JPH07122006B2 - Rubber composition with excellent dynamic properties - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition having stable scorch characteristics and excellent dynamic characteristics.

<Prior Art> In recent years, in the automobile industry, demands for improving various physical properties of each product and part are increasing. For example, taking rubber products such as tires and anti-vibration rubber as examples, it is possible to improve fuel economy, improve durability, prolong economic life by extending product life, and improve ride comfort by reducing vibration and noise. It is becoming an important issue. Therefore, it is important to improve the dynamic properties such as resilience, heat generation, and dynamic ratio of the vulcanized rubber used for such rubber products.

As methods for improving dynamic properties, methods such as improvement in rubber microstructure and molecular weight distribution, improvement in compounding formulation of organic rubber chemicals and reinforcing agents, addition of dynamic physical property improvers, etc. are also known. Among these methods, the method of adding a dynamic physical property improver has attracted attention because it can improve the dynamic characteristics more easily than other methods and can be applied to natural rubber.

As such a physical property-improving agent, 4-nitroso-
N- (2-nitro-2-methylpropyl) aniline, 5
Nitroso compounds such as -nitroso-8-hydroxyquinoline are known. However, the hygiene of nitrosamines has become a social issue, making their use difficult. Therefore, as a dynamic physical property improver containing no nitroso group, JP-A-58-118837 proposes an 8-hydroxyquinoline derivative, and JP-A-59-18740 proposes a nitro compound containing sulfur. Has been done. Although these compounds are effective in improving resilience and heat resistance, they have a problem of reducing flex cracking resistance.

On the other hand, the following general formula [I] proposed by JP-A-63-23942 is proposed. (In the formula, X is a divalent chain aliphatic group, a cycloaliphatic group or an aromatic group, and may contain halogen or oxygen. 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, nitrogen atoms may be further linked to each other via R ^1. R ² and R ³ are 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.) The dinitrodiamines represented by the above have the above-mentioned problems. However, it is possible to obtain a rubber composition having excellent dynamic characteristics when compounded with rubber.

Since these dinitroamines impart excellent dynamic properties to rubber, they have been applied to tires and anti-vibration rubbers. However, although the dinitrodiamines have improved scorch properties as compared with the above-mentioned 8-hydroxyquinoline derivatives and the like, they are basic and tend to accelerate the scorch properties. Therefore, the processing step and vulcanization time of the rubber composition containing the dinitrodiamines are
Compared with the case of a normal rubber composition not containing the compound,
The current situation is that we have to make some changes.

Conventionally, as a method of delaying the scorch property, it has been known to add a scorch retarder, and particularly N
-(Cyclohexylthio) phthalimide is often used. Although this compound is effective for delaying scorch, it reduces dynamic properties and
Since it has blooming properties, it was necessary to minimize the amount added, which was a practical problem.

<Problems to be Solved by the Invention> From such a background, the present inventors intend to develop a rubber composition that maximizes the dynamic characteristics that are characteristic of the dinitrodiamines and that also has stable scorch properties. As a result of earnest research, the present invention has been completed.

<Means for Solving the Problems> The present invention is a rubber composition containing carbon black, which is a raw material rubber made of natural rubber and / or synthetic rubber.
With respect to 100 parts by weight, the dinitrodiamines represented by the general formula [I] 0.1 to 1
0 parts by weight, N- (cyclohexylthio) phthalimide 0.05 to 0.3 parts by weight, and general formula [II] (Wherein R is a divalent acyclic aliphatic group, a cycloaliphatic group or an aromatic group, and the group may contain a hetero atom) 0.05 to 1 part by weight of bismaleimides The present invention provides a rubber composition characterized in that

Specific examples of the dinitrodiamines of the general formula [I] used in the present invention include the following compounds. In the following examples, -Z is Indicates.

_{(1) Z-NHCH 2 2} NH-Z (2) Z-NHCH 2 3 NH-Z (3) Z-NHCH 2 4 NH-Z (4) Z-NHCH 2 6 NH-Z (5) Z-NHCH _{2 10} NH-Z (6) Z-NHCH _{2 12} NH-Z (8) NO ₂ CH ₂ 2NHCH _{2 2} NHCH _{2 2} NO ₂ (9) NO ₂ CH _{2 2} NHCH _{2 6} NHCH _{2 2} NO ₂ Thus, the substituent X in the general formula [I] is a divalent chain aliphatic group, a cycloaliphatic group or an aromatic group,
A halogen can be contained in the group as in the 33rd and 34th examples, and an oxygen can be contained in the group as in the 40th to 43rd examples. Among these, those in which X is a chain aliphatic group, particularly a chain aliphatic group having 4 to 12 carbon atoms are preferably used.

R ¹ in the general formula [I] is a hydrogen atom, a chain aliphatic group, a cycloaliphatic group or an aromatic group, and when X and R ¹ are both chain aliphatic groups, as in the first 23 patients and the 24 patients, via R ¹ further linked nitrogen atom together, X, are also encompassed that form a ring with R ¹ and the two nitrogen atoms.

Further, R ² and R ³ in the general formula [I], which may be the same or different, are each a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. In addition, the above
Also included are those in which R ² and R ³ are bonded to each other to form a ring, as in Examples 12, 13, 22, and 30.

The form of compounding such dinitrodiamines with rubber is arbitrary, and the compound alone, a mixture of a plurality of compounds, a mixture with a carrier such as clay that does not affect the physical properties of rubber, and other It may be in the form of a compounding example, such as N- (cyclohexylthio) phthalimide or bismaleimide which is another component of the present invention, or a mixture with various compounding agents described later. Therefore, any of these forms can be added to the rubber.

The amount of the dinitrodiamines used is 0.1 to 10 parts by weight per 100 parts by weight of the rubber, because if it is too small, the effect of improving the dynamic properties is insufficient, and if it is too large, it becomes uneconomical, and preferably It is in the range of 0.2 to 3 parts by weight.

If the amount of N- (cyclohexylthio) phthalimide used is too small, the effect of improving the scorch property is insufficient, and if it is too large, the dynamic properties are deteriorated or the blaming property is observed. ~ 0.3
The range is parts by weight.

Furthermore, the above-mentioned general formula [I
Specific examples of the bismaleimides of [I] include the following compounds.

N, N'-ethylene bismaleimide, N, N'-hexamethylene bismaleimide, N, N'-dodecamethylene bismaleimide, N, N '-(2,2,4-trimethylhexamethylene) bismaleimide, N, N '-(oxy-dipropylene) bismaleimide, N, N'-(amino-dipropylene) bismaleimide, N, N '-(ethylene-dioxydipropylene) bismaleimide, N, N'-(1, 4-cyclohexylene) bismaleimide, N, N '-(1,3-cyclohexylene) bismaleimide, N, N'-(methylene-1,4-dicyclohexylene) bismaleimide, N, N '-(isopropyiene Ridene-1,4-dicyclohexylene) bismaleimide, N, N '-(oxy-1,4-dicyclohexylene) bismaleimide, N, N'-(m-phenylene) bismaleimide, N, N'- (P-phenylene) bismaleimide, N, N '-(o-phenylene) bismaleimide, N, N'-(1,3-naphthylene) bismaleimide, N, N '-(1,4-naphthylene) bismaleimide, N, N'-(1 , 5-naphthylene) bismaleimide, N, N '-(3,3'-dimethyl-4,4'-biphenylene) bismaleimide, N, N'-(3,3'-dichloro-4,4'-biphenylene ) Bismaleimide, N, N '-(2,4-pyridindiyl) bismaleimide, N, N'-(2,6-pyridinediyl) bismaleimide, N, N '-(4-methyl-2,6- Pyridinediyl) bismaleimide, N, N '-(1,4-anthraquinonediyl) bismaleimide, N, N'-(4-methyl-1,3-phenylene) bismaleimide, N, N '-(5-methyl -1,3-phenylene) bismaleimide, N, N '-(2-methyl-1,3-phenylene) bismaleimide, N, N'-(2-methyl-1,4-phenyl) Nylene) bismaleimide, N, N '-(4,6-dimethyl-1,3-phenylene) bismaleimide, N, N'-(4,5-dimethyl-1,3-phenylene) bismaleimide, N, N ′-(2,4-Dimethyl-1,3-phenylene) bismaleimide, N, N ′-(2,5-dimethyl-1,3-phenylene) bismaleimide, N, N ′-(2,3-dimethyl -1,4-phenylene) bismaleimide, N, N '-(2,5-dimethyl-1,4-phenylene) bismaleimide, N, N'-(2,6-dimethyl-1,4-phenylene) bis Maleimide, N, N '-(4,6-dichloro-1,3-phenylene) bismaleimide, N, N'-(5-chloro-1,3-phenylene) bismaleimide, N, N '-(5- Hydroxy-1,3-phenylene) bismaleimide, N, N '-(5-methoxy-1,3-phenylene) bismaleimide, N, N'-(methylene-di-p-phenylene) bi Maleimide, N, N '-(isopropylidene-di-p-phenylene) bismaleimide, N, N'-(oxy-di-p-phenylene) bismaleimide, N, N '-(thio-di-p-phenylene) ) Bismaleimide, N, N '-(dithio-di-p-phenylene) bismaleimide, N, N'-(sulfonyl-di-p-phenylene) bismaleimide, N, N '-(carbonyl-di-p- Phenylene) bismaleimide R in the general formula [II] is a divalent acyclic aliphatic group, a cycloaliphatic group or an aromatic group, and these are, for example, oxy-dialkylene, amino-dialkylene, alkylene- Dioxydialkylene, oxy-dicyclohexylene, pyridinediyl, anthraquinonediyl, oxy-diphenylene, thio-diphenylene, dithio-diphenylene, sulfonyl- Phenylene, carbonyl -
Heteroatoms such as O, N, S can be included, such as diphenylene. The acyclic aliphatic group, the cyclic aliphatic group and the aromatic group which form R may be substituted. The group which can be substituted with the acyclic aliphatic group,
Halogen (eg chlorine or bromine), hydroxy, lower (eg C ₁ -C ₄ ) alkoxy and the like can be mentioned. Further, as a group which can be substituted on the cyclic aliphatic group or aromatic group, lower (for example, C _{1 to} C ₄ ) alkyl, halogen (for example, chlorine or bromine),
Examples thereof include hydroxy and lower (for example, C _{1 to} C ₄ ) alkoxy.

Among these, bismaleimides in which R in the general formula [II] is an aromatic group having 6 to 8 carbon atoms or an aliphatic group having 4 to 8 carbon atoms are preferably used.

If the amount of the bismaleimides [II] used is too small, the effect of improving the scorch property is insufficient, and if it is too large, the crosslinking density increases and the elongation properties deteriorate, which is not preferable in some rubber products. Therefore, it is 0.0 per 100 parts by weight of rubber.
It is 5 to 1 part by weight, preferably 0.1 to 0.5 part by weight.

The bismaleimides of the general formula [II] which are the subject of the present invention are disclosed in JP-A-61-166844 and JP-A-61-168842.
It is known from JP-A No. 1993-163200 that the rubber itself is compounded in order to improve the reversion property of the rubber, but the dinitrodiamines represented by the general formula [I] and N-
The use in the coexistence with (cyclohexylthio) phthalimide is first revealed by the present invention. Further, in the present invention, while making full use of the excellent dynamic characteristics of the dinitrodiamines represented by the general formula [I],
In order to improve the scorchability of dinitrodiamines, N
It is added in a specific amount together with-(cyclohexylthio) phthalimide, whereby a composition having no deterioration in dynamic properties and no blooming property can be obtained for the first time.

As the rubber that can be used in the present invention, in addition to natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, acrylonitrile-butadiene copolymer rubber, isoprene-isobutylene copolymer rubber, ethylene-propylene-diene copolymer Various synthetic rubbers such as rubber are exemplified, and these rubbers can be used alone or blended with different kinds of rubber.
Among these, natural rubber alone or a blend system with a synthetic rubber mainly composed of natural rubber is preferable.

As the carbon black, various carbon blacks having different reinforcing properties that have been conventionally used can also be used in the present invention, and the type thereof is not particularly limited. The amount of addition is not particularly limited, but usually rubber
Used in 150 parts by weight or less per 100 parts by weight, preferably
It is selected from the range of 10 to 150 parts by weight.

In the present invention, various other compounding agents commonly used in the rubber industry can also be used according to the purpose. Usually, fillers, sulfur, stearic acid, peptizers, zinc white, various vulcanization accelerators, process oils, processing aids, antioxidants, antiozonants, waxes and the like are used. The types and amounts of these compounding agents can be selected as necessary and are not particularly limited in the present invention.

Generally, when compounding agents are compounded with natural rubber or synthetic rubber, the compounding is basically performed in two steps. That is,
Carbon black and other fillers, process oils, stearic acid, etc. are added in the first step at a relatively high rubber temperature of 120 to 220 ° C, and vulcanization accelerators and vulcanizing agents are used at rubber temperatures of 40 to 120 ° C. It is added in the second step at a relatively low temperature.

The dinitrodiamines of the general formula [I] according to the present invention, N-
(Cyclohexylthio) phthalimide and the general formula [I
The bismaleimides of I] can be compounded in any step. However, the dinitrodiamines are preferably added in the first step in which carbon black or the like is blended, and the blending temperature at that time is higher at 140 to 200 ° C. because the effect of improving the rubber properties is higher at higher temperatures. preferable. Further, N- (cyclohexylthio) phthalimide and bismaleimides have a large tendency to deteriorate the dynamic physical properties when added in the first step at high temperature, and therefore are preferably added in the second step at relatively low temperature.

The rubber composition of the present invention is preferably used, for example, as various members of a tire, particularly a tread portion or a vibration-proof rubber. For example, this rubber composition can be applied to the tread portion or other members and molded by a method commonly used in the tire industry to obtain a tire. Further, the rubber composition can be molded into an appropriate shape or adhered to a metal to obtain a vibration-proof rubber.

<Example> Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.
In the following examples, "%" or "part" is based on weight unless otherwise specified.

The dinitrodiamines and bismaleimides used in the examples are as follows, and are represented by the respective symbols below.

Dinitrodiamines 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 bismaleimides F: N, N ′-(m-phenylene) bismaleimide G: N, N′-hexamethylene bismaleimide Example 1 As a Banbury mixer, using Toyo Seiki's 250 ml Labo Plastomill, at an oil bath temperature of 170 ° C., based on the above compounding recipe, dinitrodiamines, carbon black, stearic acid, process oil and zinc white were added to natural rubber. The mixture was kneaded at a mixer rotation speed of 60 rpm for 5 minutes. The rubber temperature at this time was 150 to 160 ° C.

This formulation was then transferred to an open mill and at a temperature of 60-70 ° C, the N- (cyclohexylthio) shown in the formulation above was used.
Phthalimide, bismaleimides, antioxidant, vulcanization accelerator and sulfur were added and kneaded.

After further vulcanizing at 145 ° C for 25 minutes with a vulcanizing press,
It was subjected to various tests. However, the following Mooney scorch test was carried out using the compound before vulcanization. The test results are summarized in Table-1.

The various test methods are as follows.

(1) Mooney scorch property For the rubber compound before vulcanization, in accordance with JIS K-6300, 1
The time required for the temperature to rise by 5 points from the minimum value at 25 ° C was defined as scorch time.

(2) Resilience It was measured using a Lupke type tester.

(3) Heat resistance Measured according to ASTM D-623-58. That is, using a Goodrich type heat generation tester, load 35 lbs, stroke
The heat generation temperature after 40 minutes (displayed by the difference between the rubber temperature after 40 minutes and the initial rubber temperature) was measured under the conditions of 6.35 mm, frequency 1800 rpm, and chamber temperature of 40 ° C.

(4) 60 ° C. tan δ (loss coefficient) The viscosity was measured using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho under the conditions of static load 300 g, frequency 50 Hz, and temperature 60 ° C. The smaller the value, the smaller the rolling resistance.

(5) Dynamic magnification Using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho, temperature
It was measured at 25 ° C and a vibration frequency of 100 Hz.

(6) Tensile stress (M ₃₀₀ ) Based on JIS K-6301, measured with a dumbbell-shaped test piece.

(7) Bloom property After leaving the vulcanized rubber sheet in an atmosphere of temperature 25 ° C and humidity 50% for 2 weeks, the surface of the vulcanized rubber was observed. When there was no blooming, ○, when blooming was × Displayed in.

Example 2 Example 1 was prepared based on the above compounding recipe in which the raw material rubber was a blend system of natural rubber and styrene-butadiene copolymer rubber.
The same experiment was performed. The vulcanization condition was 155 ° C. for 30 minutes. The results are summarized in Table-2.

<Effects of the Invention> According to the present invention, a rubber composition having stable scorch characteristics and excellent dynamic characteristics can be obtained. That is, the rubber composition of the present invention has a stable scorch property and is maintained at a high level of resilience, heat resistance, 60 ° C. tan δ and dynamic ratio. Therefore, when such a rubber composition is applied to a tire member, for example, a grip portion of a tire, the fuel economy of the vehicle and the durability of the tire are improved, and it is expected to improve the economical efficiency by extending the product life. It Further, when the rubber composition of the present invention is applied to a vibration-proof rubber, vibration and noise are reduced, and for example, in a vehicle equipped with such a vibration-proof rubber, improvement in riding comfort is expected.

Claims (7)

[Claims] 1. A rubber composition containing carbon black, which is a raw rubber made of natural rubber and / or synthetic rubber.
For 100 parts by weight, the general formula [I] (In the formula, X is a divalent chain aliphatic group, a cycloaliphatic group or an aromatic group, and may contain halogen or oxygen. 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, nitrogen atoms may be further linked to each other via R ^1. R ² and R ³ are 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) 0.1 to 10 parts by weight of dinitrodiamine, N- (Cyclohexylthio) phthalimide 0.05-0.3 parts by weight, and general formula [II] (In the formula, R is a divalent acyclic aliphatic group, a cycloaliphatic group or an aromatic group, which may contain a hetero atom). 0.05 to 1 part by weight of bismaleimide A rubber composition comprising: 2. The composition according to claim 1, wherein the raw rubber is a natural rubber alone or a blended system with a synthetic rubber mainly composed of natural rubber. 3. The composition according to claim 1 or 2, wherein X in the general formula [I] is a chain aliphatic group having 4 to 12 carbon atoms. 4. R in the general formula [II] is an aromatic group having 6 to 8 carbon atoms or an aliphatic group having 4 to 8 carbon atoms.
Or the composition according to 3. 5. A tire using the composition according to any one of claims 1 to 4. 6. The composition according to claim 5, wherein the composition is used in a tread portion.
Tires listed. 7. An anti-vibration rubber using the composition according to any one of claims 1 to 4.