JPH1149897A - Rubber composition and tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition that can be vulcanized in a shortened time without the problem on carcinogenicity, shows high adhesion particularly to polyester tire codes and to provide tires. SOLUTION: This rubber composition contains at least one selected from the rubber components of natural rubber, isoprene rubber, butadiene rubber and styrene-butadiene rubber and is curable at 100-190 deg.C. In this case, the objective tire rubber composition contains at least one of a primary vulcanization acceleartor selected from sulfur, benzothiazylsulfen amides and mercaptobenzothiazole and at least one of a secondary vulcanization acceleartor selected from zinc dibenzyl dithiocarbamate and tetrabenzylthiuram disulfide. The tire is provided with the carcass layer 32 prepared by this composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition which can be vulcanized in a short time without a problem of carcinogenicity and has high adhesive strength and a tire using the same.

[0002]

2. Description of the Related Art In recent years, in the tire manufacturing process, it has become an important issue to shorten the vulcanization time in order to increase the manufacturing efficiency. In order to achieve this object, it is conceivable to increase the vulcanization temperature. However, increasing the vulcanization temperature is not an effective solution. That is, in the vulcanization step, the external components such as the tread layer are close to a heat source such as a mold and a bladder, so that they are quickly subjected to heat transfer and vulcanized in a short time, whereas the carcass layer, the breaker layer, etc. The internal components are at a distance from the heat source and are difficult to vulcanize. Therefore, in the actual vulcanization process, the vulcanization of the internal components is the rate-determining stage, and it is necessary to shorten the vulcanization time.However, raising the vulcanization temperature is based on the above heat transfer situation, This is because although it has a direct effect on the vulcanization of the external component, it is hardly effective on the vulcanization of the internal component.

[0003] Therefore, the composition of the rubber composition has been devised so that the composition of the internal components can be changed so that vulcanization can be carried out efficiently and vulcanization can be performed even with a small amount of heat of vulcanization. Have been done. Conventionally, as an example of changing the composition of the internal component, a rubber composition used for coating a carcass cord is used as a secondary vulcanization accelerator together with a thiazole-based sulfenamide as a primary vulcanization accelerator. There is an example in which a guanidine compound or an alkylthiuram-based compound such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, or tetramethylthiuramonosulfide is used in combination, thereby shortening the vulcanization time.

[0004]

However, the guanidine compound is thermally decomposed during vulcanization to produce an amino compound, and the amino compound causes aminolysis (depolymerization) of the polyester carcass cord. And the adhesiveness between the carcass cord and the cured rubber is reduced. Also,
The alkylthiuram-based compound has a problem that it cannot be used industrially because it has high carcinogenicity and is a precursor of nitrosamines whose use is strictly regulated.

An object of the present invention is to provide a rubber composition which has no problem of carcinogenicity, can be vulcanized in a short time, and has a high adhesive strength to polyester, and a tire using the same. That is.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, a rubber composition using a specific primary vulcanization accelerator and a secondary vulcanization accelerator is The inventors have found that vulcanization can be performed in a short time and that the problems of adhesiveness and carcinogenicity can be solved at once. That is, the rubber composition of the present invention contains at least one rubber component selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber and styrene-butadiene rubber, and
A rubber composition curable at 0 to 190 ° C., comprising sulfur, at least one primary vulcanization accelerator selected from benzothiazylsulfenamides and mercaptobenzothiazole, and zinc dibenzyldithiocarbamate. And at least one secondary vulcanization accelerator selected from tetrabenzylthiuram disulfide.

The tire according to the present invention is a tire provided with a carcass layer obtained by coating a carcass cord with a vulcanized product.
The vulcanized product is obtained from the rubber composition of the present invention.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Rubber Composition The rubber composition according to the present invention comprises a rubber component, sulfur,
It contains a primary vulcanization accelerator and a secondary vulcanization accelerator. As rubber components, natural rubber (NR), isoprene rubber (I
R), butadiene rubber (BR) and styrene-butadiene rubber (SBR). These rubber components are
The order of vulcanization rate is usually as follows.

(Fast) NR>IR>BR> SBR (Slow) Therefore, from the viewpoint that the vulcanization accelerator works more effectively for a polymer system having a slow vulcanization rate, the SBR compound is preferred. On the other hand, from the viewpoint of improving adhesiveness, it is common to mainly use NR, and a small amount of BR and / or SBR is added to about 30 parts by weight in 100 parts by weight of the rubber component.
It may be blended by weight.

The primary vulcanization accelerator is a component that is blended to reduce the amount of sulfur as a vulcanizing agent, to shorten the vulcanization time, and to lower the vulcanization temperature. Exercise effect. Examples of the primary vulcanization accelerator include at least one selected from benzothiazylsulfenamides and mercaptobenzothiazole.

The benzothiazylsulfenamides include N-tert-butyl-2-benzothiazylsulfenamide (BBS), N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-oxy Diethylene-2-benzothiazylsulfenamide (OB
S), N, N-diisopropyl-2-benzothiazylsulfenamide (DPBS) and the like, and one or more of these are used. When the benzothiazylsulfenamide is at least one selected from N-tert-butyl-2-benzothiazylsulfenamide and N-cyclohexyl-2-benzothiazylsulfenamide, scorch is stable. Excellent vulcanization properties can be obtained.

Although the secondary vulcanization accelerator does not show a sufficient vulcanization acceleration effect by itself, it has an auxiliary effect on the primary vulcanization accelerator. Examples of the secondary vulcanization accelerator include at least one selected from zinc dibenzyldithiocarbamate and tetrabenzylthiuram disulfide. The rubber composition of the present invention can be vulcanized in a short time by using the primary vulcanization accelerator and the secondary vulcanization accelerator in combination, and can maintain particularly high adhesion to polyester and the like. Become like 1 used in the present invention
Neither the secondary vulcanization accelerator nor the secondary vulcanization accelerator is a precursor of nitrosamines, and therefore does not cause a problem of carcinogenicity.

The rubber composition of the present invention has a temperature of 100 to 190 ° C.
Vulcanizable at low temperatures. The vulcanization temperature is preferably 140
To 190 ° C, more preferably 140 to 180 ° C. If the vulcanization temperature is lower than 100 ° C., it takes a long time to vulcanize. On the other hand, if the vulcanization temperature exceeds 190 ° C,
If the vulcanization temperature is too high, the polymer in the rubber component undergoes molecular shearing and the like, and the vulcanization properties are reduced.

The mixing ratio of each component contained in the rubber composition is not particularly limited, but preferably 1 to 6 parts by weight of sulfur and 1 to 1 part by weight of primary vulcanization accelerator to 100 parts by weight of the rubber component. 3 parts by weight, 1 to 2 parts by weight of secondary vulcanization accelerator, more preferably 2 to 4 parts by weight of sulfur, 1 to 2.5 parts by weight of primary vulcanization accelerator, 1 to 2 parts by weight of secondary vulcanization accelerator 1.5 parts by weight.

If necessary, the rubber composition may contain, for example, a mineral oil softener such as a paraffinic, naphthenic or aromatic mineral, dioctyl phthalate (DOP), dibutyl phthalate (DBP), or dioctyl sepate ( DO
S), a plasticizer such as dioctyl adipate (DOA); a vulcanization aid such as zinc oxide and stearic acid; a foaming agent; an antioxidant; and an additive such as wax. The mixing ratio of these additives is not particularly limited.

As the method for producing the rubber composition, known methods can be employed. For example, the above-mentioned components can be mixed at 120 to 150 ° C. and 5 to 10 by using a rubber kneading apparatus such as an open roll or a Banbury mixer. There is a method of kneading for a minute. Tire The tire of the present invention is obtained by vulcanizing a raw tire. The tire of the present invention includes a carcass layer obtained by coating a carcass cord with the rubber composition at the stage of a green tire.

FIG. 1 shows a cross section of a tire according to the present invention. The tire has side portions 2 and 2 arranged on the left and right sides of a tread portion 1 having a ground contact surface 11 as a center, and bead portions 3 and 3 extend from these left and right side portions 2 and 2. The left and right bead portions 3, 3 are fixed to a rim (not shown). In the tread portion 1, a tread groove 12 is formed in the ground contact surface 11. The outer portion of the tread portion 1 includes a tread layer 13a serving as a cap and a tread layer 13b serving as a base, and a nylon band 14
Are arranged, and the breaker layer 15 is arranged further inside. The bead portion 3 has a bead apex layer 31 at the center.
Are arranged, the periphery of the bead apex layer 31 is wrapped by the carcass layer 32, and the clinch apex layer 33 is arranged further outside the outer carcass layer 32. The inner carcass layer 32 merges with the outer carcass layer 32 at the upper end of the bead apex layer 31, extends to the side portion 2 to become an inner layer of the side portion 2, further extends to the tread portion 1, and extends to the inner layer of the tread portion 1. It has become. In the figure, reference numeral 4 denotes a bead wire.

As can be seen from the above description, the carcass layer constitutes the entire inner portion of the tire, and the carcass cord serves as a skeleton of the tire and functions to withstand loads, impacts and air pressure. The carcass cord is made of, for example, a material such as polyester, nylon, and steel, and is usually twisted to impart strength and elongation. The carcass cord is woven in a cord shape, impregnated with an adhesive such as resorcin-formaldehyde (RFL), and covered and protected with the above rubber composition to obtain a carcass layer.

The raw tire includes, in addition to the carcass layer, a tread layer for protecting the carcass layer from impact from a road surface, a breaker layer (belt) for tightening the carcass layer, a bead portion for fixing the tire to a rim, and the like, as described above. It has. This green tire is put into a mold vulcanizer and, for example, 1
When vulcanized at 40 to 180 ° C. for 10 to 15 minutes, a tire is obtained.

[0020]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples.
In the following examples, "parts" indicates "parts by weight". (Examples 1 to 3 and Comparative Examples 1 to 4)
The rubber compositions of Examples 1 to 3 and Comparative Examples 1 to 4 were obtained by kneading at 140 ° C. for 10 minutes using a Banbury mixer. Using these rubber compositions, green tires using a cord-unvulcanized rubber composite coated with a polyester carcass cord were manufactured and vulcanized at 180 ° C. to obtain vulcanized tires.

The performance of each of the obtained rubber compositions was evaluated by the evaluation method described later, and the results are shown in Table 1. (Example 4, Comparative Example 5) Example 1 with the composition shown in Table 2
In the same manner as described above, the rubber compositions of Example 4 and Comparative Example 5 were obtained to produce vulcanized tires, and the performance of each rubber composition was evaluated by the evaluation method described later. The results are shown in Table 2. In this case, the vulcanization temperature was changed from 180 ° C to 140 ° C.

[0022]

[Table 1]

[0023]

[Table 2]

* 1 SBR 1500 manufactured by Sumitomo Chemical Co., Ltd. * 2 Showa Black N330 manufactured by Showa Cabot. * 3 Antigen FR manufactured by Sumitomo Chemical Co., Ltd. * 4 Nouchira NS N-tert manufactured by Ouchi Shinko Chemical
-Butyl-2-benzothiazylsulfenamide.

* 5 Sanshin Chemical Suncellor CM N-
Cyclohexyl-2-benzothiazylsulfenamide. * 6 Succinol D diphenylguanidine manufactured by Sumitomo Chemical Co., Ltd. * 7 Noxeller TT tetramethylthiuram disulfide manufactured by Ouchi Shinko Chemical.

* 8 Nouchira ZTC manufactured by Ouchi Shinko Chemical
Zinc dibenzyldithiocarbamate. * 9 TBz TD manufactured by Akzo Tetrabenzylthiuram disulfide. * 10 Ouchi Shinko Chemical Noxeller M Mercaptobenzothiazole. [Evaluation method] Vulcanization test Using a vibration type vulcanization tester (curast meter) described in JIS K 6300, a vulcanization test was performed at a measurement temperature of 160 ° C., and time and torque were plotted. A curve was created. Here, the reason why the torque is generated with the passage of time is that the curing and crosslinking of the rubber composition progress by the action of sulfur under heating. The maximum torque indicates the efficiency of the crosslinking reaction.

Assuming that the minimum value of the torque of the cross-linking curve is ML and the maximum value is MH, the difference ME is expressed by MH-ML.
Here, the time (minute) that becomes ML + 0.1ME is T10,
The time (minute) at which ML + 0.9ME is obtained is defined as T90. T10 is a standard of the tire manufacturing process.
If it is less than 8, rubber scorch may occur. On the other hand, T90 is a measure of the vulcanization time, and the smaller the value, the shorter the vulcanization time. Vulcanization time A peel test was conducted between the cord of the vulcanized tire and the cord of the vulcanized rubber composite and the coated rubber, and the minimum time at which no void was observed on the peeled surface of the coated rubber was defined as the vulcanization time. Adhesive performance The cord-vulcanized rubber composite obtained above was subjected to wet heat aging (temperature 8).
(0 ° C., humidity 80%, 7 days), a peel test was performed, the amount of rubber adhered to the cord was measured, and the adhesion was evaluated according to the following criteria.

Good: 60% or more of the cord surface after peeling is covered with rubber. X: Less than 60% of the cord surface after peeling was covered with rubber. If the carcinogenic rubber composition does not contain a compound that is a precursor of nitrosamines and the problem of carcinogenicity does not occur, "No" means that a compound that is a precursor of nitrosamines is contained and the problem of carcinogenicity is included. Was evaluated as “Yes”.

[0029]

The rubber composition according to the present invention can be vulcanized in a short time and has a particularly high adhesive strength to polyester and the like.
Neither the primary vulcanization accelerator nor the secondary vulcanization accelerator contained in the rubber composition is a precursor of nitrosamines, so that the problem of carcinogenicity when vulcanizing the rubber composition is raised. Will not cause.

Since the carcass layer of the tire according to the present invention is manufactured using the above rubber composition, the adhesion between the carcass cord such as polyester and the vulcanized rubber is high, and the tire is vulcanized in a short time. ing. Does not cause carcinogenic problems.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a tire according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tread part 2 Side part 3 Bead part 13a, 13b Tread layer 15 Breaker layer 32 Carcass layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 5/47 C08K 5/47

Claims (2)

[Claims] 1. A rubber composition comprising at least one rubber component selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber and styrene-butadiene rubber,
A rubber composition curable at 90 ° C., comprising: sulfur; at least one primary vulcanization accelerator selected from benzothiazylsulfenamides and mercaptobenzothiazole; zinc dibenzyldithiocarbamate; And at least one secondary vulcanization accelerator selected from benzylthiuram disulfide. 2. A tire provided with a carcass layer obtained by coating a carcass cord with a vulcanized product, wherein the vulcanized product is obtained from the rubber composition according to claim 1.