JP5495152B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition excellent in heat-curing resistance, mechanical fatigue resistance, and heat resistance, and a heavy-duty pneumatic tire using the rubber composition.

  In recent years, the usage of trucks and buses has been reduced by reducing the load on the tires due to speed and load restrictions on expressways, improving the wear resistance of the tread rubber, and also using road tires for road maintenance. Lifespan is gradually increasing. Under the use conditions of such tires, the rubber deteriorates due to the thermal deterioration of the rubber due to the self-heating caused by the running. In addition to tire cushion rubber, belt rubber, casing rubber, and rubber inserted between breaker carcass were effectively designed to prevent deterioration in strength characteristics due to thermosetting.

  On the other hand, in recent rapid economic growth countries in the Asian region, road pavement conditions are worse than in Japan, and tire demand is growing in extremely demanding markets such as high loads and high internal pressure. The rubber aging behavior of a tire under these heavy load use conditions takes a process in which the rubber is softened due to mechanical fatigue from the load caused by running and breaks down. This does not cause a problem if tires are manufactured using rubbers suitable for different use conditions. In this case, however, the stock of many types of rubber materials in a factory increases, resulting in a large variety of production loss.

  In order to solve this problem, conventionally, for tires that are put out in areas where the load is severe, a technique is adopted in which the rubber gauge of the tire cushion rubber is thickened to disperse the load strain. However, this method also causes a certain amount of productivity loss and a significant cost increase, and a tire with high profitability cannot be manufactured.

  Patent Document 1 discloses a rubber containing either natural rubber or a diene synthetic rubber as a rubber composition that achieves high grip performance and steering stability and maintains high grip performance and steering stability even at the end of traveling. A technique in which 0.2 to 2.0 parts by mass of a sulfur component as a vulcanizing agent and 0.1 to 1.5 parts by mass of tetrabenzylthiuram disulfide as a vulcanization accelerator are blended with respect to 100 parts by mass of the component. It is disclosed.

In Patent Document 2, a rubber composition that can be vulcanized in a short time and has a particularly high adhesion to a polyester cord is selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber, and styrene-butadiene rubber. A rubber composition comprising at least one selected rubber component and curable at 100 to 190 ° C., comprising at least one primary selected from sulfur, benzothiazylsulfenamides and mercaptobenzothiazole A technique is disclosed that includes a vulcanization accelerator and at least one secondary vulcanization accelerator selected from zinc dibenzyldithiocarbamate and tetrabenzylthiuram disulfide.
JP 2002-226629 A JP 11-49897 A

  The present invention relates to a rubber composition excellent in heat-curing resistance, mechanical fatigue resistance and heat resistance when traveling on a rough road, and a heavy load pneumatic using the rubber composition as a cushion rubber under the belt layer. Provide tires.

  The present invention relates to 100 parts by mass of a diene rubber component containing 80% by mass or more of natural rubber, 25 to 40 parts by mass of carbon black of N330 to N220 grade in ASTM number, and 1.8 to 2.2 parts by mass of sulfur. A rubber composition containing 0.2 to 0.7 parts by mass of tetrabenzylthiuram disulfide (TBZTD) and 1/3 to 2/3 part of the sulfur content of a sulfenamide vulcanization accelerator. Further, the rubber composition preferably has an initial vulcanization rate T10 of 1.3 to 2.5 in a vulcanization rate meter at 160 ° C.

  The present invention relates to a heavy duty pneumatic tire using the rubber composition as a cushion rubber under a belt layer.

  The present invention relates to 100 parts by mass of an ene rubber component mainly composed of natural rubber, 25 to 40 parts by mass of carbon black of ASTM number N330 to N220 grade, 1.8 to 2.2 parts by mass of sulfur, tetra By incorporating 0.2 to 0.7 parts by mass of benzylthiuram disulfide (TBZTD) and 1/3 to 2/3 parts of the amount of sulfur in the sulfenamide vulcanization accelerator, fracture energy and exothermicity In addition, a rubber composition having excellent overall carbon dispersibility, compression fatigue resistance, vulcanization speed and adhesion to adjacent members can be obtained.

  The present invention relates to 100 parts by mass of a diene rubber component containing 80% by mass or more of natural rubber, 25 to 40 parts by mass of N330 to N220 grade carbon black, 1.8 to 2.2 parts by mass of sulfur, tetrabenzyl It is a rubber composition in which 0.2 to 0.7 parts by mass of thiuram disulfide (TBZTD) and 1/3 to 2/3 parts of the amount of sulfur are compounded with a sulfenamide vulcanization accelerator. Hereinafter, the blending components will be described in detail.

<Rubber component>
In the present invention, the rubber component contains 80% by mass or more of natural rubber. In order to maintain the high breaking strength of the rubber, it is essential that the natural rubber is 80% by mass or more. Other diene rubbers can be mixed with natural rubber, but when natural rubber is less than 80% by mass, the sea-island structure is broken in the mixed state with other diene rubbers, and the continuity of natural rubber components in the sea is lost. Characteristics such as fracture strength cannot be maintained.

  Other diene rubber components include styrene-butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber ( NBR), butyl rubber (IIR) and the like can be used. These rubber components can be used alone or in combination of two or more. The ethylene-propylene-diene rubber (EPDM) is an ethylene-propylene rubber (EPM) containing a third diene component, where the third diene component is a non-conjugated diene having 5 to 20 carbon atoms. 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene and 1,4-octadiene, for example 1,4-cyclohexadiene, cyclooctadiene And cyclic dienes such as dicyclopentadiene, for example, alkenyl norbornene such as 5-ethylidene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5-norbornene and 2-isopropenyl-5-norbornene. In particular, among diene, dicyclopentadiene, 5-ethylidene Such as 2-norbornene can be preferably used.

  The styrene-butadiene rubber is preferably solution-polymerized styrene-butadiene rubber (SBR) having a styrene content of 20 to 60% by weight.

<Carbon black>
The carbon black used in the present invention is an ASTM number of N220 to N330 grade.

In particular, these carbon blacks have a nitrogen adsorption specific surface area of 80 to 130 m ² / g, an iodine adsorption amount of 80 to 150 g / kg, and a DBP oil supply amount of 70 to 130 ml / 100 g. When the nitrogen adsorption specific surface area of carbon black is smaller than 80 m ² / g, the reinforcing effect of the rubber composition is small and the strength of the rubber composition cannot be obtained. On the other hand, when the nitrogen adsorption specific surface area of carbon black is larger than 130 m ² / g, it becomes difficult to disperse carbon black in the rubber composition, and the processability in the tire manufacturing process tends to deteriorate.

  Specifically, carbon black called ISAF-HM, ISAF-LM, ISAF-HS, CF, HAF-LS-SC, HAF-LS, HAF or the like is used.

The carbon black is blended in an amount of 25 to 40 parts by mass with respect to 100 parts by mass of the rubber component.
When the amount is less than 25 parts by mass, the reinforcing effect is small, and when it exceeds 40 parts by mass, the workability is poor and the heat generation is high.

<Vulcanizing agent>
The rubber composition according to the present invention contains 1.8 to 2.2 parts by mass of sulfur as a vulcanizing agent with respect to 100 parts by mass of the rubber component. When the amount of the sulfur component is less than 1.8 parts by mass, the rubber strength of the rubber composition is insufficient. Further, when the composition is used for the cushion rubber of the belt layer, it is extremely less than the amount of sulfur in the rubber composition of the adjacent belt layer or carcass layer. As a result, the sulfur in the rubber of the adjacent belt layer, carcass layer, etc. is transferred to the cushion rubber, and the adhesion between the cords of the belt layer and carcass layer after vulcanization and the covering rubber is lowered. Preferably, the amount of sulfur is in the range of 1.9 parts by mass to 2.1 parts by mass.

  The rubber composition according to the present invention can be used in combination with a sulfur component and an organic peroxide as a crosslinking agent. By using an organic peroxide in combination, a carbon-carbon bond is partially formed in the crosslinked form of the rubber, and properties such as strength and elongation of the rubber can be appropriately adjusted. Although the compounding quantity of an organic peroxide is related with the compounding quantity of sulfur, it is 1.0 mass part or less normally with respect to 100 mass parts of rubber components.

  Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, and 2,5-dimethyl-2,5. -Di (t-butylperoxy) hexane and 2,5-dimethyl-2,5-di (benzoylperoxy) hexane are mentioned.

<Tetrabenzylthiuram disulfide (TBZTD)>
In the rubber composition according to the present invention, 0.2 to 0.7 parts by mass of tetrabenzylthiuram disulfide as a vulcanization accelerator is blended with 100 parts by mass of the rubber component. When the amount of tetrabenzylthiuram disulfide is less than 0.2 parts by mass, the effect of thermal stability of the rubber composition cannot be expected. On the other hand, when the amount of tetrabenzylthiuram disulfide is more than 0.7 parts by mass, the strength of the rubber composition after heat aging tends to decrease.

  The rubber composition according to the present invention is considered to be a rubber composition having a crosslinked structure excellent in heat resistance by using tetrabenzylthiuram disulfide as a vulcanization accelerator together with sulfur as a vulcanization agent. Tetrabenzylthiuram disulfide (TBZTD) is represented by the following formula (1).

  The tetrabenzyl thiuram disulfide (TBZTD) is a vulcanization accelerator having the properties of a monosulfur donor, and forms a monosulfide bond in the vulcanized rubber composition to improve heat resistance and compression resistance. In addition, the initial vulcanization is much faster than the sulfenamide accelerator, and the initial vulcanization of the rubber is accelerated even under conditions in which the heat of vulcanization is difficult to be transmitted to the tire internal members, and sulfur migrates from the rubber in the belt layer and carcass layer. It is possible to suppress this. However, if the amount of tetrabenzylthiuram disulfide is too large, the strength of the rubber is lowered, or scorching due to heat in the production process is generated.

  Some thiuram vulcanization accelerators, such as TMTD, which is a super accelerator, have similar effects to tetrabenzylthiuram disulfide, but many of them are precursors of nitrosamines whose degradation products have an adverse effect on the human body. It cannot be used because it occurs.

  Moreover, although the zinc compound ZTC of TBZTD is a nitrosamine-free vulcanization accelerator, the effect of accelerating vulcanization is stronger than that of TBZTD, and it is very difficult to control scorching in the production process.

<Sulfenamide vulcanization accelerator>
The rubber composition according to the present invention contains a sulfenamide vulcanization accelerator in combination with tetrabenzylthiuram disulfide (TBZTD). Examples of the sulfenamide vulcanization accelerator include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (N-tert-butyl-2-benzothiazylsulfenamide), N, N- And sulfenamide compounds such as dicyclohexyl-2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, and N, N-diisopropyl-2-benzothiazolesulfenamide.

  The ratio (A / S) of the blending amount (A) of the sulfenamide-based vulcanization accelerator and the blending amount (S) of sulfur is adjusted to a range of 1/3 to 2/3. By adjusting to such a range, the properties of the vulcanized rubber can be adjusted in a well-balanced manner in combination with the blending of the sulfenamide vulcanization accelerator used as the combined system.

  In addition, the total compounding amount (AA) of the sulfenamide vulcanization accelerator and the sulfenamide vulcanization accelerator is in the range of 1.2 to 1.8 parts by mass with respect to 100 parts by mass of the rubber component. The ratio (AA / S) to the amount (S) of sulfur is preferably in the range of 1/2 to 1/5.

<Other vulcanization accelerators>
As the rubber composition of the present invention, a third type of vulcanization accelerator can be used in combination with the vulcanization accelerator. For example, thiuram, thiazole, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine, aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators can be included.

  Examples of thiurams include TMTD (tetramethyl thiuram disulfide), tetraethyl thiuram disulfide, tetramethyl thiuram monosulfide, dipentamethylene thiuram disulfide, dipentamethylene thiuram monosulfide, dipentamethylene thiuram tetrasulfide, dipentamethylene thiuram hexasulfide. Further, thiuram compounds such as tetrabutylthiuram disulfide and pentamethylenethiuram tetrasulfide can be used.

  Examples of the thiazole type include MBT (2-mercaptobenzothiazole), MBTS (dibenzothiazyl disulfide), sodium salt of 2-mercaptobenzothiazole, zinc salt, copper salt, cyclohexylamine salt, 2- (2,4-dinitro). Thiazole compounds such as phenyl) mercaptobenzothiazole and 2- (2,6-diethyl-4-morpholinothio) benzothiazole can be used.

  As the thiourea series, for example, thiourea compounds such as thiacarbamide, diethylthiourea, dibutylthiourea, trimethylthiourea, diortolylthiourea and the like can be used.

  Examples of guanidine-based compounds include guanidine-based compounds such as diphenylguanidine, diortolylguanidine, triphenylguanidine, orthotolylbiguanide, and diphenylguanidine phthalate.

  Examples of dithiocarbamate include zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc diamyldithiocarbamate, zinc dipropyldithiocarbamate , Complex salt of zinc pentamethylenedithiocarbamate and piperidine, zinc hexadecyl (or octadecyl) isopropyldithiocarbamate, zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate, piperidine pentamethylenedithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, diamyl Di, such as cadmium dithiocarbamate And the like can be used Okarubamin acid compound.

  As the aldehyde-amine system or aldehyde-ammonia system, for example, an aldehyde-amine system such as an acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, an acetaldehyde-ammonia reaction product, or an aldehyde-ammonia system compound is used. can do.

  As the imidazoline-based compound, for example, an imidazoline-based compound such as 2-mercaptoimidazoline can be used.

  As the xanthate type, for example, a xanthate type compound such as zinc dibutylxanthate can be used.

<Other ingredients>
The rubber composition according to the present invention can contain 1 to 20 parts by mass of an adhesive resin. As the adhesive resin, a rosin resin, a terpene resin, or the like can be used.

  A terpene resin is a polymer of a terpene monomer and a polymer containing a second component in the polymer chain, a styrene terpene resin, a phenol-modified terpene resin, and a hydrogenated terpene resin obtained by hydrogenating these resins. Is included. Terpene resin can be obtained by polymerizing terpene oil obtained from pine tree using Friedel Kraft catalyst. Specifically, α-pinene, β-pinenecamper, dipentene, etc. should be used. Is possible.

  The rosin resin contains a rosin derivative. A rosin derivative can be produced by hydrogenating, disproportionating, duplicating, esterifying, or the like, rosin contained in raw pine yam or tall oil. The rosin ester used in the present invention includes the hydrogenated product. Specifically, pentaerythritol ester, glycerin ester, hydrogenated rosin ester, hydrogenated rosin methyl ester, hydrogenated rosin ethylene glycol ester, hydrogen An added rosin pentaerythritol ester, a hydrogenated rosin ester emulsion, or the like can be used.

  The rubber composition according to the present invention may contain a softener in order to further improve kneading processability. As softeners, petroleum-based softeners such as process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt and petroleum jelly; fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil and coconut oil; tall oil; sub Waxes such as beeswax, carnauba wax, lanolin; linoleic acid, palmitic acid, stearic acid, lauric acid and the like.

  The rubber composition according to the present invention can contain an anti-aging agent. Examples of the antioxidant include amines, phenols, imidazoles, carbamic acid metal salts, waxes and the like.

  The rubber composition according to the present invention can contain a white filler. Specific examples of the white filler include silica, clay, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, and titanium oxide. These may be used alone or in combination of two or more. Can be used. Particularly preferred white fillers are silica, clay, aluminum hydroxide, and alumina.

  When the white filler is contained, a coupling agent can be further contained. A coupling agent is a compound that forms a strong bond at the interface between an organic polymer and an inorganic material. Different types of reactive groups are introduced into the molecule, one chemically bonding with the polymer and the other with the inorganic.

  The rubber composition according to the present invention can contain a plasticizer. As plasticizers, DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (phthalate) Diisodecyl acid), BBP (butylbenzyl phthalate), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate), hydrophthalic anhydride ester, TCP (tricresyl phosphate), TEP (triethyl phosphate), TBP (tributyl phosphate), TOP (trioctyl phosphate), TCEP (tri (chloroethyl phosphate)), TDCPP (tris dichloropropyl phosphate), TBXP (tosibutoxyethyl phosphate), TCPP (tris (β-chloropropyl) phosphate) G), TPP (triphenyl phosphate), octyl diphenyl phosphate, phosphoric acid (trisisopropylphenyl), DOA (dioctyl adipate), DINA (diisononyl adipate), DIDA (diisodecyl adipate), D610A (dialkyl adipate 610), BXA (dibutyl diglycol adipate), DOZ (di-2-ethylhexyl azelate), DBS (dibutyl sebacate), DOS (dioctyl sebacate), acetyl triethyl citrate, acetyl tributyl citrate, DBM (dibutyl maleate), There are DOM (2-ethylhexyl maleate), DBF (dibutyl fumarate), and the like.

  The rubber composition according to the present invention can contain a scorch inhibitor, that is, a vulcanization retarder. A scorch inhibitor is a chemical that is added in a small amount to a compounded rubber to delay the vulcanization speed and correct the premature start of vulcanization. Examples thereof include organic acids such as phthalic anhydride, salicylic acid, and benzoic acid, nitroso compounds such as N-nitrosodiphenylamine, and N-cyclohexylthiophthalimide.

<Initial vulcanization speed>
In the rubber composition of the present invention, when the initial vulcanization speed T10 at 160 ° C. is adjusted to 2.5 minutes or less, migration of sulfur from the adjacent member is suppressed and high adhesiveness is maintained. Particularly at 1.3 minutes or less, vulcanization is too early, co-vulcanization with the adjacent rubber member does not proceed well, and adhesion failure tends to occur, and scorching of the rubber composition is very likely to occur.

<Pneumatic tire>
The rubber composition according to the present invention can be used for rubber between plies of a heavy-duty pneumatic tire or cushion rubber under the belt layer. FIG. 1 shows a right half of a cross-sectional view of a heavy duty pneumatic tire using a rubber composition as a cushion rubber. In FIG. 1, a tire 1 includes a tread portion 7, a pair of sidewall portions 8 extending inward in the tire radial direction from both ends thereof, and a bead portion 3 positioned at an inner end of each sidewall portion 8. . A carcass 10 is formed in a toroidal shape between the bead portions 3 on both sides, and a belt layer 9 that reinforces the tread portion 7 with a tagging effect on the outside of the carcass 10 and on the inside of the tread portion 7. Arranged. The carcass 10 is formed of one or more carcass plies in which a carcass cord is arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator, and the carcass ply extends from the tread portion 7 to the sidewall portion 8. Around the bead core 11 of the bead portion 3 is folded back from the inner side in the tire axial direction to be locked. The belt layer 9 includes two or more belt plies in which belt cords are arranged at an angle of, for example, 30 ° or less with respect to the tire equator, and the belt cords 9 are stacked in different directions so that the belt cords cross each other. .

  A cushion rubber 4 having a width substantially the same as or wider than the width of the belt layer 9 is disposed below the belt layer 9 and above the carcass 10. If necessary, a band layer 5 for preventing lifting of the belt layer 9 may be provided outside the belt layer 9, and at this time, the band layer has an organic fiber cord having a low modulus substantially equal to the tire equator. Formed with continuous plies spirally wound in parallel. A bead apex 6 extending radially outward from the bead core 11 is disposed in the bead portion 3, and an inner liner rubber forming a tire lumen surface is provided adjacent to the inside of the carcass 10. The outside is protected by the chafer 2 adjacent to the rim and the sidewall rubber.

Examples to 4 and Comparative Examples 1 to 12
Based on the blending table shown in Table 1, blending ingredients other than sulfur and the vulcanization accelerator are kneaded for 3 minutes at 160 ° C. with a Banbury mixer, and further sulfur and vulcanization accelerator are added, using an open roll, The mixture was kneaded at room temperature for 5 minutes and turned over 5 times to form a sheet. This was heated using a press at 150 ° C. for 30 minutes to obtain a vulcanized rubber composition.

The details of the ingredients used in Table 1 are as follows.
(Note 1) Natural rubber: SIR20.
(Note 2) SBR1502: Styrene-butadiene rubber manufactured by JSR.
(Note 3) BR150B: Ube Industries' butadiene rubber.
(Note 4) Carbon N220: N220 made by Cabot Japan.
(Note 5) Carbon N330: N330 manufactured by Cabot Japan.
(Note 6) Carbon N134: N134 made by Cabot Japan.
(Note 7) Insoluble sulfur: “Seimisulfa” containing 10% oil
(Note 8) Vulcanization accelerator NS: “Suncellor NS” manufactured by Sanshin Chemical Co., Ltd. (Nt-butylbenzothiazylsulfenamide).
(Note 9) Vulcanization accelerator TBZTD: manufactured by Flexis Corporation.

  In addition, in the compounding table | surface shown in Table 1, the compounding component used in common is as follows.

Zinc oxide (Mitsui Metals Co., Ltd., 2 types) 3 parts by mass Stearic acid (Nippon Yushi Co., Ltd., bead stearic acid “椿”) 2 parts by mass Anti-aging agent RD (Seiko Chemical Co., Ltd.) 1.5 parts by mass Comparative Example It implemented by the following method of the characteristic evaluation of an Example.

<Destruction energy>
A test piece was prepared from a rubber composition sheet vulcanized at 150 ° C. for 30 minutes in accordance with JIS K6251, and a numerical value of strength at break (TB) × elongation at break (TB) × 0.5 was obtained. The value was expressed as an index with the value of 100 being 100. The larger the index, the higher the fracture energy and the better.

<Destruction energy after aging>
The sheet of the rubber composition after vulcanization was heat-aged at 100 ° C. for 72 hours, and then the fracture energy was measured according to JIS K6251. The index was displayed in the same manner as the breaking energy.

<Exothermic>
A test piece was prepared from a rubber composition sheet vulcanized at 150 ° C. for 30 minutes, tan δ was measured with a viscoelastic spectrometer at a temperature of 70 ° C., an initial strain of 2%, and an amplitude of 11%. The index was displayed. The larger the index, the smaller the exothermic property and the better.

<Dispersibility of carbon>
Carbon dispersibility was evaluated by a method in which a rubber thin section was prepared using a microtome according to the ASTM-A method, and the degree of dispersion failure was counted with a microscope. Here, a numerical value of 90% or more is excellent in dispersibility.

<Compression mechanical fatigue>
The compression set was measured based on the JIS K6265 flexometer test, and indexed with Comparative Example 1 as 100. The larger the index, the better.

<Vulcanization speed T10>
Using a curast meter V type manufactured by Nichigo Corporation, the degree of vulcanization was measured at 160 ° C. for 20 minutes and the amplitude angle was 1 °, and the value of T10 was measured. Here, the value of T10 is the time (minutes) until the 10% torque increases from the Mini of the Max-Mini torque width.

<Adhesive strength with adjacent member>
NR 100 parts by mass, carbon black N326 60 parts by mass, zinc oxide 10 parts by mass, anti-aging agent RD 1 part by mass, insoluble sulfur 5.5 parts by mass, vulcanization accelerator DZ 1 part by mass A sheet of the composition (thickness 2 mm) was prepared, and a sheet of the rubber composition (thickness 2 mm) of the comparative example and the example was bonded thereto and vulcanized at 140 ° C. for 60 minutes. The sulfur content of each rubber bonded together was analyzed. If the amount of sulfur transferred was 20% or less, it was described as a circle in Table 1 as having no problem with the adhesive strength, and the problem was described as x.

<Evaluation results>
Comparative Examples 1, 5 and 6 are examples in which the amount of sulfur is outside the scope of the present invention, and Comparative Examples 2 and 3 are examples in which the amount of carbon N220 is outside the scope of the present invention. Comparative Example 4 is an example in which N134 which is not the subject of the present invention is used for carbon black. Comparative Examples 7 and 8 show examples in which the amount of the sulfenamide vulcanization accelerator is outside the scope of the present invention. Comparative Examples 9 and 10 show examples in which the blending amount of the vulcanization accelerator TBZTD is outside the scope of the present invention. Comparative Examples 11 and 12 show examples in which the proportion of natural rubber in the rubber component is less than 80% by mass.

  It is recognized that the rubber compositions of Examples 1 to 4 are comprehensively excellent in breaking energy, exothermic property, carbon dispersibility, compression fatigue property, vulcanization speed, and adhesion to adjacent members.

  The rubber composition of the present invention is excellent in heat resistance, mechanical fatigue resistance and heat resistance. By using the rubber composition for inter-ply rubber or cushion rubber under the belt layer, a heavy-duty pneumatic tire particularly suitable for running on rough roads is provided.

The right half of a sectional view of a heavy duty pneumatic tire is shown.

Explanation of symbols

  1 tire, 2 chafer, 3 bead part, 4 cushion rubber, 5 band layer, 6 bead apex, 7 tread part, 8 side wall part, 9 belt layer, 10 carcass, 11 bead apex.

Claims (2)

  For 100 parts by mass of diene rubber component containing 80% by mass or more of natural rubber, ASTM number N330 to N220 grade carbon black 25 to 40 parts by mass, sulfur 1.8 to 2.2 parts by mass, tetrabenzyl thiuram disulfide A rubber composition containing 0.2 to 0.7 parts by mass of (TBZTD) and 1/3 to 2/3 part of a sulfur compounding amount of a sulfenamide vulcanization accelerator is used as a cushion under the belt layer. Heavy duty pneumatic tire used for rubber. For 100 parts by mass of diene rubber component containing 80% by mass or more of natural rubber, ASTM number N330 to N220 grade carbon black 25 to 40 parts by mass, sulfur 1.8 to 2.2 parts by mass, tetrabenzyl thiuram disulfide 0.2 to 0.7 parts by mass of (TBZTD) and 1/3 to 2/3 part of the amount of sulfur compounded with a sulfenamide vulcanization accelerator, and initial vulcanization at 160 ° C. A heavy-duty pneumatic tire using a rubber composition having a vulcanization speed T10 of 1.3 to 2.5 as cushion rubber under the belt layer .

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