JP6701671B2 - Rubber composition for tires - Google Patents

Description

  The present invention relates to a rubber composition for tires.

  In recent years, tires are increasingly required to have low heat buildup. Conventionally, it has been known that the low heat buildup property of a tire can be improved by blending silica, but at the same time, there is a tendency that the viscosity rises, the workability deteriorates, and the toughness also deteriorates.

On the other hand, as a conventional method related to a rubber composition for tires, for example, one described in Patent Document 1 has been proposed.
In Patent Document 1, a conjugated diene compound-non-conjugated olefin copolymer (A) having a conjugated diene compound-derived portion content of 40 mol% or more, a conjugated diene-based polymer (B), and ethylene-propylene-diene rubber. A non-conjugated diene compound-non-conjugated olefin copolymer (C) containing a rubber composition is described, wherein the conjugated diene compound-non-conjugated olefin copolymer (A) is It is described that a specific compound containing antimony chloride or antimony pentachloride is used as a polymerization catalyst composition to polymerize a conjugated diene compound and a non-conjugated olefin.

International Publication No. 2012/117715 Pamphlet

  As described above, a rubber composition that can obtain a tire excellent in all of low heat buildup, processability and toughness has not been conventionally proposed.

  An object of the present invention is to provide a rubber composition which is excellent in all of low exothermicity, processability and toughness, and is also excellent in adhesive performance.

  The present inventors have conducted extensive studies to solve the above problems, and in a specific ratio, a rubber composition containing a diene rubber, an antimony oxide compound, carbon black, an organic acid cobalt salt, and a vulcanizing agent, The present invention has been completed by finding that the object of (1) is achieved.

  In addition, in the rubber composition described in Patent Document 1, it is described that antimony trichloride or antimony pentachloride can be used as a catalyst in the production process, but the rubber composition finally obtained by production is described. Does not include antimony trichloride or antimony pentachloride as a catalyst used in the production process.

The present invention is the following (1) to (4).
(1) Carbon black having an antimony oxide compound content of 1 to 50 parts by mass and a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 100 m ² /g with respect to 100 parts by mass of a diene rubber containing 90% by mass or more of isoprene. A rubber composition for a tire, which contains 40 to 80 parts by mass, 0.01 to 0.30 parts by mass of an organic acid cobalt salt as a cobalt amount, and 4.50 to 8.50 parts by mass of a vulcanizing agent.
(2) The rubber composition for a tire according to (1) above, wherein the antimony oxide compound is fine particles having an average particle diameter of 20 to 60 nm.
(3) For the tire according to (1) or (2), further containing silica, and a sulfur-containing silane coupling agent in an amount of 3 to 20 mass% with respect to the total amount of the silica and the antimony oxide compound. Rubber composition.
(4) A pneumatic tire using the rubber composition for a tire according to any one of (1) to (3) above in a steel cord compound.

  According to the present invention, it is possible to provide a rubber composition which is excellent in all of low exothermicity, processability and toughness, and is also excellent in adhesiveness.

1 is a schematic partial cross-sectional view of a tire showing an example of an embodiment of a pneumatic tire of the present invention.

The present invention will be described.
The present invention relates to a carbon black having an antimony oxide compound content of 1 to 50 parts by mass and a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 100 m ² /g with respect to 100 parts by mass of a diene rubber containing 90% by mass or more of isoprene. Is 40 to 80 parts by mass, an organic acid cobalt salt is 0.01 to 0.30 parts by mass in terms of cobalt amount, and a vulcanizing agent is 4.50 to 8.50 parts by mass.
Hereinafter, such a rubber composition for a tire is also referred to as a “composition of the present invention”.

<Diene rubber>
The diene rubber contained in the composition of the present invention contains isoprene in an amount of 90% by mass or more, preferably 92% by mass or more, and more preferably 95% by mass or more.
Isoprene includes natural rubber, and isoprene is preferably natural rubber. The reason is that the fracture characteristics are high and the toughness is excellent.

  The diene rubber may contain components other than isoprene. The component other than isoprene is not particularly limited as long as it is a diene rubber having a double bond in the main chain. Specific examples thereof include styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), ethylene-propylene-diene copolymer rubber (EPDM), styrene. -Isoprene rubber, isoprene-butadiene rubber, nitrile rubber, hydrogenated nitrile rubber and the like can be mentioned.

  It is preferable to use butadiene rubber (BR) as the diene rubber. The reason is that it has excellent fatigue resistance.

<Carbon black>
Carbon black-containing compositions of the present invention, the nitrogen adsorption specific surface area (N ₂ SA) is 30 to 100 m ² / g, is preferably 40~95m ² / g, in 50~90m ² / g More preferably.
The nitrogen adsorption specific surface area (N ₂ SA) is a value determined according to JIS K6217-2.

Carbon black-containing compositions of the present invention is preferably a DBP absorption amount is 50~80cm ³ / 100g, and more preferably 60~75cm ³ / 100g.
In addition, it is the value calculated based on JIS K6217-4 oil absorption amount A method.

The larger the difference between the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black and the DBP absorption amount, the better, and the difference between the two is preferably in the range of 150 to 200.

  In the present invention, the content of the carbon black is 40 to 80 parts by mass, preferably 45 to 75 parts by mass, and more preferably 50 to 70 parts by mass, relative to 100 parts by mass of the diene rubber. Is more preferable. The reason is that the fracture characteristics are high and the toughness is excellent.

<Antimony oxide compound>
The antimony oxide compound contained in the composition of the present invention is not particularly limited and is preferably fine particles having an average particle diameter of 20 to 60 nm, more preferably 25 to 50 nm.

  The average particle size was determined by taking a picture of the antimony oxide compound with a transmission electron microscope (TEM) at a magnification of 5000 times, selecting 500 particles arbitrarily from the obtained pictures, and using a vernier caliper for each projected area circle. The diameter is measured to obtain an integrated particle size distribution (volume basis), and an average particle diameter (median diameter) is calculated from the particle size distribution to obtain a value.

Examples of the antimony oxide compound include antimony tin oxide, antimony zinc oxide, and antimony titanium oxide.
The antimony oxide compound contains antimony oxide.
The antimony oxide compound contained in the composition of the present invention is preferably an antimony oxide-tin system or an antimony oxide-indium system. Since the rubber can be made conductive by blending a tin or indium compound, the silica blended rubber can be prevented from being charged.

  In the present invention, the content of the antimony oxide compound is 1 to 50 parts by mass, and more preferably 2 to 40 parts by mass with respect to 100 parts by mass of the diene rubber. The reason is that the fracture characteristics are high and the toughness is excellent.

<Organic acid cobalt salt>
The rubber composition of the present invention contains a cobalt salt of an organic acid. The organic acid cobalt salt increases the adhesion to the steel cord.
The content of the organic acid cobalt salt is preferably 0.01 to 0.30 parts by mass, more preferably 0.15 to 0.25 parts by mass, relative to 100 parts by weight of the diene rubber, as the amount of cobalt. preferable. If the content of cobalt is too small, it is difficult to sufficiently increase the initial adhesion to the steel cord. On the other hand, if the amount of cobalt is too large, the adhesion to the steel cord is rather reduced.

  Note that the organic acid cobalt salt contains a complex.

  In the present invention, examples of the organic acid cobalt salt include cobalt naphthenate, cobalt neodecanoate, cobalt stearate, cobalt rosinate, cobalt versatic acid, cobalt tall oilate, cobalt neodecanoate borate, and cobalt acetylacetonate. can do. Further, among these organic acid cobalt salts, organic acid cobalt salts containing boron are preferable, and for example, a complex salt in which a part of the organic acid is replaced with boric acid or the like is preferable. The organic acid cobalt salt containing boron is preferably cobalt orthoborate having a cobalt content of 20 to 23 mass %. Examples of the organic acid cobalt salt containing boron include Manobond C22.5 and Manobond 680C manufactured by Rhodia, CoMend A and CoMend B manufactured by Jhepherd, and YYNBC-II manufactured by Dainippon Ink and Chemicals.

<Vulcanizing agent>
The composition of the present invention comprises a vulcanizing agent. As the vulcanizing agent, those that can be used in conventionally known rubber compositions for tires can be used. The vulcanizing agent is preferably sulfur.
The content of the vulcanizing agent in the composition of the present invention is 4.50 to 8.50 parts by mass, and more preferably 5.0 to 8.0 parts by mass with respect to 100 parts by mass of the diene rubber. preferable. The reason is that the fracture characteristics are high and the toughness is excellent.

<Silica>
The composition of the present invention preferably contains silica.
When the composition of the present invention contains silica, the silica is not particularly limited, and any conventionally known silica compounded in a rubber composition for use in a tire or the like can be used.

  Specific examples of the silica include fumed silica, calcined silica, precipitated silica, pulverized silica, fused silica, colloidal silica, and the like. These may be used alone or in combination of two or more. You may use together.

  In the present invention, the content of the silica is preferably 2 to 50 parts by mass, more preferably 5 to 40 parts by mass, and 8 to 30 parts by mass with respect to 100 parts by mass of the diene rubber. Is more preferable. The reason is that it has high fracture properties, excellent toughness, and excellent adhesive performance.

<Sulfur-containing silane coupling agent>
The composition of the present invention preferably contains a sulfur-containing silane coupling agent.
The sulfur-containing silane coupling agent is not particularly limited, and any conventionally known sulfur-containing silane coupling agent compounded in the rubber composition for use in tires and the like can be used.

  Specific examples of the sulfur-containing silane coupling agent include 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide and triethoxysilylpropyl. -Methacrylate-monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]tetrasulfide, bis-[3-(trimethoxysilyl)-propyl ] Tetrasulfide, bis-[3-(triethoxysilyl)-propyl]disulfide, 3-mercaptopropyl-trimethoxysilane, 3-mercaptopropyl-triethoxysilane and the like can be mentioned, and these may be used alone. Of course, two or more kinds may be used in combination.

  In the present invention, the content of the sulfur-containing silane coupling agent is a ratio (sulfur-containing silane cup content to the total amount of the silica and the antimony oxide compound (the content of the antimony oxide compound alone when silica is not included)). The content of the ring agent/(content of silica+content of antimony oxide compound)×100) is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, and 7 to 10% by mass. % Is more preferable. When the blending amount of the sulfur-containing silane coupling agent is within the above range when the ratio to the total amount of the silica and the antimony oxide compound (the content of only the antimony oxide compound when silica is not included) is in the above range, This is because it is possible to obtain a rubber composition that is superior in all of exothermicity, processability, and toughness, and is also superior in adhesive performance.

<Other ingredients>
In the composition of the present invention, in addition to the above components, an aromatic terpene resin, a filler other than silica and carbon black, a silane coupling agent other than the sulfur-containing silane coupling agent, a vulcanization or crosslinking accelerator. Various additives generally used in tire rubber compositions, such as zinc oxide, softening agents (oils), anti-aging agents, and plasticizers can be added. The amounts of these additives to be compounded can be conventional general amounts, so long as the object of the present invention is not impaired.

For example, the content of the vulcanization accelerator or the crosslinking accelerator is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the diene rubber in the primary accelerator alone or in the blend with the secondary accelerator. More preferably, it is from 0 to 5 parts by mass.
The content of zinc oxide is preferably 0.2 to 10.0 parts by mass and more preferably 0.4 to 5.0 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the softening agent (oil) is preferably 0.1 to 20 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the antioxidant is preferably 0.1 to 5.0 parts by mass, and more preferably 0.2 to 4.0 parts by mass with respect to 100 parts by mass of the diene rubber.

[Production method]
The rubber composition of the present invention can be produced by mixing and kneading the above components.
Of the above components, components other than the vulcanization (crosslinking) agent and the vulcanization (crosslinking) accelerator are mixed and kneaded to prepare a masterbatch, and the masterbatch is subjected to the vulcanization (crosslinking) agent and the vulcanization (crosslinking) crosslinking. ) It is preferable that a rubber composition is manufactured by mixing an accelerator and kneading with an open roll or the like. In this way, a masterbatch composed of components other than the vulcanization (crosslinking) agent and the vulcanization (crosslinking) accelerator is prepared, and the vulcanization (crosslinking) agent and the vulcanization (crosslinking) accelerator are mixed with the masterbatch. When kneading, the kneading time after mixing the vulcanization (crosslinking) agent and the vulcanization (crosslinking) accelerator can be shortened, resulting in uneven vulcanization (crosslinking). It is possible to prevent deterioration of the physical properties of the composition and facilitate control of vulcanization (crosslinking).

[Pneumatic tire]
The pneumatic tire of the present invention is a pneumatic tire manufactured using the composition of the present invention described above. Above all, a pneumatic tire using a steel cord coated with the composition of the present invention is preferable.
FIG. 1 shows a schematic partial cross-sectional view of a tire showing an example of an embodiment of the pneumatic tire of the present invention, but the pneumatic tire of the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, reference numeral 1 represents a bead portion, reference numeral 2 represents a sidewall portion, and reference numeral 3 represents a tire tread portion.
A carcass layer 4 in which a fiber cord is embedded is mounted between the pair of left and right bead portions 1, and the end portion of the carcass layer 4 extends from the tire inner side to the outer side around the bead core 5 and the bead filler 6. It is folded back and rolled up.
Further, in the tire tread 3, the belt layer 7 is arranged outside the carcass layer 4 over the entire circumference of the tire.
Further, in the bead portion 1, a rim cushion 8 is arranged at a portion in contact with the rim.

  The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. Further, as the gas to be filled in the tire, in addition to normal air or air whose oxygen partial pressure is adjusted, an inert gas such as nitrogen, argon or helium can be used.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples.

[Production of rubber composition]
<Standard example, Examples 1 to 4, Comparative examples 1 to 3>
As shown in the standard example column, the example column, and the comparative example column of Table 1, the rubber compositions according to the standard example, Examples 1 to 4, and Comparative Examples 1 to 3 are each component shown in Table 1. Was blended in the blending amount shown in Table 1 to produce.
Specifically, first, of the components shown in Table 1 below, excluding sulfur and the vulcanization accelerator, were mixed for 5 minutes by using a 1.7-liter closed Banbury mixer to reach 150±5° C. When released, it was discharged and cooled to room temperature to obtain a masterbatch. Further, sulfur and a vulcanization accelerator were mixed with the obtained masterbatch using the above Banbury mixer to obtain a rubber composition.

[Preparation of vulcanized rubber sheet for evaluation]
The produced rubber composition (unvulcanized) was press-vulcanized in a mold (15 cm×15 cm×0.2 cm) at 160° C. for 20 minutes to prepare a vulcanized rubber sheet.

[Test evaluation method]
<Viscosity>
The Mooney viscosity (ML ₁₊₄ ) of each rubber composition was measured by a Mooney viscometer according to JIS K6300 using an L-shaped rotor, preheating time 1 minute, rotor rotation time 4 minutes, temperature 100° C., 2 rpm. It was measured under the conditions.
The results are shown in Table 1. The obtained results were expressed as indices by calculating the reciprocal of each Mooney viscosity and setting the standard example as 100. The smaller the value, the lower the viscosity and the better the processability.

<Toughness>
Regarding the vulcanized rubber sheet produced as described above, a JIS No. 3 dumbbell-shaped test piece (thickness: 2 mm) was punched out in accordance with JIS K6251:2010, and a 100% modulus (at a temperature of 100° C. and a pulling speed of 500 mm/min. M100: stress at 100% deformation), fracture strength (E _B: stress at break) were measured. Then, to calculate the M100 ^0.75 × E _B, and the toughness index it.
The results are shown in Table 1. The measurement result was expressed as an index with the value of the standard example being 100. The larger the value, the better the toughness.

<Low heat generation>
According to JIS K6394:2007, using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.), tan δ (60° C.) under the conditions of 10%±2% of elongation deformation strain rate, frequency 20 Hz, and temperature 60° C. It was measured.
The results are shown in Table 1. The result was shown as an index with the standard example being 100. The lower this value, the better the low heat buildup.

<Adhesion performance>
The test was conducted according to ASTM D-2229. Brass-plated steel cords arranged in parallel at 12.7 mm intervals were covered with the above rubber composition, embedded at an embedding length of 12.7 mm, and vulcanized and adhered under vulcanization conditions of 170° C.×10 minutes to obtain an adhesive sample. It was made. The steel cord was pulled out from this adhesive sample, and evaluated by the pulling force and the amount of rubber attached (%) covering the surface thereof.
The results are shown in Table 1. The result was shown as an index with the standard example being 100. The larger this value, the better the adhesiveness.

[Specific description of each component in the table]
Details of each component shown in the table are as follows.
・NR: Natural rubber TSR20
・Carbon black 1: ISAF Seast 6 manufactured by Tokai Carbon Co., Ltd., N ₂ SA=119 m ² /g
・Carbon black 2: HAF Seast 3 manufactured by Tokai Carbon Co., Ltd., N ₂ SA=79 m ² /g
Silica: Zeosil ^(R) 1165MP (CTAB adsorption specific surface area: 159 m ² /g, manufactured by Rhodia)
Antimony tin oxide 1: Nano-D CEP manufactured by Nanotechnology, Inc. average particle diameter=30-40 nm
Antimony tin oxide 2: NYACOL SN902SD manufactured by Nyacol Nano Technology Co., Ltd. average particle size=7 μm
・Zinc oxide: 3 types of zinc oxide manufactured by Shodo Kagaku Kogyo Co., Ltd. ・Stearic acid: manufactured by NOF CORPORATION bead stearic acid ・Anti-aging agent: SANTOFLEX 6PPD manufactured by FLEXSYS Co., Ltd.
-Organic acid cobalt salt: manufactured by Shepherd Chemical Co., Manobond, cobalt content = 22.5% by mass
・Process oil: Showa Shell Sekiyu Co., Ltd.
・Sulfur: Fine powdered sulfur containing Kinka In oil manufactured by Tsurumi Chemical Industry Co. (sulfur content 95.24% by weight)
・Vulcanization accelerator: DZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[Explanation of test results]
<Examples 1 to 4>
In Examples 1 to 4, the viscosity, toughness, exothermicity, and adhesive performance could be improved.

<Comparative Example 1>
In this embodiment, N ₂ SA of carbon black is out of the range of 30 to 100 m ² /g. In this case, the viscosity and low heat buildup deteriorated.

<Comparative example 2>
In this embodiment, the organic acid cobalt salt is not included. In this case, the adhesive performance and toughness deteriorated.

<Comparative example 3>
This is an embodiment containing a large amount of antimony oxide compound. In this case, the toughness deteriorated.

1 Bead Part 2 Sidewall Part 3 Tire Tread Part 4 Carcass Layer 5 Bead Core 6 Bead Filler 7 Belt Layer 8 Rim Cushion

Claims (3)

With respect to 100 parts by mass of the diene rubber containing 90% by mass or more of isoprene, 1 to 50 parts by mass of an antimony oxide compound, which is a fine particle having an average particle size of 20 to 60 nm , and a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 100 m. Rubber for tires containing 40 to 80 parts by mass of carbon black of ² /g, 0.01 to 0.30 parts by mass of cobalt salt of organic acid, and 4.50 to 8.50 parts by mass of vulcanizing agent. Composition. The tire rubber composition according to claim 1 , further comprising silica, and a sulfur-containing silane coupling agent in an amount of 3 to 20 mass% with respect to a total amount of the silica and the antimony oxide compound. A pneumatic tire using the rubber composition for a tire according to claim 1 or 2 in a steel cord compound.

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