JP2023074717A - Rubber composition for tires - Google Patents

Abstract

To provide a rubber composition for tires which has excellent hardness while maintaining wear resistance without reducing the content of sulfur.SOLUTION: A pneumatic tire contains: a rubber component containing 70-100 mass% of a hydrogenated copolymer which is obtained by hydrogenating an aromatic vinyl-conjugated diene copolymer and has a weight average molecular weight measured by gel permeation chromatography of 300,000 or more and a hydrogenation rate of a conjugated diene moiety of 80 mol% or more; silica; a silane coupling agent; and sulfur. The content of the silane coupling agent is 9-14 mass% based on the silica.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition for tires.

If the hardness of pneumatic tires is insufficient, the handling properties of the vehicle deteriorate, so the rubber composition for tires is required to have hardness.

WO2018/143111 JP 2016-138198 A

Methods for increasing the hardness of the tire rubber composition include increasing the amount of the silane coupling agent. However, in a rubber composition mainly composed of a diene rubber, when the amount of the silane coupling agent is increased, although the hardness is increased, the cross-linking points are concentrated at one point, and the wear resistance tends to be deteriorated.

Regarding this problem, in Patent Document 1, when the amount of the silane coupling agent is increased, the deterioration of wear resistance is suppressed by reducing the sulfur content. If this cannot be maintained, the handling performance may deteriorate.

SUMMARY OF THE INVENTION In view of the above points, an object of the present invention is to provide a rubber composition for tires that can provide excellent hardness while maintaining wear resistance without reducing the sulfur content.

In addition, in Patent Document 2, by blending a predetermined silica and a predetermined silane coupling agent, an increase in Mooney viscosity is suppressed, and a rubber composition having good workability, wear resistance, and mechanical strength can be obtained. is described, but does not contain a hydrogenated copolymer.

In order to solve the above problems, the rubber composition for tires according to the present invention is a hydrogenated copolymer in which an aromatic vinyl-conjugated diene copolymer is hydrogenated, and is measured by gel permeation chromatography. A rubber component containing 70 to 100% by mass of a hydrogenated copolymer having a weight average molecular weight of 300,000 or more and a conjugated diene portion having a hydrogenation rate of 80 mol% or more, silica, a silane coupling agent, and sulfur. and the content of the silane coupling agent is 9 to 14% by mass with respect to silica.

ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for tires which has the outstanding hardness is obtained, maintaining abrasion resistance, without reducing content of sulfur.

Matters related to the implementation of the present invention will be described in detail below.

The rubber composition for tires according to the present embodiment is a hydrogenated copolymer obtained by hydrogenating an aromatic vinyl-conjugated diene copolymer, and has a weight average molecular weight of 300,000 or more as measured by gel permeation chromatography. A rubber component containing 70 to 100% by mass of a hydrogenated copolymer in which the hydrogenation rate of the conjugated diene portion is 80 mol% or more, silica, a silane coupling agent, and sulfur, and a silane cup The content of the ring agent shall be 9 to 14 mass % with respect to silica.

The rubber component is a hydrogenated copolymer obtained by hydrogenating an aromatic vinyl-conjugated diene copolymer, and has a weight average molecular weight of 300,000 or more as measured by gel permeation chromatography. It contains a hydrogenated copolymer with an addition rate of 80 mol % or more. Here, in this specification, "weight average molecular weight measured by gel permeation chromatography (GPC)" means using a differential refractive index detector (RI) as a detector, using tetrahydrofuran (THF) as a solvent, The measurement temperature is 40° C., the flow rate is 1.0 mL/min, the concentration is 1.0 g/L, and the injection amount is 40 μL. The hydrogenation rate is a value calculated from the spectral reduction rate of the unsaturated bond portion of the spectrum obtained by measuring H ¹ -NMR.

The aromatic vinyl constituting the aromatic vinyl-conjugated diene copolymer is not particularly limited, but examples include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4 -cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. These may be used alone or in combination of two or more.

The conjugated diene constituting the aromatic vinyl-conjugated diene copolymer is not particularly limited, but examples include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1 , 3-butadiene, 1,3-hexadiene, and the like. These may be used alone or in combination of two or more.

Although the aromatic vinyl-conjugated diene copolymer is not particularly limited, it is preferably a copolymer of styrene and 1,3-butadiene (styrene-butadiene copolymer). Therefore, the hydrogenated copolymer is preferably a hydrogenated styrene-butadiene copolymer. Further, the hydrogenated copolymer may be a random copolymer, a block copolymer, or an alternating copolymer.

The hydrogenated copolymer can be synthesized, for example, by synthesizing an aromatic vinyl-conjugated diene copolymer and subjecting it to hydrogenation treatment. The method for synthesizing the aromatic vinyl-conjugated diene copolymer is not particularly limited, but solution polymerization method, gas phase polymerization method, bulk polymerization method and the like can be mentioned, and solution polymerization method is particularly preferred. Moreover, the polymerization system may be either a batch system or a continuous system. A commercially available aromatic vinyl-conjugated diene copolymer can also be used.

The hydrogenation method is not particularly limited, and hydrogenation may be performed by a known method under known conditions. Usually, it is carried out at 20 to 150° C. under hydrogen pressure of 0.1 to 10 MPa in the presence of a hydrogenation catalyst. The hydrogenation rate can be arbitrarily selected by changing the amount of the hydrogenation catalyst, the hydrogen pressure during the hydrogenation reaction, the reaction time, and the like. As a hydrogenation catalyst, a compound containing any one of metals of Groups 4 to 11 of the periodic table can be used. For example, compounds containing Ti, V, Co, Ni, Zr, Ru, Rh, Pd, Hf, Re, Pt atoms can be used as hydrogenation catalysts. More specific hydrogenation catalysts include metallocene compounds such as Ti, Zr, Hf, Co, Ni, Pd, Pt, Ru, Rh, and Re; Supported heterogeneous catalysts supported on a carrier such as silica, alumina, diatomaceous earth; Homogeneous Ziegler catalysts in which an organic salt or acetylacetone salt of a metal element such as Ni or Co is combined with a reducing agent such as organic aluminum; Organometallic compounds or complexes such as Ru and Rh; fullerenes and carbon nanotubes in which hydrogen is occluded;

The hydrogenation rate of the hydrogenated copolymer (ratio of hydrogenation to the conjugated diene portion of the aromatic vinyl-conjugated diene copolymer) is 80 mol% or more, preferably 80 to 95 mol%, More preferably 85 to 95 mol %, still more preferably 90 to 95 mol %. When the hydrogenation rate is 80 mol % or more, the effect of improving wear resistance by homogenizing cross-linking is excellent.

The weight average molecular weight of the hydrogenated copolymer is not particularly limited as long as it is 300,000 or more, but it is preferably 300,000 to 2,000,000, more preferably 300,000 to 1,000,000, and 300,000 to 600,000. is more preferable.

The rubber component may contain diene rubbers other than the hydrogenated copolymer, such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), and styrene-butadiene rubber (SBR). , styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, and the like. These diene rubbers may be used singly or in combination of two or more.

The content of the hydrogenated copolymer in the rubber component is not particularly limited, but is preferably 70 to 100% by mass, more preferably 80 to 100% by mass. When the content of the hydrogenated copolymer in the rubber component is within the above range, abrasion resistance is easily maintained even when the silane coupling agent is blended in a large amount without reducing the sulfur content.

The rubber composition for tires according to the present embodiment contains silica and a silane coupling agent. Silica is not particularly limited, but wet silica such as wet sedimentation silica and wet gel silica is preferably used. The content of silica is 30 to 100 parts by mass, preferably 50 to 80 parts by mass, per 100 parts by mass of the rubber component.

Silica is contained as a reinforcing filler, and in addition to this, carbon black may be used in combination. That is, the reinforcing filler may be silica alone or a combination of silica and carbon black. A combination of silica and carbon black is preferred. The content of the reinforcing filler is not particularly limited, and is preferably 30 to 150 parts by mass, more preferably 30 to 100 parts by mass, more preferably 50 to 80 parts by mass with respect to 100 parts by mass of the rubber component. Part is more preferred.

Carbon black is not particularly limited, and various known varieties can be used. The content of carbon black is preferably 1 to 70 parts by mass, more preferably 1 to 30 parts by mass, per 100 parts by mass of the rubber component.

Although the silane coupling agent is not particularly limited, sulfide silane, mercapto silane, and the like are preferably used. The content of the silane coupling agent is 9 to 14% by mass, preferably 9 to 12% by mass, based on the silica content. When the content of the silane coupling agent is within the above range, it is easy to obtain excellent hardness while maintaining wear resistance.

The rubber composition for tires according to the present embodiment contains, as the vulcanizing agent, sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. It is preferably 0.5 to 4 parts by mass, more preferably 1 to 3 parts by mass, based on 100 parts by mass of the rubber component.

The rubber composition for a tire according to the present embodiment can obtain excellent hardness while maintaining wear resistance by containing a silane coupling agent in a predetermined content. Although this mechanism is not clear, it can be guessed as follows. When the amount of the silane coupling agent is increased in a compound mainly composed of a normal diene rubber, the cross-linking points are concentrated at one point, resulting in deterioration of abrasion resistance. On the other hand, when the amount of silane coupling agent is increased in a formulation mainly composed of a hydrogenated copolymer, the amount of double bonds in the hydrogenated copolymer is small. Since it spreads, it can be inferred that the hardness could be increased while maintaining the wear resistance.

In addition to the components described above, the rubber composition for tires according to the present embodiment contains processing aids, zinc oxide, stearic acid, softeners, plasticizers, liquid rubbers, and resins that are commonly used in the rubber industry. , waxes, anti-aging agents, vulcanization accelerators, etc., can be appropriately blended within the usual range.

Vulcanization accelerators include sulfenamide vulcanization accelerators, guanidine vulcanization accelerators, dithiocarbamate vulcanization accelerators, thiuram vulcanization accelerators, thiazole vulcanization accelerators, and thiourea vulcanization accelerators. Accelerators and the like can be used. Among these, sulfenamide-based vulcanization accelerators, guanidine-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators are preferred.

Examples of sulfenamide vulcanization accelerators include N-cyclohexyl-2-benzothiazolylsulfenamide (CZ), N-tert-butyl-2-benzothiazolylsulfenamide (NS), N-oxy diethylene-2-benzothiazolylsulfenamide (MBS), N,N-diisopropyl-2-benzothiazolylsulfenamide (DZ).

Guanidine-based vulcanization accelerators include, for example, 1,3-diphenylguanidine (D) and di-O-tolylguanidine (DT).

Dithiocarbamate-based vulcanization accelerators include, for example, zinc dibenzyldithiocarbamate (ZnBzDTC), zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldithiocarbamate (ZnEDC), zinc di-n-butyldithiocarbamate (ZnBDC), Zinc N-pentamethylenedithiocarbamate (ZnPDC), Zinc ethylphenyldithiocarbamate (ZnEPDC), Sodium dimethyldithiocarbamate (NaMDC), Sodium diethyldithiocarbamate (NaEDC), Sodium di-n-butyldithiocarbamate (NaBDC), Diethyldithiocarbamine Acid tellurium (TeEDC), copper dimethyldithiocarbamate (CuMDC), iron dimethyldithiocarbamate (FeMDC), and the like.

When a sulfenamide-based vulcanization accelerator is contained, its content is not particularly limited, but it is preferably 0.1 to 3 parts by mass, preferably 0.2 to 2 parts by mass, with respect to 100 parts by mass of the rubber component. Parts by mass are more preferred.

When a guanidine-based vulcanization accelerator is contained, its content is not particularly limited, but it is preferably 0.1 to 3 parts by mass, and 0.2 to 2 parts by mass with respect to 100 parts by mass of the rubber component. is more preferable.

When a dithiocarbamate-based vulcanization accelerator is contained, its content is not particularly limited, but it is preferably 0.1 to 3 parts by mass, preferably 0.2 to 2 parts by mass, based on 100 parts by mass of the rubber component. Parts by mass are more preferred.

As the vulcanization accelerator, among these, it is preferable to use a combination of a dithiocarbamate vulcanization accelerator and a guanidine vulcanization accelerator, and the mixing ratio (guanidine vulcanization accelerator/dithiocarbamate vulcanization accelerator sulfur accelerator) is preferably in a mass ratio of 0.5 to 3.0.

When two or more vulcanization accelerators are used in combination, the total content of vulcanization accelerators is preferably 0.1 to 9 parts by mass, preferably 0.5 to 6 parts by mass, per 100 parts by mass of the rubber component. Parts by mass are more preferred.

The rubber composition according to the present embodiment can be produced by kneading according to a conventional method using a commonly used mixing machine such as a Banbury mixer, kneader, or roll. That is, in the first mixing step, additives other than the vulcanizing agent and the vulcanization accelerator are added and mixed to the rubber component, and then the vulcanizing agent and the vulcanization accelerator are added to the resulting mixture in the final mixing step. can be added and mixed to prepare a rubber composition.

The rubber composition thus obtained can be used for tires, and can be applied to various parts of tires such as treads and sidewalls of pneumatic tires for various uses and sizes, such as large tires for passenger cars, trucks and buses. be able to. The rubber composition is molded into a rubber member having a predetermined shape by, for example, extrusion processing, and after combining with other parts, vulcanization molding is performed at, for example, 140 to 180° C. to produce a pneumatic tire. can do.

The type of the pneumatic tire according to the present embodiment is not particularly limited, and includes various tires such as passenger car tires and heavy-duty tires used for trucks, buses, and the like.

Examples of the present invention are shown below, but the present invention is not limited to these examples.

<Synthesis Example of Hydrogenated Copolymer 1>
2.5 L of cyclohexane, 50 g of tetrahydrofuran (THF), 0.12 g of n-butyllithium, 100 g of styrene, and 400 g of 1,3-butadiene are placed in a heat-resistant reaction vessel purged with nitrogen, and polymerized at a reaction temperature of 50°C. did After the polymerization was completed, 1.7 g of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxylan was added and allowed to react for 1 hour, then hydrogen gas was supplied at a pressure of 0.4 MPa-gauge and stirred for 20 minutes. bottom. Next, the hydrogen gas supply pressure is set to 0.7 MPa-gauge, the reaction temperature is set to 90° C., and a catalyst mainly composed of titanocene dichloride is used to react until the target hydrogenation rate is reached, and the solvent is removed to perform hydrogenation. A copolymer 1 was obtained.

The weight-average molecular weight of the obtained hydrogenated copolymer 1 was measured using "LC-10A" manufactured by Shimadzu Corporation as a measuring device, "PLgel-MIXED-C" manufactured by Polymer Laboratories as a column, and as a detector. Using a differential refractive index detector (RI), using THF as a solvent, measuring temperature of 40 ° C., flow rate of 1.0 mL / min, concentration of 1.0 g / L, injection volume of 40 μL. It was 350,000 in terms of polystyrene. The bound styrene content was 20% by mass, and the hydrogenation rate of the butadiene portion was 90 mol%. The amount of bound styrene was determined from the spectrum intensity ratio between the protons based on the styrene unit and the protons based on the butadiene unit (including the hydrogenated portion) using H ¹ -NMR.

<Examples and Comparative Examples>
Using a Banbury mixer, according to the formulations (parts by mass) shown in Tables 1 and 2 below, first, in the first mixing stage (non-professional kneading process), the components other than the vulcanization accelerator and sulfur are added and mixed (exhaust temperature = 160°C), and then, in the final mixing stage (pro-kneading step), a vulcanization accelerator and sulfur were added and mixed (exhaust temperature = 90°C) to the resulting mixture to prepare a rubber composition.

Details of each component in Tables 1 and 2 are as follows.
・SBR: “HPR350” manufactured by JSR Corporation
Hydrogenated SBR: Hydrogenated copolymer 1 prepared according to the above synthesis example
・ Silica: “Ultrasil VN3” manufactured by Evonik Japan
・ Silane coupling agent: “Si69” manufactured by Evonik Japan Co., Ltd.
・ Carbon black: Tokai Carbon Co., Ltd. “SEAST 3”
・Aroma oil: “Process NC140” manufactured by JXTG Energy Co., Ltd.
・ Zinc oxide: Mitsui Kinzoku Mining Co., Ltd. “Zinc oxide type 2”
・ Anti-aging agent: "Antigen 6C" manufactured by Sumitomo Chemical Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・Wax: "OZOACE0355" manufactured by Nippon Seiro Co., Ltd.
・Vulcanization accelerator 1: Sumitomo Chemical Co., Ltd. “Sokucinol CZ”, sulfenamide-based vulcanization accelerator ・Vulcanization accelerator 2: Ouchi Shinko Kagaku Kogyo Co., Ltd. “Noxera-D”, guanidine-based Vulcanization accelerator / vulcanization accelerator 3: Sanshin Chemical Industry Co., Ltd. "Suncellar ZBE", dithiocarbamate-based vulcanization accelerator / sulfur: Tsurumi Chemical Industry Co., Ltd. "fine powder sulfur"

The obtained rubber composition was evaluated for wear resistance and hardness. The measurement and evaluation methods are as follows, and the evaluation results are shown in Tables 1 and 2.

· Abrasion resistance: In accordance with JIS K6264, using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd., the wear loss was measured under the conditions of a load of 40 N and a slip rate of 30%. is shown as an index with the value of 100.

- Hardness: Measured at 23°C using a type A durometer conforming to JIS K6253.

The results are shown in Tables 1 and 2. From the comparison between Comparative Example 1 and Comparative Examples 2 to 4, it was found that silane When the content of the coupling agent was increased, the hardness increased, but the wear resistance deteriorated.

On the other hand, from the comparison between Comparative Example 5 and Examples 1 to 3, in the formulation mainly composed of the hydrogenated copolymer, when the content of the silane coupling agent was increased without reducing the content of sulfur, the resistance It was possible to increase the hardness while maintaining wearability.

The rubber composition for tires of the present invention can be used in various tires for passenger cars, light trucks and buses.

Claims (1)

A hydrogenated copolymer obtained by hydrogenating an aromatic vinyl-conjugated diene copolymer, having a weight average molecular weight of 300,000 or more as measured by gel permeation chromatography, and a hydrogenation rate of the conjugated diene portion of 80. It contains a rubber component containing 70 to 100% by mass of a hydrogenated copolymer that is mol% or more, silica, a silane coupling agent, and sulfur, and the content of the silane coupling agent is 9 relative to the silica. A rubber composition for tires, which is ~14% by mass.