KR20020037600A - Tire rubber composition for truck and bus - Google Patents

Abstract

PURPOSE: A tire rubber composition for a truck is provided, to improve the heat-resistant aging for extending the lifetime and to prevent the deterioration of physical properties due to the long-time curing at a high temperature. CONSTITUTION: The tire rubber composition comprises 100 parts by weight of rubber; 0.5-2.0 parts by weight of sulfur; 1.0-3.0 parts by weight of a sulfenamide-based curing accelerator; and 1.0-3.0 parts by weight of 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)-hexane. Preferably the sulfenamide-based curing accelerator is selected from the group consisting of N-cyclohexylbenzothiazole, N-tert-butyl-2-benzothiazolyl sulfenamide and 2-(morpholinothio)benzothiazole. The rubber is a natural rubber, or a mixture of a natural rubber and 0-30 wt% of a diene-based rubber.

Description

Tire rubber composition for truck and bus

The present invention relates to a rubber composition of a tire for truck buses. More specifically, by introducing a new vulcanizing agent into a conventional vulcanization system, it is possible to improve the anti-reversion performance and the heat aging performance compared to the conventional and semi-EV vulcanization systems. A rubber composition suitable for large tires such as truck buses.

In general, in the case of a rubber composition used in a tire, sulfur and various kinds of vulcanization accelerators are added at an appropriate ratio in order to obtain desired physical properties in the final product state, and then undergo chemical vulcanization at high temperature and high pressure. After this vulcanization process, intermolecular crosslinking occurs in the rubber and forms a network, each of which exhibits desired physical property results.

Generally, the vulcanization system is divided into three types according to the ratio of sulfur and vulcanization accelerator to be added. The ratio of sulfur to vulcanization accelerator is 2: 1 or more, that is, conventional vulcanization system having a high sulfur content, of about 1: 1 ratio. Semi-EV and Efficient Vulcanization (EV) vulcanization system with high vulcanization accelerator and low sulfur content.

Vulcanizates have different characteristics according to each vulcanization system. Conventional and semi-EV have excellent tensile strength, repulsion characteristics, dynamic properties and fatigue resistance, while thermal stability and revision resistance are high. It is deteriorated and results in an adverse physical property that the compression / permanent strain rate at high temperature becomes large. The EV vulcanometer shows the opposite property trend due to the difference in the number of bound sulfur between molecular backbones in the rubber. Conventional and semi-EV have four or more sulfur bonds between the molecular main chains, and the thermal energy of crosslinking is inferior because the dissociation energy is relatively lower than that of the EV vulcanization system having one to two sulfur. The above result will be shown.

On the other hand, large tires for truck buses with high load and high speed conditions require excellent tensile strength, tear resistance, dynamic fatigue resistance and low heat generation. High content blends are used, and vulcanization systems typically use conventional and semi-EVs.

In the case of natural rubber vulcanizates, deterioration occurs due to an increase in temperature due to heat generation during use or contact with air, that is, long time vulcanization at a high temperature, which leads to serious quality problems in the tire industry.

For large tires, long-term vulcanization at high temperatures is indispensable, and for truck tires, the resistance to heat and reversion of rubber compositions becomes increasingly essential as the conditions of use become more severe, such as increasing speed and load. It is one of the required physical properties.

However, the typical method used to improve the reversion performance of natural rubber vulcanizates is to use less sulfur.

In this case, the cross-linking structure between the main chains is monosulfide (monosulfide 1) and disulfide (disulfide 2), which means polysulfide (4 or more sulfur). More stable than However, in this case, since the tear resistance and dynamic characteristics are usually lowered, it is not preferable for a compound for truck tires.

In another method, when the type of vulcanization accelerator is changed from a sulfenamide-based thiazole vulcanization accelerator, the thermal stability is slightly increased, but the scorch stability is deteriorated, which impairs field processability.

Therefore, in order to have high tear resistance, low hysteresis property results and scorch stability and fast vulcanization speed, the vulcanization system used in the rubber composition for truck tires still uses most conventional and semi-EV systems.

Accordingly, the present inventors can improve the heat aging resistance and the reversion performance, which are disadvantages of the conventional conventional and semi-EV vulcanization systems, and at the same time maintain the excellent tensile strength, tear resistance and dynamic fatigue resistance of the vulcanizers. While studying the present method, it was found that the new vulcanizing agent was added together with the sulfur and vulcanization accelerator used in the conventional vulcanizing system to satisfy the result, thereby completing the present invention.

Accordingly, an object of the present invention is to improve the heat aging resistance and the reversion performance while maintaining the excellent tensile strength, tear resistance, and dynamic fatigue resistance of conventional and semi-EV vulcanometers. It is to provide a suitable rubber composition.

The tire rubber composition for achieving the above object is 0.5 to 2.0 parts by weight of sulfur, 1.0 to 3.0 parts by weight of sulfenamide-based vulcanization accelerator, and 1,6-bis (N, N'-dibenzylthio) based on 100 parts by weight of raw rubber. Carbamoyldithio) -hexane (1,6-bis (N, N'-dibenzylthiocarbamoyldithio) -hexane) It is characterized by introducing the vulcanization system which consists of 1.0-3.0 weight part.

The present invention will be described in more detail as follows.

The vulcanization system of the present invention is the addition of a new vulcanizing agent, 1,6-bis (N, N'-dibenzylthiocarbamoyldithio) hexane, to a system consisting of conventional sulfur and vulcanization accelerators.

The addition of the vulcanizing agent has a structure in which hexane is cross-linked in the intermolecular crosslinking in rubber after vulcanization, and has relatively high decomposition energy and has hexane in the middle compared to polysulfide having low thermal stability. It does not decompose due to temperature, resulting in excellent thermal stability and resistance to revision. In addition, since sulfide bonds (number of sulfur 1 to 3) are contained in the crosslink between hexane and the rubber molecule main chain, a certain degree of flexibility is secured, so that the tear resistance and the dynamic fatigue resistance of the conventional and semi-EV vulcanization systems are also high. It can be maintained.

The 1,6-bis (N, N'-dibenzylthiocarbamoyldithio) hexane vulcanizing agent having such a function is preferably used in an amount of 1.0 to 3.0 parts by weight based on 100 parts by weight of the raw material rubber. The sulfur content is preferably 0.5 to 2.0 parts by weight based on 100 parts by weight of the raw material rubber, and 1.0 to 3.0 parts by weight based on 100 parts by weight of the raw material rubber.

Rather than using 1,6-bis (N, N'-dibenzylthiocarbamoyldithio) hexane vulcanizing agents alone, it is preferable to use them with sulfur and vulcanization accelerators. Due to the slowing of the vulcanization rate, it is not desirable to extend the vulcanization time in order to be able to obtain the tensile property results of conventional conventional and semi-EV vulcanization systems. In addition, when the vulcanization accelerator and the 1,6-bis (N, N'-dibenzylthiocarbamoyldithio) hexane vulcanizing agent content is high, scorch stability is reduced and field processability is not preferable.

On the other hand, the vulcanization accelerator is a sulfenamide-based vulcanization accelerator, and specific compounds include N-cyclohexylbenzothiazole, N-tert-butyl-2-benzothiazolyl sulfenamide, 2- (morphonyrothio) benzothiazole, and the like. Can be mentioned.

As the raw material rubber, natural rubber may be used alone, or a diene rubber may be mixed and used within 30 parts by weight.

In addition, the carbon black may include carbon black as a reinforcing agent, and the carbon black preferably has a nitrogen adsorption specific surface area of 70 to 130 m 2 / g, and other softeners, anti-aging agents, tackifiers, etc., which are commonly used as rubber compounding agents. Of course it can be suitably blended.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Examples 1-2 and Comparative Examples 1-2

Next, the rubber was mixed by a composition ratio as shown in Table 1 to prepare rubber before vulcanization by a conventional procedure. These rubbers were vulcanized by a vulcanization time (t ₉₅ ) at 150 ° C., and hardness, tensile strength and elongation, hardness after aging, tensile strength and elongation were measured for the manufactured rubbers, and the results are shown in Table 2 below.

Here, the measurement of hardness, tensile strength and elongation was carried out according to KS M 6518, and the hardness, tensile strength and elongation after aging in air at 100 ° C. for 7 days were measured, and the percentage of aging of each property item was determined as a percentage. The lower the aging rate, the better the heat aging resistance.

Aging rate (%) = [(Physical value after aging-Physical property value before aging) / Physical property value before aging] × 100

After vulcanizing the rubber composition at 160 ° C. for 120 minutes and measuring the respective physical property values, the rubber composition was compared with the room temperature measurement values to express the rate of change of physical properties in the same manner as the aging rate. This rate of change represents the rate of decrease in physical properties of the rubber composition after high temperature and prolonged vulcanization, and indicates that the lower the rate of change, the better the reversion performance.

(Unit: parts by weight) Example Comparative Example One 2 One 2 Natural rubber 100 80 100 100 Styrene-butadiene rubber - 20 - - Carbon black 50 52 50 50 Aromatic oils 4 6 4 4 Zinc oxide 3 3 3 3 Stearic acid 1.5 One 1.5 1.5 Antioxidant 1 2 2 2 2 Antioxidant 2 One One One One Wax One One One One brimstone 0.5 One 2.5 1.5 Vulcanization accelerator 1.5 1.5 0.5 1.5 1,6-bis (N, N'-dibenzylthiocarbamoyldithio) -hexane 2.5 2 - - Anti-aging agent 1: N- (1,2-dimethylbutyl) -N'-phenyl-p-phenylenediamine anti-aging agent 2: poly-1,2-dihydro-2,2,4-trimethylquinoline vulcanization Accelerator: N-tert-butyl-2-benzothiazolyl sulfenamidecarbon black: Carbon black with nitrogen adsorption specific surface area 70-130 m <2> / g

Example Comparative Example One 2 One 2 Room temperature Hardness (Shore-A) 70 67 68 71 Tensile Strength (kg / ㎠) 280 252 278 298 Elongation (%) 515 480 530 530 Aging tensile properties (100 ℃, 7 days hot air aging) Hardness Shore-A 77 75 77 75 Increase / decrease 7 8 9 4 Tensile Strength (kg / ㎠) The tensile strength 203 176 79 139 Aging rate (%) -28% -30% -72% -53% Elongation (%) Elongation 330 300 110 240 Aging rate -36% -38% -79% -55% Extra curricular (160 ° C, 120 min vulcanization) Hardness Shore-A 69 68 63 62 Increase / decrease -One One -5 -9 Tensile Strength (kg / ㎠) The tensile strength 275 231 146 221 Rate of change -2% -8% -47% -26% Elongation (%) Elongation 480 370 320 515 Rate of change -7% -23% -40% -3%

From the results in Table 2 above, as in the present invention In the case of using a vulcanizing agent, the aging rate of tensile strength and elongation is reduced by 20% or more as compared with Comparative Examples 1 to 2, indicating that the heat aging resistance is advantageous. In addition, when the rubber composition shows the results of the physical property reduction rate measured after high temperature and prolonged vulcanization, it can be seen that the reduction rate is remarkably reduced as compared with the comparative example, and the reversion performance is improved. Example 2 is a case where natural rubber and diene rubber are mixed, but there is a difference in the absolute value of the physical property values at room temperature, after aging, and as in Example 1, the aging rate and the reduction rate are decreased, and thus the heat resistant furnace It can be seen that mars and reversion resistance have been improved.

As a result, Examples 1 and 2 using the new vulcanizing agent were all reduced in comparison with Comparative Examples 1 and 2 in the physical property aging rate after aging at 100 ° C. for 7 days and the physical property deterioration rate after 160 ° C. for 120 minutes of vulcanization. It can be seen that it is effective in improving the reversion property, and the reduction rate decrease is greater than the decrease in aging rate, indicating that the effect is more effective in improving the reversion.

As described in detail above, according to the present invention, a rubber composition using a 1,6-bis (N, N'-dibenzyldithiocarbamoyldithio) hexane vulcanizing agent in combination with a sulfur and a vulcanization accelerator is introduced. When used in a large tire for truck buses, the heat aging resistance is improved, and thus the service life of the large tire can be extended, and the physical properties of the large tire can be prevented from being deteriorated due to high temperature and prolonged vulcanization, thereby improving product quality.

Claims (4)

0.5 to 2.0 parts by weight of sulfur, 1.0 to 3.0 parts by weight of sulfenamide-based vulcanization accelerator, and 1,6-bis (N, N'-dibenzylthiocarbamoyldithio) -hexane (1,6) -bis (N, N'-dibenzylthiocarbamoyldithio) -hexane) Rubber composition of the tire for truck bus which introduces the vulcanization system which consists of 1.0-3.0 weight part. The method of claim 1, wherein the sulfenamide vulcanization accelerator is selected from the group consisting of N-cyclohexylbenzothiazole, N-tert-butyl-2-benzothiazolyl sulfenamide and 2- (morpholinothio) benzothiazole. The rubber composition of the tire for truck buses. 2. The rubber composition of a tire for truck buses according to claim 1, wherein the raw material rubber is natural rubber alone or a mixture with diene rubber. The rubber composition of a tire for truck buses according to claim 3, wherein the diene rubber is added within 30 parts by weight of 100 parts by weight of the raw rubber.