JP2522322B2 - Rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition having improved dynamic physical properties of a vulcanized rubber containing a filler.

<Related Art> In recent years, there has been a great social demand for improving fuel economy of passenger car tires and extending running life of large tires such as truck and bus tires. For this reason, it is an important issue how to improve the dynamic physical properties such as resilience and heat generation of vulcanized rubber often used for such tires and the like.

As methods for improving the dynamic physical properties, there are known methods such as improving the microstructure and molecular weight distribution of rubber, improving the compounding formulation of organic rubber chemicals and fillers, and adding dynamic physical property improvers. Among these methods, the method of adding a dynamic physical property improver is attracting attention because it can easily improve dynamic physical properties and can be applied to natural rubber as compared with other methods. .

Therefore, as such a dynamic physical property-improving agent, for example, 8-oxyquinoline derivative having a specific structure disclosed in JP-A-58-118887 and sulfur in the molecule disclosed in JP-A-59-18740 are disclosed. A nitro compound containing was developed.

<Problems to be Solved by the Invention> However, although the above-mentioned 8-oxyquinoline derivative and sulfur-containing nitro compounds have excellent effects on dynamic physical properties such as resilience, the scorch property is greatly accelerated and resistance is improved. There is a problem that the flex cracking property is deteriorated, which is not always satisfactory.

From such a background, the present inventors have completed the present invention as a result of conducting research to develop a rubber composition having the above-mentioned problems and having excellent dynamic physical properties.

<Means for Solving Problems> The present invention relates to a natural rubber or a synthetic rubber, a filler of 10 to 100 parts by weight, and a general formula for 100 parts by weight of rubber. (In the formula, R ¹ is a chain aliphatic group having 1 to 18 carbon atoms or a cycloaliphatic group, and these may contain a halogen atom, an oxygen atom or a nitrogen atom. 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.) 0.1 to 10 parts by weight of the nitroamine derivative represented by The present invention provides a rubber composition which is characterized by containing at most a resorcin-based adhesive.

The nitroamine derivative used in the present invention is, for example, JA
It can be produced according to the method described in m.Chem.Soc., 68 10 (1946). That is, the nitroamines represented by the general formula (I) can be obtained by a condensation reaction using aliphatic or cycloaliphatic amines, nitroalkanes and formaldehyde as raw materials.

In addition, in the general formula (I), a nitroamine derivative in which the substituent R ¹ is an aromatic group can also be easily synthesized by the same method as described above. It cannot be applied to the present invention because it does not have the effect of improving the dynamic physical properties of natural rubber or synthetic rubber containing a filler.

The following compounds are specifically exemplified as the nitroamine derivative used in the present invention. Among these, among these,
The substituent R ¹ in the general formula (I) is a chain aliphatic group,
Above all, a nitroamine derivative having a chain aliphatic group having 4 to 12 carbon atoms is preferably used. Further, the above general formula (I)
As the substituents R ² and R ³ in, a hydrogen atom or an alkyl group having 1 to 6 carbon atoms is preferable, and especially R ² and R ³
Those in which both R ³ are alkyl groups are preferably used.

In the following examples, -Z is the formula Is shown.

CH ₃ NH-Z, CH ₃ CH ₂ NH-Z, CH ₃ CH _{2 2} NH-Z, (CH ₃ ) ₂ CHNH-Z, CH ₃ CH _{2 3} NH-Z, (CH ₃ ) ₃ CNH-Z, _{CH 3 CH 2 5 NH-Z} , _{(CH 3) 3 CCH 2 CH} 2 NH-Z, CH 3 CH 2) 7 -NH-Z, CH 3 CH 2 9 NH-Z, CH 3 CH 2 11 NH-Z, CH 3 CH 2 17 NH-Z , CH ₃ CH _{2 3} NHCH _{2 2} NO ₂ , CH ₃ CH _{2 7} NHCH _{2 2} NO ₂ , HOCH _{2 2} NH-Z, H ₂ NCH _{2 2} NH-Z, H ₂ NCH _{2 6} NH-Z, ClCH _{2 2} NH-Z, BrCH _{2 2} NH-Z, The amount of the nitroamine derivative used is not particularly limited, but if it is too small, the effect of improving the dynamic physical properties is insufficient, and if it is too large, the effect is saturated and uneconomical. It is in the range of 0.1 to 10 parts by weight per part by weight.

The types of rubber that can be used in the present invention include natural rubber, polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), and polybutadiene rubber (B
R), acrylonitrile-butadiene copolymer rubber (NB
R), isoprene-isobutylene copolymer rubber (IIR), ethylene / propylene diene copolymer rubber (EPDM) and the like are exemplified, and highly unsaturated rubber is preferably used.

Further, as the filler used in the present invention, carbon black, silica, which has been conventionally used in the rubber field,
Examples of talc and clay include carbon black, with carbon black being particularly preferred. Such a filler is used in the same mixing ratio as that conventionally used, and is not particularly specified in the present invention, but for example, about 10 to 100 parts by weight is used per 100 parts by weight of rubber.

Generally, when compounding agents are compounded with natural rubber or synthetic rubber, the compounding is basically performed in two steps. That is, fillers, process oils, stearic acid, etc. are compounded in the first step at a relatively high rubber temperature of about 120 to 200 ° C, and vulcanization accelerators and vulcanizing agents are added at a rubber temperature of about 80 to 120 ° C. It is compounded in the second step at a relatively low temperature.

In producing the rubber composition of the present invention, the compounding of the nitroamine derivative into the rubber may be carried out by any method, and may be carried out in the second step at a relatively low temperature together with the vulcanization accelerator and the vulcanizing agent. It is preferable to mix it in the first step in which the filler and the like are mixed. The compounding temperature at that time is higher than that at a higher temperature, although the effect of improving the dynamic physical properties of the vulcanized rubber is greater, but if compounded at an excessively high temperature, oxidative deterioration of the rubber is caused. At this time, for the purpose of further improving the effect, a small amount of a vulcanizing agent such as a vulcanization accelerator or morpholine disulfide may be added as an auxiliary agent.

Further, when a nitroamine derivative and a filler such as carbon black are blended according to the present invention, an increase in torque is seen, but for the purpose of improving this, a peptizer or a retarder may be used in combination, and further, It goes without saying that various general rubber chemicals and softening agents may be used in combination as necessary. However, the rubber composition of the present invention is
Substantially free of resorcin-based adhesives such as aminophenols.

<Examples> Hereinafter, the present invention will be specifically described with reference to Examples.

Production Example-1 129.2 g (1.0 mol) of 1-aminooctane was added to a one-necked four-necked flask equipped with a stirrer, a thermometer and a condenser.
89.1 g (1.0 mol) of nitropropane and 150 ml of methanol as a solvent were charged, and the temperature was raised to 50 ° C. At this temperature,
To this mixture, 81.2 g (1.0 mol) of 87% aqueous formalin solution was added dropwise over 30 minutes. Then mix this mixture with 50
Incubated at ℃ for 1 hour.

After the reaction was completed, the reaction mass was cooled to room temperature and toluene 30
An extraction operation was performed by adding 0 ml. After the liquid separation operation, 100 ml of water was added to the obtained oil layer for washing, and the oil layer obtained by performing the liquid separation operation again was concentrated under the condition of 50 ° C./10 torr and N- (2-methyl- 225.5 g (yield 97.9%) of 2-nitropropyl) -1-aminooctane was obtained as a light brown liquid. This compound is referred to as compound (A).

The elemental analysis values of this compound are as follows.

CHN measured value 62.12% 11.34% 12.14% calculated value 62.57% 11.38% 12.16% By the same method as above, various nitroamine derivatives shown in Table 1 were produced and used as test samples of the present invention.

Example 1 Based on natural rubber, a rubber composition was prepared based on the following formulation and various tests were conducted. For comparison, 7- (dimethyldithiocarbamoylmethyl) -8-hydroxyquinoline (abbreviated as DTHQ), N- (2-methyl-2-nitropropyl) aniline and sulfur monochloride were added as compounds to be blended. A resinous substance (abbreviated as MNDS) obtained by reacting at a molar ratio of 1: 1 and N- (2-methyl-2-) in which the substituent R ¹ in the general formula (I) is an aromatic group.
Similar tests were carried out when nitropropyl) aniline (abbreviated as NNPA) was used and when these compounds were not added.

(Composition) Natural rubber (RSS # 1) 100 parts by weight HAF Black 45 〃 Stearic acid 3 〃 Aromatic process oil 3 〃 Zinc white 5 〃 Vulcanization accelerator (N-cyclohexyl-2-benzothiazo
Rusulfenamide) 1 〃 sulfur 2 〃 compound (nitroamines or comparative compounds according to the present invention
Material) As described in Table-2, when blending, Toyo Seiki as a Banbury mixer
Machine made 250ml lab plastomill First, use the oil bath
At the temperature of 170 ℃, it is shown in the above compounded recipe on the base of natural rubber.
Carbon black, zinc white, process oil, stain
Allic acid, and compounds (nitroamines according to the present invention
Or comparative compound), and the mixer rotation speed of 60 rpm
Then, the mixture was kneaded for 5 minutes. The rubber temperature at that time is 150-160 ℃
Met. This formulation is then transferred to an open mill, 40-
At a temperature of 50 ° C., the vulcanization accelerator shown in the above formulation and
Sulfur was kneaded and blended. Furthermore, this compound was added to the vulcanization pre-cursor.
Vulcanize at 145 ° C for 20 minutes to obtain the desired shape.
After that, it was subjected to various tests.

 The various test methods are as follows.

(1) Mooney scorch property In accordance with JIS-K-6300, the time from 125 ° C. to a rise of 5 points from the lowest value was defined as the scorch time. However, the SBR system of Example 2 described later was performed at 135 ° C.

(2) Tensile physical properties and resilience The measurements were performed according to JIS-K-6301. Tensile stress (M
No. 5 type ring was used for ₃₀₀ ). For resilience, a Lupke type test machine was used.

(3) Heat resistance It was based on ASTM-D-623-58. Loaded 35lb, stroke 6.35mm, frequency using Goodrich type heat generation tester
Exothermic temperature (4
(Represented by the difference between the rubber temperature after 0 minutes and the initial rubber temperature).

(4) Bending Fatigue Resistance Using a Fatigue-to-Failure Tester manufactured by Monsanto Co., the number of times of bending until breaking was measured under the condition of a strain rate of 100%.

Table 2 shows the compounding conditions of the compounds (nitroamines according to the present invention or comparative compounds) and the results of the various tests described above.

Example 2 In place of natural rubber, SBR # 1500 was used, except that the oil bath temperature of the Banbury mixer was set to 190 ° C.
A test piece was prepared in the same manner as in Example 1, and an evaluation test was performed in the same manner. The results are shown in Table-3.

<Effects of the Invention> The rubber composition of the present invention described above has a great effect of improving dynamic physical properties such as resilience and heat resistance of vulcanized rubber such as natural rubber containing a filler and various synthetic rubbers.
Moreover, the conventional technology also improves flex crack resistance, which was a physical property contradictory to these, and also does not accelerate the scorch property as rapidly as when a conventional dynamic physical property improver is blended. Exhibits a scorch property close to that when not blended.

Due to these characteristics, it can be applied not only to the tread portion of various tires but also to other portions of the tire, and can also be effectively used for industrial products such as anti-vibration rubber.

Claims (1)

(57) [Claims] 1. Natural rubber or synthetic rubber, 10 to 100 parts by weight of a filler, and general formula per 100 parts by weight of rubber. (In the formula, R ¹ is a chain aliphatic group having 1 to 18 carbon atoms or a cycloaliphatic group, and these may contain a halogen atom, an oxygen atom or a nitrogen atom. 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.) 0.1 to 10 parts by weight of the nitroamine derivative represented by A rubber composition, which is characterized by comprising at most, and does not substantially contain a resorcin-based adhesive.