JP2013082280A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire excelling in the long-term adhesiveness of steel cords and coating rubber forming a belt, and having high durability.SOLUTION: The pneumatic tire includes a carcass and the belt disposed on the tire-radially outer side of the carcass, wherein the belt is formed of a layer of the steel cords coated with the coating rubber. In the pneumatic tire, on the tire-radially outer side of the belt, there is arranged a rubber member comprising a rubber composition in which an adsorbent having a moisture absorption amount of 5 mass% or more at 25°C and 50% relative humidity is mixed by 1-30 parts with 100 pts.mass of rubber component. The adsorbent is an adsorbent or the like comprising a low-crystallinity layered clay mineral and an amorphous aluminum silicate compound material.

Description

  The present invention relates to a pneumatic tire including a belt reinforced with a steel cord. More specifically, the present invention relates to a pneumatic tire that maintains the durability of adhesion between a steel cord and rubber covering the cord for a long period of time and improves the durability of the belt.

In recent years, metal reinforcing materials have been used as needed for rubber products such as belts and hoses, as well as tires that support the suspension of automobiles. As a tire, a steel cord reinforced tire using a steel cord as a reinforcing material of at least one of a carcass and a belt has been widely used. In steel cord reinforced tires, it is important to ensure the adhesion between the steel cord and the rubber that covers the cord. If this adhesive layer is destroyed, a fatal tire failure may result. There has been proposed a rubber composition having improved adhesion between the rubber and the rubber (Patent Documents 1 and 2). In addition, in order to enhance the adhesion to rubber and enhance its reinforcing effect, the steel cord may be plated with brass, zinc, etc., and the rubber composition may contain a cobalt salt of an organic acid as an adhesion promoter. Has been done.
However, when a large amount of this organic acid cobalt salt is used, the adhesiveness immediately after vulcanization, that is, the initial adhesiveness is excellent, but the thermal deterioration of the rubber and the generation of water thereby are promoted, or intrusion from the outside. The adhesive layer deteriorates due to the moisture, and there is an inconvenience that the deterioration-resistant adhesiveness is poor. Recently, during vulcanization, it has been found that a moderate amount of moisture is required to form an adhesive layer between the brass plating on the steel cord and the rubber layer, for example, certain organic acid metals except cobalt salts as adhesion promoters. A rubber composition for bonding steel cords containing a salt and a hydrous inorganic salt has been proposed (Patent Document 3).

  In addition, a rubber composition obtained by blending a porous inorganic filler or a flat clay with a tread undercushion rubber disposed inside the tread in the tire radial direction or a base rubber in a tread having a cap / base structure is applied, and the porous Techniques for preventing moisture from entering the belt layer by adsorbing moisture to the porous inorganic filler are known (Patent Documents 4 and 5). However, there is a limit to the hygroscopic ability of the porous inorganic filler. When the porous inorganic filler absorbs moisture to the limit, it is not possible to further prevent moisture from entering the belt layer, and further suppression of moisture penetration is necessary.

  Furthermore, since it is necessary to use a rubber composition in consideration of braking performance, handling stability, noise resistance, riding comfort, fuel efficiency, and the like for the tread, there are certain restrictions on changing the tread composition.

JP 7-32810 A JP-A-4-53845 International Publication No. WO97 / 49776 JP 2000-79807 A JP 2004-284453 A

  The present invention, under the circumstances as described above, prevents moisture from entering the belt layer from the outside of the tire and maintains the durability of adhesion between the steel cord and the rubber covering the cord for a long period of time. It is an object of the present invention to provide a pneumatic tire with improved wet heat durability.

  As a result of intensive studies, the present inventors have found that a pneumatic tire having a belt composed of at least two belt layers composed of a steel cord and a coating rubber covering the cord is disposed outside the belt in the tire radial direction. It has been found that by using a rubber composition having a low water vapor transmission rate for the rubber member, the wet heat durability of the belt layer can be improved, and the present invention has been completed.

  That is, the pneumatic tire of the present invention has an adsorbent (highly hygroscopic) having an adsorption amount of 5% by mass or more at 25 ° C. and 50% relative humidity as a reinforcing filler on a rubber member arranged on the outer side in the tire radial direction of the belt. A rubber composition containing 1 to 30 parts by mass of a filler) per 100 parts by mass of the rubber component is used.

  In a preferred embodiment of the pneumatic tire of the present invention, the rubber member is at least one of a tread undercushion rubber and a base rubber in a tread having a cap / base structure.

According to the present invention, water from the tread surface can be obtained by using a rubber composition having a low water vapor permeability obtained by blending a rubber component with a highly hygroscopic filler in a rubber member disposed outside the belt in the tire radial direction. A pneumatic tire that suppresses permeation of the belt layer and improves the wet heat durability of the belt layer is obtained.
The above tires have a belt layer with a sufficiently high durability even when placed in a poor environment of high temperature and high humidity during transportation and storage, so there are special equipment to adjust the temperature and humidity during transportation and storage. I don't need it. In recent years, the use of spare tires outside the vehicle has increased, but by using the tires of the present invention as spare tires, the durability of spare tires after being stored outdoors for a long period of time is maintained close to that of a new product. can do.

It is sectional drawing which shows one embodiment of the pneumatic tire of this invention.

  The present invention comprises a carcass composed of one or more carcass plies, and a belt composed of at least two belt layers composed of a steel cord and a coating rubber covering the cord on the outer side in the tire radial direction of the carcass, A rubber composition in which an adsorbent (highly hygroscopic filler) having an adsorption amount of 5% by mass or more at 25 ° C. and a relative humidity of 50% is used for a rubber member disposed on the outer side in the tire radial direction of the belt is used. And Here, examples of the rubber member disposed on the outer side in the tire radial direction of the belt include a tread undercushion rubber and a base rubber in a tread having a cap / base structure.

  The rubber composition formed by blending the high adsorptive filler has low water vapor permeability because the high adsorptive filler inhibits moisture permeation. Conventionally, the moisture content in the coating rubber that constitutes the belt layer is increased by the moisture that permeates from the tread surface during long-term storage, especially in high-temperature and high-humidity environments. In particular, at the groove bottom of the tread, the distance from the groove bottom to the belt is a problem. On the other hand, in the tire of the present invention, since the rubber member using the rubber composition having a low water vapor permeability formed by blending the high adsorptive filler is disposed on the outer side in the tire radial direction of the belt, the tread It is possible to suppress the permeation of moisture from the surface, prevent the adhesive force between the steel cord and the coating rubber from being lowered, and improve the durability of the belt.

The high adsorptive filler used in the rubber composition for a rubber member is an adsorbent having an adsorption amount of 5% by mass or more, preferably 10% by mass or more at 25 ° C. and a relative humidity of 50%. The adsorbent that can be used is not particularly limited as long as it has an adsorption amount of 5% by mass or more at 25 ° C. and a relative humidity of 50%. For example, natural imogolite, synthetic tubular aluminum silicate, and recently The developed low crystalline layered clay mineral and amorphous aluminum silicate complex can be preferably mentioned. These may be used alone or in combination of two or more.
When these adsorbents are used as fillers in the rubber composition for rubber members, a rubber composition having a low water vapor permeability and excellent in preventing a decrease in adhesive strength between rubber and a steel cord can be obtained. To improve.

Synthetic tubular aluminum silicate forms a silica-alumina precursor in a solution in which an inorganic silicon compound solution and an inorganic aluminum solution are mixed so as to have a predetermined silicon / aluminum ratio. For example, Japanese Patent Application Laid-Open No. 2001-64010 discloses a manufacturing method of tubular aluminum silicate obtained by collecting and washing solid components generated and precipitated after aging.
Moreover, the imogolite which is a natural tubular aluminum silicate can also be used, and a commercially available thing can be used.

  Next, the amorphous aluminum silicate of the low crystalline lamellar clay mineral and the amorphous aluminum silicate complex is hydrated aluminum silicate, and the low crystalline lamellar clay mineral is a simple substance made of aluminum hydroxide. It is a low crystalline layered clay mineral that shows almost no gibbsite or several layers in the layer direction. This composite is obtained by mixing an inorganic silicon compound solution and an inorganic aluminum solution so as to have a predetermined silicon / aluminum ratio, adjusting the pH, and heating the desalted treatment at 10 ° C. or higher. %, A highly adsorbing substance having the ability to adsorb 45% by mass or more of water vapor, and is disclosed, for example, in WO2009 / 084632.

  Such a highly hygroscopic filler contains some moisture due to its hygroscopicity and water absorption, so this moisture is released during vulcanization and is effective in forming an adhesive layer between the steel cord and the rubber phase. Acts on and improves initial adhesion. In addition, since the highly hygroscopic filler from which moisture has been released prevents the permeation of moisture, in a tire in which a rubber member using a rubber composition blended therewith is disposed outside the belt in the tire radial direction, the belt layer The destruction of the adhesive layer due to the moisture is suppressed, and the adhesion durability of the belt is improved.

  The compounding quantity of these highly hygroscopic fillers is 1-30 mass parts with respect to 100 mass parts of rubber components, Preferably, it is 5-20 mass parts with respect to 100 mass parts of rubber components. If the blending amount of the filler is less than 1 part, the effect of improving the adhesiveness cannot be obtained, and if it is 30 parts or more, the viscosity of the unvulcanized rubber becomes high and the refining workability of the base rubber is deteriorated.

  Although there is no restriction | limiting in particular as a rubber component of the rubber composition for rubber members arrange | positioned on the tire radial direction outer side of the said belt, Natural rubber (NR) and diene type synthetic rubber are mentioned. Here, as the diene-based synthetic rubber, polyisoprene rubber (IR), polybutadiene rubber (BR), styrene / butadiene copolymer rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl type Rubber etc. are mentioned. Examples of the butyl rubber include halogenated butyl rubber such as chlorinated butyl rubber and brominated butyl rubber in addition to butyl rubber (IIR). These rubber components may be used alone or in combination of two or more.

  The rubber component preferably contains 10% by mass or more of butyl rubber, and more preferably 10-50% by mass. When the content of the butyl rubber in the rubber component is less than 10% by mass, the rubber member has a small effect of suppressing the permeation of moisture. When the content exceeds 50% by mass, adjacent rubbers such as belt coating rubbers and caps are used. -Adhesive strength with cap rubber or the like in the tread of the base structure is insufficient, and peeling or the like may occur.

  On the other hand, the belt layer is made of a steel cord and a coating rubber, and is not particularly limited, and those conventionally used for a belt layer of a steel cord reinforced tire can be used. Examples of the rubber component of the rubber composition for the coating rubber include natural rubber and synthetic rubber. Examples of the synthetic rubber include polybutadiene rubber, isoprene rubber, styrene / butadiene copolymer rubber, butyl rubber, halogenated butyl rubber, preferably bromine. Butyl rubber having a paramethylstyrene group (specifically, a copolymer of isobutylene and p-halogenated methylstyrene), ethylene / propylene / diene rubber (EPDM), and the like. The rubber component may be used singly or in combination of two or more. From the viewpoint of adhesiveness with a steel cord and breaking properties of coating rubber, 50 mass of natural rubber and / or isoprene rubber is used. % Or more is preferable.

  Furthermore, various adhesion promoters conventionally used in rubber compositions for steel rubber coating rubber can be appropriately blended with the rubber composition for coating rubber. Examples of the adhesion promoter include organic acid metal salts, RHS (resorcinol-hexamethoxymethylmelamine / silica), and among these, organic acid metal salts are preferable, and cobalt salts of organic acids are particularly preferable. The organic acid may be saturated, unsaturated, linear or branched. Specifically, neodecanoic acid, stearic acid, naphthenic acid, rosin, tall oil acid, oleic acid, linoleic acid, linolenic acid Etc.

  Further, in the rubber composition for a rubber member and the rubber composition for coating used in the tire of the present invention, in addition to the above components, a compounding agent usually used in the rubber industry may be appropriately blended in a normal compounding amount. it can. Specifically, fillers such as carbon black, softeners such as aroma oil, vulcanizing agents, guanidines such as diphenylguanidine, thiazoles such as mercaptobenzothiazole, N, N′-dicyclohexyl-2-benzothiazoli Vulcanization accelerators such as sulfenamides such as rusulfenamide, thiurams such as tetramethylthiuram disulfide, vulcanization accelerators such as zinc oxide, poly (2,2,4-trimethyl-1,2-dihydro Quinoline), amines such as phenyl-α-naphthylamine, anti-aging agents, scorch inhibitors, stearic acid and the like.

  The steel cord constituting the belt layer is preferably plated with brass, zinc, or an alloy containing nickel or cobalt in order to improve the adhesion to the coating rubber, and is plated with brass. Particularly preferred are those to which The Cu content in the brass plating is preferably 75% by mass or less, and more preferably 55 to 70% by mass from the viewpoint of realizing good and stable adhesiveness. In addition, there is no restriction | limiting in particular about the twist structure of a steel cord.

Next, embodiments of the tire of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of the pneumatic tire of the present invention.
The tire shown in FIG. 1 has a pair of left and right bead portions 1 and a pair of sidewall portions 2, and a tread portion 3 connected to both sidewall portions 2, and a bead core embedded in the pair of bead portions 1. A radial carcass 5 extending in a toroidal shape between the four to reinforce these parts 1, 2, and 3, and a belt 6 comprising at least two belt layers disposed on the outer side in the tire radial direction of the carcass 5. Have. The tread portion 3 in the illustrated example includes a cap rubber 7 positioned on the outermost side in the tire radial direction, a base rubber 8 on the inner side in the radial direction, and a tread undercushion rubber 9 on the inner side in the radial direction of the base rubber 8. In the tire of the present invention, the cap rubber 7 and the base rubber 8 may form a single layer, and the tread undercushion rubber 9 may be omitted.

  In the tire of the present invention, it is preferable to use a rubber composition having a low water vapor transmission rate, in which at least one of the base rubber 8 and the tread undercushion rubber 9 is blended with the above-described rubber component and a highly hygroscopic filler. Thereby, the permeation | transmission of the water | moisture content from the tread surface is suppressed, and it prevents that the adhesive force of the steel cord and coating rubber which comprises a belt falls.

  The method for producing the rubber composition for a rubber member to be disposed on the outer side in the tire radial direction of the belt of the tire of the present invention is not particularly limited, and a highly hygroscopic filler is added alone to the rubber component by a commonly performed method, It is obtained by kneading together with other compounding components using a kneading machine such as a Banbury mixer, a roll, an internal mixer, and the like, vulcanized after molding, and used as the rubber member.

  The pneumatic tire of the present invention has high adhesion to a steel cord and is excellent in durability. As a gas filled in the tire, an inert gas such as nitrogen can be used in addition to air.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

Examples 1-4 and Comparative Examples 1-5
Between the belt layer made of steel cord and coating rubber and the tread, a rubber sheet made of a rubber composition of the compounding formulation shown in Table 1 having a width of 158 mm and a thickness of 0.5 mm is attached as a tread undercushion rubber, and the tire Was vulcanized and molded. The tire size is 185 / 60R14. Next, the vulcanized tire is deteriorated by leaving it in a constant temperature and humidity chamber maintained at a temperature of 100 ° C. and a humidity of 95% for 5 weeks to improve the heat resistance deterioration adhesion between the deteriorated steel cord and the coating rubber. It was determined as follows.
Further, the unvulcanized viscosity of each rubber composition was determined as an index of workability.
These results are shown in Table 1.

(1) Heat-resistant deterioration adhesiveness Based on ASTM D4776-1996, the pulling force when the steel cord was pulled out was measured, and Comparative Example 1 was set as 100 and displayed as an index. The larger the index value, the stronger the adhesion between the steel cord and the coating rubber.
(2) Unvulcanized viscosity According to JIS K6300-1994, Mooney viscosity (ML _{1 + 4} , 130 ° C) was measured using L rotor under conditions of preheating 1 minute, rotor operating time 4 minutes, temperature 130 ° C. Comparative example 1 was set as 100 and indicated as an index. The larger this value, the lower the unvulcanized viscosity and the better the workability.

注
＊１ ＢＲ０１〔ＪＳＲ（株）製〕
＊２ Ｎ５５０〔東海カーボン（株）製〕
＊３ 吸湿性充填剤１ イモゴライト（組成ＳｉＯ_２・Ａｉ_２Ｏ_３・２Ｈ_２Ｏ）
＊４ 吸湿性充填剤２ 低結晶性層状粘度鉱物と非晶質アルミニウムケイ酸塩複合体
ハスクレイＨＣ５００〔戸田工業（株）製〕
＊５ アンチゲン６Ｃ〔住友化学（株）製〕
＊６ ノクセラーＮＳ−Ｐ〔大内新興化学工業（株）製〕

* 1 BR01 [manufactured by JSR Corporation]
* 2 N550 [manufactured by Tokai Carbon Co., Ltd.]
* 3 Hygroscopic filler 1 Imogolite (composition SiO ₂ · Ai ₂ O ₃ · 2H ₂ O)
* 4 Hygroscopic filler 2 Low crystalline laminar viscosity mineral and amorphous aluminum silicate complex Hasclay HC500 [manufactured by Toda Kogyo Co., Ltd.]
* 5 Antigen 6C (Sumitomo Chemical Co., Ltd.)
* 6 Noxeller NS-P [Ouchi Shinsei Chemical Co., Ltd.]

  From the examples in Table 1, since a water vapor permeability of the tread undercushion rubber is low by using a rubber composition containing a highly hygroscopic filler for the tread undercushion rubber, the temperature and the high temperature are higher than those of Comparative Example 1. It can be seen that the adhesive strength between the steel cord and the coating rubber after being left in a humidity environment can be improved, and the processability of the rubber composition is also good.

  On the other hand, the tires of Comparative Examples 2 to 5 are rubber compositions in which the rubber composition for the tread undercushion rubber is blended with a highly hygroscopic filler outside the scope of the present invention, and improves the adhesion between the steel cord and the coating rubber. However, a rubber composition having good workability has not been obtained.

  The tire provided with the belt layer of the present invention is excellent in deterioration resistance and can be suitably used as a tire for passenger cars and heavy-duty vehicles.

1 Bead part 2 Side wall part 3 Tread part 4 Bead core 5 Radial carcass 6 Belt 7 Cap rubber 8 Base rubber 9 Tread under cushion rubber

Claims (9)

  A pneumatic structure comprising a carcass made of one or more carcass plies and a belt made of two or more belt layers disposed on the outer side in the tire radial direction of the carcass, wherein the belt layer is made of a steel cord covered with a coating rubber. In a tire, a rubber composition in which 1 to 30 parts of an adsorbent having a moisture absorption amount of 5% by mass or more is added to 100 parts by mass of a rubber component at 25 ° C. and 50% relative humidity on the outer side in the tire radial direction of the belt. A pneumatic tire comprising a rubber member made of a material.   The pneumatic tire according to claim 1, wherein the adsorbent is an adsorbent having an adsorption amount of 15% by mass or more.   The pneumatic tire according to claim 1 or 2, wherein the adsorbent is aluminum silicate.   The pneumatic tire according to claim 3, wherein the adsorbent is natural imogolite.   The pneumatic tire according to claim 3, wherein the adsorbent is a synthetic tubular aluminum silicate.   The pneumatic tire according to claim 3, wherein the adsorbent is a low crystalline layered clay mineral and an amorphous aluminum silicate complex.   The pneumatic tire according to any one of claims 1 to 6, wherein a rubber composition containing 5 to 20 parts by mass of an adsorbent with respect to 100 parts by mass of the rubber component is used for the rubber member.   The pneumatic tire according to claim 1, wherein the rubber member is a tread undercushion.   The pneumatic tire according to claim 1, wherein the rubber member is a base rubber in a tread having a cap-base structure.

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