JP6988405B2 - Rubber composition for tires and pneumatic tires - Google Patents

Description

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

In recent years, it has been required to reduce the heat generation (hysteresis loss) of a tire from the viewpoint of low fuel consumption when the vehicle is running. On the other hand, a method of blending silica with a rubber component constituting a tread portion of a tire to reduce heat generation of the tire is known.
However, since silica has a low affinity with the rubber component and has high agglomeration between silicas, even if silica is simply mixed with the rubber component, the silica does not disperse and the effect of reducing heat generation is sufficiently obtained. There was a problem that it could not be done.

（Ｒ^１、Ｒ^４、Ｒ^５およびＲ^１０：炭素数１〜２０の炭化水素基、Ｘ^１：Ｓｉ、Ｓｎ又はＧｅ、ｐ：１〜３の整数） In response to such a problem, Patent Document 1 describes a rubber composition in which at least an inorganic filler and a dispersant for an inorganic filler are mixed with a rubber component, and the dispersant for an inorganic filler is a conjugated diene-based weight. Described is a rubber composition characterized by being composed of a modified conjugated diene-based polymer in which a structural unit or the like shown below is introduced into the coalescence ([Claim 1]).

(R ¹ , R ⁴ , R ⁵ and R ¹⁰ : hydrocarbon groups having 1 to 20 carbon atoms, X ¹ : Si, Sn or Ge, p: integers of 1 to 3)

Japanese Unexamined Patent Publication No. 2013-249359

Recently, due to environmental problems and resource problems, further reduction of heat generation of tires is required, and accordingly, silica-containing rubber compositions for tires have a dispersibility of silica (hereinafter, abbreviated as "silica dispersibility"). ) Is required to be further improved.
Then, when the present inventors examined the rubber composition described in Patent Document 1, it became difficult to adjust the vulcanization rate depending on the vulcanization accelerator used and the blending amount thereof, and the silica dispersibility It became clear that it does not always meet the level required these days.

Therefore, it is an object of the present invention to provide a rubber composition for a tire that maintains an appropriate vulcanization rate and has excellent silica dispersibility, and a pneumatic tire using the rubber composition for a tire.

As a result of diligent studies to solve the above problems, the present inventors have blended a mercapto-based silane coupling agent and a specific liquid polybutadiene rubber into a rubber composition containing a diene-based rubber and silica, and further guanidine. We have found that by blending a predetermined amount of the system vulcanization accelerator, an appropriate vulcanization rate is maintained and the silica dispersibility is improved, and the present invention has been completed.
That is, the present inventors have found that the above problem can be solved by the following configuration.

ここで、上記式（Ａ１）中、Ｒ^１１は炭素数１〜８のアルコキシ基を表し、Ｒ^１２は炭素数４〜３０の直鎖状のポリエーテル基を表し、Ｒ^１３は水素原子または炭素数１〜８のアルキル基を表し、Ｒ^１４は炭素数１〜３０のアルキレン基を表す。ｌは１〜３の整数を表し、ｍは０〜２の整数を表し、ｎは０〜１の整数を表し、ｌ、ｍおよびｎはｌ＋ｍ＋ｎ＝３の関係式を満たす。ｌが２または３である場合の複数のＲ^１１は、それぞれ同一であっても異なっていてもよく、ｍが２である場合の複数のＲ^１２は、それぞれ同一であっても異なっていてもよい。
［５］ 上記メルカプト系シランカップリング剤が、下記式（Ａ１）中のｍが０で表される化合物である、［４］に記載のタイヤ用ゴム組成物。
［６］ ［１］〜［５］のいずれかに記載のタイヤ用ゴム組成物をキャップトレッドに配置した空気入りタイヤ。 [1] Contains a diene-based rubber, silica, a mercapto-based silane coupling agent, a liquid polybutadiene rubber, and a guanidine-based vulcanization accelerator.
The silica content is 30 to 200 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the mercapto-based silane coupling agent is 1 to 20% by mass with respect to the content of the silica.
The 1,2 bond (vinyl bond) content of the liquid polybutadiene rubber is 80% by mass or more on average, and the 1,2 bond of each liquid polybutadiene rubber is contained when two or more kinds of liquid polybutadiene rubber are contained. (Vinyl bond) content is 60% by mass or more,
The liquid polybutadiene rubber has a weight average molecular weight of 1000 to 18000.
The content of the liquid polybutadiene rubber is 1 to 20 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the guanidine-based vulcanization accelerator is more than 0.6 parts by mass and less than 2.5 parts by mass with respect to 100 parts by mass of the diene-based rubber, and 3 with respect to the mass of the liquid polybutadiene rubber. A rubber composition for tires, which is ~ 60% by mass.
[2] The rubber composition for a tire according to [1], wherein the liquid polybutadiene rubber has a weight average molecular weight of 1000 to 10000.
[3] The rubber composition for a tire according to [1] or [2], wherein the silica has a CTAB adsorption specific surface area of 145 to 300 m ^{2 / g.}
[4] The rubber composition for a tire according to any one of [1] to [3], wherein the mercapto-based silane coupling agent is a compound represented by the following formula (A1).

Here, in the above formula (A1), R ¹¹ represents an alkoxy group having 1 to 8 carbon atoms, R ¹² represents a linear polyether group having 4 to 30 ^{carbon atoms, and R 13} represents a hydrogen atom or carbon. The number 1 to 8 represents an alkyl group, and R ¹⁴ represents an alkylene group having 1 to 30 carbon atoms. l represents an integer of 1 to 3, m represents an integer of 0 to 2, n represents an integer of 0 to 1, and l, m and n satisfy the relational expression of l + m + n = 3. a plurality of R ¹¹ when l is 2 or 3, each may be the same or different and a plurality of R ¹² when m is 2, even if each be the same or different good.
[5] The rubber composition for a tire according to [4], wherein the mercapto-based silane coupling agent is a compound in which m in the following formula (A1) is represented by 0.
[6] A pneumatic tire in which the rubber composition for a tire according to any one of [1] to [5] is arranged on a cap tread.

As shown below, according to the present invention, a rubber composition for a tire that maintains an appropriate vulcanization rate and has excellent silica dispersibility, and a pneumatic tire using the rubber composition for a tire are provided. Can be done.

It is a schematic partial sectional view of the tire which shows an example of embodiment of the pneumatic tire of this invention.

Hereinafter, the rubber composition for a tire of the present invention and the pneumatic tire using the rubber composition for a tire of the present invention will be described.
The numerical range represented by using "~" in the present specification means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

[Rubber composition for tires]
The rubber composition for a tire of the present invention (hereinafter, also simply abbreviated as "the rubber composition of the present invention") includes a diene-based rubber, silica, a mercapto-based silane coupling agent, a liquid polybutadiene rubber, and a guanidine-based rubber. Contains a sulfurization accelerator.
Here, the 1,2 bond content (hereinafter, also referred to as “vinyl bond content”) of the liquid polybutadiene rubber is 80% by mass or more on average, and contains two or more kinds of liquid polybutadiene rubber. The vinyl bond content of each liquid polybutadiene rubber is 60% by mass or more.
The weight average molecular weight of the liquid polybutadiene rubber is 1000 to 18000.
Further, regarding the content of each component, the content of the silica is 30 to 200 parts by mass with respect to 100 parts by mass of the diene-based rubber, and the content of the mercapto-based silane coupling agent is the content of the silica. The content is 1 to 20% by mass with respect to the amount, the content of the liquid polybutadiene rubber is 1 to 20 parts by mass with respect to 100 parts by mass of the diene-based rubber, and the content of the guanidine-based vulture accelerator is 1 to 20 parts by mass. The amount is more than 0.6 parts by mass and less than 2.5 parts by mass with respect to 100 parts by mass of the diene-based rubber, and is 3 to 60% by mass with respect to the mass of the liquid polybutadiene rubber. ..

In the present invention, as described above, a predetermined amount of a mercapto-based silane coupling agent and a specific liquid polybutadiene rubber are blended in a rubber composition containing a diene-based rubber and silica, and a predetermined amount of a guanidine-based vulcanization accelerator is added. By blending, an appropriate vulcanization rate is maintained and silica dispersibility is improved.
This is not clear in detail, but it is presumed to be as follows.
That is, because the guanidine-based vulcanization accelerator not only promotes the reaction (silanization) between silica and the mercapto-based silane coupling agent, but also promotes the reaction between the diene-based rubber and the mercapto-based silane coupling agent. However, when the blending amount of the guanidine-based vulcanization accelerator is a specific amount for each of the diene-based rubber and the liquid polybutadiene rubber, the balance of the above-mentioned promoting action is improved and an appropriate addition is made. It is considered that the vulcanization rate was maintained and the silica dispersibility was improved.
Hereinafter, each component contained in the rubber composition of the present invention will be described in detail.

[Diene rubber]
The diene-based rubber contained in the rubber composition of the present invention is not particularly limited, and specific examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), and aromatic vinyl-conjugated diene copolymer weight. Examples thereof include coalesced rubber, acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), and chloroprene rubber (CR). These may be used alone or in combination of two or more.
Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene copolymer rubber (SBR) and styrene isoprene copolymer rubber.
The diene rubber is a derivative in which the ends and side chains of each of the above rubbers are modified (modified) with an amino group, an amide group, a silyl group, an alkoxy group, a carboxy group, a hydroxy group, an epoxy group and the like. May be good.

Among these diene-based rubbers, it is preferable that the rubber is at least one selected from the group consisting of NR, IR, BR and aromatic vinyl-conjugated diene copolymer rubber, and preferably from the group consisting of NR, BR and SBR. It is more preferably at least one rubber selected, and even more preferably at least one rubber selected from the group consisting of BR and SBR.

In the present invention, the weight average molecular weight (Mw) of NR or IR is not particularly limited, but the silica dispersibility is better, and the workability, heat resistance, cold resistance, and deterioration resistance are excellent. It is preferably 000 to 3,000,000, more preferably 300,000 to 2,000,000, and even more preferably 400,000 to 1,500,000.
The weight average molecular weight (Mw) of BR or SBR is not particularly limited, but is 100,000 to 2 because the silica dispersibility is better and the processability, heat resistance, cold resistance, and deterioration resistance are excellent. It is preferably 1,,000,000, more preferably 150,000 to 1,000,000, and even more preferably 200,000 to 800,000.
In the present specification, the number average molecular weight (Mn) and the weight average molecular weight (Mw) are standard polystyrene-equivalent values obtained by gel permeation chromatography (GPC) measurement under the following conditions.
・ Solvent: Tetrahydrofuran ・ Detector: RI detector

In the present invention, it is preferable that 80% by mass or more of the diene-based rubber is at least one rubber selected from the group consisting of NR, IR, BR and aromatic vinyl-conjugated diene copolymerized rubber.
Among them, it is more preferable that 90% by mass to 100% by mass of the diene-based rubber is at least one rubber selected from the group consisting of NR, BR and SBR.

〔silica〕
The silica contained in the rubber composition of the present invention is not particularly limited, and any conventionally known silica blended in the rubber composition for applications such as tires can be used.
Examples of the silica include wet silica, dry silica, fumed silica, and diatomaceous earth. As the silica, one kind of silica may be used alone, or two or more kinds of silica may be used in combination.

In the present invention, the reason why the kneading property becomes good, silica is preferably CTAB adsorption specific surface area of 145~300m ² / g, more preferably 150~250m ² / g, 160~240m It is more preferably ^{2 / g.}
Here, the CTAB adsorption specific surface area was measured by measuring the amount of n-hexadecyltrimethylammonium bromide adsorbed on the silica surface according to JIS K6217-3: 2001 "Part 3: How to determine the specific surface area-CTAB adsorption method". The value.

Further, in the present invention, the content of the silica is 30 to 200 parts by mass, preferably 40 to 180 parts by mass, and 40 to 150 parts by mass with respect to 100 parts by mass of the diene rubber. Is more preferable.

[Mercapt-based silane coupling agent]
The mercapto-based silane coupling agent (silane coupling agent having a mercapto group) contained in the rubber composition of the present invention is not particularly limited as long as it is a silane compound having a mercapto group (-SH) and a hydrolyzable group. In addition, in this specification, a protected mercapto group in which a mercapto group is protected does not correspond to a mercapto group.
The hydrolyzable group is not particularly limited, and examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Of these, an alkoxy group is preferable because it has better silica dispersibility and is excellent in processability, heat resistance, cold resistance, and deterioration resistance. When the hydrolyzable group is an alkoxy group, the number of carbon atoms of the alkoxy group is preferably 1 to 16, and more preferably 1 to 4. Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, a propoxy group and the like.

The mercapto-based silane coupling agent may have an organic functional group other than the mercapto group.
Specific examples of such an organic functional group include an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group and the like.

In the present invention, the mercapto-based silane coupling agent is represented by the following formula (A1) because the silica dispersibility is better and the processability, heat resistance, cold resistance, and deterioration resistance are excellent. It is preferably a compound.

In the above formula (A1), R ¹¹ represents an alkoxy group having 1 to 8 carbon atoms, and among them, an alkoxy group having 1 to 3 carbon atoms is preferable. Examples of the alkoxy group having 1 to 3 carbon atoms include a methoxy group and an ethoxy group. When l is an integer of 2 or more, the plurality of R ^11s may be the same or different.

In the above formula (A1), R ¹² represents a linear 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− ^Rb − in total. Here, ^Ra and R ^b are independently linear or branched alkylene groups, linear or branched alkaneylene groups, linear or branched alkynylene groups, or substituted or absent. Represents a substituted arylene group. Of these, a linear alkylene group is preferable. When m is 2, the plurality of R ^12s may be the same or different.
Preferable embodiments of the linear polyether group having 4 to 30 carbon atoms include, for example, a group represented by the following formula (A2).

In the above formula (A2), R ²¹ represents a linear alkyl group, a linear alkenyl group, or a linear alkynyl group, and 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 an octyl group, a nonyl group, a decyl group, an undecylic group, a dodecyl group, a tridecylic group, and the like, and a tridecylic group is preferable.
In the above formula (A2), R ²² represents a linear alkylene group, a linear alkaneylene group, or a linear alkynylene group, and a linear alkylene group is preferable. As the linear alkylene group, a linear alkylene group having 1 to 2 carbon atoms is preferable, and an ethylene group is more preferable.
In the above formula (A2), p represents an integer of 1 to 10 and is preferably 3 to 7.
In the above formula (A2), * indicates a bonding position.

In the above formula (A1), R ¹³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
In the above formula (A1), R ¹⁴ represents an alkylene group having 1 to 30 carbon atoms, of which an alkylene group having 1 to 12 carbon atoms is preferable, and an alkylene group having 1 to 5 carbon atoms is more preferable. Specific examples of the alkylene group having 1 to 5 carbon atoms include a methylene group, an ethylene group and a propylene group.

In the above equation (A1), l represents an integer of 1 to 3, m represents an integer of 0 to 2, n represents an integer of 0 to 1, and l, m and n represent the relational expression of l + m + n = 3. Fulfill.
In the present invention, m in the above formula (A1) is preferably 0, and l is more preferably 3 for the reason that the silica dispersibility is further improved.

In the present invention, the content of the mercapto-based silane coupling agent is 1 to 20% by mass, preferably 4 to 20% by mass, and 5 to 15% by mass with respect to the content of the silica. It is more preferable to have.
The content of the mercapto-based silane coupling agent is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, and 3 to 20 parts by mass with respect to 100 parts by mass of the diene-based rubber. It is more preferably 15 parts by mass.

[Liquid polybutadiene rubber]
The liquid polybutadiene rubber contained in the rubber composition of the present invention has a vinyl bond content of 80% by mass or more on average, and vinyl bonds of each liquid polybutadiene rubber when two or more kinds of liquid polybutadiene rubbers are contained. It is a butadiene polymer having a content of 60% by mass or more.
Here, the vinyl bond content represents the ratio (% by mass) of the repeating unit having a vinyl bond derived from butadiene with respect to the entire butadiene polymer.
Further, the average value of the vinyl bond content is preferably 90% by mass or more because the silica dispersibility is better. Further, the upper limit is preferably 95% by mass or less for the same reason.

The weight average molecular weight (Mw) of the liquid polybutadiene rubber is 1000 to 18000, preferably 1000 to 10000, and more preferably 1000 to 5000. The method for measuring the molecular weight is as described above.

In the present invention, the content of the liquid polybutadiene rubber is 1 to 20 parts by mass, preferably 2 to 15 parts by mass, and 5 to 10 parts by mass with respect to 100 parts by mass of the diene rubber. Is more preferable.

[Guanidine-based vulcanization accelerator]
The guanidine-based vulcanization accelerator contained in the rubber composition of the present invention is not particularly limited, and specific examples thereof include diphenylguanidine (DPG), 1,3-di-o-tolylguanidine (DOTG), and 1-o. -Trirubiguanide (OTBG) and the like can be mentioned, and these may be used alone or in combination of two or more.

In the present invention, the content of the guanidine-based vulture accelerator is more than 0.6 parts by mass and less than 2.5 parts by mass with respect to 100 parts by mass of the diene-based rubber, 0.7. It is preferably ~ 2.4 parts by mass, more preferably 0.8 to 2.0 parts by mass, and even more preferably 0.9 to 1.8 parts by mass.
The content of the guanidine-based vulcanization accelerator is 3 to 60% by mass, preferably 5% by mass or more and less than 50% by mass, preferably 5 to 30% by mass, based on the mass of the liquid polybutadiene rubber. % Is more preferable.
When the content of the guanidine-based vulcanization accelerator is in the above-mentioned range, an appropriate vulcanization rate is maintained and the silica dispersibility is improved as described above.

〔Carbon black〕
The rubber composition of the present invention preferably contains carbon black for the reason of improving the reinforcing performance of the tire.
Specific examples of the carbon black include furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF, and these may be used alone or in combination of two or more. May be.
_{Further, the carbon black preferably has a nitrogen adsorption specific surface area (N 2} SA) of 10 to 300 m ² / g from the viewpoint of processability when the rubber composition is mixed and the reinforcing property of the pneumatic tire. More preferably, it is 20 to ^{200 m 2 / g.}
Here, N ₂ SA is a value obtained by measuring the amount of nitrogen adsorbed on the surface of carbon black according to JIS K 6217-2: 2001 "Part 2: How to determine the specific surface area-Nitrogen adsorption method-Single point method". ..

In the present invention, when the carbon black is contained, the content is preferably 40 to 130 parts by mass, more preferably 50 to 100 parts by mass with respect to 100 parts by mass of the diene rubber.

[Other ingredients]
In addition to the above-mentioned components, the rubber composition of the present invention contains fillers such as calcium carbonate; dinitrosopentamethylenetetraamine (DPT), azodicarboxylicamide (ADCA), dinitrosopentastyrenetetramine, oxybisbenzenesulfonylhydrazide (OBSH). ), Vulcanization sulphonyl hydrazide derivative, ammonium bicarbonate that generates carbon dioxide, ammonium carbonate, sodium bicarbonate, toluenesulfonyl hydrazide that generates nitrogen, P-toluenesulfonyl semicarbadide, nitrosoxysulfonylazo compound, N, N'-dimethyl-N , N'-dinitrosophthalamide, P, P'-oxybibis (benzenesulfonyl semicarbazide) and other chemical foaming agents; vulcanizing agents such as sulfur; Other vulcanization accelerators; vulcanization accelerators such as zinc oxide and stearic acid; waxes; aroma oils; antiaging agents; plasticizers; Additives can be added.
The blending amount of these additives can be a conventional general blending amount as long as it does not contradict the object of the present invention. For example, for 100 parts by mass of diene rubber, 0.5 to 5 parts by mass of sulfur, 0.1 to 5 parts by mass of vulcanization accelerator, 0.1 to 10 parts by mass of vulcanization accelerator aid, and aging. The inhibitor may be blended in an amount of 0.5 to 5 parts by mass, wax may be blended in an amount of 1 to 10 parts by mass, and aroma oil may be blended in an amount of 5 to 30 parts by mass.

[Manufacturing method of rubber composition for tires]
The method for producing the rubber composition for a tire of the present invention is not particularly limited, and for example, a method of kneading each of the above-mentioned components using a known method or device (for example, a Banbury mixer, a kneader, a roll, etc.) and the like. Can be mentioned.
Further, the rubber composition for a tire of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[Pneumatic tires]
The pneumatic tire of the present invention is a pneumatic tire in which the above-mentioned rubber composition for a tire of the present invention is arranged on a tire tread (cap tread).
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 tire of the present invention is not limited to the aspect 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 tread portion composed of the rubber composition for a tire of the present invention.
Further, 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 portions of the carcass layer 4 are located around the bead core 5 and the bead filler 6 from the inside to the outside of the tire. It is folded back and rolled up.
Further, in the tire tread 3, a belt layer 7 is arranged on the outside of the carcass layer 4 over one circumference of the tire.
Further, in the bead portion 1, the 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, an inert gas such as nitrogen, argon or helium can be used in addition to normal or air having an adjusted oxygen partial pressure.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

[Standard Examples 1 to 3, Examples 1 to 8 and Comparative Examples 1 to 8]
The components shown in Table 1 below were blended in 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 are heated to around 150 ° C. using a 1.7 liter sealed Banbury mixer, and then for 5 minutes. After mixing, it was released and cooled to room temperature to obtain a masterbatch.
Then, using the above Banbury mixer, sulfur and a vulcanization accelerator were mixed with the obtained masterbatch to obtain a rubber composition for a tire.

<Vulcanization time (T95)>
For the prepared rubber composition for tires (unvulcanized), a rotary vulcanization tester was used as a leometer in accordance with JIS 6300-2: 2001 "How to determine vulcanization characteristics by vibration type vulcanization tester". At a test temperature of 160 ° C., a vulcanization curve was measured with the obtained torque on the vertical axis and the vulcanization time on the horizontal axis. In the obtained vulcanization curve, the vulcanization time required from the start of vulcanization to the maximum torque value of MH was defined as tk (max). According to JIS K6300-2, the difference between the minimum torque value ML and the maximum torque value MH is set as ME (ME = MH-ML), and the vulcanization time from the start of the test until the torque reaches ML + 95% ME is set. T95 (minutes) was used, and this was used as the vulcanization time.
The results are shown in Table 1 below. Except for Examples 7 and 8, the results are represented by an index having the value of Standard Example 1 as 100, Example 7 being represented by an index having the value of Standard Example 2 as 100, and Example 8 being represented by an index having the value of Standard Example 3 as 100. It was expressed as an exponent with the value of 100 as 100. The smaller this index is, the faster the vulcanization rate is, and the larger this index is, the slower the vulcanization rate is. However, based on the specific vulcanization time of Standard Example 1, the index is in the range of 90 to 110. It can be evaluated that it has an appropriate vulcanization rate.

<Moony viscosity>
For the prepared rubber composition for tires (unvulcanized), according to JIS K6300-1: 2013, an L-shaped rotor was used under the conditions of preheating time of 1 minute, rotor rotation time of 5 minutes, and test temperature of 100 ° C. Mooney viscosity was measured.
The results are shown in Table 1 below. The results are represented by an index with Standard Example 1 as 100, Except for Examples 7 and 8, an index with a value of Standard Example 2 as 100, and Example 8 is a value of Standard Example 3. Was expressed as an index with 100 as 100. The smaller the index, the smaller the viscosity and the better the workability. However, considering the viscosity of Standard Example 1, if the index is 125 or less, it can be evaluated that the workability is excellent.

<Pain effect>
The prepared rubber composition for tires (unsulfurized) is vulnerable to strain shear modulus at 170 ° C. for 10 minutes using a strain shear stress measuring machine (RPA2000, manufactured by α-Technology), and then has a strain shear modulus of 0.28%. The coefficient G'and the strain-shear elastic modulus G'with a strain of 30.0% were measured, and the difference G'0.28 (MPa) -G'30.0 (MPa) was calculated as the Pain effect.
The results are shown in Table 1 below. Except for Examples 7 and 8, the results are represented by an index with the Pain effect of Standard Example 1 as 100, Example 7 with an index with the value of Standard Example 2 as 100, and Example 8 with Standard Example. It was expressed as an exponent with the value of 3 as 100. The smaller the index, the smaller the Pain effect and the better the dispersibility of silica.

The following components were used as the components in Table 1 above.
SBR1: E581 (oil-extended product (containing 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR. The net SBR in SBR is 72.7% by mass), styrene content: 37% by mass, vinyl bond. Amount: 42.5% by mass, weight average molecular weight: 126000, manufactured by Asahi Kasei Co., Ltd.)
・ BR1: Nipol BR1220 (manufactured by Zeon Corporation)
Silica 1: Zeosil 1165MP (CTAB adsorption specific surface area = 159m ² / g, manufactured by Rhodia)
-Silica 2: Zeosil Premium 200MP (CTAB adsorption specific surface area = 200m ² / g, manufactured by Rhodia)
-Silica 3: KS30-SC (CTAB adsorption specific surface area = 300 m ² / g, manufactured by Tokuyama Corporation)
・ Stearic acid: Beaded stearic acid YR (manufactured by NOF CORPORATION)

-Liquid BR1: Polybutadiene (B-3000, vinyl bond content: 90% by mass or more, weight average molecular weight: 3000, manufactured by Nippon Soda Corporation)
-Liquid BR2: Polybutadiene (B-2000, vinyl bond content: 90% by mass or more, weight average molecular weight: 2100, manufactured by Nippon Soda Corporation)
-Liquid BR3: Hydroxyl-terminated polybutadiene at both ends (G-3000, vinyl bond content: 90% by mass or more, weight average molecular weight: 3000, manufactured by Nippon Soda Corporation)
Liquid BR4: Butadiene homopolymer (Ricon 150, vinyl bond content: 70% by mass, weight average molecular weight: 6000, manufactured by CRAY VALLEY)
-Liquid SBR1: SBR (Ricon 100, vinyl bond content: 70% by mass, weight average molecular weight: 7000, manufactured by CRAY VALLEY)

-Silane coupling agent 1: Si69 (manufactured by Evonik Degussa)
-Silane coupling agent 2: Si263 (3-mercaptopropyltriethoxysilane)
-Silane coupling agent 3: Si363 represented by the following formula (manufactured by Evonik Degussa)

・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
-Anti-aging agent: Amine-based anti-aging agent (Santflex 6PPD, manufactured by Flexis)
・ Process oil: Extract No. 4 S (manufactured by Showa Shell Sekiyu Co., Ltd.)
・ Sulfur: Fine sulfur powder containing Jinhua Ink oil (manufactured by Tsurumi Chemical Industry Co., Ltd.)
-Guanidine-based vulcanization accelerator: DPG (Noxeller D, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
-Sulfur amide-based vulcanization accelerator: CBS (Noxeller CZ-G, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
-Thiazole-based vulcanization rate: MBTS (Noxeller MP, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)

From the results shown in Table 1, it was found that when the mercapto-based silane coupling agent and the guanidine-based vulcanization accelerator were not blended, the silica dispersibility was inferior even if the liquid BR satisfying the predetermined vinyl bond content was blended. (Comparative example 1).
Further, it was found that when the liquid BR and the guanidine-based vulcanization accelerator were not blended, the vulcanization rate was slowed down and the processability was inferior even if the mercapto-based silane coupling agent was blended (Comparative Example 2). ).
Further, it was found that the silica dispersibility was inferior when a liquid BR that did not satisfy the predetermined vinyl bond content was blended (Comparative Example 3).
It was also found that when a liquid SBR that does not satisfy the predetermined vinyl bond content was blended, the vulcanization rate was slowed down and the silica dispersibility was also inferior (Comparative Example 4).
Further, it was found that when a thiazole-based vulcanization accelerator was added instead of the guanidine-based vulcanization accelerator, the silica dispersibility was inferior (Comparative Example 5).
Further, when the blending amount of the guanidine-based vulcanization accelerator is 0.6 parts by mass or less or 2.5 parts by mass or more with respect to 100 parts by mass of the diene-based rubber, the vulcanization rate Was found to be slower and the silica dispersibility was also inferior (Comparative Examples 6 to 8).

On the other hand, when a mercapto-based silane coupling agent, a liquid polybutadiene rubber satisfying a predetermined vinyl bond content, and a predetermined amount of a guanidine-based vulcanization accelerator are blended, an appropriate vulcanization rate is maintained and silica is dispersed. It was found that the property was excellent and the workability was also good (Examples 1 to 8).

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 (6)

It contains a diene-based rubber, silica, a mercapto-based silane coupling agent, a liquid polybutadiene rubber, and a guanidine-based vulcanization accelerator.
The silica content is 30 to 200 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the mercapto-based silane coupling agent is 1 to 20% by mass with respect to the content of the silica.
The 1,2 bond (vinyl bond) content of the liquid polybutadiene rubber is 80% by mass or more on average, and the 1,2 bond of each liquid polybutadiene rubber when two or more kinds of liquid polybutadiene rubber is contained. (Vinyl bond) content is 60% by mass or more,
The liquid polybutadiene rubber has a weight average molecular weight of 1000 to 18000.
However, the liquid polybutadiene rubber does not have a sulfur atom and does not have a sulfur atom.
The content of the liquid polybutadiene rubber is 1 to 20 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the guanidine-based vulcanization accelerator is more than 0.6 parts by mass and less than 2.5 parts by mass with respect to 100 parts by mass of the diene-based rubber, and 3 with respect to the mass of the liquid polybutadiene rubber. A rubber composition for tires, which is ~ 60% by mass. The rubber composition for a tire according to claim 1, wherein the liquid polybutadiene rubber has a weight average molecular weight of 1000 to 10000. The rubber composition for a tire according to claim 1 or 2, wherein the silica has a CTAB adsorption specific surface area of 145 to 300 m ^{2 / g.} The rubber composition for a tire according to any one of claims 1 to 3, wherein the mercapto-based silane coupling agent is a compound represented by the following formula (A1).

Here, in the formula (A1), R ¹¹ represents an alkoxy group having 1 to 8 carbon atoms, R ¹² represents a linear polyether group having 4 to 30 ^{carbon atoms, and R 13} represents a hydrogen atom or carbon. The number 1 to 8 represents an alkyl group, and R ¹⁴ represents an alkylene group having 1 to 30 carbon atoms. l represents an integer of 1 to 3, m represents an integer of 0 to 2, n represents an integer of 0 to 1, and l, m and n satisfy the relational expression of l + m + n = 3. a plurality of R ¹¹ when l is 2 or 3, each may be the same or different and a plurality of R ¹² when m is 2, even if each be the same or different good. The rubber composition for a tire according to claim 4, wherein the mercapto-based silane coupling agent is a compound in which m in the following formula (A1) is represented by 0. A pneumatic tire in which the rubber composition for a tire according to any one of claims 1 to 5 is arranged on a cap tread.

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