JP2014177535A - Rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition excellent in low rolling resistance when using it to make a tire and processability.SOLUTION: There is provided a rubber composition containing diene rubber (A), silica (B) and rapeseed oil (C) having an iodine value of 80 to 100, and the content of the silica (B) is 5 to 200 pts.mass based on 100 pts.mass of the diene rubber (A), the content of the rapeseed oil (C) is 1 to 20 pts.mass based on 100 pts.mass of the diene rubber (A).

Description

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

  In recent years, there has been a demand for reducing tire rolling resistance in order to improve fuel efficiency during vehicle travel. Therefore, a method is known in which silica is added to the diene rubber constituting the tread portion of the tire to reduce hysteresis loss (particularly, tan δ at high temperatures), thereby reducing heat generation and reducing tire rolling resistance. Yes.

  For example, Claim 1 of Patent Document 1 discloses a rubber composition for a tire tread containing a diene rubber and silica. Patent Document 1 describes that the rolling resistance of a tire can be lowered by adopting the configuration of claim 1.

  On the other hand, rubber compositions for tires and the like are required to have excellent processability in the storage stage and the stage before the vulcanization process.

JP 2011-241362 A

Under these circumstances, the present inventors examined a rubber composition containing a diene rubber and silica based on Patent Document 1, and although the rolling resistance when it is certainly made into a tire is low, It became clear that the level required recently has not been met.
In view of the above circumstances, an object of the present invention is to provide a rubber composition that is excellent in low rolling resistance and excellent in processability when formed into a tire.

As a result of intensive studies on the above problems, the present inventors have formulated a rubber composition that is excellent in low rolling resistance and excellent in processability when blended with rapeseed oil having a specific iodine value. As a result, the present invention was found.
That is, the present inventors have found that the above problem can be solved by the following configuration.

(1) containing a diene rubber (A), silica (B), and rapeseed oil (C) having an iodine value of 80 to 100,
The content of the silica (B) is 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber (A),
The rubber composition whose content of the said rapeseed oil (C) is 1-20 mass parts with respect to 100 mass parts of said diene rubbers (A).
(2) The rubber composition according to (1), wherein the rapeseed oil (C) is hydrogenated rapeseed oil.
(3) A pneumatic tire using the rubber composition according to the above (1) or (2) for a tire tread.

  As shown below, according to the present invention, it is possible to provide a rubber composition that is excellent in low rolling resistance and excellent in workability when formed into a tire.

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

  Below, the rubber composition of this invention and the pneumatic tire using the rubber composition of this invention are demonstrated.

(Rubber composition)
The rubber composition of the present invention (hereinafter also simply referred to as the composition of the present invention) contains a diene rubber (A), silica (B), and rapeseed oil (C) having an iodine value of 80 to 100. The content of the silica (B) is 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber (A), and the content of the rapeseed oil (C) is the diene rubber (A ) 1 to 20 parts by mass with respect to 100 parts by mass.

Since the composition of the present invention contains rapeseed oil having a specific iodine value as described above, it is considered that when it is made into a tire, it has excellent low rolling resistance and excellent workability.
This indicates that, as shown in a comparative example to be described later, when the rapeseed oil is not blended (Comparative Example 1), the processability becomes insufficient or the iodine value of the rapeseed oil is within a specific range even when the rapeseed oil is blended. If not (Comparative Examples 4 and 5), it is presumed that the workability and / or the low rolling resistance is insufficient.

  The diene rubber (A), silica (B), rapeseed oil (C) and other components that may be optionally contained are described in detail below.

<Diene rubber (A)>
The diene rubber (A) used in the composition of the present invention is not particularly limited. Specific examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), and aromatic vinyl-conjugated diene. Examples thereof include copolymer rubber, acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), and chloroprene rubber (CR). The diene rubber (A) may be a single diene rubber or a combination of two or more diene rubbers.

As the diene rubber (A), an aromatic vinyl-conjugated diene copolymer rubber is preferably used for the reason that the resulting tire is excellent in rigidity and grip performance, and an aromatic vinyl-conjugated diene copolymer is preferably used. It is more preferable to use butadiene rubber (BR) together.
Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene copolymer rubber (SBR) and styrene-isoprene copolymer rubber. Among these, styrene-butadiene copolymer rubber (SBR) is preferable because the obtained tire has excellent rigidity and excellent grip performance.

The aromatic vinyl-conjugated diene copolymer has an aromatic vinyl content (for example, styrene content) of preferably 20 to 45% by mass because of its reactivity with silica, and 23 to 42% by mass. % Is more preferable.
Further, the vinyl bond content in the conjugated diene of the aromatic vinyl-conjugated diene copolymer is preferably 10 to 50%, preferably 25 to 48%, because it has reactivity with silica. More preferred. Here, the amount of vinyl bonds refers to the ratio of 1,2-vinyl bonds among cis-1,4-bonds, trans-1,4-bonds and 1,2-vinyl bonds, which are conjugated dienes. Say.

The said aromatic vinyl-conjugated diene copolymer is not specifically limited about the manufacturing method, It can manufacture by a conventionally well-known method.
Moreover, the aromatic vinyl and conjugated diene as a monomer used when manufacturing the said aromatic vinyl-conjugated diene copolymer are not specifically limited.
Here, examples of the conjugated diene monomer include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and 2-chloro-1. , 3-butadiene, 1,3-pentadiene and the like.
On the other hand, examples of the aromatic vinyl monomer include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, Examples include 4-tert-butylstyrene, divinylbenzene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl) dimethylaminoethyl ether, N, N-dimethylaminoethylstyrene, and vinylpyridine.

The content in the case of using the aromatic vinyl-conjugated diene copolymer is preferably 50% by mass or more of the diene rubber (A), because the resulting tire has excellent rigidity and excellent grip performance. , 55% by mass or more, more preferably 60% by mass or more.
Further, when the butadiene rubber (BR) is used in combination with the aromatic vinyl-conjugated diene copolymer, the content of the butadiene rubber (BR) is determined from the viewpoint of wet performance and wear resistance of the obtained tire. It is preferably less than 50% by mass of the diene rubber (A), more preferably less than 45% by mass, and even more preferably less than 40% by mass.

  The weight average molecular weight of the diene rubber (A) is preferably 100,000 to 1,500,000 from the viewpoint of the toughness of the obtained tire and the handling of the composition of the present invention, and 600,000 to 1 , 300,000 is more preferable. The weight average molecular weight (Mw) of the diene rubber (A) is measured in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

<Silica (B)>
The silica (B) used in the composition of the present invention is not particularly limited, and any conventionally known silica that is blended in a rubber composition for uses such as tires can be used.
Examples of the silica (B) include wet silica, dry silica, fumed silica, and diatomaceous earth. As the silica (B), one type of silica may be used alone, or two or more types of silica may be used in combination.
In the present invention, the silica (B) is preferably wet silica from the viewpoint of rubber reinforcement.

The silica (B) is from wet performance and wear resistance of the viewpoint of the resulting tire, it is preferable that the nitrogen adsorption specific surface area (N ₂ SA) is 100 to 300 m ² / g, in 140~200m ² / g More preferably.
Here, N ₂ SA is a surrogate property of the surface area that silica can use for adsorption with rubber molecules, and the amount of nitrogen adsorbed on the silica surface is determined according to JIS K6217-2: 2001 “Part 2: Determination of specific surface area— It is a value measured according to the “nitrogen adsorption method—single point method”.

  In the composition of the present invention, the content of the silica (B) is 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber (A), and the resulting tire has wet performance and wear resistance. From the viewpoint, it is preferably 20 to 140 parts by mass, and more preferably 35 to 130 parts by mass.

<Rapeseed oil (C)>
The rapeseed oil (C) used in the composition of the present invention is not particularly limited as long as it is rapeseed oil having an iodine value of 80 to 100.
Here, the iodine value is measured in accordance with JIS K0070: 1992. Specifically, when halogen is reacted with 100 g of the sample, the amount of halogen bonded is converted to the number of g of iodine. It is.

  The iodine value of the rapeseed oil (C) is preferably 85 to 95 because both the melting point of the oil and the oxidation resistance of the oil are compatible.

  The rapeseed oil (C) is preferably hydrogenated (hydrogenated) rapeseed oil for the reason of achieving both the melting point of the oil and the oxidation resistance.

  It is preferable that the said rapeseed oil (C) is a liquid in the temperature range (for example, room temperature-200 degreeC) to be used.

  The weight average molecular weight of the rapeseed oil (C) is preferably 300 to 1000, more preferably 500 to 800, for the reason that the melting point and plasticity of the oil are excellent. The weight average molecular weight (Mw) of rapeseed oil (C) is measured in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

In the composition of the present invention, the content of the rapeseed oil (C) is 1 to 20 parts by mass with respect to 100 parts by mass of the diene rubber (A). It is preferably 20 parts by mass, more preferably 10 to 20 parts by mass, and even more preferably 12 to 20 parts by mass.
If the content of the rapeseed oil (C) is less than 1 part by mass with respect to 100 parts by mass of the diene rubber (A), processability becomes insufficient. Moreover, when content of rapeseed oil (C) exceeds 20 mass parts with respect to 100 mass parts of diene rubber (A), low rolling resistance will become inadequate.

<Optional component>
If necessary, the composition of the present invention may further contain an additive within a range not impairing its effects and purposes.
Examples of the additive include a silane coupling agent, a filler other than the silica (B) (for example, carbon black), zinc oxide, stearic acid, an antioxidant, a processing aid, an aroma oil, a liquid polymer, and a terpene. Various additives generally used in rubber compositions such as a resin, a thermosetting resin, a vulcanizing agent, and a vulcanization accelerator can be used.

  The composition of the present invention preferably contains a silane coupling agent because the dispersibility of the silica (B) is improved.

(Silane coupling agent)
Specific examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, Mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide And dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide. These may be used alone or in combination of two or more.

Moreover, as a suitable aspect of the said silane coupling agent, for example, a mercapto silane coupling agent having a polyether chain and / or a mercapto silane coupling agent having a polysiloxane structure (—Si—O—) is used. Etc.
Here, the polyether chain is a side chain having two or more ether bonds, and specific examples thereof include, for example, a side chain having two or more structural units —R ^a —O—R ^b — in total. Can be mentioned. Here, in the structural unit, R ^a and R ^b are each independently a linear or branched alkylene group, a linear or branched alkenylene group, a linear or branched alkynylene group, Alternatively, it represents a substituted or unsubstituted arylene group. Of these, a linear alkylene group is preferable.

  As a suitable aspect of the mercapto type | system | group silane coupling agent which has the said polyether chain | strand, the compound represented by following formula (2) is mentioned, for example.

In the above formula (2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms, among them, preferably an alkoxy group having 1 to 3 carbon atoms. Examples of the alkoxy group having 1 to 3 carbon atoms include a methoxy group and an ethoxy group. A plurality of R ²¹ when l is 2 may be the same or different.
In the formula (2), R ²² represents a straight-chain polyether group having 4 to 30 carbon atoms. The polyether group is a group having two or more ether bonds, and specific examples thereof include a group having two or more structural units —R ^a —O—R ^b — in total. Definitions and preferred embodiments of R ^a and R ^b are the same as R ^a and R ^b as described above. When m is 2, the plurality of R ²² may be the same or different.
As a suitable aspect of a C4-C30 linear polyether group, group represented by following formula (5) is mentioned.

In the above formula (5), R ⁵¹ represents a linear alkyl group, a linear alkenyl group, or a linear alkynyl group, and among them, a linear alkyl group is preferable. As the linear alkyl group, a linear alkyl group having 1 to 20 carbon atoms is preferable, and a linear alkyl group having 8 to 15 carbon atoms is more preferable. Specific examples of the linear alkyl group having 8 to 15 carbon atoms include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group and the like, and tridecyl group is particularly preferable.
In the above formula (5), R ⁵² represents a linear alkylene group, a linear alkenylene group or a linear alkynylene group, and among them, a linear alkylene group is preferable. As said linear alkylene group, a C1-C2 linear alkylene group is preferable and an ethylene group is more preferable.
In said formula (5), p represents the integer of 1-10 and it is preferable that it is 3-7.
In the above formula (5), * indicates a bonding position.

In the formula (2), R ²³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
In the above formula (2), R ²⁴ represents an alkylene group having 1 to 30 carbon atoms, among them preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms. Specific examples of the alkylene group having 1 to 5 carbon atoms include a methylene group, an ethylene group, and a propylene group.
In said formula (2), l represents the integer of 1-2 and it is preferable that it is 1. In said formula (2), m represents the integer of 1-2 and it is preferable that it is 2. n represents an integer of 0 to 1, and is preferably 0. l, m, and n satisfy the relationship of l + m + n = 3.

  On the other hand, as a suitable embodiment of the mercapto-based silane coupling agent having the polysiloxane structure, for example, a copolymer having a repeating unit represented by the following formula (3) and a repeating unit represented by the following formula (4): Things.

In the above formulas (3) and (4), R ³¹ and R ⁴¹ each independently represent an alkylene group having 1 to 5 carbon atoms, and specific examples thereof include a methylene group, an ethylene group, and a propylene group. It is done. Of these, a propylene group is preferred. A plurality of R ³¹ and R ⁴¹ may be the same or different.
In the above formulas (3) and (4), R ³² and R ⁴² are each independently a linear or branched alkylene group having 1 to 30 carbon atoms, or a linear or branched carbon group having 2 to 30 carbon atoms. The alkenylene group or the linear or branched alkynylene group having 2 to 30 carbon atoms is preferable, and those having 3 to 20 carbon atoms are preferable. When R ³² is a terminal, R ³² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight chain. It represents a chain or branched alkynyl group having 2 to 30 carbon atoms, and among them, those having 3 to 20 carbon atoms are preferable. If R ⁴² is terminated, the definition of R ^42, specific examples and preferred embodiments are the same as above R ^32. A plurality of R ³² and R ⁴² may be the same or different.
In the above formulas (3) and (4), R ³³ and R ⁴³ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched group. A alkenyl group having 2 to 30 carbon atoms, a linear or branched alkynyl group having 2 to 30 carbon atoms, a linear or branched alkyl group having 1 to 30 carbon atoms, and a hydroxyl group or a carboxyl group at the terminal Or a linear or branched alkenyl group having 2 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at the terminal. R ⁴³ is preferably a group having a hydroxyl group at the terminal. R ³² and R ³³ may form a ring with R ³² and R ³³ . R ⁴² and R ⁴³ may form a ring with R ⁴² and R ⁴³ . A plurality of R ³³ and R ⁴³ may be the same or different.
R ³⁴ represents an alkyl group having 1 to 13 carbon atoms, and among them, an alkyl group having 3 to 10 carbon atoms is preferable. Specific examples of the alkyl group having 3 to 10 carbon atoms include a hexyl group, a heptyl group, and an octyl group. A plurality of R ³⁴ may be the same or different.

  In the composition of the present invention, the content of the silane coupling agent is 0.5 to 20% by mass with respect to the content of the silica (B) because the dispersibility of the silica (B) is further improved. It is preferable that it is 1-18 mass%, It is more preferable that it is 2-15 mass%.

<Method for producing rubber composition>
The production method of the composition of the present invention is not particularly limited, and specific examples thereof include, for example, kneading the above-described components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). The method etc. are mentioned.
The 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 is a pneumatic tire using the above-described composition of the present invention for a tire (preferably 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 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.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

<Examples 1-3, Comparative Examples 1-5>
The components shown in Table 1 below were blended in the proportions (parts by mass) shown in Table 1 below.
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, regarding the amount of SBR, the upper value is the amount of SBR (oil-extended product) (unit: parts by mass), and the lower value is the net amount of SBR contained in SBR (unit: parts by mass) It is.

<Mooney viscosity>
For the prepared rubber composition (unvulcanized), Mooney was used in accordance with JIS K6300-1: 2001, using an L-shaped rotor, with a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100 ° C. The viscosity was measured.
The results are shown in Table 1. The results were expressed as an index with the value of Comparative Example 1 as 100. The smaller the index, the lower the viscosity and the better the workability.

<Tan δ (60 ° C.)>
The prepared 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.
About the produced vulcanized rubber sheet, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.), conditions of stretch deformation strain rate 10% ± 2%, frequency 20 Hz, temperature 60 ° C. Then, tan δ (60 ° C.) was measured.
The results are shown in Table 1. The results were expressed as an index with tan δ (60 ° C.) of Comparative Example 1 as 100. The smaller the index, the smaller the tan δ (60 ° C.), and the lower the rolling resistance when the tire is made.

Details of each component shown in Table 1 are as follows.
Diene rubber A1 (SBR): E581 (oil-extended product (including 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR. The net content of SBR in SBR is 72.7% by mass), styrene content: 40 (Mass%, vinyl bond amount: 44%, weight average molecular weight: 1,260,000, manufactured by Asahi Kasei Corporation)
-Diene rubber A2 (BR): Nipol BR1200 (manufactured by Nippon Zeon)
Silica B1: Zeosil 1165GR (N ₂ SA: 165 m ² / g, manufactured by Rhodia)
Carbon black: Show black N339 (N ₂ SA: 90 m ² / g, manufactured by Cabot Japan)
Silane coupling agent: VP Si69 (Evonik Degussa) (bis (3-triethoxysilylpropyl) tetrasulfide)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Stearic acid YR (manufactured by NOF Corporation)
Anti-aging agent: Santoflex 6PPD (manufactured by Solutia Europe)
Aroma oil: Extract No. 4 S (manufactured by Showa Shell Sekiyu KK)
・ Rapeseed oil C1: hydrogenated rapeseed oil (hydrogenated product, iodine value: 88)
・ Rapeseed oil X1: Rapeseed oil (non-hydrogenated product, iodine value: 115)
・ Rapeseed oil X2: Rapeseed oil (hydrogenated product, iodine value: 76)
・ Sulfur: Oil-treated sulfur (manufactured by Karuizawa Refinery)
・ Vulcanization accelerator 1: Noxeller CZ-G (Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization accelerator 2: Perkacit DPG (manufactured by Flexsys)

The examples of the present application containing rapeseed oil (C) having an iodine value in a specific range (80 to 100) all showed excellent low rolling resistance and workability. Especially, Example 1 and 2 whose content of rapeseed oil (C) is 2-20 mass parts with respect to 100 mass parts of diene rubber (A) showed the more excellent workability. Especially, Example 1 whose content of rapeseed oil (C) is 12-20 mass parts with respect to 100 mass parts of diene rubber (A) showed the further outstanding workability.
On the other hand, Comparative Example 1 containing no rapeseed oil had insufficient processability. Moreover, although the rapeseed oil was contained but the iodine of rapeseed oil was not the specific range (80-100), the comparative examples 4 and 5 were inadequate in workability and / or low rolling resistance. Moreover, although rapeseed oil (C) whose iodine number is a specific range (80-100) is contained, content of rapeseed oil (C) is less than 1 mass part with respect to 100 mass parts of diene rubber (A). In Comparative Example 2, the processability was insufficient. Moreover, although rapeseed oil (C) whose iodine number is a specific range (80-100) is contained, content of rapeseed oil (C) is 20 mass parts with respect to 100 mass parts of diene rubber (A). In Comparative Example 3, the rolling resistance was low.

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 (3)

Containing a diene rubber (A), silica (B), and rapeseed oil (C) having an iodine value of 80 to 100,
The content of the silica (B) is 5 to 200 parts by mass with respect to 100 parts by mass of the diene rubber (A),
The rubber composition whose content of the said rapeseed oil (C) is 1-20 mass parts with respect to 100 mass parts of said diene rubbers (A).   The rubber composition according to claim 1, wherein the rapeseed oil (C) is hydrogenated rapeseed oil.   A pneumatic tire using the rubber composition according to claim 1 or 2 for a tire tread.