JP2010269751A - Rubber composition for inner liner, and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for an inner liner capable of improving a tire vulcanization productivity without lowering air holding performance and crack resistance of a tire inner liner layer, and to provide a pneumatic tire using the same. <P>SOLUTION: The rubber composition for the inner liner characteristically contains: 0.1 to 10 pts.mass of thermosetting resin and 0.1 to 1.5 pts.mass of zinc oxide based on 100 pts.mass of a rubber component containing butyl system rubber as a rubber main component. In the pneumatic tire an inner liner layer has two layer structure of a tire inner side surface layer (A) and a carcass side layer (B) and the rubber composition is used for the carcass side layer (B); and a rubber composition containing no thermosetting resin is used for the tire inner side surface layer (A). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition for an inner liner suitable for an inner liner of a tire for a vehicle such as a passenger car, a truck, and a bus, and a pneumatic tire using the rubber composition, and particularly without reducing air retention and crack resistance. The present invention relates to a rubber composition for an inner liner capable of improving vulcanization productivity and a pneumatic tire using the same.

Normally, pneumatic tires for vehicles such as passenger cars, trucks, and buses are provided with low-permeability rubber such as halogenated butyl rubber to prevent air leakage on the inner surface and keep the tire pressure constant. An inner liner layer as a main component is provided.
However, in general, butyl rubber has a slow vulcanization speed, and is a factor that hinders improvement in tire vulcanization productivity.

  Conventionally, as a means for improving the vulcanization rate of the inner liner layer, a method of increasing the ratio of natural rubber or isoprene rubber in the rubber component is known. However, in this method, when the ratio of the butyl rubber in the rubber component is lowered, the air retention is remarkably deteriorated and it is difficult to put it to practical use.

As a means for solving these problems, for example, with respect to 100 parts by weight of a rubber component comprising 30 to 60% by weight of butyl rubber, 20 to 50% by weight of natural rubber and / or isoprene rubber, and 10 to 40% by weight of butadiene rubber. 10 to 50 parts by weight of mica having an average particle diameter of 40 to 100 μm, 10 to 35 parts by weight of carbon black and / or silica, and 5 to 20 parts by weight of filler having an average particle diameter of 0.5 to 20 μm And a rubber composition for an inner liner in which the total content of the carbon black, silica and filler is 30 to 55 parts by weight, and a tire having an inner liner using the same (for example, refer to Patent Document 1). And a technique using a tyrium-based super-vulcanization accelerator is disclosed for vulcanization of the rubber composition for the inner liner. Yes.
However, the technique using the Tiraum-based super-vulcanization accelerator has a problem that the crosslinking density becomes too high and the crack resistance is lowered.

  On the other hand, 1 to 8 parts by weight of non-reactive alkylphenol resin having specific physical properties, 0.5 parts by weight of sulfur based on 100 parts by weight of diene rubber alone or a combination of diene rubber and halogenated butyl rubber in a specific range. Durability improved, characterized in that a rubber composition added to and blended so as to have a sulfur / accelerator ratio in the range of 5 parts by weight or less is used as an inliner adjacent member. A rubber composition containing a heavy load bias tire (for example, see Patent Document 2) or a halogenated butyl rubber alone or a blend rubber of a halogenated butyl rubber and a diene rubber as an inner liner is disposed as the inner liner. Diene rubber or diene rubber and butyl halide having a higher ratio of diene rubber than the inner liner between the ply layer In a large bias tire for a construction vehicle having an inner liner adjacent member having a rubber blend rubber component as a rubber component, the inner liner adjacent member is 1 to 6 parts by weight of blown asphalt with respect to 100 parts by weight of the rubber component. A large bias tire for construction vehicles characterized by comprising a rubber composition containing 1 to 8 parts by weight of a reactive alkylphenol resin and 0.5 to 3 parts by weight of sulfur. In a tire provided with a coating formed by coating a vulcanized elastomer mixture layer on a radially inner side of an occlusive substance layer capable of flowing into the occlusive substance layer on all or a part of the inner wall surface, the occlusive substance layer (sealant layer) includes: The main component is an elastomer having specific physical properties mixed with at least one thermosetting substance, and a small amount of the thermosetting substance. With one reticulating agent or curing agent, a tire having a self-closed layer, characterized in that it is spaced apart (e.g., see Patent Document 4) is known from the closed mixture by the closure mixture layer.

  However, these pneumatic tires provide pneumatic tires with improved durability by reinforcing the inner liner layer adjacent members and the like, and reduce the air retention and crack resistance of the present invention. The problem and technical idea are different from the rubber composition for an inner liner and the pneumatic tire using the rubber composition for the inner liner that can improve the vulcanization productivity.

JP 2008-31342 (Claims, Examples, etc.) JP-A-60-261706 (Claims, Examples, etc.) Japanese Patent Laid-Open No. 3-148304 (Claims, Examples, etc.) JP-A-55-11998 (Claims, Examples, etc.)

  The present invention has been made in view of the above-described problems of the prior art, and is intended to solve this problem. The rubber composition for an inner liner can improve vulcanization productivity without reducing air retention and crack resistance. It is an object to provide a product and a pneumatic tire using the same.

  As a result of intensive studies on the above-described conventional problems, the present inventor has specific amounts of resin and zinc oxide each having specific physical properties with respect to 100 parts by mass of a rubber component containing butyl rubber as the main rubber component. Thus, it is found that a rubber composition for an inner liner can be obtained, and that the pneumatic tire can be obtained by using the rubber composition for a specific part of the inner liner layer. The present invention has been completed.

That is, the present invention resides in the following (1) to (3).
(1) To 100 parts by mass of a rubber component containing butyl rubber as a main rubber component, 0.1 to 10 parts by mass of thermosetting resin and 0.1 to 1.5 parts by mass of zinc oxide are included. A rubber composition for an inner liner.
(2) The inner liner layer has a two-layer structure of a tire inner surface layer (A) and a carcass side layer (B), and the rubber composition of the above (1) is used as the carcass side layer (B). A pneumatic tire comprising a rubber composition for an inner liner that does not contain a thermosetting resin for the inner surface layer (A).
(3) When the thickness ratio of the tire inner surface layer (A) and the carcass side layer (B) in the inner liner layer is 1 when the thickness of the tire inner surface layer (A) is 1, the carcass side layer (B) The pneumatic tire according to the above (2), wherein the tire has a thickness of 1 to 3.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for inner liners which can improve vulcanization productivity, and a pneumatic tire using the same can be provided, without reducing air retention property and crack resistance.

Hereinafter, embodiments of the present invention will be described in detail for each invention.
The rubber composition for an inner liner of the present invention is 0.1 to 10 parts by mass of a thermosetting resin and 0.1 to 1 part of zinc oxide with respect to 100 parts by mass of a rubber component containing butyl rubber as a main rubber component. It contains 5 parts by mass.

As a rubber component of the rubber composition for an inner liner of the present invention, in order to obtain good air retention characteristics, at least one butyl rubber selected from butyl rubber and halogenated butyl rubber (each alone or in combination) is used as a main rubber component. Among these, the use of halogenated butyl rubber is preferred in order to obtain even better air retention characteristics.
Examples of the halogenated butyl rubber include bromobutyl rubber (Br-IIR), chlorinated butyl rubber (Cl-IIR), and a chlorinated or brominated modified copolymer of a copolymer of isomonoolefin and paramethylstyrene. Among these, it is desirable to use bromobutyl rubber because the vulcanization rate is further improved.

Examples of the thermosetting resin used in the present invention include at least one of a phenol-formaldehyde resin, a metacresol resin, and the like, further improving vulcanization productivity, ensuring crack resistance, and ensuring tackiness. Therefore, it is particularly desirable to use phenol-formaldehyde resin.
In the present invention, the use of a resin other than a thermosetting resin, for example, the use of a thermoplastic resin such as an alicyclic petroleum resin, an alkylphenol-formaldehyde resin, or an aliphatic petroleum resin, provides vulcanization productivity and air retention. It is damaged and is not preferred.
The content of the thermosetting resin is 0.1 to 10 parts by mass, preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the rubber component.
If the content of the thermosetting resin is less than 0.1 parts by mass, the intended effect of the present invention cannot be exhibited. On the other hand, if the content exceeds 10 parts by mass, the crack resistance is significantly reduced. Absent.

The rubber composition for an inner liner of the present invention further contains 0.1 to 1.5 parts by mass of zinc oxide with respect to 100 parts by mass of the rubber component from the viewpoint of both air retention and crack resistance. The The preferable zinc oxide content is desirably 0.5 to 1.0 part by mass.
If the zinc oxide content is 0.1 parts by mass, air retention cannot be ensured. On the other hand, if the zinc oxide content exceeds 1.5 parts by mass, the crosslink density is excessively improved and crack resistance deteriorates. Absent.
In general, the inner liner rubber composition contains about 3 parts by mass of zinc oxide. However, in the present invention, the use of the thermosetting resin and specification of the content range thereof, and the inclusion of zinc oxide are included. By reducing the amount to 0.1 to 1.5 parts by mass, the crack resistance is further improved.

The rubber composition for an inner liner of the present invention preferably further contains sulfur in order to further improve the vulcanization rate.
The sulfur content is preferably 5 parts by mass or less, and more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component.
In addition, when content of sulfur exceeds 5 mass parts, a crosslinking density will improve too much and crack resistance will deteriorate, and it is unpreferable.

The rubber composition for an inner liner of the present invention preferably further contains a vulcanization accelerator for further improvement of the vulcanization speed.
As the vulcanization accelerator that can be used, a thiazole vulcanization accelerator is preferably used, and di-2-benzothiazolyl disulfide (DM) is particularly preferable.
The content of the vulcanization accelerator is preferably 2.5 parts by mass or less, and more preferably 0.5 to 1. parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of further ensuring crack resistance. 5 parts by mass is desirable.
In addition, if the content of the vulcanization accelerator exceeds 2.5 parts by mass, the vulcanization speed becomes too fast, and the production becomes difficult, which is not preferable.

  In the rubber composition for the inner liner of the present invention, in addition to the rubber component, thermosetting resin, zinc oxide, sulfur, and vulcanization accelerator, it is generally used in the tire industry as long as the effects of the present invention are not impaired. A rubber compounding agent to be used, for example, a reinforcing filler such as carbon black, stearic acid, process oil, an anti-aging agent and the like can be appropriately contained.

  In the rubber composition for an inner liner of the present invention configured as described above, 0.1 to 10 parts by mass of thermosetting resin, zinc oxide with respect to 100 parts by mass of a rubber component containing butyl rubber as a main rubber component By containing 0.1 to 1.5 parts by mass, vulcanization productivity can be improved without lowering air retention and crack resistance.

  The pneumatic tire of the present invention can be produced by configuring the rubber composition for an inner liner having the above-described configuration as an inner liner layer of a pneumatic tire according to a conventional method, and ensures further crack resistance of the entire tire. Therefore, the inner liner layer has a two-layer structure of the tire inner surface layer (A) and the carcass side layer (B), and the rubber composition for the inner liner having the above structure is used as the carcass side layer (B). It is preferable to use a rubber composition for an inner liner that does not contain a thermosetting resin for the tire inner surface layer (A).

  In the pneumatic tire of the present invention, when the inner liner layer has a two-layer structure, in order to obtain good adhesion between the tire inner surface layer (A) and the carcass side layer (B), the tire inner surface layer As the rubber composition for the inner liner which does not contain the thermosetting resin used in (A), it is preferable to use the same kind of rubber component, and it is particularly preferable to use the thermosetting resin from the rubber composition for the inner liner of the present invention. It is desirable to use a rubber composition for an inner liner that has a compounding composition that does not contain.

Furthermore, in the inner liner layer in the pneumatic tire of the present invention, the thickness of the carcass side layer (B) is preferably 1 to 3 times the thickness of the tire inner surface layer (A).
If the thickness of the carcass side layer (B) is not equal to or greater than the thickness of the tire inner surface layer (A), the time-shortening effect is thin, and if the thickness exceeds three times, the concern about crack resistance and the tire inner surface layer (A ) Is too thin and difficult to manufacture, which is not preferable.

  In the pneumatic tire having such a configuration, a rubber composition for an inner liner that does not contain a thermosetting resin is used for the tire inner surface layer (A), and heat transfer is delayed during tire vulcanization. By using the rubber composition for the inner liner containing the thermosetting resin having the above-described structure for the carcass side layer (B) that is required to improve the speed, vulcanization production can be performed without reducing air retention and crack resistance. A pneumatic tire capable of improving the performance can be obtained.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to the following Example etc.

[Examples 1-5 and Comparative Examples 1-5]
A rubber composition for an inner liner was prepared by kneading with a Banbury mixer having the formulation shown in Table 1 below.
About the obtained rubber composition for inner liners, vulcanization speed (blow point), air retention, and crack resistance were evaluated by the following evaluation methods.

[Evaluation method of vulcanization speed (blow point)]
A rubber sample (50 × 140 × 9 mm) of unvulcanized rubber was measured for a blow point at 170 ° C. with a blow point measuring device (manufactured by Toyo Seiki Seisakusho), and the value of Comparative Example 1 was indicated as an index. The smaller the value, the better the vulcanization speed.

[Evaluation method of air retention]
The gas permeability coefficient of each rubber composition was measured according to A method (differential pressure method) of JIS K 7126: 2006 “Plastic film and sheet gas permeability test method”, and the gas permeability coefficient of the rubber composition of Comparative Example 1 was determined. The index is shown as 100. A larger index value indicates a smaller gas permeability coefficient and better air retention.

[Crack resistance evaluation method]
In accordance with JIS K 7126-1999, the number of bendings required to reach fracture was measured using a bending fatigue tester (manufactured by Kodaira Seisakusho). The number of bends was expressed as an index by taking the reciprocal of the value of Comparative Example 1 as 100. It shows that it is excellent in crack resistance, so that a numerical value is small.

As is clear from the results of Table 1 above, Examples 1 to 5 that fall within the scope of the present invention impair air retention and crack resistance compared to Comparative Examples 1 to 5 that fall outside the scope of the present invention. No vulcanization rate (vulcanization productivity) was found.
When a comparative example is seen, in Comparative Examples 1-3, it is an illustration at the time of using a thermoplastic resin as a resin, and Comparative Examples 4 and 5 are cases where the content of zinc oxide is outside the scope of the present invention. In this case, it was found that the effect of the present invention cannot be exhibited.

[Examples 6 to 10 and Comparative Examples 6 to 8]
Using the rubber compositions for inner liners of Examples and Comparative Examples prepared in Table 1 above, a two-layer structure having a gauge ratio (thickness ratio) shown in Table 2 below [tire inner surface layer (A), carcass side A pneumatic tire (radial tire for passenger cars, size: 195 / 65R15) having an inner liner layer made of the layer (B)] was made as a prototype.
Each prototype tire obtained was evaluated for tire vulcanization time, air retention, and crack resistance by the following evaluation methods.
These results are shown in Table 2 below.

[Evaluation method of vulcanization speed]
The vulcanization time of the prototype tire was displayed as an index with the value of Comparative Example 6 being 100. The smaller the value, the shorter the vulcanization time and the better the tire vulcanization productivity.

[Evaluation method of air retention]
Each prototype tire was filled with an air pressure of 700 KPa, left in a constant temperature chamber at 60 ° C. for 3 months, and the air pressure after 3 months was measured. The amount of air leakage was indicated as an index with the value of Comparative Example 6 being 100. It shows that it is excellent in air retention property, so that a numerical value is small.

[Crack resistance evaluation method]
After each prototype tire was run on a 30000 km drum at an air pressure of 350 KPa, the rim was removed and the inner surface was visually checked for cracks and wrinkles according to the following evaluation criteria.
Evaluation criteria:
○: Visible crack, wrinkle-free ×: Visible crack, wrinkled

As is clear from the results of Table 2 above, the pneumatic tires of Examples 6 to 10, which are within the scope of the present invention, have air retention and crack resistance as compared with Comparative Examples 6 to 8, which are outside the scope of the present invention. It was found that the vulcanization time (vulcanization productivity) was excellent without impairing the properties.
In Comparative Examples 6 to 8, it was found that the pneumatic tire using the inner liner rubber composition in which the inner liner layer is outside the scope of the present invention cannot exhibit the effects of the present invention. .

  In the present invention, vulcanization productivity can be improved without lowering air retention and crack resistance, and therefore, it can be suitably applied to high-load pneumatic tires for passenger cars, trucks, buses, etc. it can.

Claims (3)

  It is characterized by containing 0.1 to 10 parts by mass of a thermosetting resin and 0.1 to 1.5 parts by mass of zinc oxide with respect to 100 parts by mass of a rubber component containing butyl rubber as a main rubber component. Rubber composition for inner liner.   The inner liner layer has a two-layer structure of a tire inner surface layer (A) and a carcass side layer (B). As the carcass side layer (B), the rubber composition of claim 1 is used, and the tire inner surface layer ( A pneumatic tire characterized by using a rubber composition for an inner liner which does not contain a thermosetting resin in A).   When the ratio of the thickness of the tire inner surface layer (A) to the carcass side layer (B) in the inner liner layer is set to 1, the thickness of the carcass side layer (B) The pneumatic tire according to claim 2, wherein is from 1 to 3.