JP4782439B2 - Rubber composition and tire tube comprising the same - Google Patents

Description

  The present invention relates to a rubber composition and a tire tube comprising the same.

  In a rubber composition used for a tire tube, butyl rubber such as butyl rubber and chlorinated butyl rubber is employed as a polymer in order to retain air in the tube. However, butyl rubber has a problem that the vulcanization rate is remarkably slow because the number of unsaturated bonds in the molecule is extremely small compared to polymers such as natural rubber and styrene butadiene rubber.

  In order to increase the vulcanization speed, it is easily guessed that vulcanization with peroxide rather than vulcanization with sulfur, but butyl rubber is a radical generated during the decomposition of peroxide It was not realistic because the main chain collapsed.

  For this reason, thiuram-based and dithiocarbamic acid-based vulcanization accelerators exhibiting a remarkably excellent vulcanization-accelerating action are used for rubber compositions using butyl rubber in order to increase the vulcanization speed.

  However, compounds such as tetramethylthiuram disulfide, which is used as a general thiuram vulcanization accelerator, and zinc diethyldithiocarbamate, which is used as a general dithiocarbamate vulcanization accelerator, are in accordance with German regulation TRGS552. As shown, there is a problem in that it is converted into a nitrosamine compound that is harmful to the human body by being oxidized.

  Therefore, by using them as a vulcanization accelerator in a rubber composition for a tire tube, the health of workers is harmed by the nitrosamine compound generated in the tube production process, and from the tube dumped after use, There is concern that environmental pollution will occur due to the elution of nitrosamine compounds.

  Patent Document 1 discloses a tire tread rubber composition, but it is not intended for use in a tire tube, and there is a problem in that environmental contamination is caused by a nitrosamine compound from the rubber composition. .

JP 2003-213044 A

  The present invention provides a rubber composition that does not discharge harmful nitrosamines generated in the tube molding process and the like, and that has improved processability by increasing the adhesiveness during tube molding, and a tire tube comprising the same. With the goal.

  The present invention relates to a general formula (1) with respect to 100 parts by weight of a polymer comprising butyl rubber and / or ethylene-propylene-diene rubber.

(In the general formula (1), R ^{1 to} R ⁴ are non-linear hydrocarbon groups having 4 or more carbon atoms)
A thiuram compound represented by the general formula (2)

(In General Formula (2), R ^{1 to} R ⁴ are non-linear hydrocarbon groups having 4 or more carbon atoms)
And a rubber composition containing a total of 1 to 3.5 parts by weight of a zinc dithiocarbamate compound represented by the formula (1) and 0.5 to 2.5 parts by weight of sulfur.

  The present invention also relates to a tire tube made of the rubber composition.

  According to the present invention, by blending a specific amount of a specific thiuram compound and a zinc dithiocarbamate compound, harmful nitrosamines generated in the tube forming process and the like are not discharged, and the adhesiveness at the time of tube forming is further increased. Thus, it is possible to provide a rubber composition having improved processability and a tire tube comprising the same.

  The rubber composition of the present invention comprises a polymer, a thiuram compound, a zinc dithiocarbamate compound, and sulfur. In the present invention, a thiuram compound and a zinc dithiocarbamate compound are used as a vulcanization accelerator, and sulfur is used as a vulcanizing agent.

  The polymer is composed of butyl rubber and / or ethylene-propylene-diene rubber.

  Examples of the butyl rubber include butyl rubber (IIR), chlorinated butyl rubber (CIIR), brominated butyl rubber (BIIR) and the like. Of these, IIR is preferred because it does not contain a halogen element and is free from environmental pollution.

  Examples of the monomer component of the diene moiety in ethylene-propylene-diene rubber (EPDM) include ethylidene norbornene (ENB), dicyclohexylpentadiene (DCPD), and 1,4-hexadiene (HD). Among these, ENB is preferable because the properties of vulcanized rubber are excellent.

  The content of butyl rubber in the polymer is preferably 100 to 70% by weight, and the content of ethylene-propylene-diene rubber in the polymer is preferably 0 to 30% by weight. When the content of butyl rubber is less than 70% by weight and the content of ethylene-propylene-diene rubber exceeds 30% by weight, air permeation tends to occur and the performance as a tube tends to decrease.

  The thiuram compound (hereinafter referred to as thiuram compound 1) has the general formula (1)

It is represented by

In the general formula (1), R ^{1 to} R ⁴ represent a non-linear hydrocarbon group having 4 or more carbon atoms.

  The non-linear hydrocarbon group preferably has 10 or less carbon atoms.

  Examples of the non-linear hydrocarbon group having 4 or more carbon atoms include an aromatic-containing group such as a benzyl group, a cycloalkyl group such as a cyclopentyl group, an alkyl group such as an isobutyl group, hex-3-ene- Examples thereof include alkenyl groups such as 1-yl group and alkynyl groups such as hex-3-yn-1-yl group. Among them, the toxicity of the nitrosamine compound produced by oxidation to the human body is small, and the adhesion of the unvulcanized rubber composition obtained by blending is large (because the adhesion is improved) ), A benzyl group and an isobutyl group are preferable, and a benzyl group is particularly preferable because the tube can be easily formed.

As thiuram compounds, those in which R ^{1 to} R ⁴ are a methyl group, an ethyl group, a propyl group, or a butyl group in the general formula (1) are also known. Furthermore, since the resulting unvulcanized rubber composition has low tackiness and it is difficult to form a tube, it is not used as the thiuram compound 1.

  The content of the thiuram compound 1 is preferably 0.5 to 3.5 parts by weight with respect to 100 parts by weight of the polymer. If the content of the thiuram compound 1 is less than 0.5 parts by weight, the content of zinc dithiocarbamate increases and the blending unit price becomes extremely high, which is not economical. On the other hand, when the content of the thiuram compound 1 exceeds 3.5 parts by weight, the vulcanization rate is remarkably increased, so that the workability in the production process of the rubber composition tends to deteriorate.

  A zinc dithiocarbamate compound (hereinafter, zinc dithiocarbamate compound 2) is represented by the general formula (2)

It is represented by

In the general formula (2), R ^{1 to} R ⁴ represent a non-linear hydrocarbon group having 4 or more carbon atoms.

  The non-linear hydrocarbon group preferably has 10 or less carbon atoms.

  Non-linear hydrocarbon groups having 4 or more carbon atoms include aromatic-containing groups such as benzyl groups, cycloalkyl groups such as cyclopentyl groups, alkyl groups such as isobutyl groups, hex-3-en-1- Examples thereof include an alkenyl group such as yl group and an alkynyl group such as hex-3-yn-1-yl group. In particular, the nitrosamine compound produced by oxidation is less harmful to the human body, and the unvulcanized rubber composition obtained by blending is highly adhesive, making it easy to form a tube. Therefore, a benzyl group and an isobutyl group are preferable, and a benzyl group is particularly preferable.

As zinc dithiocarbamate compounds, those in which R ^{1 to} R ⁴ are a methyl group, an ethyl group, a propyl group or a butyl group in the general formula (2) are also known, but they are toxic by being oxidized. A nitrosamine compound is produced, and the resulting unvulcanized rubber composition has low tackiness and is difficult to form a tube. Therefore, it is not used as the zinc dithiocarbamate compound 2.

  The content of the zinc dithiocarbamate compound 2 is preferably 0.5 parts by weight or less with respect to 100 parts by weight of the polymer. Further, when the content of zinc dithiocarbamate compound 2 exceeds 0.5 parts by weight, the vulcanization rate is remarkably increased, so that workability in the production process of the rubber composition is deteriorated, and the zinc dithiocarbamate compound Since 2 is blended in a large amount, the blending unit price tends to increase, which tends to be not economical.

  The total content of thiuram compound 1 and zinc dithiocarbamate compound 2 is 1 part by weight or more, preferably 1.5 parts by weight or more with respect to 100 parts by weight of the polymer. If the total content is less than 1 part by weight, it takes a long time for vulcanization, which is not preferable. The total content of thiuram compound 1 and zinc dithiocarbamate compound 2 is 3.5 parts by weight or less, preferably 3.0 parts by weight or less, based on 100 parts by weight of the polymer. When the total content exceeds 3.5 parts by weight, the durability of the tire tube is not sufficient, and the tire tube tends to burst due to running of the tire.

  The sulfur content is 0.5 parts by weight or more, preferably 0.7 parts by weight or more with respect to 100 parts by weight of the polymer. When the content is less than 0.5 parts by weight, the properties of the vulcanized rubber are deteriorated. The sulfur content is 2.5 parts by weight or less, preferably 2.3 parts by weight or less, based on 100 parts by weight of the polymer. If the sulfur content exceeds 2.5 parts by weight, the sulfur is deposited on the rubber surface, which deteriorates workability and impairs the appearance of the product.

  In addition to the polymer, thiuram compound 1, zinc dithiocarbamate compound 2 and sulfur, the rubber composition of the present invention comprises a reinforcing filler such as carbon black used in the rubber industry, a softener such as oil, an oxidation agent, and the like. Zinc, stearic acid, etc. can be used.

  The tire tube of the present invention is preferably made of the rubber composition.

  A tire tube refers to a tire tube disposed between a tire and a rim. Specific examples of the tire include bicycle tires, automobile bias tires, motorcycle bias tires, agricultural vehicle bias tires, and the like. Among them, automobile bias tires have a significantly large production volume, and thus are in the environment. Therefore, the tire tube is preferably used for an automotive bias tire.

  The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

Various chemicals used in the examples are described below.
Butyl rubber: Butyl 265 manufactured by Nippon Butyl Co., Ltd.
EPDM: 501A manufactured by Sumitomo Chemical Co., Ltd. (monomer component of diene part: ethylidene norbornene)
Carbon black: Seest SO manufactured by Tokai Carbon Co., Ltd.
Oil: Paraffin oil manufactured by Japan Energy Co., Ltd. Zinc oxide: Zinc Hana No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Sulfur stearate manufactured by Nippon Oil & Fats Co., Ltd. Vulcanization accelerator TT: Noxeller TT (tetramethylthiuram disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator EZ: Noxeller EZ (zinc diethyldithiocarbamate) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator CZ: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator TBzTD: Sunseller TBZTD (tetrabenzylthiuram disulfide) manufactured by Sanshin Chemical Industry Co., Ltd.
Vulcanization accelerator ZTC: Noxeller ZTC (zinc dibenzyldithiocarbamate) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-2 and Comparative Examples 1-6
<Harmful to human body>
In TRGS (Technische Regeln Fuer gefaehrliche Stoffe und Zubereitungen) 552 established by the German Hazardous Substances Committee (AGS), ◯ indicates that the vulcanization accelerator used is not described, and ○ indicates that it is described did.

(Preparation of unvulcanized rubber composition)
According to the contents of Table 1, chemicals except sulfur and a vulcanization accelerator were blended, and kneaded at 150 ° C. for 5 minutes using a Banbury mixer. An unvulcanized rubber composition was prepared by further adding sulfur and a vulcanization accelerator to the obtained kneaded product and kneading at 100 ° C. for 3 minutes.

<Vulcanization time>
Using the unvulcanized rubber composition, measurement was performed according to a vulcanization curing characteristic test (JIS K6300-2). Using a curast meter, the torque under a temperature condition of 170 ° C. was measured, and the vulcanization time to reach a 90% vulcanization amount was measured. And the vulcanization time of the comparative example 1 was made into the reference | standard (100), and the other vulcanization time was displayed as the index | exponent. The larger the index, the longer it takes to vulcanize, which is not preferable.

(Production of tire tube)
Both ends of the rubber sheet extruded into a cylindrical shape were joint-molded to form an unvulcanized rubber composition into a tube shape, and vulcanized at 170 ° C. for 10 minutes to produce a tire tube.

<Adhesiveness>
During the manufacturing process of the tire tube, the adhesiveness of the unvulcanized rubber composition when molded into a tube shape was observed and evaluated. ◎ indicates that the unvulcanized rubber composition has high adhesiveness and joint molding is possible, ○ indicates that the unvulcanized rubber composition is slightly sticky and slightly difficult to mold, and △ indicates that there is no addition Since the vulcanized rubber composition does not stick at all, it indicates that molding is very difficult.

<Tube durability>
A case where the tire tube is placed between the rim and the tire is set on the rim, filled with air and run on a drum testing machine, when the vehicle can run more than 10,000 km without puncture, and otherwise The case was determined as x.

  The measurement results are shown in Table 1.

Claims (2)

For 100 parts by weight of polymer consisting of 70-100% by weight of butyl rubber and 0-30% by weight of ethylene-propylene-diene rubber,
A rubber composition containing a total of 1 to 3.5 parts by weight of tetrabenzylthiuram disulfide and zinc dibenzyldithiocarbamate , and 0.5 to 2.5 parts by weight of sulfur,
A rubber composition containing only the tetrabenzylthiuram disulfide and the zinc dibenzyldithiocarbamate as a vulcanization accelerator. A tire tube comprising the rubber composition according to claim 1 .