WO2013008787A1 - Rubber composition for tires and pneumatic tire - Google Patents

Abstract

A rubber composition for tires, which contains, as a filler for reinforcing the rubber composition, 1-30 parts by mass of a highly moisture-absorbing filler per 100 parts by mass of the rubber component, said highly moisture-absorbing filler having a moisture absorption of 5% by weight or more at 25˚C at a relative humidity of 60%. A rubber composition which uses, as the highly moisture-absorbing filler, a composite of a low-crystallinity layered clay mineral and an amorphous aluminum silicate salt is suitable for steel cord coating rubbers for belt layers of tires, members that are on the radially outer side of belts in tires, and the like.

Description

Rubber composition for tire and pneumatic tire

TECHNICAL FIELD The present invention relates to a rubber composition suitable for tires, and more specifically, a rubber composition for tires and a steel cord excellent in wet grip performance and wear resistance using a filler having high moisture absorption performance as a reinforcing filler. It is related with the pneumatic tire excellent in adhesiveness.

In recent years, with increasing interest in safety of automobiles, there has been a demand not only for low fuel consumption but also for handling stability. In order to meet such demands, there is a demand for tires that are highly satisfactory in terms of tire performance, such as low heat build-up with reduced rolling resistance, steering stability on wet and dry road surfaces, and wear resistance. In order to meet such demands, improvements have been made to reinforcing fillers and rubber components.
Conventionally, carbon black has been used as a filler for rubber reinforcement. This is because carbon black can impart high wear resistance to the rubber composition, but by using carbon black alone, a rubber composition that balances wet grip performance, wear resistance, and low fuel consumption at a high level is obtained. This is difficult, and silica is used instead of carbon black as an improved method.
In general, silica is incompatible with the polymer, inferior in reinforcing properties, and is poorly dispersed in rubber, resulting in a large Mooney viscosity value and poor extrudability.

In Patent Documents 1 to 3, a rubber component, kM ¹ · xSiO _y · zH ₂ O (in the formula, M is used for the purpose of obtaining a rubber composition having excellent fuel economy and wet grip performance without reducing wear resistance. ¹ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, or an oxide or hydroxide of the metal, k is an integer of 1 to 5, and x is an integer of 0 to 10 , Y is an integer of 2 to 5, and z is an integer of 0 to 10), and a rubber composition for tire treads containing carbon black, silica, and a silane coupling agent is proposed. Yes.

However, the rubber compositions described in Patent Documents 1 to 3 require a relatively large amount of inorganic compound powder in order to obtain sufficient wet grip performance and fuel efficiency improvement effects. Therefore, a tire rubber composition that is further excellent in the balance of wet grip performance, wear resistance, and low fuel consumption has not been obtained.

In order to improve the dispersibility and workability of silica, a silane coupling agent is used (Patent Documents 4 and 5).
However, the coupling efficiency of the silane coupling agent is small, and in order to compensate for this, the amount is increased and blended. However, since the coupling agent is expensive, there is a problem in that the cost increases when the amount of coupling agent is increased.

Patent Document 4 discloses a silane coupling agent containing an alkoxyl group. Silica and alkoxyl group-containing silane coupling agent react during kneading and generate alcohol as a by-product, but usually the reaction is not sufficient, and the reaction proceeds during subsequent extrusion processing, etc., and alcohol is generated, Bubbles become blistered and blisters are generated, which impairs the dimensional stability of the product and inevitably reduces the processing speed to suppress the generation of blisters. If the temperature at the time of kneading is raised, the reaction proceeds more, but if the temperature is raised too much, another problem such as gelation occurs due to vulcanization with sulfur derived from the coupling agent at the same time as the reaction. Further, if the amount of the coupling agent is reduced in order to reduce the generation of alcohol, problems such as an increase in viscosity due to poor dispersion of silica and a decrease in reinforcing properties occur.

Further, Patent Document 6 discloses 100 parts by weight of a sulfur curable elastomer, 10 to 250 parts by weight of particulate precipitated silica, and 0.01 to 1.0 part by weight of organosilicon having a specific structure per 1 part by weight of the silica. A rubber composition comprising a compound (silane coupling agent) and 10 to 250 parts by weight of sodium thiosulfate pentahydrate [Na ₂ S ₂ O ₃ .5H ₂ O] in a temperature range of 140 ° C. to 190 ° C. A method for processing a rubber composition is disclosed, characterized by mixing thermomechanically at a temperature for 1 to 20 minutes.

The technique disclosed in this document is to improve the coupling efficiency of the silane coupling agent by adding sodium thiosulfate pentahydrate, so-called non-pro kneading process without sacrificing the properties of the final product. However, in this method, the increase in viscosity and the decrease in scorch (early vulcanization time) are remarkably unsuitable for practical use.

In addition, tin (Sn) compounds such as fatty acid tin are known as curing catalysts for silicon rubber. Such Sn compounds accelerate the reaction of the silica-silane coupling agent, and at the same time, are undesirable silane coupling agents. The reaction between the comrades is also promoted, and therefore, the bonds between the polymers and the silica also occur, the rubber viscosity increases, and it is not suitable for practical use.

Patent Document 5 discloses that it is effective to add sodium borate to the rubber composition in order to eliminate such problems in the reaction of the silane-silane coupling agent and prevent the generation of blisters during the extrusion process. Is disclosed.

Furthermore, in order to improve fuel economy and grip on wet road surfaces and wear resistance, aluminum silicate containing fine structure allophane and / or imogolite is contained in the rubber composition together with carbon black and / or silica. It has been proposed to let Allophane is a hollow spherical clay mineral having an average diameter of 2 to 20 nm, and imogolite is a hollow tubular clay mineral having an average outer diameter of 1 to 5 nm, an inner diameter of 0.5 to 2.0 nm, and a length of 30 nm to 5 μm. Although a composite is formed and the wet performance is improved, there is a problem in wear resistance (Patent Document 7). In Patent Document 8, a crystalline zeolite having pores with an average particle size of 0.1 to 500 μm and an average pore size of less than 2 nm is blended to adsorb water molecules on ice to improve the friction performance on ice. Sex is not enough.

On the other hand, in a steel cord reinforced tire using a steel cord as a reinforcing material, it is important to ensure the adhesion between the steel cord and the rubber covering the cord. If this adhesive layer is destroyed, it is fatal. Since it causes a tire failure, a rubber composition having improved adhesion between a steel cord and rubber has been proposed (Patent Documents 9 and 10). 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 water-containing inorganic salt has been proposed (Patent Document 11). However, even in such a method, although the improvement effect in the initial adhesiveness and the heat-resistant deterioration adhesiveness is exhibited, the level is not necessarily satisfactory.

Patent Documents 12 and 13 improve the adhesiveness between the steel cord and the rubber by blending a rubber composition with a hygroscopic porous inorganic filler, and Patent Document 14 describes a hygroscopic porous inorganic filler. A rubber composition containing a filler is used for the belt layer to prevent the ingress of moisture from the outside, to suppress wet heat deterioration and improve durability, but it is not sufficient, but further improvement Is desired.

JP 2002-338750 A JP 2003-55503 A JP 2005-213353 A JP-A-8-259736 JP-A-11-269313 JP-A-9-118784 JP 2007-182520 A JP 2000-44732 A JP 7-32810 A Japanese Patent Laid-Open No. 4-53845 International Publication No. WO97 / 49776 JP 2000-7838 A JP 2002-13083 A JP 2000-79807 A

The present invention has been made in view of such circumstances, and a rubber composition for tires and a steel having excellent wet grip performance and wear resistance and excellent extrudability using a filler with high moisture absorption performance as a reinforcing filler. It is an object of the present invention to provide a pneumatic tire with improved durability and excellent adhesion to a cord.

The rubber composition of the present invention is a rubber composition in which an adsorbent having a moisture absorption amount of 5% by mass or more is added as a reinforcing filler at 25 ° C. and a relative humidity of 60%. In particular, it is a rubber composition for tires that uses a low crystalline layered clay mineral and an amorphous aluminum silicate complex, which have been developed in recent years, as fillers.

According to the present invention, a rubber composition excellent in wet grip performance and wear resistance can be obtained, and in a rubber composition containing silane and a silane coupling agent, the reaction efficiency of the silane coupling agent is good and the properties are stable. Thus, a rubber composition for a tire having good extrudability can be obtained. Furthermore, this rubber composition has excellent adhesiveness with a steel cord when used as a steel cord coating rubber.

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

The tire rubber composition of the present invention contains at least a rubber component and a filler having a high moisture absorption performance. Specifically, the moisture absorption performance of the filler is 5% by mass or more at 25 ° C. and 60% relative humidity, and 10% by mass or more, more preferably 15% by mass at 60% relative humidity. preferable.

The reinforcing filler used in the rubber composition of the present invention is not particularly limited as long as it has a moisture absorption amount of 5% by mass or more at 25 ° C. and a relative humidity of 60%. Preferable examples include zeolite, natural imogolite, synthetic tubular aluminum silicate, and a recently developed low crystalline layered clay mineral and amorphous aluminum silicate complex. These may be used alone or in combination of two or more.
Here, the 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, and then removes coexisting ions. For example, JP-A-2001-64010 discloses a production method of tubular aluminum silicate obtained by recovering and washing solid components produced and precipitated after heat 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 then desalinating and heating at 10 ° C. or higher, 25 ° C., A highly adsorptive substance having the ability to adsorb moisture of 15% by mass or more at 20% relative humidity and 40% by mass or more at 60% is disclosed in, for example, WO2009 / 084632. Commercial products can also be purchased.

Next, an application mode of the rubber composition containing at least the filler having high moisture absorption performance of the present invention will be described.
1st form The 1st form discovered that the rubber composition containing at least the filler with high moisture absorption performance showed the tire performance excellent in wet grip property.
The filler of the highly hygroscopic filler used in the rubber composition of this form is a highly adsorptive substance having a performance of adsorbing 15% by mass or more of moisture at 25 ° C. and a relative humidity of 20%, and a relative humidity of 60%. It is preferable that it is 40 mass% or more. When the relative humidity is 20% and the moisture absorption is less than 15% by mass, sufficient wet grip performance cannot be obtained.
The compounding amount of these highly hygroscopic fillers is 1 to 30 parts by mass with respect to 100 parts by mass of the rubber component, and preferably 5 to 20 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount of the filler is within this range, a rubber composition having sufficient wet grip performance can be obtained without deteriorating processability due to an increase in the unvulcanized viscosity.

The tire rubber composition of the present embodiment contains carbon black (C / B) and silica in addition to the hygroscopic filler as a filler, and further uses other fillers used in the rubber composition. be able to.
Carbon black used as a filler is not particularly limited, and for example, SRF, GPF, FEF, HAF, ISAF, SAF, etc. are used, nitrogen adsorption specific surface area (N ₂ SA) is 30 m ² / g or more, and dibutyl phthalate Carbon black having an oil absorption (DBP) of 90 ml / 100 g or more is preferred. By using carbon black, the effect of improving grip performance and fracture resistance is increased, but HAF, ISAF, and SAF, which are excellent in wear resistance, are particularly preferable.
Carbon black may be used alone or in combination of two or more.

Silica preferably has a nitrogen adsorption specific surface area (N ₂ SA) in the range of 100 to 270 m ² / g, particularly preferably 170 to 270 m ² / g. If this specific surface area is less than 100 m ² / g, the wear resistance may be insufficient. On the other hand, if it exceeds 270 m ² / g, a dispersion failure will occur and the low heat build-up, wear resistance and workability will be significantly reduced. It becomes. The nitrogen adsorption specific surface area (N ₂ SA) is a value measured according to ASTM D4820-93 after drying at 300 ° C. for 1 hour.
Examples of such silica include, but are not limited to, precipitated amorphous silica, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), fumed silica, calcium silicate, and aluminum silicate. Of these, precipitated, amorphous, wet-processed, hydrated silica is preferred. The blending ratio when C / B and silica are used in combination can be arbitrarily changed according to the blending purpose.
The amount of silica used in the present embodiment is preferably 30 to 120 parts by mass, more preferably 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. Silica is blended so that the ratio of hygroscopic filler to the hygroscopic filler / silica is in the range of 0.12 to 0.18.

The amount of carbon black used is preferably 80 parts by mass or less with respect to 100 parts by mass of the rubber component, and the total amount of carbon black and silica combined is preferably 120 parts by mass or less. By setting the total amount to 120 parts by mass or less with respect to 100 parts by mass of the rubber component, the wear resistance can be sufficiently improved.

In this tire rubber composition, a silane coupling agent is used together with silica. The silane coupling agent reacts with the silanol group remaining in the silica and the rubber component polymer to act as a bonding bridge between silica and rubber to form a reinforcing phase and improve dispersibility.
Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxysilyl). Ethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltri Methoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilyl Ethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl Methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazole tetrasulfide, etc. Among these, bis (3-triethoxysilylpropyl) tetrasulfide and 3-trimethoxysilyl from the viewpoint of reinforcing effect Propylbenzothiazole tetrasulfide is preferred, and commercially available from Momentive Performance Materials, trademarks “NXT Low-V Silane”, “NXT Ultra Low-V Silane”, “NXT-Z” (3-octanoylthiopropyltriethoxysilane) ) Or Dexsa Si69, Si75, etc. can be used.

In this embodiment, one silane coupling agent may be used alone, or two or more silane coupling agents may be used in combination. The blending amount is selected in the range of 1 to 25 parts by mass with respect to 100 parts by mass of the rubber component in terms of the total amount of silane coupling agent. If the blending amount of the silane coupling agent is within the above range, the effects of the present invention are sufficiently exhibited. A preferred blending amount is in the range of 2 to 15 parts by mass.

The rubber components used in this embodiment are styrene-butadiene rubber, cis-1,4-polyisoprene, low cis-1,4-polybutadiene, high cis-1,4-polybutadiene, ethylene-propylene-diene rubber, butyl rubber, Examples include chloroprene rubber, halogenated butyl rubber, acrylonitrile-butadiene rubber, and natural rubber. Among them, diene rubber, particularly styrene-butadiene rubber is preferable, but not particularly limited thereto. These rubber components may be used alone or in combination of two or more.

In order to improve workability, a maleic acid monoester or an amine compound is added to the tire rubber composition of this embodiment.
The amount of maleic acid monoester or amine compound added is 1-8 parts by weight, preferably 3-5 parts by weight, per 100 parts by weight of the rubber component. If it is less than 1 part by mass, the low viscosity effect cannot be obtained, and if it exceeds 8 parts by mass, the wear resistance is deteriorated.
The maleic acid monoester is preferably a monoester of maleic anhydride and a (poly) oxyalkylene, particularly a polyoxypropylene derivative. By having a polyoxyalkylene group, compatibility with rubber is improved.

Monoesters of maleic anhydride and (poly) oxyalkylene derivatives can be obtained by reacting maleic anhydride with (poly) oxyalkylene derivatives. Examples of the (poly) oxyalkylene derivative include polyoxypropylene lauryl ether, polyoxypropylene myristyl ether, polyoxypropylene decyl ether, polyoxypropylene octyl ether, polyoxypropylene-2-ethylhexyl ether, polyoxypropylene stearyl ether, polyoxypropylene stearyl ether, Polyoxypropylene aliphatic ethers such as oxypropylene oleyl ether; polyoxypropylene aromatic ethers such as polyoxypropylene benzyl ether, polyoxypropylene alkylphenyl ether, polyoxypropylene benzylated phenyl ether, and the like, among these, Polyoxypropylene aliphatic ether is preferred, and polyoxypropylene lauryl ether is particularly preferred.

More preferably, the degree of polymerization of the oxyalkylene unit is 3 to 7, particularly 5, and the alkyl group or alkenyl group has 8 to 18 carbon atoms. Specifically, POA (r) is abbreviated as POA (r), and r is an average degree of polymerization. POA (3) octyl ether, POA (4) 2-ethylhexyl ether, POA (3) decyl ether, POA (5) Decyl ether, POA (3) lauryl ether, POA (5) lauryl ether, POA (8) lauryl ether, POA (1) stearyl ether, POA (5) myristyl ether and the like.
Maleic acid monoesters may be used alone or in combination of two or more.

The amine compound added to the rubber composition of the present embodiment is not particularly limited, and examples thereof include N, N-dimethyl-n-octadecylamine, N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylene. Amine-ketone such as diamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline, reaction product of diphenylamine and acetone Compounds, phenyl-1-naphthylamine, octylated diphenylamine, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine, p- (p-toluenesulfonylamido) diphenylamine, N, N′-di-2-naphthyl -P-ferylenediamine, N, N'-diphenyl-p-ferylenediamine, N-phenyl-N'-isopropyl And ru-p-ferenediamine, N-phenyl-N '-(3-methacryloyloxy-2-hydroxypropyl) -p-ferenediamine, and the like. Among these, N, N-dimethyl-n-octadecylamine is preferable. These amine compounds may be used alone or in combination of two or more.

In the tire rubber composition of the present embodiment, as long as the object of the present invention is not impaired, a compounding agent usually used in the rubber industry, for example, a vulcanizing agent, a vulcanization accelerator, a process oil, an anti-aging agent is used. Agent, scorch inhibitor, zinc white, stearic acid and the like.

The manufacturing method of the tire rubber composition of the present embodiment is not particularly limited, and a hygroscopic filler is added to the rubber component alone by a commonly performed method, and together with other compounding components, a Banbury mixer, a roll, an internal mixer It is obtained by kneading using a kneader such as the like, vulcanized after molding, and used as tire rubber.

Second Embodiment A second embodiment of the present invention will be described.
In a rubber composition containing silica and a silane coupling agent, when a specific amount of an inorganic filler with high moisture absorption performance is blended, the reaction efficiency of the silica-silane coupling agent is increased, and other performances are not affected. In addition, generation of blisters can be prevented, and a rubber composition having stable wet properties and excellent properties can be obtained.
The rubber composition of this embodiment is a rubber composition containing silica and a silane coupling agent. The rubber component is 100 parts by mass of a diene rubber, 10 to 100 parts by mass of silica, and 3 to 20 of the silane coupling agent with respect to silica. 1 to 30 parts by mass of an adsorbent having a moisture absorption amount of 5% by mass or more at 25% by mass, 25 ° C. and 60% relative humidity is blended.

As the rubber component used in this embodiment, natural rubber (NR) or diene synthetic rubber can be used alone or in combination. Examples of the synthetic rubber include synthetic isoprene rubber, butadiene rubber (BR), and styrene-butadiene rubber (SBR). Particularly, the rubber component is 20 to 100% by mass of styrene-butadiene rubber (SBR). It is preferable.

As the silica used in this embodiment, those having a nitrogen adsorption specific surface area (N ₂ SA) in the range of 80 to 270 m ² / g are preferably used. If the specific surface area is less than 80 m ² / g, the wear resistance of the rubber composition may be insufficient. On the other hand, if the specific surface area exceeds 270 m ² / g, poor dispersion is caused and the workability is remarkably lowered. 100 to 250 m ² / g is preferable.
The nitrogen adsorption specific surface area (N ₂ SA) is a value measured according to ASTM D4820-93 after drying at 300 ° C. for 1 hour.
Examples of such silica include, but are not limited to, precipitated amorphous silica, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), fumed silica, calcium silicate, and aluminum silicate. Of these, precipitated, amorphous, wet-processed, hydrated silica is preferred. Specifically, nip roll AQ manufactured by Nippon Silica Kogyo Co., Ltd., ULTRASIL VN3, BV3370GR manufactured by Degussa Germany, RP1165NP manufactured by Rhône-Poulenc, Zeosil 165GR, Zeosil 175NP, Hisil 233 manufactured by PPG, Hisil 200, Hisil 255 (all are trade names), but is not particularly limited.
The compounding amount of silica is 10 to 100 parts by mass, preferably 30 to 90 parts by mass with respect to 100 parts by mass of the rubber component. When the amount of silica is less than 10 parts by mass, the wet performance is inferior when the rubber composition is used in a tread of a tire, and when it exceeds 100 parts by mass, the viscosity is excessively increased.

A silane coupling agent is used for the rubber composition of this embodiment. The silane coupling agent reacts with the silanol group remaining in the silica and the rubber component polymer to act as a bonding bridge between silica and rubber to form a reinforcing phase and improve dispersibility. The silane coupling agent is preferably a silane coupling agent containing an alkoxyl group, but is not particularly limited. As the silane coupling agent, the silane coupling agent mentioned in the first embodiment can be used.

The compounding amount of the silane coupling agent is 3 to 20% by mass, preferably 5 to 10% by mass with respect to the silica mass. If the blending amount of the silane coupling agent is less than 3% by mass, the reactivity with silica is insufficient, resulting in poor dispersion of the silica and a decrease in reinforcing property. If it exceeds 20% by mass, the viscosity of the rubber composition increases. Extrusion processability deteriorates.

In this embodiment, an adsorbent having a high hygroscopic performance (high hygroscopic filler) is used to promote the reaction between silica and the silane coupling agent. The moisture absorption performance of the adsorbent is 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more at 25 ° C. and a relative humidity of 60%. If it is less than 5% by mass, the property stability improving effect of the rubber composition in the processing step cannot be obtained.
As the highly hygroscopic filler, those listed above can be used. Among these, silica gel includes A type and B type, and B type is preferred.

The amount of these highly hygroscopic fillers to be blended is 1 to 30 parts by weight, preferably 10 to 20 parts by weight with respect to 100 parts by weight of the rubber component, and the blending ratio with respect to silica, filler / silica ≧ 0. .12. When the blending amount of the filler is less than 1 part by mass, the effect of improving the property stability of the rubber composition in the processing step is insufficient, and when it exceeds 30 parts by mass, the processability deteriorates.
The highly hygroscopic filler increases the reaction efficiency of the silica-coupling agent, but has little effect on other unvulcanized physical properties (viscosity, scorch time) and vulcanized physical properties.

In addition to the rubber component, silica, silane coupling agent, and high hygroscopic filler, the rubber composition of the present embodiment includes, as necessary, a compounding agent that is usually used in the rubber composition, such as carbon black and other fillers. Agents, softeners, anti-aging agents, vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids, stearic acid, zinc white, and the like can be appropriately blended. The anti-aging agent, vulcanization accelerator, and zinc white may be added in either the master batch or the final batch.

Rubber kneading is performed using a commonly used internal mixer or roll. When an internal mixer is used, it is usually kneaded in two or more stages: a stage for mixing a filler (non-pro kneading) and a stage for mixing a vulcanizing agent (pro kneading). The highly hygroscopic filler is desirably mixed at the same stage as the silica, but is not limited thereto. The kneading temperature is not particularly defined, but is preferably 140 ° C. or higher and preferably 180 ° C. or lower for promoting the reaction of the silica-silane coupling agent which is the object of the present invention.

Third Embodiment The third embodiment includes 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, and the belt is a coating rubber. In a pneumatic tire including a layer made of a steel cord coated with an adhesive, an adsorbent having a moisture absorption amount of 5% by mass or more at 25 ° C. and a relative humidity of 60% as a filler for reinforcing the comb with respect to 100 parts of the rubber component A tire using a rubber composition containing 1 to 20 parts as a coating rubber. In particular, when a low crystalline layered clay mineral and an amorphous aluminum silicate composite are used as a filler, a rubber composition excellent in initial adhesion between rubber and steel cord and heat-resistant deterioration adhesiveness is obtained. A tire using a belt layer is a pneumatic tire excellent in durability.

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, it is considered that the highly hygroscopic filler from which moisture is released absorbs moisture generated with the deterioration of the rubber over time, so that breakage of the adhesive layer due to moisture is suppressed and heat resistant deterioration adhesiveness is improved.

The blending amount of these hygroscopic fillers is 1 to 20 parts by mass with respect to 100 parts by mass of the rubber component, and preferably 5 to 10 parts by mass with respect to 100 parts by mass of the rubber component. 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 20 parts or more, the viscosity of the unvulcanized rubber becomes high, and the calendar workability to the steel cord is deteriorated.

As the rubber component in the coating rubber composition used in the tire of this embodiment, natural rubber or synthetic rubber is used. As the synthetic rubber, for example, butadiene rubber, isoprene rubber, styrene / butadiene rubber (SBR), butyl rubber, and halogenated butyl rubber are preferable, and brominated butyl rubber and butyl rubber having a paramethylstyrene group (specifically, isobutylene and p-halogen). Copolymers with methyl styrene), ethylene / propylene / diene rubber (EPDM) and the like can also be mentioned as suitable ones.
The rubber component is selected from natural rubber and the above-mentioned synthetic rubber, and one or more types are appropriately used. It is desirable to use natural rubber as a main component, and the ratio of natural rubber is the resistance to fracture or steel cord. From the viewpoint of adhesiveness, the rubber fraction (mass%) is preferably 50 to 100 mass%, particularly preferably 60 to 100 mass%, and more preferably 100 mass%. Synthetic rubbers other than the natural rubber are desirably blended at a ratio of 50% by mass or less, and the use exceeding 50% by mass lowers fracture resistance and adhesion with a steel cord.

In the rubber composition for coating used in the tire according to the present embodiment, if desired, the various kinds of adhesion promoters conventionally used in the rubber composition for steel cord coating can be appropriately added, so that the initial value when these are conventionally blended can be used. Adhesion and anti-degradation adhesion can be further improved. Preferred examples of the adhesion promoter include metal salts of organic acids, particularly cobalt salts of organic acids. The organic acid may be saturated, unsaturated, linear or branched, such as neodecanoic acid, stearic acid, naphthenic acid, rosin, tall oil acid, oleic acid, linoleic acid, linolenic acid, etc. Is mentioned. In addition, when the metal is polyvalent, a part of the organic acid can be substituted with a compound containing boron, boric acid, aluminum or the like. Specifically, Rhône-Poulenc Manobond and the like can be used.
The compounding amount of the metal salt of the organic acid is preferably 0.1 to 0.2 parts by mass as the metal element content with respect to 100 parts by mass of the rubber.

The coating rubber composition used in this embodiment usually contains sulfur. The sulfur content is preferably in the range of 3 to 8 parts by mass per 100 parts by mass of the rubber component. If this content is less than 3 parts by mass, it is not possible to provide sufficient sulfur for the production of Cu _x S (generated by the reaction of copper and sulfur in the brass plating of the steel cord), which is the source of adhesive strength. , Adhesive strength may be insufficient. Moreover, since Cu _x S is excessively generated when the amount exceeds 8 parts by mass, cohesive failure of the enlarged Cu _x S occurs, the adhesive strength is lowered, and the heat aging resistance as a rubber property tends to be lowered. It is done.

Furthermore, in the coating rubber composition used in the present embodiment, in addition to the above-mentioned components, compounding agents that are usually used in the rubber industry can be appropriately blended in the usual compounding amounts. Specifically, fillers such as carbon black, softeners such as aroma oil, guanidines such as diphenylguanidine, thiazoles such as mercaptobenzothiazole, N, N′-dicyclohexyl-2-benzothiazolylsulfenamide, etc. Sulfenamides, vulcanization accelerators such as thiurams such as tetramethylthiuram disulfide, vulcanization accelerators such as zinc oxide, poly (2,2,4-trimethyl-1,2-dihydroquinoline), phenyl Anti-aging agents such as amines such as -α-naphthylamine.

Among these, fillers such as carbon black are known as reinforcing agents for increasing the tensile strength, breaking strength, tensile stress, hardness, etc. of vulcanized rubber, and improving wear resistance and tensile resistance. Zinc oxide is known as a vulcanization acceleration aid which forms a complex compound with a fatty acid and enhances the vulcanization acceleration effect.

Carbon black used as a filler is not particularly limited, and for example, SRF, GPF, FEF, HAF, ISAF, SAF, etc. are used, nitrogen adsorption specific surface area (N ₂ SA) is 30 m ² / g or more, and dibutyl phthalate Carbon black having an oil absorption (DBP) of 90 ml / 100 g or more is preferred. By using carbon black, the effect of improving the fracture resistance is increased.
Carbon black may be used alone or in combination of two or more.
The amount of carbon black used is preferably 30 to 80 parts by mass, and preferably 45 to 70 parts by mass with respect to 100 parts by mass of the rubber component.

In addition, the steel cord applied to the tire of this embodiment is preferably plated with brass, zinc, or an alloy containing nickel or cobalt in order to improve adhesion to rubber, particularly brass. What has been plated is suitable. When the Cu content in the brass plating of the steel cord is 75% by weight or less, preferably 55 to 70% by weight, good and stable adhesion can be obtained. In addition, there is no restriction | limiting in particular about the twist structure of a steel cord.

The manufacturing method of the rubber composition for coating used in the tire of the present embodiment is not particularly limited, and a hygroscopic filler is added to the rubber component alone by a commonly performed method, and together with other compounding components, a Banbury mixer, a roll It is obtained by kneading using a kneader such as an internal mixer, vulcanized after molding, and used as tire rubber.

Fourth aspect The fourth aspect is a pneumatic tire provided with a belt composed of at least two belt layers composed of a steel cord and a coating rubber covering the cord, and a rubber disposed on the outer side in the tire radial direction of the belt. By using a rubber composition having a low water vapor transmission rate as a member, the pneumatic tire has suppressed moisture permeation from the tread surface and improved the wet heat durability of the belt layer.

The present embodiment includes a carcass made of one or more carcass plies, and a belt made of at least two belt layers made 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 a highly hygroscopic filler having an adsorption amount of 5% by mass or more at 25 ° C. and a relative humidity of 60% is used in a rubber member arranged on the outer side in the tire radial direction of the belt. 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 above rubber composition has a low water vapor permeability because the highly adsorbent filler inhibits the permeation of moisture. 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 according to this embodiment, 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. 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 has an adsorption amount of 5% by mass at 25 ° C. and 60% relative humidity, preferably 5% by mass at 50%, more preferably 10% by mass or more. Is an adsorbent. The adsorbent that can be used only needs to have an adsorption amount of 5% by mass or more at 25 ° C. and a relative humidity of 60%, and the above-described highly adsorbent fillers can be used. 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.

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 blending amount of these highly hygroscopic fillers is 1 to 30 parts by mass with respect to 100 parts by mass of the rubber component, and preferably 5 to 20 parts by mass with respect to 100 parts by mass of the rubber component. 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.

The rubber component of the rubber composition for a rubber member disposed on the outer side in the tire radial direction of the belt is not particularly limited, and examples thereof include natural rubber (NR) and diene synthetic rubber. 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 a belt layer 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 cord 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 them, 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.

Moreover, in the rubber composition for rubber members and the rubber composition for coating used in the tire of this embodiment, in addition to the above-mentioned 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 according to the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of the pneumatic tire of the present embodiment.
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 this embodiment, 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 arranged on the outer side in the tire radial direction of the belt of the tire of the present embodiment 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.

A tire using the rubber composition of the present invention is produced by a usual method. That is, a rubber composition containing various compounding agents is processed into a tire at an unvulcanized stage, and is pasted and molded by a normal method on a tire molding machine to form a raw tire. The green tire is heated and pressed in a vulcanizer to obtain a tire.
As a gas filled in the tire, an inert gas such as nitrogen can be used in addition to air.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 to 4 and Comparative Examples 1 to 8
A rubber composition having a formulation according to Table 1 was prepared by kneading with a Banbury mixer.
In Examples and Comparative Examples, the viscosity of the unvulcanized rubber composition, the tire wet performance, and the wear resistance of the obtained rubber composition were measured and evaluated by the following methods.
The results are shown in Table 1.

(1) 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.
(2) Wet performance A pneumatic tire having a tire size of 195 / 60R15 was prototyped using each rubber composition as a tread rubber. The prototype tire was mounted on four wheels of a passenger car with a displacement of 2000 cc, and the brake stop distance was measured on the wet evaluation road of the test course. The measured value was displayed as an index with Comparative Example 1 as 100. The larger this value, the better the wet performance.
(3) Abrasion resistance A pneumatic tire having a tire size of 195 / 60R15 was prototyped using each rubber composition as a tread rubber. The prototype tire was mounted on four wheels of a passenger car with a displacement of 2000 cc, and after traveling 10,000 kilometers on the road surface, the remaining groove amount was measured. The measured values were displayed as an index with Comparative Example 1 being 100. It shows that abrasion resistance is so favorable that an index | exponent is large.

Note * 1 JSR, E-SBR, # 1723
* 2 N134 (N ₂ SA: 146 m ² / g)
* 3 Nippon Silica Kogyo Co., Ltd., nip seal AQ, BET surface area = 210 m ² / g
* 4 Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
* 5 Hygroscopic filler 1: Silica gel (Type B)
* 6 Hygroscopic filler 2: Low crystalline layered clay mineral and amorphous aluminum silicate complex (Hasclay HC500) [manufactured by Toda Kogyo Co., Ltd.]
* 7 Workability improver 1: Maleic acid mono (polyoxypropylene lauryl ether) ester * 8 Workability improver 2: N, N-dimethyl-n-octadecylamine * 9 N-isopropyl-N'-phenyl-p- Phenylenediamine * 10 Dibenzothiazyl disulfide * 11 N-cyclohexyl-2-benzodiazolesulfenamide

From the results shown in Table 1, the rubber composition of the present invention in which a hygroscopic filler is blended improves the workability, wet performance, and wear resistance in a well-balanced manner compared to the rubber composition outside the scope of the present invention. You can see that

Examples 5 to 13 and Comparative Examples 9 to 16
A rubber composition having a formulation according to Tables 2 and 3 was prepared by kneading with a Banbury mixer.
Various physical properties of each rubber composition obtained in Examples and Comparative Examples were evaluated by the following measuring methods. The results are shown in Tables 2 and 3.
(4) Generation | occurrence | production of blister About 10 mm-thick kneaded material | dough was left still for 15 minutes in 120 degreeC oven, and generation | occurrence | production of the blister was evaluated visually. The evaluation was made on a 10-point scale, where 1 was the number of occurrences of blisters and 10 was the absence of blisters. If it is 3 or less, it is a level at which extrusion work is impossible.
(5) Unvulcanized viscosity Measured by the same method as the measurement of the above (1) unvulcanized viscosity. The larger this value, the lower the unvulcanized viscosity and the better the extrudability.

 

 

Note (Tables 2 and 3)
* 1 JSR, E-SBR, # 1712
* 2 N134 (N ₂ SA: 146 m ² / g)
* 3 Nippon Silica Kogyo Co., Ltd., nip seal AQ, BET surface area = 210 m ² / g
* 4 Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
* 5 Hygroscopic filler 1: Silica gel (Type B)
* 6 hygroscopic filler 2: Zeolite * 7 hygroscopic filler 3: imogolite (composition _{SiO 2 · Ai 2 O 3 ·} 2H 2 O)
* 8 Hygroscopic filler 4: Low crystalline layered clay mineral and amorphous aluminum silicate complex (Hasclay HC500) [manufactured by Toda Kogyo Co., Ltd.]
* 9 N-isopropyl-N'-phenyl-p-phenylenediamine * 10 Diphenylguanidine * 11 Dibenzothiazyl disulfide * 12 N-cyclohexyl-2-benzodiazolesulfenamide

From the results shown in Tables 2 and 3, it can be seen that the rubber composition containing the highly hygroscopic filler suppresses the generation of blisters without significantly affecting the rubber properties.

Examples 14 to 17 and Comparative Example 17
A rubber composition having a formulation according to Table 4 was prepared by kneading with a Banbury mixer.
About the obtained rubber composition, initial adhesiveness and heat-resistant deterioration adhesiveness were measured by the following method. The results are shown in Table 4.

(6) Initial adhesiveness Steel cords (1 × 5 structure, wire diameter 0.25 mm) plated with brass (Cu: 63 wt%, Zn: 37 wt%) are arranged in parallel at 12.5 mm intervals. Is coated with a sheet made of each rubber composition from both sides, and vulcanized under conditions of 160 ° C. × 20 minutes to produce a sample having a thickness of 12.5 mm, in accordance with ASTM-D-2229, The steel cord was pulled out, the pulling force at that time was measured, and the value of Comparative Example 17 was taken as 100 and displayed as an index. The larger the value, the better.
(7) Heat-resistant deterioration adhesiveness In the same manner as (6) above, vulcanization was carried out under the conditions of 160 ° C. × 20 minutes to prepare a sample having a thickness of 12.5 mm, and this was carried out in air at 100 ° C. for 7 days After leaving to deteriorate, the steel cord was pulled out in accordance with ASTM-D-2229, and the pulling force at that time was measured. The larger the value, the better.

Note * 1 Natural rubber RSS # 3
* 2 N330 [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 layered viscosity mineral and amorphous aluminum silicate complex (Hasclay HC500) [manufactured by Toda Kogyo Co., Ltd.]
* 5 N-Isopropyl-N'-phenyl-p-phenylenediamine * 6 Manobond C (active ingredient: 22% as cobalt metal, Rhône-Poulenc trade name)
* 7 N, N'-dicyclohexyl-2-benzothiazolylsulfenamide (Noxeller DZ) [Ouchi Shinsei Chemical Co., Ltd.]

From the results shown in Table 4, the rubber composition for coating of the present invention is excellent in initial adhesiveness and heat-resistant deterioration adhesiveness to steel cords. A tire using this rubber composition for the belt layer has excellent durability.

Examples 18 to 21 and Comparative Examples 18 to 22
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 5 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 5.

(8) Heat-resistant deterioration adhesiveness The pulling force when the steel cord was pulled was measured according to ASTM D4776-1996, and the index was displayed with Comparative Example 18 as 100. The larger the index value, the stronger the adhesion between the steel cord and the coating rubber.
(9) Unvulcanized viscosity Measured by the same method as the measurement of the above (1) unvulcanized viscosity. The larger this value, the lower the unvulcanized viscosity and the better the workability.

* 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 layered 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 5, the use of a rubber composition containing a highly hygroscopic filler for the tread undercushion rubber results in a low water vapor permeability of the tread undercushion rubber. 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 19 to 22 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 rubber composition of the present invention can be suitably used for tire members, particularly tire treads. Moreover, the tire provided with the belt layer 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 (28)

1. In a rubber composition comprising at least one rubber component of natural rubber and diene-based synthetic rubber and silica, 5 mass at 25 ° C. and 60% relative humidity as a highly hygroscopic filler with respect to 100 mass parts of the rubber component. A rubber composition for tires comprising 1 to 30 parts of an adsorbent having a moisture absorption amount of at least%.
2. The tire rubber composition according to claim 1, wherein the adsorbent is an adsorbent having a moisture absorption amount of 15% by mass or more at a relative humidity of 20%.
3. 2. The tire rubber composition according to claim 1, wherein the adsorbent is an adsorbent having a moisture absorption of 15% by mass or more at a relative humidity of 60%.
4. The tire rubber composition according to any one of claims 1 to 3, wherein the adsorbent is a low crystalline layered clay mineral and an amorphous aluminum silicate complex.
5. The tire rubber composition according to claim 3, wherein the adsorbent is silica gel.
6. The tire rubber composition according to claim 3, wherein the adsorbent is aluminum silicate.
7. The tire rubber composition according to claim 6, wherein the adsorbent is zeolite.
8. The tire rubber composition according to claim 6, wherein the adsorbent is natural imogolite.
9. The tire rubber composition according to claim 6, wherein the adsorbent is a synthetic tubular aluminum silicate.
10. The rubber composition for tires according to claim 1 or 2, wherein the amount of silica blended is 30 to 120 parts by mass with respect to 100 parts by mass of the rubber component.
11. The tire rubber according to claim 1, wherein 10 to 100 parts by mass of silica and 3 to 20% by mass of a silane coupling agent are blended with respect to silica with respect to 100 parts by mass of the rubber component.
12. The rubber composition for a tire according to any one of claims 1 to 11, wherein a compounding amount of silica is 0.12 or more by mass ratio with respect to the adsorbent.
13. The rubber composition for tires according to claim 12, wherein the compounding amount of silica is 0.12-0.18 in mass ratio with respect to the adsorbent.
14. The tire rubber composition according to any one of claims 1 to 13, wherein the rubber component contains at least styrene-butadiene rubber.
15. The maleic acid mono (polyoxypropylene lauryl ether) ester is blended in an amount of 1 to 8 parts by mass with respect to 100 parts by mass of the rubber component, according to any one of claims 1 to 2, 4 and 12 to 14. Rubber composition for tires.
16. The tire rubber composition according to any one of claims 11 to 15, wherein 3-octanoylthiopropyltriethoxysilane is blended as a silane coupling agent.
17. In a pneumatic tire comprising a carcass and a belt disposed on the outer side in the tire radial direction of the carcass, the belt including a layer made of a steel cord covered with a coating rubber, a reinforcing filler at 25 ° C. and a relative humidity of 60 %, A pneumatic tire in which a rubber composition in which 1 to 20 parts of an adsorbent having a moisture absorption amount of 5% by mass or more is blended with 100 parts of a rubber component is used as a coating rubber.
18. 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 the tire, a rubber assembly in which 1 to 30 parts of an adsorbent having a moisture absorption amount of 5% by mass or more at 25 ° C. and a relative humidity of 60% is blended on the outer side in the tire radial direction of the belt with respect to 100 parts by mass of the rubber component. A pneumatic tire comprising a rubber member made of the following composition.
19. The pneumatic tire according to claim 17 or 18, wherein the adsorbent is an adsorbent having an adsorption amount of 15% by mass or more.
20. The pneumatic tire according to any one of claims 17 to 19, wherein the adsorbent is a low crystalline layered clay mineral and an amorphous aluminum silicate complex.
21. The pneumatic tire according to any one of claims 17 to 19, wherein the adsorbent is aluminum silicate.
22. The pneumatic tire according to claim 21, wherein the adsorbent is natural imogolite.
23. The pneumatic tire according to claim 21, wherein the adsorbent is a synthetic tubular aluminum silicate.
24. The pneumatic tire according to any one of claims 17 and 19 to 23, wherein a rubber composition containing 5 to 10 parts of an adsorbent with respect to 100 parts of a rubber component is used as a coating rubber.
25. The pneumatic tire according to any one of claims 17 and 19 to 24, wherein the coating rubber is a rubber composition containing 0.1 to 0.2 parts by mass of an adhesion promoter with respect to 100 parts by mass of the rubber component.
26. The pneumatic tire according to any one of claims 18 to 23, wherein a rubber composition containing 5 to 20 parts by mass of an adsorbent with respect to 100 parts by mass of a rubber component is used for the rubber member.
27. The pneumatic tire according to any one of claims 18 to 23 and 26, wherein the rubber member is a tread undercushion.
28. The pneumatic tire according to any one of claims 18 to 23 and 26, wherein the rubber member is a base rubber in a tread having a cap-base structure.

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