JP2017082087A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition capable of providing a tire excellent in wear performance and excellent in processability and storage stability at the same time.SOLUTION: There is provided a rubber composition containing 100 pts.mass of a diene rubber having average glass transition temperature of -80 to -20°C, 30 to 180 pts.mass of silica and 1 to 50 pts.mass of a cerium oxide and further a sulfur-containing silane coupling agent of 3 to 20 mass% in a ratio to the total amount of the silica and the cerium oxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rubber composition for tires.

In recent years, a labeling (display method) system has been implemented for pneumatic tires, and it is required to achieve both wetness (braking and driving performance on a wet road surface) and low rolling resistance at a higher level.
Conventionally, it is known that the low rolling resistance and wettability are improved by changing the filler blended in the rubber material constituting the tread portion of the tire from carbon black to silica. However, the silica compounded rubber tended to deteriorate the wear performance.
Moreover, although the method of improving the dispersibility of a silica by mix | blending the silane coupling agent which has a mercapto group with a silica is proposed, processability and storage stability were inadequate.

On the other hand, as a conventional method relating to a tire rubber composition, for example, those described in Patent Documents 1 and 2 have been proposed.
Patent Document 1 discloses that a conjugated diene compound-nonconjugated olefin copolymer (A) having a conjugated diene compound-derived content of 40 mol% or more, a conjugated diene polymer (B), and an ethylene-propylene-diene rubber. And a non-conjugated diene compound-nonconjugated olefin copolymer (C) containing a rubber composition, wherein the conjugated diene compound-nonconjugated olefin copolymer (A) is cerium. It is described that a conjugated diene compound and a non-conjugated olefin are polymerized by using a specific compound containing as a polymerization catalyst composition.

  In Patent Document 2, pMC (percent Modern Carbon) obtained by polymerizing monomer components derived from biomass and measured according to ASTM D6866-10 is 1% or more, and the glass transition temperature (Tg) is −120 to −80. A rubber composition for tires containing a biomass-derived rubber at a temperature of C is described, and it is described that a monomer component derived from biomass can be obtained using cerium oxide as a catalyst.

International Publication No. 2012/117715 Pamphlet JP 2014-231605 A

  An object of the present invention is to provide a rubber composition capable of obtaining a tire having excellent wear performance and simultaneously excellent workability and storage stability.

  The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and have a specific ratio and a diene rubber having a specific glass transition temperature, silica, cerium oxide, and a rubber containing a specific sulfur-containing silane coupling agent. The present inventors have found that the composition achieves the above object and completed the present invention.

  In addition, in the rubber composition described in Patent Documents 1 and 2, it is described that cerium or cerium oxide can be used as a catalyst in the production process. The catalyst used in the production process does not include cerium or cerium oxide.

The present invention includes the following (i) to (iv).
(I) For 100 parts by mass of the diene rubber having an average glass transition temperature of −80 to −20 ° C., 30 to 180 parts by mass of silica and 1 to 50 parts by mass of cerium oxide are contained. The rubber composition for tires which contains the sulfur containing silane coupling agent which has an average composition formula represented by 3-20 mass% in the ratio with respect to the total amount of the said silica and the said cerium oxide.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} ... Formula (1)
(In formula (1), A represents a divalent organic group containing a sulfide group, B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms, C represents a hydrolyzable group, and D represents R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, a to e are 0 ≦ a <1, 0 <b <1, 0 <c <3 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4.
(Ii) The tire rubber composition as described in (i) above, wherein the cerium oxide is fine particles having an average particle diameter of 20 to 60 nm.
(Iii) The silica has a nitrogen adsorption specific surface area (N ₂ SA) of 194 to 225 m ² / g, a CTAB specific surface area (CTAB) of 180 to 210 m ² / g, a DBP absorption of 190 ml / 100 g or more, and the N ₂ The ratio of SA to CTAB (N ₂ SA / CTAB) is 0.9 to 1.4, and the silica content is 60 to 150 parts by mass with respect to 100 parts by mass of the diene rubber. The tire rubber composition according to (i) or (ii) above, (iv) A pneumatic tire using the rubber composition according to any one of (i) to (iii) as a tire tread .

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition which can obtain the tire which is excellent in abrasion performance, and is excellent also in workability and storage stability can be provided.

It is a partial section schematic diagram of the tire showing an example of the embodiment of the pneumatic tire of the present invention.

The present invention will be described.
The present invention includes 30 to 180 parts by mass of silica and 1 to 50 parts by mass of cerium oxide with respect to 100 parts by mass of the diene rubber having an average glass transition temperature of −80 to −20 ° C. It is a rubber composition for tires containing 3-20 mass% of sulfur containing silane coupling agents which have an average composition formula represented by the ratio to the total amount of the silica and the cerium oxide.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} ... Formula (1)
Here, in formula (1), A represents a divalent organic group containing a sulfide group. B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. C represents a hydrolyzable group. D represents an organic group containing a mercapto group. R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. a to e satisfy the relational expressions of 0 ≦ a <1, 0 <b <1, 0 <c <3, 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4.
Hereinafter, such a rubber composition for tire is also referred to as “the composition of the present invention”.

<Diene rubber>
The diene rubber contained in the composition of the present invention is not particularly limited as long as it has a double bond in the main chain and has an average glass transition temperature of -80 to -20 ° C. Examples include natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), ethylene-propylene-diene copolymer Examples include coalesced rubber (EPDM), styrene-isoprene rubber, isoprene-butadiene rubber, nitrile rubber, and hydrogenated nitrile rubber.

As the diene rubber, for example, one kind in the above specific examples may be used alone, or two or more kinds may be used in combination.
When using individually by 1 type, the glass transition temperature of the diene rubber is -80 to -20 ° C.
When using 2 or more types together, the value which multiplied and added each mass% of each component to the glass transition temperature of each component is -80--20 degreeC.

  The glass transition temperature of the diene rubber is measured by differential scanning calorimetry (DSC) with a temperature increase rate of 20 ° C./minute, and a low-temperature baseline and a slope of the transition region (slope straight line). The temperature at the intersection of the extension lines. When the diene rubber is an oil-extended product, the glass transition temperature of the diene rubber in a state not containing an oil-extended component (oil) is used.

  As the diene rubber, styrene-butadiene rubber (SBR) and butadiene rubber (BR) are preferably used, and more preferably used in combination, because the wet performance and the low fuel consumption performance can be balanced.

  When styrene-butadiene rubber (SBR) and butadiene rubber (BR) are used in combination as the diene rubber, the SBR in the diene rubber is preferably 50 to 100% by mass, and 60 to 80% by mass. Is more preferable. Within this range, the general physical properties of the rubber composition after vulcanization will be better.

<Silica>
The silica which the composition of this invention contains is not specifically limited, The conventionally well-known arbitrary silica currently mix | blended with the rubber composition for uses, such as a tire, 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.

The silica has a nitrogen adsorption specific surface area (N ₂ SA) of 194 to 225 m ² / g, a CTAB specific surface area (CTAB) of 180 to 210 m ² / g, a DBP absorption of 190 ml / 100 g or more, it is preferred ratio of ₂ SA and the CTAB (N ₂ SA / CTAB) is 0.9 to 1.4. In this case, the content of the silica is more preferably 60 to 150 parts by mass with respect to 100 parts by mass of the diene rubber.

Nitrogen adsorption specific surface area of the silica (N ₂ SA) of is preferably 194~220m ² / g, more preferably 200~220m ² / g. When N ₂ SA is too high, the mixing property is deteriorated and the kneading becomes uneven, making it difficult to obtain a stable rubber material.
Note that N ₂ SA of silica is determined in accordance with JIS K6217-2.

Preferably CTAB specific surface area of the silica (CTAB) is 180~200m ² / g, more preferably 190~200m ² / g. When CTAB is too high, rolling resistance is deteriorated, which is not preferable.
In addition, CTAB of a silica shall be calculated | required based on JISK6217-3.

The ratio of N ₂ SA to CTAB (N ₂ SA / CTAB) of silica is preferably 1.0 to 1.3. If this ratio (N ₂ SA / CTAB) is too low, the reinforcing property tends to decrease. On the other hand, if this ratio of silica is too high, the dispersibility of the silica is lowered, and the rolling resistance tends to deteriorate.

The DBP absorption amount of silica is preferably 195 ml / 100 g or more, and more preferably 200 ml / 100 g or more. If the DBP absorption is too low, the tensile strength at break tends to decrease. The upper limit of the DBP absorption amount is not particularly limited, but is preferably 250 ml / 100 g or less. If the DBP absorption amount is too high, the viscosity tends to increase and the processability tends to deteriorate.
In addition, the DBP absorption amount of silica shall be calculated | required based on JISK6217-4 oil absorption amount A method.

  In the present invention, the silica content is 30 to 180 parts by mass with respect to 100 parts by mass of the diene rubber, and the resulting tire has good wear resistance and a good balance of fuel efficiency. Therefore, it is more preferable that it is 60-150 mass parts, and it is further more preferable that it is 80-130 mass parts.

<Cerium oxide>
The cerium oxide 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, and more preferably 20 to 50 nm.

  The average particle size was obtained by taking a photograph of cerium oxide at a magnification of 5000 times using a transmission electron microscope (TEM), arbitrarily selecting 500 particles from the obtained photos, and using each caliper to calculate the projected area equivalent circle diameter. Is measured to obtain an integrated particle size distribution (volume basis), and an average particle diameter (median diameter) is calculated therefrom to obtain a calculated value.

Examples of cerium oxide include those represented by chemical formulas such as CeO ₂ and Ce ₂ O ₃ .

  In the present invention, the content of the cerium oxide is 1 to 50 parts by mass with respect to 100 parts by mass of the diene rubber, more preferably 5 to 45 parts by mass, and 10 to 40 parts by mass. Further preferred. When the blending amount of cerium oxide is less than 1 part by mass, the low rolling property, wet performance and wear performance of the tire are not improved, and when it exceeds 50 parts by mass, the wear performance tends to decrease.

<Sulfur-containing silane coupling agent>
The sulfur-containing silane coupling agent contained in the composition of the present invention has an average composition formula represented by the above formula (1).

  In the formula (1), A is a divalent organic group containing a sulfide group. When subscript a = 0, A does not exist, and when 0 <a <1, A exists. The presence of A makes it possible to increase the molecular weight of two siloxane compounds by bridging them. Thereby, the content rate of a mercapto group can be made small and the workability of a rubber composition can be maintained. On the other hand, when A does not exist (a = 0), the sulfur-containing silane coupling agent has a feature of being more reactive with silica.

  The divalent organic group A containing a sulfide group is not particularly limited as long as it is an organic group in which one or more sulfide groups are bonded to one or more divalent hydrocarbon groups. An organic group in which a divalent hydrocarbon group is bonded to both sides of one or more sulfide groups is preferable. Examples of the divalent hydrocarbon group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic cyclized hydrogen group, and an aliphatic hydrocarbon group is preferable. Examples of the aliphatic hydrocarbon group include a methylene group, an alkylene group having 2 to 10 carbon atoms, and an alkenylene group. The alkylene group and alkenylene group having 4 or more carbon atoms may be either linear or branched.

The divalent organic group A containing a sulfide group may be, for example, an organic group represented by the following formula (2).
_{- (CH 2) n -S x} - (CH 2) n - ···· formula (2)
In formula (2), n represents an integer of 1 to 10, and x represents an integer of 1 to 4. n is an integer of 1 to 10, preferably an integer of 2 to 5.
By making n an integer in such a range, both reactivity with silica and workability can be achieved.
x is an integer of 1 to 4, preferably an integer of 2 to 4. By making x an integer in such a range, workability can be further improved.

As the divalent organic group A containing sulfide groups, _{e.g., -C 3 H 6 -S 2 -C} 3 H 6 -, - CH 2 -S 2 -CH 2 -, - C 2 H 4 -S 2 - _{C 2 H 4 -, - C} 4 H 8 -S 2 -C 4 H 8 -, - C 3 H 6 -S 4 -C 3 H 6 -, - CH 2 -S 4 -CH 2 -, - C 2 _{H 4 -S 4 -C 2 H 4} -, - C 4 H 8 -S 4 -C 4 H 8 - , etc. can be exemplified. Among them _{-C 3 H 6 -S 2 -C 3} H 6 -, - C 3 H 6 -S 4 -C 3 H 6 - is preferable.

  In the formula (1), B is a monovalent hydrocarbon group having 5 to 10 carbon atoms. Examples of the monovalent hydrocarbon group B include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic cyclized hydrogen group, and an aliphatic hydrocarbon group is preferable. The aliphatic hydrocarbon group may be linear or branched, and may be, for example, an alkyl group or an alkenyl group having 5 to 10 carbon atoms, more preferably 6 to 9 carbon atoms. Examples of the hydrocarbon group B include a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. Of these, the monovalent hydrocarbon group B is preferably an octyl group. The monovalent hydrocarbon group B preferably does not contain a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom.

  The subscript b indicating the abundance ratio of the monovalent hydrocarbon group B is a real number of 0 <b <1. The subscript b is preferably 0.10 <b <0.89 when the subscript a = 0. The subscript b is also preferably 0.10 <b <0.89 when 0 <a <1.

In the formula (1), C is a monovalent hydrolyzable group. Examples of the hydrolyzable group C include an alkoxy group, a carboxyl group, an alkenyloxy group, a phenoxy group, and the like. Preferably, the hydrolyzable group C is represented by the following formula (3).
-OR ² ··· Formula (3)
In Formula (3), R ² represents an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms.

  The hydrolyzable group C is preferably an alkoxy group, more preferably an alkoxy group having 1 to 4 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and an isopropoxy group. . Of these, an ethoxy group is preferable.

  The subscript c indicating the abundance ratio of the hydrolyzable group C is a real number of 0 <c <3. The subscript c is preferably 0 <c <2.0, more preferably 1.2 <c <2.0, when the subscript a = 0. The subscript c is preferably 0 <c <2.5, more preferably 0.5 <c <2.0, when 0 <a <1.

In the formula (1), D is a monovalent organic group containing a mercapto group. The organic group D containing a mercapto group is not particularly limited. For example, at least one hydrogen atom of an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic cyclized hydrogen group is substituted with a mercapto group. If it was done. The aliphatic hydrocarbon group to which the mercapto group is bonded may be either linear or branched. The organic group D containing a mercapto group may be represented by the following formula (4).
- (CH _{2) m} -SH ···· (4)
In formula (4), m represents an integer of 1 to 10.

  The organic group D containing a mercapto group is preferably an alkyl group having a mercapto group having 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms. Examples include a mercaptomethyl group, a mercaptoethyl group, a mercaptopropyl group, a mercaptobutyl group, a mercaptopentyl group, a mercaptohexyl group, a mercaptoheptyl group, a mercaptooctyl group, a mercaptononyl group, and a mercaptodecyl group. Of these, a mercaptopropyl group, particularly a 3-mercaptopropyl group is preferred.

  The subscript d indicating the proportion of the organic group D containing a mercapto group is a real number of 0 <d <1. The subscript d is preferably 0.1 <d <0.8 when the subscript a = 0. The subscript d is also preferably 0.1 <d <0.8 when 0 <a <1.

In the formula (1), R ¹ is a monovalent hydrocarbon group having 1 to 4 carbon atoms. Examples of the hydrocarbon group R ¹ include a methyl group and an alkyl group having 2 to 4 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, an n-butyl group, and an isopropyl group, and an ethyl group is preferable.

The subscript e indicating the abundance ratio of the monovalent hydrocarbon group R ¹ is a real number of 0 ≦ e <2. The subscript e is preferably 0.1 <e <1.6 when the subscript a = 0. The subscript e is preferably 0.1 <e <0.8 when 0 <a <1.

  The subscripts a to e described above satisfy the relationship 0 <2a + b + c + d + e <4. When the subscript a = 0, preferably 0.3 <b + c + d + e <3.5, more preferably 0.5 <b + c + d + e <3.0. Further, when 0 <a <1, preferably 0.5 <2a + b + c + d + e <3.5, more preferably 0.8 <2a + b + c + d + e <3.0.

  When the subscripts a to e satisfy the relational expression described above, the dispersibility of the silica can be improved while ensuring the processability of the rubber composition.

  In the formula (1), the abundance ratio of the average composition SiO is represented by (4-2a-b-c-d-e) / 2.

  The sulfur-containing silane coupling agent having the average composition formula represented by the formula (1) can be produced by a usual synthesis method. Moreover, you may use it selecting suitably from commercially available silane coupling agents.

In the sulfur-containing silane coupling agent used in the present invention, when a in the formula (1) is 0 <a <1, 0 <c <3, and A, C, and D are the formulas (2) (3 ) And (4).
In the sulfur-containing silane coupling agent used in the present invention, when a in the formula (1) is a = 0, 0 <c <2, 0 ≦ e <2, and B has 5 to 10 carbon atoms. It is preferable that the alkyl group of D is represented by the said Formula (4).

  In the present invention, the content of the sulfur-containing silane coupling agent is a ratio to the total amount of the silica and the cerium oxide (the content of the sulfur-containing silane coupling agent / (the content of silica + the content of cerium oxide). Amount) × 100) is 3 to 20% by mass, preferably 5 to 15% by mass, and more preferably 7 to 10% by mass. When the blending amount of the sulfur-containing silane coupling agent is less than 3% by mass with respect to the total amount of the silica and the cerium oxide, the low fuel consumption performance, wet performance, and wear resistance of the tire are not improved. Processability also deteriorates. On the other hand, when the ratio with respect to the total amount of the said silica and the said cerium oxide becomes higher than 20 mass%, there exists a tendency for abrasion performance to fall.

<Other ingredients>
In addition to the above components, the composition of the present invention includes an aromatic terpene resin, a filler other than silica (for example, carbon black), a silane coupling agent other than the above sulfur-containing silane coupling agent, and vulcanization. Or various other additives generally used for rubber compositions for tires, such as crosslinking agents, vulcanization or crosslinking accelerators, zinc oxide, softeners (oils), anti-aging agents, plasticizers, etc. Can do. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

For example, the content of fillers other than silica (for example, carbon black) is preferably 4 to 30 parts by mass, and more preferably 5 to 25 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the vulcanizing agent or the crosslinking agent is preferably 0.3 to 3.0 parts by mass and more preferably 0.5 to 2.5 parts by mass with respect to 100 parts by mass of the diene rubber. preferable.
The content of the vulcanization accelerator or the crosslinking accelerator is preferably 0.5 to 4.0 parts by mass with respect to 100 parts by mass of the diene rubber in the form of a primary accelerator alone or a blend with a secondary. It is more preferable that it is 0.0-2.5 mass parts.
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 10 to 60 parts by mass and more preferably 15 to 45 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the anti-aging agent 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.
The content of a plasticizer such as a thermoplastic resin is preferably 0 to 30 parts by mass and more preferably 0 to 20 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.
Among the above components, components other than the vulcanization (crosslinking) agent and the vulcanization (crosslinking) accelerator are mixed and kneaded to create a master batch, and the vulcanization (crosslinking) agent and vulcanization (crosslinking) are added to this master batch. ) It is preferable to produce a rubber composition by mixing an accelerator and kneading using 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 into the masterbatch. When kneaded, the vulcanization (crosslinking) rubber and the vulcanization (crosslinking) accelerator can be mixed to shorten the kneading time, resulting in non-uniform vulcanization (crosslinking). The physical properties of the composition can be prevented from being lowered, and vulcanization (crosslinking) can be easily controlled.

[Pneumatic tire]
The pneumatic tire of the present invention is a pneumatic tire manufactured using the composition of the present invention described above. Especially, it is preferable that it is a pneumatic tire manufactured using the composition of this invention for a tire tread.
FIG. 1 shows a schematic partial sectional view of a tire representing 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.
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.

  The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. Moreover, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

  The pneumatic tire of the present invention is excellent in wear performance and workability.

  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 1-4, Comparative Examples 1-4>
As shown in the column of the standard example, the column of the example of Table 1, and the column of the comparative example, the rubber compositions according to the standard example, the examples 1 to 4 and the comparative examples 1 to 4 have the components shown in Table 1. Were blended in the blending amounts shown in Table 1.
Specifically, first, among the components shown in Table 1 below, the components excluding sulfur and the vulcanization accelerator were mixed for 5 minutes using a 1.7 liter closed Banbury mixer, and reached 150 ± 5 ° C. Was released and cooled to room temperature to obtain a masterbatch. Furthermore, using the Banbury mixer, sulfur and a vulcanization accelerator were mixed with the obtained master batch to obtain a rubber composition.

  In Table 1, SBR indicates the amount (unit: part by mass) of the oil-extended product, and the value in parentheses indicates the net amount (unit: part by mass) of SBR contained in SBR.

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

[Test evaluation method]
<Viscosity change>
First, using a BS viscometer (1 rpm), the initial viscosity of the obtained composition was measured under the condition of 20 ° C. (unit: Pa · s).
Next, the viscosity (viscosity after accelerated test) after placing the obtained composition under the condition of 70 ° C. for 3 days was measured in the same manner.
Further, the measured initial viscosity and post-acceleration viscosity were applied to the following formula to determine the viscosity change rate.
Viscosity change rate (%) = (viscosity after accelerated test / initial viscosity) × 100
The results are shown in Table 1. The results are shown as an index with the viscosity change rate of the standard example as 100. The lower the index, the better the storage stability.

<Processability>
For the rubber composition (unvulcanized) produced as described above, the scorch time was measured in accordance with JIS K6300-1: 2001 using an L-shaped rotor and at a test temperature of 125 ° C.
The results are shown in Table 1. The results are shown as an index with a standard example scorch time of 100. The larger the index, the longer the scorch time and the better the workability.

<Abrasion resistance>
The vulcanized rubber sheet produced as described above is subjected to wear loss under the conditions of a temperature of 20 ° C. and a slip rate of 50% using a Lambone abrasion tester (manufactured by Iwamoto Seisakusho) in accordance with JIS K6264-1, 2: 2005. It was measured.
The results are shown in Table 1. The results were expressed as an index according to the following formula, with the wear amount of the standard example being 100. The larger the index, the smaller the amount of wear, and the better the wear resistance when made into a tire.
Abrasion resistance = (Abrasion amount of standard example / Abrasion amount of sample) × 100

[Specific description of each component in the table]
The details of each component shown in the table are as follows.
SBR: Styrene butadiene rubber having a hydroxyl group (trade name E581, manufactured by Asahi Kasei Co., Ltd.): Oil-extended product (styrene content: 73% by mass), Tg: −27 ° C., weight average molecular weight: 1,260,000
BR: Butadiene rubber, Nipol 1220 manufactured by Nippon Zeon
・ Carbon black: Show black N339 (manufactured by Cabot Japan)
Silica 1: 200 MP (N ₂ SA = 207, CTAB = 198 m ² / g, N ₂ SA / CTAB = 1.1, DBP adsorption amount = 206 ml / g)
Silica 2: 1165 MP (N ₂ SA = 160, CTAB = 159 m ² / g, N ₂ SA / CTAB = 1.0, DBP adsorption amount = 200 ml / g)
-Cerium oxide 1: Nanotechnology Nano-D CEP average particle size = 25-45 nm
-Cerium oxide 2: Nanotechnology Nano-D CEN average particle diameter = 30-45 nm
Silane coupling agent 1: average composition formula _{C 2 H 5 OSi-O [} (CH 2 CH 2 O) 5 -C 13 H 27] 2 - (CH 2) a sulfur-containing silane coupling represented by ₃ -SH Agent, Si363 manufactured by Evonik Degussa
Silane coupling agent 2: Average composition formula (—C ₃ H ₆ —S ₄ —C ₃ H ₆ —) _0.071 (—C ₈ H ₁₇ ) _0.571 (—OC ₂ H ₅ ) _1.50 (—C ₃ H ₆ SH ) Sulfur-containing silane coupling agent represented by _0.286 SiO _0.75 , 9511D manufactured by Shin-Etsu Chemical Co., Ltd.
・ Stearic acid: Beads stearic acid (manufactured by NOF Corporation)
・ Zinc flower: 3 types of zinc oxide
-Anti-aging agent: 6PPD manufactured by Flexis
・ Process oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
・ Vulcanization accelerator 1: CZ: Noxeller CZ-G (manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization accelerator 2: DPG: Soxinol DG (Sumitomo Chemical Co., Ltd.)

[Explanation of test results]
<Examples 1-4>
In Examples 1-4, the thing excellent in abrasion performance, workability, and storage stability (viscosity change) was obtained.

<Comparative Example 1>
This is an embodiment that does not contain cerium oxide. In this case, wear performance and workability deteriorated.

<Comparative example 2>
This is an embodiment with little silica. In this case, workability deteriorated.

<Comparative Example 3>
This is an embodiment in which the average glass transition temperature of the diene rubber is low. In this case, workability deteriorated.

<Comparative example 4>
This is an embodiment with a large amount of cerium oxide and a small amount of silica. In this case, the wear resistance deteriorated.

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

Claims (4)

30 to 180 parts by mass of silica and 1 to 50 parts by mass of cerium oxide are included with respect to 100 parts by mass of the diene rubber having an average glass transition temperature of −80 to −20 ° C., and further represented by the following formula (1). A rubber composition for tires, comprising a sulfur-containing silane coupling agent having an average composition formula in a ratio of 3 to 20% by mass with respect to the total amount of silica and cerium oxide.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} ... Formula (1)
(In formula (1), A represents a divalent organic group containing a sulfide group, B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms, C represents a hydrolyzable group, and D represents R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, a to e are 0 ≦ a <1, 0 <b <1, 0 <c <3 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4.   The tire rubber composition according to claim 1, wherein the cerium oxide is fine particles having an average particle diameter of 20 to 60 nm. The silica has a nitrogen adsorption specific surface area (N ₂ SA) of 194 to 225 m ² / g, a CTAB specific surface area (CTAB) of 180 to 210 m ² / g, a DBP absorption of 190 ml / 100 g or more, and the N ₂ SA and The CTAB ratio (N ₂ SA / CTAB) is 0.9 to 1.4, and the silica content is 60 to 150 parts by mass with respect to 100 parts by mass of the diene rubber. The tire rubber composition according to claim 1 or 2,   A pneumatic tire using the rubber composition according to claim 1 for a tire tread.

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