JP2009132835A - Rubber composition for tire inner liner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire inner liner, while inhibiting modulus change and maintaining heat-aging resistance, hardly causing compression set even under a high temperature and high pressure state in running. <P>SOLUTION: This rubber composition is characterized by blending a 0.5 pt.wt. to 4 pts.wt. polyalkylene glycol having a 106 to 500 molecular weight and 0 to 0.3 pt.wt. sulfur based on a 100 pts.wt. diene-based rubber containing a ≥50 wt.% halogenated butyl rubber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a rubber composition for a tire inner liner, and more particularly to a rubber composition for a tire inner liner that hardly causes compression set even at a high temperature and high pressure during running while maintaining an initial modulus and heat aging resistance. .

  On the inner surface of the tubeless pneumatic tire, a rubber composition mainly composed of butyl rubber having excellent air permeation prevention performance is provided as an inner liner (see, for example, Patent Document 1).

  As shown in FIG. 1 (A), the pneumatic tire provided with the inner liner in this way has a uniform thickness as shown in FIG. 1 (A). The inner liner 1 laminated on the inner peripheral side of the carcass layer 2 has a uniform thickness. Yes. However, when used for a long time, the inner liner 1 is permanently deformed by compression due to the deformation of the covering rubber 3 of the carcass layer 2 as shown in FIG. May cause a thin gauge part. In particular, this problem occurs remarkably in a heavy-duty tire having a high tire pressure and a large load.

  Thus, when a thin, permanently deformed portion of the gauge occurs in the inner liner, air permeability is inversely proportional to the gauge, so that air penetrates into the carcass layer, belt layer, etc. from the thin portion and promotes oxidative degradation. The problem of tire destruction occurs.

As a countermeasure, it is conceivable that the modulus is increased by increasing the amount of a vulcanizing compound such as sulfur used in the rubber composition for the inner liner, thereby suppressing compression set. However, when the amount of sulfur is increased, the initial modulus becomes excessive and the heat aging resistance deteriorates.
JP 2002-212363 A

  An object of the present invention is to provide a rubber composition for a tire inner liner that hardly causes compression set even under high-temperature and high-pressure conditions during running while suppressing change in modulus and maintaining heat aging resistance.

  The rubber composition for a tire inner liner according to the present invention that achieves the above-described object provides a polyalkylene glycol having a molecular weight of 106 to 500 to 0.5 to 100 parts by weight of 100 parts by weight of a diene rubber containing 50% by weight or more of halogenated butyl rubber. 4 parts by weight and 0 to 0.3 parts by weight of sulfur are blended.

  The polyalkylene glycol may be diethylene glycol or dipropylene glycol. This rubber composition for a tire inner learner is suitable for forming an inner liner of a heavy duty pneumatic tire.

  The rubber composition for a tire inner liner of the present invention was blended with 0.5 to 4 parts by weight of a polyalkylene glycol having a molecular weight of 106 to 500 to 100 parts by weight of a diene rubber containing 50% by weight or more of a halogenated butyl rubber. Since the compression set is made as small as possible and the sulfur content is 0 to 0.3 parts by weight, it is possible to prevent the modulus from becoming excessive and to maintain the heat aging resistance.

  The base rubber of the rubber composition for a tire inner liner of the present invention is a diene rubber containing 50% by weight or more of a halogenated butyl rubber. Halogenated butyl rubber is obtained by halogenating butyl rubber with bromine, chlorine or the like, and has a characteristic that the air permeability coefficient is minimal. Among the diene rubbers, the content of halogenated butyl rubber is 50% by weight or more, preferably 75 to 100% by weight. When the halogenated butyl rubber is less than 50% by weight, the air permeation preventing performance may not be sufficiently obtained.

  The diene rubber other than the halogenated butyl rubber may be any rubber that can be blended with the rubber for the tire inner liner, and examples thereof include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and butyl rubber. It is done. These diene rubbers can be used alone or in combination.

  The rubber composition for a tire inner liner can suppress compression set under high temperature and pressure by blending polyalkylene glycol. The polyalkylene glycol is synthesized by addition polymerization of an alkylene oxide to an alcohol. Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide. Examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, ethylene oxide-propylene oxide random copolymer, and ethylene oxide-propylene oxide block copolymer. Among them, polyethylene glycol and polypropylene glycol are preferable, Particularly preferred are diethylene glycol and dipropylene glycol.

  The polyalkylene glycol used in the present invention has a molecular weight of 106 to 500, preferably 106 to 400. The lower limit of the molecular weight is the molecular weight 106 of diethylene glycol. When the molecular weight exceeds 500, compression set cannot be sufficiently suppressed, and heat aging resistance is also deteriorated. The molecular weight of the polyalkylene glycol is the average molecular weight when there is a distribution in the degree of polymerization and / or a mixture of a plurality of polyalkylene glycols.

  The compounding amount of the polyalkylene glycol is 0.5 to 4 parts by weight, preferably 1 to 2 parts by weight, based on 100 parts by weight of the diene rubber. When the blending amount is less than 0.5 parts by weight, compression set cannot be sufficiently suppressed. If the blending amount exceeds 4 parts by weight, the initial modulus becomes excessive.

  In this invention, the compounding quantity of sulfur is 0-0.3 weight part with respect to 100 weight part of diene rubbers, and does not need to mix | blend sulfur. When sulfur is not blended, the compression set can be made as small as possible and the heat aging resistance can be improved. On the other hand, in order to prepare the initial modulus, a small amount of sulfur can be blended together depending on the blending amount of the polyalkylene glycol. In that case, the amount of sulfur is preferably 0.01 to 0.25 parts by weight. When the compounding amount of sulfur exceeds 0.3 parts by weight, the deterioration of heat aging resistance increases when the initial modulus is set to the same level.

  The rubber composition for tire inner liners can be blended with various additives generally used in rubber compositions such as reinforcing fillers, inorganic fillers, anti-aging agents, plasticizers, and vulcanization accelerators. Such an additive can be kneaded by a general method to obtain a rubber composition which can be used for vulcanization or crosslinking. The blending amounts of these additives may be conventional conventional blending amounts as long as the object of the present invention is not adversely affected.

  The rubber composition for a tire inner liner of the present invention is preferably used for an inner liner of a pneumatic tire, and since it suppresses compression set even in a high temperature and high pressure state during running and is excellent in heat aging resistance, even during long-term use. A high level of anti-air permeation prevention performance is ensured to prevent oxidative deterioration of the tire internal members. In particular, when used for an inner liner of a heavy duty pneumatic tire, the effect is particularly remarkable, and a heavy duty pneumatic tire provided with an inner liner made of the rubber composition for a tire inner learner of the present invention has compression set and It has both heat aging resistance and excellent durability.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  Twelve types of rubber compositions (Examples 1 to 8, Comparative Examples 1 to 4) having the compositions shown in Tables 1 and 2 were weighed with components excluding sulfur and a vulcanization accelerator, respectively, and 1.8 L sealed type. Each rubber composition was obtained by kneading with a mixer for 3 to 5 minutes, adding sulfur and a vulcanization accelerator to the discharged master batch, and kneading with an 8-inch open roll. The obtained 12 kinds of rubber compositions (Examples 1 to 8, Comparative Examples 1 to 4) were vulcanized at 150 ° C. for 60 minutes in a mold having a predetermined shape for a compression set test and a tensile test. A test piece was prepared and each test was performed by the following method.

Compression set Using the test piece of the obtained rubber composition, the compression rate is 25% under the conditions of a temperature of 70 ° C. and a test time of 24 hours in accordance with JIS K6262. It was measured. The obtained results are shown in Tables 1 and 2 as an index with the value of Comparative Example 1 as 100. It means that the smaller the index, the smaller the compression set and the better.

Tensile test (300% modulus)
Using the test piece of the obtained rubber composition, a tensile test was performed at a tensile speed of 500 mm / min in accordance with JIS K6251, and 300% modulus and elongation at break were measured. The obtained 300% modulus results are shown in Tables 1 and 2 as an index with the value of Comparative Example 1 being 100. The difference between the index and the index (100.0) of Example 1 is preferably as small as possible, and is preferably within ± 15%.

Tensile test after heat aging test (300% modulus retention, elongation at break)
Using the tensile test piece of the obtained rubber composition, after performing an aging test in a gear oven at a temperature of 70 ° C. for 288 hours, a tensile test was performed at a tensile speed of 500 mm / min in accordance with JIS K6251. The 300% modulus and elongation at break were measured. The obtained results are shown in Tables 1 and 2 in terms of retention ratio (%) where the initial value of 300% modulus and the initial value of elongation at break of each rubber composition are 100, respectively. The closer these retention ratios are to 100, the better the heat aging resistance.

The types of raw materials used in Tables 1 and 2 are shown below.
Br-IIR: Brominated butyl rubber, BROMOBUTYL X2 carbon black manufactured by LANXESS: Dia Black G manufactured by Mitsubishi Chemical
PAG-1: Diethylene glycol, Diethylene Glycol (molecular weight 106) manufactured by Tokyo Chemical Industry Co., Ltd.
PAG-2: Dipropylene glycol, Dipropylene Glycol (molecular weight 134) manufactured by Tokyo Chemical Industry Co., Ltd.
PAG-3: Polyethylene glycol, manufactured by Tokyo Chemical Industry Co., Ltd. Polyethylene Glycol 400 (molecular weight 400)
PAG-4: Polyethylene glycol (Molecular weight 500, 1: 1 mixture of Polyethylene Glycol 400 and Polyethylene Glycol 600 manufactured by Tokyo Chemical Industry Co., Ltd.)
PAG-5: Polyethylene glycol, manufactured by Tokyo Chemical Industry Co., Ltd. Polyethylene Glycol 600 (molecular weight 600)
Sulfur: Fine powder with Jinhua seal oil manufactured by Tsurumi Chemical Industry Co., Ltd. Sulfuric acid: Beads stearic acid manufactured by Nippon Oil & Fats Co., Ltd. Paulownia paraffin oil: Process oil 123 manufactured by Showa Shell Sekiyu KK
Vulcanization accelerator: Sunuchi DM-PO manufactured by Ouchi Shinsei Chemical Co., Ltd.
Zinc Hana: Zinc Oxide, manufactured by Shodo Chemical Industry Co., Ltd.

(A) (B) is typical explanatory drawing of the cross section of the inner liner laminated | stacked on the carcass layer, (A) is sectional drawing of an initial state, (B) shows sectional drawing of the state after a long-term use. .

Explanation of symbols

1 Inner liner 2 Carcass layer 3 Covered rubber 4 Carcass cord

Claims (3)

  Tire inner in which 0.5 to 4 parts by weight of polyalkylene glycol having a molecular weight of 106 to 500 and 0 to 0.3 parts by weight of sulfur are blended with 100 parts by weight of diene rubber containing 50% by weight or more of halogenated butyl rubber Rubber composition for learners.   The rubber composition for a tire inner liner according to claim 1, wherein the polyalkylene glycol is diethylene glycol or dipropylene glycol.   A heavy duty pneumatic tire comprising an inner liner made of the rubber composition for a tire inner learner according to claim 1 or 2.

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