阅读说明：本技术 橡胶组合物 (Rubber composition ) 是由 宫崎达也 于 2019-03-11 设计创作，主要内容包括：本发明旨在提供一种橡胶组合物,该橡胶组合物提供了拉伸性能、燃料经济性和耐磨性的平衡改善。本发明涉及一种橡胶组合物,该橡胶组合物包含：橡胶组分,该橡胶组分含有二烯系橡胶；二氧化硅和/或炭黑；以及母料,该母料含有硫和酸值为5以上的树脂。(The present invention aims to provide a rubber composition that provides an improvement in the balance of tensile properties, fuel economy and abrasion resistance. The present invention relates to a rubber composition comprising: a rubber component containing a diene rubber; silica and/or carbon black; and a master batch containing sulfur and a resin having an acid value of 5 or more.)

1. A rubber composition, wherein the rubber composition comprises:

a rubber component containing a diene rubber;

at least one of silica and carbon black; and

a master batch containing sulfur and a resin having an acid value of 5 or more.

2. The rubber composition according to claim 1,

wherein the resin has an acid value of 10 to 180.

3. The rubber composition according to claim 1 or 2,

wherein the softening point of the resin is 120 ℃ or lower.

4. The rubber composition according to any one of claims 1 to 3,

wherein the total sulfur content of the rubber composition is 1.5 parts by mass or more per 100 parts by mass of the rubber component.

5. The rubber composition according to any one of claims 1 to 4.

Wherein the rubber composition contains 1.5 parts by mass or less of a thiadiazole-based vulcanization accelerator with respect to 100 parts by mass of the rubber component.

6. A masterbatch, wherein the masterbatch comprises:

sulfur; and

a resin having an acid value of 5 or more.

7. A masterbatch according to claim 6 wherein said polymer is a polymer,

wherein the masterbatch does not contain any diene rubber.

8. A method of using a master batch as an additive in rubber, wherein the master batch contains sulfur and a resin having an acid value of 5 or more.

Technical Field

The present invention relates to a rubber composition.

Background

Powdered sulfur can be mixed with paraffin oil to reduce flammability to prevent explosion and improve dispersibility in rubber. Meanwhile, aromatic oils containing aromatic compounds are known to have poor compatibility with sulfur.

Further, in order to improve the braking performance of the tire, the tread rubber needs to exhibit less deformation so that the axle stopping force can be instantaneously transmitted to the tread rubber in contact with the road surface. Therefore, the tread rubber is required to have high hardness. However, as this wavelength of elimination, such tread rubber tends to have poor tensile properties, resulting in poor resistance to rubber chipping. To solve this problem, various measures have been proposed such as a method of reducing the sulfur content while increasing the vulcanization accelerator content, a method of using a hybrid crosslinking agent in combination, and a method of reducing the sulfur content and incorporating a crosslinkable phenol resin. Other proposed methods include incorporating high-purity natural rubber or resin (e.g., terpene-based resin, rosin-based resin, or coumarone-indene resin) (see, for example, patent document 1).

List of cited documents

Patent document

Patent document l: JP 5597959B

Disclosure of Invention

Technical problem

As described above, although various methods for achieving desired rubber properties have been proposed and studied, these methods (for example, a method of reducing the sulfur content while increasing the content of a vulcanization accelerator, or a method of reducing the sulfur content while incorporating a crosslinking phenol resin, or other similar methods) tend to deteriorate wet grip properties and slow the initial vulcanization rate. The method of using the hybrid crosslinking agent in combination can maintain wet grip performance and initial vulcanization speed and improve abrasion resistance, but results in high material cost. Methods of incorporating highly purified natural rubber or resins (e.g., terpene-based resins, rosin-based resins, or coumarone-indene resins) or other similar methods tend to result in poor fuel economy and higher costs. Furthermore, the rubber properties are not improved by replacing the powdered sulfur with oil-treated sulfur or a mixture of coumarone-indene resin and sulfur. These proposed methods still do not provide satisfactory performance and further improvements are needed. In particular, there has not been any known method for improving powdered sulfur to sufficiently improve tensile properties, fuel economy and abrasion resistance at a lower cost, and such a method is desired.

The present invention aims to solve the problem and provide a rubber composition that provides an improvement in the balance of tensile properties, fuel economy and abrasion resistance.

Technical scheme

The present invention relates to a rubber composition comprising:

a rubber component containing a diene rubber;

at least one of silica and carbon black; and

a master batch containing sulfur and a resin having an acid value of 5 or more.

Preferably, the acid number of the resin is from 10 to 180.

Preferably, the softening point of the resin is 120 ℃ or lower.

Preferably, the total sulfur content of the rubber composition is 1.5 parts by mass or more with respect to 100 parts by mass of the rubber component.

Preferably, the rubber composition contains 1.5 parts by mass or less of a thiazole-based vulcanization accelerator with respect to 100 parts by mass of the rubber component.

The invention also relates to a masterbatch comprising:

sulfur; and

a resin having an acid value of 5 or more.

Preferably, the masterbatch does not contain any diene rubber.

The invention also relates to a method of using a masterbatch (which contains sulfur and a resin having an acid number of 5 or more) as an additive in rubber.

Advantageous effects of the invention

The rubber composition of the present invention comprises: a rubber component containing a diene rubber; silica and/or carbon black; and a master batch containing sulfur and a resin having an acid value of 5 or more; thus, the rubber composition of the present invention provides an improved balance of tensile properties, fuel economy and abrasion resistance.

Detailed Description

The rubber composition of the present invention comprises: a rubber component containing a diene rubber; silica and/or carbon black; and a master batch containing sulfur and a resin having an acid value of 5 or more. The use of a master batch containing sulfur and a resin having an acid value of 5 or more improves tensile properties and fuel economy as compared with a rubber composition prepared by mixing only sulfur and a resin. Thus, the rubber composition of the present invention provides an improved balance of tensile properties, fuel economy and abrasion resistance.

Although unclear, the reason why the above effect is produced seems to be as follows.

When a master batch containing sulfur and a resin having an acid value of 5 or more is prepared in advance, sulfur in the master batch and carboxyl groups in the resin interact through ionic bonds, thereby forming a uniform mixture of the resin and sulfur. Then, sulfur is more easily dispersed in a rubber composition prepared by kneading such a master batch with a rubber component and other components, as compared with a rubber composition in which only powdered sulfur is mixed. Furthermore, even under oxidative degradation conditions, sulfur is less likely to re-aggregate. Thus, a rubber composition providing an improved balance of tensile properties, fuel economy and abrasion resistance can be obtained.

The rubber component contains a diene rubber.

Examples of the diene rubber include: isoprene rubber, polybutadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene monomer rubber (EPDM), Chloroprene Rubber (CR), and nitrile rubber (NBR). These may be used alone, or two or more of these may be used in combination. The rubber component preferably contains isoprene-based rubber, BR and/or SBR, more preferably contains BR and/or SBR, and particularly preferably contains a combination of BR and SBR.

The rubber component may further contain other rubbers than the diene-based rubber as long as the rubber component contains the diene-based rubber. Examples of such other rubbers include butyl rubber and fluororubber.

The amount of the diene rubber is preferably 70% by mass or more, more preferably 80% by mass or more, and further more preferably 90% by mass or more, based on 100% by mass of the rubber component, and the amount of the diene rubber may be 100% by mass. When the amount of the diene rubber is within the above range, the effect of the present invention can be suitably achieved.

Examples of the isoprene-based rubber include Natural Rubber (NR), polyisoprene rubber (IR), modified NR and modified IR. NR may be one commonly used in the tire industry, such as SIR20, RSS #3, or TSR 20; IR may be one commonly used in the tire industry, such as IR 2200. Examples of the modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR). Examples of the modified NR include Epoxidized Natural Rubber (ENR), Hydrogenated Natural Rubber (HNR), and grafted natural rubber. Examples of the modified IR include epoxidized polyisoprene rubber, hydrogenated polyisoprene rubber and grafted polyisoprene rubber. These rubbers may be used alone, or two or more of these may be used in combination.

The amount of the isoprene-based rubber (if present) is preferably 5% by mass or more, more preferably 10% by mass or more, based on 100% by mass of the rubber component. The amount of the isoprene-based rubber is preferably 50% by mass or less, and more preferably 30% by mass or less. With this amount, good grip performance can be achieved.

Non-limiting examples of BR include those commonly used in the tire industry, such as BR having a high cis content, BR containing 1, 2-syndiotactic polybutadiene crystals (SPB-containing BR), polybutadiene rubber synthesized using a rare earth catalyst (rare earth-catalyzed BR), and tin-modified polybutadiene rubber that has been modified with a tin compound (tin-modified BR). Commercial products of BR include products of Utsuki Kaisha, JSR Kaisha, Asahi Kaisha, Nippon Kaisha and Lanxess. These may be used alone, or two or more of these may be used in combination.

The cis content of BR is preferably 80 mass% or more, more preferably 85 mass% or more, further more preferably 90 mass% or more, and particularly preferably 95 mass% or more. With such a cis content, better wear resistance can be achieved.

The cis content herein is determined by infrared absorption spectroscopy.

The BR can be unmodified BR or modified BR.

The modified BR can be any BR having functional groups that interact with the filler (e.g., silica). Examples include: chain-end-modified BR obtained by modifying at least one chain end of BR with a compound (modifier) having any of the following functional groups (chain-end-modified BR terminated with any of the following functional groups); a main chain-modified BR having a main chain having any of the following functional groups; a main chain-modified chain-end-modified BR having any of the following functional groups at both the main chain and the chain ends (for example, a main chain-modified chain-end-modified BR having any of the following functional groups at the main chain and at least one chain end modified with a compound (modifier) having any of the following functional groups); and chain end-modified BR which has been modified (or coupled) with a polyfunctional compound having two or more epoxy groups in the molecule to introduce a hydroxyl group or an epoxy group.

Examples of functional groups include: amino (preferably amino in which the hydrogen atom of the amino group is substituted with a C1-C6 alkyl group), amide, silyl, alkoxysilyl (preferably C1-C6 alkoxysilyl), isocyanate, imino, imidazolyl, ureido, ether, carbonyl, oxycarbonyl, mercapto, thio, disulfide, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imido, hydrazono, azo, diazo, carboxyl, cyano, pyridyl, alkoxy (preferably C1-C6 alkoxy), hydroxyl, oxy, and epoxy. These functional groups may be substituted.

In particular, BR is preferably rare earth catalyzed BR because it provides good durability and abrasion resistance while ensuring good tensile properties and fuel economy.

The rare earth-catalyzed BR can be conventional BR, examples including those using rare earth catalysts (catalysts including lanthanide rare earth compounds, organoaluminum compounds, aluminoxanes or halogen-containing compounds, optionally containing Lewis bases). Among them, polybutadiene rubber (Nd-catalyzed BR) synthesized using a neodymium (Nd) catalyst including a neodymium-containing compound as a lanthanoid rare earth compound is preferable.

In order to more suitably obtain the effects of the present invention, the glass transition temperature (Tg) of BR is preferably-160 ℃ or higher, more preferably-130 ℃ or higher, and further preferably-60 ℃ or lower, more preferably-90 ℃ or lower.

The glass transition temperature herein was measured with a differential scanning calorimeter (Q200 available from TA Instruments Japan Inc.) at a temperature rising rate of 10 ℃/min in accordance with JIS-K7121.

The amount of BR (if present) is preferably 5% by mass or more, more preferably 10% by mass or more, and further more preferably 15% by mass or more, based on 100% by mass of the rubber component. The amount of BR is preferably 80% by mass or less, more preferably 70% by mass or less, further preferably 50% by mass or less, and particularly preferably 30% by mass or less. When the amount of BR is within the above range, sufficient mechanical strength and abrasion resistance can be obtained.

Non-limiting examples of SBR include those commonly used in the tire industry, such as emulsion polymerized SBR (E-SBR) and solution polymerized SBR (S-SBR). These may be used alone, or two or more of these may be used in combination.

Commercial products of SBR include products manufactured or sold by sumitomo chemical corporation, JSR corporation, asahi chemical corporation and japanese ruing corporation.

The SBR may be an unmodified SBR or a modified SBR. Examples of the modified SBR include those in which the functional group described for the modified BR is introduced.

The SBR may be an oil-extended SBR or a non-oil-extended SBR. When the oil-extended SBR is used, the oil-extended amount of the SBR (i.e., the amount of the extended oil in the SBR) is preferably 10 to 50 parts by mass with respect to 100 parts by mass of the rubber solid content of the SBR, in order to more appropriately achieve the effect of the present invention.

The styrene content of SBR is preferably 5% by weight or more, more preferably 10% by weight or more, and further preferably 15% by weight or more. The styrene content is preferably 60% by weight or less, more preferably 50% by weight or less, still more preferably 45% by weight or less, and particularly preferably 40% by weight or less. When the styrene content is within the above range, the effects of the present invention can be more suitably achieved.

Styrene content of SBR herein is determined by¹H-NMR analysis determination.

In order to more suitably obtain the effect of the present invention, the vinyl content of SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and further preferably 20 mol% or more. The vinyl group content is preferably 70 mol% or less, more preferably 65 mol% or less, and still more preferably 50 mol% or less.

Vinyl content in this context means by¹H-NMR analysis of the vinyl content (number of vinyl units in the butadiene structure) of the butadiene portion was determined.

In order to more suitably obtain the effects of the present invention, the glass transition temperature (Tg) of SBR is preferably-90 ℃ or higher, more preferably-50 ℃ or higher. The Tg is also preferably 0 ℃ or lower, more preferably-10 ℃ or lower.

The glass transition temperature herein was measured with a differential scanning calorimeter (Q200 available from TA Instruments Japan Inc.) at a temperature rising rate of 10 ℃/min in accordance with JIS-K7121.

In order to more suitably obtain the effects of the present invention, the weight average molecular weight (Mw) of the SBR is preferably 200,000 or more, more preferably 250,000 or more, further more preferably 300,000 or more, and particularly preferably 1,000,000 or more. The Mw is also preferably 2,000,000 or less, more preferably 1,800,000 or less.

The weight average molecular weight (Mw) herein can be determined by Gel Permeation Chromatography (GPC) (GPC-8000 series available from Toso Co., Ltd., detector: differential refractometer, column: TSKGEL SUPERMALPORE HZ-M available from Toso Co., Ltd.), which is calibrated with polystyrene standards.

The amount of SBR (if present) is preferably 20 mass% or more, more preferably 30 mass% or more, further more preferably 50 mass% or more, and further more preferably 70 mass% or more, based on 100 mass% of the rubber component. The amount of SBR is preferably 95% by mass or less, and more preferably 90% by mass or less. When the amount of SBR is within the above range, sufficient abrasion resistance, grip performance and reversion resistance can be obtained.

Here, the amount of SBR means the amount of solid content of SBR as measured with respect to the solid content of the rubber present in the entirety being 100 mass%.

The total amount of BR and SBR is preferably 80% by mass or more, more preferably 90% by mass or more, and further more preferably 95% by mass or more, based on 100% by mass of the rubber component, and the total amount of BR and SBR may be 100% by mass. By making the total amount of BR and SBR within the above range, the effects of the present invention can be more suitably achieved.

The master batch contains sulfur and a resin having an acid value of 5 or more. Incorporation of such a masterbatch into a rubber composition makes it possible to improve tensile properties and fuel economy, as compared with a rubber composition prepared by mixing only sulfur and a resin. Thus, the rubber composition provides an improved balance of tensile properties, fuel economy and abrasion resistance. The invention also relates to a masterbatch of this type, which contains sulphur and a resin having an acid number of 5 or more. Further, as described above, the above-described master batch may be incorporated into a rubber composition. The invention also relates to a method for using such a masterbatch as an additive in rubber, which masterbatch contains sulphur and a resin having an acid number of 5 or more.

Resin refers to a hydrocarbon oligomer containing carboxyl groups.

The master batch may contain compounding agents generally used in the tire industry to such an extent that the effects of the present invention are not impaired, as long as the master batch contains sulfur and a resin having an acid value of 5 or more. However, the master batch preferably does not contain any diene rubber. If the master batch contains a diene rubber, since the diene rubber and sulfur are not ionically bonded to each other, it physically inhibits the formation of an ionic bond between the resin having an acid value of 5 or more and sulfur. Further, when the master batch is introduced during the final kneading step of preparing the rubber composition, the diene-based rubber in which silica or carbon black hardly permeates can easily initiate fracture. Thus, in another suitable embodiment of the invention, the masterbatch does not contain any diene rubber.

The acid value (mg KOH/g) of the resin is 5 or more. The use of a resin having such an acid value promotes ionic bonding and adsorption of sulfur to the resin, so that the sulfur surface may become hydrophobic, which promotes dispersion of sulfur in the resin. Therefore, it is possible to prepare a master batch in which sulfur is finely dispersed in a resin and is easily mixed into a rubber composition, so that the effects of the present invention can be achieved. The acid value is preferably 10 or more, more preferably 15 or more, still more preferably 20 or more, and particularly preferably 25 or more. From the viewpoint of dispersibility of the resin, the upper limit of the acid value is preferably 500 or less, more preferably 250 or less, further preferably 200 or less, and further preferably 180 or less.

The acid value of the resin herein means the amount (in mg) of potassium hydroxide required to neutralize the acid present in 1g of the resin, which is measured by potentiometric titration (JIS K0070: 1992).

The softening point of the resin is preferably 50 ℃ or higher, more preferably 60 ℃ or higher, and still more preferably 70 ℃ or higher. The softening point is preferably 140 ℃ or lower, more preferably 120 ℃ or lower. The resin having a softening point within the above range can be highly dispersed in the rubber composition.

The softening point herein was determined using a flow tester (CFT-500D from Shimadzu corporation) as follows: heating was carried out at a temperature rise rate of 6 ℃/min while a 1g resin sample was extruded through a nozzle having a diameter of 1mm and a length of 1mm by applying a load of 1.96MPa with a plunger, and the amount of downward movement of the plunger of the flow tester was plotted against the temperature. The temperature at which half of the sample flowed out was defined as the softening point.

The SP value of the resin is preferably 9.2 or more, more preferably 10 or more. The SP value is preferably 13 or less, more preferably 12 or less. The resin having an SP value within the above range can be highly dispersed in the rubber composition (rubber masterbatch).

Herein, the SP value refers to a solubility parameter calculated according to Hansen (Hansen) equation.

The resin may be any one commonly used in the tire industry, examples including: aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenol resins, rosin-based resins, petroleum resins, terpene-based resins, p-tert-butylphenol acetylene resins, and acrylic (ester) -based resins. Commercial products of such resins include products of bovingian petrochemicals, sumitomo bakelite co, anyuan chemical, tokyo co, Rutgers Chemicals, BASF, arizona chemical, japanese chemical, japan catalyst co, JX Energy, kawa chemical co, takanga chemical co, east asia synechiae, and Harima Chemicals Group, inc. These may be used alone, or two or more of these may be used in combination. Among them, rosin-based resins, acrylic (ester) -based resins, aromatic vinyl polymers, coumarone-indene resins and terpene-based resins are preferable, and rosin-based resins and acrylic (ester) -based resins are more preferable. Particularly, rosin-based resins are particularly preferable because they have an acid value of 5 or more and can be well dispersed in rubber, so that the effects of the present invention can be suitably achieved. When the resin is a rosin-based resin, the carboxyl group of the rosin-based resin promotes adsorption and dispersion of sulfur in the resin. In addition, the polycyclic structure and the branches of the rosin-based resin absorb radicals generated during the dispersion of sulfur in the resin, thereby reducing the cracking of the polymer. This allows a suitable shear torque to be applied to the sulfur, thereby promoting dispersion of the sulfur. Therefore, it is considered that the use of a master batch in which the rosin-based resin and the sulfur ion are bonded together improves the dispersibility of sulfur.

The aromatic vinyl polymer refers to a resin produced by polymerizing alpha-methylstyrene and/or styrene. Examples include styrene homopolymers (styrene resins), alpha-methylstyrene homopolymers (alpha-methylstyrene resins), copolymers of alpha-methylstyrene and styrene and copolymers of styrene with other monomers.

The coumarone-indene resin refers to a resin containing coumarone and indene as main monomer components constituting the skeleton (main chain) of the resin. Examples of monomer components that may be contained in the backbone in addition to coumarone and indene include styrene, alpha-methylstyrene, methylindene, and vinyltoluene.

The indene resin refers to a resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

Examples of the phenol resin include those produced by reacting a phenol with an aldehyde (e.g., formaldehyde, acetaldehyde or furfural) in the presence of an acid catalyst or a base catalyst. Among them, a phenol resin produced by a reaction in the presence of an acid catalyst (e.g., a novolak-type phenol resin) is preferable.

The rosin-based resin is obtained, for example, as a solid hydrocarbon secreted from a tree (e.g., coniferous tree, such as pine) and contains a resin acid having a reactive double bond. Resin acids refer to compounds containing carboxyl groups derived from trees. Specific examples of the resin acid having a reactive double bond include: abietic acid, palustric acid, neoabietic acid, levopimaric acid, pimaric acid, isopimaric acid, dehydroabietic acid, and dihydroabietic acid.

Such rosin-based resins are classified according to whether or not they are modified. Specifically, they may be unmodified rosins (non-modified rosins) or modified rosins (rosin derivatives).

Examples of unmodified rosins: including tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. These unmodified rosins may be used alone, or two or more of these may be used in combination. Preferred unmodified rosins are tall rosin and gum rosin.

Modified rosin means a modified product of any of the above-mentioned unmodified rosins, and examples include rosin esters, unsaturated carboxylic acid-modified rosins, unsaturated carboxylic acid-modified rosin esters, amide compounds of rosins, rosin amine salts, rosin-modified petroleum resins, and rosin-modified phenol resins.

The rosin ester can be prepared, for example, by reacting the above-mentioned unmodified rosin with a polyol by a known esterification method.

Examples of the polyhydric alcohol include: glycols such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylene glycol, tetramethylene glycol, 1, 3-butanediol, and 1, 6-hexanediol; trihydric alcohols such as glycerol, trimethylolpropane, trimethylolethane and triethylolethane; tetrahydric alcohols such as pentaerythritol and dipentaerythritol; aminoalcohols, for example triethanolamine, tripropanolamine, triisopropanolamine, N-isobutyldiethanolamine and N-N-butyldiethanolamine. These polyols may be used alone, or two or more of these may be used in combination.

The unmodified rosin and the polyol may be incorporated in such a manner that the molar ratio (OH/COOH) of the hydroxyl group of the polyol to the carboxyl group of the unmodified rosin is, for example, 0.2 to 1.2. The unmodified rosin and polyol can be reacted at a temperature of, for example, 150 to 300 ℃ for a duration of, for example, 2 to 30 hours. In such a reaction, a known catalyst may be added in an appropriate amount as necessary.

The unsaturated carboxylic acid-modified rosin can be produced, for example, by reacting the above-mentioned unmodified rosin with an α, β -unsaturated carboxylic acid by a known method.

Examples of the α, β -unsaturated carboxylic acids include the α, β -unsaturated carboxylic acids themselves and anhydrides thereof. Specific examples include fumaric acid, maleic anhydride, itaconic acid, citraconic anhydride, acrylic acid, and methacrylic acid. These α, β -unsaturated carboxylic acids may be used singly or two or more of these may be used in combination.

The unmodified rosin and the α, β -unsaturated carboxylic acid may be incorporated in a ratio of the amount of the α, β -unsaturated carboxylic acid to 1mol of the unmodified rosin, for example, 1mol or less. The unmodified rosin and the α, β -unsaturated carboxylic acids can be reacted at a temperature of, for example, 150 ℃ to 300 ℃ for a duration of, for example, 1 to 24 hours. In such a reaction, a known catalyst may be added in an appropriate amount, if necessary.

The unsaturated carboxylic acid-modified rosin ester can be produced, for example, by reacting the unmodified rosin with the polyhydric alcohol and the α, β -unsaturated carboxylic acid, either sequentially or simultaneously.

When the above components are reacted sequentially, the unmodified rosin may be reacted first with the polyol and then with the α, β -unsaturated carboxylic acid; alternatively, the unmodified rosin may be reacted first with the α, β -unsaturated carboxylic acid and then with the polyol. The esterification reaction between the unmodified rosin and the polyol and the modification reaction between the unmodified rosin and the α, β -unsaturated carboxylic acid can be carried out under the above-mentioned conditions.

The amide compound of rosin can be produced, for example, by reacting the above-mentioned unmodified rosin with an amidating agent.

Examples of the amidating agent include primary polyamine compounds and/or secondary polyamine compounds, polyoxazoline compounds, and polyisocyanate compounds.

The primary polyamine compound and/or the secondary polyamine compound means a compound containing two or more primary amino groups and/or secondary amino groups per molecule, which can undergo a condensation reaction with a carboxyl group present in an unmodified rosin to amidate the rosin. Specific examples of such polyamine compounds include: acyclic diamines such as ethylenediamine, N-ethylaminoethylamine, 1, 2-propylenediamine, 1, 3-propylenediamine, N-methyl-1, 3-propylenediamine, bis (3-aminopropyl) ether, 1, 2-bis (3-aminopropoxy) ethane, 1, 3-bis (3-aminopropoxy) -2, 2-dimethylpropane, 1, 4-diaminobutane and laurylaminopropylamine; cyclic diamines such as 2-aminomethylpiperidine, 4-aminomethylpiperidine, 1, 3-bis (4-piperidyl) propane and homopiperazine; polyamines such as diethylenetriamine, triethylenetetramine, iminodipropylamine and methyliminodipropylamine; and a hydrohalide salt of the above polyamine compound. These primary polyamine compounds and/or secondary polyamine compounds may be used alone, or two or more of these may be used in combination.

The polyoxazoline compound refers to a compound containing two or more polyoxazoline rings per molecule, which can undergo an addition reaction with a carboxyl group present in an unmodified rosin to amidate the rosin. Examples of such polyoxazoline compounds include 2, 2' - (1, 3-phenylene) -bis (2-oxazoline). These polyoxazoline compounds may be used alone, or two or more of these may be used in combination.

The polyisocyanate compound means a compound containing two or more isocyanate groups per molecule, which can undergo addition condensation decarboxylation reaction with a carboxyl group present in an unmodified rosin to amidate the rosin. Examples of such polyisocyanate compounds include: aromatic diisocyanates such as tolylene diisocyanate (2, 4-tolylene diisocyanate or 2, 6-tolylene diisocyanate or a mixture thereof), phenylene diisocyanate (m-phenylene diisocyanate or p-phenylene diisocyanate or a mixture thereof), 1, 5-naphthalene diisocyanate, diphenylmethane diisocyanate (4, 4 '-diphenylmethane diisocyanate, 2, 4' -diphenylmethane diisocyanate or 2, 2 '-diphenylmethane diisocyanate or a mixture thereof) and 4, 4' -toluidine diisocyanate; araliphatic diisocyanates, such as xylylene diisocyanate (1, 3-xylylene diisocyanate or 1, 4-xylylene diisocyanate or mixtures thereof) and tetramethylxylylene diisocyanate (1, 3-tetramethylxylylene diisocyanate or 1, 4-tetramethylxylylene diisocyanate or mixtures thereof); aliphatic diisocyanates such as 1, 3-trimethylene diisocyanate, 1, 4-tetramethylene diisocyanate, 1, 5-pentamethylene diisocyanate and 1, 6-hexamethylene diisocyanate; alicyclic diisocyanates such as cyclohexane diisocyanate, 3-isocyanatomethyl-3, 5, 5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), methylene-bis (cyclohexyl isocyanate), norbornane diisocyanate and bis (isocyanatomethyl) cyclohexane; and other diisocyanates; and their derivatives (e.g., multimers, polyol adducts). These polyisocyanate compounds may be used alone, or two or more of these may be used in combination.

The above-mentioned amidating agents may be used alone, or two or more of them may be used in combination.

The unmodified rosin and the amidating agent may be incorporated in such a manner that the molar ratio of the active groups of the amidating agent (primary and/or secondary amino groups, polyoxazoline rings or isocyanate groups) to the carboxyl groups of the unmodified rosin (OH/active groups) is, for example, from 0.2 to 1.2. The unmodified rosin and polyol can be reacted at a temperature of, for example, 120 ℃ to 300 ℃ for a duration of, for example, 2 hours to 30 hours. In such a reaction, a known catalyst may be added in an appropriate amount, if necessary.

The rosin amine salt can be prepared by neutralizing the carboxyl group present in an unmodified rosin with a tertiary amine compound.

Examples of the tertiary amine compound include: tri (C1-C4 alkyl) amines such as trimethylamine and triethylamine; and heterocyclic amines such as morpholine. These tertiary amine compounds may be used alone, or two or more of these may be used in combination.

Further, other examples of the modified rosin include rosin-modified petroleum resins, rosin-modified phenols (rosin-modified phenol resins), and rosin alcohols prepared by reducing carboxyl groups of rosin-based resins (e.g., unmodified rosins, unsaturated carboxylic acid-modified rosins). These modified rosins may be used alone, or two or more of these may be used in combination. Preferred modified rosins are rosin esters and unsaturated carboxylic acid modified rosins.

As for the rosin-modified phenol resin, examples of the rosin used for modification include gum rosin, wood rosin, and tall rosin, and examples of the phenol resin to be modified include novolak (novolac) type phenol resin, resol (resol) type phenol resin, and novolak-resol complex type phenol resin.

The rosin-based resin may be used alone, or two or more of these may be used in combination.

Among rosin-based resins, gum rosin, tall rosin, and modified gum rosin are preferable in order to more suitably obtain the effects of the present invention. More preferred are gum rosin, tall rosin, and rosin esters of gum rosin, unsaturated carboxylic acid-modified rosins, or unsaturated carboxylic acid-modified rosin esters. Suitable examples of these include maleic acid modified rosins and maleic anhydride modified rosins.

Examples of petroleum resins include C5 resins, C9 resins, C5/C9 resins, and dicyclopentadiene (DCPD) resins.

Examples of the terpene-based resin include polyterpene resins produced by polymerization of terpene compounds; an aromatic modified terpene resin prepared by polymerization of a terpene compound and an aromatic compound; and hydrides of the above resins.

Polyterpene resin refers to a resin produced by polymerization of terpene compounds. The terpene compound is a compound having the formula (C)₅H₈) And n or an oxygen-containing derivative thereof, each having a terpene main chain and being classified, for example, as a monoterpene (C)₁₀H₁₆) Sesquiterpenes (C)₁₅H₂₄) Or diterpenes (C)₂₀H₃₂) Examples of such terpene compounds include α -Pinene, β -pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α -phellandrene, α -terpinene, gamma-terpinene, terpinolene, 1, 8-cineole, 1, 4-cineole, α -terpineol, β -terpineol and gamma-terpineol.

Examples of the polyterpene resin include resins made of the above-mentioned terpene compounds, such as pinene resin, limonene resin, dipentene resin, and pinene-limonene resin. Among them, pinene resins are preferable because they are simple in polymerization reaction and also because they are made of natural rosin and thus can be obtained at low cost. Pinene resins generally contain two isomers (i.e., α -pinene and β -pinene), and are classified into β -pinene resins mainly containing β -pinene and α -pinene resins mainly containing α -pinene, depending on the ratio of components in the resins.

Examples of the aromatic modified terpene resin include terpene phenolic resins made of the above terpene compounds and phenolic compounds; and terpene styrenic resins prepared from the above terpene compounds and styrenic compounds. Terpene phenolic styrenic resins made from the above terpene compounds, phenolic compounds and styrenic compounds may also be used. Examples of the phenolic compounds include phenol, bisphenol a, cresol and xylenol. Examples of the styrenic compound include styrene and α -methylstyrene.

Examples of the p-tert-butylphenol acetylene resin include resins produced by condensation of p-tert-butylphenol and acetylene.

Examples of the acrylic acid (ester) -based monomer component of the acrylic acid (ester) -based resin include (meth) acrylic acid and (meth) acrylic acid derivatives such as (meth) acrylic acid esters (e.g., alkyl esters such as 2-ethylhexyl acrylate; aryl esters; aralkyl esters), (meth) acrylamide and (meth) acrylamide derivatives. The term "(meth) acrylic acid" is a generic term for acrylic acid and methacrylic acid.

The monomer component of the acrylic resin may include, in addition to (meth) acrylic acid or (meth) acrylic acid derivatives, aromatic vinyl monomers such as styrene, α -methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene.

The acrylic resin may be formed of only the (meth) acrylic component, or may further contain components other than the (meth) acrylic component. Further, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or other groups.

Examples of sulfur include those commonly used in the rubber industry, such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. Commercial products of Sulfur include products of oil & oil chemical industries, light well swamp Sulfur (Karuizawa Sulfur co., Ltd.), four nationwide chemical industries, Flexsys, japan seiko industries, and fine well chemical industries. These may be used alone, or two or more of these may be used in combination.

The master batch can be prepared by melt-mixing sulfur and a resin having an acid value of 5 or more.

The mixing is preferably carried out as follows: a resin having an acid value of 5 or more is melted at a high temperature, a small portion of sulfur is introduced into the molten resin, and they are mixed while checking whether or not they are dissolved.

In the master batch, sulfur and the resin having an acid value of 5 or more are preferably present in a ratio (mass ratio) of sulfur (solid component) to the resin having an acid value of 5 or more of 1: 0.05 to 10 (more preferably 1: 0.1 to 7, further more preferably 1: 0.5 to 5). By setting the ratio within the above range, the effects of the present invention can be more appropriately achieved.

The amount of sulfur (solid content) in the master batch is preferably 10% by mass or more, more preferably 12% by mass or more, further preferably 15% by mass or more, and particularly preferably 20% by mass or more, based on 100% by mass of the master batch. The amount of sulfur (solid content) in the masterbatch is also preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. The amount of sulfur (solid content) in the masterbatch is particularly preferably about 30 to 60 mass%. If the amount is within the above range, the effects of the present invention can be more suitably obtained.

The amount of the resin having an acid value of 5 or more in the masterbatch is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more, based on 100% by mass of the masterbatch. The amount of the resin having an acid value of 5 or more in the master batch is preferably 90% by mass or less, more preferably 85% by mass or less, and still more preferably 80% by mass or less. The amount of the resin having an acid value of 5 or more in the master batch is particularly preferably about 40 to 70 mass%. If the amount is within the above range, the effects of the present invention can be more suitably obtained.

The amount of the master batch is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, further more preferably 2.5 parts by mass or more, and particularly preferably 3.0 parts by mass or more, relative to 100 parts by mass of the rubber component. The amount of the master batch is also preferably 20 parts by mass or less, more preferably 15 parts by mass or less, further more preferably 12 parts by mass or less, and particularly preferably 10 parts by mass or less. If the amount is within the above range, the effects of the present invention can be more suitably obtained.

Examples of the silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Among them, wet-process silica is preferable because it contains a large amount of silanol groups. Commercial products of Silica include products of Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan, and Tokuyama Corporation. These may be used alone, or two or more of these may be used in combination.

The content of silica is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, further more preferably 55 parts by mass or more, and further more preferably 60 parts by mass or more, relative to 100 parts by mass of the rubber component. The use of a suitable amount of silica tends to provide good wet grip performance and handling stability for passenger vehicle tires. The upper limit of the content of silica is not particularly limited, but is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, further preferably 170 parts by mass or less, and particularly preferably 150 parts by mass or less. When the upper limit is set on the amount of silica, good abrasion resistance and fuel economy tend to be achieved.

Nitrogen adsorption specific surface area (N) of silica₂SA) is preferably 70m²More preferably,/g or more, and140m²a total of 160m or more, preferably 160m²More than g. When nitrogen adsorption specific surface area (N) of silica₂SA) is not less than the lower limit, good wet grip performance and tensile strength at break tend to be obtained. Further, N to silica₂The upper limit of SA is not particularly limited, but is preferably 500m²A ratio of the total amount of the components to the total amount of the components is 300m or less²(ii) less than g, more preferably 280m²The ratio of the carbon atoms to the carbon atoms is less than g. When nitrogen adsorption specific surface area (N) of silica₂SA) is not more than the upper limit, good silica dispersibility tends to be obtained.

N of silicon dioxide₂SA is measured by the BET method according to ASTM D3037-93.

When the rubber composition contains silica, it preferably further contains a silane coupling agent.

Non-limiting examples of silane coupling agents include: sulfide-based silane coupling agents, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (, Bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silane coupling agents, such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT-Z (both available from Momentive corporation); vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silane coupling agents such as gamma-glycidoxypropyltriethoxysilane and gamma-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; chlorine-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercial products of silane coupling agents include Degussa, Momentive, Shin-Etsu Silicones, Tokyo chemical industries, Azmax, Dow Corning Tokyo. These may be used alone, or two or more of these may be used in combination.

The amount of the silane coupling agent is preferably 3 parts by mass or more, and more preferably 6 parts by mass or more, relative to 100 parts by mass of silica. When the amount of the silane coupling agent is 3 parts by mass or more, good properties (e.g., tensile strength at break) tend to be obtained. The amount of the silane coupling agent is also preferably 12 parts by mass or less, and more preferably 10 parts by mass or less. When the amount of the silane coupling agent is 12 parts by mass or less, an effect corresponding to the amount tends to be obtained.

Non-limiting examples of carbon blacks include: n134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercial products of Carbon black include Asahi Carbon co., ltd., Cabot Japan k.k., TokaiCarbon co., ltd., mitsubishi chemical co., lion king co., NSCC Carbon co., ltd., and columbia Carbon. These may be used alone, or two or more of these may be used in combination.

The amount of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the rubber component. When the amount of carbon black is not less than the lower limit, good UV cracking resistance and good abrasion resistance tend to be obtained. For use in passenger cars where wet grip performance is important, the amount of carbon black is also preferably 10 parts by mass or less, and more preferably 7 parts by mass or less. When the amount of carbon black is not more than the upper limit, the rubber composition tends to provide good wet grip performance and fuel economy.

Of carbon blackNitrogen adsorption specific surface area (N)₂SA) is preferably 50m²A value of 80m or more, more preferably 80m²A total of 100m or more, preferably²More than g. When nitrogen adsorption specific surface area (N) of carbon black₂SA) is not less than the lower limit, good wear resistance and grip performance tend to be obtained. N is a radical of₂SA is preferably 200m²A ratio of not more than 150 m/g, more preferably²A value of 130m or less, more preferably 130m or less²The ratio of the carbon atoms to the carbon atoms is less than g. When N is present₂When the SA does not exceed the upper limit, the carbon black tends to be well dispersed.

Nitrogen adsorption specific surface area of carbon black according to JIS K6217-2: 2001.

In the rubber composition, the total amount of silica and carbon black is preferably 30 parts by mass or more, and more preferably 40 parts by mass or more, relative to 100 parts by mass of the rubber component. For use in passenger cars, the total amount of silica and carbon black is more preferably 80 parts by mass or more. The total amount of silica and carbon black is also preferably 300 parts by mass or less, more preferably 200 parts by mass or less, and still more preferably 160 parts by mass or less. When the total amount of silica and carbon black is within the above range, the reinforcing effect of these fillers can be sufficiently achieved as well as abrasion resistance, fuel economy and tensile properties.

The rubber composition may contain other fillers in addition to silica and carbon black. Non-limiting examples of other fillers include calcium carbonate, talc, alumina, clay, aluminum hydroxide, alumina, magnesium sulfate, and graphite.

The rubber composition may comprise a plasticizer. Non-limiting examples of plasticizers include oils, liquid polymers (liquid diene polymers), and liquid resins. These plasticizers may be used alone, or two or more of these may be used in combination.

The oil can be any conventional oil including, for example: processing oils such as paraffinic processing oils, aromatic processing oils, and naphthenic processing oils; low polycyclic aromatic (PCA) process oils such as TDAE and MES; a vegetable oil; and mixtures thereof. Aromatic processing oils are preferred from the viewpoint of abrasion resistance and fracture properties. Specific examples of aromatic Process oils include the Diana Process Oil AH series available from shinning corporation.

The liquid polymer (liquid diene polymer) means a diene polymer which is liquid at room temperature (25 ℃).

The weight average molecular weight (Mw) of the liquid diene polymer in terms of polystyrene measured by Gel Permeation Chromatography (GPC) is preferably 1.0 × 10³To 2.0 × 10⁵More preferably 3.0 × 10³To 1.5 × 10⁴。

The Mw of the liquid diene polymers herein is determined by Gel Permeation Chromatography (GPC) calibrated with polystyrene standards.

Examples of the liquid diene-based polymer include a liquid styrene-butadiene copolymer (liquid SBR), a liquid polybutadiene polymer (liquid BR), a liquid polyisoprene polymer (liquid IR), and a liquid styrene-isoprene copolymer (liquid SIR).

Non-limiting examples of liquid resins include liquid aromatic vinyl polymers, coumarone-indene resins, terpene resins and rosin resins and their hydrides.

The liquid aromatic vinyl polymer refers to a resin prepared by polymerizing alpha-methylstyrene and/or styrene. Examples include liquid resins such as styrene homopolymers, alpha-methylstyrene homopolymers, and copolymers of alpha-methylstyrene and styrene.

The liquid coumarone-indene resin refers to a resin containing coumarone and indene as main monomer components constituting the skeleton (main chain) of the resin. Examples include: liquid resins containing styrene, alpha-methylstyrene, methylindene, vinyltoluene or other monomer components in the backbone can be included in addition to coumarone and indene.

The liquid terpene resin refers to a liquid terpene-based resin represented by a resin produced by polymerization of terpene compounds (e.g., α -pinene, β -pinene, camphene, dipentene) and a terpene phenolic resin (made of a terpene compound and a phenolic compound).

The liquid rosin resin refers to a liquid rosin resin represented by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrides thereof.

The rubber composition may contain a solid resin (oligomer which is solid at room temperature (25 ℃) in addition to the resin having an acid value of 5 or more present in the master batch.

The amount of the solid resin (if present) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further more preferably 5 parts by mass or more, relative to 100 parts by mass of the rubber component. The amount of the solid resin is also preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and further more preferably 30 parts by mass or less. By making the amount of the solid resin within the above range, good wet grip performance tends to be obtained.

Non-limiting examples of solid resins include those as described with respect to resins having an acid number of 5 or more used in the masterbatch. Preferred examples include: rosin-based resins, polyterpene resins, aromatic modified terpene resins (e.g., terpene phenolic resins), coumarone-indene resins, aromatic vinyl polymers, and petroleum resins (e.g., dicyclopentadiene-based resins (DCPD-based resins), C5 petroleum resins, C9 petroleum resins, and C5/C9 petroleum resins).

The rubber composition preferably contains an antioxidant from the viewpoint of properties such as crack resistance and ozone resistance.

Non-limiting examples of antioxidants include: naphthylamine-based antioxidants, such as phenyl- α -naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4, 4 '-bis (α, α' -dimethylbenzyl) diphenylamine; p-phenylenediamine antioxidants, such as N-isopropyl-N ' -phenyl-p-phenylenediamine, N- (1, 3-dimethylbutyl) -N ' -phenyl-p-phenylenediamine, and N, N ' -di-2-naphthyl-p-phenylenediamine; quinoline-based antioxidants, such as 2, 2, 4-trimethyl-1, 2-dihydroquinoline polymers; monophenol-based antioxidants such as 2, 6-di-t-butyl-4-methylphenol and styrenated phenol; and bisphenol, triphenol, or polyphenol antioxidants such as tetrakis [ methylene-3- (3 ', 5 ' -di-tert-butyl-4 ' -hydroxyphenyl) propionate ] methane. Among them, p-phenylenediamine antioxidants and quinoline antioxidants are preferable, and N- (1, 3-dimethylbutyl) -N' -phenyl-p-phenylenediamine or a 2, 2, 4-trimethyl-1, 2-dihydroquinoline polymer is more preferable. Commercial products of antioxidants include products of Seiko chemical, Sumitomo chemical, New Engineer chemical industries, and Flexsys.

The amount of the antioxidant is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the rubber component. When the amount of the antioxidant is not less than the lower limit, sufficient ozone resistance tends to be obtained. The amount of the antioxidant is preferably 7.0 parts by mass or less, and more preferably 6.0 parts by mass or less. When the amount of the antioxidant is not more than the upper limit, good tire appearance and fuel economy tend to be obtained.

The rubber composition preferably comprises a fatty acid, such as stearic acid or oleic acid. The amount of the fatty acid is preferably 0.5 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, relative to 100 parts by mass of the rubber component, from the viewpoint of property balance.

The stearic acid may be conventional stearic acid, and examples include products from NOF Corporation, kao Corporation, fuji film and mitsukoku Corporation, and kokura fatty acid co.

The rubber composition preferably comprises zinc oxide. The amount of zinc oxide is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the rubber component, from the viewpoint of balance of properties.

The zinc oxide may be a conventional zinc oxide, and examples include those of mitsui metal mining co, tokyo lead-free co, Hakusui Tech co, ltd, n.

The rubber composition may comprise a wax. Non-limiting examples of waxes include: petroleum waxes and natural waxes, as well as synthetic waxes made by purifying or chemically treating a variety of waxes. These waxes may be used alone, or two or more kinds may be used in combination.

Examples of petroleum waxes include paraffin waxes and microcrystalline waxes. The natural wax may be any wax other than those derived from petroleum resources. Examples include: vegetable waxes such as candelilla wax, carnauba wax, japan wax, rice wax, and jojoba wax; animal waxes such as beeswax, lanolin and spermaceti; mineral waxes, such as ozokerite (ozokerite), ceresin (ceresin), and petrolatum (petroleum); and purified products of these waxes. Commercial products of waxes include products of the great interior new chemical industries, japan wax refiners and seiko chemical industries. The amount of the wax may be appropriately selected depending on the ozone resistance and cost.

The rubber composition may contain sulfur in addition to the sulfur present in the masterbatch.

When the rubber composition contains sulfur in addition to sulfur present in the master batch, the total amount of both (i.e., the total sulfur content of the rubber composition) is preferably 0.7 parts by mass or more, more preferably 1.0 parts by mass or more, and still more preferably 1.5 parts by mass or more, relative to 100 parts by mass of the rubber component. For use in a topping rubber (rubber) having a high sulfur content, the total sulfur content is preferably 7 parts by mass or less, more preferably 6 parts by mass or less, and still more preferably 5.6 parts by mass or less; for application to tread formulations, the total sulfur content is preferably 3 parts by mass or less, more preferably 2.5 parts by mass or less, and even more preferably 2.2 parts by mass or less. When the total content of sulfur is within the above range, good properties (tensile properties, fuel economy and abrasion resistance) tend to be obtained.

When sulfur is added in addition to the sulfur present in the masterbatch, the sulfur added can be any sulfur, including those useful in masterbatches, such as powdered sulfur, insoluble sulfur, and powdered sulfur containing zinc oxide.

The rubber composition preferably contains a vulcanization accelerator.

The amount of the vulcanization accelerator is not particularly limited, and the amount thereof can be freely selected depending on the desired vulcanization speed or crosslinking density. The amount of the vulcanization accelerator is usually 0.3 to 10 parts by mass, preferably 0.5 to 7 parts by mass, relative to 100 parts by mass of the rubber component.

The vulcanization accelerator may be of any type, including those commonly used. Examples of the vulcanization accelerator include: thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazyl disulfide and N-cyclohexyl-2-benzothiazylsulfenamide; thiuram based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD) and tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N); sulfenamide vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, N-tert-butyl-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide and N, N' -diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-o-tolylguanidine and o-tolylbiguanide. These may be used alone, or two or more of these may be used in combination. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferable from the viewpoint of balance of properties.

From the viewpoint of tensile properties, the amount of the vulcanization accelerator (which is a thiazole-based vulcanization accelerator) is preferably 1.5 parts by mass or less with respect to 100 parts by mass of the rubber component. Therefore, in another suitable embodiment of the present invention, the rubber composition contains 1.5 parts by mass or less of the thiazole-based vulcanization accelerator with respect to 100 parts by mass of the rubber component.

In addition to the above components, the rubber composition may suitably contain other compounding agents commonly used in the tire industry, such as a mold release agent.

The rubber composition can be prepared by known methods. For example, it can be prepared by kneading the components using a rubber kneader (e.g., an open roll mill or a banbury mixer) and vulcanizing the kneaded mixture.

The rubber composition is generally prepared by a process comprising the steps of: a basic kneading step of kneading a rubber component (diene-based polymer) and additives (e.g., a filler such as carbon black) other than a crosslinking agent (vulcanizing agent) and a vulcanization accelerator; a final kneading step of kneading the kneaded mixture prepared in the basic kneading step and a crosslinking agent (and preferably a vulcanization accelerator). The master batch of the present invention is preferably introduced and kneaded in the final kneading step, starting from the increase in rubber viscosity and the stretching property.

The kneading conditions were as follows. In the basic kneading step, the kneading temperature is usually 130 ℃ to 200 ℃, preferably 140 ℃ to 190 ℃, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 20 minutes. In the final kneading step, the kneading temperature is usually 115 ℃ or less, and in the roll kneading, 60 ℃ to 95 ℃ is preferable.

The composition obtained after mixing the vulcanizing agent and the vulcanization accelerator is usually vulcanized by, for example, press vulcanization. The vulcanization temperature is usually 130 ℃ to 200 ℃, preferably 140 ℃ to 190 ℃.

The rubber composition is suitable for a tread (cap tread, base tread), and can be used for tire components other than a tread, such as a sidewall, a base tread, a clinch apex (closure apex), a bead apex (bead apex), a cushion rubber, a rubber of carcass cord topping, a spacer (insulation), a chafer and an inner liner, and a side reinforcing layer of a run-flat tire.

The rubber composition is suitable for pneumatic tires. Such a pneumatic tire can be produced from the above rubber composition by a conventional method. Specifically, an unvulcanized rubber composition containing each component may be extruded into the shape of a tire member (e.g., tread), assembled with other tire members on a tire building machine in a conventional manner to prepare an unvulcanized tire, and then the unvulcanized tire may be heated and pressurized in a vulcanizing machine to prepare a tire.

The pneumatic tire can be used, for example, as a tire for passenger cars, a tire for large SUV, a tire for heavy load vehicles (such as trucks and buses), a tire for light trucks, or a tire for two-wheeled motor vehicles, or a tire for racing cars (high performance tire), a winter tire, or a run flat tire.