JP2016089015A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having a tread rubber composition capable of enhancing initial grip performance and stable grip performance in intermediate and later stages at the same time at high dimension while maintaining good abrasion resistance.SOLUTION: The invention relates to a pneumatic tire having a tread manufactured by using a tread rubber composition containing a rubber component, carbon black having nitrogen adsorption specific surface area of 151 m/g or more, a condensed resin obtained from a compound of which at least one hydrogen of a benzene ring is substituted by a hydroxyl group and/or an alkyl group and formaldehyde and a methylene donor with the carbon black of 5 to 170 pts.mass, the condensed resin of 0.5 to 20 pts.mass and the methylene donor of 0.04 to 10 pts.mass based on 100 pts.mass of the rubber composition and the content of a free monomer component contained in the condensed resin of 7 mass% or less.SELECTED DRAWING: None

Description

The present invention relates to a pneumatic tire having a tread produced using a tread rubber composition.

A tire tread is desired to maintain excellent grip performance from the initial driving to the end of driving. In other words, it is desired to maintain good grip performance during running and late stage as well as excellent initial grip performance, and it is also required to ensure wear resistance that generally tends to contradict grip performance.

Conventionally, for the purpose of improving the initial grip performance, a method of increasing the blending amount of a low softening point resin or a liquid polymer or a method of blending a low-temperature softening agent has been studied, and the tire temperature becomes 60 ° C. or higher. In order to obtain a stable grip performance during traveling, a method of blending a high softening point resin has been studied.

However, when a low softening point resin is blended, although the initial grip performance is improved, there is a problem that the grip performance during running and in the latter stage decreases as the temperature of the tread increases. On the other hand, when a high softening point resin such as coumarone indene resin is blended, there is a problem that the initial grip performance is greatly inferior although the stable grip performance during running and the latter period can be obtained.

Patent Document 1 discloses a method of combining a low softening point resin and a high softening point resin, which can be considered as a technique for solving these problems, into a rubber composition. However, since the compounding amount of the resin greatly affects the temperature characteristics of the entire rubber, the amount of resin that can be compounded is limited. As a result, even when the low softening point resin and the high softening point resin are used in combination, the initial grip performance and the stable grip performance during running cannot be obtained as much as when each resin is blended alone.

While the phenolic group hardens the structure as the chemical structure of the resin, it is difficult to disperse in nonpolar rubbers frequently used in tire rubber compositions, so terpene phenol, terpene aromatic, terpene aromatic A technology using a resin composed of two or more different types of monomers such as vinyl has also been proposed, but the initial grip performance and stable grip performance during and late driving while ensuring good wear resistance. Further improvement is required for the point of simultaneously improving the level of

Patent Document 2 discloses a rubber composition for a tire that uses a specific amount of a specific alkylphenol resin and a methylene donor to improve the extrusion processability, handling stability, fuel efficiency, elongation at break, and handling response in a well-balanced manner. Although the article has been disclosed, this document also does not discuss the point of improving the initial grip performance and the stable grip performance in the running / late period at the same time while ensuring good wear resistance. .

JP 2004-137463 A JP 2012-241065 A

The present invention solves the above-mentioned problems, and uses a tread produced using a tread rubber composition that can improve the initial grip performance and the stable grip performance during running / late stage at the same time in a high dimension while ensuring good wear resistance. It aims at providing the pneumatic tire which has.

The present invention relates to a rubber component, a carbon black having a nitrogen adsorption specific surface area of 151 m ² / g or more, a compound obtained by substituting at least one hydrogen of a benzene ring with a hydroxyl group and / or an alkyl group, and a condensed resin obtained from formaldehyde A pneumatic tire having a tread produced using a tread rubber composition containing a methylene donor, wherein the carbon black is included in an amount of 5 to 170 parts by mass with respect to 100 parts by mass of the rubber component. The present invention relates to a pneumatic tire containing 0.5 to 20 parts by mass, 0.04 to 10 parts by mass of the methylene donor, and containing 7% by mass or less of a free monomer component contained in the condensed resin.

The condensation resin is preferably an alkylphenol resin obtained from formaldehyde and at least two compounds selected from the group consisting of 2-alkylphenol, 3-alkylphenol, and 4-alkylphenol.

The condensation resin is preferably a resin obtained from 2-alkylphenol, 3-alkylphenol, 4-alkylphenol, and formaldehyde.

It is preferable that the methylene donor is at least one compound selected from the group consisting of hexamethylenetetramine, hexamethoxymethylol melamine, and hexamethylol melamine pentamethyl ether.

The methylene donor is preferably hexamethylenetetramine.

The 2-alkylphenol, the 3-alkylphenol, and the 4-alkylphenol are preferably o-cresol, m-cresol, and p-cresol, respectively.

The content of the free monomer component contained in the condensation resin is preferably 1% by mass or less.

It is preferable that the softening point of the condensation resin is 98 to 140 ° C.

The condensation resin preferably has a novolac type condensation resin content of 93 to 100% by mass.

It is preferable that the tread rubber composition contains 0.2 to 15 parts by mass of zinc dithiophosphate with respect to 100 parts by mass of the rubber component.

According to the present invention, a specific amount of a condensation resin obtained from a rubber component, carbon black having a specific nitrogen adsorption specific surface area, a compound in which at least one hydrogen of a benzene ring is substituted with a hydroxyl group and / or an alkyl group, and formaldehyde And a specific amount of methylene donor, and a tread rubber composition in which the content of free monomer components (residual in the resin due to unreacted content) contained in the condensation resin is not more than a specific amount. Since it is a pneumatic tire with a tread made using it, it ensures good wear resistance while maintaining initial grip performance and stable grip performance during and late driving (especially initial grip performance on dry road surfaces and during and late driving) Stable grip performance) can be achieved at a high level.

The present invention relates to a rubber component, a carbon black having a nitrogen adsorption specific surface area of 151 m ² / g or more, and 0.5 to 20 parts by mass of a specific condensation resin and 0.04 to 10 parts per 100 parts by mass of the rubber component. And the condensation resin is a resin obtained from formaldehyde and a compound obtained by substituting at least one hydrogen of the benzene ring with a hydroxyl group and / or an alkyl group, and contained in the condensation resin. A pneumatic tire having a tread produced using a tread rubber composition in which the content of a free monomer component (remaining in the resin due to unreacted) is 7% by mass or less.

In the present invention, by using a predetermined amount of the specific condensation resin and methylene donor, and the specific carbon black, the initial grip performance and the stable grip performance during the running / late period are ensured while ensuring good wear resistance. The initial grip performance on the dry road surface and the stable grip performance during running / late stage) can be improved at a high level at the same time, and the above performance balance can be remarkably improved.

The tread rubber composition constituting the pneumatic tire of the present invention includes a rubber component, carbon black having a specific nitrogen adsorption specific surface area, a specific condensation resin, and a methylene donor.

Examples of rubber components that can be used in the present invention include isoprene-based rubbers such as natural rubber (NR) and isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), Examples include diene rubbers such as ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR). A rubber component may be used independently and may use 2 or more types together. Among these, isoprene-based rubber, BR, and SBR are preferable, SBR and BR are more preferable, and SBR is more preferable because grip performance and wear resistance can be obtained in a balanced manner.

SBR is not particularly limited, and emulsion polymerization SBR (E-SBR), solution polymerization SBR (S-SBR), high molecular weight SBR of process oil extension, and modification for silica modified with a compound having interaction with silica SBR etc. are mentioned. In terms of effectively exhibiting the effects of the present invention, modified SBR for silica and S-SBR are preferable, and S-SBR is particularly preferable.

（式中、ｎは１〜１０の整数を表し、Ｒは２価の炭化水素基を表し、例えば−ＣＨ_２−であり、Ｒ^１、Ｒ^２及びＲ^３は、それぞれ独立に、炭素原子数が１〜４のヒドロカルビル基又は炭素原子数が１〜４のヒドロカルビルオキシ基を表し、Ｒ^１、Ｒ^２及びＲ^３の少なくとも１つがヒドロカルビルオキシ基であり、Ａは窒素原子を有する官能基を表す。） As the modified SBR for silica, SBR in which the terminal or main chain of the polymer is modified with a modifier having an interaction with various types of silica can be used. Specific examples include JP 2010-077412 and JP 2006. Examples thereof include modified SBR described in JP-A No. 274010, JP-A 2009-227858, JP-A 2006-306962, JP-A 2009-275178, and the like. Among these, modified SBR obtained by reacting a modifying agent represented by the following general formula (I) can be preferably used.

(In the formula, n represents an integer of 1 to 10, R represents a divalent hydrocarbon group, for example, —CH ₂ —, and R ¹ , R ^2, and R ³ each independently represents the number of carbon atoms. Represents a hydrocarbyl group having 1 to 4 carbon atoms or a hydrocarbyloxy group having 1 to 4 carbon atoms, at least one of R ¹ , R ² and R ³ is a hydrocarbyloxy group, and A represents a functional group having a nitrogen atom .)

The amount of bound styrene in SBR is preferably 15% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and particularly in the case of gripping direction, still more preferably 35% by mass or more. The amount of bound styrene is preferably 60% by mass or less, more preferably 55% by mass or less, and still more preferably 50% by mass or less. If the amount of bound styrene is less than 15% by mass, the wet grip performance may be insufficient, and if it exceeds 60% by mass, it becomes difficult to disperse the polymer and cross-link between the polymers uniformly, or to reduce fuel consumption and breakage. Elongation and wear resistance may be deteriorated. In the present invention, the styrene content of SBR is calculated by H ¹ -NMR measurement.

The content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more, particularly preferably 70% by mass or more, particularly preferably 90% by mass when used as a high performance tire. % Or more, and may be 100% by mass. There exists a possibility that the effect of this invention may not fully be exhibited as it is less than 50 mass%.

The BR is not particularly limited. For example, BR having a high cis blending amount, BR containing 1,2-syndiotactic polybutadiene crystal (SPB), BR synthesized using a rare earth element-based catalyst (rare earth BR) A thing common in the tire industry can be used. Among these, rare earth BR is preferable because good wear resistance can be obtained.

As the rare earth BR, a conventionally known one can be used, for example, a rare earth element-based catalyst (a lanthanum series rare earth element compound, an organoaluminum compound, an aluminoxane, a halogen-containing compound, a catalyst containing a Lewis base if necessary), etc. And synthesized. Among these, Nd-based BR synthesized using a neodymium-based catalyst is preferable because good wear resistance can be obtained.

The cis content of BR is preferably 90% by mass or more, more preferably 95% by mass or more, and the vinyl content is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 1% by mass or less. The cis content of BR (cis-1,4-bonded butadiene unit amount) and vinyl content (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectrum analysis.

When blending BR, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 15% by mass or more. The content is preferably 50% by mass or less, more preferably 40% by mass or less. If it is less than 5% by mass, good wear resistance may not be obtained, and if it exceeds 50% by mass, grip performance may be deteriorated.

Examples of the isoprene-based rubber include synthetic isoprene rubber (IR), natural rubber (NR), and modified natural rubber. When isoprene-based rubber is blended, the content of isoprene-based rubber in 100% by mass of the rubber component Is preferably less than 80% by mass, more preferably less than 75% by mass, and particularly preferably less than 20% by mass in the case of passenger car tires. There exists a possibility that the effect of this invention may not fully be exhibited as it is 80 mass% or more.

In the present invention, a specific condensation resin is used. The condensation resin used in the present invention is a resin obtained from formaldehyde and a compound in which at least one hydrogen of a benzene ring is substituted with a hydroxyl group and / or an alkyl group (hereinafter also referred to as a monomer component). The content of free monomer components contained (that is, the total amount of free monomer components) is 7% by mass or less. Since the content of the free monomer component is small, the effects of the present invention are suitably obtained.

As the condensation resin, a crosslinking reactive condensation resin is preferable. The crosslinkable reactive condensation resin means a monomer component, which will be described later, constituting the condensation resin, having a monomer component in which a substituent coordinated to the benzene ring is coordinated in a position other than the para position. The condensation resin composed only of the monomer component is low in crosslinking reactivity with the methylene donor due to structural steric hindrance and corresponds to a non-crosslinking reactive condensation resin.

Specifically, the condensation resin is a condensation resin (novolak type) obtained by reacting formaldehyde with a compound in which at least one of the hydrogen atoms of the benzene ring is substituted with a hydroxyl group and / or an alkyl group using an acid catalyst. A novolak-type phenol resin obtained by reacting at least two compounds selected from the group consisting of 2-alkylphenol, 3-alkylphenol and 4-alkylphenol with formaldehyde. Examples of commercially available products include resins having a structure such as PR-X11061 manufactured by Sumitomo Bakelite Co., Ltd., and Sumikanol 610, 611, and 620 manufactured by Taoka Chemical Industry Co., Ltd.

The compound in which at least one hydrogen in the benzene ring is substituted with a hydroxyl group and / or an alkyl group is not particularly limited, but a compound in which two hydrogen atoms in the benzene ring are substituted with a hydroxyl group and / or an alkyl group is particularly preferable. As a compound in which two hydrogen atoms in the benzene ring are substituted with a hydroxyl group and / or an alkyl group, a compound in which two hydrogen atoms in the benzene ring are substituted with a hydroxyl group, and two hydrogen atoms in the benzene ring are substituted with a hydroxyl group and an alkyl group. A compound is preferable, and a compound in which two hydrogen atoms of a benzene ring are substituted with a hydroxyl group and an alkyl group is particularly preferable.

Examples of the compound in which two hydrogen atoms in the benzene ring are substituted with a hydroxyl group and an alkyl group include 2-alkylphenol, 3-alkylphenol, and 4-alkylphenol. Resorcinol, catechol, hydroquinone and the like can be mentioned. Although a condensation resin using one kind of these monomer components may be used, a condensation resin using a plurality of kinds is preferable. It is preferable to use at least two compounds selected from the group consisting of 2-alkylphenol, 3-alkylphenol and 4-alkylphenol because the effects of the present invention can be suitably obtained. It is particularly preferred to use three compounds of 4-alkylphenol.

When the compound in which at least one hydrogen of the benzene ring is substituted with a hydroxyl group and / or an alkyl group has an alkyl group, the number of carbon atoms of the alkyl group is not particularly limited, but the effects of the present invention are preferably obtained. For reasons, 1 to 10 are preferable, 1 to 8 are more preferable, and 1 is particularly preferable. As alkylphenol, you may use combining what the carbon number of an alkyl group differs.

As the compound in which at least one hydrogen of the benzene ring is substituted with a hydroxyl group and / or an alkyl group, the 2-alkylphenol, the 3-alkylphenol, and the 4-alkylphenol are o-cresol, m-cresol, p, respectively. -When it is cresol. That is, it is preferable that the condensation resin is a cresol resin.

The acid catalyst is not particularly limited, and examples thereof include boron trifluoride / ether complex, boron trifluoride / phenol complex, boron trifluoride / water complex, boron trifluoride / alcohol complex, boron trifluoride / amine. A complex or a mixture thereof is used. Of these, boron trifluoride, boron trifluoride / phenol complex, boron trifluoride / ether complex and the like can be used.

The method for reacting the monomer component with formaldehyde in the presence of the acid catalyst is not particularly limited, and can be performed by a known method. For example, an acid catalyst, a monomer component, and formaldehyde may be dissolved in a suitable solvent and reacted at 100 to 180 ° C. for 1 to 10 hours.

The method for purifying the condensation resin obtained by the above reaction is not particularly limited, but for example, after dissolving in a solvent, purification operations such as recrystallization, column chromatography, distillation, etc., free monomer components contained in the condensation resin By performing until the total amount becomes a specific amount or less, the condensation resin is obtained. In addition, as a distillation method, the method as described in Unexamined-Japanese-Patent No. 2011-74205 can be used suitably.

The content of free monomer components contained in the condensation resin (total amount of free monomer components) is 7% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less, more preferably 1% by mass. % Or less. If it exceeds 7% by mass, the effects of the present invention cannot be sufficiently obtained.
The total amount of free monomer components is a value measured by gel filtration chromatography (GPC).

The content of the novolak type condensation resin is preferably 93 to 100% by mass, more preferably 96 to 100% by mass, still more preferably 98 to 100% by mass, and particularly preferably 99 to 100% by mass. . There exists a possibility that the effect of this invention may not fully be acquired as content of novolak-type condensation resin is less than 93 mass%.
The content of the novolak type condensation resin is a value measured by gel filtration chromatography (GPC).

The softening point of the condensation resin is preferably 98 ° C or higher, more preferably 100 ° C or higher, still more preferably 105 ° C or higher, and particularly preferably 110 ° C or higher. The softening point is preferably 140 ° C. or lower, more preferably 135 ° C. or lower.
The softening point of the condensation resin is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring device.

The softening point of the condensation resin can be adjusted by adjusting the combination and ratio of the above-mentioned 2-alkylphenol, 3-alkylphenol, 4-alkylphenol and the like used as the monomer component, and imparting appropriate anisotropy and crystallinity. . For example, the melting points of o-cresol, m-cresol, and p-cresol are 30 ° C., 12 ° C., and 35.5 ° C., respectively. By adjusting the softening point, the softening point of the condensation resin can be adjusted to a desired temperature.
Further, since the total amount of free monomer components contained in the condensation resin also affects the softening point, the softening point of the condensation resin can also be adjusted by adjusting this amount.

The weight average molecular weight (Mw) of the condensation resin is preferably 1000 or more, more preferably 1500 or more. Mw is preferably 3000 or less, more preferably 2500 or less, and still more preferably 1900 or less. The effect of this invention is acquired more suitably as Mw is in the said range.
The weight average molecular weight (Mw) was converted from standard polystyrene using a gel permeation chromatograph (GPC).

In this specification, GPC was measured under the following conditions (1) to (8).
(1) Apparatus: HLC-8020 manufactured by Tosoh Corporation
(2) Separation column: Tosoh GMH-XL (two in series)
(3) Measurement temperature: 40 ° C
(4) Carrier: Tetrahydrofuran (5) Flow rate: 0.6 mL / min (6) Injection volume: 5 μL
(7) Detector: Differential refraction (8) Molecular weight standard: Standard polystyrene

Content of the said condensation resin is 0.5-20 mass parts with respect to 100 mass parts of rubber components, Preferably it is 1-15 mass parts. The effect of this invention can fully be exhibited as it exists in the said range.

In the present invention, in addition to the above condensation resin having crosslinking reactivity, it is preferable to blend an alkylphenol alkyne condensation resin obtained by reacting alkylphenol with an alkyne such as acetylene as an adhesive grip improver. By using the condensation resin and the alkylphenol alkyne condensation resin in combination, the effects of the present invention are more remarkably exhibited.

Examples of the alkylphenol constituting the alkylphenol alkyne condensation resin include cresol, xylenol, t-butylphenol, octylphenol, and nonylphenol. Of these, a phenol having a branched alkyl group such as t-butylphenol is preferable, and t-butylphenol is particularly preferable.

The alkyne constituting the alkylphenol alkyne condensation resin is preferably an alkyne having 2 to 10 carbon atoms, more preferably an alkyne having 2 to 5 carbon atoms, and particularly preferably acetylene.

The content of the alkylphenol alkyne condensation resin is preferably 5 parts by mass or more, more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. Moreover, this content becomes like this. Preferably it is 60 mass parts or less, More preferably, it is 50 mass parts or less. The effect of this invention can fully be exhibited as it exists in the said range.

In addition to the condensation resin and the alkylphenol alkyne condensation resin, other resins are preferably blended. Examples of other resins include acrylic resins and terpene resins. Examples of the acrylic resin include styrene acrylic resin having improved compatibility with rubber, and examples of the terpene resin include aromatic terpene resin, terpene phenol resin, and polyterpene resin.

The content of the other resin is preferably 1 to 15 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. The effect of this invention can be exhibited suitably as it is in the said range.

The total content of the condensation resin, the alkylphenol alkyne condensation resin, and the other resin is preferably 10 to 100 parts by mass, more preferably 20 to 70 parts by mass with respect to 100 parts by mass of the rubber component. The effect of this invention can fully be exhibited as it exists in the said range.

In the present invention, a methylene donor is used. By using a methylene donor together with the condensation resin, it is possible to obtain a good balance between initial grip performance and stable grip performance during running and at the later stage while ensuring good wear resistance.

Examples of the methylene donor include hexamethylenetetramine (HMT), hexamethoxymethylol melamine (HMMM), hexamethylol melamine pentamethyl ether (HMMPME), and Sumikanol 507A. Among these, HMT, HMMM, and HMMPME are preferable, and HMT is particularly preferable in that the effects of the present invention can be suitably obtained.

The content of the methylene donor is 0.04 to 10 parts by mass, preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. The effect of this invention can fully be exhibited as it exists in the said range. When HMT is used, even if it is a small amount (5 parts by mass or less, preferably 3 parts by mass or less, more preferably 2 parts by mass or less), the effects of the present invention can be sufficiently exerted.

In the present invention, carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 151 m ² / g or more is used. By using the carbon black together with the condensation resin and the methylene donor, the initial grip performance and the stable grip performance in the running / late period are synergistically improved while maintaining good wear resistance, and the performance balance is improved. It can be remarkably improved.

N ₂ SA of the carbon black is 151 m ² / g or more, preferably 160 m ² / g or more, more preferably 170 m ² / g or more. The N ₂ SA is preferably 300 m ² / g or less, more preferably 250 m ² / g or less, and still more preferably 200 m ² / g or less. Be greater than 300m ² / g, be less than 151m ² / g, there is a possibility that the effect of the present invention can not be obtained sufficiently.
In addition, N ₂ SA of carbon black is obtained in accordance with ASTM D 6556.

The carbon black has a specific surface area of cetyltrimethylammonium bromide (CTAB) of preferably 100 m ² / g or more, more preferably 150 m ² / g or more. Moreover, this CTAB specific surface area becomes like this. Preferably it is 300 m < ² > / g or less, More preferably, it is 250 m < ² > / g or less. If it is less than 100 m ² / g, the grip performance tends to decrease, and if it exceeds 300 m ² / g, good dispersion is difficult to obtain, and the wear resistance tends to decrease.
In addition, the CTAB specific surface area of carbon black is measured according to ASTM D 3765.

The content of the carbon black is 5 parts by mass or more, preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and particularly preferably 50 parts by mass when used as a high-performance tire with respect to 100 parts by mass of the rubber component. Part or more, particularly preferably 60 parts by weight or more, and most preferably 100 parts by weight or more. If it is less than 5 parts by mass, the ultraviolet cracking property is deteriorated, and there is a possibility that sufficient effects of improving wear resistance and grip performance cannot be obtained. Moreover, this content is 170 mass parts or less, Preferably it is 160 mass parts or less. When it exceeds 170 parts by mass, the workability and filler dispersibility are deteriorated, and the wear resistance may be lowered.
In order to add 115 parts by mass or more of the carbon black content, it is preferable to increase the liquid SBR as a plasticizer to ensure processability and filler dispersibility. When the amount of resin is increased, the initial grip is lowered.

In the present invention, in addition to the carbon black, a white filler may be blended. As the white filler, those commonly used in the rubber industry, for example, mica such as silica, calcium carbonate, sericite, etc. Aluminum hydroxide, magnesium oxide, magnesium hydroxide, clay, talc, alumina, titanium oxide, zirconium oxide and the like can be used. Among these, silica and aluminum hydroxide are preferable, and aluminum hydroxide is more preferable in that the wear resistance and grip performance can be obtained satisfactorily.

The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups.

_N 2 SA of the silica is preferably ^{100~300m 2 / g, 150~250m 2 /} g is more preferable. If it is less than 100 m ² / g, the wear resistance tends to decrease, and if it exceeds 300 m ² / g, the workability tends to decrease. N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-81.

When silica is blended, wet performance and low fuel consumption are expected, and the content thereof is preferably 10 parts by mass or more, more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 10 parts by mass, the reinforcing property of the rubber is insufficient, causing a problem in terms of durability. Moreover, this content becomes like this. Preferably it is 100 mass parts or less, More preferably, it is 80 mass parts or less. When it exceeds 100 parts by mass, the workability tends to deteriorate.

_N 2 SA of the aluminum hydroxide is preferably 5~120m ² / g. Outside the above range, wear resistance and grip performance may be deteriorated. The lower limit of the N ₂ SA is more preferably 10 m ² / g. Further, the upper limit of the N ₂ SA is more preferably 100 m ² / g, still more preferably 80 m ² / g.
In the present invention, N ₂ SA of aluminum hydroxide is a value measured by the BET method according to ASTM D3037-81.

When mix | blending aluminum hydroxide, the content becomes like this. Preferably it is 1-60 mass parts with respect to 100 mass parts of rubber components, More preferably, in the case of the tire for passenger cars, More preferably, it is 5-30 mass parts. The effect of this invention can fully be exhibited as it exists in the said range.

In the tread rubber composition of the present invention, in addition to the above components, compounding agents generally used in the tire industry, such as wax, zinc oxide, stearic acid, mold release agent, anti-aging agent, sulfur, etc. You may mix | blend materials, such as a vulcanizing agent and a vulcanization accelerator, suitably.

The sulfur used in the present invention is not particularly limited, and examples include those used in the rubber field such as tires. Specifically, powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, high dispersion Exemplified sulfur is exemplified. The sulfur content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 5 parts by mass or less, more preferably 2 parts by mass with respect to 100 parts by mass of the rubber component. Part or less, more preferably 1 part by weight or less. The effect of this invention is exhibited more suitably as it is in the said range.

The zinc oxide used in the present invention is not particularly limited, and examples thereof include those used in the rubber field such as tires. Here, fine zinc oxide can be suitably used among zinc oxides. Specifically, it is preferable to use zinc oxide having an average primary particle diameter of 200 nm or less, and more preferably 100 nm or less. Although the minimum of this average primary particle diameter is not specifically limited, Preferably it is 20 nm or more, More preferably, it is 30 nm or more. In addition, the average primary particle diameter of zinc oxide represents the average particle diameter (average primary particle diameter) converted from the specific surface area measured by the BET method by nitrogen adsorption. The specific surface area measured by the BET method by nitrogen adsorption _(N 2 SA) is preferably 10 to 50 m ² / g.
Incidentally, _N 2 SA of the zinc oxide is a value determined by the BET method in accordance with ASTM D3037-81.

When blending zinc oxide, the content of zinc oxide is preferably 0.5 to 10 parts by mass or less, more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. The effect of this invention is acquired more suitably as content of zinc oxide exists in the said range.

（式中、Ｒ^４〜Ｒ^７はそれぞれ独立に炭素数１〜１８の直鎖若しくは分岐鎖アルキル基、又は炭素数５〜１２のシクロアルキル基を表す。） The tread rubber composition in the present invention may contain zinc dithiophosphate instead of the fine zinc oxide. Examples of zinc dithiophosphate include compounds represented by the following formula (II) (zinc dialkyldithiophosphate). By blending zinc dithiophosphate, the effects of the present invention can be suitably exhibited.

(In the formula, R ^{4 to} R ⁷ each independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms.)

In the above formula (II), R ^{4 to} R ⁷ each independently represents a linear or branched alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 5 to 12 carbon atoms. Examples of the linear or branched alkyl group represented by R ^{4 to} R ⁷ include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a 4-methylpentyl group, a 2-ethylhexyl group, and an octyl group. Group, octadecyl group, and the like. On the other hand, examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group. Of these, easily dispersed in the rubber composition, and from the viewpoint of easy manufacturing, R ⁴ to R ⁷ is preferably a straight or branched chain alkyl group having 2 to 8 carbon atoms, n- A butyl group, an n-propyl group, an iso-propyl group, and an n-octyl group are more preferable.

Examples of the compound represented by the formula (II) include TP-50, ZBOP-S, ZBOP-50 manufactured by Rhein Chemie, and compounds similar to these (for example, R ^{4 to} R ⁷ are n-propyl groups, Iso-propyl group or n-octyl group) can be used.

The content of zinc dithiophosphate is preferably 0.2 to 15 parts by mass, more preferably 1 to 8 parts by mass with respect to 100 parts by mass of the rubber component. The effect of this invention can fully be exhibited as it exists in the said range.

The rubber composition in the present invention can be prepared by a known method that undergoes kneading steps such as a base kneading step and a finish kneading step. The kneading step can be performed, for example, by kneading these components using a kneader. A conventionally known kneader can be used, and examples thereof include a Banbury mixer, a kneader, and an open roll. Further, a re-kneading step may be performed after the base kneading step and before the finishing kneading step.

There may be a plurality of the base kneading steps. For example, a rubber component, carbon black, 3/6 to 5/6 amount of silica, silane coupling agent, in addition to a method of performing a base kneading step of kneading all components except sulfur and vulcanization accelerator, such as the rubber component X-kneading 3/6 to 5/6, kneaded by X-kneading, remaining silica, remaining silane coupling agent, Y-kneading kneading other components excluding sulfur and vulcanization accelerator, etc. It may be a base kneading step divided into two.

After the base kneading step, for example, a final kneading step (discharge temperature) in which the obtained kneaded product 1 is kneaded with components such as a vulcanizing agent such as sulfur and a vulcanization accelerator using a kneader similar to the above. In the present invention by performing a vulcanization step in which the obtained kneaded product 2 (unvulcanized rubber composition) is press-heated at 130 to 190 ° C. for 5 to 30 minutes. A rubber composition can be produced. In addition, when mix | blending zinc dithiophosphate, you may knead | mix the said component by finishing kneading.

The rubber composition is suitable for a tread of a pneumatic tire, particularly a tread (cap tread) of a racing tire.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition.
That is, the rubber composition containing the above components is extruded in accordance with the shape of the tread at an unvulcanized stage and molded together with other tire members on a tire molding machine by a normal method. Form a vulcanized tire. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The pneumatic tire of the present invention can be used for tires for passenger cars, trucks and buses, sports cars, two-wheeled motorbikes, competition vehicles, etc., and is particularly preferably used as a high-performance tire. The high-performance tire in the present invention is a tire that is particularly excellent in grip performance (particularly dry grip performance), and includes a concept including a competition tire used in a competition vehicle. The present invention can be suitably applied to competition tires, particularly competition dry tires used on dry road surfaces.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

<Preparation of terminal modifier>
Under a nitrogen atmosphere, 23.6 g of 3- (N, N-dimethylamino) propyltrimethoxysilane (manufactured by Amax Co., Ltd.) was added to a 100 ml volumetric flask, and anhydrous hexane (manufactured by Kanto Chemical Co., Ltd.) was further added. Was made to 100 ml.

<Example of copolymer production>
In a 30 L pressure-resistant vessel sufficiently purged with nitrogen, 18 L of n-hexane, 740 g of styrene (manufactured by Kanto Chemical Co., Inc.), 1260 g of butadiene and 10 mmol of tetramethylethylenediamine were added, and the temperature was raised to 40 ° C. Next, after adding 10 mL of butyl lithium, it heated up at 50 degreeC and stirred for 3 hours. Next, 11 mL of the terminal modifier was added and stirred for 30 minutes. After adding 15 mL of methanol and 0.1 g of 2,6-tert-butyl-p-cresol to the reaction solution, the reaction solution was put into a stainless steel container containing 18 L of methanol to collect aggregates. The obtained aggregate was dried under reduced pressure for 24 hours to obtain a modified SBR.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
SBR1: Toughden 4850 manufactured by Asahi Kasei Corporation (styrene content: 40% by mass, containing 50 parts by mass of oil with respect to 100 parts by mass of rubber solid content)
SBR2: Modified SBR prepared in the above copolymer production example (modified SBR obtained by reacting the modifier represented by the above formula (I), amount of bound styrene: 27% by mass, vinyl amount: 58% by mass, Tg: -27 ° C)
BR: CB24 manufactured by LANXESS Co., Ltd. (high cis BR synthesized using an Nd-based catalyst, cis content: 96% by mass, vinyl content: 0.7% by mass)
Silica: ULTRASIL VN3 (N ₂ SA: 175 m ² / g) manufactured by Evonik
Carbon Black 1: Show Black N110 (N ₂ SA: 142 m ² / g, CTAB specific surface area: 119 m ² / g) manufactured by Cabot Japan
Carbon black 2: HP180 manufactured by Orion Engineered Carbons (N ₂ SA: 175 m ² / g, CTAB specific surface area: 181 m ² / g)
Carbon black 3: HP160 (N ₂ SA: 165 m ² / g, CTAB specific surface area: 163 m ² / g) manufactured by Columbia Carbon Co., Ltd.
Silane coupling agent: Si75 manufactured by Evonik
Aluminum hydroxide 1: dry pulverized product of ATH # B manufactured by Sumitomo Chemical Co., Ltd. (average particle size: 0.4 μm, N ₂ SA: 35 m ² / g)
Aluminum hydroxide 2: Heidilite H-43 (average particle size: 0.75 μm, N ₂ SA: 6.7 m ² / g) manufactured by Showa Denko KK
Liquid SBR: L-SBR-820 (liquid SBR, Mw: 10,000) manufactured by Kuraray Co., Ltd.
Condensation resin 1: PR-X11061 manufactured by Sumitomo Bakelite Co., Ltd. (using o-cresol, m-cresol, and p-cresol as monomer components, total amount of free monomer components: 0.6% by mass, novolak-type phenol resin) Content: 99.4% by mass, softening point: 128 ° C., Mw: 1800, crosslinking reactive condensation resin)
Condensation resin 2: A resin in which the purification method was changed in the production of PR-X11061 and the total amount of free monomer components was changed (prototype A) (the monomer component was the same as PR-X11061, and the total amount of free alkylphenols: 1.5% by mass) Novolak type phenol resin content: 98.5% by mass, softening point: 124 ° C., Mw: 1880, crosslinkable reactive condensation resin)
Condensation resin 3: resin in which the purification method was changed in the production of PR-X11061 and the total amount of free monomer components was changed (prototype B) (the monomer component was the same as PR-X11061, the total amount of free alkylphenol: 5% by mass, novolak Type phenolic resin content: 95% by mass, softening point: 110 ° C., Mw: 2090, crosslinking reactive condensation resin)
Condensation resin 4: Sumikanol 611 (metacresol resin (using only m-cresol as the monomer component) (the amount of m-cresol in 100% by mass of the monomer component used in the resin production is 100) manufactured by Taoka Chemical Industries, Ltd. Mass%), free monomer component total amount: 3.5 mass%, content of novolac type phenol resin: 96 mass%, softening point: 101 ° C., Mw: 2000, cross-linking reactive condensation resin)
Condensation resin 5: Sumikanol 610 manufactured by Taoka Chemical Co., Ltd. Lot A (metacresol resin (using only m-cresol as monomer component (amount of m-cresol in 100% by mass of monomer component used for resin production) 100% by mass), free monomer component total amount: 8% by mass, novolac type phenol resin content: 91% by mass, softening point: 96 ° C., Mw: 2000, cross-linking reactive condensation resin)
Condensation resin 6: Sumikanol 610 manufactured by Taoka Chemical Co., Ltd. Lot B (metacresol resin (using only m-cresol as a monomer component (amount of m-cresol in 100% by mass of monomer component used for resin production) 100% by mass), free monomer component total amount: 12% by mass, novolac type condensation resin content: 87% by mass, softening point: 92 ° C., Mw: 2000, cross-linking reactive condensation resin)
Condensation resin 7: Pure product of Sumikanol 620 manufactured by Taoka Chemical Industry Co., Ltd. (prototype C) (modified resorcinol resin (resorcinol, m-octylphenol, m-cresol used as monomer components), total amount of free monomer components: 1 0.0% by mass, content of novolac type condensation resin: 98% by mass, softening point: 105 ° C., Mw: 1500, cross-linking reactive condensation resin)
Condensation resin 8: Sumikanol 620 (modified resorcinol resin (using resorcinol, m-octylphenol, m-cresol as monomer components), manufactured by Taoka Chemical Co., Ltd.), total amount of free monomer components: 19% by mass, novolak type condensation resin Content: 81 mass%, softening point: 100 ° C., Mw: 1500, crosslinkable reactive condensation resin)
Condensation resin 9: PR12686 manufactured by Sumitomo Bakelite Co., Ltd. (cashew oil-modified phenol resin (using only phenol as the monomer component (the amount of phenol in 100% by mass of the monomer component used in the production of the resin is 100% by mass)), (Free phenol content: 0.2% by mass, content of novolac-type phenol resin: 99.8% by mass, softening point: 94 ° C.)
Alkylphenol alkyne condensation resin: Koresin (condensation resin of pt-butylphenol and acetylene, softening point: 145 ° C., Tg: 98 ° C.) manufactured by BASF
Styrene acrylic resin 1: ARUFON UC-3900 (solvent-free styrene acrylic resin (carboxyl group-containing), Tg: 77 ° C., non-crosslinking reactive grip improving resin) manufactured by Toagosei Co., Ltd.
Styrene acrylic resin 2: ARUFON UC-3920 (solvent-free styrene acrylic resin (carboxyl group-containing), Tg: 102 ° C.) manufactured by Toagosei Co., Ltd.
Aromatic terpene resin: YS resin TO125 manufactured by Yashara Chemical Co., Ltd. (aromatic modified terpene resin, softening point: 125 ° C., Tg: 65 ° C.)
Terpene phenol resin: Sylvares TP115 manufactured by Arizona Chemical Co. (terpene phenol resin, softening point: 115 ° C., Tg: 57 ° C.)
Methylene donor 1: Noxeller H (Hexamethylenetetramine (HMT)) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Methylene donor 2: Sumikanol 507AP (hexamethylol melamine pentamethyl ether (HMMPME)) manufactured by Taoka Chemical Co., Ltd.
Methylene donor 3: Cylet 964 RPC (Hexamethoxymethylmelamine (HMMM)) manufactured by Mitsui Cytec Co., Ltd.
Oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Anti-aging agent 1: Antigen 6C (N-phenyl-N ′-(1,3-dimethyl) -p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Anti-aging agent 2: Nocrack 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Zinc oxide 1: Zincock Super F-2 manufactured by Hakusuitec Co., Ltd. (average primary particle size: 65 nm, N ₂ SA: 20 m ² / g)
Zinc oxide 2: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Zinc dithiophosphate: Rhenogran TP-50 (compound represented by the above formula (II) (zinc dialkyldithiophosphate), R ^{4 to} R, manufactured by Rhein Chemie ⁷ : n-butyl group, active ingredient: 50% by mass)
Powder sulfur containing 5% oil: HK-200-5 manufactured by Hosoi Chemical Co., Ltd.
Vulcanization accelerator 1: Noxeller DM (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noxeller TOT-N (tetrakis (2-ethylhexyl) thiuram disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator 3: Noxeller NS-G (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator 4: Noxeller D (1,3-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Examples 1-1 to 1-21 and Comparative Examples 1-1 to 1-11>
In accordance with the formulation shown in Table 1, compounding materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at a discharge temperature of 150 ° C. using 4.0 L Banbury manufactured by Kobe Steel. The obtained kneaded material is re-kneaded for 4 minutes at a discharge temperature of 150 ° C., sulfur and a vulcanization accelerator are added to the re-kneaded kneaded material, and the discharge temperature is 95 ° C. using an open roll. And kneaded for 4 minutes to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread shape, bonded together with other tire members on a tire molding machine, vulcanized at 160 ° C. for 20 minutes, and a test tire (tire size: 245). / 40R18).

<Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-3>
According to the contents shown in Table 2, using 4.0 L Banbury manufactured by Kobe Steel, first, the total amount of (X kneaded) rubber component and carbon black, and 2/3 each of silica and silane coupling agent. Kneaded for 5 minutes under the condition of a discharge temperature of 150 ° C., then (Y kneading) the remaining materials other than sulfur and vulcanization accelerator were added and kneaded for 4 minutes under the condition of a discharge temperature of 155 ° C. A kneaded paste was obtained. Finally, (finishing kneading) Sulfur and a vulcanization accelerator are added to the obtained kneaded product, and kneaded for 4 minutes under an exhaust temperature of 95 ° C. using an open roll to obtain an unvulcanized rubber composition. It was. The obtained unvulcanized rubber composition was molded into a tread shape, bonded together with other tire members on a tire molding machine, vulcanized at 160 ° C. for 20 minutes, and a test tire (tire size: 245). / 40R18).

The following evaluation was performed about the test tire obtained by the said manufacture. The results are shown in Tables 1 and 2. The reference comparative examples in Tables 1 and 2 were Comparative Examples 1-1 and 2-1, respectively.

(Initial grip performance)
The test tire was mounted on a 2000 cc domestic FR vehicle, and the vehicle traveled 10 laps on a dry asphalt road test course. At that time, the test driver evaluated the control stability during steering in the second lap, and an index was displayed with the reference comparative example as 100 (initial grip performance index). The larger the value, the higher the initial grip performance. When the index value was 104 or more, it was judged to be good.

(Grip performance during and late driving)
The test tire was mounted on a 2000 cc domestic FR vehicle, and the vehicle traveled 10 laps on a dry asphalt road test course. At that time, the test driver compared and evaluated the stability of the control during steering of the best lap and the final lap, and the index was displayed as a reference comparative example of 100. The larger the value, the smaller the decrease in grip performance during and late driving on the dry road surface, indicating that stable grip performance during and during driving can be obtained better. When the index value was 104 or more, it was judged to be good.

(Abrasion resistance)
The test tire was mounted on a domestic FR vehicle with a displacement of 2000 cc, and the vehicle was run on a dry asphalt road test course. The remaining groove amount of the tire tread rubber at that time was measured (7.0 mm when new), and the index was displayed with the remaining groove amount of the reference comparative example being 100 (wear resistance index). It shows that abrasion resistance is so high that a numerical value is large. When the index value was 100 or more, it was judged to be good.

From Tables 1 and 2, in Examples using a predetermined amount of a specific condensation resin and a methylene donor and a specific carbon black, the initial grip performance and the running / stable state were stabilized while ensuring good wear resistance. It was revealed that the grip performance (particularly the initial grip performance on a dry road surface and the stable grip performance during and after driving) can be improved at a high level at the same time, and the performance balance is remarkably improved.
Moreover, it turned out from the comparison of Example 1-1 and Comparative Examples 1-1, 1-9, and 1-10 that the effect of the present invention is synergistically improved. In these blending examples, the amount of oil blended was adjusted in order to adjust the hardness to the same level.

Claims (10)

A rubber component, a carbon black having a nitrogen adsorption specific surface area of 151 m ² / g or more, a condensation resin obtained by substituting at least one hydrogen of a benzene ring with a hydroxyl group and / or an alkyl group, and formaldehyde, and a methylene donor A pneumatic tire having a tread produced using a tread rubber composition comprising:
5 to 170 parts by mass of the carbon black, 0.5 to 20 parts by mass of the condensation resin, and 0.04 to 10 parts by mass of the methylene donor with respect to 100 parts by mass of the rubber component,
A pneumatic tire in which a content of a free monomer component contained in the condensed resin is 7% by mass or less. The pneumatic tire according to claim 1, wherein the condensed resin is an alkylphenol resin obtained from at least two compounds selected from the group consisting of 2-alkylphenol, 3-alkylphenol, and 4-alkylphenol, and formaldehyde. The pneumatic tire according to claim 1 or 2, wherein the condensation resin is a resin obtained from 2-alkylphenol, 3-alkylphenol, 4-alkylphenol, and formaldehyde. The pneumatic tire according to any one of claims 1 to 3, wherein the methylene donor is at least one compound selected from the group consisting of hexamethylenetetramine, hexamethoxymethylol melamine, and hexamethylol melamine pentamethyl ether. The pneumatic tire according to any one of claims 1 to 4, wherein the methylene donor is hexamethylenetetramine. The pneumatic tire according to claim 2 or 3, wherein the 2-alkylphenol, the 3-alkylphenol, and the 4-alkylphenol are o-cresol, m-cresol, and p-cresol, respectively. The pneumatic tire according to any one of claims 1 to 6, wherein a content of a free monomer component contained in the condensed resin is 1% by mass or less. The pneumatic tire according to any one of claims 1 to 7, wherein a softening point of the condensed resin is 98 to 140 ° C. The pneumatic tire according to any one of claims 1 to 8, wherein the condensation resin has a novolac type condensation resin content of 93 to 100% by mass. The pneumatic tire according to any one of claims 1 to 9, wherein the tread rubber composition contains 0.2 to 15 parts by mass of zinc dithiophosphate with respect to 100 parts by mass of the rubber component.