JP3013052B2 - 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 requirements for such rubber materials for tires include (1) excellent breaking characteristics such as abrasion resistance, (2) low rolling resistance corresponding to low fuel consumption, and (3) wet road surfaces. It has excellent brake braking performance (wet grip performance) and excellent brake braking performance on ice or on icy roads (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 due to 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 during high-frequency periodic deformation generated between the tire tread and fine unevenness of the road surface during braking, and hysteresis is required to improve them Losses 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 a good correlation can be obtained with tan δ (loss coefficient: a measure of hysteresis loss), a wet grip property with tan δ near 0 ° C, and an 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 low temperatures around 0 ° C. and −20 ° C. is increased, and tan δ at high temperatures around 60 ° C. is increased.
It can be seen that δ should be reduced.

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, JP-A-63-23942
In Japanese Patent Application Laid-Open No. HEI 1-247437, dinitrodiamines represented by the following general formula (I) are proposed.

[0008]

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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 linear An aliphatic group, a cycloaliphatic group or an aromatic group, X and R
^{When 1} is a chain aliphatic group, 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 atom having 1 to 12 carbon atoms.
Wherein 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]

DISCLOSURE OF THE INVENTION The present inventors have obtained a polymer obtained by polymerizing isoprene in an organic solvent using a specific polyisoprene rubber, that is, an organic alkali metal compound as a polymerization initiator, and having 1,2 bonds or 3 , the total amount of both 4 bond content I der least 25 wt% is less than 50 wt%, and M
By using a polyisoprene rubber having a Mooney viscosity of 20 to 150 represented by L _{1 + 4} (100 ° C.),
It has been found that the effect of adding the dinitrodiamine represented by (I) is more effectively exerted, and a rubber composition having excellent low-temperature properties and rolling resistance can be obtained.

[0013] The present invention, obtained isoprene is polymerized in an organic solvent an organic alkali metal compound as a polymerization initiator, 1,2-bond content or 3,4 bond content both I der least 25 wt% Is less than 50% by weight , and has a Mooney viscosity of 20 to 150 expressed as ML _{1 + 4} (100 ° C.), a raw rubber mainly composed of polyisoprene rubber, carbon black, and a raw rubber 100. 0.1 per part by weight
An object of the present invention is to provide a rubber composition containing up to 10 parts by weight of a dinitrodiamine represented by the above general formula (I).

[0014] become mainly of raw rubber in the present invention, the total amount of both I Oh <br/> at 1,2-bond content or 3,4 coupling amount 25 wt% or more be less than 50 wt% And ML
It is a polyisoprene rubber having a Mooney viscosity represented by _{1 + 4} (100 ° C.) of 20 to 150. 1,2 bond amount and 3,4 bond amount
Is more than 50% by weight, the ice grip property is poor.
On the other hand, if both the 1 , 2 bond amount and the 3, 4 bond amount are less than 25% by weight, the wet grip property is inferior, so that it is not preferable. The Mooney viscosity represented by ML _{1 + 4} (100 ° C)
If it is less than 20, the breaking strength will be inferior. On the other hand, if the Mooney viscosity exceeds 150, problems will arise in workability, which is not preferable.

The polyisoprene rubber can be produced by polymerizing isoprene by a solution polymerization method using an organic alkali metal compound known as a living polymerization method as an initiator. In particular, an organic lithium compound is used as a polymerization initiator, and a Lewis basic compound such as ethers or tertiary amines is used as a control agent for 1, 2, or 3, 4 bond amounts to polymerize an inert hydrocarbon compound. The method using a solvent is preferable because the polymerization reaction is excellent in stability and the reaction can be easily controlled.

Examples of the inert polymerization solvent include aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, aliphatic hydrocarbons such as hexane and heptane, and alicyclic hydrocarbons such as cyclopentane, cyclohexane and methylcyclohexane. It is preferable to use hydrogen and the like in controlling the polymerization reaction. These solvents can be used alone or as a mixture of two or more. From the solvent and the raw material monomer isoprene, substances that destroy the initiator or destroy the active terminal of the polymer, such as water, oxygen, carbon dioxide, certain sulfur compounds, acetylenes, etc. It must be sufficiently removed.

The organolithium compound suitable as an initiator in the solution polymerization is generally known as a one-terminal or both-terminal-initiated anionic polymerization initiator, and specific examples thereof include ethyllithium, propyllithium, Examples thereof include butyl lithium, amyl lithium, trimethylene dilithium, tetramethylene dilithium, hexyl lithium, cyclohexyl lithium, phenyl lithium, tolyl lithium, and naphthyl lithium.

Various known compounds can be used as the Lewis basic compound serving as a control agent for the amount of 1,2 bond or 3,4 bond, however, considering the availability in industrial practice. Then, ethers or tertiary amines are preferably used.

Examples of ethers that can be used include cyclic ethers such as tetrahydrofuran, tetrahydropyran, and 1,4-dioxane; aliphatic monoethers such as diethyl ether and dibutyl ether; ethylene glycol diethyl ether; Examples thereof include aliphatic polyethers such as butyl ether, diethylene glycol diethyl ether and diethylene glycol dibutyl ether, and aromatic ethers such as phenyl ether and anisole. Examples of tertiary amines include triethylamine, tripropylamine,
Besides trialkylamines such as tributylamine,
N, N, N ', N'-tetramethylethylenediamine,
Compounds such as N, N-diethylaniline, pyridine, quinoline and the like can be mentioned.

The polymerization temperature may vary depending on the target microstructure, but from the viewpoint of economy and side reactions, the polymerization temperature ranges from 0 to 150.
C. is preferred. Further, in order to obtain a rubber composition having excellent processability, it is also effective to react a binder having a functionality of two or more, such as silicon tetrachloride, tin tetrachloride, dimethyl adipate, diethyl adipate, and divinylbenzene. It is. Further, in addition to the binder, it can be modified with various polar compounds capable of reacting with the active terminal.

The thus obtained 1,2 bond amount or 3,
(4) Polyisoprene rubber having a large bonding amount and a Mooney viscosity in a specific range can be oil-extended by adding an extending oil as needed. In the case of oil extension, the extension oil can be used in a proportion of 100 parts by weight or less based on 100 parts by weight of the polyisoprene rubber.

As the raw rubber in the present invention, the polyisoprene rubber having a large amount of 1,2 bonds or 3,4 bonds obtained in this manner and having a Mooney viscosity in a specific range can be used alone. Further, a polyisoprene rubber containing at least 50% by weight and blended with another diene rubber in a range of up to 50% by weight can also be used. Examples of the diene rubber that can be blended include styrene / butadiene copolymer rubber, butadiene rubber, and natural rubber. 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 the above polyisoprene rubber 5%.
0 to 95 parts by weight and 50 to 5 parts by weight of another diene rubber.

As the carbon black used in the present invention, various carbon blacks having conventionally used different reinforcing properties, for example, SAF, ISAF, HAF, SAF
PF, FEF, GPF, SRF, MT, etc.,
The type is not particularly limited. Of these,
It is preferable to use carbon black having a nitrogen adsorption specific surface area of about 30 to 130 m ² / g, for example, ISAF, HAF, FEF or the like. Although the amount of carbon black added is not particularly limited, it is usually 10 to 15 parts by weight per 100 parts by weight of rubber.
It is preferably about 0 parts by weight, 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 (I) that can be used in the present invention include the following compounds. In the following examples, -Z represents the following group.

[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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As described above, the linking group X in the general formula (I) is a divalent chain aliphatic group, a cycloaliphatic group or an aromatic group, as in the 33rd and 34th examples. Halogen may be contained in the group, and Examples 40 to 43
Oxygen can be included in the group as an example. Among these, compounds in which X is a chain aliphatic group, particularly a chain aliphatic group having 4 to 12 carbon atoms, particularly an alkylene, are preferably used. Other preferable examples of X include an aromatic group such as phenylene or diphenylmethane (a bond is generated from each of two benzene rings).

R ¹ in the general formula (I) is a hydrogen atom, a chain aliphatic group, a cycloaliphatic group or an aromatic group. When X and R ¹ are both chain aliphatic groups, As in the above-mentioned Examples 23 and 24, nitrogen atoms are further linked via R ¹ to form a ring, for example, a 6-membered ring such as a piperazine ring, with X, R ¹ and two nitrogen atoms. Are also included.

Further, R ² and R ³ in the general formula (I) may be the same or different from each other, and are each a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. Note that, as in the twelfth, thirteenth, twenty- ^second, and thirtieth examples, those in which R ² and R ³ are bonded to form a ring, for example, a 6-membered ring, together with the carbon atom to which they are bonded. Included.

The form in which such dinitrodiamines are blended with the rubber is arbitrary, and may be any one of the compounds alone, a mixture of a plurality of compounds, a mixture with a carrier such as clay which does not affect the physical properties of the rubber, Further, it may take a form such as a mixture with various compounding agents described below. Therefore, any of these forms can be added to the raw rubber mainly composed of polyisoprene rubber.

The amount of dinitrodiamine 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 is insufficient, and if it is too large, it becomes uneconomical. The dinitrodiamine is 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 be used according to the purpose. For example, various vulcanization accelerators such as thiazoles, thiurams, dithioic acids, guanidines, phthalic anhydride, scorch retarders such as N- (cyclohexylthio) phthalimide, other sulfur, fillers, stearic acid, peptizers, Zinc white, process oil, processing aids, antioxidants, 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 compounding agent 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. In compounding the dinitrodiamine of the general formula (I) with the specific polyisoprene rubber according to the present invention, the compounding time is not particularly limited, and may be compounded in any of the first step and the second step. Alternatively, it may be blended in another step. However, preferably, it is added in the first step in which carbon black or the like is compounded, and the compounding temperature at that time is usually 140 to 20 because higher temperatures have a greater effect of improving the rubber properties.
About 0 ° C. is 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, 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.

[0039]

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. In the following examples, “%” and “parts” mean “% by weight” and “parts by weight”, respectively, unless otherwise specified.
Phr means parts per 100 parts of rubber.

The dinitrodiamines used in the examples are as follows, and are indicated by respective symbols. 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 E: N, N'-bis (2-methyl-2-nitropropyl) -4,4'-diaminodiphenylmethane

In the following examples, rubber physical properties were tested by the following methods. Mooney viscosity raw rubber, at a temperature of 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. tan δ (loss coefficient) Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho, values at 60 ° C., 0 ° C. and −20 ° C. were measured under the conditions of a static load of 100 g and a frequency of 10 Hz. T at 60 ° C
anδ corresponds to the rolling resistance, and the smaller the value, the greater the effect of lowering the rolling resistance. On the other hand, tan at 0 ° C.
δ corresponds to the wet grip property, and tan δ at −20 ° C. corresponds to the ice grip property, and the larger the value, the greater the effect of improving the grip property. Conforms to tensile stress _{(M 300) JIS K-6301} , measured at dumbbell-shaped test piece.

Synthesis Example of Polyisoprene Rubber Using n-hexane as a polymerization solvent, n-butyllithium as an initiator, and ethylene glycol diethyl ether as a control agent for 1, 2, or 3, 4 bond amounts, 65 After isoprene was polymerized at ℃, a coupling reaction was carried out using silicon tetrachloride. At this time, by changing the amount of ethylene glycol diethyl ether, the amount of 1,2 bond or 3,4 bond is changed, and in part, a highly aromatic extender oil (SBR) is used.
(Aroma oil for # 1712) to obtain polyisoprene rubber shown below.

IR-1: 3,4 bond 64% 1,2 bond 5% cis 1,4 bond 23% trans 1,4 bond 8% Glass transition temperature −11 ° C. Mooney viscosity 57ML _{1 + 4} (100 ° C.) 37.5 phr oil

IR-2: 3,4 bond 57% 1,2 bond 5% cis 1,4 bond 27% trans 1,4 bond 11% Glass transition temperature -20 ° C Mooney viscosity 44ML _{1 + 4} (100 ° C) Extension 37.5 phr oil

IR-3: 3,4 bond 46% 1,2 bond 3% cis 1,4 bond 35% trans 1,4 bond 16% Glass transition temperature −31 ° C. Mooney viscosity 44ML _{1 + 4} (100 ° C.) 37.5 phr oil

IR-4: 3,4 bond 25% 1,2 bond 1% cis 1,4 bond 67% trans 1,4 bond 7% Glass transition temperature −50 ° C. Mooney viscosity 80ML _{1 + 4} (100 ° C.) Without oil

For comparison, a commercially available polyisoprene rubber "JSRIR2200" (manufactured by Nippon Synthetic Rubber Co., Ltd .; hereinafter abbreviated as IR2200) was used. Its physical properties were as follows. IR2200: 3,4 bond 0% 1,2 bond 1% cis 1,4 bond 98% trans 1,4 bond 1% Glass transition temperature -70 ° C Mooney viscosity 82ML _{1 + 4} (100 ° C) No extension oil

Example 1 <Blending formulation> Polyisoprene rubber or natural rubber described in Tables 1 to 5 HAF black (N330) 45 parts Stearic acid 3 parts Zinc zinc 5 parts Antiaging agent 2 parts (N-phenyl-N'-) 1,3-dimethylbutyl-p-phenylene diamine) Vulcanization accelerator 1 part (N-cyclohexyl-2-benzothiazylsulfenamide) Io 2 parts Dinitrodiamine Tables 1 to 5

As a banbury mixer, 2 manufactured by Toyo Seiki Co., Ltd.
Oil bath temperature 170 using 50ml Labo Plastmill
Based on the above formulation, dinitrodiamines, carbon black, stearic acid, and zinc white were added to polyisoprene rubber or natural rubber at a temperature of 60 ° C. and kneaded at 60 rpm for 10 minutes. The rubber temperature at this time was 130 to 150 ° C.

Next, this 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 above test results are summarized in Tables 1 to 5 together with the variable values of the formulation.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[0054]

[0055]

Reference Example 1 <Blending Formula> Polyisoprene rubber (IR-1: 64% of 3,4 bonds) 82.5 parts (including 22.5 parts of extending oil) Styrene / butadiene copolymer rubber (SBR # 1500) or 40 parts butadiene rubber (BR 01: manufactured by Nippon Synthetic Rubber Co., Ltd.) ISAF Black (N220) 70 parts stearic acid 2 parts zinc white 3 parts antioxidant 2 parts (N-phenyl-N'-1,3-dimethyl) Butyl-p-phenylene diamine) Vulcanization accelerator 1 part (N-cyclohexyl-2-benzothiazylsulfenamide) Io 2 parts Dinitrodiamine Table 6

The same experiment as in Example 1 was carried out on the basis of the above compounding formula in which the raw rubber was a blend of polyisoprene rubber and styrene / butadiene copolymer rubber or butadiene rubber. The experimental results are summarized in Table 6 together with the variable values of the formulation.

[0058]

[Table 6]

[0059]

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, according to the present invention, by mixing dinitrodiamines with a specific polyisoprene rubber, tan δ at around 60 ° C. corresponding to rolling resistance is reduced, and -2 corresponding to ice grip property and wet grip property is obtained.
The tan δ around 0 ° C. and around 0 ° C. can be increased. In addition, by mixing dinitrodiamines in this way, 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 Tsuki Wakatsuki 5-1, Anesaki Kaigan, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd. (72) Inventor Mitsuji Tsuji 5-1, Anesaki Kaigan, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd. In-company (56) References JP-A-1-174547 (JP, A) JP-A-1-174546 (JP, A) JP-A-1-195101 (JP, A) JP-A-1-247437 (JP, A) JP-A-2-28230 (JP, A) JP-A-63-23942 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 9/00 C08K 3/04 C08K 5 / 32 B60C 1/00

Claims (7)

(57) [Claims] An organic alkali metal compound is used as a polymerization initiator to polymerize isoprene in an organic solvent.
Binding amount or 3,4 bond content both der least 25 wt%
Is less than 50% by weight , and a raw rubber mainly composed of polyisoprene rubber having a Mooney viscosity represented by ML _{1 + 4} (100 ° C.) of 20 to 150, carbon black, and
0.1 to 10 parts by weight of the following general formula (I) per 100 parts by weight of the raw rubber Wherein X is a divalent chain aliphatic, cycloaliphatic or aromatic group, which may contain halogen or oxygen; R ¹ is a hydrogen atom, a chain aliphatic group , is a cyclic aliphatic group or an aromatic group, and X and R ¹ are both chain aliphatic group may be further connected to each other is a nitrogen atom each other via R ^1; R ² and R ³ each independently represents 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 characterized by the following: 2. The rubber composition according to claim 1, wherein the raw rubber substantially comprises the polyisoprene rubber. 3. The raw material rubber is polyisoprene rubber 50.
2. The rubber composition according to claim 1, comprising at least 50 parts by weight of another diene rubber and at most 50 parts by weight. 4. The raw material rubber is polyisoprene rubber 50.
The rubber composition according to claim 3, wherein the rubber composition is a blend of 50 to 95 parts by weight and 50 to 5 parts by weight of styrene / butadiene copolymer rubber or butadiene rubber. 5. The rubber composition according to claim 1, wherein X in the general formula (I) is a linear aliphatic group having 4 to 12 carbon atoms. 6. A tire produced from the rubber composition according to claim 1. 7. The tire according to claim 6, wherein said rubber composition is used in a tread portion.