JP2015189971A - polybutadiene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide novel polybutadiene which has improved cold flow property even when being a linear polybutadiene, and contributes to balance improvement of abrasion resistance, processability and low loss property and tensile property when used for a rubber composition.SOLUTION: There is provided a polybutadiene having a cold flow speed (mg/min.) at temperature of 50°C of 17 or less and a ratio between 5 wt.% toluene solution viscosity (Tcp [cps]) and a Mooney viscosity (ML) at 100°C measured according to JIS-K6300, (Tcp/ML) of 1.8 or more.

Description

  Although the present invention is a linear polybutadiene, it has improved cold flow properties, and contributes to improving the balance of wear resistance, workability, low loss properties and tensile properties when made into a rubber composition. Novel polybutadiene is provided.

Polybutadiene having a high molecular linearity (linearity) has excellent properties such as wear resistance, heat resistance, and impact resilience when used in tires and the like. Tcp / ML _{1 + 4} is empirically used as the linearity index. Tcp indicates the degree of molecular entanglement in the concentrated solution, and the larger Tcp / ML _{1 + 4} , the smaller the degree of branching and the greater the linearity.
However, the polybutadiene has a large cold flow and tends to collapse during transportation and storage.

  Therefore, an invention of a polybutadiene for golf balls that improves the cold flow is disclosed by making the polybutadiene tin-modified while taking advantage of the properties of polybutadiene having high linearity, and then cross-linking with a co-crosslinking agent and peroxides. Patent Document 1).

  Furthermore, another technique is to improve the cold flow of polybutadiene with a high linearity (linearity) produced with a metallocene catalyst, so that it does branch modification with a cobalt-based catalyst without significantly affecting the microstructure. Is disclosed (Patent Document 2).

  However, after modification with tin, a method of adding two kinds of crosslinking agents and a modification process using a cobalt catalyst are added, resulting in high costs. In addition, due to the recent increase in environmental orientation, there has been a demand for linear polybutadiene with improved cold flow that does not involve metals such as tin.

JP 2002-338606 A JP 2004-285335 A

  The purpose of the present invention is to maintain the characteristics as a linear polybutadiene, while being excellent in cold flow properties than in the past, and in the case of a rubber composition, it is excellent in wear resistance, processability, and low loss properties. It is to provide a polybutadiene having a good balance of physical properties and excellent tensile properties.

The cold flow rate (mg / min) at a temperature of 50 ° C. is 17 or less, and the Mooney viscosity (ML _{1 + 4} ) at 100 ° C. measured based on 5 wt% toluene solution viscosity (Tcp [cps]) and JIS-K6300 The ratio (Tcp / ML _{1 + 4} ) with respect to polybutadiene is 1.8 or more.

  The polybutadiene is characterized in that the molecular weight distribution Mz / Mn of the high molecular weight component defined by the ratio of z-average molecular weight and number-average molecular weight of the polybutadiene is 5.70 to 8.00.

  When the polybutadiene according to the present invention defined by specific physical property values is used, the rubber composition has high processability and wear resistance at the same time, and is well balanced with low loss, etc. It can be provided as a material suitable for the application.

(Raw material polybutadiene)
The raw material polybutadiene is polybutadiene polymerized using a cobalt catalyst, a vanadium catalyst, a lithium catalyst, a nickel catalyst, a neodymium catalyst, or the like. In particular, polybutadiene polymerized with a cobalt or neodymium catalyst is preferable.
As the microstructure, 1,4-cis structure is preferably 80% or more, preferably 90% or more, more preferably 95% or more, and particularly preferably 97% or more. This is because a 1,4-cis structure at a higher rate is advantageous from the viewpoints of wear resistance and impact resilience.

Furthermore, the Mooney viscosity (ML _{1 + 4} , 100 ° C.) at 100 ° C. is preferably 20 to 80, more preferably 30 to 70, and particularly preferably 35 to 65. When it is lower than the above range, the impact resilience is low. On the other hand, when it is higher than the above range, workability is adversely affected.

The ratio (Tcp / ML _{1 + 4} ) of 5% by weight toluene solution viscosity (Tcp [cps]) and Mooney viscosity (ML _{1 + 4} ) at 100 ° C. measured based on JIS-K6300 is 1.8 or more as an index of branching degree. Preferably there is.
The smaller the value of (Tcp / ML _{1 + 4} ) as the branching degree index, the larger the branch, and vice versa.
The branch of the polybutadiene before modification used in the present invention is desired to be low and linear. This is because it is more advantageous than branched polybutadiene from the viewpoint of improving fuel efficiency.

(Modification method of polybutadiene)
The polybutadiene in the present invention is obtained by modifying the raw material polybutadiene. This is a so-called modified polybutadiene.
The modification method is a method of crosslinking using a trace amount of organic peroxide.
As the organic peroxide to be used, peroxides are preferable, and examples thereof include dicumyl peroxide and 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane. In addition, benzoyl peroxide, hydrogen peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, 2,2-azobisisobutyronitrile, 2,2-azobis (2-diamino) Propane) hydrochloride, 2,2-azobis (2-diaminopropane) dihydrochloride, 2,2-azobis (2,4-dimethylvaleronitrile), potassium persulfate, sodium persulfate, ammonium persulfate and the like. In particular, use of dicumyl peroxide is preferable.

As a modified form, it is presumed that rubber molecules are loosely crosslinked with peroxide. The amount of the organic peroxide used is preferably 0.001 to 0.010 phr, more preferably 0.001 to 0.080 phr with respect to 100 parts by mass (phr) of the polybutadiene before modification, and 0.001 to 0.080 phr. 0.060 phr is particularly preferred.
If the amount is less than the above range, the crosslinking effect by modification cannot be obtained. On the other hand, when the amount is more than the above range, the crosslinking proceeds excessively to generate a gel, which is not preferable.

(Modification method)
The modification method using an organic peroxide is a commercial grade cis-1,4-polybutadiene (UBEPOL BR150L) wound around a roll using a mixing roll, and then a predetermined amount of organic peroxide is added and further kneaded. The sample obtained in this way is obtained by heat treatment for a predetermined time using a pressure press.

(Modified polybutadiene)
The ratio (Tcp / ML _{1 + 4} ) of the modified polybutadiene 5 wt% toluene solution viscosity (Tcp [cps]) and Mooney viscosity (ML _{1 + 4} ) at 100 ° C. measured based on JIS-K6300 is 1.8 or more. Is more preferably 2.0 or more, and particularly preferably 2.2 or more.
If the value of Tcp / ML _{1 + 4} is high to some extent and is not linear, the above range is preferable because it adversely affects fuel efficiency.

Moreover, it is preferable that the stress relaxation time (T80) until it attenuate | damps 80% when the torque at the time of completion | finish of ML1 _{+ 4} and 100 degreeC measurement is 100% is 3.0-15.0 (second). It is more preferably 1 to 13.0 (seconds), and particularly preferably 3.2 to 10.0 (seconds). The transition of the stress relaxation of rubber is due to a combination of elasticity and viscosity, with slow relaxation indicating a high elastic component and fast relaxation indicating a high viscous component.
If it is smaller than the above range, a sufficient stress cannot be applied when a shear stress is applied. On the other hand, if it is larger than the above range, the residual stress at the time of forming increases, so that problems of workability such as poor dimensional stability occur.

The number average molecular weight (Mn) is preferably 17 × 10 ⁴ to 30 × 10 ^{4, and} more preferably 18 × 10 ^{4 to} 28 × 10 ⁴ . The weight average molecular weight (Mw) is preferably 49 × 10 ⁴ to 80 × 10 ^{4, and} more preferably 50 × 10 ⁴ to 70 × 10 ⁴ . And Z average molecular weight (Mz), preferably ^{120 × 10 4 ~160 × 10 4} .

  In particular, from the viewpoint of low loss (low hysteresis loss), the ratio (Mz / Mn) of the molecular weight distribution Z average molecular weight (Mz) to the number average molecular weight (Mn) in the high molecular weight region is preferably 5.70 to 8.00. .80 to 7.80 are more preferable, and 6.50 to 7.50 are particularly preferable.

  As the microstructure, 1,4-cis structure is preferably 80% or more, preferably 90% or more, more preferably 95% or more, and particularly preferably 97% or more. This is because a 1,4-cis structure at a higher rate is advantageous from the viewpoints of wear resistance and impact resilience. That is, there is almost no change before and after modification, and it is preferable that the cis state be high.

  Further, the 1,2-vinyl structure is 1.3% or less, more preferably 1.1% or less. The ratio of the transformer structure is preferably 1.1% or less.

  The cold flow rate (mg / min) at a temperature of 50 ° C. is 17 or less, preferably 16 or less, particularly preferably 15 or less. When the value of the cold flow is higher than the above range, workability and workability are affected.

  Further, the long chain branching index (LCB Index) as an index of polybutadiene branching is preferably 6.40 or more, more preferably 6.50 or more, and particularly preferably 7.00 or more. Below the above range, the ratio of long-chain branches that can actually have a large effect on cold flow is low, so the effect on cold flow improvement is low.

(Rubber composition)
In order to grasp the performance of the polybutadiene of the present invention, it is necessary to measure various physical properties as a so-called rubber composition by vulcanizing and then blending with other rubber components.
A rubber composition is obtained by blending the above-mentioned modified polybutadiene (A) with other additives such as other diene rubber (B), rubber reinforcing material (C) and vulcanizing agent.

As the compounding amount of the modified polybutadiene in the rubber composition, when the total amount of the rubber compound is 100 parts by mass (herein, the whole rubber compound indicates (A) + (B)). 60 mass parts is good, 10-50 mass parts is more preferable, and 20-40 mass parts is especially preferable.
Use outside this range is not preferred because the balance effect of physical properties, which are excellent in wear resistance and workability and excellent in low loss and tensile properties, is reduced.

(Other diene rubbers)
The other diene rubber (B) contained in the rubber composition is preferably a vulcanizable rubber, specifically, 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-butadiene rubber, natural rubber (NR), etc. Can be mentioned. Among these, SBR is preferable.
Further, among SBR, solution-polymerized styrene butadiene copolymer rubber (S-SBR) is particularly preferable. These rubbers may be used alone or in combination of two or more.

As the microstructure of the solution-polymerized styrene butadiene copolymer rubber (S-SBR) used in the present invention, the styrene content is 15 to 35% by weight, preferably 17 to 30% by weight, and the vinyl bond content of the butadiene portion is 30 to 30%. By using 75%, preferably 32 to 72% of S-SBR, 100 parts by mass of the rubber component, 30 parts by mass or more and less than 90 parts by mass, preferably 50 to 80 parts by mass, the above effect is exhibited. If the blending amount of S-SBR is small, the wet performance decreases, which is not preferable. Conversely, if it is large, the wear resistance and low loss property deteriorate, which is not preferable.
Such S-SBR is known, and for example, commercially available products such as Nippon Zeon Nipol NS110R and Asahi Kasei Asaprene 1204 can be used.

The compounding amount of the modified polybutadiene in the rubber composition is preferably 40 to 95 parts by mass, more preferably 50 to 90 parts by mass, and particularly preferably 60 to 80 parts by mass when the total amount of the rubber compound is 100 parts by mass. .
Use outside this range is not preferred because the balance effect of physical properties, which are excellent in wear resistance and workability and excellent in low loss and tensile properties, is reduced.

(Rubber reinforcement)
As the rubber reinforcing agent, any reinforcing material such as an inorganic rubber reinforcing agent and an organic rubber reinforcing agent can be applied. Inorganic rubber reinforcing agents include precipitated silica, metal oxides, alkali metal salts, and carbon black. However, it is not limited to these. An example of the organic rubber reinforcing agent is fibrous 1,2-polybutadiene. However, it is not limited to this.

  As the rubber reinforcing agent, two or more kinds may be combined in addition to using each reinforcing agent described above alone. For example, silica and carbon black may be used in combination.

  When the rubber reinforcing agent is silica, those obtained by acidification of precipitated silica, particularly soluble silicic acid such as sodium silicate are preferred. Furthermore, as described above, these silicas may be combined with carbon black.

  In addition, commercially available precipitated silica can be used, for example, Rhodia silica (Trademark Hi-Sil) such as Z1165MP and Z165GR, Tosoh VN2 (Trademark Nippon), Evonik Silica VN2 and VN3, etc. Is given. In addition, wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. are listed. Among them, the improvement effect of fracture resistance, wet grip and low rolling resistance are compatible. Wet silica is most preferred because it is most effective.

The most preferable rubber reinforcing agent is an inorganic rubber reinforcing agent, and in particular, precipitated silica having a BET surface area of 100 to 300 m ² / g and a particle size of 0.01 to 0.1 μm.

  The amount of the rubber reinforcing agent is 20 to 80 phr, more preferably 25 to 75 phr, and particularly preferably 30 to 70 phr with respect to 100 parts by mass of the entire rubber compound.

(Other compounds)
In the rubber composition containing a rubber reinforcing agent of the present invention, various chemicals usually used in the rubber industry, for example, a vulcanizing agent, a vulcanization accelerator, a process oil, are used as long as the object of the present invention is not impaired. Anti-aging agent, scorch preventing agent, zinc white, stearic acid and the like can be contained. Further, the rubber composition of the present invention is obtained by kneading using a kneader such as an open kneader such as a roll, a closed kneader such as a Banbury mixer, and vulcanized after molding. Applicable to various rubber products.

(Silane coupling agent)
As another additive component, a silane coupling agent is an organosilicon compound represented by the general formula R ₇ nSiX _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 group, 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. A hydrolytic group selected from a 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.

Among the R ₇ components of the silane coupling agent, those containing a vinyl group and / or a chloro group are preferable.

  Specific examples of silane coupling agents that can be used commercially include, but are not limited to, the following. Bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylpropyl) tetrasulfide, bis (3 -Trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylpropyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethoxysilane 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxy Rylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl Methacrylate monosulfide, vinyltrichlorosilane, methylvinyldichlorosilane, divinyldichlorosilane, dimethylvinylchlorosilane, chloromethyldimethylvinylsilane, methoxydimethylvinylsilane, trimethoxyvinylsilane, dimethyldivinylsilane, ethoxydimethylvinylsilane, diacetoxymethyldinylsilane, allyl Oxydimethylvinylsilane, diethoxymethylvinylsilane, bis (di Tilamino) methylvinylsilane, phenylvinyldichlorosilane, triacetoxyvinylsilane, 3-chloropropylmethyldivinylsilane, diethoxydivinylsilane, dimethylethylmethylketoxyvinylsilane, dimethylisobutoxyvinylsilane, triethoxyvinylsilane, methylphenylvinylchlorosilane, methylphenyl Vinylsilane, dimethylisopentyloxyvinylsilane, 4-bromophenyldimethylvinylsilane, 3-aminophenoxydimethylvinylsilane, 4-aminophenoxydimethylvinylsilane, dimethylpiperidinomethylvinylsilane, dimethyl-2-[(2-ethoxyethoxy) ethoxy] vinylsilane , Divinylmethylphenoxysilane, dimethyl-P-anisylvinylsilane, tris (1 Methylvinyloxy) vinylsilane, triisopropoxyvinylsilane, diethoxy-2-piperidinoethoxyvinylsilane, diphenylvinylchlorosilane, 3-dimethylvinylphenyl N, N-diethylcarbomate, triphenoxyvinylsilane, 1,3-divinyl-1, 1,3,3-tetramethyldisiloxane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1- (4-methylpiperidinomethyl) -1,1,3,3- Tetramethyl-3-vinyldisiloxane, 1,4-bis (dimethylvinylsilyl) benzene, 1,4-bis (dimethylvinylsiloxy) benzene, 1,3-bis (dimethylvinylsiloxy) benzene, 1,1,3 , 3-tetraphenyl-, 3-divinyldisiloxane, 1,3,5-trimethyl-1, , 5-trivinylcyclotrisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, tetrakis (dimethylvinylsiloxymethyl) methane, 3-chloropropyltrimethoxysilane ,and so on.

  The addition amount of the additive silane coupling agent is preferably 0.2 to 20% by weight, particularly preferably 5 to 15% by weight, based on the filler amount.

(Vulcanizing agent)
Although it does not specifically limit as a vulcanizing agent used for the rubber composition for rubber reinforcement compounding concerning the present invention, it is mainly sulfur, and the quantity of 0.1-10 phr is with respect to 100 mass parts of the whole rubber compounding. 1-5 are more preferable. It is known that when the amount of the vulcanizing agent is too large, the elasticity of the rubber vulcanizate is lost because the crosslinking proceeds too much. On the other hand, if the amount of the vulcanized product is too small, rubber elasticity and frictional resistance are insufficient.

(Vulcanization accelerator)
Further, the vulcanization accelerator used in the rubber composition for blending a rubber reinforcing agent according to the present invention is 2-mercaptobenzothiazole (M), dibenzylzothiazyl disulfide (DM), N-cyclohexyl-2-benzothia. Although it is a disulfenamide (CZ) and a diphenyl guanidine (D), it is not limited to these. These vulcanization accelerators may be used in combination. A preferred use amount is 0.1 to 7 phr, more preferably 1 to 5 phr with respect to 100 parts by mass of the entire rubber compound.

  As other compounding components of the rubber composition for compounding a rubber reinforcing agent according to the present invention, process oil, zinc oxide, stearic acid, and antioxidant can be used in the rubber mixing step and the vulcanizing step.

(Process oil)
Examples of the process oil include paraffin oil, naphthenic oil, and aroma oil, but are not limited to these, and aroma oil is preferable. Aroma oils are used to maintain the maximum tensile strength and friction resistance performance of rubber compositions. A preferred amount of process oil is 1-50 phr, more preferably 5-30 phr.

In the production of the rubber composition, after producing the modified polybutadiene, the rubber composition is produced by the following procedure.

Mixing step (manufacturing method of the first rubber composition)
All the rubber compositions except the vulcanizing agent and the vulcanization accelerator are mixed in a closed kneader such as a Banbury mixer at 90 ° C. within 5 minutes. Immediately thereafter, the mixture is cooled in a temperature range of 30 to 60 ° C. using a mixing roll and then formed into a sheet. Therefore, the said mixing process means the mixing process of the rubber composition except a preliminary mixing or a vulcanization raw material.

Vulcanization preliminary process (method for producing the second rubber composition)
The silica-rubber compound sheet obtained from the mixing step described above is mixed with a vulcanizing agent and a vulcanization accelerator using a mixing roll in a temperature range of 30 to 60 ° C. As described above, sulfur is preferable as the vulcanizing agent.

The rubber composition by the vulcanization preliminary process is drawn into a sheet shape, and the sample is Mooney viscosity (ML _{1 + 4} , 100 ° C.), based on JIS K6300-2 (B-2 method) at 160 ° C. in RPA2000 (registered trademark). The optimum vulcanization point and tan δ during vulcanization are measured.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the second rubber composition obtained by the vulcanization preliminary process is smaller than the Mooney viscosity of the first compound obtained from the mixing process, and its value is 50 to 120, more preferably 60. ˜105, particularly preferably 70˜95.

If the Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the second rubber composition in the vulcanization preparatory process is larger than the above range, the molding process performance is inferior, causing problems in workability. The tensile stress of the vulcanizate cannot be obtained, resulting in workability problems.

(Vulcanization characteristics of rubber compounded with silica and physical properties of vulcanizate)
The silica-containing rubber composition of the second rubber composition in the vulcanization preliminary process is produced by press molding at 160 ° C. according to the optimum vulcanization point measured by the aforementioned RPA2000 (registered trademark). The rubber vulcanizate of the present invention follows the measurement of viscoelastic properties through temperature sweep, tensile strength and exothermic properties.

  Examples are shown below.

(1) Microstructure analysis The microstructure was analyzed by infrared absorption spectrum analysis. The microstructure was calculated from the absorption intensity ratio of cis 740 cm ⁻¹ , trans 967 cm ⁻¹ and vinyl 910 cm ⁻¹ .
(2) Measurement of Tcp Toluene solution viscosity (Tcp) was obtained by dissolving 2.28 g of polymer in 50 ml of toluene, and then using a standard solution for calibrating viscometer (JIS Z8809) as a standard solution. And measured at 25 ° C.
(3) Measurement of ML _{1 + 4} , 100 ° C. Mooney viscosity (ML _{1 + 4} , 100 ° C.) was measured according to JIS-K6300.
(4) Measurement of number average, weight average and Z average molecular weight GPC method: Measured by HLC-8220 (manufactured by Tosoh Corporation) and calculated by standard polystyrene conversion. Tetrahydrofuran was used as the solvent, KF-805L (two in series) manufactured by Shodx was used as the column, and a suggestive refractometer (RI) was used as the detector.
(5) Measurement of T80 The measurement of T80 was calculated by the stress relaxation measurement according to ASTM D1646-7.
Specifically, under conditions of ML _{1 + 4} and 100 ° C., the Mooney viscosity when the rotor was stopped (0 seconds) after 4 minutes of measurement was taken as 100%, and the time (seconds) until the value was relaxed by 80% was measured.
(6) Measurement of Lambourne Wear Lambourne wear was measured at a slip rate of 20 percent and 40 percent according to the measurement method defined in JIS-K6264, and indicated as an index with Comparative Example 1 being 100 (the larger the index, the greater the index). Good).
(7) Hardness measurement According to JIS K6253, it measured at room temperature using the type A durometer.
(8) Viscoelasticity tan δ measurement Using an EPLEXOR 100N manufactured by GABO under the conditions of a frequency of 10 Hz and a dynamic strain of 0.3% at temperatures of 50 ° C. and 0 ° C., Comparative Example 1 was shown as an index.
The larger the index, the better the low loss property (50 ° C.) and the wet performance (0 ° C.).
(9) Tensile strength, elongation at break Measured according to JIS K6251. The higher the value, the better.
(10) Cold flow rate The cold flow rate (CF) is obtained by keeping the obtained polymer at 50 ° C., sucking it with a glass tube having an inner diameter of 6.4 mm for 10 minutes with a differential pressure of 180 mmHg, and measuring the weight of the sucked polymer. Thus, the amount of polymer sucked per minute (mg / min) was obtained.
(11) Long chain branching index (LCB Index): Measured by LAOS (Large Amplitude Oscillation Shear) measurement method using RPA2000 type tester (manufactured by Alpha Technologies). In LCB, it is a polymer having a high degree of linearity and a lower degree of branching as the obtained numerical value approaches zero.

(Example 1)
300 grams of polybutadiene, a commercial grade cis-1,4-polybutadiene (UBEPOL BR150L), was wound on a roll at a temperature of 35-45 ° C. using a 6 inch mixing roll, and then 0.001 part by weight of organic peroxidation A modified sample was obtained by adding the product and further kneading. Table 1 shows the physical properties of the obtained polybutadiene.
Each component was blended in the proportions shown in Table 2 for the polybutadiene obtained by the above modification to obtain a rubber composition. The obtained results are shown in the lower part of Table 2.

(Example 2)
A rubber composition was produced in the same manner as in Example 1 except that the amount of peroxide used for modifying (crosslinking) polybutadiene was changed to 0.005 parts by mass. The results are shown in Tables 1 and 2.

(Comparative Example 1)
A rubber composition was produced in the same manner as in Example 1 except that the polybutadiene used in Example 1 was used as it was without being modified with peroxide. The results are shown in Tables 1 and 2.

(Comparative Example 2)
A rubber composition was produced in the same manner as in Comparative Example 1 except that the polybutadiene used in Comparative Example 1 was changed to UBEPOL BR150B manufactured by Ube Industries, Ltd., which is a commercial product. The results are shown in Tables 1 and 2.

Details of each formulation are shown below.
(1) Polybutadiene before modification: UBEPOL BR150L and BR150B manufactured by Ube Industries, Ltd.
(2) Organic peroxide: Nippon Oil & Fats Park Mill D
(3) SBR: Solution polymerization SBR
(4) Silica: Tosoh Silica Co., Ltd., trade name: Nip Seal AQ
(5) Silane coupling agent: Degussa Hyrun, trade name Si69
(6) Aroma oil: Sansen Oil 4240 made by Nippon San Oil
(7) Zinc oxide: Sakai Chemical Industry Sazex No. 1 (8) Stearic acid: Stearic acid manufactured by Kao (9) Antioxidant: Antigen 6C manufactured by Sumitomo Chemical
(10) Sulfur: Sulfur manufactured by Hosoi Chemical Co., Ltd. (11) Vulcanization accelerator 1: Noxeller CZ manufactured by Ouchi Shinsei Chemical Co., Ltd.
(12) Vulcanization accelerator 2: Noxeller D manufactured by Ouchi Shinsei Chemical Co., Ltd.

  From Table 2, it can be seen from the physical property results of the rubber composition having the same composition other than polybutadiene that it is excellent in wear resistance and processability, and also in the balance of low loss and tensile properties. That is, it can be seen that the polybutadiene of the present invention contributes as an effect of improving these physical properties.

  The polybutadiene obtained in the present invention has an improvement effect such as workability and wear resistance, and by using a rubber compound, a tire, a vibration isolating rubber, a belt, a hose, a seismic isolation rubber, a rubber crawler, a footwear member, etc. Can be used.

Claims (2)

The cold flow rate (mg / min) at a temperature of 50 ° C. is 17 or less, and the Mooney viscosity (ML _{1 + 4} ) at 100 ° C. measured based on 5 wt% toluene solution viscosity (Tcp [cps]) and JIS-K6300 And the ratio (Tcp / ML _{1 + 4} ) to 1.8 or more.   2. The polybutadiene according to claim 1, wherein a molecular weight distribution Mz / Mn of a high molecular weight component defined by a ratio of z-average molecular weight and number-average molecular weight of the polybutadiene is 5.70 to 8.00.