JP3094176B2 - Rubber composition suitable for tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition suitable for tires and having particularly excellent rolling resistance and wet grip and ice grip performance.

[0002]

2. Description of the Related Art In recent years, in the field of automobiles, it has become important issues to improve safety such as running stability and brake braking performance and to reduce fuel consumption from the viewpoint of resource saving and energy saving. As a result, the demand for rubber materials for tires has been changed to be more stringent.

The following are mentioned as requirements for such rubber materials for tires. (1) Excellent breaking characteristics such as abrasion resistance; (2) Low rolling resistance in response to low fuel consumption; (3) Brake braking performance on wet roads (wet grip) and snow or icing Excellent brake braking performance on the road surface (ice grip performance). Among them, the rolling resistance of (2) and the wet grip property and ice grip property of (3) are said to be physical properties resulting from hysteresis loss of rubber.

That is, the rolling resistance corresponds to energy dissipation when rubber undergoes relatively low-frequency periodic deformation during tire running, and to reduce this, it is necessary to reduce the hysteresis loss of the rubber composition. There is. On the other hand, wet grip performance and ice grip performance correspond to energy dissipation when receiving high-frequency periodic deformation generated between the tire tread and fine unevenness of the road surface during braking, and to improve them, The hysteresis loss of the rubber composition must be increased. Therefore,
The above two physical properties were considered to be contradictory.

However, the frequency at which the tire undergoes periodic deformation is greatly different between running and braking. When the deformation frequency is converted into temperature according to the Williams-Randel-Ferry temperature conversion rule, the rolling resistance is 60 ° C. Nearby
It is known that good correlation is obtained between tan δ (loss coefficient: a measure of hysteresis loss), wet grip property and tan δ near 0 ° C, and ice grip property with tan δ near -20 ° C. Therefore, low rolling resistance,
In order to simultaneously satisfy the high wet grip property and the high ice grip property, tan δ at a low temperature around 0 ° C. and −20 ° C. is increased, and tan δ at a high temperature around 60 ° C.
It can be seen that it is only necessary to reduce.

Conventionally, to meet such demands for tread rubber materials, for example, a method using a polybutadiene rubber or a styrene / butadiene copolymer rubber having a high vinyl bond content in a butadiene portion obtained by solution polymerization as a base rubber, a specific glass Method of blending various kinds of rubbers having a transition temperature, polybutadiene rubber or styrene / butadiene copolymer rubber having a tin-carbon bond in a molecular chain, polybutadiene rubber or styrene / butadiene having amino group-containing benzophenones added to a polymer chain A method of using a copolymer rubber as a base rubber, a method of blending a modified carbon black, and a method of blending a modifier have been proposed.

Among these methods, the method of adding a modifier has attracted attention because it can easily impart various physical properties to rubber and can be applied to natural rubber as compared with other methods. As such a modifier, dinitrodiamines represented by the following general formula (II) are proposed in JP-A-63-23942 and JP-A-1-247437.

[0008]

Embedded image

Wherein X is a divalent linear aliphatic group, a cycloaliphatic group or an aromatic group, which may contain halogen or oxygen; R ¹ is a hydrogen atom, a chain An aliphatic group, a cycloaliphatic group or an aromatic group, X and R
^When both ¹ are chain aliphatic groups, the nitrogen atoms may be further linked to each other via R ¹ ; R ² and R ³ are each independently a hydrogen atom or a group having 1 to 1 carbon atoms.
And R ² and R ³ may combine to form a ring . )

[0010]

These dinitrodiamines are known as modifiers capable of improving the low-temperature properties and heat build-up of rubber for tires and reducing the rolling resistance. Therefore, these dinitrodiamines have been applied to rubber for tires, but in response to demands for further improving low-temperature characteristics such as ice grips and wet grips and increasing fuel efficiency, which have become increasingly severe in recent years. Further improvement was desired.

Under these circumstances, the present inventors have conducted intensive studies in order to develop a rubber composition in which the effects of improving the physical properties of the above-mentioned dinitrodiamines are more effectively exhibited, and which have a good balance in low-temperature characteristics and rolling resistance. As a result,
The present invention has been completed.

[0012]

The present inventors have introduced a specific benzophenone compound into the polymerized terminal of a specific modified styrene / butadiene copolymer, that is, a copolymer obtained by copolymerizing styrene and butadiene. By using a modified styrene / butadiene copolymer having a ratio of styrene unit to butadiene unit within a certain range and having a specific microstructure and Mooney viscosity, the modified styrene / butadiene copolymer is represented by the general formula (II). It has been found that the effect of adding dinitrodiamines is more effectively exerted, and a rubber composition having excellent low-temperature properties and rolling resistance can be obtained.

That is, the present invention provides the following (A):
An object of the present invention is to provide a rubber composition containing the components (B) and (C). (A) General formula (I) is added to the polymerization end of a copolymer obtained by copolymerizing styrene and butadiene.

[0014]

Embedded image

[0015] (wherein, Q is represented. Methyl or ethyl) are introduced a benzophenone compound represented by the (1) styrene unit 3-30 wt%, the butadiene units is 97 to 70 wt%, (2) The vinyl bond amount of the butadiene portion is 25% by weight or more, and (3) the Mooney viscosity represented by ML _{1 + 4} (100 ° C.) is 3
A raw rubber mainly composed of a modified styrene / butadiene copolymer of 0 to 80, (B) carbon black, and (C) the raw rubber 1
0.1 to 10 parts by weight of N, N'-bis per 100 parts by weight
(2-methyl-2-nitropropyl) -1,6-diamido
Nohexane .

In the present invention, the raw material rubber is mainly composed of a copolymer obtained by copolymerizing styrene and butadiene, into which a benzophenone compound represented by the above general formula (I) is introduced at the polymerization terminal. (1) styrene unit is 3 to 30% by weight, butadiene unit is 97 to 70% by weight, (2) butadiene portion has a vinyl bond amount of 25% by weight or more, and (3) ML _{1 + 4} (100 ° C. ) Is 3
0-80 modified styrene / butadiene copolymer.

Here, when the styrene unit is less than 3% by weight, the breaking strength is poor, and when it exceeds 30% by weight, the rolling resistance is not sufficiently improved. On the other hand, when the vinyl bond amount of the butadiene portion is less than 25% by weight, the wet grip performance is inferior, which is not preferable. Furthermore, ML _{1 + 4} (100 ° C)
If the Mooney viscosity represented by the formula is less than 30, the breaking strength will be poor, while if the Mooney viscosity exceeds 80, problems will arise in workability, which is not preferred.

Such a modified styrene / butadiene copolymer can be prepared by a known method, for example, as described in JP-A-59-197443,
It can be produced by the methods described in JP-A-60-8341 and JP-A-60-8342. That is,
In a hydrocarbon solvent, styrene and butadiene are copolymerized by a solution polymerization method (a so-called living polymerization method) using an organic lithium compound as a polymerization initiator, and the obtained copolymer is subjected to a benzophenone compound represented by the general formula (I). Can be produced by reacting The polymerization temperature may vary depending on the target microstructure, but is preferably about 0 to 150 ° C from the viewpoint of economy and side reactions. The vinyl bond amount of the butadiene portion can be adjusted by using a Lewis base such as an ether or a tertiary amine and changing the type and amount of use, or by appropriately selecting the polymerization temperature and the like.

The amount of the benzophenone compound represented by the general formula (I) used in the modification reaction is preferably about 0.2 to 1.5 equivalents per 1 equivalent of the polymerized lithium atom.
In addition, from the viewpoint of fracture characteristics and rolling resistance performance, before reacting the benzophenone compound represented by the general formula (I), a part of the polymerization terminal is reacted with a coupling compound such as tin tetrachloride, It is also effective to include a branched copolymer. When such a branched copolymer is formed, the amount of the coupling agent such as tin tetrachloride needs to be such that the effect of the benzophenone modification is not impaired. 0.01 ~
Used at a rate of about 0.2 equivalent.

The raw rubber used in the present invention is mainly composed of the modified styrene / butadiene copolymer as described above. This modified copolymer can be used alone, or the modified copolymer can be used. It is also possible to use one containing at least 50% by weight of the coalesced substance and blending another diene rubber in the range of up to 50% by weight. Suitable diene rubbers for blending include natural rubber, isoprene rubber, unmodified styrene / butadiene copolymer rubber, butadiene rubber, and the like. When these diene rubbers are blended, it is preferable to blend them in an amount of 5% by weight or more based on the total weight of the raw rubber. Therefore, the preferred blending ratio in the blend system is 50 to 50%.
95% by weight and 50 to 5% by weight of another diene rubber.

As the carbon black used in the present invention, various carbon blacks conventionally used having different reinforcing properties, for example, SAF, ISAF, HAF, F
Examples include EF, SRF, GPF, and MT, and the type is not particularly limited. Among these, carbon black having a nitrogen adsorption specific surface area of about 30 to 130 m ² / g,
For example, it is preferable to use ISAF, HAF, FEF, or the like. Although the amount of carbon black added is not particularly limited, it is usually preferably about 10 to 150 parts by weight, more preferably about 10 to 80 parts by weight, per 100 parts by weight of rubber.

The N, N'-bis (2-methyl) used in the present invention
Ru-2-nitropropyl) -1,6-diaminohexane
Is Ru compound der represented by the chemical formula below.

[0023]

Embedded image In the above chemical formula , -Z represents the following group.

[0024]

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N, N′-bis (2-methyl-2-nitro
When propyl) -1,6-diaminohexane is compounded with the rubber, the form is arbitrary, and each compound alone,
It may take the form of a mixture of a plurality of compounds, a mixture with a carrier such as clay that does not affect the physical properties of the rubber, and a mixture with various compounding agents described below. Therefore, any of these forms can be added to the raw rubber mainly composed of the modified copolymer rubber.

N, N′-bis (2-methyl-2-nitro
Propyl) -1,6-diaminohexane is used in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the raw rubber,
If the amount is too small, the effect is insufficient, and if it is too large, it becomes uneconomical. N, N'-bis (2-methyl-2
-Nitropropyl) -1,6-diaminohexane is preferably used in an amount of 0.2 to 3 parts by weight per 100 parts by weight of the raw rubber.

In the present invention, various other compounding agents commonly used in the rubber industry can be used according to the purpose. For example, chloranil, 1,1-bis (t
-Butylperoxy) -3,3,5-trimethylcyclohexane, reaction aids such as nucleus-substituted phenol sulfide resins, and various additives such as thiazoles, thiurams, dithioacids, and guanidines. Sulfuric accelerator, phthalic anhydride, scorch retarder such as N- (cyclohexylthio) phthalimide, other sulfur, filler, stearic acid, peptizer, zinc white, process oil, processing aid, antioxidant, ozone deterioration Inhibitors, waxes and the like are appropriately used. The types and amounts of these compounding agents can be selected as necessary, and are not particularly limited in the present invention.

In general, when compounding a compound with natural rubber or synthetic rubber, the compounding is basically performed in two steps. That is, carbon black and other fillers, process oil, stearic acid, etc. have a rubber temperature of 120 to
The vulcanization accelerator and the vulcanizing agent are added in a relatively high temperature first step of about 220 ° C, and the rubber temperature is about 40 to 120 ° C in a relatively low temperature second step. According to the present invention, N, N '
-Bis (2-methyl-2-nitropropyl) -1,6-
When compounding diaminohexane with the modified copolymer rubber, the compounding time is not particularly limited, and may be compounded in any of the first step and the second step, and may be further compounded in another step. Good. However, preferably, it is added in the first step in which carbon black or the like is blended, and the blending temperature at that time is preferably about 140 to 200 ° C., since a higher temperature has a greater effect of improving rubber physical properties.
More preferably, the temperature is 170 ° C. or higher.

The rubber composition of the present invention is preferably used, for example, as various members of a tire, particularly as a tread portion. For example, the rubber composition is applied to a tread portion or other members, and molded by a method usually used in the tire industry to obtain a tire.

[0030]

The present invention will be described in more detail with reference to the following examples, which are preferred embodiments of the present invention and do not limit the scope of the present invention. Note that, in the following examples,% and part representing the amount are:
Unless otherwise specified, it means% by weight and part by weight, respectively.

The N, N'-bis (2-methyl
Ru-2-nitropropyl) -1,6-diaminohexane
Is indicated by the following symbols.

[0032]

TABLE 1 A: N, N'-bis (2-methyl-2-nitropropyl) -1,6-diaminohexane

In the following examples, rubber physical properties were tested by the following methods. Mooney viscosity The temperature of raw material rubber is 100 in accordance with JIS K-6300.
Measured in ° C. Mooney scorch property For the rubber compound before vulcanization, in accordance with JIS K-6300,
The time required to rise 5 points above the minimum value at 135 ° C. was defined as the scorch time. Tanδ (Loss coefficient) Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho, under the conditions of 10% static strain, 10Hz frequency, and 0.25% dynamic strain amplitude,
The values at 60 ° C, 0 ° C and -20 ° C were measured. 6
The tan δ at 0 ° C. corresponds to the rolling resistance. The smaller the value, the greater the effect of lowering the rolling resistance.
The tan δ at ℃ corresponds to the wet grip property, and the tan δ at −20 ° C. corresponds to the ice grip property,
The larger the value, the greater the effect of improving grip. Conforms to tensile stress _{(M 300) JIS K-6301} , measured at dumbbell-shaped test piece.

Synthesis Example of Modified Styrene / Butadiene Copolymer Rubber Using a stirrer and a reactor equipped with a jacket, under a nitrogen atmosphere, cyclohexane, 1,3-butadiene, tetrahydrofuran and styrene were charged, and the temperature was adjusted to 30 ° C. -Butyl lithium is added and the polymerization is started.
After the temperature was raised to 70 ° C, polymerization was carried out for 2 hours, and the polymerization conversion rate was 10
After reaching 0%, a small amount of tin tetrachloride was added.
Perform the coupling reaction for 5 minutes. Thereafter, 4,4'-bis (diethylamino) benzophenone was added, and the mixture was added at 60 ° C for 3 hours.
Perform denaturation reaction for 0 minutes. 2,6 is added to the obtained copolymer solution.
After adding di-t-butyl-p-cresol, the solvent was removed by steam stripping.
To obtain a modified copolymer. The styrene content and vinyl bond amount of the obtained copolymer were measured using an infrared spectrophotometer. The following modified styrene / butadiene copolymer rubber was produced by varying 1,3-butadiene, styrene, tetrahydrofuran, n-butyllithium, tin tetrachloride and a benzophenone compound in accordance with the above operation.

SBR-1: Styrene content 24% Vinyl bond amount 34% Mooney viscosity 45ML _{1 + 4} (100 ° C.) SBR-2: Styrene content 15% Vinyl bond amount 31% Mooney viscosity 51ML _{1 + 4} (100 ° C.)

Embodiment 1

[0037]

<Table 2><Blendedformulation> Modified styrene / butadiene rubber (SBR-1 or SBR-2) 100 parts ISAF black (N220) 45 parts Stearic acid 3 parts Zinc zinc 2 parts Antioxidant 2 parts (N-phenyl-) N'-1,3-dimethylbutyl-p-phenylenediamine) Vulcanization accelerator 1 part (N-cyclohexyl-2-benzothiazylsulfenamide) Io 2 parts Dinitrodiamine Tables 3 and 4 described ( N, N'- bis (2- methyl- 2- nitropropyl ) -1,6 -diaminohexane )

A Banbury mixer manufactured by Toyo Seiki Co., Ltd.
Using a 50 ml Labo Plastmill, oil bath temperature 175
At room temperature, dinitrodiamines (N, N'-bis (2-methyl) were added to styrene / butadiene rubber based on the above formulation.
-2-nitropropyl) -1,6-diaminohexa
) , Carbon black, stearic acid and zinc white were charged and kneaded at a mixer rotation speed of 50 rpm for 15 minutes. The rubber temperature at this time was 165 to 193 ° C.

Next, the composition was transferred to an open mill,
At a temperature of 0 to 70 ° C, the antioxidant, the vulcanization accelerator and the sulfur shown in the above formulation were added and kneaded. A part of the kneaded sample was subjected to the Mooney scorch test, and the rest of the kneaded sample was subjected to a vulcanizing press to obtain 17 parts.
After vulcanization at 0 ° C. for 25 minutes, the tan δ and the tensile stress were measured. The results of these tests are shown in Tables 3 and 4 together with the variable values of the formulation.

[0040]

[Table 3]

[0041]

[Table 4]

Embodiment 2

[0043]

<Compounding formula> Modified styrene / butadiene rubber (SBR-1) 70 parts Natural rubber (RSS # 1) or 30 parts Butadiene rubber (BR01: manufactured by Nippon Synthetic Rubber Co., Ltd.) HAF black (N330) 50 parts Stearic acid 2 parts Zinc zinc 3 parts Antioxidant 2 parts (N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine) Vulcanization accelerator 1 part (N-cyclohexyl-2-benzothiazyl) Sulfenamide) Io 2 parts Dinitrodiamine Table 6 (N, N'- bis (2- methyl- 2- nitropropyl ) -1,6 -diaminohexane )

The same experiment as in Example 1 was carried out on the basis of the above-mentioned formulation in which the raw rubber was a blend of modified styrene / butadiene rubber and natural rubber or butadiene rubber. The experimental results are shown in Table 6 together with the variable values of the formulation.

[0045]

[Table 6]

[0046]

The tire employing the rubber composition of the present invention has low rolling resistance and excellent brake braking performance on wet road surfaces, snowy and icy road surfaces. That is, in accordance with the present invention, certain styrene / butadiene rubbers have N, N'-bis (2-methyl-2-nitroprop
(1) By mixing -1,6-diaminohexane , tan δ around 60 ° C. corresponding to rolling resistance is reduced, and around -20 ° C. and around 0 ° C. corresponding to ice grip property and wet grip property. tanδ can be increased. In addition, N, N'-bis
(2-methyl-2-nitropropyl) -1,6-diamido
By blending nohexane , the mechanical strength can be improved. Therefore, when such a rubber composition is applied to a tire member, for example, a tread portion, improvement in economy due to low fuel consumption of a vehicle is expected, and improvement in brake braking performance on wet road surfaces and on snow and icy road surfaces. Is expected to improve safety.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Yago 3-1-198 Kasuganaka, Konohana-ku, Osaka-shi Within Sumitomo Chemical Co., Ltd. (72) Inventor Tsuki Wakatsuki 5-1, Anesaki Beach, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd. (72) Inventor Kouji Tsuji 5-1, Anesaki Beach, Ichihara City, Chiba Prefecture Sumitomo Chemical Co., Ltd. (56) References JP-A-63-150338 (JP, A) JP-A-63- 23942 (JP, A) JP-A 1-247437 (JP, A) JP-A 61-133245 (JP, A) JP-A 63-191844 (JP, A) JP-A 60-61304 (JP, A)

Claims (8)

(57) [Claims] (1) The polymerization terminal of a copolymer obtained by copolymerizing (A) styrene and butadiene has a compound represented by the general formula (I): (Wherein Q represents methyl or ethyl) . (1) Styrene units are 3 to 30% by weight, butadiene units are 97 to 70% by weight, (2) The butadiene moiety has a vinyl bond amount of 25% by weight or more, and (3) a Mooney viscosity represented by ML _{1 + 4} (100 ° C.) of 3
(B) carbon black, and (C) 0.1 to 10 parts by weight of N, N'-bis () per 100 parts by weight of the raw rubber, the raw material rubber being mainly composed of a modified styrene / butadiene copolymer of 0 to 80. A rubber composition comprising (2-methyl-2-nitropropyl) -1,6-diaminohexane. 2. The method according to claim 1, wherein the raw material rubber is substantially the modified styrene /
The rubber composition according to claim 1, comprising a butadiene copolymer. 3. The raw material rubber contains at least 50% by weight of the modified styrene / butadiene copolymer and other diene rubbers.
2. The rubber composition according to claim 1, comprising 0% by weight or less. 4. The rubber composition according to claim 3, wherein the raw material rubber is a blend of 50 to 95% by weight of the modified styrene / butadiene copolymer and 50 to 5% by weight of another diene rubber. 5. The rubber composition according to claim 3, wherein the other diene rubber is selected from natural rubber, isoprene rubber, unmodified styrene / butadiene copolymer rubber, and butadiene rubber. 6. The amount of the raw rubber 100
The rubber composition according to any one of claims 1 to 5, wherein the amount is 10 to 150 parts by weight per part by weight. 7. A tire produced from the rubber composition according to claim 1. 8. The tire according to claim 7, wherein said rubber composition is used in a tread portion.