JP5389562B2 - Rubber composition for tire tread and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition for a tire tread used for a tread of a pneumatic tire, and a pneumatic tire using the same.

  For pneumatic tires, particularly racing tires such as rally tires and semi-racing tires, grip performance on dry road surfaces (dry grip performance), cut chip resistance, and wear resistance are important.

  As a method for improving dry grip properties, for example, a method such as increasing the filling of a reinforcing filler or softening agent or using a rubber polymer having a high glass transition point is used. In addition, there are problems such as deterioration of wear resistance, and further improvements in dry grip properties and cut chip resistance are demanded. Further, as a technique for improving cut-chip resistance, there is a technique of adding a resin typified by rosin or the like (for example, see Patent Document 1 below), but there is a demerit that wear resistance is lowered.

  By the way, the technique which adds saccharides to a rubber composition is known conventionally, for example, the following patent document 2 has abrasion resistance and aging resistance, without impairing fracture characteristics, wet grip property, exothermic property, and workability. In order to improve the properties, monosaccharides, polysaccharides higher than disaccharides, and derivatives thereof (for example, sugar alcohol, deoxy sugar, amino sugar, glycoside, uronic acid, sugar fatty acid ester) are added. It has been proposed. However, it has not been known to incorporate an alkyl group-modified sugar derivative unique to the present invention, and the advantageous action and effect thereof has not been known.

JP-A-11-116734 Japanese Patent Laid-Open No. 11-071481

  The present invention has been made in view of the above points, and an object thereof is to provide a rubber composition for a tire tread that can improve dry grip properties and cut chip resistance without impairing wear resistance. To do.

  The present inventor has been intensively studied in view of the above points, and by incorporating a specific sugar derivative modified with an alkyl group together with a reinforcing filler with respect to a specific diene rubber component, wear resistance is improved. It was found that the dry grip and cut-chip resistance can be greatly improved while suppressing the deterioration. The present invention is based on such knowledge.

That is, the tire tread rubber composition according to the present invention has a general formula (described later) with respect to 100 parts by weight of a diene rubber component containing 50 parts by weight or more of styrene butadiene rubber having a glass transition point of −50 ° C. or more and 0 ° C. or less. It contains 0.1 to 20 parts by weight of alkyl-D-glucopyranoside represented by 1) and 60 to 200 parts by weight of a reinforcing filler.

  The pneumatic tire according to the present invention includes a tread made using such a rubber composition.

  According to the present invention, it is possible to improve dry grip properties and cut chip resistance while suppressing deterioration of wear resistance.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  In the rubber composition according to the present invention, as the diene rubber component, styrene butadiene rubber (that is, styrene-butadiene copolymer, SBR) having a glass transition point of −50 ° C. or higher and 0 ° C. or lower is used. The thing containing 50 weight part or more in a weight part is used. The use of styrene butadiene rubber having a relatively high glass transition point in this way contributes to improvement in dry grip properties. A more preferable range of the glass transition point is −50 to −10 ° C. Here, the glass transition point (Tg) is a value (temperature increase rate 20 ° C./min) measured using differential scanning calorimetry (DSC) in accordance with JIS K7121.

  If the diene rubber component contains at least 50 parts by weight of at least one styrene butadiene rubber having a glass transition point of −50 to 0 ° C. in 100 parts by weight of the rubber component, the styrene butadiene rubber alone (ie, 100 parts by weight) or a blend of 50 parts by weight or more of the styrene butadiene rubber and 50 parts by weight or less of another diene rubber. When blending, it is more preferable to use 70 parts by weight or more of the styrene butadiene rubber in 100 parts by weight of the rubber component.

  Other diene rubbers to be blended are not particularly limited. For example, natural rubber (NR), polyisoprene rubber (IR), styrene butadiene rubber having a glass transition point of less than −50 ° C., polybutadiene rubber (BR). Styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, nitrile rubber, and the like. These may be used alone or in combination of two or more. .

  The alkyl group-modified sugar derivative blended in the rubber composition according to the present invention is obtained by reacting glucose with a primary alcohol. As glucose, D-glucose or L-glucose may be used, but natural glucose, that is, D-glucose is preferably used. Moreover, as a primary alcohol, it is preferable to use a C1-C25 saturated alcohol.

  Therefore, as the alkyl group-modified sugar derivative, it is preferable to use alkyl-D-glucopyranoside whose alkyl group has 1 to 25 carbon atoms. Using such an alkyl group-modified sugar derivative derived from natural glucose also leads to a reduction in petroleum resource-derived raw materials. In this case, the glucopyranoside may be α-type (that is, alkyl-α-D-glucopyranoside), β-type (that is, alkyl-β-D-glucopyranoside), or a mixture of both. Here, as the alkyl group, for example, methyl group, ethyl group, n-propyl group, n-butyl group, isobutyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, isohexyl group, neohexyl group , Heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, heicosyl group, docosyl group, tricosyl Group, tetracosyl group and pentacosyl group.

The alkyl group-modified sugar derivative is particularly preferably an alkyl-D-glucopyranoside represented by the following general formula (1), and particularly preferably an alkyl-α-D represented by the following general formula (2). -Using glucopyranoside.

  In said formula (1) and (2), n is an integer of 0-24. If the carbon number of the alkyl group represented by (n + 1) is too large, the contribution of the glucose moiety becomes small and the effect of addition tends to approach paraffin oil, which may cause a decrease in wear resistance, etc. It is preferable that it is 25 or less. n is more preferably an integer of 0 to 12, and still more preferably an integer of 2 to 10.

Alkyl-D-glucopyranoside is obtained by reacting glucose with a primary alcohol as shown in the following formula (3). In this reaction, for example, glucose and primary alcohol are heated and reacted in the presence of hydrochloric acid and a cation exchange resin (see JP-B-50-13770), and a cation exchange resin (styrene and divinylbenzene are used as a catalyst). A method in which glucose and a primary alcohol are reacted using a three-dimensional polymer substrate produced by condensation with a sulfonic acid group bonded as an exchange group as a fixed bed (see JP-A-6-92984), A method of reacting glucose and primary alcohol using transglucosidase (α-glucosidase) as a catalyst (see JP-A-7-87992), and converting glucose and primary alcohol into clay minerals (montmorillonite, beidellite, saponite, A method of reacting in the presence of hectorite (Japanese Patent Laid-Open No. 10-204095) Broadcast reference) can be carried out by such.

  The alkyl group-modified sugar derivative can be blended at 0.1 to 20 parts by weight with respect to 100 parts by weight of the diene rubber component. If the blending amount is less than 0.1 parts by weight, the effect of addition is insufficient. Conversely, if the blending amount exceeds 20 parts by weight, the abrasion resistance deteriorates although the dry grip property and the cut-chip resistance are excellent. The lower limit of the amount of the alkyl group-modified sugar derivative is more preferably 1 part by weight or more, still more preferably 3 parts by weight or more, and the upper limit is more preferably 10 parts by weight or less, still more preferably 5 parts by weight or less. .

  In the rubber composition according to the present invention, the reinforcing filler is blended in an amount of 60 to 200 parts by weight with respect to 100 parts by weight of the diene rubber. When the compounding amount of the reinforcing filler is less than 60 parts by weight, the dry grip property, cut chip resistance, and wear resistance are inferior. If the blending amount exceeds 200 parts by weight, the workability deteriorates. The compounding amount of the reinforcing filler is more preferably 60 to 150 parts by weight, still more preferably 60 to 120 parts by weight.

  Examples of the reinforcing filler include carbon black, silica, and the like. Preferably, the main component is carbon black, that is, carbon black alone, or 60% by weight or more of carbon black and 40% of silica. % Or less. The compounding amount of carbon black is preferably 40 to 200 parts by weight, more preferably 50 to 120 parts by weight with respect to 100 parts by weight of the diene rubber component.

The carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of 70 to 150 m ² / g, that is, ASTM grade, SAF class (N100 series), ISAF class (N200 series), HAF class (N300). Is preferably used. If the nitrogen adsorption specific surface area is too small, the wear resistance and cut chip resistance tend to be inferior, and the effect of improving dry grip properties is also reduced. More preferably, carbon black having a nitrogen adsorption specific surface area of 100 to 150 m ² / g is used. Here, the nitrogen adsorption specific surface area is a value measured according to JIS K6217-2.

The silica is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Among these, wet silica is preferable. By using silica together with the carbon black, dry grip properties and cut chip resistance can be further improved. When silica is used in combination, it is preferably blended at 10 to 40 parts by weight per 100 parts by weight of the reinforcing filler. Although not particularly limited, as silica, having colloidal properties of nitrogen adsorption specific surface area (BET) 150~250m ² / g by BET method is preferably used, more preferably at 180~230m ² / g . The BET of silica is measured according to the BET method described in ISO 5794.

  In addition to the components described above, the rubber composition according to the present invention includes zinc white, stearic acid, anti-aging agent, softener, vulcanization accelerator, vulcanizing agent, vulcanizing aid, resins, and the like. Various additives generally used in rubber compositions for treads can be blended. As the vulcanizing agent, for example, sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and oil-treated sulfur is preferably used, and is not particularly limited, but sulfur is added to 100 parts by weight of the diene rubber component. It is preferable to mix | blend with 0.5-3.0 weight part with respect to it, More preferably, it is 1.0-2.0 weight part.

  The rubber composition can be prepared by kneading using a commonly used Banbury mixer, a mixer such as a roll or a kneader. The obtained rubber composition can be used for treads of various pneumatic tires, and a pneumatic radial tire provided with the treads can be produced by vulcanization molding according to a conventional method. The tires to be applied are not particularly limited, such as passenger car tires, heavy duty tires such as trucks and buses, but more preferably rally tires used for off-road races traveling on rough roads such as dirt courses, etc. It is used for racing tires such as semi-racing tires that require high dry grip.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, according to the composition (parts by weight) shown in Table 1 below, each component was added and mixed according to a conventional method to prepare rubber compositions of Examples and Comparative Examples. Each component in Table 1 is as follows.

SBR1: “SBR0122” manufactured by JSR Corporation (oil-extended styrene-butadiene rubber in which 34 parts by weight of oil is added to 100 parts by weight of rubber polymer, glass transition point = −40 ° C.)
SBR2: “Toughden 4850” manufactured by Asahi Kasei Corporation (oil-extended styrene-butadiene rubber in which 50 parts by weight of oil is added to 100 parts by weight of rubber polymer, glass transition point = −25 ° C.)
SBR3: “SBR1712” manufactured by JSR Corporation (oil-extended styrene-butadiene rubber in which 37.5 parts by weight of oil is added to 100 parts by weight of rubber polymer, glass transition point = −64 ° C.)
・ Natural rubber (NR): RSS3 ・ Carbon black SAF: “Seast 9” (N ₂ SA = 142 m ² / g) manufactured by Tokai Carbon Co., Ltd.
Carbon black ISAF: “Seast 7HM” manufactured by Tokai Carbon Co., Ltd. (N ₂ SA = 126 m ² / g)
Carbon black HAF: “Seast KH” manufactured by Tokai Carbon Co., Ltd. (N ₂ SA = 93 m ² / g)
Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd. (BET = 205 m ² / g)
・ Rosin resin: “Chinese rosin” manufactured by Arakawa Chemical Industries, Ltd.
・ Glucose: “D-(+)-glucose” manufactured by Nacalai Tesque
Alkyl group-modified sugar derivative A: butyl-α-D-glucopyranoside, n = 3 in formula (2), “GS-AG4S” manufactured by Gunei Chemical Industry Co., Ltd.
Alkyl group-modified sugar derivative B: octyl-α-D-glucopyranoside, n = 7 in formula (2), “GS-AG8S” manufactured by Gunei Chemical Industry Co., Ltd.
Alkyl group-modified sugar derivative C: Decyl-α-D-glucopyranoside, n = 9 in formula (2), “GS-AG10S” manufactured by Gunei Chemical Industry Co., Ltd.

  In each rubber composition, 3 parts by weight of zinc white (“Zinc Hana 1” manufactured by Mitsui Kinzoku Mining Co., Ltd.) and stearic acid (“Lunac” manufactured by Kao Co., Ltd.) per 100 parts by weight of diene rubber S-25 ") 2 parts by weight, anti-aging agent (Sumitomo Chemical Co., Ltd." Antigen 6C ") 1 part by weight, sulfur (Tsurumi Chemical Co., Ltd." powder sulfur ") 1.5 parts by weight, vulcanization acceleration 2.0 parts by weight of the agent CBS (“Sunseller CM” manufactured by Sanshin Chemical Industry Co., Ltd.) and 1.0 part by weight of the vulcanization accelerator DPG (“Soxinol D” manufactured by Sumitomo Chemical Co., Ltd.) were blended.

  About each obtained rubber composition, while measuring a vulcanization | cure speed | rate, it vulcanizes | cures at 150 degreeC x 30 minutes, and produces the test piece of a predetermined shape, and using the obtained test piece, dry grip property, Cut chip properties (breaking strength, tear strength) and wear resistance were measured and evaluated. Each measurement / evaluation method is as follows.

-Vulcanization speed t50: Mooney scorch test in accordance with JIS K6300 was performed using a rheometer (L-shaped rotor), and the t50 value at the time of measurement at a temperature of 150 ° C for 1 minute was obtained. A smaller value indicates a faster vulcanization rate.

・ Dry grip property: Using a spectrometer manufactured by Toyo Seiki Co., Ltd., tan δ (loss tangent) as a viscoelastic property at a frequency of 10 Hz, an initial elongation of 10%, a strain amplitude of ± 2%, and a temperature of 20 ° C. was measured. The value was expressed as an index where the value of 1 was 100. The larger the index, the larger the tan δ. It is known that tan δ near 20 ° C. under a frequency of about 10 Hz correlates well with the dry grip property when used as a tread rubber, and that the larger the tan δ, the better the dry grip property. Therefore, the larger the index, the better the dry grip property.

Cut resistance: The breaking strength (MPa) was subjected to a tensile test (dumbbell No. 3) according to JIS K6251. For the tear strength (kN / m), a tear test (crescent dumbbell) was performed according to JIS K6252. It is known that the breaking strength and tear strength have a correlation with cut chip resistance, and the larger the value of both, the better the cut chip resistance.

-Abrasion resistance: A wear test was performed in accordance with JIS K6264 using a Lambourn abrasion tester under the conditions of a slip rate of 30%, a load load of 40 N, and a sandfall amount of 20 g / min. The results were displayed as an index with the wear amount of Comparative Example 1 being 100 (“Wear amount of Comparative Example 1” × 100 / “Wear amount of each test piece”). The higher the index, the better the wear resistance.

  The results are as shown in Table 1, and in Examples 1 to 11, with respect to Comparative Example 1 as a control, the rupture strength and tear strength were improved while suppressing deterioration of wear resistance, and the cut-resistant chip. As a result, the dry grip properties were greatly improved. Also, the vulcanization speed was high. In Example 6 in which silica was used in combination, dry grip properties and cut chip resistance were further improved as compared to Example 4 in which the same amount of the same alkyl group-modified sugar derivative was blended.

  On the other hand, in Comparative Example 2, although the alkyl group-modified sugar derivative was blended, the dry grip property was lower than that of Comparative Example 1 because the ratio of styrene butadiene rubber was small. In Comparative Example 3, since the glass transition point of the styrene butadiene rubber was too low, the dry grip property was lowered. In Comparative Example 4, the amount of carbon black was too small, the wear resistance and cut chip resistance were inferior, and the dry grip property was also lower than that of Comparative Example 1. In Comparative Example 5, a rosin resin was blended in place of the alkyl group-modified sugar derivative. In that case, although the chip resistance and dry grip resistance were slightly improved, the effect was small and the wear resistance was also reduced. Sex deteriorated. In Comparative Example 6, glucose is added as a saccharide instead of an alkyl group-modified sugar derivative. However, glucose does not provide an effect of improving dry grip properties, and it has cut chip resistance and wear resistance. It got worse. In Comparative Example 7, although the compounding amount of the alkyl group-modified sugar derivative was too large and the dry grip property and cut chip resistance were excellent, the wear resistance was deteriorated.

Claims (4)

For 100 parts by weight of a diene rubber component containing 50 parts by weight or more of styrene butadiene rubber having a glass transition point of −50 ° C. or more and 0 ° C. or less
A rubber composition for a tire tread containing 0.1 to 20 parts by weight of an alkyl-D-glucopyranoside represented by the following general formula (1) and 60 to 200 parts by weight of a reinforcing filler.

(In the formula, n is an integer of 0 to 24.) N is claim 1 for a tire tread rubber composition according an integer of 0 to 12 in the general formula (1). The reinforcing fillers according to claim 1 or 2 for a tire tread rubber composition according to the nitrogen adsorption specific surface area carbon black of 70~150m 2 / ^g. The pneumatic tire provided with the tread which uses the rubber composition of any one of Claims 1-3 .