JP2016040347A - Tire rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire rubber composition excellent in both wear resistance and breaking elongation, and a pneumatic tire prepared therewith.SOLUTION: A tire rubber composition comprises a diene rubber, and cobalt or a cobalt compound. The diene rubber comprises a butadiene rubber of 5-70 mass%. A content of the cobalt or the cobalt compound is 0.01-5 pts. mass, as an amount of cobalt, relative to the diene rubber of 100 pts. mass.SELECTED DRAWING: None

Description

  The present invention relates to a tire rubber composition and a pneumatic tire.

  In pneumatic tires mounted on passenger cars, trucks, buses, construction vehicles, etc., wear resistance has been positioned as an important characteristic in recent years from the viewpoints of safety, economic efficiency and maintainability when used by customers.

For example, Patent Document 1 discloses that “(A) linearity index is 110 to 140 and Newton's fluidity index (n) is 2. for the purpose of improving the dispersibility of fillers in polybutadiene rubber and improving wear resistance. 2 to 3.0 (where the linearity index is the solution viscosity (centipoise) of a 5% by weight toluene solution of the polymer at 30 ° C., and the Newtonian flow index is expressed by the formula: γ = K · τn (where γ = K Τn (γ is a shear rate (unit: 1 / sec), τ is a shear stress (Pa), and K is a constant of 1 / η (η: polymer viscosity (Pa · sec))) 100 parts by weight of diene rubber containing 10 parts by weight or more of polybutadiene rubber, (B) (i) carbon black having a CTAB of 70 m ² / g or more and / or (ii) silica having a BET specific surface area of 100 m ² / g or more (B) i) and (a total amount of the rubber composition for a tire tread comprising 30 to 150 parts by weight of ii) "is described ([Claim 1] [0004]).

JP 2009-057398 A

  The inventors of the present invention have studied a conventionally known rubber composition for tires containing butadiene rubber described in Patent Document 1 and the like. However, although the wear resistance is improved by adding butadiene rubber, the butadiene rubber is improved. It has been clarified that the elongation at break may be reduced depending on the blending amount, and as a result, defects such as cracks may occur in the manufactured tire.

  Then, this invention makes it a subject to provide the rubber composition for tires excellent in both abrasion resistance and breaking elongation, and a pneumatic tire using the same.

As a result of diligent studies to solve the above problems, the present inventors have found that a rubber composition in which a specific amount of cobalt or a cobalt compound is blended with a diene rubber containing a predetermined amount of butadiene rubber has wear resistance and fracture. The inventors found that all the elongations were good and completed the present invention.
That is, the present inventor has found that the above problem can be solved by the following configuration.

[1] containing a diene rubber and cobalt or a cobalt compound,
The diene rubber contains 5 to 70% by mass of butadiene rubber,
The rubber composition for tires whose content of the said cobalt or the said cobalt compound is 0.01-5 mass parts as a cobalt amount with respect to 100 mass parts of said diene rubbers.
[2] The rubber composition for tires according to [1], containing the cobalt compound, wherein the cobalt compound is a cobalt salt or a cobalt complex.
[3] The rubber composition for tires according to [2], containing the cobalt salt, wherein the cobalt salt is an organic acid cobalt salt.
[4] A pneumatic tire using the rubber composition according to any one of [1] to [3] as at least one constituent member selected from the group consisting of a tread and a sidewall.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for tires excellent in both abrasion resistance and breaking elongation, and a pneumatic tire using the same can be provided.

It is a typical fragmentary sectional view of the tire showing an example of the embodiment of the pneumatic tire of the present invention.

[Rubber composition for tire]
The rubber composition for tires of the present invention (hereinafter also simply referred to as “the rubber composition of the present invention”) contains a diene rubber and cobalt or a cobalt compound. A rubber composition for tires containing 70% by mass and having a cobalt content of 0.01 to 5 parts by mass with respect to 100 parts by mass of the diene rubber.

In the present invention, excellent wear resistance and elongation at break can be achieved by blending a specific amount of cobalt or a cobalt compound with a diene rubber containing a predetermined amount of butadiene rubber.
This is based on a new finding that when a cobalt or cobalt compound is added to a rubber composition containing a predetermined amount of butadiene rubber, deterioration of other diene rubbers can be suppressed. That is, even if the blending amount of butadiene rubber is relatively reduced as compared with a system in which cobalt or a cobalt compound is not blended, the effect of improving the wear resistance can be expressed to the same level or more.
Below, each component which the rubber composition of this invention contains is demonstrated in detail.

[Diene rubber]
The diene rubber contained in the rubber composition of the present invention is not particularly limited as long as it contains at least 5-70% by mass of butadiene rubber.
Here, the butadiene rubber is an alkyl group, allyl group, amino group, isocyanate group, hydroxyl group, thiol group, vinyl group, epoxy group, thiirane group, carboxy group, carbonyl group-containing group, amide group, ester group, imide. At least one functional group selected from a group, a nitrile group, a thiocyan group, an alkoxy group, a silyl group, an alkoxysilyl group, a nitro group, etc., has modified (modified) the side chain, one end or both ends It may be a derivative.

The weight average molecular weight of the butadiene rubber is preferably 50,000 to 1,000,000, and more preferably 200,000 to 800,000. By setting the weight average molecular weight in such a range, the wear resistance can be further improved.
Here, the weight average molecular weight (Mw) of butadiene rubber shall be measured by standard polystyrene conversion by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

  Furthermore, the butadiene rubber is preferably contained in the diene rubber in an amount of 5 to 50% by mass and more preferably in the range of 5 to 40% by mass because the wear resistance is improved and the balance with the elongation at break is improved. More preferably.

In the present invention, the diene rubber other than the butadiene rubber is not particularly limited as long as it has a double bond in the main chain. Specific examples thereof include natural rubber (NR), isoprene rubber (IR), Acrylonitrile-butadiene rubber (NBR), aromatic vinyl-conjugated diene copolymer rubber [eg, styrene-butadiene rubber (SBR), styrene-isoprene rubber, styrene-butadiene-isoprene rubber (SBIR)], styrene-isoprene rubber (SIR) ), Styrene-isoprene-butadiene rubber (SIBR), and the like. These may be used alone or in combination of two or more.
These diene rubbers are alkyl groups, allyl groups, amino groups, isocyanate groups, hydroxyl groups, thiol groups, vinyl groups, epoxy groups, thiirane groups, carboxy groups, carbonyl group-containing groups, amide groups, ester groups, At least one functional group selected from imide group, nitrile group, thiocyan group, alkoxy group, silyl group, alkoxysilyl group, nitro group, etc., the side chain, one end or both ends are modified (modified) Derivatives may also be used.
Of these, NR and SBR are preferably used from the viewpoint of better wear resistance and excellent workability.

[Cobalt or cobalt compound]
As described above, the rubber composition of the present invention contains 0.01 to 5 parts by mass of cobalt or a cobalt compound as a cobalt amount with respect to 100 parts by mass of the diene rubber.
Here, “cobalt” means metallic cobalt, and “cobalt compound” means a compound containing metallic cobalt.

  In the present invention, from the viewpoint of affinity with the diene rubber, it is preferable to use a cobalt compound among cobalt and a cobalt compound. Specifically, it is more preferable to use a cobalt salt or a cobalt complex described later. .

<Cobalt salt>
Specific examples of the cobalt salt include cobalt halides such as cobalt chloride and cobalt bromide; inorganic cobalt salts such as cobalt hydroxide, cobalt nitrate and cobalt sulfate; cobalt acetate, cobalt octylate and cobalt naphthenate. , Cobalt malonate, cobalt neodecanoate, cobalt stearate, cobalt propionate, cobalt benzoate, cobalt p-hydroxybenzoate, fatty acid cobalt-boron compound [e.g. Etc.), and organic acid cobalt salts such as cobalt rosinate, cobalt versatate and cobalt tall oil.
Among these, the organic acid cobalt salt is preferable because the balance between wear resistance and elongation at break improves.

<Cobalt complex>
Specific examples of the cobalt complex include, for example, cobalt (II) bisacetylacetonate; cobalt (III) trisacetylacetonate; acetoacetic acid ethyl ester cobalt; cobalt halide organic base complex (for example, triarylphosphine). A fin complex, a trialkylphosphine complex, a pyridine complex, a picoline complex, an ethyl alcohol complex, and the like).

  In this invention, content of the said cobalt or the said cobalt compound is 0.01-5 mass parts as a cobalt amount with respect to 100 mass parts of said diene rubbers, and is 0.01-1 mass part. Is preferable, and it is more preferable that it is 0.01-0.5 mass part.

〔Carbon black〕
The rubber composition of the present invention preferably contains carbon black.
Specific examples of the carbon black include furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF. These may be used alone or in combination of two or more. May be.
Further, the carbon black, from the viewpoint of workability and the like at the time of mixing of the rubber composition is preferably a nitrogen adsorption specific surface area (N ₂ SA) is 10 to 300 m ² / g, with 20 to 200 m ² / g More preferably.
Here, N ₂ SA is a value obtained by measuring the amount of nitrogen adsorbed on the carbon black surface in accordance with JIS K 6217-2: 2001 “Part 2: Determination of specific surface area—nitrogen adsorption method—single point method”. .

  When the carbon black is contained, the content is preferably 1 to 100 parts by mass and more preferably 5 to 80 parts by mass with respect to 100 parts by mass of the diene rubber.

[Other ingredients]
In addition to the components described above, the rubber composition of the present invention includes fillers such as silica and calcium carbonate; silane coupling agents; vulcanizing agents such as sulfur; sulfenamide-based, guanidine-based, thiazole-based, thiourea-based, and thiuram-based materials. Vulcanization accelerators such as zinc oxide and stearic acid; waxes; aroma oils; paraphenylenediamines (for example, N, N'-di-2-naphthyl-p-phenylenediamine, N- 1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine, etc.), ketone-amine condensates (eg, 2,2,4-trimethyl-1,2-dihydroquinoline, etc.) Various plastic additives, chemical foaming agents such as hollow polymers, and the like, and various other additives generally used in rubber compositions for tires can be blended.

[Method for producing rubber composition]
The method for producing the rubber composition of the present invention is not particularly limited, and examples thereof include a method of kneading the above-described components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). It is done.
The rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[Pneumatic tire]
The pneumatic tire of the present invention (hereinafter also simply referred to as “the tire of the present invention”) is a pneumatic tire using the above-described rubber composition of the present invention as a constituent (rubber) member.
Here, the constituent member using the rubber composition of the present invention is a tread portion and / or a sidewall portion, and is preferably a tread portion.
FIG. 1 shows a schematic partial cross-sectional view of a tire representing an example of an embodiment of the tire of the present invention, but the tire of the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, the code | symbol 1 represents a bead part, the code | symbol 2 represents a sidewall part, and the code | symbol 3 represents the tread part comprised from the rubber composition of this invention.
Further, a carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1, and the end of the carcass layer 4 extends from the inside of the tire to the outside around the bead core 5 and the bead filler 6. Wrapped and rolled up.
In the tire tread 3, a belt layer 7 is disposed over the circumference of the tire on the outside of the carcass layer 4.
Moreover, in the bead part 1, the rim cushion 8 is arrange | positioned in the part which touches a rim | limb.
Further, an inner liner 9 is disposed on the inner surface of the tire in order to prevent air filled in the tire from leaking outside the tire.

For example, when the rubber composition of the present invention is used in a tire tread portion, the tire of the present invention can achieve both excellent vulcanization properties and low heat generation.
In addition, the tire of the present invention is vulcanized or cured at a temperature corresponding to, for example, the type of diene rubber, vulcanization or crosslinking agent, vulcanization or crosslinking accelerator used in the rubber composition of the present invention, and the blending ratio thereof. It can manufacture by bridge | crosslinking and forming a tire tread part.

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

<Examples 1-3 and Comparative Examples 1-6>
The components shown in Tables 1 and 2 below were blended in the proportions (parts by mass) shown in Tables 1 and 2 below.
Specifically, first, the components shown in Tables 1 and 2 below, excluding sulfur and the vulcanization accelerator, were kneaded for 5 minutes with a 1.7 liter closed mixer and reached 135 ° C. Occasionally discharged and cooled at room temperature to obtain a masterbatch.
Next, sulfur and a vulcanization accelerator were kneaded with the obtained masterbatch with an open roll to prepare a rubber composition.
Next, the obtained rubber composition was vulcanized at 148 ° C. for 30 minutes in a lamborn abrasion mold (disk shape having a diameter of 63.5 mm and a thickness of 5 mm) to produce a vulcanized rubber sheet.

<Elongation at break (E _B ): (Indicator of elongation at break)>
A JIS No. 3 dumbbell-shaped test piece was punched out of the vulcanized rubber sheet thus prepared, and a tensile test at a tensile speed of 500 mm / min was conducted in accordance with JIS K6251: 2010, and the elongation at break (E _B ) was room temperature (23 ° C.). Measured with
The measurement results are represented by an index with the value of Comparative Example 1 as 100 for the following Table 1, and are represented by an index with the value of Comparative Example 4 as 100 for the following Table 2, respectively. Shown in the table. It means that it is excellent in elongation at break, so that this index | exponent is large.

<Abrasion resistance>
About the produced vulcanized rubber sheet, using an Lambourn abrasion tester (made by Iwamoto Seisakusho Co., Ltd.), the applied force is 1.5 kg / cm ³ (= 15 N) and the slip rate is 50% in accordance with JIS K 6264-2: 2005. The wear test was performed for 10 minutes at a test temperature of room temperature, and the wear mass was measured.
As shown in the following formula (A) for the following Table 1, the test results are represented by an index (index) based on the measured value of Comparative Example 1, and as shown in the following Formula (B) for the following Table 2. Are represented by indices based on the measured values of Comparative Example 4, and are shown in Tables 1 and 2 below. The larger this index (index), the smaller the amount of wear and the better the wear resistance.
Index = (Abrasion mass / measured value of test piece of Comparative Example 1) × 100 (A)
Index = (Abrasion mass / measured value of test piece of Comparative Example 4) × 100 (B)

The components shown in Tables 1 and 2 are as follows.
・ Natural rubber: RSS # 3
-Butadiene rubber: NIPOL BR 1220 (manufactured by Nippon Zeon)
・ Carbon black: Show Black N234 (made by Showa Cabot)
・ Zinc oxide: Zinc Hana 3 (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Bead stearic acid (manufactured by NOF Corporation)
-Anti-aging agent 1: Amine-based anti-aging agent (Santflex 6PPD, manufactured by Flexsys)
-Anti-aging agent 2: Amine-ketone type anti-aging agent (NOCRACK 224, Ouchi Shinsei Chemical Co., Ltd.)
・ Wax: Sunnock (Ouchi Shinsei Chemical Co., Ltd.)
・ Cobalt naphthenate: 10% by mass of cobalt (manufactured by DIC)
・ Cobalt hydroxide: Cobalt amount 62.5% by mass (Wako Pure Chemical Industries, Ltd.)
・ Sulfur: Oil-treated sulfur (manufactured by Karuizawa Refinery)
・ Vulcanization accelerator: Noxeller NS-P (manufactured by Ouchi Shinsei Chemical Co., Ltd.)

From the results shown in Table 1, it can be seen that the rubber compositions of Comparative Examples 1 to 3 prepared without compounding butadiene rubber have no change in wear resistance and elongation at break regardless of the presence or absence of a cobalt compound. It was.
In addition, from the results shown in Table 2, the rubber compositions of Comparative Examples 4 to 6 prepared by adding butadiene rubber and not by adding a cobalt compound have improved wear resistance as the amount of butadiene rubber increases. However, it was also found that the elongation at break was inferior with the increase in the amount of butadiene rubber.
On the other hand, the rubber compositions of Examples 1 to 3 prepared by blending a cobalt compound together with butadiene rubber have better wear resistance than Comparative Example 4, and there is little decrease in elongation at break and good breaking. It was found that the elongation can be maintained. In particular, from the comparison of Examples 1 to 3, it was found that when an organic acid cobalt salt was used, there was no decrease in elongation at break and excellent balance between wear resistance and elongation at break.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion 9 Inner liner

Claims (4)

Containing a diene rubber and cobalt or a cobalt compound;
The diene rubber contains 5 to 70% by mass of butadiene rubber,
The rubber composition for tires whose content of the said cobalt or the said cobalt compound is 0.01-5 mass parts as a cobalt amount with respect to 100 mass parts of said diene rubbers. Containing the cobalt compound,
The tire rubber composition according to claim 1, wherein the cobalt compound is a cobalt salt or a cobalt complex. Containing the cobalt salt,
The tire rubber composition according to claim 2, wherein the cobalt salt is an organic acid cobalt salt.   The pneumatic tire which used the rubber composition in any one of Claims 1-3 for the at least 1 component selected from the group which consists of a tread and a sidewall.