JP4367095B2 - Polybutadiene composition for tire - Google Patents

Description

  It relates to a polybutadiene composition for tires that has excellent wear resistance and improved flex crack growth resistance, and includes tire outer members such as treads and sidewalls in tires, tire inner members such as carcass, belts, and beads, and anti-vibration rubbers. It can also be used for industrial goods such as belts, hoses, and seismic isolation rubber, and footwear such as men's shoes, women's shoes, and sports shoes.

  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.

  It is known that the above-mentioned polybutadienes having different microstructures are produced depending on the polymerization catalyst and polymerization conditions, and they are used in various applications depending on their properties.

  For the purpose of improving the wear resistance and heat build-up of tires, polybutadiene rubber (BR) is widely blended with natural rubber or the like, and various proposals have been made for BR. For example, JP-A-7-118443 (Patent Document 1) discloses a BR having a weight average molecular weight of 500,000 to 750,000, a molecular weight distribution of 1.5 to 3.0, and an intrinsic viscosity of 90 or more. No. 247721 (Patent Document 2) discloses BR having a cis content of 95% or more and a molecular weight distribution of 3.5 to 6.0. .

  In general, BR has excellent wear resistance, heat build-up, rebound resilience, etc., but has the disadvantage of poor chip cutability and flex crack growth resistance. If the molecular weight distribution is widened or branched, flex crack growth is Although improved, there was a problem that the wear resistance was lowered.

Japanese Patent Laid-Open No. 7-118443 JP 2001-247721 A

  An object of the present invention is to provide a polybutadiene composition for tires having excellent wear resistance and improved flex crack growth resistance.

In the present invention, (a) a Mooney viscosity of 55 to 65 synthesized using a cobalt-based catalyst and a 5% toluene solution viscosity (Tcp, 25 ° C. ) to Mooney viscosity ( ML _{1 + 4} , 100 ° C. ) ratio (Tcp / ML _{1 + 4} ) is cis 1,4 content of 2.0-4.0 and cis 1,4 content is 97% or more and (b) cis 1,4 content other than (a) cis polybutadiene described above More than 95% cis polybutadiene rubber, low cis polybutadiene rubber, natural rubber, polyisoprene rubber, emulsion polymerization styrene-butadiene rubber, ethylene propylene diene rubber, nitrile rubber, butyl rubber, chloroprene rubber, or derivatives of these rubbers 90 to 10 weight % Rubber component (a) + (b) 100 parts by weight,
The present invention relates to a polybutadiene composition for tires, comprising 1 to 100 parts by weight of carbon black (c).

The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the high cis polybutadiene (a) is preferably 2.5 to 3.8 and the cis content is preferably 95% or more.

  The present invention relates to a polybutadiene composition for tires characterized in that the crack length when bent at 100,000 strokes is 5 mm or less in a flex crack growth test specified in JIS K6260 is 5 mm or less.

  The rubber reinforcing agent (c) is preferably carbon black.

  The polybutadiene composition in the present invention is composed of a rubber component containing a specific high-cis polybutadiene and a rubber reinforcing agent, and is a polybutadiene composition suitable for a tire having excellent wear resistance and improved flex crack growth resistance. Provided.

The polybutadiene of the present invention has the following characteristics.
The Mooney viscosity is 50 to 70, preferably 55 to 65. If the Mooney viscosity is larger than the above range, the workability is deteriorated.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) is 2.5 to 3.8, preferably 2.6 to 3.5, more preferably 2.6 to 3.2. It is. When the molecular weight distribution is larger than the above range, the wear resistance is lowered, and when the molecular weight distribution is smaller than the above range, workability may be deteriorated.

The ratio (Tcp / ML) of 5% toluene solution viscosity (Tcp) to Mooney viscosity (ML) is 1.8 to 5.0, preferably 2.0 to 4.0, more preferably 2.1 to 3.5.
When the Tcp / ML ratio is larger than the above range, the cold flow property of the base rubber is increased, and when it is smaller than the above range, the wear resistance is undesirably lowered.

  The cis 1.4 content is preferably 95% or more, particularly preferably 97% or more. If the cis 1.4 content is less than the above, the wear resistance is lowered, which is not preferable.

  Said polybutadiene can be manufactured with a cobalt-type catalyst. Examples of the cobalt catalyst composition include a catalyst system comprising (A) a cobalt compound, (B) a halogen-containing organoaluminum compound, and (C) water.

  As the cobalt compound, a cobalt salt or complex is preferably used. Particularly preferred are cobalt salts such as cobalt chloride, cobalt bromide, cobalt nitrate, cobalt octylate (ethylhexanoate), cobalt naphthenate, cobalt acetate and cobalt malonate, cobalt bisacetylacetonate and trisacetylacetate. Examples thereof include organic base complexes such as nates, ethyl acetoacetate cobalt, pyridine complexes and picoline complexes of cobalt salts, or ethyl alcohol complexes.

  Examples of the halogen-containing machine aluminum include trialkylaluminum, dialkylaluminum chloride, dialkylaluminum bromide, alkylaluminum sesquichloride, alkylaluminum sesquibromide, alkylaluminum dichloride, and the like.

  Specific examples of the compound include trialkylaluminum such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, and tridecylaluminum.

  In addition, dialkylaluminum chlorides such as dimethylaluminum chloride and diethylaluminum chloride, organoaluminum halogen compounds such as sesquiethylaluminum chloride and ethylaluminum dichloride, hydrogenated organics such as diethylaluminum hydride, diisobutylaluminum hydride and sesquiethylaluminum hydride Aluminum compounds are also included. Two or more of these organoaluminum compounds can be used in combination.

  The molar ratio (B) / (A) between the component (A) and the component (B) is preferably 0.1 to 5000, more preferably 1 to 2000.

  The molar ratio (B) / (C) between the component (B) and the component (C) is preferably 0.7 to 5, particularly preferably 0.8 to 4, and still more preferably 1 to 3. It is.

  In addition to butadiene monomer, isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethylbutadiene, 2-methylpentadiene, 4-methylpentadiene, conjugated dienes such as 2,4-hexadiene, Acyclic monoolefins such as ethylene, propylene, butene-1, butene-2, isobutene, pentene-1, 4-methylpentene-1, hexene-1 and octene-1, cyclic monoolefins such as cyclopentene, cyclohexene and norbornene; And / or an aromatic vinyl compound such as styrene and α-methylstyrene, a non-conjugated diolefin such as dicyclopentadiene, 5-ethylidene-2-norbornene, and 1,5-hexadiene.

  The polymerization method is not particularly limited, and bulk polymerization (bulk polymerization) using a conjugated diene compound monomer such as 1,3-butadiene itself as a polymerization solvent, or solution polymerization can be applied. Solvents used in the solution polymerization 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 like. And 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. .

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

  The polymerization temperature is preferably in the range of -30 to 150 ° C, particularly preferably in the range of 30 to 100 ° C. The polymerization time is preferably in the range of 1 minute to 12 hours, particularly preferably 5 minutes to 5 hours.

  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.

  Examples of the diene rubber (b) other than (a) of the present invention include high cis polybutadiene rubber, low cis polybutadiene rubber (BR), emulsion polymerization or solution polymerization styrene butadiene rubber (SBR), natural rubber, polyisoprene rubber, ethylene. Examples include propylene diene rubber (EPDM), nitrile rubber (NBR), butyl rubber (IIR), and chloroprene rubber (CR).

  Derivatives of these rubbers such as polybutadiene rubber modified with tin compounds and the above-mentioned rubbers modified with epoxy, silane, and maleic acid can also be used. These rubbers can be used alone or in combination of two or more. May be.

As the rubber reinforcing agent of component (c) of the present invention, inorganic reinforcing agents such as various carbon blacks and white carbons, activated calcium carbonate, and ultrafine magnesium silicate, polyethylene resins, polypropylene resins, high styrene resins, phenol resins And organic reinforcing agents such as lignin, modified melamine resin, coumarone indene resin and petroleum resin.
Particularly preferred is carbon black having a particle size of 90 nm or less and a dibutyl phthalate (DBP) oil absorption of 70 ml / 100 g or more, and examples thereof include FEF, FF, GPF, SAF, ISAF, SRF, and HAF.

  The mixing ratio of the rubber composition of the present invention is 10 to 90% by weight of a specific high-cis polybutadiene (a) and a rubber component (a) consisting of 90 to 10% by weight of a diene rubber (b) other than (a). + (B) 100 parts by weight and rubber reinforcing agent (c) 1-100 parts by weight.

Preferably, the specific high-cis polybutadiene (a) 20 to 80% by weight,
Diene rubbers other than (a) (b) 100 parts by weight of rubber component (a) + (b) consisting of 80 to 20% by weight and rubber reinforcing agent (c) 5 to 80 parts by weight

  The rubber composition of the present invention can be obtained by kneading the above components using a conventional Banbury, open roll, kneader, biaxial kneader or the like.

If necessary, the rubber composition of the present invention is kneaded with compounding agents usually used in the rubber industry, such as vulcanizing agents, vulcanization aids, anti-aging agents, fillers, process oils, zinc white, and stearic acid. May be.

As the vulcanizing agent, known vulcanizing agents such as sulfur, organic peroxides, resin vulcanizing agents, and metal oxides such as magnesium oxide are used.

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

Examples of the anti-aging agent include amine / ketone series, imidazole series, amine series, phenol series, sulfur series and phosphorus series.

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.

The process oil may be any of aromatic, naphthenic, and paraffinic.

  In the present invention, it is possible to suitably provide a polybutadiene composition for tires having a stroke of 30 mm and a crack length of 5 mm or less when bent 100,000 times in a flex crack growth test defined in JIS K6260.

  Examples according to the present invention will be specifically described below.

The microstructure was performed 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 .

  The molecular weight (Mw, Mn) was measured by GPC method: HLC-8220 (manufactured by Tosoh Corporation) and calculated by standard polystyrene conversion.

  Toluene solution viscosity (Tcp) was obtained by dissolving 2.28 g of polymer in 50 ml of toluene, using a standard solution for calibrating viscometer (JIS Z8809) as a standard solution, and using a Canon Fenceke viscometer No. 400 was used and measured at 25 ° C.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the base rubber and the blend was measured according to JIS6300.

  The hardness was measured by a durometer type (type A) according to a measuring method defined in JIS-K6253.

  The tensile strength was measured with a No. 3 dumbbell at a tensile speed of 500 mm / min according to the measurement method defined in JIS-K6251.

  The Lambourn friction was measured at a slip rate of 20% 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 better).

  In the bending crack growth test, the crack length after bending 100,000 times at a stroke of 30 mm was measured according to the measurement method defined in JIS K6260.

(Examples 1-2 , Comparative Examples 1-3 )
A rubber composition was produced using the polybutadiene shown in Table 1. Table 2 shows the conditions and results.

Claims (1)

(A) Mooney viscosity synthesized using a cobalt-based catalyst is 55 to 65, and the ratio (Tcp / ML _{1 + 4} ) of 5% toluene solution viscosity (Tcp, 25 ° C.) to Mooney viscosity (ML _{1 + 4} , 100 ° C.) is 2. 10 to 90% by weight of cis polybutadiene having a cis 1,4 content of 0.0 to 4.0 of 97% or more, and (b) cis 1,4 content other than the above (a) cis polybutadiene is 95% or more. Cis polybutadiene rubber, low cis polybutadiene rubber, natural rubber, polyisoprene rubber, emulsion polymerized styrene-butadiene rubber, ethylene propylene diene rubber, nitrile rubber, butyl rubber, chloroprene rubber, or derivatives of these rubbers consisting of 90 to 10% by weight. For 100 parts by weight of rubber component (a) + (b),
A tire polybutadiene composition comprising 1 to 100 parts by weight of carbon black (c).