JP2008163162A - Method for producing vinyl-cis-polybutadiene rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a vinyl-cis-polybutadiene having a further improved tensile stress being an excellent characteristic of a conventional vinyl-cis-polybutadiene. <P>SOLUTION: The method for producing a vinyl-cis-polybutadiene comprises a process for subjecting 1,3-butadiene to 1,2-polymerization in a mixture comprising a hydrocarbon-based organic solvent as a main component into which a syndiotactic-1,2-polybutadiene having a particle diameter of 20-100 nm is dispersed and in which a cis-1,4-polybutadiene is dissolved in the presence of a catalyst obtained from a soluble cobalt compound, an organoaluminum compound represented by the general formula AlR<SB>3</SB>(R is a 1-6C alkyl group, a phenyl group or a cycloalkyl group) and carbon disulfide. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a vinyl-cis polybutadiene rubber having excellent extrudability, tensile stress, and flex crack growth resistance.

  The 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 has a structure in which a vinyl group is a side chain.

  Conventionally, a method for producing a vinyl-cis polybutadiene rubber composition has been carried out with an aromatic hydrocarbon solvent such as benzene, toluene or xylene. When these solvents were used, the viscosity of the polymerization solution was high, and there were problems with stirring, heat transfer, transfer, etc., and excessive energy was required to recover the solvent.

As the method for manufacturing the water in an inert organic solvent, soluble cobalt compound of the general formula AlR _n X _3-n (where R is an alkyl group, a phenyl group or a cycloalkyl group having 1 to 6 carbon atoms , X is a halogen element, n is a number from 1.5 to 2), and BR is produced by cis 1,4 polymerization of 1,3-butadiene using a catalyst obtained from an organoaluminum chloride. Then, a soluble cobalt compound and a general formula AlR ₃ (wherein R is an alkyl group having 1 to 6 carbon atoms, a phenyl group or a cycloalkyl group) with or without the addition of 1,3-butadiene and / or the solvent to the polymerization system. 1,3-butadiene is syndiotactic 1,2 polymerization (hereinafter abbreviated as 1,2 polymerization) in the presence of a catalyst obtained from an organoaluminum compound and carbon disulfide. ) (See, for example, Japanese Patent Publication No. 49-17666 (Patent Document 1) and Japanese Patent Publication No. 49-17667 (Patent Document 2)).

Also, for example, Japanese Patent Publication No. Sho 62-171 (Patent Document 3), Japanese Patent Publication No. Sho 63-36324 (Patent Document 4), Japanese Patent Publication No. 2-337927 (Patent Document 5), Japanese Patent Publication No. 2-38081 (Patent Document 6), Japanese Patent Publication No. 3-63566 (Patent Document 7), or manufactured by cis 1,4 polymerization of 1,3-butadiene in the presence or absence of carbon disulfide Later, 1,3-butadiene and carbon disulfide are separated and recovered, and 1,3-butadiene substantially free of carbon disulfide and a method of circulating the inert organic solvent are described. Further, Japanese Patent Publication No. 4-48815 (Patent Document 8) discloses a rubber composition having a small die swell ratio and a vulcanized product excellent in tensile stress and bending crack growth resistance suitable as a tire sidewall. Is described.

  Japanese Patent Application Laid-Open No. 2000-44633 (Patent Document 9) discloses an inert organic solvent mainly composed of a C4 fraction such as n-butane, cis 2-butene, trans-2-butene, and butene-1. The method of manufacturing in is described. 1,2-polybutadiene contained in the rubber composition in this method is a short fiber crystal, and the distribution of the major axis length of the short fiber crystal is 98% or more of the fiber length is less than 0.6 μm, 70% It is described that the above is less than 0.2 μm, and the resulting rubber composition has the moldability, tensile stress, tensile strength, flex crack growth resistance of cis 1,4 polybutadiene rubber (hereinafter abbreviated as BR), etc. Is described as being improved.

However, in addition to further improvement of moldability, various properties are desired to be improved depending on the application, and the above-mentioned vinyl-cis polybutadiene rubber is more exothermic and repellent than ordinary high cis-1,4-polybutadiene. There was also a point that it was inferior in elasticity.

Japanese Patent Publication No.49-17666 Japanese Patent Publication No.49-17667 Japanese Patent Publication No.62-171 Japanese Examined Patent Publication No. 63-36324 JP-B-2-37927 JP-B-2-38081 Japanese Examined Patent Publication No. 3-63566 Japanese Patent Publication No. 4-48815 JP 2000-44633 A

  An object of the present invention is to provide a method for producing vinyl cis polybutadiene in which the tensile stress, which is an excellent characteristic of conventional vinyl cis polybutadiene, is further improved.

  The present invention is soluble in a mixture mainly composed of a hydrocarbon-based organic solvent in which syndiotactic-1,2-polybutadiene having a particle size of 20 to 100 nm is dispersed and cis-1,4-polybutadiene is dissolved. In the presence of a catalyst obtained from a cobalt compound and an organoaluminum compound represented by the general formula AlR3 (wherein R is an alkyl group having 1 to 6 carbon atoms, a phenyl group or a cycloalkyl group) and carbon disulfide, The present invention relates to a method for producing vinyl cis-polybutadiene, comprising a step of 1,2-polymerizing 1,3-butadiene.

According to the present invention, it is possible to produce a vinyl cis polybutadiene rubber which has better processability, exothermic property and rebound resilience than conventional vinyl cis polybutadiene rubber. When the obtained vinyl cis-polybutadiene rubber is used for tires, the workability is improved by its excellent processability in the manufacturing process, and the fuel consumption of the completed tire can be reduced.

The vinyl cis polybutadiene rubber of the present invention is mainly composed of a hydrocarbon-based organic solvent in which syndiotactic-1,2-polybutadiene having a particle diameter of 20 to 100 nm is dispersed and cis-1,4-polybutadiene is dissolved. In a mixture of the following, a soluble cobalt compound and an organic aluminum compound represented by the general formula AlR ₃ (where R is an alkyl group having 1 to 6 carbon atoms, a phenyl group or a cycloalkyl group) and carbon disulfide are obtained. In the presence of the catalyst, 1,3-butadiene is polymerized in a 1,2 step.

Syndiotactic-1,2-polybutadiene (hereinafter abbreviated as SPB) having a particle diameter of 20 to 100 nm can be produced as follows.
A solution containing 1 wt% SPB (containing 2 wt% anti-aging agent with respect to SPB) is prepared by adding SPB to a solvent and dissolving the SPB by heating and stirring at 100 to 150 ° C. for 2 hours. . The solvent may be selected as long as it can dissolve SPB. For example, toluene can be used when the melting point of SPB is 100 to 150 ° C., and xylene can be used when the melting point is 150 to 180 ° C. When the melting point of SPB is 180 ° C. or higher, orthodichlorobenzene is preferred.
The hydrocarbon solvent is cooled to room temperature or lower while stirring, and a predetermined amount of hot SPB solution is injected therein. By this operation, SPB becomes fine particles having a particle diameter of 20 to 100 nm. The melting point of SPB is preferably 100 to 215 ° C.

Examples of the hydrocarbon solvent include aromatic hydrocarbons such as toluene, benzene and xylene, aliphatic hydrocarbons such as n-hexane, butane, heptane and pentane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, Examples thereof include olefinic hydrocarbons such as olefin compounds, cis-2-butene and trans-2-butene, hydrocarbon solvents such as mineral spirit, solvent naphtha and kerosene, and halogenated hydrocarbon solvents such as methylene chloride. 1,3-butadiene may be used as a solvent.

  Among these, toluene, cyclohexane, or a mixture of cis-2-butene and trans-2-butene is preferably used.

Cis-1,4-polybutadiene can be produced by polymerizing 1,3-butadiene in a hydrocarbon solvent.
The cis-1,4-polybutadiene is preferably cis-1,4-polybutadiene containing 80% or more of cis-1,4 bonds and having a Mooney viscosity (ML1 + 4, 100 ° C.) of 20 to 80. As the cis-1,4-polybutadiene, cis-1,4-polybutadiene synthesized using a cobalt catalyst, a nickel catalyst, or a lanthanoid catalyst can be used alone or in combination of two or more.
For example, cobalt catalysts such as soluble cobalt compounds, organic carboxylates of nickel, organic complex salts of nickel, organic lithium compounds, organic carboxylates of neodymium, organic complex salts of neodymium, and the like.

Hydrocarbon solvents include aromatic hydrocarbons such as toluene, benzene and xylene, aliphatic hydrocarbons such as n-hexane, butane, heptane and pentane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, and the above olefins. Examples thereof include compounds, olefinic hydrocarbons such as cis-2-butene and trans-2-butene, hydrocarbon solvents such as mineral spirit, solvent naphtha and kerosene, and halogenated hydrocarbon solvents such as methylene chloride. 1,3-butadiene monomer itself may be used as a polymerization solvent.

Among these, toluene, cyclohexane, or a mixture of cis-2-butene and trans-2-butene is preferably used.

Cis-1,4-polybutadiene is dissolved in a hydrocarbon solvent in which the SPB particles are dispersed. The concentration of cis-1,4-polybutadiene is preferably 5 to 30 wt%.

1,3-butadiene, an organoaluminum compound represented by the general formula AlR ₃ , and a mixture of hydrocarbon solvents in which SPB particles obtained as described above are dispersed and in which cis-1,4-polybutadiene is dissolved; Carbon sulfide and a soluble cobalt compound are added, and 1,3-butadiene is polymerized in 1,2 to produce vinyl cis polybutadiene rubber (VCR). When the mixture contains 1,3-butadiene, it is not necessary to add 1,3-butadiene. Preferable examples of the organoaluminum compound represented by the general formula AlR ₃ include trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, and triphenylaluminum. The organoaluminum compound is at least 0.1 mmol, especially 0.5 to 50 mmol, per mole of 1,3-butadiene. The carbon disulfide is not particularly limited, but is preferably one that does not contain moisture. The concentration of carbon disulfide is 20 mmol / L or less, particularly preferably 0.01 to 10 mmol / L. A known phenyl isothiocyanate or xanthate compound may be used as an alternative to carbon disulfide.

The temperature for the 1,2 polymerization is preferably from -5 to 100 ° C, particularly preferably from -5 to 80 ° C. 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 is added to the polymerization system for the 1,2 polymerization. The yield of 1,2-polybutadiene can be increased. The polymerization time (average residence time) is preferably in the range of 5 minutes to 2 hours. The 1,2 polymerization is preferably performed so that the polymer concentration after the 1,2 polymerization is 9 to 29% by weight. The polymerization tank is performed by connecting one tank or two or more tanks. The polymerization is carried out by stirring and mixing the polymerization solution in a polymerization tank (polymerizer). As a polymerization tank used for 1,2 polymerization, a higher viscosity is obtained during the 1,2 polymerization, and the polymer easily adheres, so that a polymerization tank equipped with a high-viscosity liquid stirring device, for example, an apparatus described in Japanese Patent Publication No. 40-2645 Can be used.

After the polymerization reaction reaches a predetermined polymerization rate, a known anti-aging agent can be added according to a conventional method. Representative of the antioxidants are phenol-based 2,6-di-t-butyl-p-cresol (BHT), phosphorus-based trinonylphenyl phosphite (TNP), sulfur-based 4.6-bis (octylthio). Methyl) -o-cresol, dilauryl-3,3′-thiodipropionate (TPL) and the like. It may be used alone or in combination of two or more, and the addition of the antioxidant is 0.001 to 5 parts by weight with respect to 100 parts by weight of the VCR. Next, a polymerization terminator is added to the polymerization system and stopped. For example, after the polymerization reaction is completed, the polymer is supplied to a polymerization stop tank, and a large amount of a polar solvent such as alcohol such as methanol or ethanol or water is added to the polymerization solution, or an inorganic acid such as hydrochloric acid or sulfuric acid, acetic acid, benzoic acid, etc. This is a method known per se, such as a method of introducing an organic acid or hydrogen chloride gas into the polymerization solution. Subsequently, vinyl cis polybutadiene (hereinafter abbreviated as VCR) produced according to a usual method is separated, washed and dried.

The proportion (HI) of boiling n-hexane insoluble matter in the obtained vinyl cis-polybutadiene is preferably 3 to 60% by weight, particularly 5 to 30% by weight, and particularly preferably 5 to 20% by weight.
The boiling n-hexane soluble component is cis 1,4-polybutadiene having a microstructure of 90% or more.

The VCR thus obtained was separated from the remaining unreacted 1,3-butadiene, inert medium and carbon disulfide-containing mixture by distillation as 1,3-butadiene, an inert medium. On the other hand, carbon disulfide is separated and removed by adsorption separation treatment of carbon disulfide or separation treatment of carbon disulfide adduct, and 1,3-butadiene and an inert medium substantially free of carbon disulfide are recovered. To do. Further, carbon disulfide is substantially contained by recovering three components from the mixture by distillation and separating and removing carbon disulfide from the distillation by the adsorption separation or carbon disulfide deposit separation treatment. Unrecovered 1,3-butadiene and inert media can also be recovered. The carbon disulfide recovered as described above and the inert medium are used by mixing freshly replenished 1,3-butadiene.

When continuously operated by the method according to the present invention, the operability of catalyst components is excellent, and a VCR can be produced continuously for a long time with high catalyst efficiency and industrially advantageously. In particular, it can be continuously produced industrially advantageously at a high conversion without adhering to the inner wall of the polymerization tank, the stirring blade, and other parts where the stirring is slow.

  The physical properties of the vinyl cis polybutadiene rubber obtained according to the present invention are measured as follows.

Mooney Viscosity JIS K6300 Unvulcanized Rubber Physical Properties Shimadzu Mooney Viscometer (SMV-202) 100 ° C. preheating 1 minute measurement 4 minute value (ML _{1 + 4} ).

PB melting point, heat of fusion, crystallization temperature; UBR analysis center request analysis Shimadzu heat flow rate differential scanning calorimeter (DSC-50)
Sample ≈ 10 mg, 10 ° C / min-in N ₂

Hexane-insoluble matter (HI = SPB component): DSC conversion HI measurement The amount of heat of fusion obtained by DSC and the calibration curve of HI obtained by the actual measurement HI measurement method were obtained.
Measured HI measurement method: To 350 ml of n-hexane stirred with a stirrer, 5 g of precisely weighed vinyl cis-polybutadiene was chopped into a match-sized size and dissolved. Next, this solution is filtered with a pre-weighed advantech cylindrical filter paper 86R (20 × 100 mm), and the insoluble part remaining on the filter paper is subjected to Soxhlet extraction with n-hexane for 3 hours and vacuum dried at 60 ° C. for 3 hours. HI% was calculated by accurately weighing.

Measurement of particle diameter of PB fine particles It was measured with a laser particle size analyzer LPA-300 manufactured by Otsuka Electronics.

The present invention will be described below based on examples.

850 ml of cyclohexane was introduced into a 1 L stainless steel autoclave equipped with helical blades and cooled to 15 ° C. Under stirring, 13 ml of a 150 ° C. SPB / ODCB solution (1 wt%) (containing 170 mg of SPB having a melting point of 145 ° C.) was injected. When a part of the solution was extracted and the particle size was measured, it was confirmed that the particles were 40 nm.
88 g of cis-1,4-polybutadiene (UBEPOL-BR130B manufactured by Ube Industries) was placed in a 1.5 L stainless steel autoclave equipped with helical blades, and the atmosphere was sufficiently replaced with nitrogen. Next, the entire amount of the SPB particle / cyclohexane solution was introduced and stirred at room temperature for 16 hours.
100 ml of 1,3-butadiene was added to a 300 ml glass autoclave equipped with a vertical stirring blade and stirred at 300 rpm. Next, 4.0 ml of a cyclohexane solution (2.0 M) of triethylaluminum (TEA) and 8.0 ml of a cyclohexane solution of cobalt octenoate (Co (Oct) ₂ ) (0.05 M) were added and reacted at 25 ° C. for 5 minutes. It was. This 1,3-butadiene solution was transferred to the above 1.5 L stainless steel autoclave, and the temperature of the solution was adjusted to 50 ° C. Next, 6.4 ml of a cyclohexane solution (0.25 M) of carbon disulfide (CS ₂ ) was added, and 1,2 polymerization was performed at 50 ° C. for 10 minutes. The polymerization was terminated by adding 5 ml of a 5% solution of Irganox 1076 in a 1: 1 mixture of n-heptane and ethanol and releasing the pressure while cooling the autoclave with ice water. When the pressure returned to normal pressure, the polymer was recovered in a vat and vacuum dried at 100 ° C. for 5 hours. The polymerization conditions are shown in Table 1, and the polymerization results are shown in Table 2.

(Comparative Example 1)
The same operation as in Example 1 was conducted except that the SPB / ODCB solution (1 wt%) was changed to ODCB.
From the polymerization results, it can be seen that the example has a higher ML _{1 + 4} / HI than the comparative example and is excellent in reinforcement.

Claims (1)

In a mixture mainly composed of a hydrocarbon-based organic solvent in which syndiotactic-1,2-polybutadiene having a particle size of 20 to 100 nm is dispersed and cis-1,4-polybutadiene is dissolved, a soluble cobalt compound and general In the presence of a catalyst obtained from an organoaluminum compound represented by the formula AlR ₃ (where R is an alkyl group having 1 to 6 carbon atoms, a phenyl group or a cycloalkyl group) and carbon disulfide, -A process for producing vinyl cis-polybutadiene, which comprises a step of polymerizing butadiene 1 or 2.