymers, 3rd ed." (John Wiley & Sons, 1990). obtain.

Using the obtained frequency-dependent master curve of G ′ and G ″, the liquid paraffin solution concentration C of polybutadiene when X = G ″ / C ² = 20,000 Pa (concentration conversion G ″) And Y = G ′ / C ² (concentration conversion G ′) was obtained. And the ratio of Y (Y _(50%) ) obtained from the measured value of the liquid paraffin 50 mass% solution and Y (Y _(10%) ) obtained from the measured value of the liquid paraffin 10 mass% solution (Y _{(50 %)} / Y _(10%) ).

(Evaluation of composition)
Tensile stress: 100% and 300% tensile stress was measured according to JIS-K6251, and indexed with Comparative Example R1 described in Table 3 as 100 (the larger the index, the better).

Abrasion resistance (Lambourn wear resistance): Lambourn wear resistance was measured at a slip rate of 40% according to the measurement method defined in JIS-K6264, and indicated as an index with Comparative Example R1 shown in Table 3 as 100 ( The higher the index, the better.

Rebound resilience: According to JIS-K6255, the rebound resilience was measured at room temperature using a Dunlop trypometer, and displayed as an index with Comparative Example R1 listed in Table 3 being 100 (the larger the index, the better).

Low exothermic property / permanent strain: Measured according to the measurement method defined in JIS-K6265, and displayed as an index with Comparative Example R1 shown in Table 3 being 100 (the larger the index, the better).

Low fuel consumption (tan δ (60 ° C.)): Measured at a temperature range of −120 ° C. to 100 ° C., a frequency of 16 Hz, and a dynamic strain of 0.3% using a viscoelasticity measuring device (manufactured by GABO, EPLEXOR 100N), 60 ° C. Tan δ was used as an index of low fuel consumption. The index was displayed with the comparative example R1 described in Table 3 as 100. Low fuel consumption (tan δ) is better. In addition, the index in Table 3 is described so as to increase as fuel efficiency is improved.

−30 ° C. storage elastic modulus (E ′): Measured using a viscoelasticity measuring apparatus (GABO, EPLEXOR 100N) under the conditions of a temperature range of −120 ° C. to 100 ° C., a frequency of 16 Hz, and a dynamic strain of 0.3%. The storage elastic modulus (E ′) at −30 ° C. was used. The results were expressed as indexes with the comparative example R1 shown in Table 3 being 100 (the larger the index, the lower the elastic modulus at −30 ° C., the better).

(Example 1)
The inside of the autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 545 ml of cyclohexane solvent and 550 ml of butadiene was charged. Next, 3.4 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.88 ml of a cyclohexane solution (0.005 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) gadolinium (Gd (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution of carbenium tetrakis (pentafluorophenyl) borate (0.004 mol / L) 2.2 ml was added. After polymerization at 50 ° C. for 25 minutes, 5 ml of an ethanol solution containing an antioxidant was added to terminate the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. The polymerization conditions, the polymerization results, and the measurement results of the physical properties of the synthesized polybutadiene are shown in Table 1-1 and Table 1-2.

(Example 2)
The inside of an autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 500 ml of cyclohexane solvent and 500 ml of butadiene was charged. Next, 1.5 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.80 ml of a cyclohexane solution (0.005 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) gadolinium (Gd (dpm) ₃ ) was added, followed by hydrogenation. 0.4 ml of a cyclohexane solution of diisobutylaluminum (1 mol / L) and 2.0 ml of a toluene solution of triphenylcarbenium tetrakis (pentafluorophenyl) borate (0.004 mol / L) were added. After polymerization at 50 ° C. for 25 minutes, 6 ml of an ethanol solution containing an antioxidant was added to terminate the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 3)
The inside of the autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 545 ml of cyclohexane solvent and 550 ml of butadiene was charged. Next, 3.4 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.88 ml of a cyclohexane solution (0.005 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) gadolinium (Gd (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution of carbenium tetrakis (pentafluorophenyl) borate (0.004 mol / L) 2.2 ml was added. After polymerization at 50 ° C. for 25 minutes, 5 ml of an ethanol solution containing an antioxidant was added to terminate the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

Example 4
The inside of the 1.5 L autoclave was purged with nitrogen, and a solution consisting of 495 ml of cyclohexane solvent and 500 ml of butadiene was charged. Subsequently, 3.2 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.8 ml of a cyclohexane solution (0.005 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) gadolinium (Gd (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution (0.004 mol / L) 2.0 ml of carbenium tetrakis (pentafluorophenyl) borate was added. After polymerization at 50 ° C. for 25 minutes, 5 ml of an ethanol solution containing an antioxidant was added to terminate the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 5)
The inside of the autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 545 ml of cyclohexane solvent and 550 ml of butadiene was charged. Subsequently, 2.85 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.88 ml of a cyclohexane solution (0.005 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) gadolinium (Gd (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution of carbenium tetrakis (pentafluorophenyl) borate (0.004 mol / L) 2.2 ml was added. After polymerization at 50 ° C. for 25 minutes, 5 ml of an ethanol solution containing an antioxidant was added to terminate the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 6)
The inside of an autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 500 ml of cyclohexane solvent and 500 ml of butadiene was charged. Next, 3.4 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.4 ml of a cyclohexane solution (0.01 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) terbium (Tb (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution (0.004 mol / L) 2.0 ml of carbenium tetrakis (pentafluorophenyl) borate was added. After polymerization at 50 ° C. for 25 minutes, 5 ml of an ethanol solution containing an antioxidant was added to terminate the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. The polymerization conditions, the polymerization results, and the measurement results of the physical properties of the synthesized polybutadiene are shown in Table 1-1 and Table 1-2.

(Example 7)
The inside of the autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 400 ml of cyclohexane solvent and 400 ml of butadiene was charged. Subsequently, 4.0 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.4 ml of a cyclohexane solution (0.01 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) terbium (Tb (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution (0.004 mol / L) 2.0 ml of carbenium tetrakis (pentafluorophenyl) borate was added. After polymerization at 50 ° C. for 25 minutes, 5 ml of an ethanol solution containing an antioxidant was added to terminate the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 8)
The inside of an autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 295 ml of cyclohexane solvent and 300 ml of butadiene was charged. Subsequently, 1.8 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.24 ml of a cyclohexane solution (0.01 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) terbium (Tb (dpm) ₃ ) was added, and then triphenyl was added. 1.2 ml of a toluene solution (0.004 mol / L) of carbenium tetrakis (pentafluorophenyl) borate was added. After polymerization at 50 ° C. for 20 minutes, 4 ml of an ethanol solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

Example 9
The inside of an autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 295 ml of cyclohexane solvent and 300 ml of butadiene was charged. Subsequently, 1.95 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.24 ml of a cyclohexane solution (0.01 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) terbium (Tb (dpm) ₃ ) was added, and then triphenyl was added. 1.2 ml of a toluene solution (0.004 mol / L) of carbenium tetrakis (pentafluorophenyl) borate was added. After polymerization at 50 ° C. for 25 minutes, 4 ml of an ethanol solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 10)
The inside of the autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 545 ml of cyclohexane solvent and 550 ml of butadiene was charged. Next, 3.4 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.88 ml of a cyclohexane solution (0.005 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) dysprosium (Dy (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution of carbenium tetrakis (pentafluorophenyl) borate (0.004 mol / L) 2.2 ml was added. After polymerization at 50 ° C. for 20 minutes, 5 ml of an ethanol solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 11)
The inside of an autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 295 ml of cyclohexane solvent and 300 ml of butadiene was charged. Subsequently, 1.95 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.48 ml of a cyclohexane solution (0.005 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) dysprosium (Dy (dpm) ₃ ) was added, and then triphenyl was added. 1.2 ml of a toluene solution (0.004 mol / L) of carbenium tetrakis (pentafluorophenyl) borate was added. After polymerization at 50 ° C. for 25 minutes, 4 ml of an ethanol solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

Example 12
The inside of an autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 245 ml of cyclohexane solvent and 250 ml of butadiene was charged. Next, 1.5 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, after adding 0.4 ml of a cyclohexane solution (0.005 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) dysprosium (Dy (dpm) ₃ ), triphenyl was added. 1.0 ml of a toluene solution of carbenium tetrakis (pentafluorophenyl) borate (0.004 mol / L) was added. After polymerization at 50 ° C. for 25 minutes, 5 ml of an ethanol solution containing an antioxidant was added to terminate the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 13)
The inside of the 1.5 L autoclave was purged with nitrogen, and a solution consisting of 495 ml of cyclohexane solvent and 500 ml of butadiene was charged. Subsequently, 2.7 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 1.0 ml of a cyclohexane solution (0.01 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) holmium (Ho (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution of carbenium tetrakis (pentafluorophenyl) borate (0.004 mol / L) (5.0 ml) was added. After polymerization at 50 ° C. for 25 minutes, 5 ml of an ethanol solution containing an antioxidant was added to terminate the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 14)
The inside of the 1.5 L autoclave was purged with nitrogen, and a solution consisting of 395 ml of cyclohexane solvent and 400 ml of butadiene was charged. Then, 2.5 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 1.6 ml of a cyclohexane solution (0.01 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) thulium (Tm (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution of carbenium tetrakis (pentafluorophenyl) borate (0.004 mol / L) 8.0 ml was added. After polymerization at 50 ° C. for 20 minutes, 5 ml of an ethanol solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 15)
The inside of an autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 245 ml of cyclohexane solvent and 250 ml of butadiene was charged. Next, 1.5 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.5 ml of a cyclohexane solution (0.01 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) erbium (Er (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution (0.004 mol / L) of carbenium tetrakis (pentafluorophenyl) borate in 2.5 ml was added. After polymerization at 50 ° C. for 20 minutes, 3 ml of an ethanol solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 16)
The inside of the 1.5 L autoclave was purged with nitrogen, and a solution consisting of 495 ml of cyclohexane solvent and 500 ml of butadiene was charged. Next, 3.1 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 1.0 ml of a cyclohexane solution (0.01 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) erbium (Er (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution of carbenium tetrakis (pentafluorophenyl) borate (0.004 mol / L) (5.0 ml) was added. After polymerization at 50 ° C. for 20 minutes, 5 ml of an ethanol solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Example 17)
The inside of an autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 245 ml of cyclohexane solvent and 250 ml of butadiene was charged. Next, 1.5 ml of a cyclohexane solution (2 mol / L) of triethylaluminum (TEAL) was added. Next, 0.5 ml of a cyclohexane solution (0.01 mol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) erbium (Er (dpm) ₃ ) was added, and then triphenyl was added. Toluene solution (0.004 mol / L) of carbenium tetrakis (pentafluorophenyl) borate in 2.5 ml was added. After polymerization at 50 ° C. for 25 minutes, 3 ml of an ethanol solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. Then, physical properties of the synthesized polybutadiene were measured. Table 1-1 shows the polymerization conditions, polymerization results, and measurement results of physical properties of the synthesized polybutadiene.

(Comparative Example 1)
The measurement results of the physical properties of JSR BR01 (polybutadiene polymerized using a Ni-based catalyst) manufactured by JSR Corporation are shown in Table 1-1 and Table 1-2.

As shown in Table 1-1, the polybutadienes obtained in Examples 1 to 17 have a relatively large Tcp / ML _{1 + 4} that is an index of molecular linearity (linearity) of 1.3 or more and 5.0 or less, The cold flow rate (CF) is 5.5 mg / min or less, and the cold flow characteristics are excellent.

(Example R1)
Using the polybutadiene synthesized using Gd (dpm) ₃ in Example 1, according to the formulation shown in Table 2, natural rubber, carbon black, zinc oxide, stearic acid, anti-aging agent and oil are added and kneaded with a plastmill. A primary compounding was carried out, and then a secondary compounding in which a vulcanization accelerator and sulfur were added by a roll was carried out to produce a compounded rubber. Further, this compounded rubber was molded according to the desired physical properties, and press vulcanized at 150 ° C. to produce a vulcanized product, and the physical properties were measured. Table 3 shows the measurement results of the physical properties of various blends.

(Example R2)
Using the polybutadiene synthesized using Tb (dpm) ₃ in Example 6, according to the formulation shown in Table 2, natural rubber, carbon black, zinc oxide, stearic acid, anti-aging agent and oil are added and kneaded with a plastmill. A primary compounding was carried out, and then a secondary compounding in which a vulcanization accelerator and sulfur were added by a roll was carried out to produce a compounded rubber. Further, this compounded rubber was molded according to the desired physical properties, and press vulcanized at 150 ° C. to produce a vulcanized product, and the physical properties were measured. Table 3 shows the measurement results of the physical properties of various blends.

(Example R3)
Using the polybutadiene synthesized using Dy (dpm) ₃ in Example 10, according to the formulation shown in Table 2, natural rubber, carbon black, zinc oxide, stearic acid, anti-aging agent and oil are added and kneaded with a plastmill. A primary compounding was carried out, and then a secondary compounding in which a vulcanization accelerator and sulfur were added by a roll was carried out to produce a compounded rubber. Further, this compounded rubber was molded according to the desired physical properties, and press vulcanized at 150 ° C. to produce a vulcanized product, and the physical properties were measured. Table 3 shows the measurement results of the physical properties of various blends.

(Example R4)
Using the polybutadiene synthesized using Ho (dpm) ₃ in Example 13, according to the formulation shown in Table 2, natural rubber, carbon black, zinc oxide, stearic acid, anti-aging agent, and oil are added and kneaded with a plastmill. A primary compounding was carried out, and then a secondary compounding in which a vulcanization accelerator and sulfur were added by a roll was carried out to produce a compounded rubber. Further, this compounded rubber was molded according to the desired physical properties, and press vulcanized at 150 ° C. to produce a vulcanized product, and the physical properties were measured. Table 3 shows the measurement results of the physical properties of various blends.

(Example R5)
Using the polybutadiene synthesized using Er (dpm) ₃ in Example 16, according to the formulation shown in Table 2, natural rubber, carbon black, zinc oxide, stearic acid, anti-aging agent and oil are added and kneaded with a plastmill. A primary compounding was carried out, and then a secondary compounding in which a vulcanization accelerator and sulfur were added by a roll was carried out to produce a compounded rubber. Further, this compounded rubber was molded according to the desired physical properties, and press vulcanized at 150 ° C. to produce a vulcanized product, and the physical properties were measured. Table 3 shows the measurement results of the physical properties of various blends.

(Comparative Example R1)
Primary blending by adding natural rubber, carbon black, zinc oxide, stearic acid, anti-aging agent and oil with plasto mill according to the blending formulation shown in Table 2, using JSR BR01 manufactured by JSR Corporation of Comparative Example 1 as polybutadiene. Then, the compounding rubber was produced by implementing the secondary compounding which adds a vulcanization accelerator and sulfur with a roll. Further, this compounded rubber was molded according to the desired physical properties, and press vulcanized at 150 ° C. to produce a vulcanized product, and the physical properties were measured. Table 3 shows the measurement results of the physical properties of various blends.

　表２中の数値は、質量部である。

The numerical values in Table 2 are parts by mass.

The numerical values in Table 3 are indexed for each item when each characteristic value of Comparative Example R1 using JSR BR01 manufactured by JSR Corporation is used as a reference (100). The larger the value, the better the characteristics.

As shown in Table 3, the compositions of Examples R1 to R5 using the polybutadiene obtained in Examples 1, 6, 10, 13, and 16 are the compositions of Comparative Example R1 using JSR BR01 manufactured by JSR Corporation. It has superior rebound resilience, low-temperature storage elastic modulus at -30 ° C, and low fuel consumption (tan δ (60 ° C)), and wear resistance, low heat build-up, and permanent set are equivalent or better.

According to the present invention, it is possible to provide a polybutadiene having a relatively large Tcp / ML _{1 + 4} that is an index of molecular linearity (linearity) and having excellent cold flow characteristics. In addition, according to the present invention, it is possible to provide a polybutadiene having excellent properties of a polybutadiene having a low degree of branching, for example, excellent wear resistance, low heat generation, rebound resilience, and excellent cold flow properties. it can. The polybutadiene of the present invention is excellent in wear resistance, low heat build-up, rebound resilience, and the like, and can be suitably used for rubber compositions, particularly tire rubber compositions.

Claims (12)

The ratio (Tcp / ML _{1 + 4} ) of 5% toluene solution viscosity (Tcp) measured at 25 ° C. and Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is 1.3 or more and 5.0 or less,
The molecular weight distribution (Mw / Mn) is 2.0 or more and less than 4,
A polybutadiene having a cold flow rate (CF) of 5.5 mg / min or less. The polybutadiene according to claim 1, wherein the Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is 25 or more and 60 or less. The number of long chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of hydrogenated polybutadiene (provided that the long chain branch points are formed from two or more butadiene units). Is a branch point where a branched chain having 6 or more carbon atoms is bonded to the main chain.) Is 9 or less,
Concentration-converted G ″ and concentration-converted G ′ obtained from measurement of the angular frequency dependence of the storage elastic modulus G ′ and the loss elastic modulus G ″ of a liquid paraffin 50% by mass and 10% by mass solution X = Y ratio G ′ / C ² = 20,000 Pa when Y = G ′ / C ² (where C represents the solution concentration) [Y _(50%) / Y _{(10% ) (where, Y (50%)} is the value found from the measured values of liquid paraffin 50 wt% _{solution, Y (10%)} is a value determined from the measured values of the liquid paraffin 10 wt% solution.)] is, Polybutadiene characterized by being greater than 2. The number of long chain branch points per 10,000 butadiene monomer units determined from ¹³ C-NMR measurement of hydrogenated polybutadiene (provided that the long chain branch points are formed from two or more butadiene units). Is a branch point where a branched chain having 6 or more carbon atoms is bonded to the main chain.) Is 9 or less,
A polybutadiene having a cold flow rate (CF) of 5.5 mg / min or less. The ratio (Tcp / ML _{1 + 4} ) of 5% toluene solution viscosity (Tcp) measured at 25 ° C. to Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is 1.3 or more,
Concentration-converted G ″ and concentration-converted G ′ obtained from measurement of the angular frequency dependence of the storage elastic modulus G ′ and the loss elastic modulus G ″ of a liquid paraffin 50% by mass and 10% by mass solution X = Y ratio G ′ / C ² = 20,000 Pa when Y = G ′ / C ² (where C represents the solution concentration) [Y _(50%) / Y _{(10% ) (where, Y (50%)} is the value found from the measured values of liquid paraffin 50 wt% _{solution, Y (10%)} is a value determined from the measured values of the liquid paraffin 10 wt% solution.)] is, Polybutadiene characterized by being greater than 2. 6. The polybutadiene according to claim 1, wherein the cis-1,4-structure content is 90% or more. A rubber composition comprising the polybutadiene according to any one of claims 1 to 6. A tire rubber composition comprising the polybutadiene according to any one of claims 1 to 6. The tire rubber composition according to claim 8, comprising a diene polymer other than polybutadiene and a rubber reinforcing agent. The tire rubber composition according to claim 9, wherein the diene polymer is at least one of natural rubber, styrene-butadiene rubber, and polyisoprene. The rubber composition for tire according to claim 9 or 10, wherein the rubber reinforcing agent is carbon black and / or silica. A tire comprising the rubber composition for a tire according to any one of claims 8 to 11 as a rubber base material.