JP5287436B2 - Method for producing reinforced polybutadiene rubber - Google Patents

Description

  The present invention relates to a method for producing a reinforced polybutadiene rubber comprising cis-1,4-polybutadiene and syndiotactic-1,2-polybutadiene.

  Reinforced polybutadiene rubber (also called vinyl cis-polybutadiene rubber or VCR) in which syndiotactic-1,2-polybutadiene crystals are dispersed in cis-1,4-butadiene rubber is a conventional cis-1,4-butadiene. It is known as a material that facilitates higher hardness, higher elastic modulus and improved workability of products compared to rubber.

In Japanese Patent Publication No. 49-17666 (Patent Document 1) and Japanese Patent Publication No. 49-17667 (Patent Document 2), as a method for producing a reinforced polybutadiene rubber, 1,3-butadiene is used in an inert organic solvent. water, soluble cobalt compound, and the general formula and the cis-1,4 polymerization using a AlR _n X _3-n catalyst obtained from organic halides representable, followed by soluble cobalt compounds in the polymerization system, the general formula AlR ₃ And a method of synthesizing 1,3-butadiene with syndiotactic-1,2 polymerization using a syndiotactic-1,2 polymerization catalyst obtained from carbon disulfide. It is described that the obtained reinforced polybutadiene rubber is excellent in tear strength, bending crack resistance, and the like without impairing the properties of cis-1,4-butadiene rubber.

Furthermore, JP 2000-44633 A (Patent Document 3) discloses a method for producing a novel reinforced polybutadiene rubber using the same method as described above in an inert organic solvent containing a C ₄ fraction as a main component. It is disclosed. In the obtained reinforced polybutadiene rubber, syndiotactic-1,2-polybutadiene has a dispersion form of short fiber crystals, moldability, tensile stress, tensile strength, flex crack resistance compared to conventional reinforced polybutadiene rubber It describes that it is excellent in growth and the like.

Japanese Patent Publication No.49-17666 Japanese Patent Publication No.49-17667 JP 2000-44633 A

  An object of the present invention is to provide a reinforced polybutadiene rubber comprising cis-1,4-polybutadiene and syndiotactic-1,2-polybutadiene having excellent fatigue resistance.

The present inventors polymerized 1,3-butadiene in a cis-1,4 polymerization in an inert organic solvent comprising a C ₄ fraction mainly composed of cis and trans-2-butene and a cyclic aliphatic hydrocarbon, Subsequently, in the production of reinforced polybutadiene rubber that undergoes syndiotactic-1,2 polymerization, the number of moles of halogen (A) in the halogen-containing organoaluminum compound and the number of moles of organoaluminum compound in syndiotactic-1,2 polymerization ( It has been found that the fatigue resistance of the resulting reinforced polybutadiene rubber is improved by setting the ratio (B) / (A) to B in a specific range.

That is, the present invention relates to a soluble cobalt compound, a general formula AlR in an inert organic solvent composed of a C ₄ fraction mainly composed of cis and trans-2-butene with 1,3-butadiene and a cyclic aliphatic hydrocarbon. ^a _n X _3-n (wherein R ^a is an alkyl group having 1 to 6 carbon atoms, a phenyl group or a cycloalkyl group, X is a halogen element, and n is 1.5 to 2). Cis-1,4 polymerization with a halogen-containing organoaluminum compound and a catalyst comprising water, and the resulting polymerization reaction mixture contains a soluble cobalt compound, a general formula AlR ^b ₃ (where R ^b is a C 1-6 carbon atom). Reinforced polybutadiene rubber that is syndiotactic-1,2 polymerized in the presence of carbon disulfide by adding an organoaluminum compound represented by an alkyl group, phenyl group or cycloalkyl group) In the syndiotactic-1,2 polymerization, the ratio of the number of moles of halogen atoms (A) in the halogen-containing organoaluminum compound to the number of moles (B) of the organoaluminum compound in the syndiotactic-1,2 polymerization (B) / ( A) is a manufacturing method of the reinforced polybutadiene rubber characterized by being 2.0-10.

  According to the present invention, a reinforced polybutadiene rubber having excellent fatigue resistance can be provided.

  The reinforced polybutadiene rubber of the present invention can be produced by a two-stage polymerization method. That is, cis-1,4 polymerization is carried out in the first stage, and syndiotactic-1,2 polymerization is carried out as the second stage without stopping the polymerization as it is. A reinforced polybutadiene rubber in which tactic-1,2-polybutadiene crystals are dispersed is obtained.

Solvents used for polymerization are cis and trans-2-butene as the main components, C ₄ fraction which is a C ₄ hydrocarbon mixture containing 1-butene, n-butane and the like, and cyclic such as cyclopentane and cyclohexane. It is a mixed solvent composed of aliphatic hydrocarbons. The concentration of 1,3-butadiene in the reaction system is preferably 10 to 60% by weight.

Cis-1,4 polymerization catalyst, soluble cobalt compound, general formula AlR ^a _n X _3-n (where, R ^a is an alkyl group, a phenyl group or a cycloalkyl group having 1 to 6 carbon atoms, X is a halogen And a catalyst comprising a halogen-containing organoaluminum compound and water.

  Examples of the soluble cobalt compound include cobalt β-diketone complexes such as cobalt (II) acetylacetonate and cobalt (III) acetylacetonate, cobalt β-keto acid ester complexes such as cobalt acetoacetic acid ethyl ester complex, and cobalt octoate. And cobalt halides such as cobalt salts of organic carboxylic acids having 6 or more carbon atoms such as ate, cobalt naphthenate, and cobalt benzoate, cobalt chloride pyridine complexes, and cobalt chloride ethyl alcohol complexes.

The amount of these cobalt compounds used is usually in the range of 1 × 10 ⁻⁷ to 1 × 10 ⁻⁴ mol, preferably 1 × 10 ⁻⁶ to 1 × 10 ⁻⁵ mol, relative to 1 mol of butadiene.

Formula AlR ^a _n X _3-n (where, R ^a is an alkyl group, a phenyl group or a cycloalkyl group having 1 to 6 carbon atoms, X is halogen, n represents a 1.5-2) Examples of the halogen-containing organoaluminum compound represented by the formula: And alkyl aluminum dihalides. Specific examples of the compound include diethylaluminum monochloride, diethylaluminum monobromide, dibutylaluminum monochloride, ethylaluminum sesquichloride, ethylaluminum dichloride, dicyclohexylaluminum monochloride, and diphenylaluminum monochloride. Is preferred. These can be used alone or as a mixture.

  The amount of these halogen-containing organoaluminum compounds used is usually in the range of 10 to 5000 mol, preferably 50 to 1000 mol, per 1 mol of the soluble cobalt compound.

  The usage-amount of water is 0.1-1.45 mol normally with respect to 1 mol of aluminum compounds, Preferably it is 0.2-1.2 mol.

  The order of addition of the catalyst components is not particularly limited, but it is preferable to mix the halogen-containing organoaluminum with water in advance and use it after aging. The aging time is preferably 0.1 to 24 hours, and the aging temperature is preferably 0 to 80 ° C.

  Known molecular weight regulators at the time of polymerization, for example, non-conjugated dienes such as hydrogen, cyclooctadiene, and allene, or α-olefins such as ethylene, propylene, and butene-1 can be used. Moreover, in order to suppress the gel formation at the time of superposition | polymerization, a well-known antigelling agent can be used.

  The polymerization temperature is preferably in the range of 0 ° C to 100 ° C, particularly preferably in the range of 20 ° C to 80 ° C. The polymerization time is preferably in the range of 5 minutes to 5 hours, particularly preferably 10 minutes to 2 hours. The polymerization pressure is performed under normal pressure or a pressure up to about 10 atmospheres (gauge pressure). Polymerization is carried out by connecting one tank or two or more tanks, preferably while stirring and mixing the solution in the tank, and polymerizing so that the polymer concentration after polymerization is 5 to 26% by weight. Is preferred.

  Using the cis-1,4 polymerization reaction mixture obtained as described above, syndiotactic-1,2 polymerization is subsequently carried out in this polymerization system. At this time, 1,3-butadiene may or may not be added.

In the present invention, syndiotactic-1,2 polymerization is carried out by adding a soluble cobalt compound, a general formula AlR ^b ₃ (wherein R ^b is an alkyl group having 1 to 6 carbon atoms, phenyl, to the above cis-1,4 polymerization reaction mixture. It is carried out by adding an organoaluminum compound and carbon disulfide represented by a group or a cycloalkyl group.

  The soluble cobalt compound added here may be the same as or different from that used in the cis-1,4 polymerization, but is preferably the same. In this case, the soluble cobalt compound used in cis-1,4 polymerization is added as necessary.

Examples of the trialkylaluminum that is an organoaluminum compound represented by the general formula AlR ^b ₃ (where R ^b is an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a cycloalkyl group) include triethylaluminum, trimethylaluminum, Examples include triisobutylaluminum, trihexylaluminum, and trioctylaluminum. Of these, triethylaluminum is preferable. These can be used alone or as a mixture.

  The amount of these trialkylaluminums used is usually in the range of 10 to 5000 mol, preferably 50 to 1000 mol, per 1 mol of the soluble cobalt compound.

In the syndiotactic-1,2 polymerization of the present invention, the general formula AlR ^a _n X _3-n (where, R ^a is an alkyl group, a phenyl group or a cycloalkyl group having 1 to 6 carbon atoms, X is a halogen The number of moles of halogen atoms (A) in the halogen-containing organoaluminum compound represented by the general formula AlR ^b ₃ (where R ^b is 1 to 2 carbon atoms). The ratio (B) / (A) of the number of moles to the organoaluminum compound represented by 6) is an alkyl group, a phenyl group or a cycloalkyl group. This ratio is more preferably 2.0 to 7.5, and particularly preferably 2.0 to 5.0.

  In the present invention, carbon disulfide is added after cis-1,4 polymerization. The carbon disulfide is preferably free of moisture, and the concentration is preferably 20 mmol / L or less, and particularly preferably 0.01 to 10 mmol / L.

  The polymerization temperature is preferably in the range of 0 ° C to 100 ° C, particularly preferably in the range of 20 ° C to 80 ° C. The polymerization time is preferably in the range of 5 minutes to 5 hours, particularly preferably in the range of 10 minutes to 2 hours. Further, by adding 1 to 50 parts by weight, preferably 1 to 20 parts by weight of 1,3-butadiene per 100 parts by weight of the cis polymerization solution to the polymerization system, the syndiotactic-1 and 2 syndiotactic at the time of polymerization are performed. Although the yield of tic-1,2-polybutadiene can be increased, the polymerization is preferably carried out so that the polymer concentration after polymerization is 6 to 30% by weight.

  You may add a well-known anti-aging agent in accordance with a conventional method after completion | finish of superposition | polymerization. Anti-aging agents include phenol-based 2,6-di-t-butyl-p-cresol (BHT), phosphorus-based trinonylphenyl phosphite (TNP), and sulfur-based dilauryl-3,3′-thiodipropio. Nate (TPL). These may be used alone or in combination of two or more, and the addition amount is 0.001 to 5 parts by weight with respect to 100 parts by weight of the polymer.

  The polymerization is stopped by adding an alcohol such as methanol or ethanol or a polymerization terminator such as water. For example, a method of introducing a polymerization solution into a polymerization stop tank to which these are supplied in large quantities, an inorganic acid such as hydrochloric acid and sulfuric acid, an organic acid such as acetic acid and benzoic acid, and a method of introducing hydrogen chloride gas into the polymerization solution This is a method known per se. Thereafter, the produced polymer is separated, washed and dried according to a usual method.

The Mooney viscosity (ML _{1 + 4} ) at 100 ° C. of the reinforced polybutadiene rubber obtained as described above is preferably in the range of 20 to 150, particularly in the range of 30 to 110, from the viewpoint of processability and strength. It is preferable.

  The boiling n-hexane insoluble content (HI) of the reinforced polybutadiene rubber is preferably 1 to 25% by weight, more preferably 2 to 22% by weight, and particularly preferably 2.5 to 19% by weight. The melting point is preferably 170 ° C. or higher, particularly 190 to 220 ° C. Here, most of HI is syndiotactic 1,2-polybutadiene, and the boiling n-hexane soluble component is 1,4-cis-polybutadiene.

The content of cis-1,4 structure soluble in boiling n-hexane is preferably 90% or more, particularly preferably 95% or more. Further, the weight average molecular weight (M _w ) is preferably 300,000 to 800,000, particularly preferably 400,000 to 700,000.

The Mooney viscosity (ML _{1 + 4} ) at 100 ° C. of the boiling n-hexane soluble part is preferably 10 to 130, particularly preferably 15 to 80. Moreover, 10-300 are preferable and, as for the 5% toluene solution viscosity (Tcp) measured at 25 degreeC, 20-200 are especially preferable. Furthermore, the intrinsic viscosity ([η]) is preferably 1.0 to 5.0, and particularly preferably 1.0 to 4.0.

The ratio (Tcp / ML _{1 + 4} ) of 5% toluene solution viscosity (Tcp) measured at 25 ° C. to the boiling n-hexane soluble content and Mooney viscosity (ML _{1 + 4} ) at 100 ° C. is 1 or more. Is preferable, and 1.5 or more is particularly preferable.

  The reinforcing effect of syndiotactic 1,2-polybutadiene was obtained by dividing the difference between the Mooney viscosity of the reinforced polybutadiene rubber and the Mooney viscosity of soluble n-hexane (ΔML) by the amount of boiling n-hexane insoluble (HI). It can be represented by a value (ΔML / HI). That is, the larger the ΔML / HI, the higher the reinforcing effect.

  The reinforced polybutadiene rubber obtained by the present invention is used alone or blended with other synthetic rubber or natural rubber, and if necessary, is oil-extended with a process oil, fillers such as carbon black, and other usual compounding agents and vulcanizing agents And after making it the rubber composition which added the vulcanization adjuvant, it can vulcanize | cure and can use it as a rubber | gum for tires. Specifically, it can be suitably used as a tire member such as a sidewall, a tread, a stiffener, a bead filler, an inner liner, and a carcass. In addition, it can also be used for rubber applications that require mechanical properties and wear resistance, such as hoses, belts, and other various industrial products. Furthermore, it can also be used as a plastic modifier.

  The above rubber composition can be obtained by kneading the respective components using a Banbury, an open roll, a kneader, a biaxial kneader, or the like by a conventionally performed method. As the compounding agent, in addition to the above-mentioned filler, vulcanizing agent, vulcanizing aid and process oil, anti-aging agents, zinc white, stearic acid and the like which are usually used in the rubber industry may be used.

  Examples of the filler include inorganic fillers such as calcium carbonate, basic magnesium carbonate, clay, Lissajous and diatomaceous earth, and organic fillers such as recycled rubber and powder rubber. As the vulcanizing agent, known vulcanizing agents such as sulfur, organic peroxides, resin vulcanizing agents, metal oxides such as magnesium oxide, etc. are used. As vulcanizing aids, known vulcanizing aids are used. For example, aldehydes, ammonia, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, xanthates and the like are used. The process oil may be any of aromatic, naphthenic, and paraffinic. Examples of the anti-aging agent include amine / ketone series, imidazole series, amine series, phenol series, sulfur series and phosphorus series.

Hereinafter, the present invention will be specifically described with reference to examples. In addition, the measuring method of a physical property is as follows.
(1) Mooney viscosity (ML _{1 + 4} ): Measured at 100 ° C. according to JIS K6300.
(2) Boiling n-hexane insoluble content (HI): Calculated from a calorific value measured with a differential scanning calorimeter (DSC) using a calibration curve between the heat of fusion prepared in advance and the measured HI. The measured HI is the weight% of the remainder of the extraction after 2 g of reinforced polybutadiene rubber is Soxhlet extracted with 200 ml of n-hexane for 4 hours.
(3) Melting point (T _m ): Determined by the peak temperature of the endothermic curve with a differential scanning calorimeter (DSC).
(4) Evaluation of physical properties of the vulcanized product: After mixing the vulcanization accelerator and other than sulfur in a Banbury mixer according to the following composition table, the resulting mixture, sulfur and the vulcanization accelerator are mixed by a roll and mixed. A rubber composition was prepared. Each obtained compounded rubber composition was press vulcanized at 150 ° C. for 15 minutes to prepare a test piece for evaluation.

Example 1
2.0 L of a mixed solution adjusted to a weight ratio of 42/33/25 of a C ₄ fraction mainly composed of cyclohexane, 1,3-butadiene, cis and trans-2-butene in an autoclave having an internal volume of 5 L And replaced with nitrogen. To this solution, 3.43 mmol of water was added and stirred for 30 minutes, and then 19.6 mmol of 1,5-cyclooctadiene and 6.0 mmol of diethylaluminum chloride were added and stirred for 5 minutes. The solution was brought to 60 ° C., 12.3 mmol of cobalt octoate was added, and cis-1,4 polymerization was performed for 20 minutes. Then, 12.0 mmol of triethylaluminum was added to 40 ° C., 0.012 mmol of cobalt octoate, 11.0 mmol of water and 0.50 mmol of carbon disulfide were added, and syndiotactic-1,2 polymerization was performed for 20 minutes. After a predetermined time, a 1: 1 mixture of n-heptane and ethanol containing an antioxidant was added to stop the polymerization, and the polymer was recovered and dried to obtain a reinforced polybutadiene rubber. ML _{1 + 4} of the obtained reinforced polybutadiene rubber was 50.3, HI was 14.4% by weight, and the melting point of syndiotactic-1,2 polybutadiene was 199.5 ° C. The physical property evaluation results of the vulcanizate are shown in Table 2.

(Comparative Example 1)
A reinforced polybutadiene rubber was obtained in the same manner as in Example 1 except that 7.8 mmol of triethylaluminum added during the syndiotactic-1,2 polymerization was used. ML _{1 + 4} of the obtained reinforced polybutadiene rubber was 53.7, HI was 12.2 wt%, and the melting point of syndiotactic-1,2 polybutadiene was 198.8 ° C. The physical property evaluation results of the vulcanizate are shown in Table 2.

(Comparative Example 2)
A reinforced polybutadiene rubber was obtained in the same manner as in Example 1 except that the amount of triethylaluminum added during the syndiotactic-1,2 polymerization was 9.0 mmol. ML _{1 + 4} of the obtained reinforced polybutadiene rubber was 56.8, HI was 13.7% by weight, and the melting point of syndiotactic-1,2 polybutadiene was 198.8 ° C. The physical property evaluation results of the vulcanizate are shown in Table 2.

Claims (1)

1,3-butadiene with _{C 4} fraction and an inert organic solvent consisting of cyclic aliphatic hydrocarbons consisting mainly of cis and trans-2-butene, soluble cobalt compound, general formula AlR ^a _n X _3-n (Wherein R ^a is an alkyl group having 1 to 6 carbon atoms, a phenyl group or a cycloalkyl group, X is a halogen element, and n is 1.5 to 2). Cis-1,4 polymerization with a catalyst comprising a compound and water, and the resulting polymerization reaction mixture is soluble in a cobalt compound, a general formula AlR ^b ₃ (where R ^b is an alkyl group having 1 to 6 carbon atoms, a phenyl group or A method for producing a reinforced polybutadiene rubber in which syndiotactic-1,2 polymerization is performed in the presence of carbon disulfide. In Nji syndiotactic-1,2 polymerization, the number of moles of the halogen atom of the organoaluminum compound in halogen-containing (A) and organoaluminum compound ^(AlR _{b 3)} the ratio of moles of (B) (B) / ( A) Is 2.0-10, The manufacturing method of the reinforced polybutadiene rubber characterized by the above-mentioned.