RU2799596C2 - Diene rubber and rubber composition - Google Patents

Abstract

FIELD: tire rubber composition.

SUBSTANCE: composition includes a diene rubber (A) containing butadiene units and having an average molecular weight of 5000 to 50000, a solid rubber (B) representing at least one material selected from the group consisting of natural rubbers, butadiene-styrene rubbers, butadiene rubbers and isoprene rubbers, and a vulcanizing agent (D) which is sulphur. The content of the diene rubber (A) is 2 to 30 parts by mass per 100 parts by mass of the hard rubber (B), and the amount of the vulcanizing agent (D) is 0.1 to 10 parts by mass per 100 parts by mass of the hard rubber (B). Diene rubber (A) meets the requirements (i) β_avg>0, (ii) β₁₂>40, (iii )β_avg/(β₁₂-40)≤2, where β₁₂ means mol.%. 1,2-linked butadiene units and β_avg means mol.% structural units represented by the formula:

A crosslinked product obtained by crosslinking the rubber composition, a tire tread, a bead filler cord, a tire breaker and a pneumatic tire containing, at least in part, a rubber composition or a crosslinked product, are also described.

EFFECT: achievement of high levels of adhesion coefficient with wet road surface and coefficient of adhesion with ice, as well as high mechanical properties.

10 cl, 2 tbl, 27 ex

Description

Technical field

[0001]

The present invention relates to a diene rubber, a rubber composition comprising a diene rubber, a crosslinked product comprising a rubber composition, and a tire tread, a bead filler cord, a tire breaker and a pneumatic tire which at least partially comprise a rubber composition or a crosslinked product. The present invention also relates to a resin modifier comprising a diene rubber.

State of the art

[0002]

Pneumatic tires, such as, in particular, all-season tires, winter tires and non-studded tires, as required, must not only have mechanical properties such as abrasion resistance, hardness and strength, but also simultaneously must satisfy high levels of other characteristics, such as efficiency. wet grip (wet grip coefficient) and grip performance at low temperatures or on snow (ice grip coefficient).

[0003]

The wet grip coefficient is effectively increased by increasing the Tanδ value (hysteresis loss). However, increasing Tanδ by adding an additive such as resin reduces the flexibility of the rubber.

The ice grip coefficient is effectively increased by increasing the contact area between the tire and ice or snow, as well as by improving the flexibility of the tire at low temperatures. As is known in the art, flexibility can be imparted to tires by using a hard rubber having a low glass transition temperature ( _Tg ), by reducing the amount of carbon black added, by adjusting the average particle size of the carbon black to about 100 to 200 nm. or by adding a softener such as oil. Unfortunately, tires with improved traction on ice by imparting flexibility disadvantageously exhibit reduced traction on wet road surfaces. In addition, the addition of a softener such as oil leads to the problem that the softener bleeds out of the mixture over time and the rubber hardens over time, or the problem that the tensile modulus drops, causing the mechanical strength of the tires to decrease.

[0004]

In order to enhance the mechanical properties of the resulting rubber composition or the crosslinked product of the rubber composition, a filler such as carbon black or silica is usually added to the rubber composition as a rubber reinforcing filler. However, this known approach impairs processability during manufacture and is therefore accompanied by the use of a processability enhancing additive such as process oil or liquid polymer. Although the conventional processability improver provides improved processability, a problem remains that the ice grip coefficient and the wet grip coefficient cannot be simultaneously satisfied at a high level.

[0005]

Patent Document 1 describes a rubber composition that includes a coumarone-indene resin having a softening point of not more than 50°C, and describes that the ice adhesion coefficient and abrasion resistance can be improved in a balanced manner. Patent Document 2 describes a rubber composition that includes a styrene-butadiene rubber having a specific amount of bonded styrene and a specific vinyl content, a low molecular weight butadiene rubber having a specific content of cis-1,4 structures and a specific weight average molecular weight, and silicon dioxide in a specific mixing ratio, and it is described that the rubber composition acquires improved performance on ice and an increased coefficient of wet grip. Patent Document 3 describes a composition that includes a linear or branched diene elastomer obtained from at least one type of conjugated diene, and a reinforcing filler, and the elastomer contains not less than 15% of the mass. cyclic vinyl units and has a number average molecular weight of 30,000 to 350,000 g/mol, and the composition is described as gaining improvements in terms of hysteresis loss and tensile modulus.

Citation list

patent document

[0006]

Patent Document 1: JP-A-2013-139522

Patent Document 2: JP-A-2002-060549

Patent Document 3: JP-A-2006-515897

The essence of the invention

Technical task

[0007]

Although the rubber compositions described in Patent Documents 1 to 3 have improved abrasion resistance and improved various braking performance compared to conventional compositions, they are still unsatisfactory in terms of simultaneously meeting the requirements for ice grip coefficient and wet grip coefficient. and need more improvements.

[0008]

The present invention has been made in view of the circumstances discussed above. Thus, the objectives of the present invention are to provide a diene rubber that is capable of producing a crosslinked product or forming a rubber composition that has high levels of both ice grip coefficient and wet grip coefficient, to obtain a rubber composition comprising a diene rubber, to provide a tire element derived from a rubber composition or a crosslinked product of a rubber composition, and to provide a tire comprising a rubber composition or a crosslinked product of a rubber composition, at least as part of it. Yet another object of the present invention is to provide a resin modifier that includes a diene rubber and is capable of producing a resin composition having the characteristics described above.

The solution of the problem

[0009]

After extensive research, the present inventors have found that a particular diene rubber having a relatively low molecular weight can form, together with other components, a rubber composition that, in the form of a rubber composition or a crosslinked rubber composition product, achieves both high levels of wet grip coefficient and ice adhesion coefficient. It has also been found that diene rubber is useful as a resin modifier, thus completing the present invention.

[0010]

Specifically, the present invention relates to the following items [1]-[12].

[1] A diene rubber (A) containing butadiene units and having a weight average molecular weight of 5,000 to 50,000,

and diene rubber (A) satisfies the requirements (i)-(iii), in which β ₁₂ means mol%. 1,2-linked butadiene units, and β _cp means mol%. structural units represented by formula (1) below, in both cases with respect to all butadiene units present in the diene rubber (A),

(i) _βcp >0

(ii) β ₁₂ >40

(iii) β _cp /(β ₁₂ -40)≤2

[0011]

[Chemical formula 1]

(1).

(1).

[2] The rubber composition comprising the diene rubber (A) described in [1].

[3] The rubber composition according to [2], further comprising a hard rubber (B).

[4] The rubber composition according to [2] or [3], further comprising a filler (C).

[5] A crosslinked product obtained by crosslinking the rubber composition described in any one of [2] to [4].

[6] A tire tread comprising, at least as part of a tire tread, a rubber composition as described in any one of [2] to [4] or a crosslinked product as described in [5].

[7] A side wing filler cord comprising, at least as part of a side wing filler cord, a rubber composition as described in any one of [2] to [4] or a crosslinked product as described in [5].

[8] A tire breaker including, at least as part of a tire breaker, a rubber composition as described in any one of [2] to [4] or a crosslinked product as described in [5].

[9] A pneumatic tire comprising, at least as part of a pneumatic tire, a rubber composition as described in any one of [2] to [4] or a crosslinked product as described in [5].

[10] The pneumatic tire according to [9], wherein the pneumatic tire is a winter tire or a non-studded tire.

[11] The pneumatic tire according to [9], in which the pneumatic tire is an all-season tire.

[12] A resin modifier comprising a diene rubber (A) as described in [1].

Positive effects of the invention

[0012]

The diene rubber produced in accordance with the present invention can serve as a component added to the rubber composition to enable the rubber composition or the crosslinked product of the rubber composition to achieve both high levels of wet grip and ice grip. Thus, a material using a rubber composition or a crosslinked product as part thereof is useful as a tire tread, bead filler cord, tire breaker or pneumatic tire. In addition, the resin composition including the diene rubber also has the characteristics described above, and therefore, the diene rubber can be used as a resin modifier.

Description of Embodiments

[0013]

Diene rubbers (A)

The diene rubber (A) of the present invention is a low molecular weight polymer which has a weight average molecular weight (Mw) in the range of 5,000 to 50,000, contains butadiene units, and satisfies the requirements (i) to (iii), where β ₁₂ means mol %. 1,2-linked butadiene units, and β _cp means mol%. structural units represented by the formula (1) described above, in both cases with respect to all butadiene units present in the diene rubber (A).

[0014]

(i) _βcp >0

(ii) β ₁₂ >40

(iii) β _cp /(β ₁₂ -40)≤2

[0015]

The weight average molecular weight (Mw) of the diene rubber (A) is in the range of 5,000 to 50,000 and is preferably not more than 40,000, more preferably not more than 30,000, and even more preferably not more than 20,000. The weight average molecular weight (Mw) of the diene rubber ( A) is preferably not less than 5500, more preferably not less than 6000, and even more preferably not less than 6500. In the present invention, the Mw of the diene rubber (A) is a polystyrene equivalent weight average molecular weight determined by measurement using gel permeation chromatography ( GPC (GPC)). The above Mw range of the diene rubber (A) ensures excellent process flow efficiency during production and obtains good economic efficiency, and also provides good processability when producing or using a rubber composition that includes a solid rubber (B) described later, or a resin composition, which includes resin.

[0016]

The molecular weight distribution (Mw/Mn) of the diene rubber (A) is preferably 1.0 to 20.0, more preferably 1.0 to 15.0, even more preferably 1.0 to 10.0, particularly preferred 1.0 to 5.0 and most preferably 1.0 to 2.0. When Mw/Mn is in the above range, the resulting diene rubber (A) advantageously has little change in viscosity. Molecular weight distribution (Mw/Mn) is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) measured by GPC against standard polystyrenes.

[0017]

The diene rubber (A) includes butadiene units as monomer units constituting the polymer. In a preferred embodiment of diene rubber (A) butadiene units are not less than 50% of the mass. all the monomer units that make up the polymer. The content of butadiene units is preferably from 60 to 100% of the mass. and more preferably from 70 to 100% of the mass. all monomer units in the diene rubber (A). In this case, the content of butadiene units can be determined taking into account such a factor as compatibility with solid rubber (B). When, for example, butadiene rubber, isoprene rubber or natural rubber are present as a component of the hard rubber (B), it is preferable that the total content of butadiene units is 100% by mass.

[0018]

Examples of additional monomer units that may be present in the diene rubber (A) in addition to butadiene units include conjugated diene units (a1) other than butadiene and aromatic vinyl compound units (a2).

[0019]

Examples of conjugated dienes (a1) other than butadiene include isoprene, 2,3-dimethylbutadiene, 2-phenylbutadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3- octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, myrcene and chloroprene. Of these conjugated dienes (a1), isoprene is preferred.

[0020]

Examples of aromatic vinyl compounds (a2) include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2,4- dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)-styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, N, N-diethyl-4- aminoethylstyrene, vinylpyridine, 4-methoxystyrene, monochlorostyrene, dichlorostyrene and divinylbenzene. Of these aromatic vinyl compounds, styrene, α-methylstyrene and 4-methylstyrene are preferred.

[0021]

The content of additional monomeric units other than butadiene units in the diene rubber (A) is preferably not more than 50% by mass, more preferably not more than 40% by mass. and even more preferably not more than 30% of the mass.

[0022]

The diene rubber (A) necessarily includes the structural units represented by the formula (1) below, that is, mol %. structural units represented by the formula (1) below, (β _cp mol %) is necessarily greater than 0 mol %. (β _cp >0) with respect to all butadiene units (requirement (i)).

[0023]

[Chemical formula 2]

(1)

(1)

[0024]

As a result, a diene rubber (A) including such structural units, a rubber composition that includes a diene rubber (A) and a hard rubber (B), or a cross-linked product that is obtained from the rubber composition can simultaneously satisfy the requirements for ice adhesion coefficient and wet grip coefficient. To improve the coefficient of adhesion with ice and the coefficient of adhesion with wet road surface β _cp mol %. is preferably not less than 0.5 mol%. (β _cp ≥0.5) and more preferably not less than 0.8 mol%. (β _cp ≥0.8). Usually β _cp mol %. is not more than 30 mol%. (β _cp ≤30). The mole percentage (mol %) of the structural units represented by formula (1) can be calculated from the ratio of the peak area attributed to the structural units of formula (1) to the peak area attributed to other butadiene units (1,2-bonded butadiene units, 1 ,4-linked butadiene units), according to ¹ H-NMR. The mole percentage (mol %) (β _cp mol %) of the structural units represented by formula (1) in the diene rubber (A) can be adjusted to a desired value, for example, by selecting the types of solvents and optional polar compound used in the production diene rubber (A), or by controlling production conditions such as polymerization temperature, monomer (butadiene) concentration, and the feed rate at which monomer is fed continuously or intermittently into the polymerization system.

[0025]

The mole percentage (mol %) (β ₁₂ mol %) of 1,2-linked butadiene units relative to all butadiene units in the diene rubber (A) is greater than 40 mol%. (β ₁₂ >40) (requirement (ii)). A rubber composition that includes a diene rubber (A) having such a content of 1,2 bonds together with a solid rubber (B) or a crosslinked product obtained from the rubber composition is of interest in that the Tanδ of the rubber composition is increased and excellent wet grip and ice grip coefficient. From the point of view of improving the coefficient of adhesion with wet road surface and the coefficient of adhesion with ice β ₁₂ mol%. is preferably not less than 42 mol%. (β ₁₂ ≥42). From the point of view of workability β ₁₂ mol%. is preferably not more than 80 mol%. (β ₁₂ ≤80) and more preferably not more than 70 mol%. (β ₁₂ ≤70). The mole percentage (mol %) of 1,2-linked butadiene units can be calculated from the ratio of the peak area attributed to 1,2-linked butadiene units to the peak area attributed to other butadiene units (1,4-linked butadiene units, structural units , represented by formula (1)), according to ¹ H-NMR. The mole percentage (mol %) (β ₁₂ mol %) of 1,2-linked butadiene units in the diene rubber (A) can be adjusted to the desired value, for example, by choosing the types of solvent and optional polar compound used in the production of the diene rubber (A), or by controlling production conditions such as polymerization temperature.

[0026]

In diene rubber (A) β _{12 mol} %. and β _cp % mol. necessarily satisfy the requirement β _cp /(β ₁₂ -40)≤2 (requirement (iii)).

As described above, high mol%. (e.g. greater than 40 mol %) of 1,2 bonds in the butadiene units present in the diene rubber (A) results in a high _{Tg of} the liquid rubber and therefore increases the _{Tg of} the rubber composition to which the rubber is added to as a result, the coefficient of adhesion with ice and the coefficient of adhesion with wet road surfaces increase. In order to ensure that the crosslinked product of the rubber composition comprising the hard rubber (B) and the low molecular weight diene rubber will exhibit improved ice grip and wet grip, the Tanδ value of the crosslinked product should be high over a wide temperature range of -20 to 30°C. Increased Tanδ values of such a cross-linked product throughout the above wide temperature range are difficult to obtain by simply increasing the mol %. 1,2 bonds in the diene rubber, and the introduction of structural units represented by formula (1) into the diene rubber (A) plays an important role. If, on the other hand, the structures of formula (1) are present in the diene rubber (A) in a large proportion, the rubber composition comprising the diene rubber (A) and the hard rubber (B) gives a crosslinked product which exhibits an exceptionally high elastic modulus and which cannot achieve the desirable properties such as flexibility and hardness expected from the characteristics of a hard rubber (B). Studies have shown that whether a crosslinked product achieves the desired properties such as flexibility and hardness while still exhibiting improved ice traction and wet traction is critically affected by the mol % ratio. structural units represented by formula (1), to an excess of mol%. 1,2-bonds, over 40%. If 1,2-bonds have an increased mol%. relative to mol%. structural units of formula (1) in diene rubber (A), and when the rubber composition including such diene rubber (A) and hard rubber (B) is subjected to a crosslinking process, the diene rubber (A) is subjected to crosslinking at such an increased speed that the obtained the crosslinked product typically has a high degree of crosslinking. On the other hand, the structural units of formula (1) give the highest glass transition temperature among other structural units derived from butadiene, and are less easily crosslinked than other butadiene units. Probably as a result of the presence of these two types of structures in a particular ratio, Tanδ values can be high over a wide temperature range from -20 to 30°C, while still providing the proper degree of crosslinking.

[0027]

To ensure that the crosslinked product that is obtained will achieve further increases in ice grip and wet grip, β _cp /(β ₁₂ -40) has a value preferably not greater than 1.8 (β _cp /(β ₁₂ -40)≤1.8), more preferably not more than 1.5 (β _cp /(β ₁₂ -40)≤1.5), particularly preferably not more than 0.7 (β _cp /(β ₁₂ - 40)≤0.7), and β _cp /(β ₁₂ -40) most preferably has a value of no more than 0.4 (β _cp /(β ₁₂ -40) ≤ 0.4).

[0028]

The melt viscosity of the diene rubber (A) measured at 38°C is preferably 0.1 to 2000 Pa⋅s, more preferably 0.1 to 1500 Pa⋅s, even more preferably 0.1 to 1000 Pa⋅s , also preferably 0.1 to 500 Pa.s, also more preferably 0.1 to 250 Pa.s, particularly preferably 0.1 to 100 Pa.s and most preferably 0.1 to 50 Pa.s. When the melt viscosity of the diene rubber (A) is in the above range, the rubber composition comprising such a diene rubber and the hard rubber (B) described later shows increased flexibility and hence exhibits improved processability. The melt viscosity of the diene rubber (A) can be adjusted to a desired value, for example, by adjusting the Mw and Mw/Mn of the diene rubber (A). In the present invention, the diene rubber melt viscosity (A) means a value measured with a Brookfield viscometer at 38°C.

[0029]

The glass transition temperature (T _article ) diene rubber (A) is preferably not more than 0°C. T _article is a variable depending on factors such as mol%. 1,2 bonds (and 3,4 bonds) in butadiene units and units of a conjugated diene (a1) other than butadiene, the type of conjugated diene (a1) and the content of units derived from monomers other than conjugated dienes. In terms of abrasion resistance, ice grip coefficient and rolling resistance characteristic, T _st is more preferably not more than -10°C, even more preferably not more than -20°C, even more preferably not more than -30°C, also preferably not more than -40°C, also more preferably not more than -50°C, particularly preferably not more than -60°C and most preferably not more than -70°C. In terms of steering stability performance, dry grip coefficient and wet grip coefficient, the T _st of the diene rubber (A) is preferably not less than -100°C, more preferably not less than -90°C, still more preferably not less than -70°C, also preferably not less than -60°C, particularly preferably not less than -40°C and most preferably not less than -20°C.

[0030]

The diene rubber (A) is obtained by polymerizing butadiene and optionally an additional monomer other than butadiene, for example, by an emulsion polymerization method or a solution polymerization method.

[0031]

The emulsion polymerization method may be a known method or a method considered to be known. For example, monomers containing a prescribed amount of a conjugated diene may be emulsified and dispersed in the presence of an emulsifier and may be emulsion polymerized using a polymerization initiator.

[0032]

Examples of emulsifiers include salts of long chain fatty acids having 10 or more carbon atoms and rosin salts. Examples of long chain fatty acid salts include potassium salts and sodium salts of fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, oleic acid and stearic acid.

[0033]

Typically, water is used as the dispersion medium. The dispersion medium may include a water-soluble organic solvent such as methanol or ethanol, as long as the stability during polymerization does not deteriorate.

Examples of radical polymerization initiators include persulfate salts such as ammonium persulfate and potassium persulfate, organic peroxides, and hydrogen peroxide.

[0034]

A chain transfer agent can be used to control the molecular weight of the diene rubber (A) that is produced. Examples of chain transfer agents include mercaptans such as t-dodecylmercaptan and n-dodecylmercaptan; carbon tetrachloride, thioglycolic acid, diterpene, terpinolene, γ-terpinene and α-methylstyrene dimer.

[0035]

The emulsion polymerization temperature may be appropriately selected depending on, for example, the type of radical polymerization initiator used. The temperature is usually in the range from 0 to 100°C and preferably in the range from 0 to 60°C. The polymerization mode may be continuous or batchwise.

[0036]

The polymerization reaction can be stopped by adding a polymerization terminating agent. Examples of polymerization termination agents include amine compounds such as isopropylhydroxylamine, diethylhydroxylamine and hydroxylamine, quinone type compounds such as hydroquinone and benzoquinone, and sodium nitrite.

[0037]

After stopping the polymerization reaction, the addition of an antioxidant may follow, if required. After stopping the polymerization reaction, the resulting latex is purified from unreacted monomers, if required, and the diene rubber (A) is coagulated by adding a coagulating salt such as sodium chloride, calcium chloride or potassium chloride, optionally together with an acid such as nitric acid or sulfuric acid, to control the pH of the coagulated system at a given value. The dispersion medium is then separated, whereby the polymer is recovered. The polymer is then washed with water, dehydrated and dried. Thus, diene rubber (A) can be obtained. During the coagulation process, the latex can be mixed together with the emulsified extender oil dispersion, if required, and the diene rubber (A) can be recovered as an oil-filled rubber.

[0038]

The method of polymerization in solution may be a known method or a method that is considered known. For example, monomers comprising a conjugated diene are solvent polymerized with a Ziegler catalyst, a metallocene catalyst, or an active metal or active metal compound capable of catalyzing the anionic polymerization, optionally in the presence of a polar compound if desired.

[0039]

Examples of solvents include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane and isooctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane and methylcyclopentane; and aromatic hydrocarbons such as benzene, toluene and xylene.

[0040]

Examples of active metals capable of catalyzing anionic polymerization include alkali metals such as lithium, sodium and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium and barium; and rare earth metals, lanthanides such as lanthanum and neodymium. Of the active metals capable of catalysing the anionic polymerization, alkali metals and alkaline earth metals are preferred, and alkali metals are more preferred.

[0041]

Preferred active metal compounds that are capable of catalyzing the anionic polymerization are organic alkali metal compounds. Examples of organic alkali metal compounds include organo-monolithium compounds such as methyl lithium, ethyl lithium, n-butyl lithium, sec-butyl lithium, t-butyl lithium, hexyl lithium, phenyl lithium and stilbene lithium; polyfunctional organolithium compounds such as dilithiomethane, dilithionaphthalene, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane and 1,3,5-trilithiobenzene; sodium naphthalene and potassium naphthalene. Of these organic alkali metal compounds, organolithium compounds are preferred, and organomonolithium compounds are more preferred.

[0042]

The amount in which the organic alkali metal compound is used can be properly determined depending on factors such as the melt viscosity and the molecular weight of the diene rubber (A). Typically, the amount of such a compound is from 0.01 to 3 mass.h. per 100 wt.h. all monomers, including the conjugated diene.

[0043]

The organic alkali metal compound can be used in the form of an organic alkali metal amide by being reacted with a secondary amine such as dibutylamine, dihexylamine or dibenzylamine.

[0044]

In anionic polymerization, a polar compound is usually used to control the microstructures of the conjugated diene units (for example, 1,2-linked butadiene units, 1,4-linked butadiene units and vinylcyclopentane (VCP) structures represented by formula (1)), without deactivation reactions. Examples of polar compounds include ethers such as dimethyl ether, diethyl ether, tetrahydrofuran and 2,2-di(2-tetrahydrofuryl)propane (DTHFP); glycol ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether; amines such as triethylamine, N,N,N',N'-tetramethylenediamine, N,N,N',N'-tetramethylethylenediamine (TMEDA) and N-methylmorpholine; and metal salts such as sodium or potassium salts of aliphatic alcohols, including sodium t-butyrate, sodium t-amylate and sodium isopentylate, and sodium or potassium salts of alicyclic alcohols, including dialkyl sodium cyclohexanolates, for example sodium mentholate. These polar compounds may be used alone, or two or more compounds may be used in combination. The polar compound is usually used in an amount of 0.01 to 1000 mol per mol of organic alkali metal compound (polymerization initiator). To promote falling β ₁₂ mol%. (% mol. 1,2-linked butadiene units) in the desired range, satisfying at least requirement (ii), the polar compound is preferably used in an amount of from 0.1 to 1000 mol, more preferably from 0.1 to 2 mol , even more preferably 0.1 to 1 mol and also preferably 0.1 to 0.9 mol per mol of the organic alkali metal compound.

[0045]

To reduce β _cp mol %. (mol % of structural units represented by formula (1)) and ensure that at least the requirement of (iii) is met, the anionic polymerization is preferably carried out so that the monomer is not depleted in the polymerization system during monomer supply, and is more preferably carried out with successive feeding of the monomer until the monomer is completely fed. In the case of sequential feeding, the feed rate of butadiene, in particular with respect to 1 mol of initiator, is preferably not less than 0.1 mol/min, more preferably not less than 0.3 mol/min, and even more preferably not less than 0.5 mol /min In order to facilitate control of the polymerization temperature during the anionic polymerization, the feed rate during butadiene sequential feeding is preferably not more than 50 mol/min, and more preferably not more than 10 mol/min, relative to 1 mol of initiator.

[0046]

The solution polymerization temperature is typically in the range -80 to 150°C, preferably 0 to 100°C, and more preferably 10 to 90°C. The polymerization mode may be batch or continuous.

[0047]

The polymerization reaction can be stopped by adding a polymerization terminating agent. Examples of polymerization termination agents include alcohols such as methanol and isopropanol. The diene rubber (A) can be isolated by pouring the polymerization reaction liquid into a poor solvent such as methanol to precipitate the diene rubber (A), or by washing the polymerization reaction liquid with water, followed by separation and drying.

Of the production methods for the diene rubber (A) described above, the solution polymerization method is preferable.

[0048]

In the diene rubber (A), the content of catalyst residues attributed to the polymerization catalyst used in rubber production is preferably in the range of 0 to 200 ppm in terms of metal. When, for example, the polymerization catalyst used for the production of diene rubber (A) is an organic alkali metal derivative such as an organolithium compound, the metal in terms of which the residue content of the catalyst is determined is an alkali metal such as lithium. The above catalyst residue content ensures that tack reduction during processing or the like is avoided and that the rubber composition of the present invention, which will be described below, will produce crosslinked products achieving improvement in terms of heat resistance and tire rolling resistance performance. The content of catalyst residues attributed to the polymerization catalyst used in the production of diene rubber (A) is more preferably 0 to 150 ppm, and even more preferably 0 to 100 ppm in terms of metal. The content of catalyst residues can be measured, for example, using a Zeman-polarized atomic absorption spectrophotometer.

[0049]

For example, the content of catalyst residues in the diene rubber (A) can be controlled within the specific range described above by purifying the diene rubber (A) to sufficiently remove catalyst residues. The cleaning method is preferably washing with water or warm water, an organic solvent such as methanol or acetone, or supercritical liquid carbon dioxide. From an economic point of view, the number of washing operations is preferably 1 to 20 and more preferably 1 to 10. The washing temperature is preferably 20 to 100°C and more preferably 40 to 90°C. Before the polymerization reaction, the monomers may be purified by distillation or by using an absorbent to remove impurities that would inhibit polymerization. Such purification makes it possible to carry out the polymerization with a reduced amount of polymerization catalyst, thus making it possible to reduce the content of catalyst residues. From a similar point of view, the content of catalyst residues in the rubber composition of the present invention described below, which includes solid rubber (B), diene rubber (A) and filler (C), is preferably from 0 to 200 ppm, more preferably from 0 up to 150 ppm and even more preferably from 0 to 100 ppm in terms of metal. In this case, the content of catalyst residues may include the content of catalyst residues attributed to the polymerization catalyst used in the production of solid rubber (B), diene rubber (A) and/or other components optionally used in the rubber composition.

[0050]

The diene rubber (A) thus obtained can be used directly, or it can be used after the unsaturated bonds in the diene rubber (A) have been reacted with a modifying agent. The diene rubber (A) can be used after at least some of the unsaturations have been hydrogenated.

[0051]

The diene rubbers (A) may be used alone, or two or more may be used in combination.

[0052]

Rubber compositions

The rubber composition of the present invention includes a diene rubber (A). Due to the content of diene rubber (A), the rubber composition shows excellent performance. When, in particular, the rubber composition comprises a hard rubber (B) and a filler (C) described later, the rubber composition or the crosslinked product of the rubber composition achieve both high levels of wet grip coefficient and ice grip coefficient, and also have excellent mechanical properties. properties.

[0053]

Hard rubbers (B)

The rubber composition of the present invention may further include a solid rubber (B). The solid rubber (B) used in the present invention is a rubber that can be handled as a solid at 20°C. The Mooney viscosity ML ₁₊₄ of the solid rubber (B) at 100° C. is typically in the range of 20 to 200. Such rubber is typically selected from at least one of synthetic rubbers and natural rubbers.

[0054]

Examples of the solid rubbers (B) include synthetic rubbers such as styrene-butadiene rubbers (hereinafter also referred to as "SBR"), butadiene rubbers, isoprene rubbers, butyl rubbers, halogenated butyl rubbers, ethylene-propylene-diene rubbers, butadiene- acrylonitrile copolymer rubbers, chloroprene rubbers, acrylate rubbers, fluoroelastomers and urethane rubbers; and natural rubbers. Of these solid rubbers (B), natural rubbers, SBRs, butadiene rubbers and isoprene rubbers are preferred, and natural rubbers, butadiene rubbers and SBRs are more preferred. The hard rubbers (B) may be used alone, or two or more may be used in combination.

[0055]

In order to ensure that the rubber composition and the resulting crosslinked products will fully exhibit their characteristics, the Mw of the solid rubber (B) is preferably not less than 80,000, and more preferably is in the range of 100,000 to 3,000,000.

[0056]

Considering that the rubber composition of the present invention is used as snow tire treads (winter tires, non-studded tires) or all-season tire treads, the glass transition temperature (T _g ) of the solid rubber (B) measured by differential thermal analysis, is not more than -10°C, preferably not more than -20°C, more preferably not more than -30°C, even more preferably not more than -40°C, also preferably not more than -45°C, especially preferably not more than -50°C and most preferably not more than -55°C. When the glass transition temperature is in this range, the rubber composition becomes more flexible at low temperatures and hence the ice adhesion coefficient is increased. In this case, the _{Tg of} the solid rubber (B) is the glass transition temperature of the rubber component substantially constituting the solid rubber (B). When, for example, the solid rubber (B) includes a plurality of rubber components, the glass transition temperatures of the plurality of rubber components substantially forming the solid rubber (B) each have a value of not more than -10°C. In the case where, for example, the rubber components substantially forming the solid rubber (B,) are STR20 (natural rubber from Thailand) and butadiene rubber, the glass transition temperatures of STR20 and butadiene rubber have a value of not more than -10°C.

[0057]

SBR can be any such rubber commonly used in the tire field. Specifically, those rubbers having a styrene content of 0.1 to 70% by mass are preferred, and more preferably the styrene content is 5 to 60% by mass, even more preferably 5 to 50% by mass, also preferably 5 up to 40% wt., particularly preferably from 5 to 30% wt. and most preferably from 5 to 25% of the mass. In addition, rubbers having a vinyl content of 0.1 to 80 wt% are preferred, and those having a vinyl content of 5 to 70 wt% are more preferred.

[0058]

The content of vinyl in the SBR in the present description means the content containing the vinyl group of the monomer units relative to all derived from butadiene units found in the SBR. Similarly, the vinyl content of the solid rubber (B) described later means the content of monomer units that actually have a vinyl group relative to the total amount of monomer units that may have a vinyl group, depending on the linking pattern.

[0059]

Preferably, the Mw SBR is from 100,000 to 2,500,000, more preferably from 150,000 to 2,000,000, and even more preferably from 150,000 to 1500,000. coating and improved mechanical strength, abrasion resistance and steering stability characteristics.

[0060]

The temperature T _St BSC measured by differential thermal analysis is not more than -10°C, preferably not more than -20°C, more preferably not more than -30°C, even more preferably not more than -40°C , also preferably not more than -45°C, particularly preferably not more than -50°C and most preferably not more than -55°C. When the glass transition temperature is in this range, the rubber composition becomes more flexible at low temperatures and hence the ice adhesion coefficient is increased.

[0061]

SBR can be obtained by copolymerization of styrene and butadiene. The production method of SBR is not limited, and any of emulsion polymerization, solution polymerization, gas phase polymerization, and bulk polymerization can be used. Of these production methods, emulsion polymerization and solution polymerization are preferred.

[0062]

Emulsion-polymerized styrene-butadiene rubber (hereinafter also referred to as E-SBR) can be produced by a conventional emulsion polymerization method. For example, such rubber can be obtained by emulsifying and dispersing given amounts of styrene and butadiene monomers in the presence of an emulsifier and emulsifying the monomers with a radical polymerization initiator.

[0063]

Examples of emulsifiers that can be used include salts of long chain fatty acids having 10 or more carbon atoms and rosin salts. Specific examples include potassium salts and sodium salts of fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, oleic acid and stearic acid.

[0064]

As a rule, water is used as the dispersion medium. The dispersion medium may include a water-soluble organic solvent such as methanol or ethanol, as long as the stability during polymerization does not deteriorate.

Examples of radical polymerization initiators include persulfate salts such as ammonium persulfate and potassium persulfate, organic peroxides, and hydrogen peroxide.

[0065]

A chain transfer agent can be used to control the molecular weight of the resulting E-BSK. Examples of chain transfer agents include mercaptans such as t-dodecylmercaptan and n-dodecylmercaptan; carbon tetrachloride, thioglycolic acid, diterpene, terpinolene, γ-terpinene and α-methylstyrene dimer.

[0066]

The emulsion polymerization temperature may be appropriately selected depending on the type of radical polymerization initiator used. In general, the temperature is preferably 0 to 100°C, and more preferably 0 to 60°C. The polymerization mode may be continuous or batchwise. The polymerization reaction can be stopped by adding a polymerization terminating agent.

[0067]

Examples of polymerization termination agents include amine compounds such as isopropylhydroxylamine, diethylhydroxylamine and hydroxylamine; quinone type compounds such as hydroquinone and benzoquinone; and sodium nitrite.

[0068]

After stopping the polymerization reaction, the addition of an antioxidant may follow, if required. After stopping the polymerization reaction, the resulting latex is stripped of unreacted monomers, if required, and the polymer is coagulated by adding a coagulating salt such as sodium chloride, calcium chloride or potassium chloride, optionally together with an acid such as nitric acid or sulfuric acid, to control the pH. coagulated system at a given value. The dispersion medium is then separated and, as a result, the polymer is isolated in crumb form. The crumb is washed with water, then dehydrated and dried using a belt dryer or similar equipment to obtain E-BSK. During the coagulation process, the latex may be mixed with the emulsified extender oil dispersion, if desired, and the rubber may be recovered as oil-filled rubber. It should be noted that in the present description, the extension oil is not considered as a component of the hard rubber (B) in the rubber composition.

[0069]

Examples of commercially available E-SBRs include "JSR1723" oil-filled styrene-butadiene rubber manufactured by JSR Corporation.

Solution-polymerized styrene-butadiene rubber (hereinafter also referred to as P-SBR (S-SBR)) can be produced by a conventional solution polymerization method. For example, styrene and butadiene are polymerized in a solvent with an active metal capable of catalyzing the anionic polymerization, optionally in the presence of a polar compound if desired.

[0070]

Examples of solvents include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane and isooctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane and methylcyclopentane; and aromatic hydrocarbons such as benzene and toluene. As a rule, it is preferable to use the solvent in such an amount that the monomer concentration is from 1 to 50 wt%.

[0071]

Examples of active metals capable of catalyzing anionic polymerization include alkali metals such as lithium, sodium and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium and barium; and rare earth lanthanides such as lanthanum and neodymium. Of these active metals, alkali metals and alkaline earth metals are preferred, and alkali metals are more preferred. Of the alkali metals, it is more preferable to use organic alkali metal compounds.

[0072]

Examples of organic alkali metal compounds include organo-monolithium compounds such as n-butyl lithium, sec-butyl lithium, t-butyl lithium, hexyl lithium, phenyl lithium and stilbene lithium; polyfunctional organolithium compounds such as dilithiomethane, 1,4-dilithiobutane, 1,4-dilithio-2-ethyl-cyclohexane and 1,3,5-trilithiobenzene; sodium naphthalene and potassium naphthalene. In particular, organolithium compounds are preferred, and organomonolithium compounds are more preferred. The amount in which the organic alkali metal compound is used may be appropriately determined depending on the desired molecular weight of P-BSA. The organic alkali metal compound can be used in the form of an organic alkali metal amide by being reacted with a secondary amine such as dibutylamine, dihexylamine or dibenzylamine.

[0073]

Polar compounds are not particularly limited as long as these compounds do not deactivate the anionic polymerization reaction, and are generally used to control the microstructure of the butadiene units and control the distribution of styrene in the copolymer chains. Examples include ether compounds such as tetrahydrofuran and ethylene glycol diethyl ether; tertiary amines such as N, N, N', N'-tetramethylethylenediamine and trimethylamine; alkali metal alkoxides; and phosphine compounds.

[0074]

The temperature of the polymerization reaction usually lies in the range from -80 to 150°C, preferably from 0 to 100°C and more preferably from 30 to 90°C. The polymerization mode may be batch or continuous. In order to increase the random copolymerizability of styrene and butadiene, it is preferable to supply styrene and butadiene to the reaction liquid continuously or intermittently so that styrene and butadiene in the polymerization system have a specific composition ratio.

[0075]

The polymerization reaction can be stopped by adding an alcohol such as methanol or isopropanol as a polymerization terminating agent. After stopping the polymerization reaction, the target P-BSA can be isolated by separating the solvent from the polymerization solution by methods such as direct drying or steam stripping. The polymerization solution may be mixed together with the extender oil before the solvent is removed, and the rubber may be recovered as an oil-filled rubber.

[0076]

As long as the positive effects of the invention will not be weakened, the BSC may be a modified BSC obtained by introducing functional groups into the BSC. Examples of functional groups include amino groups, alkoxysilyl groups, hydroxyl groups, epoxy groups, and carboxyl groups.

[0077]

For example, modified SBR can be produced by adding, prior to the addition of the termination agent, an agent capable of reacting with the active ends of the polymer, for example, a coupling agent such as tin tetrachloride, tetrachlorosilane, dimethyldichlorosilane, dimethyldiethoxysilane, tetramethoxysilane, tetraethoxysilane, 3-aminopropyltriethoxysilane , tetraglycidyl-1,3-bisaminomethylcyclohexane or 2,4-toluene diisocyanate; an end-modifying agent such as 4,4'-bis(diethylamino)benzophenone or N-vinyl-pyrrolidone, or any of the modifying agents described in JP-A-2011-132298. In the modified BSC, functional groups can be introduced at the ends of the polymer or into the side chains of the polymer.

[0078]

Examples of isoprene rubbers that can be used include commercially available isoprene rubbers polymerized with a Ziegler catalyst such as titanium tetrahalide-trialkylaluminum systems, diethylaluminum chloride-cobalt systems, trialkylaluminum-boron trifluoride-nickel systems, and diethylaluminum chloride-nickel systems; rare earth lanthanide catalysts such as triethylaluminum-organic neodymium-Lewis acid systems; or organic alkali metal compounds, similar to R-BSK. Ziegler-catalyzed isoprene rubbers are preferred because they have a high cis content. Ultra-high cis isoprene rubbers made using rare earth lanthanide catalysts can be used.

[0079]

The content of vinyl in isoprene rubbers is preferably not more than 50% by mass, more preferably not more than 40% by mass. and even more preferably not more than 30% of the mass. If the vinyl content exceeds 50% by mass, the rolling resistance characteristics are generally degraded. The lower limit of the vinyl content is not particularly limited. The glass transition temperature, although variable and dependent on the vinyl content, is preferably not greater than -20°C and more preferably not greater than -30°C.

[0080]

Preferably, the Mw of isoprene rubbers is from 90,000 to 2,000,000 and more preferably from 150,000 to 1,500,000. This Mw provides high processability and mechanical strength.

[0081]

As long as the positive effects of the present invention are not impaired, isoprene rubbers may have branched substructures or polar functional groups, which are introduced through the use of polyfunctional modifiers, for example, tin tetrachloride, silicon tetrachloride, alkoxysilanes having an epoxy group in the molecule, or alkoxysilanes containing an amino group.

[0082]

Examples of butadiene rubbers that can be used include commercially available butadiene rubbers polymerized with Ziegler catalysts such as titanium tetrahalide-trialkylaluminum systems, diethylaluminum chloride-cobalt systems, trialkylaluminum-boron trifluoride-nickel systems, and diethylaluminum chloride-nickel systems; rare earth metal lanthanide catalysts such as triethylaluminum-organic acid neodymium-Lewis acid systems; or organic alkali metal compounds similar to P-BSK. Ziegler-catalyzed butadiene rubbers are preferred because they have a high cis content. Ultra-high cis butadiene rubbers (eg, 95% or more cis) produced using rare earth lanthanide catalysts can be used.

[0083]

The content of vinyl in butadiene rubbers is preferably not more than 50% by weight, more preferably not more than 40% by weight. and even more preferably not more than 30% of the mass. If the vinyl content exceeds 50% by mass, rolling resistance performance (low fuel consumption performance) and abrasion resistance tend to deteriorate. The lower limit of the vinyl content is not particularly limited. The glass transition temperature, although variable and dependent on the vinyl content, is preferably not greater than -40°C and more preferably not greater than -50°C.

[0084]

Preferably, the Mw of butadiene rubbers is 90,000 to 2,000,000, and more preferably, 150,000 to 1,500,000. and steering stability characteristics.

[0085]

As long as the positive effects of the invention are not impaired, butadiene rubbers may have branched partial structures or polar functional groups, which are introduced through the use of polyfunctional modifiers, for example, tin tetrachloride, silicon tetrachloride, alkoxy-silanes having an epoxy group, or containing the amino group of alkoxysilanes.

[0086]

At least one of BBR, isoprene rubbers and butadiene rubbers can be used in combination with one or two or more of, for example, butyl rubbers, halogenated butyl rubbers, ethylene-propylene-diene rubbers, butadiene-acrylonitrile copolymer rubbers and chloroprene rubbers. . Such rubbers may be produced by any means without limitation, or commercial products may be used.

[0087]

Examples of natural rubbers include natural rubbers, high purity natural rubbers, and modified natural rubbers such as epoxidized natural rubbers, halogenated natural rubbers, hydrogenated natural rubbers, and grafted natural rubbers, which are commonly used in the tire industry, specific examples include TSR (technically specified rubbers) such as SMR (TSR from Malaysia), SIR (TSR from Indonesia) and STR (TSRs from Thailand), and RSS (grooved smoked sheets). In particular, SMR 20, STR 20 and RSS #3 are preferred in terms of quality uniformity and high availability. The natural rubbers may be used alone, or two or more may be used in combination. In the present invention, synthetic rubbers and natural rubbers can be used together.

[0088]

When the rubber composition includes diene rubber (A) and solid rubber (B), the content of diene rubber (A) is preferably 0.1 to 50 parts by mass. relative to 100 mass.h. solid rubber (B) and more preferably 0.1 to 45 mass, even more preferably 0.5 to 40 mass, also preferably 1 to 40 mass, also more preferably 2 up to 40 wt.h., particularly preferably from 2 to 30 wt.h. and most preferably from 2 to 20 wt.h. When the content of the diene rubber (A) is in the above range, the crosslinked product which is obtained achieves excellent wet grip and ice grip without exuding the diene rubber (A) from the hard rubber (B).

When the rubber composition also contains a filler (C), the above range of diene rubber (A) content ensures that the filler (C) will have good dispersibility in the rubber composition and the crosslinked product that is obtained will simultaneously have high levels of wet grip. road surface and ice adhesion coefficient, and will also have good mechanical properties.

[0089]

Fillers (C)

The rubber composition of the present invention may include a filler (C). The filler (C) used in the rubber composition of the present invention is not limited. For purposes such as improving properties, such as mechanical properties, and improving dry grip, wet grip, steering stability performance, and low fuel consumption performance of tires incorporating the rubber composition as parts thereof, at least least preferred is a filler selected from carbon blacks and silicas. In a preferred embodiment, the composition includes carbon black as a filler (C). In another preferred embodiment, the composition includes silica as a filler (C). In another preferred embodiment, the composition comprises carbon black and silica as fillers (C).

[0090]

Examples of carbon blacks include furnace blacks, gas channel blacks, thermal blacks, acetylene blacks, and Ketjen blacks. From the viewpoint of improving the crosslinking speed, improving the mechanical strength of the crosslinked products that are obtained, and improving the dry grip coefficient, the wet grip coefficient, the steering stability performance and the low fuel consumption performance of tires including the rubber composition as their parts, furnace blacks are preferred among the above carbon blacks. The carbon blacks may be used alone, or two or more may be used in combination.

[0091]

In order to achieve an improvement in the dry grip coefficient, the wet grip coefficient and the low fuel consumption performance of the tires including the rubber composition as parts thereof, the average particle diameter of the carbon black particles is preferably not less than 5 nm, more preferably not less than than 10 nm and even more preferably not less than 15 nm, and is preferably not more than 100 nm, more preferably not more than 80 nm, even more preferably not more than 70 nm, and particularly preferably not more than 60 nm. The average particle diameter of carbon black can be determined by measuring particle diameters using a transmission electron microscope and calculating the average diameter.

[0092]

Examples of commercially available furnace blacks include "DIABLACK" manufactured by Mitsubishi Chemical Corporation and "SEAST" manufactured by Tokai Carbon Co., Ltd. Examples of commercially available acetylene blacks include "DENKA BLACK" manufactured by Denka Company Limited. Examples of commercially available Ketjen black grades include "ECP600JD" manufactured by Lion Specialty Chemicals Co., Ltd.

[0093]

In order to achieve enhancement of properties such as wettability and dispersibility with respect to hard rubber (B), carbon blacks may be treated with acids such as nitric acid, sulfuric acid, hydrochloric acid and mixed acids of these acids, or may be subjected to a surface oxidation treatment by heating in the presence of air. To improve the mechanical strength of the claimed rubber composition and cross-linked products obtained from the composition, carbon black can be treated at a temperature of 2000 to 3000°C in the presence of a graphitization catalyst. Preferred examples of graphitization catalysts are boron, boron oxide (eg B ₂ O ₂ , B ₂ O ₃ , B ₄ O ₃ and B ₄ O ₅ ), boron oxoacids (eg orthoboric acid, metaboric acid and tetraboric acid) and salts thereof. , boron carbides (eg B ₄ C and B ₆ C), boron nitride (BN) and other boron compounds.

[0094]

Carbon blacks can be used after their grain size has been adjusted by a method such as crushing. Examples of pulverizers that can be used to crush carbon black include high-speed impact crushers (hammer mills, pin mills, and basket mills), a variety of ball mills (rotary mills, vibratory mills, and planetary mills), and mixing mills (bead mills, attritors, mills). flow type and ring mills).

[0095]

Examples of silicas include wet silicas (hydrosilicates), dry silicas (silicic anhydrides), calcium silicates, and aluminosilicates. Of these silicas, wet silicas are preferred to achieve further improvements in processability, mechanical strength, and abrasion resistance of the crosslinked products that are produced, as well as dry grip coefficient, wet grip coefficient, steering stability performance, and low consumption performance. fuel for tires, including the rubber composition in the form of their parts. The silicas may be used alone, or two or more may be used in combination.

[0096]

In order to improve the processability of the rubber composition and the dry grip coefficient, the wet grip coefficient and the low fuel consumption performance of tires including the rubber composition as parts thereof, the average particle diameter of the silica particles is preferably not less than 0.5 nm. , more preferably not less than 2 nm, even more preferably not less than 5 nm, particularly preferably not less than 8 nm and most preferably not less than 10 nm, and is preferably not more than 200 nm, more preferably not more than 150 nm , even more preferably not more than 100 nm, also preferably not more than 50 nm, particularly preferably not more than 30 nm and most preferably not more than 20 nm. The average silica particle diameter can be determined by measuring particle diameters using a transmission electron microscope and calculating the average diameter.

[0097]

Of the carbon blacks and silicas described above, silicas are more preferred as fillers (C) in terms of, for example, enhancing the rolling resistance performance of the resulting rubber composition and its crosslinked products.

In the present invention, the rubber composition may include a filler other than silicas and carbon blacks for purposes such as improving the mechanical strength of tires incorporating the rubber composition as parts thereof and improving manufacturing costs by adding filler as a cost-saving additive.

[0098]

Examples of fillers other than silicas and carbon blacks include organic fillers and inorganic fillers such as clays, talcs, mica, calcium carbonate, magnesium hydroxide, aluminum hydroxide, barium sulfate, titanium oxides, glass fibers, fibrous fillers, and glass beads. Such excipients may be used alone, or two or more may be used in combination.

[0099]

When the rubber composition of the present invention includes a diene rubber (A), a hard rubber (B), and a filler (C), the content of the filler (C) is preferably 20 to 200 parts by mass. per 100 wt.h. hard rubber (B). When the amount of the filler (C) is in this range, the tires including the rubber composition as parts thereof show improvement in dry grip coefficient, wet grip coefficient and low fuel consumption performance. From the point of view discussed above, the amount of filler (C) per 100 mass.h. solid rubber (B) is more preferably not less than 30 mass, even more preferably not less than 40 mass, also preferably not less than 50 mass. and especially preferably not less than 60 mass, and is preferably not more than 150 mass, more preferably not more than 120 mass, even more preferably not more than 100 mass, even more preferably not more than 90 mass, also preferably not more than 80 mass. and especially preferably not more than 70 mass.h.

[0100]

When the rubber composition of the present invention includes diene rubber (A), solid rubber (B) and filler (C), and when silica is used as filler (C), the amount of silica per 100 mass.h. solid rubber (B) is preferably not less than 20 mass, more preferably not less than 25 mass, even more preferably not less than 30 mass, also preferably not less than 35 mass, particularly preferably not less than 40 mass.h. and most preferably not less than 45 mass, and is preferably not more than 100 mass, more preferably not more than 90 mass, even more preferably not more than 80 mass, even more preferably not more than 70 mass, also preferably not more than 65 mass, particularly preferably not more than 60 mass. and most preferably not more than 55 parts by mass from the point of view of improving the dry grip coefficient, the wet grip coefficient and the low fuel consumption performance of the tires including the rubber composition as parts thereof.

[0101]

When the rubber composition of the present invention includes diene rubber (A), solid rubber (B) and filler (C), and when carbon black is used as filler (C), the amount of carbon black per 100 mass.h. solid rubber (B) is preferably not less than 10 mass, more preferably not less than 20 mass, even more preferably not less than 30 mass. and especially preferably not less than 40 mass, and is preferably not more than 120 mass, more preferably not more than 100 mass, even more preferably not more than 80 mass, even more preferably not more than 70 mass, also preferably not more than 60 mass, particularly preferably not more than 55 mass. and most preferably not more than 50 parts by mass from the viewpoint of improving the dry grip coefficient, the wet grip coefficient and the low fuel consumption performance of the tires including the rubber composition as parts thereof.

[0102]

When silica and carbon black are used in combination, the ratio of silica to carbon black (weight ratio=silica/carbon black) is preferably 1:99 to 99:1, more preferably 10:90 to 90:10, and even more. preferably from 30:70 to 80:20.

[0103]

Additional components

When the rubber composition of the present invention includes silica or the like as filler (C), it is preferable that the composition also contains a silane coupling agent. Examples of silane coupling agents include sulfide compounds, mercapto compounds, vinyl compounds, amino compounds, glycidoxy compounds, nitro compounds, and chlorine compounds.

[0104]

Examples of sulfide compounds include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis( 3-trimethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)-disulfide, bis(3-trimethoxysilylpropyl)disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-trimethoxy -silylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazoletetrasulfide, 3-triethoxysilylpropylbenzothiazoletetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide and 3-octanoylthio-1-propyltriethoxysilane.

[0105]

Examples of mercapto compounds include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane.

[0106]

Examples of vinyl compounds include vinyltriethoxysilane and vinyltrimethoxysilane.

Examples of amino compounds include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane and 3-(2-aminoethyl)aminopropyltrimethoxysilane.

[0107]

Examples of glycidoxy compounds include γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycidoxypropylmethyldimethoxysilane.

[0108]

Examples of nitro compounds include 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane.

Examples of chlorine compounds include 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane and 2-chloroethyltriethoxysilane.

Other compounds may be used, examples of which include octyltriethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, and hexadecyltrimethoxysilane.

[0109]

The silane coupling agents may be used alone, or two or more may be used in combination. Of the above silane coupling agents, sulfur-containing silane coupling agents such as sulfide compounds and mercapto compounds are preferred due to their high reinforcing effects, and bis(3-triethoxysilylpropyl)disulfide, bis(3-triethoxysilylpropyl)tetrasulfide and 3- mercaptopropyltrimethoxysilane.

[0110]

The silane coupling agent is preferably added in an amount of 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass. and even more preferably from 1 to 15 wt.h. per 100 wt.h. filler (C). This content of the silane coupling agent ensures that dispersibility, bonding effects, reinforcing effects and abrasion resistance are enhanced.

[0111]

The rubber composition of the present invention may further contain a vulcanizing agent (D) for cross-linking the rubber in the composition. Examples of vulcanizing agents (D) include sulfur and sulfur compounds. Examples of sulfur compounds include morpholine disulfides and alkylphenol disulfides. Vulcanizing agents (D) may be used alone or two or more may be used in combination. When the rubber composition of the present invention includes a diene rubber (A) and a hard rubber (B), the vulcanizing agent (D) is usually added in an amount of 0.1 to 10 parts by mass, preferably 0.5 to 10 parts by mass. and more preferably from 0.8 to 5 wt.h. per 100 wt.h. hard rubber (B) in terms of the mechanical properties of the crosslinked products.

[0112]

When, for example, the rubber composition of the present invention contains a vulcanizing agent (D) for crosslinking (vulcanizing) rubber, the composition may further include a vulcanization accelerator (E). Examples of the vulcanization accelerators (E) include guanidine series compounds, sulfenamide compounds, thiazole compounds, thiuramic compounds, thiourea compounds, dithiocarbamic acid compounds, aldehyde-amine compounds, aldehyde-ammonia compounds, imidazoline compounds and xanthate compounds. The vulcanization accelerators (E) may be used alone or two or more may be used in combination. When the rubber composition of the present invention includes a diene rubber (A) and a hard rubber (B), the vulcanization accelerator (E) is usually added in an amount of 0.1 to 15 parts by mass. and preferably from 0.1 to 10 wt.h. per 100 wt.h. hard rubber (B).

[0113]

When, for example, the rubber composition of the present invention contains sulfur, a sulfur compound or the like. as a vulcanizing agent (D) for crosslinking (vulcanizing) rubber, the composition may further include a vulcanization aid (F). Examples of vulcanization aids (F) include fatty acids such as stearic acid, metal oxides such as zinc oxide, and metal salts of fatty acids such as zinc stearate. The vulcanization aids (F) may be used alone or two or more may be used in combination. When the rubber composition of the present invention includes a diene rubber (A) and a hard rubber (B), the vulcanization aid (F) is usually added in an amount of 0.1 to 15 parts by mass. and preferably from 1 to 10 wt.h. per 100 wt.h. hard rubber (B).

[0114]

In addition to vulcanizing agents, crosslinking agents may be added to the rubber composition. Examples of crosslinkers include oxygen, organic peroxides, phenolic resins, amino resins, quinone and quinone dioxime derivatives, halogen compounds, aldehyde compounds, alcohol compounds, epoxy compounds, metal halides, organometallic halides, and silane compounds. They may be used alone or two or more may be used in combination. When the rubber composition of the present invention includes a diene rubber (A) and a hard rubber (B), the amount of the crosslinking agent is preferably 0.1 to 10 parts by mass. per 100 wt.h. hard rubber (B).

[0115]

When necessary, the rubber composition of the present invention may include, for example, a softener to achieve improvements in properties such as processability and flowability, while still ensuring that the benefits of the present invention are not impaired. Examples of softeners include process oils such as silicone oils, aromatic oils, TDAE (purified distilled aromatic extracts), MES (low extraction solvates), RAE (residual aromatic extracts), paraffin oils and naphthenic oils, and resin components such as aliphatic hydrocarbons. resins, alicyclic hydrocarbon resins, C ₉ resins, rosin resins, coumarone-indene resins and phenolic resins. When the rubber composition of the present invention contains a process oil as a softener and also includes a diene rubber (A) and a hard rubber (B), the content of the softener in terms of sweat resistance is preferably not more than 50 parts by mass, more preferably not more than 30 wt.h. and even more preferably not more than 15 wt.h. per 100 wt.h. hard rubber (B).

[0116]

The rubber composition of the present invention may contain additives, if required, to achieve improvement in properties such as weather resistance, heat resistance and oxidation resistance, while still achieving the positive effects of the present invention. Examples of such additives include antioxidants, oxidation inhibitors, waxes, lubricants, light stabilizers, scorch retardants, processing aids, colorants such as pigments and colorants, flame retardants, antistatic agents, matting agents, release agents, UV absorbers, mold release agents, foaming agents. , antibacterial agents, anti-mould agents and fragrances.

[0117]

Examples of oxidation inhibitors include hindered phenolic compounds, phosphorus compounds, lactone compounds and hydroxyl compounds.

Examples of antioxidants include amine ketone compounds, imidazole compounds, amine compounds, phenolic compounds, sulfur compounds and phosphorus compounds. The additives may be used alone or two or more may be used in combination.

[0118]

Method for the production of rubber compositions

The rubber composition of the present invention can be produced by any method, without limitation, as long as the components described above can be mixed together homogeneously. Examples of devices used in the production of rubber composition include closed kneaders with tangential or intermeshing rotors such as coarse kneaders, Brabender mixers, Banbury mixers and closed kneaders, single screw extruders, twin screw extruders, mixing rolls and rolls. The production of the rubber composition can usually be carried out at a temperature in the range from 50 to 270°C.

[0119]

The rubber composition of the present invention is preferably used as a crosslinked product (vulcanized rubber). Conditions and vulcanization methods are not particularly limited, but the composition is preferably vulcanized with a vulcanization mold under conditions where the vulcanization temperature is 120 to 200°C and the vulcanization pressure is 0.5 to 20 MPa.

[0120]

The cross-linked products are preferably such that the diene rubber (A) is extracted therefrom with a recovery factor of not more than 20% by mass, more preferably not more than 15% by mass. and even more preferably not more than 10% of the mass.

The recovery factor can be calculated by soaking 2 g of the crosslinked product in 400 ml of toluene at 23° C. for 48 hours and determining the amount of diene rubber (A) extracted into toluene.

[0121]

Tire treads and pneumatic tires

The tire tread of the present invention includes, at least as part of it, the rubber composition described in the invention, and usually the rubber composition contains a diene rubber (A), a hard rubber (B) and a filler (C), or a cross-linked product obtained by crosslinking the rubber composition. Such a tire tread has sufficient dry grip plus excellent wet grip and ice grip, and exhibits outstanding steering stability characteristics. The tire tread structure of the present invention is not particularly limited, and may be a single layer structure or a multilayer structure. In the case of a multilayer structure, the rubber composition is preferably used in the layer which is in contact with the roadbed.

[0122]

The pneumatic tire of the present invention includes, at least in part, the rubber composition described above, and usually the rubber composition contains a diene rubber (A), a solid rubber (B) and a filler (C), or a crosslinked product obtained by crosslinking rubber composition, and is, in particular, preferably a pneumatic tire, including the tire tread described above. The pneumatic tire of the present invention, by virtue of containing the rubber composition as a part thereof, has sufficient dry grip plus excellent wet grip and ice grip, and exhibits improved steering stability characteristics and outstanding abrasion resistance. Thus, pneumatic tires are suitable as tires for driving on snow, such as winter tires and non-studded tires, as well as all-season tires.

[0123]

Examples of tire parts in which the rubber composition and the cross-linked products of the rubber composition can be used include treads (tread tread, undertreads), sidewalls, rubber reinforcement layers (such as liners) for self-supporting tires, rim pads, bead filler cords, insulation sidewalls, bead fenders, trim ring wings, belts (tire breakers), belt pads, undertreads, undertread pads, bead tapes, bead tape liners and tape tops.

[0124]

Resin modifiers

In view of the excellent characteristics described above, the diene rubber (A) of the present invention can also be used as a resin modifier. A resin modifier including a diene rubber (A) can be used as a resin composition by being mixed with a resin.

[0125]

The above resin is not particularly limited and may be, for example, a thermosetting resin or a thermoplastic resin. Examples of thermoplastic resins include olefin resins, styrene resins, polyphenylene ether resins, polycarbonate resins, polyamide resins, isobutylene-isoprene copolymer rubbers, and polyurethane thermoplastic elastomers. Such thermoplastic resins may be used alone, or two or more may be used in combination. The resin composition may include a variety of additives, if desired.

[0126]

The resin composition can be prepared in any of a variety of ways, without limitation. When, for example, the resin is a thermoplastic resin, the resin composition can be prepared, for example, by mixing a resin modifier including diene rubber (A), thermoplastic resins, and optionally various additives using a mixing machine such as a Henkel mixer, or by kneading in melt this mixture by heating using a kneading machine such as a single screw extruder, twin screw extruder, rubber mixer, Banbury mixer or rolls. On the other hand, a resin composition can be obtained by dissolving a resin modifier including diene rubber (A), a thermoplastic resin and optionally various additives in a solvent capable of dissolving these materials, and then removing the solvent.

[0127]

The resin composition is useful in a variety of applications such as, for example, pressure sensitive adhesives, adhesives, and vibration isolation materials.

Examples

[0128]

The present invention is described in more detail based on the following examples. However, it should be understood that the scope of the present invention is not limited to such examples.

[0129]

The following components are used in the examples and comparative examples.

Diene rubbers (A)

Polymers (A-1) to (A-4) obtained in Production Examples 1-4 are described later.

Hard rubbers (B)

Natural rubber (NR) STR20 (from Thailand): manufactured by VON BUNDIT CO., LTD., T _st -62.6°C.

Butadiene rubber (BR): BR01 (manufactured by JSR Corporation, high cis type (95% 1,4-cis bonds), weight average molecular weight 520,000, _Tg -103°C.

Fillers (C)

Carbon black: DIABLACK I (N220) (manufactured by Mitsubishi Chemical Corporation, average particle diameter 20 nm).

Silica: ULTRASIL 7000GR (manufactured by Evonik Degussa Japan, wet silica, average particle diameter 14 nm).

Optional Components

Silane Coupling Agent

SI75 (manufactured by Evonik Degussa Japan).

Vulcanizing agent

Sulfur: MUCRON OTRET-20 (manufactured by SHIKOKU CHEMICALS CORPORATION).

Auxiliary additives for vulcanization

Stearic acid: LUNAC S-20 (manufactured by Kao Corporation).

Zinc oxide: Zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.).

Vulcanization accelerators

Vulcanization accelerator (1): Sanceler NS (manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD.).

Vulcanization accelerator (2): Nocceler D (manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.).

Antioxidants

Antioxidant (1): Nocrac 6C (manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.).

Antioxidant (2): ANTAGE RD (manufactured by Kawaguchi Chemical Industry Co., LTD.).

Other components

TDAE: VivaTec 500 (manufactured by H&R).

Wax: SUNTIGHT S (manufactured by Seiko Chemical Co., Ltd.).

[0130]

The properties of the diene polymers obtained in the production examples described later were measured and calculated by the following methods.

[0131]

Weight average molecular weight, number average molecular weight and molecular weight distribution

The measurements are carried out using the instrument "HLC-8320" manufactured by TOSOH CORPORATION. The concentration is sample/tetrahydrofuran = 5 mg/10 ml. Tetrahydrofuran manufactured by Wako Pure Chemical Industries, Ltd. is used as the developing solution.

The weight average molecular weight (Mw) and the number average molecular weight (Mn) are determined by GPC (Gel Permeation Chromatography) against standard polystyrenes, and the molecular weight distribution (Mw/Mn) is calculated from these values. Use the following measuring instruments and measurement conditions.

Measuring instruments and measuring conditions

Instrument: GPC instrument “HLC-8320” manufactured by TOSOH CORPORATION

Separator column: TSKgel Super HZM-M column manufactured by TOSOH CORPORATION

Eluent: Tetrahydrofuran

Eluent flow rate: 0.7 ml/min

Sample concentration: 5 mg/10 ml

Column temperature: 40°C

[0132]

Glass transition temperature (T _st )

Place 10 mg of sample in an open aluminum tray, which is then closed with an aluminum cap and crimped with a sample seal. The thermogram is measured using differential scanning calorimetry (DSC (DSC)) at a heating rate of 10°C/min, and the value at the top of the DSC peak is taken as the glass transition temperature (T _st ). Use the following measuring instruments and measurement conditions.

Measuring instruments and measuring conditions

Instrument: DSC6200 differential scanning calorimeter manufactured by Seiko Instruments Inc.

Cooling unit: Cooling controller manufactured by Seiko Instruments Inc.

Detector: by heat flux

Sample weight: 10 mg

Heating rate: 10°C/min

Cooling Conditions: The temperature is reduced at a rate of 10°C/min, kept constant at -130°C for 3 minutes, and then raised.

Control container: Aluminum

Control mass: 0 mg

[0133]

β ₁₂ and β _cp

A solution of 50 mg of the diene polymer obtained in the production example in 1 ml of deuterated chloroform (CDCl ₃ ) was analyzed by ¹ H-NMR at 400 MHz. The total number of scans is 512. Based on the integrals of the areas described below, the graph obtained by measurement, β ₁₂ (mol. % of 1,2-linked butadiene units) and β _cp (mol. % of structural units represented by formula (1) ) is determined as follows.

Region 4.65-5.22 ppm: Region A (synthetic spectrum attributed to 1,2 bonds and structural units represented by formula (1))

Section 5.22-5.68 ppm: Section B (synthetic spectrum of 1,2-bonds and 1,4-bonds)

Plot 5.68-5.95 ppm: Plot C (spectrum attributed to structural units represented by formula (1))

β ₁₂ =[(integral of segment A - integral of segment B × 2)/2]/[(integral of segment A - integral of segment C × 2)/2 + [integral of segment C - (integral of segment A - integral of segment C × 2) /2]/2+integral of segment C] × 100

β _cp = integral of section C/{(integral of section A - integral of section C × 2)/2 + [integral of section C - (integral of section A - integral of section C × 2)/2]/2 + integral of section C} × 100

[0134]

Production of diene polymers (A)

Production example 1: Diene polymer (A-1)

A pressure-resistant container that has been purged with nitrogen and dried is charged with 1320 g of cyclohexane as solvent and 66.4 g of n-butyllithium (1.6 mol/l solution in hexane) as polymerization initiator. The temperature is raised to 50°C. Then, 4.3 g of N, N, N', N'-tetramethyl-ethylenediamine (TMEDA) (0.2 mol per mol of polymerization initiator) are added, and a mixed solution containing 1320 g of butadiene, which was prepared in advance, is also added , at a feed rate of 12.5 ml/min (feed rate of butadiene per mole of polymerization initiator 0.9 mol/min). The polymerization is carried out for 1 hour. 7.1 g of methanol was added to the resulting polymerization reaction solution to stop the polymerization. The polymerization reaction solution was washed with 2 L of water. After washing, the polymerization reaction solution was separated from water and dried under reduced pressure at 70° C. for 12 hours to obtain a polymer (A-1). The properties of the resulting polymer are described in Table 1.

[0135]

Production example 2: Diene polymer (A-2)

A pressure-resistant container that has been purged with nitrogen and dried is charged with 1380 g of cyclohexane as solvent and 109.2 g of n-butyllithium (1.6 mol/l solution in hexane) as polymerization initiator. The temperature is raised to 50°C. Then, 13.2 g of tetrahydrofuran (THF) (0.7 mol per mol of polymerization initiator) is added, and a mixed solution containing 1000 g of butadiene, which was prepared in advance, is also added at a feed rate of 12.5 ml/min (butadiene feed rate per mol of polymerization initiator 0.5 mol/min). The polymerization is carried out for 1 hour. To the resulting polymerization reaction solution, 10.6 g of methanol was added to stop the polymerization. The polymerization reaction solution was washed with 2 L of water. After washing, the polymerization reaction solution was separated from water and dried under reduced pressure at 70° C. for 12 hours to obtain a polymer (A-2). The properties of the resulting polymer are described in Table 1.

[0136]

Production example 3: Diene polymer (A-3)

A pressure-resistant container that has been purged with nitrogen and dried is charged with 1500 g of cyclohexane as solvent and 152.9 g of n-butyllithium (1.6 mol/l solution in hexane) as polymerization initiator. The temperature is raised to 50°C. Then, 9.29 g of TMEDA (0.2 mol per mol of polymerization initiator) are added, and a mixed solution containing 1000 g of butadiene, which was prepared in advance, is also added at a feed rate of 12.5 ml/min (butadiene feed rate per mol of polymerization initiator 0.4 mol/min). The polymerization is carried out for 1 hour. To the resulting polymerization reaction solution, 14.8 g of methanol was added to stop the polymerization. The polymerization reaction solution was washed with 2 L of water. After washing, the polymerization reaction solution was separated from water and dried under reduced pressure at 70° C. for 12 hours to obtain a polymer (A-3). The properties of the resulting polymer are described in Table 1.

[0137]

Production example 4: Diene polymer (A-4)

A pressure-resistant container that has been purged with nitrogen and dried is charged with 1184 g of hexane as solvent and 45.2 g of n-butyllithium (1.6 mol/l solution in hexane) as polymerization initiator. The temperature is raised to 40°C. Then, 13.2 g of TMEDA (1 mol per mol of polymerization initiator) is added, and a mixed solution containing 1184 g of butadiene, which was prepared in advance, is also added at a feed rate of 10 ml/min (butadiene feed rate per mol of polymerization initiator 1 mol/min ). The polymerization is carried out for 1 hour. 4.8 g of methanol was added to the resulting polymerization reaction solution to stop the polymerization. The polymerization reaction solution was washed with 2 L of water. After washing, the polymerization reaction solution is separated from water and dried under reduced pressure at 70° C. for 12 hours to obtain a polymer (A-4). The properties of the resulting polymer are described in Table 1.

[0138]

Production example 5: Diene polymer (A'-5)

A pressure-resistant container that has been purged with nitrogen and dried is charged with 1184 g of hexane as solvent and 45.2 g of n-butyllithium (1.6 mol/l solution in hexane) as polymerization initiator. The temperature is raised to 40°C. Then, 13.2 g of TMEDA (1 mol per mol of polymerization initiator) are added, and a mixed solution containing 1184 g of butadiene, which was prepared in advance, is also added at a feed rate of 5 ml/min (butadiene feed rate per mol of polymerization initiator 0.5 mol /min). The polymerization is carried out for 1 hour. 4.8 g of methanol was added to the resulting polymerization reaction solution to stop the polymerization. The polymerization reaction solution was washed with 2 L of water. After washing, the polymerization reaction solution is separated from water and dried under reduced pressure at 70° C. for 12 hours to obtain a polymer (A'-5). The properties of the resulting polymer are described in Table 1.

[0139]

Production example 6: Diene polymer (A'-6)

A pressure-resistant container that has been purged with nitrogen and dried is charged with 1000 g of hexane as solvent and 28.3 g of n-butyllithium (1.6 mol/l solution in hexane) as polymerization initiator. The temperature is raised to 50°C. Then, a mixed solution containing 1000 g of butadiene, which was prepared beforehand, was added at a feed rate of 12.5 ml/min (feed rate of butadiene per mol of polymerization initiator 2 mol/min). The polymerization is carried out for 1 hour. 2.7 g of methanol was added to the resulting polymerization reaction solution to stop the polymerization. The polymerization reaction solution was washed with 2 L of water. After washing, the polymerization reaction solution is separated from water and dried under reduced pressure at 70° C. for 12 hours to obtain a polymer (A'-6). The properties of the resulting polymer are described in Table 1.

[0140]

Table 1

Production examples 1 2 3 4 5 6 A-1 A-2 A-3 A-4 A'-5 A'-6 Weight average molecular weight (Mw) 16000 7000 5000 19000 19000 27000 Molecular weight distribution (Mw/Mn) 1.02 1.03 1.04 1.03 1.05 1.03 T _st (°C) -41 -66 -49 -18 -eleven -94 β ₁₂ (1,2-bonds), mol % 63.2 45.9 55.4 53.0 46.0 9.0 βcp _, mol % 3.7 1.2 9.6 23 thirty 0 β _cp /(β ₁₂ -40) 0.16 0.20 0.62 1.8 5.0 - Monomer feed rate, ml/min 12.5 12.5 12.5 10 5 12.5 Butadiene feed rate (mol/min) per mole polymerization initiator 0.9 0.5 0.4 1 0.5 2 Initiator NBL NBL NBL NBL NBL NBL Number of moles of initiator 0.17 0.28 0.39 0.11 0.11 0.07 polar connection TMEDA THF TMEDA TMEDA TMEDA - Gram polar compound 4.3 13.2 9.29 13.2 13.2 0 Number of moles of polar compound 0.037 0.183 0.080 0.114 0.114 0 Number of moles of polar compound per mole of polymerization initiator 0.2 0.7 0.2 1 1 0

NBL initiator: n-butyllithium

[0141]

Examples 1-4 and Comparative Examples 1-3

The polymer (A), hard rubbers (B), fillers (C), vulcanization aids, silane coupling agent, antioxidants, and other components are added in the amounts (mass parts) shown in Table 2 to a Banbury internal mixer and kneaded. together for 6 min from the initial temperature of 60°C to the temperature of the resin 140°C. The kneaded mixture is then removed from the mixer and cooled to room temperature. The mixture is then placed back into the Banbury internal mixer and the vulcanizing agent and vulcanization accelerators are added. The resulting mixture is kneaded for 75 seconds from an initial temperature of 50°C to a maximum temperature of 100°C. The result is a rubber composition.

The resulting rubber compositions were subjected to compression (compression conditions: 145° C., 70 to 75 minutes) to obtain a crosslinked sheet (2 mm thick) of a crosslinked product (vulcanized rubber). Sheets are tested by the methods described below to determine the dynamic modulus and Tan δ. The results are presented in table 2.

[0142]

Ice adhesion coefficient

The stitched sheets produced in the Examples and Comparative Examples were cut to obtain test specimens 40 mm long and 5 mm wide. The test specimens are tested with a dynamic viscoelastic tester manufactured by GABO GmbH at a measuring temperature of -20°C, a frequency of 10 Hz, a static strain of 10% and a dynamic strain of 2% to determine the dynamic modulus (E') and tanδ as coefficient of adhesion with ice. The results are shown in Table 2 as absolute values and as values relative to the value of Comparative Example 3, taken as 100. The ice adhesion coefficient of the rubber composition becomes higher as the absolute value decreases and the relative value of the elastic modulus (E') increases. The ice adhesion coefficient of the rubber composition becomes higher as the absolute value increases and the relative value of Tanδ increases.

The relative values of the dynamic modulus (E') as an indicator of the coefficient of adhesion to ice are calculated using the following equation:

Relative value of dynamic modulus (E') of Example or Comparative Example = (absolute value of dynamic modulus (E') of Comparative Example 3, 8.63 MPa)/(absolute value of dynamic modulus (E') of Example or Comparative Example) × 100

Relative Tanδ (-20°C) values as an indicator of ice adhesion coefficient are calculated using the following equation:

Relative value of Tanδ (-20°C) of example or comparative example = (absolute value of Tanδ (-20°C) of example or comparative example)/(absolute value of Tanδ (-20°C) of comparative example 3, 0.44) × 100

[0143]

Wet grip coefficient

The stitched sheets produced in the Examples and Comparative Examples were cut to obtain test specimens 40 mm long and 5 mm wide. The test specimens are tested with a dynamic viscoelastic tester manufactured by GABO GmbH at a measurement temperature of 0°C, a frequency of 10 Hz, a static strain of 10%, and a dynamic strain of 2% to determine Tanδ as a measure of the wet grip coefficient. The results are shown in Table 2 as absolute values and as values relative to the value of Comparative Example 3 taken as 100. The higher the value, the higher the wet grip coefficient of the rubber composition.

The relative values of Tanδ (0°C) as an indicator of the wet grip coefficient are calculated using the following equation:

Relative value of Tanδ (0°C) as an indicator of the criterion of the coefficient of wet grip of the example or comparative example = (absolute value of Tanδ (0°C) of the example or comparative example)/(absolute value of Tanδ (0°C) of comparative example 3 , 0.31) × 100

[0144]

table 2

Examples Comparative examples 1 2 3 4 1 2 3 Recipe (wt.h. Components (A) Polymer (A-1) 10 Polymer (A-2) 10 Polymer (A-3) 10 Polymer (A-4) 10 Polymer (A'-5) 10 Polymer (A'-6) 10 Components (B) NK (NR) 70 70 70 70 70 70 70 BC (BR) thirty thirty thirty thirty thirty thirty thirty Components (C) Silica 35 35 35 35 35 35 35 carbon black 35 35 35 35 35 35 35 Optional Components Silane Coupling Agent 2.8 2.8 2.8 2.8 2.8 2.8 2.8 Sulfur 1.9 1.9 1.9 1.9 1.9 1.9 1.9 zinc oxide 3.5 3.5 3.5 3.5 3.5 3.5 3.5 Stearic acid 2 2 2 2 2 2 2 Vulcanization accelerator (1) 1 1 1 1 1 1 1 Vulcanization accelerator (2) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Antioxidant (1) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Antioxidant (2) 1 1 1 1 1 1 1 Wax 1.5 1.5 1.5 1.5 1.5 1.5 1.5 TDAE 10 10 10 10 10 10 20 Properties Ice adhesion coefficient
Dynamic modulus of elasticity (-20°C) MPa 8.84 8.09 8.49 9.29 9.64 8.56 8.63 Relative value 98 107 102 93 90 101 100 Ice adhesion coefficient
Tanδ (-20°C) - 0.44 0.45 0.47 0.46 0.46 0.43 0.44 Relative value 100 102 107 105 105 98 100

Wet grip coefficient
Tanδ (0°C) - 0.33 0.32 0.32 0.33 0.34 0.32 0.31 Relative value 106 103 103 106 110 103 100 The sum of the relative values of the coefficient of ice adhesion (dynamic modulus, Tanδ) and the coefficient of wet adhesion (Tanδ) Sum of relative values 305 312 312 304 304 302 300

NR (NR): Natural rubber, BR (BR): Butadiene rubber

[0145]

According to Table 2, the crosslinked products obtained from the rubber compositions of Examples 1-3 show an improvement in ice grip and wet grip in a balanced manner compared to the crosslinked products of Comparative Examples 1-3. Example 4 shows a high ice grip coefficient compared to Comparative Example 1, and therefore leads to an increase in the sum of the ice grip coefficient and the wet grip coefficient in a balanced manner. Since β _cp is too high, Comparative Example 1, giving an excessively high elastic modulus (-20°C), therefore has a low ice adhesion coefficient, although Tanδ (-20°C) and Tanδ (0°C) good ones. Comparative example 2 fails to achieve a sufficient increase in Tanδ (-20°C) and Tanδ (0°C) due to too low values of β ₁₂ and β _cp .

Thus, the rubber compositions of Examples 1-4 meeting the requirement of β _cp /(β ₁₂ -40) ≤ 2 are shown to have balanced ice and wet grip coefficients.

Industrial Applicability

[0146]

The diene rubber (A) of the present invention shows excellent processability when converted into a rubber composition. In addition, when the rubber is converted into a crosslinkable rubber composition by combining with a crosslinking agent (vulcanizing agent) or the like, the rubber composition or its crosslinked product simultaneously achieves high levels of wet grip coefficient and ice grip coefficient, and also exhibits excellent mechanical properties, therefore, are useful for use in tires or the like.

Claims (22)

1. Rubber composition for the production of tires, including diene rubber (A), hard rubber (B) and vulcanizing agent (D), where diene rubber (A) contains butadiene units and has a weight average molecular weight of 5000 to 20000, and diene rubber (A) satisfies the requirements (i)-(iii), where β ₁₂ means mol%. 1,2-linked butadiene units and β _cp means mol%. structural units represented by formula (1) below, in both cases with respect to all butadiene units present in the diene rubber (A), (i) _βcp >0, (ii) 70≥β ₁₂ >40, (iii) β _cp /(β ₁₂ -40)≤2, [Chemical formula 1]

the vulcanizing agent (D) is sulfur, the hard rubber (B) is at least one material selected from the group consisting of natural rubbers, styrene-butadiene rubbers, butadiene rubbers and isoprene rubbers, the content of diene rubber (A) is from 2 to 30 mass parts with respect to 100 mass parts of solid rubber (B), and the amount of vulcanizing agent (D) is from 0.1 to 10 mass parts per 100 mass parts of hard rubber (B). 2. Rubber composition according to claim. 1, in which the content of diene rubber (A) is from 2 to 20 mass parts per 100 mass parts of solid rubber (B). 3. Rubber composition according to claim 1 or 2, additionally containing a filler (C). 4. Crosslinked product obtained by crosslinking the rubber composition according to any one of paragraphs. 1-3. 5. Tire tread, containing, at least in the form of a part of the tire tread, a rubber composition according to any one of paragraphs. 1-3 or a cross-linked product according to claim 4. 6. Filler cord side wing containing, at least in the form of a filler cord side wing, rubber composition according to any one of paragraphs. 1-3 or a cross-linked product according to claim 4. 7. Tire breaker, containing, at least as part of a tire breaker, a rubber composition according to any one of paragraphs. 1-3 or a cross-linked product according to claim 4. 8. Pneumatic tire containing, at least in the form of a part of the pneumatic tire, the rubber composition according to any one of paragraphs. 1-3 or a cross-linked product according to claim 4. 9. Pneumatic tire according to claim 8, wherein the pneumatic tire is a winter tire or a non-studded tire. 10. Pneumatic tire according to claim 8, wherein the pneumatic tire is an all-season tire.