JPH05279528A - Rubber composition and tire made therefrom - Google Patents

Abstract

PURPOSE:To obtain a rubber composition satisfactory in vulcanization rate, processing stability, etc., and capable of giving a tire of improved durability when used as, e.g. an inner liner by compounding a specified rubber component with a specified compound, a benzothiazole vulcanization accelerator, etc. CONSTITUTION:This composition is prepared by compounding 100 pts.wt. rubber component containing at least 50 pts.wt. halogenated butyl rubber with 0.1-3.0 pts.wt. at least one member selected between a thiuram compound of formula I (wherein R1 to R4 are each 7-12C alkyl) and a dithiocarbamate compound of formula II (wherein R5 and R6 are each R1; M is an at least bivalent metal; and (n) is the number equal to the valence of the metal M), 0.1-3.0 pts.wt. benzothiazole vulcanization accelerator (e.g. dibenzothiazol disulfide), at most 30 pts.wt. softener (e.g. aromatic oil) and at most 1.5 pts.wt. S or S-containing vulcanizer (e.g. S).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition and a tire using the rubber composition for an inner liner of a tubeless tire having an inner liner or a tube of a tire with a tube. However, in the present specification, the term "tire" is used to include an inner liner that integrally forms a tire and a separate tube.

[0002]

2. Description of the Related Art Conventionally, trucks, large vehicles for construction,
In pneumatic tires such as agricultural vehicles, aircraft, passenger cars, two-wheeled vehicles, and tires for racing cars, for tubeless tires having an inner liner, for the inner liner, and for tires with a tube, for tubes,
A rubber composition having low air permeability is used. Butyl rubber or halogenated butyl rubber having low air permeability is mainly blended in such a rubber composition, but halogenated butyl rubber tends to be frequently used from the viewpoint of workability such as adhesiveness. In order to improve the vulcanizability and the like of a rubber composition containing a halogenated butyl rubber, the following formula is added to this rubber composition:

[Chemical 3] TMTD (tetramethylthiuram disulfide) represented by
It is known to compound thiuram compounds such as

[0003]

However, in such a conventional TMTD compounded rubber composition, since the rubber-rubber adhesion at the adhesive interface is insufficient, the joint part during molding is in use. May peel off and cause a malfunction, or
When used as an inner liner, the rubber-rubber adhesion between adjacent different rubbers (ply rubber) is insufficient,
Furthermore, since the elastic modulus is high, cracks are likely to occur, which causes air leakage failure.

Further, the rubber composition containing TMTD is inferior in processing stability and often causes a phenomenon of scorching during the processing step. In order to improve the co-vulcanizability of blend rubbers of low unsaturated rubber (EPDM) and diene rubbers (NR, SBR, BR, etc.), long-chain alkyl thiuram compounds or long-chain alkyl dithiocarbamate compounds are used. It is known to be used alone as a vulcanization accelerator (Journal of the Rubber Society of Japan, Vol. 45, p. 745 (1972), JP-A-50-24344). However, it does not eliminate all the above inconveniences.

In view of the above inconvenience, the present invention provides a vulcanization rate,
A rubber composition capable of sufficiently satisfying processing stability, rubber-rubber interfacial adhesion, and crack resistance, and workability using the same for an inner liner or a tube, and durability based on airtightness The purpose is to provide an excellent tire.

[0006]

As a result of earnest studies, the present inventors have combined a compound selected from the group consisting of a specific thiuram compound and a specific dithiocarbamate compound with a benzothiazole vulcanization accelerator. It has been found that the above-mentioned object can be achieved by using it.

The structure of the present invention is as follows. That is,
The rubber composition of the present invention comprises a softening agent of 30 parts with respect to 100 parts by weight of a rubber component containing 50 parts by weight or more of halogenated butyl rubber.
Below parts by weight, the following formula

[Chemical 4] (In the formula, R ₁ , R ₂ , R ₃ , and R ₄ each independently represent a straight-chain or branched-chain alkyl group having 7 to 12 carbon atoms, preferably 8), and a thiuram compound represented by , The following formula

[Chemical 5] (In the formula, R ₅ and R ₆ are each independently a carbon number of 7 to 12,
Preferably, a straight chain or branched chain alkyl group of 8 is shown, and M
Is a divalent or higher valent metal, and n is a number equal to the valence of the metal of M), and at least one of the compounds selected from the group consisting of dithiocarbamate compounds represented by 0.
1 to 3.0 parts by weight, benzothiazole vulcanization accelerator 0.1 to
Add 3.0 parts by weight and 1.5 parts by weight or less of sulfur or sulfur-based vulcanizing agent. The ratio of the benzothiazole vulcanization accelerator to the compound selected from the group consisting of the thiuram compound and the dithiocarbamate compound is 1.0 to 8.
It is preferably 0.

It is also preferred that R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each a 2-ethylhexyl group, M is antimony and n is 3. Further, each of the above rubber compositions can be used for various rubber products, but is particularly preferably used for a tube or an inner liner of a tire, for example, for trucks, aircraft, agricultural vehicles, large construction vehicles, passenger vehicles, Examples include tires for motorcycles and racing cars.

The above rubber composition can be produced by a conventional kneading method using a mixer or a kneader. At this time, a filler such as carbon black, an antioxidant, a resin, a vulcanization accelerating aid such as stearic acid and zinc oxide, and a processing aid such as a tackifier may be blended, if necessary. When used as a tire tube or an inner liner, it can be carried out by a usual manufacturing method.

In the rubber component, the halogenated butyl rubber is set to 50 parts by weight or more in order to reduce the air permeability of the rubber composition composed of these, and if it is less than 50 parts by weight, the air permeation rate is reduced. Since it is difficult to maintain the internal pressure, it is inconvenient. Examples of the softening agent include aromatic oil, spindle oil, naphthenic oil, paraffinic oil, vegetable oil, sub, etc.When the softening agent exceeds 30 parts by weight, for example, when used as an inner liner or a tube. However, the viscosity when unvulcanized is too low, which causes significant inconvenience during the processing step.

If the amount of the compound selected from the group consisting of thiuram compounds and dithiocarbamate compounds is less than 0.1 parts by weight, a sufficient vulcanization density cannot be obtained when used as an inner liner or a tube, for example. On the other hand, if it exceeds 3.0 parts by weight, the vulcanization density of the inner liner or tube is too high, which is inconvenient. When the carbon number of R ₁ , R ₂ , R ₃ and R ₄ is 6 or less, the dispersion in rubber becomes poor and the heat resistance is poor, which is inconvenient, and when it is 13 or more, the vulcanization rate is extremely delayed. Therefore, it is inconvenient.

Similarly, when the carbon number of R ₅ and R ₆ is 6 or less, the dispersion in the rubber becomes poor and the elastic modulus and the like are inconvenient, and when it is 13 or more, the vulcanization rate is very high. Since it is delayed, it is inconvenient, and examples of the metal of M include antimony, iron, copper, zinc, nickel, lead, tellurium, etc. However, when M is monovalent, the vulcanization promoting effect is insufficient, which is inconvenient. Is.

Further, as the benzothiazole vulcanization accelerator, mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), Nt-butyl-2-benzothiazolylsulfenamide (TBBS), N- Cyclohexyl-2-benzothiazolyl sulfenamide (CBS),
N-oxydiethylene-2-benzothiazolylsulfenamide (MBS), N, N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), zinc salt of mercaptobenzothiazole, 2- (4-morpholinodithio) ) Benzothiazole, 2- (2,4-dinitro-phenyl) -mercaptobenzothiazole, a salt of mercaptobenzothiazole and cyclohexylamine, N, N-diethylthiocarbamoyl-2-benzothiazolyl sulfide, and the like. MBTS or MBT is preferable, and if it is less than 0.1 parts by weight, for example, when it is used as an inner liner or a tube, it is inconvenient because a sufficient vulcanization density cannot be obtained. Vulcanization density is too high, which is inconvenient.

Examples of the vulcanizing agent include sulfur, dialkyl disulfide, diaryl disulfide, alkylphenol disulfide, dithiodimorpholine, and the like. However, when the vulcanizing agent exceeds 1.5 parts by weight, for example, the elastic modulus when used as an inner liner or a tube is increased. It is too high and inconvenient.

Further, if the ratio of the benzothiazole vulcanization accelerator and the compound selected from the group consisting of the thiuram compound and the dithiocarbamate compound is less than 1.0, the synergistic effect on the vulcanization density becomes small, which is desirable. In order to obtain the sulfur density, a larger amount is required.
As a result, the advantage of processing stability becomes small, which is inconvenient. Further, if it exceeds 8.0, similarly, the synergistic effect on the vulcanization density becomes small, and a larger amount of the compound is required to obtain the desired vulcanization density. Also, the vulcanization rate is significantly slowed, which is inconvenient in terms of productivity. Further, the crack resistance is not so much improved.

[0016]

EXAMPLES The present invention will be described below based on examples. Example A (Examples 1 to 5 and Comparative Examples 1 to 4) In Table 1, the compounding ratio (unit: parts by weight) of the rubber composition, the physical properties of the rubber composition, and the rubber composition are shown as inner liners of tires. The characteristics of the tire used for are shown below. Example A
Is a chlorinated butyl rubber (Cl-
IIR), as a thiuram compound, TEHT, TOTD and TM
TD (outside the scope of the present invention) was used, EH-Sb and EH-Zn were used as the dithiocarbamate compound, and MBTS was used as the benzothiazole vulcanization accelerator. Further, since the present invention achieves the intended purpose by using a compound selected from the group consisting of thiuram compounds and dithiocarbamate compounds, and a benzothiazole vulcanization accelerator in combination, Comparative Example 1 3 to 3, the composition lacking any of the components, and in Comparative Example 4,
The case where TMTD outside the scope of the present invention was used as the thiuram compound was shown and compared with each example. Comparative Example 4
TMTD was mixed with TEHT of Example 1 in the same molar number. Each test method is as follows.

Vulcanization rate Using an oscillating desk rheometer manufactured by Japan Synthetic Rubber Co., Ltd., the temperature was measured at 175 ° C. for Examples A and B and 155 ° C. for Example C. T90 in the table is 90 of the maximum torque value
The time (unit: minutes) required to obtain% is shown, and the smaller this value is, the faster the vulcanization rate is.

Processing stability It was measured at 130 ° C. using a Mooney viscometer manufactured by Shimadzu Corporation. The test method was performed according to JIS K6300, and T5 (unit: min) was determined. The larger this numerical value is, the better the processing stability is, which is preferable.

Rubber-Rubber Adhesion The rubber compositions of the respective examples and comparative examples were laminated with the same kind of rubber and different kinds of rubber and vulcanized, and a peeling test was conducted. The test method was carried out in accordance with JIS K6301, and the peel strength of Comparative Examples 4, 5 and 6 was set to 100, and indexed. The larger this value is, the larger the peeling strength is, and it is preferable that both the same kind of rubber and different kinds of rubber have excellent rubber-rubber adhesion. Table 2 shows the composition of the different rubbers used. Here, good adhesion between the same kind of rubber and rubber indicates that the adhesion at the joint is excellent, and that good adhesion between different kinds of rubber and rubber is used for the inner liner of the tire. At this time, it is shown that the adhesiveness with the adjacent rubber is excellent.

Crack resistance A DeMattia test was carried out according to ASTM D430. The size of the sample piece is 150 mm × 25 mm × 6.35 mm, and the bending speed is 5 Hz. The number of flexures until the cracks of Comparative Examples 4, 5 and 6 entered was set to 100, and the index was displayed. The larger this value is, the better the crack resistance is, which is preferable.

Durability of Actual Vehicles Tires using the rubber compositions of Examples 1 to 5 and Comparative Example 4 as the inner liner rubber were manufactured and run for about 40,000 km, and the number of cracks in the inner liner was examined. The smaller this value is, the more excellent the crack resistance is, which is preferable for the durability of the tire.

[0022]

[Table 1] Abbreviation explanation TEHT tetrakis 2-ethylhexyl thiuram disu
lfide) TOTD tetra octyl thiuram disulfide TMTD tetramethyl thiuram disulfide (te
tra methyl thiuramdisulfide) EH-Sb Di 2-ethylhexyl dithiocarbamate Antimony (Antimony di 2-ethyl hexyl dithio)
carbamate) EH-Zn di 2-ethylhexyl dithiocarbamate
) MBTS dibenzothiazyl disulfide
othiazyl disulfide) TBBS Nt-butyl-2-benzothiazolyl sulfenamide (Nt-buthyl-2-benzothiazolyl sulfenamid
e)

[0023]

[Table 2]

As described above, the compounded rubber compositions of Examples 1 to 5 in which a compound selected from the group consisting of thiuram compounds and dithiocarbamate compounds and a benzothiazole vulcanization accelerator were used in combination had a vulcanization rate. Is fast,
It can be seen that the processing stability is excellent, the adhesion between the same kind of rubber and the different kinds of rubber is excellent, and the crack resistance is also excellent.

Since the adhesiveness between the same kind of rubber and rubber is excellent, it can be seen that the adhesiveness at the joint portion is good, and because the adhesiveness between different kinds of rubber and rubber is excellent, when used for the inner liner, It can be seen that the adhesiveness with the adjacent rubber is good.

On the other hand, from Comparative Examples 1 and 2, when one kind of vulcanization accelerator selected from the group consisting of thiuram compounds and dithiocarbamate compounds is blended, the vulcanization rate is good, but the processing stability is very high. Inferior to the same type and different types of rubber
The rubber-to-rubber adhesion and crack resistance are also inferior to the examples.
In Comparative Example 3, the vulcanization rate was slow, and the same type / different type rubber-
The adhesion between rubbers is also very poor. Further, from Comparative Example 4, when TMTD outside the scope of the present invention was used as the thiuram compound and a benzothiazole-based vulcanization accelerator was further added, the vulcanization rate was similar to that in the Example. ,
It can be seen that the processing stability, the adhesion between the same kind and different kinds of rubber-rubber, and the crack resistance are inferior.

Further, it was found that the tire using this rubber composition for the inner liner had less cracks than the rubber composition of Comparative Example 4, and was excellent as the inner liner rubber for the tire. Incidentally, the peeling failure of the joint portion of the inner liner of the tire after running 40,000 km did not occur in the examples and the comparative examples under these conditions.

Example B (Examples 6 to 12, Comparative Example 5) Table 3 similarly shows the compounding ratio (unit: parts by weight) of the rubber composition and the physical properties of the rubber composition. In Example B, TEHT was used as the thiuram compound and EH-Sb was used as the dithiocarbamate compound. As the benzothiazole vulcanization accelerator, MBTS was used as in Example A. Further, as Comparative Example 5, an example using TMTD, which is a thiuram compound outside the scope of the present invention, was shown. The TMTD of Comparative Example 5
Was the blending amount of TEHT of Example 8 in the same number of moles. Also,
The ratio of MBTS / TEHT and MBTS / EH-Sb was changed. Also, Cl-IIR 80 parts by weight as a rubber component, ethylene propylene rubber
20 parts by weight of (EPDM) was used, and 25 parts by weight of a softening agent was added.

[0029]

[Table 3]

The ratio of MBTS / TEHT and MBTS / EH-Sb is 1.0
If it is less than the above range, the cracking resistance is excellent, but the processing stability is slightly lowered, and the effect of improving the adhesion between the same kind / different kinds of rubber-rubber is slightly small. Also, as this ratio increases, the crack resistance decreases. This ratio is 1.0 ~
It can be seen that when it is in the range of 8.0, a rubber having a fast vulcanization rate, excellent processing stability, good adhesion between the same type / different type rubber and rubber, and good crack resistance can be obtained. On the other hand, from Comparative Example 5, when TMTD out of the range of the present invention was used as the thiuram compound and a benzothiazole vulcanization accelerator was further added, the vulcanization speed and processing stability were the same as those in the Example. However, it is understood that the same type / different type rubber-rubber adhesion property and crack resistance are inferior.

Example C (Examples 13 and 14, Comparative Example 6) Table 4 similarly shows the compounding ratio (unit: parts by weight) of the rubber composition and the physical properties of the rubber composition. Example C
TEHT was used as the thiuram compound and EH-Sb was used as the dithiocarbamate compound. As the benzothiazole vulcanization accelerator, MBTS was used as in Example A. Further, as Comparative Example 6, an example using TMTD which is a thiuram compound outside the scope of the present invention is shown. The TMTD of Comparative Example 6
Is the blending amount of TEHT of Example 13 and the same model number. Also,
The ratio of MBTS / TEHT and MBTS-EH-Sb was fixed at 2. Further, 80 parts by weight of Br-IIR and 20 parts by weight of NR were used as a rubber component, and 10 parts by weight of a softening agent was added.

[0032]

[Table 4] As described above, a compound selected from the group consisting of thiuram compounds and dithiocarbamate compounds, and Example 13, in which a benzothiazole vulcanization accelerator was used in combination.
It can be seen that the rubber composition having the composition of 14 has excellent processing stability, excellent adhesion between the same kind and different kinds of rubber-rubber, and further excellent crack resistance.

On the other hand, from Comparative Example 6, when TMTD outside the scope of the present invention was used as the thiuram compound and a benzothiazole type vulcanization accelerator was further added, the vulcanization rate was similar to that of the Example. However, it can be seen that the same type / different type rubber-rubber adhesion and crack resistance are inferior. As described above, it was confirmed in this example that the curing of the present invention is also effective for Br-IIR.

[0034]

As described above, according to the present invention,
By using a specific thiuram compound and / or a specific dithiocarbamate compound in combination with a benzothiazole vulcanization accelerator in a specific blending ratio, the vulcanization speed, processing stability, and adhesion to the same or different rubbers A rubber composition capable of sufficiently satisfying both crack resistance and a tire having excellent durability such as peel resistance and crack resistance of a joint portion when the rubber composition is used as an inner liner rubber or a tube rubber. It can be realized.

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Claims (5)

[Claims] 1. A softening agent of 30 parts by weight or less based on 100 parts by weight of a rubber component containing 50 parts by weight or more of a halogenated butyl rubber, and the following formula: (In the formula, R ₁ , R ₂ , R ₃ and R ₄ each independently represent a linear or branched alkyl group having 7 to 12 carbon atoms), and a thiuram compound represented by the following formula: 2] (In the formula, R ₅ and R ₆ each independently represent a linear or branched alkyl group having 7 to 12 carbon atoms, M is a divalent or higher valent metal, and n is a valence of the metal of M. (Equal numbers) 0.1 to 3.0 parts by weight of at least one compound selected from the group consisting of dithiocarbamate compounds, 0.1 to 3.0 parts by weight of benzothiazole vulcanization accelerator, and sulfur or sulfur compounds. A rubber composition containing 1.5 parts by weight or less of a vulcanizing agent. 2. The benzothiazole vulcanization accelerator,
The rubber composition according to claim 1, wherein the ratio of the compound selected from the group consisting of the thiuram compound and the dithiocarbamate compound is 1.0 to 8.0. 3. The R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each a 2-ethylhexyl group, M is antimony, and n is 3. Item 1 or 2
The rubber composition described. 4. A tubeless tire having an inner liner, wherein the inner runner has the above-mentioned features.
A tire characterized by using the rubber composition according to any one of item 3. 5. A tire with a tube, wherein the rubber composition according to any one of claims 1 to 3 is used for the tube.