JP2004339466A - Polybutadiene composition for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polybutadiene composition used for a tire excellent in abrasion resistance and improved in flex crack development resistance. <P>SOLUTION: This polybutadiene composition for the tire is obtained by blending (c) 1-100 pts. wt. rubber-reinforcing agent to 100 pts. wt. rubber components (a)+(b) consisting of (a) 10-90 pts. wt. high cis-polybutadiene synthesized by using a cobalt-based catalyst, having 50-70 Mooney viscosity (ML) and 1.8-5.0 ratio (Tcp/ML) of 5 % toluene solution viscosity (Tcp) to the Mooney viscosity (ML), and (b) 90-10 wt. % diene-based rubber except for the above high cis-polybutadiene (a). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polybutadiene composition for tires having excellent abrasion resistance and improved flex crack growth resistance, and includes a tire outer member such as a tread / sidewall of a tire, a tire inner member such as a carcass belt / bead, and a vibration isolating rubber. It can also be used for industrial goods such as belts, hoses, and seismic isolation rubbers, and footwear such as men's shoes, women's shoes, and sports shoes.

  Polybutadiene has, as a so-called microstructure, a bonding part (1,4-structure) formed by polymerization at the 1,4-position and a bonding part (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 having a vinyl group as a side chain.

  It is known that polybutadiene having a different microstructure is produced depending on the polymerization catalyst and polymerization conditions, and is used for various purposes depending on its properties.

  For the purpose of improving the wear resistance and heat generation of tires, blending of polybutadiene rubber (BR) with natural rubber and the like has been widely performed, 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. Japanese Patent No. 247721 (Patent Document 2) discloses a 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-cutting properties and flex crack growth resistance. There is a problem that the wear resistance is reduced although it is improved.

JP-A-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.

The present invention provides (a) a Mooney viscosity synthesized using a cobalt-based catalyst of 50 to 70, and a ratio (Tcp / ML) of a 5% toluene solution viscosity (Tcp) to a Mooney viscosity (ML) of 1.8 to 5; Of the rubber component (a) + (b) consisting of 10 to 90% by weight of a high-cis polybutadiene of 1.0 and 90% to 10% by weight of (b) a diene rubber other than the above-mentioned (a) high-cis polybutadiene. ,
A polybutadiene composition for tires, comprising 1 to 100 parts by weight of a rubber reinforcing agent (c).

Further, it is preferable that the molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the high cis polybutadiene (a) is 2.5 to 3.8 and the cis content is 95% or more.

  The present invention relates to a polybutadiene composition for a tire, characterized in that a stroke is 30 mm in a flex crack growth test specified in JIS K6260 and a crack length at the time of bending 100,000 times is 5 mm or less.

  Preferably, the rubber reinforcing agent of (c) is carbon black.

  The polybutadiene composition in the present invention is composed of a rubber component and a rubber reinforcing agent containing a specific high-cis polybutadiene, and has excellent abrasion resistance. Provided.

The polybutadiene of the present invention has the following properties.
Mooney viscosity is 50-70, preferably 55-65. If the Mooney viscosity is larger than the above range, the workability is reduced, and if it is smaller than the above range, the abrasion resistance may be reduced, which is not preferable.

  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, and more preferably 2.6 to 3.2. It is. If the molecular weight distribution is larger than the above range, the abrasion resistance decreases, and if the molecular weight distribution is smaller than the above range, workability may be deteriorated, which is not preferable.

The ratio (Tcp / ML) of the 5% toluene solution viscosity (Tcp) to the Mooney viscosity (ML) is 1.8 to 5.0, preferably 2.0 to 4.0, and more preferably 2.1 to 4.0. 3.5.
When the Tcp / ML ratio is larger than the above range, the cold flow property of the raw rubber increases, and when the Tcp / ML ratio is smaller than the above range, the abrasion resistance decreases, which is not preferable.

  The cis 1.4 content is preferably at least 95%, particularly preferably at least 97%. If the cis 1.4 content is less than the above, the abrasion resistance decreases, which is not preferable.

  The above polybutadiene can be produced with a cobalt-based catalyst. Examples of the cobalt-based 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 salt or complex of cobalt 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, and bisacetylacetonate and trisacetylacetonate of cobalt. And organic base complexes such as pyridine complex and picoline complex of acetoacetate ethyl ester cobalt and cobalt salt, and ethyl alcohol complex.

  Examples of the halogen-containing aluminum include trialkyl aluminum, dialkyl aluminum chloride, dialkyl aluminum bromide, alkyl aluminum sesquichloride, alkyl aluminum sesquibromide, and alkyl aluminum dichloride.

  Specific compounds include trialkylaluminums such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, and tridecylaluminum.

  Further, dimethylaluminum chloride, dialkylaluminum chlorides such as diethylaluminum chloride, organoaluminum halides such as sesquiethylaluminum chloride, ethylaluminum dichloride, and the like, 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 from 0.7 to 5, particularly preferably from 0.8 to 4, and still more preferably from 1 to 3. It is.

  Conjugated dienes such as isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethylbutadiene, 2-methylpentadiene, 4-methylpentadiene and 2,4-hexadiene other than butadiene monomer; Acyclic monoolefins such as ethylene, propylene, butene-1, butene-2, isobutene, pentene-1, 4-methylpentene-1, hexene-1, octene-1, cyclopentene, cyclohexene and norbornene; And / or non-conjugated diolefins such as aromatic vinyl compounds such as styrene and α-methylstyrene, 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 itself such as 1,3-butadiene as a polymerization solvent or solution polymerization can be applied. Examples of the solvent in the solution polymerization include aromatic hydrocarbons such as toluene, benzene, and xylene; aliphatic hydrocarbons such as n-hexane, butane, heptane, and pentane; cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; 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 them, 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 150C, and particularly preferably in the range of 30 to 100C. The polymerization time is preferably in the range of 1 minute to 12 hours, particularly preferably 5 minutes to 5 hours.

  After the polymerization is performed for a predetermined time, the pressure inside the polymerization tank is released as necessary, and post-treatments such as washing and drying steps are 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-polymerized or solution-polymerized styrene-butadiene rubber (SBR), natural rubber, polyisoprene rubber, and ethylene. Examples include propylene diene rubber (EPDM), nitrile rubber (NBR), butyl rubber (IIR), and chloroprene rubber (CR).

  Derivatives of these rubbers, for example, polybutadiene rubber modified with a tin compound, epoxy-modified, silane-modified, maleic acid-modified rubber, and the like can also be used.These rubbers can be used alone or in combination of two or more. May be.

Examples of the rubber reinforcing agent of the component (c) of the present invention include various types of inorganic reinforcing agents such as carbon black and white carbon, activated calcium carbonate, ultrafine magnesium silicate, polyethylene resin, polypropylene resin, high styrene resin, and phenol resin. And organic reinforcing agents such as lignin, modified melamine resin, coumarone indene resin and petroleum resin.
Particularly preferred is carbon black having a particle diameter 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 such that the rubber component (a) is composed of 10 to 90% by weight of a specific high cis polybutadiene (a) and 90 to 10% by weight of a diene rubber (b) other than (a). + (B) 100 parts by weight and rubber reinforcing agent (c) 1 to 100 parts by weight.

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

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

The rubber composition of the present invention, if necessary, kneading compounding agents usually used in the rubber industry, such as a vulcanizing agent, a vulcanizing aid, an antioxidant, a filler, a process oil, zinc white, and stearic acid. May be.

As the vulcanizing agent, known vulcanizing agents, for example, 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, ammonias, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, xanthates and the like are used.

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

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 powdered rubber.

As the process oil, any of an aromatic type, a naphthenic type, and a paraffin type may be used.

  In the present invention, a polybutadiene composition for tires having a stroke of 30 mm and a crack length of 100,000 times bending of 5 mm or less in a flex crack growth test specified in JIS K6260 can be suitably provided.

  Hereinafter, examples based on the present invention will be specifically described.

Microstructure was performed by infrared absorption spectroscopy. 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 determined by dissolving 2.28 g of a polymer in 50 ml of toluene, and using a standard solution for calibration of a viscometer (JIS Z8809) as a standard solution. Measured at 25 ° C. using a 400.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the raw rubber and the compound was measured in accordance with JIS6300.

  The hardness was measured by a durometer method (type A) according to a measurement method specified 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 specified in JIS-K6251.

  The Lambourn friction was measured at a slip ratio of 20% according to the measurement method specified in JIS-K6264, and was indicated by an index with Comparative Example 1 being 100 (the larger the index, the better).

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

(Examples 1-4, Comparative Examples 1-2)
Using the polybutadiene shown in Table 1, a rubber composition was produced. Table 2 shows the conditions and results.

Claims (4)

(A) a high-viscosity liquid having a Mooney viscosity of 50-70 synthesized using a cobalt-based catalyst and a ratio (Tcp / ML) of Mooney viscosity (Tcp) to Mooney viscosity (ML) of 1.8-5.0; 100 parts by weight of a rubber component (a) + (b) comprising 10 to 90% by weight of cis polybutadiene and (b) 90 to 10% by weight of a diene rubber other than (a) high cis polybutadiene,
A polybutadiene composition for tires, comprising 1 to 100 parts by weight of a rubber reinforcing agent (c).   The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the high cis polybutadiene (a) is 1.8 to 3.8 and the cis content is 95% or more. Item 4. The polybutadiene composition for a tire according to item 1.   The polybutadiene composition for a tire according to any one of claims 1 to 2, wherein a stroke is 30 mm and a crack length when bent 100,000 times is 5 mm or less in a flex crack growth test defined in JIS K6260. The polybutadiene composition for a tire according to any one of claims 1 to 3, wherein the rubber reinforcing agent (c) is carbon black.