JPH05112675A - Rubber composition suitable for tire - Google Patents

Abstract

PURPOSE:To provide a rubber composition having excellent rolling resistance and wet and ice grip performance suitable for use in tires. CONSTITUTION:The objective composition can be obtained by incorporating (A) 100 pts.wt. of a stock rubber predominant in a modified styrene/butadiene copolymer with its end incorporated with a benzophenone compound of formula I (Q is methyl or ethyl), made up of (1) 3-30wt.% of styrene units and (2) 97-70wt.% of butadiene units with >=25wt.% of the vinyl linkages in the butadiene portion and 30-80 in Mooney viscosity with (B) carbon black, and (C) 0.1-10 pts.wt. of a dinitrodiamine of formula II (X is divalent chain aliphatic group, etc.; R<1> is H, chain aliphatic group, etc.; R<2> and R<3> are each H or 1-12C alkyl).

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 an important issue to improve fuel efficiency from the viewpoint of resource saving and energy saving as well as improvement of safety such as running stability and braking performance. Along with this, the demand for rubber materials for tires has become more severe.

The following are mentioned as requirements for such a rubber material for tires. (1) Excellent fracture characteristics such as wear resistance, (2) Low rolling resistance in response to low fuel consumption, (3) Brake braking on wet road surface (wet grip) and snow or icing Excellent braking performance (ice grip) on the road. Of these, (2) rolling resistance and (3) wet grip property and ice grip property are said to be physical properties due to hysteresis loss of rubber.

That is, rolling resistance corresponds to energy dissipation when the rubber undergoes cyclic deformation at a relatively low frequency during tire running, and in order to reduce it, it is necessary to reduce hysteresis loss of the rubber composition. There is. On the other hand, the wet grip property and the ice grip property correspond to energy dissipation when undergoing high frequency cyclic deformation generated between the tire tread and the fine irregularities of the road surface during braking, and in order to improve them, The hysteresis loss of the rubber composition must be increased. Therefore,
The above two physical properties were considered to be in conflict with each other.

However, the frequency when the tire undergoes cyclic deformation greatly differs between running and braking, and when the deformation frequency is converted into temperature according to the Williams-Landel-Ferry temperature conversion rule, the rolling resistance is 60 ° C. Near
It is known that tan δ (loss coefficient: a measure of hysteresis loss), wet grip properties are well correlated with tan δ near 0 ° C, and ice grip properties are well correlated with tan δ near -20 ° C. Therefore, low rolling resistance,
In order to satisfy the high wet grip property and the high ice grip property at the same time, tan δ at a low temperature around 0 ° C and -20 ° C is increased, and tan δ at a high temperature around 60 ° C is increased.
It can be seen that it is sufficient to reduce δ.

Conventionally, in order to meet such requirements 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 the butadiene portion obtained by solution polymerization as a base rubber, a specific glass A method of blending various rubbers having a transition temperature, a polybutadiene rubber having a tin-carbon bond in a molecular chain or a styrene / butadiene copolymer rubber, a polybutadiene rubber having an amino group-containing benzophenone added to a polymer chain, or a styrene / butadiene rubber A method of using a copolymer rubber as a base rubber, a method of adding a modified carbon black, a method of adding a modifier, and the like have been proposed.

Among these methods, the method of adding a modifier is attracting attention because it can easily give various properties to rubber and can be applied to natural rubber as compared with other methods. As such a modifier, JP-A-63-23942
In Japanese Patent Laid-Open No. 1-247437 and Japanese Patent Laid-Open No. 1-247437, the following general formula (I
Dinitrodiamines represented by I) have been proposed.

[0008]

[Chemical 3]

(In the formula, X is a divalent chain aliphatic group, a cycloaliphatic group or an aromatic group, and the group may contain halogen or oxygen; R ¹ is a hydrogen atom or a chain group. An aliphatic group, a cycloaliphatic group or an aromatic group, wherein 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 carbon number of 1 to 1;
12 alkyl groups, R ² and R ³ may combine to form a ring)

[0010]

The dinitrodiamines are known as modifiers capable of improving the low temperature characteristics and heat buildup of rubber for tires and further reducing rolling resistance. Therefore, these dinitrodiamines are being applied to rubber for tires, but in response to the demand for further improvement of low temperature characteristics such as ice grip and wet grip and fuel efficiency reduction which have become increasingly severe in recent years. , Further improvement was desired.

From such a background, the inventors of the present invention have earnestly studied to develop a rubber composition in which the effect of improving the physical properties of the dinitrodiamines is more effectively exhibited, and which has 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 at the polymerization end of a specific modified styrene / butadiene copolymer, that is, a copolymer obtained by copolymerizing styrene and butadiene. A modified styrene / butadiene copolymer having the ratio of styrene units and butadiene units within a certain range, and having a specific microstructure and Mooney viscosity is used, and is represented by the general formula (II). It was found that the effect of adding dinitrodiamines is more effectively exhibited, and a rubber composition having excellent low temperature characteristics and rolling resistance can be obtained.

That is, the present invention provides the following (A),
The present invention provides a rubber composition containing each of the components (B) and (C). (A) at the polymer terminal of the copolymer obtained by copolymerizing styrene and butadiene,

[0014]

[Chemical 4]

(In the formula, Q represents methyl or ethyl)
The benzophenone compound represented by is introduced,
(1) The styrene unit is 3 to 30% by weight, the butadiene unit is 97 to 70% by weight, (2) the vinyl bond content of the butadiene portion is 25% by weight or more, and (3) ML.
Raw rubber mainly composed of a modified styrene / butadiene copolymer having a Mooney viscosity of 30 to 80 represented by _{1 + 4} (100 ° C.), (B) carbon black, and (C) per 100 parts by weight of the raw rubber 0.1 to 10 parts by weight of the dinitrodiamine represented by the general formula (II).

In the present invention, the main constituent of the raw material rubber is that in which the benzophenone compound represented by the above general formula (I) is introduced into the polymerization terminal of the copolymer obtained by copolymerizing styrene and butadiene. Therefore, (1) styrene unit is 3 to 30% by weight, and butadiene unit is 97 to 7
0% by weight, (2) vinyl bond content of butadiene part is 25
A modified styrene / butadiene copolymer having a Mooney viscosity of 30 to 80 represented by (3) ML _{1 + 4} (100 ° C.) by weight or more.

If the styrene unit is less than 3% by weight, the breaking strength is poor, and if it exceeds 30% by weight, the rolling resistance is not sufficiently improved. If the amount of vinyl bonds in the butadiene portion is less than 25% by weight, wet grip performance is deteriorated, which is not preferable. Furthermore, ML _{1 + 4} (100 ℃)
When the Mooney viscosity represented by is less than 30, the breaking strength is inferior, while when the Mooney viscosity exceeds 80, there is a problem in workability, which is not preferable.

Such a modified styrene / butadiene copolymer can be prepared by a known method, for example, JP-A-59-197443.
It can be produced by the methods described in JP-A-60-8341 and JP-A-60-8342. That is, styrene and butadiene are copolymerized by a solution polymerization method (so-called living polymerization method) using an organic lithium compound as a polymerization initiator in a hydrocarbon solvent, and the resulting copolymer is represented by the above general formula (I). It can be produced by reacting a benzophenone compound. The polymerization temperature may vary depending on the target microstructure, but from the viewpoint of economic efficiency and side reactions, it is preferably about 0 to 150 ° C. The vinyl bond amount of the butadiene portion can be adjusted by using a Lewis base such as ether or tertiary amine, changing the kind and the amount thereof, 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 relative to 1 equivalent of the polymerization terminal lithium atom. 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 terminals is reacted with a coupling compound such as tin tetrachloride, It is also effective to contain a branched copolymer. When forming such a branched copolymer, it is necessary to use a coupling agent such as tin tetrachloride in an amount that does not impair the effect of benzophenone modification. 0.0
It is used at a ratio of about 1 to 0.2 equivalent.

The raw material rubber in the present invention is mainly composed of the modified styrene / butadiene copolymer as described above, but the modified copolymer can be used alone or the modified copolymer is used. It is also possible to use a blend containing 50% by weight or more of the coalesce 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 5% by weight or more based on the total weight of the raw rubbers.
95% by weight and 50 to 5% by weight of other diene rubber.

As the carbon black used in the present invention, various carbon blacks having different reinforcing properties which have been conventionally used, for example, SAF, ISAF, HAF, F.
Examples thereof include EF, SRF, GPF, MT, and the type thereof 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. The amount of carbon black added is not particularly limited, but is usually preferably about 10 to 150 parts by weight per 100 parts by weight of rubber, and more preferably about 10 to 80 parts by weight per 100 parts by weight of rubber.

Specific examples of the dinitrodiamines of the general formula (II) used in the present invention include the following compounds. In the following examples, -Z represents the following group.

[0023]

[Chemical 5]

[0024]

[Chemical 6]

[0025]

[Chemical 7]

[0026]

[Chemical 8]

[0027]

[Chemical 9]

[0028]

[Chemical 10]

As described above, the linking group X in the general formula (II) is a divalent chain aliphatic group, a cycloaliphatic group or an aromatic group, and as in the 33rd and 34th examples, The group may contain halogen, and examples 40 to 43
As in the example, oxygen can be contained in the group. Among these, a compound in which X is a chain aliphatic group, especially a chain aliphatic group having 4 to 12 carbon atoms, particularly alkylene, is preferably used. Other preferable X includes an aromatic group such as phenylene and diphenylmethane (each of two benzene rings has a bond).

R ¹ in the general formula (II) is a hydrogen atom, a chain aliphatic group, a cycloaliphatic group or an aromatic group, and when both X and R ¹ are chain aliphatic groups. Is a case where nitrogen atoms are further linked via R ¹ as in the 23rd and 24th examples, and a ring, for example, a 6-membered ring such as a piperazine ring is formed by X, R ¹ and two nitrogen atoms. Those that are included are also included.

Further, R ² and R ³ in the general formula (II), which may be the same or different, are each a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. In addition, as in the above-mentioned 12th example, 13th example, 22nd example and 30th example, those in which R ² and R ³ are combined to form a ring, for example, a 6-membered ring, with a carbon atom to which they are bonded Included.

When such dinitrodiamines are compounded in the rubber, the form is arbitrary, and each compound alone, a mixture of a plurality of compounds, and a mixture with a carrier such as clay that does not affect the physical properties of rubber, Further, it may be in a form of being mixed with various compounding agents described later. Therefore, any of these forms can be added to the raw rubber mainly composed of the modified copolymer rubber.

The amount of the dinitrodiamines used is 0.1 to 10 parts by weight per 100 parts by weight of the raw rubber. If the amount is too small, the effect will be insufficient, and if it is too large, it will be uneconomical. The dinitrodiamines are preferably used in the range 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 also be used according to the purpose. For example, chloranil, 1,1-bis (t
-Butylperoxy) -3,3,5-trimethylcyclohexane, organic peroxides, reaction aids such as nuclear-substituted phenol sulfide resins, thiazoles, thiurams, dithio acids, and various additives such as guanidines. Sulfurization 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, etc. are used as appropriate. The types and amounts of these compounding agents can be selected as necessary and are not particularly limited in the present invention.

When compounding agents are generally compounded with natural rubber or synthetic rubber, the compounding is basically carried out in two steps. That is, carbon black and other fillers, process oils, stearic acid, etc., have rubber temperatures of 120-
It is added in the first step at a relatively high temperature of about 220 ° C, and the vulcanization accelerator and the vulcanizing agent are added in the second step at a relatively low temperature of about 40 to 120 ° C. When compounding the dinitrodiamines of the general formula (II) with the modified copolymer rubber according to the present invention, the compounding timing is not particularly limited, and may be compounded in any of the first step and the second step. , And may be compounded in another step. However, preferably, carbon black or the like is added in the first step, and the compounding temperature at that time is preferably 140 to 200 ° C., and more preferably 170 to 200 ° C., since the higher the temperature, the greater the effect of improving the rubber physical properties. C. or higher is more preferable.

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, this rubber composition can be applied to a tread portion or other member and molded by a method commonly used in the tire industry to obtain a tire.

[0037]

The present invention will be described in more detail with reference to the following examples, which are preferred specific examples of the present invention and do not limit the scope of the present invention. In addition, in the following examples,% and parts representing the amount are
Unless otherwise indicated, they mean% by weight and parts by weight, respectively.

The dinitrodiamines used in the examples are shown in the following table, and are indicated by the respective symbols below.

[0039]

[Table 1] A: N, N'-bis (2-methyl-2-nitropropyl) -1,6-diaminohexane B: N, N'-bis (2-methyl-2-nitropropyl) -1, 4-Diaminobutane C: N, N'-bis (2-methyl-2-nitropropyl) -1,12-diaminododecane D: N, N'-bis (2-methyl-2-nitropropyl) -1, 4-diaminobenzene

In the following examples, the rubber physical properties were tested by the following methods. For Mooney viscosity raw material rubber, a temperature of 100 according to JIS K-6300
It was measured at ° C. About Mooney scorch rubber compound before vulcanization, according to JIS K-6300,
The time required for the temperature to rise by 5 points from the minimum value at 135 ° C was defined as the scorch time. Tan δ (loss factor) Measured at 60 ℃, 0 ℃ and -20 ℃ under conditions of static strain 10%, frequency 10Hz, dynamic strain amplitude 0.25% using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho. did. The tan δ at 60 ° C corresponds to rolling resistance, and the smaller the value, the greater the rolling resistance lowering effect. On the other hand, tan δ at 0 ° C corresponds to wet grip, and tan δ at -20 ° C is Corresponding to ice grip performance, the larger the value, the greater the improvement effect of grip performance. Tensile stress (M ₃₀₀ ) Measured with a dumbbell-shaped test piece in accordance with JIS K-6301.

Example of Synthesis 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. -Butyllithium is added to start the polymerization.
After the temperature was raised to 70 ° C, polymerization was performed for 2 hours, and the polymerization conversion rate was 10
After reaching 0%, add a small amount of tin tetrachloride and add 1 at 70 ° C.
Perform the coupling reaction for 5 minutes. Then 4,4'-bis (diethylamino) benzophenone was added, and the mixture was mixed at 60 ° C for 3
Perform a denaturation reaction for 0 minutes. 2,6 in the obtained copolymer solution
After the addition of -di-t-butyl-p-cresol, the solvent was removed by steam stripping, and then 110 ° C.
A modified copolymer is obtained by drying with a hot roll of. The styrene content and vinyl bond content of the obtained copolymer were measured using an infrared spectrophotometer. According to the above operation, the 1,3-butadiene, styrene, tetrahydrofuran, n-butyllithium, tin tetrachloride and benzophenone compounds were varied to produce the modified styrene / butadiene copolymer rubber shown below.

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)

Example 1

[0044]

[Table 2] <Compound formulation> Modified styrene / butadiene rubber (SBR-1 or SBR-2) 100 parts ISAF black (N220) 45 parts Stearic acid 3 parts Lead zinc 2 parts Anti-aging agent 2 parts (N-phenyl- N'-1,3-dimethylbutyl-p-phenylenediamine) Vulcanization accelerator 1 part (N-cyclohexyl-2-benzothiazylsulfenamide) Iou 2 parts Dinitrodiamines Tables 3 and 4

2 made by Toyo Seiki as a Banbury mixer
Oil bath temperature 175 using 50ml Labo Plastomill
Dinitrodiamines, carbon black, stearic acid and zinc white were added to a styrene / butadiene rubber based on the above compounding recipe at a temperature of 50 ° C. and kneaded at a mixer rotation speed of 50 rpm for 15 minutes. The rubber temperature at this time is 165 to
It was 193 ° C.

The formulation was then transferred to an open mill, 6
At a temperature of 0 to 70 ° C., the antioxidant, vulcanization accelerator and sulfur shown in the above formulation were added and kneaded. A part of the sample after kneading was subjected to the Mooney scorch test, and the rest of the sample after kneading was subjected to a vulcanization press.
After vulcanization at 0 ° C. for 25 minutes, the tan δ and tensile stress were measured. The results of these tests are shown in Tables 3 and 4 together with the variable values of the formulation.

[0047]

[Table 3]

[0048]

[Table 4]

Example 2

[0050]

<Table 5> <Compound formulation> 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 Lead phosphite 3 parts Anti-aging agent 2 parts (N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine) Vulcanization accelerator 1 part (N-cyclohexyl-2-benzothiazyl Sulfenamide) Io 2 parts Dinitrodiamines Table 6

The same experiment as in Example 1 was carried out on the basis of the above compounding recipe in which the raw material rubber was a blend system 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.

[0052]

[Table 6]

[0053]

EFFECT OF THE INVENTION The tire using the rubber composition of the present invention has low rolling resistance and excellent braking performance on wet road surfaces and on snow and icy road surfaces. That is, according to the present invention, by blending dinitrodiamines with a specific styrene / butadiene rubber, tan δ near 60 ° C. corresponding to rolling resistance is lowered and at the same time −20 ° C. corresponding to ice grip property and wet grip property. It is possible to increase tan δ in the vicinity and around 0 ° C. Further, by blending the dinitrodiamines in this way, the mechanical strength can be improved. Therefore, when such a rubber composition is applied to a tire member, for example, a tread portion, it is expected to improve economy by reducing fuel consumption of a vehicle and improve braking performance on a wet road surface and on snow and icy road surfaces. Is expected to improve safety.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Tsukasa Wakatsuki, 5-1, Anezaki coast, Ichihara, Chiba Prefecture Sumitomo Chemical Co., Ltd. (72) Inventor, Mitsuji Tsuji, 5-1, Anesaki coast, Ichihara, Chiba Sumitomo Chemical Co., Ltd. Business

Claims (8)

[Claims] 1. A copolymer represented by the general formula (I): ## STR1 ## at the polymer terminal of a copolymer obtained by copolymerizing (A) styrene and butadiene. A benzophenone compound represented by the formula (wherein Q represents methyl or ethyl) is introduced, (1) the styrene unit is 3 to 30% by weight, the butadiene unit is 97 to 70% by weight, and (2) butadiene. The vinyl bond content of the part 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) 0.1 to 10 parts by weight of the general formula (II) per 100 parts by weight of the raw rubber. 2] (In the formula, X is a divalent chain aliphatic group, a cycloaliphatic group or an aromatic group, and halogen or oxygen can be contained in the group; R ¹ is a hydrogen atom, a chain aliphatic group A cyclic aliphatic group or an aromatic group, but when both X and R ¹ are chain aliphatic groups, the nitrogen atoms may be further linked to each other via R ¹ ; R ² and R ³ is each independently a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and R ² and R ³ may combine to form a ring). A rubber composition comprising: 2. The raw rubber is substantially the modified styrene /
The rubber composition according to claim 1, which comprises a butadiene copolymer. 3. A raw material rubber comprising 50% by weight or more of the modified styrene / butadiene copolymer, and another diene rubber 5
The rubber composition according to claim 1, which comprises 0% by weight or less. 4. The rubber composition according to claim 3, wherein the raw material rubber is a blend system 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. X in the general formula (II) has 4 to 12 carbon atoms.
The rubber composition according to any one of claims 1 to 5, which is a chain aliphatic group. 7. A tire manufactured from the rubber composition according to claim 1. 8. The tire according to claim 7, wherein the rubber composition is used in a tread portion.