JP2005067279A - Tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire with a pad and cushion rubber with superior heat generating property, breakage elongation resistance (settling resistance) and fracture resistance after aging appropriately arranged adjacent to a carcass for improving traveling safety accompanying the enlarged size, especially a tire for a large vehicle and off-the-road tires. <P>SOLUTION: This tire comprises the pad rubber arranged adjacent to the outside of a back-folded carcass part back-folding a bead, and arranged at one part or the entire part of a region above the bead and below a half of the tire height, and the cushion rubber arranged adjacent to the outside of the carcass part and below the belt, and arranged at one part or the entire part of a region from above the half of the tire height to the central part of the tire. At least one of a rubber composition of the pad rubber and the cushion rubber includes 1, 6-hexamethylene-sodium dithiosulfate hydrate, and a bismaleimido compound. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tire that can be suitably used for a large vehicle, off-the-road, etc., and more specifically, a pad (PAD) rubber portion that is liable to cause deterioration in physical properties due to heat generation or distortion during traveling of the tire accompanying an increase in size, and The present invention relates to a tire with improved physical properties of a cushion rubber portion.

  Generally, radial tires for large vehicles and off-the-road vehicles have a general structure as shown in FIG. That is, it consists of a tread portion 2, a pair of side wall portions 3 connected to both sides thereof, and a pair of beads 4. Each of these portions includes a carcass 5 mounted between the embedded beads 4 and a belt 6 made of a plurality of steel cords that reinforce the tread portion 2 outside the carcass 5. The carcass 5 and the belt 6 include a carcass ply layer and a belt ply layer formed by coating a metal reinforcing material such as a steel cord with a covering rubber.

  Further, in a general tire, adjacent to the outside of the folded carcass portion 5a where the bead 4 is rolled back, it extends over a part or all of the region A below the half of the tire height and above the bead 4. Pad rubber with excellent tensile properties is placed. Also, a cushion that is disposed under the belt 6 adjacent to the outside of the carcass portion 5b and has excellent tensile properties even over part or all of the region B extending from more than half of the tire height to the tire center portion O. Rubber is placed.

  By the way, with the increase in size in recent years, in a tire that is heavily loaded, heat generation, distortion, and the like are likely to occur in the outer portion and shoulder portion of the folded portion of the carcass. For this reason, the temperature rise during driving | running | working may be remarkable for the outer part and shoulder part of the folding | turning carcass part of a tire. The pad rubber or cushion rubber disposed in such a portion has a reduced tensile physical property due to a temperature rise, and not only leads to the separation in the rubber, but also causes a decrease in the adhesion of the covering rubber in the nearby carcass ply layer and belt ply layer, Eventually, tires may burst due to such separation. Therefore, 30 to 100 parts by weight of the reinforcing filler and 0.2 to 3 parts of the specific diphenylamine anti-aging agent with respect to 100 parts by weight of the rubber component comprising at least one of natural rubber and synthetic diene rubber. It has been proposed to use a rubber composition containing 0.0 part by weight for a stiffener rubber for reinforcing a bead part or a cushion rubber for reinforcing a belt end (for example, Patent Document 1).

In order to satisfy both problems such as tensile physical properties and heat generation, it is also considered to use high-grade carbon black (ISAF, HAF, etc.).
JP 2001-240701 A

  However, since the deformation load is considerably increased with the recent increase in size of tires, rubber with high sag resistance is required, and the exothermic property of the tire and the rupture / extension resistance and puncture resistance after aging (for example, after running) are required. There is a need for further improvements.

  Accordingly, the subject of the present invention is a pad and cushion rubber which are excellent in heat generation, rupture resistance after aging (sagging resistance) and puncture resistance in order to improve running safety accompanying an increase in size. It is an object to provide tires that are appropriately disposed adjacent to the carcass, particularly tires for large vehicles and off-the-road vehicles.

  The tire according to the present invention is characterized by the configuration or means described in the following (1) to (7).

  (1) Adjacent to the outside of the folded carcass portion where the bead is rolled up, and adjacent to the outside of the carcass portion, and pad rubber disposed in a part or all of the region below the half of the tire height and above the bead. And at least one rubber composition, which is disposed under the belt and disposed in a part or all of the region extending from half or more of the tire height to the center of the tire, is 1,6-hexamethylene A tire comprising both sodium dithiosulfate hydrate and a bismaleimide compound.

(2) The tire as described in (1) above, wherein both the rubber composition of the pad rubber and the cushion rubber contain 1,6-hexamethylene-sodium dithiosulfate hydrate and a bismaleimide compound.
(3) The tire according to (1) or (2), wherein the bismaleimide compound is N, N-diphenylmethane bismaleimide.
(4) The rubber composition contains 0.5 to 3.0 parts by mass of 1,6-hexamethylene-sodium dithiosulfate hydrate with respect to 100 parts by mass of the rubber component, and a bismaleimide type The tire according to any one of (1) to (3) above, wherein the compound is contained in a range of 0.5 to 5.0 parts by mass.
(5) The rubber composition contains carbon black having a nitrogen adsorption specific surface area of 70 to 120 m ² / g in a range of 25 to 50 parts by mass with respect to 100 parts by mass of the rubber component. The tire according to (4) above, wherein

(6) A radial tire for a large vehicle, wherein the tire according to any one of (1) to (5) is used for a large vehicle.
(7) A radial tire for off-the-road, wherein the tire according to any one of (1) to (5) is used for off-the-road.

  As described above, the inventor of the present invention contains an appropriate amount of a heat-resistant crosslinking agent, particularly 1,6-hexamethylene-sodium dithiosulfate hydrate and a bismaleimide compound, preferably N, N-diphenylmethane bismaleimide, in the rubber component. When the rubber member made of the rubber composition is arranged as a pad rubber and a cushion rubber adjacent to the carcass, its exothermic property and resistance to breakage and fracture after aging of the tire or after running for a long time, heavy load, etc. Has been found to be further improved, and the present invention has been completed.

  That is, according to the tire according to the present invention, at least one of the above-described pad rubber and cushion rubber contains both 1,6-hexamethylene-sodium dithiosulfate hydrate and a bismaleimide compound. The pad and the cushion rubber, which are excellent in exothermic property and rupture elongation resistance (sag resistance) and puncture resistance after aging, can be appropriately placed adjacent to the carcass, and increase the running safety of the tire. It is something that can be done.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following embodiments and examples.

  FIG. 1 is a partial cross-sectional view of a tire for a large vehicle. As shown in FIG. 1, in the tire 1 of the present embodiment, it is adjacent to the outside of the folded carcass portion 5 a that is winding the bead 4, and not more than half of the tire height H and above the bead 4. The pad rubber disposed in a part or all of the region A and the region B disposed adjacent to the outside of the carcass portion 5b below the belt 6 and extending from more than half of the tire height H to the tire center O At least one rubber composition with the cushion rubber disposed in part or all contains both 1,6-hexamethylene-sodium dithiosulfate hydrate and a bismaleimide compound.

  That is, the tire 1 according to the present embodiment includes a tread portion 2, a pair of sidewall portions 3 connected to both sides thereof, and a pair of beads 4 like a general large vehicle tire. Each of these parts includes a buried bead 4, a carcass 5 mounted between the other bead 4 (not shown), and a belt layer 6 made of a plurality of steel cords that reinforce the tread portion 3 outside the carcass 5. It has. The carcass and belt are composed of a carcass ply layer and a belt ply layer formed by coating a metal reinforcing member such as a steel cord with a covering rubber. Further, the covering rubber is used by directly covering the surface of a metal reinforcing member such as a steel cord or coating the periphery where the metal cord or the like is woven.

  In the most preferred embodiment of the present invention, the pad rubber and the cushion rubber are rubber compositions containing both 1,6-hexamethylene-sodium dithiosulfate hydrate and a bismaleimide compound. In the present invention, both the pad and the cushion rubber need not be such a rubber composition, and at least one of them may be a rubber molded body made of such a rubber composition.

In the rubber composition of the pad and cushion rubber of the present embodiment, first, the rubber component is not particularly limited, but when used for a tire or the like, a polymer of isoprene, for example, a generally available natural rubber and The rubber component is preferably a rubber component made of at least one selected from synthetic isoprene rubber.
As described above, the rubber component may contain only natural rubber, only synthetic rubber, or both. The synthetic rubber is not particularly limited and can be appropriately selected from known ones according to the purpose. Gen-based rubber is particularly preferable, and among them, styrene-butadiene copolymer (SBR), polyisoprene (IR) ), Polybutadiene (BR), acrylonitrile-butadiene rubber, chloroprene rubber, and butyl rubber can be appropriately selected.

  In the present invention, the rubber composition contains both 1,6-hexamethylene-dithiosulfate hydrate (hereinafter referred to as HTS) and / or bismaleimide compound (hereinafter referred to as BMI) in the rubber component. Is contained.

HTS is a heat-resistant cross-linking agent that provides a thermally stable cross-linked structure as compared to sulfur cross-linking. HTS undergoes radical cleavage by heat during vulcanization and has the structural formula;
A radical [.S- (CH ₂ ) ₆ -S.] Is generated and reacts with a double bond in the polymer.

  Suitable BMIs include N, N′-1,2-phenylenebismaleimide, N, N′-1,3-phenylenebismaleimide, N, N′-1,4-phenylenebismaleimide, N, N '-(-Diphenylmethane) bismaleimide, 2,2-bis [4- (4-maleimidophenoxy) phenyl] propane, bis (3-ethyl-5-methyl-4-maleimidophenyl) methane and the like can be exemplified. It is not necessary to be limited to. Particularly preferred in the present invention is N, N-diphenylmethane bismaleimide.

  In the present invention, the rubber composition contains both the above HTS and BMI. In these components, HTS is in the range of 0.5 to 3.0 parts by mass with respect to 100 parts by mass of the rubber component. And BMI is preferably contained in the range of 0.5 to 5.0 parts by mass.

  In pad and cushion rubber made of a rubber composition containing both HTS and BMI, the deterioration of tensile properties due to heat generation during running is suppressed, and aging is achieved by simultaneously blending both of the above heat-resistant crosslinking agents. Later (for example, after long-term running), break elongation resistance and fracture resistance are improved. When only one of the above HTS and BMI is contained, that is, when these two types are not contained at the same time, curing of the rubber after aging progresses, the degree of elongation at break and the breaking strength are lowered, and the effect of the pad and cushion is exhibited. Disappear. Such a tendency is also seen when the blending amount of HTS and BMI is less than 0.5 parts by mass. Moreover, when the blending amount of the HTS exceeds 3.0 parts by mass and when the blending amount of the BMI exceeds 5.0 parts by mass, an effect commensurate with the cost cannot be expected and the cost tends to be high. .

In the rubber composition for the pad and cushion rubber, the carbon black having a nitrogen adsorption specific surface area in the range of 70 to 120 m ² / g is in the range of 25 to 50 parts by mass, particularly 100 parts by mass of the rubber component. , Preferably in the range of 30 to 45 parts by mass.

In the above carbon black, carbon black used in the normal rubber industry can be blended, but among them, in the carbon black having the above nitrogen adsorption specific surface area, the heat generation property of the rubber is suppressed and reinforced. Demonstrates a satisfactory effect as an agent. If carbon black having a nitrogen adsorption specific surface area of less than 70 m ² / g is used, the effect as a rubber reinforcing agent becomes insufficient. When the nitrogen adsorption specific surface area of carbon black exceeds 120 m ² / g, the heat build-up of the rubber is increased.

Such carbon black is desirably contained in a range of 25 to 50 parts by mass, particularly preferably in a range of 30 to 45 parts by mass with respect to 100 parts by mass of the rubber component. When the blending amount of carbon black is less than 25 parts by mass, the effect as a reinforcing agent is insufficient and the rigidity of the rubber becomes insufficient. When the blending amount of carbon black exceeds 50 parts by mass, the exothermic property of the rubber is high. That is, the elongation at break decreases.
Such carbon black can be appropriately selected from those usually used in the rubber industry. For example, carbon black of various grades such as SRF, GPF, FER, HAF, ISAF and the like can be used.

  The rubber composition in the pad and cushion rubber includes, in addition to the above-described compound, other compounds such as a reinforcing filler such as silica, an inorganic filler such as talc, calcium carbonate and sodium carbonate, Add vulcanization accelerators, anti-aging agents, acid value zinc, stearic acid, ozone degradation inhibitors, process aids such as process oils, plasticizers, softeners, and vulcanization shorteners such as cobalt organic acid salts. Can do. As vulcanization accelerators, M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), CZ (N-cyclohexyl-2-benzothiazylsulfenamide), NS (Nt-butyl) And thiazole vulcanization accelerators such as 2-benzothiazolesulfenamide).

  The rubber composition for the pad and cushion is obtained by kneading using a closed kneader such as a Banbury mixer or a kneader such as an open roll, and is appropriately disposed between the above-described regions on the tire belt layer and the carcass layer. Then, after molding, vulcanization is performed, and the rubber is molded into the tire as pad rubber and cushion rubber in a part of regions A and B shown in FIG.

  In the tire configured to include the pad rubber and the cushion rubber, the heat generation of the pad rubber and the cushion rubber is suppressed to be small, and after the aging, for example, the rubber after running for a long time or running under a heavy load. Curing does not proceed, the breaking strength and breaking elongation are maintained, and the running durability and safety of the tire are improved. For this reason, it is desirable to use for a heavy duty tire and a tire for off-road. The tire of the present invention can be filled with an inert gas such as nitrogen in addition to air.

  Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited to these.

Examples 1 to 13 and Comparative Examples 1 to 3
Natural rubber (NR), carbon black (N219, N330, N110, N550), acid value zinc, stearic acid, anti-aging agent (trade name: SANTOFLEX 6PPD), sulfur, vulcanization accelerator (DZ: N, N′- Dicyclohexyl-2-benzothiazolylsulfenamide: trade name “Noxeller DZG” manufactured by Ouchi Shinsei Kagaku), BMI (N, N′-diphenylmethane bismaleimide: manufactured by Mitsui Chemicals), and HTS (1,6-hexamethylene) -Sodium dithiosulfate hydrate (manufactured by Otsuka Chemical Co., Ltd.) is used to knead the mass parts of each composition shown in Table 1, Table 2 and Table 3 below using a Banbury mixer, and unvulcanized rubber composition The rubber composition is molded as pad rubber and cushion rubber in predetermined areas A and B adjacent to the belt and carcass as shown in FIG. To produce a dual-purpose tires (4000R57).

<Tan δ: tensile physical properties>
A test piece was prepared from the bad rubber and cushion rubber of the manufactured new tire, and the loss tangent (tan δ) was measured with a spectrometer manufactured by Toyo Seiki Co., Ltd. at a temperature of 25 ° C., a frequency of 52 Hz, and a dynamic strain of 2.0%. . The smaller the numerical value, the smaller the hysteresis loss and the better the heat generation.

<Road test>
The manufactured new tire was run for 2000 hours with the front mounted on the vehicle body and 2000 hours with the rear mounted for a total of 4000 hours, and then the tire was removed. Next, a test piece is made from the tire bad rubber and cushion rubber, and the breaking strength and breaking elongation of the tire after the road test are tested together with a new tire with a dumbbell-shaped No. 7 type (JIS-K6251). Carried out. The retention rate of Tb and Eb was calculated from the obtained measured value according to the following formula. Higher retention is better with less decrease in tensile properties.
(Retention ratio) = (Measured value after road test) ÷ (Measured value of new tire) × 100
The results are shown in Table 4.

  From the evaluation of Examples 1 to 8 and Comparative Examples 1 and 2, it can be seen that deterioration in physical properties after aging is suppressed by simultaneously blending HTS and BMI. Moreover, as long as Examples 1 to 6 and Examples 7 and 8 were compared, even if the amount of BMI added was further increased from 5 parts by mass, the improvement in tensile properties was not so much observed. Even when the addition amount of HTS was further increased from 3 parts by mass, the improvement in tensile properties was not so much observed.

Looking at the relationship between the nitrogen adsorption specific surface area of carbon black and the tensile physical properties in Examples 2 and 3 and Examples 12 and 17, the tensile physical properties decrease from when the nitrogen adsorption specific surface area falls below 70 m ² / g. I understand that. Further, it can be seen that when the nitrogen adsorption non-surface area exceeds 120 m ² / g, as seen in Example 16, the rupture strength after aging is gradually affected and the exothermic property of the rubber increases.

  From the relationship between Examples 2, 9, and 10, it can be seen that an appropriate amount of carbon black is 25 to 50 parts by mass. It can be seen that the breaking strength gradually deteriorates when the blending amount of carbon black falls below 25 parts by mass. On the other hand, when the amount exceeds 50 parts by mass, the heat generation tends to increase and the elongation at break tends to decrease.

  The tire according to the present invention is a rubber member comprising a rubber composition containing an appropriate amount of 1,6-hexamethylene-dithiosulfate sodium hydrate and a bismaleimide compound, preferably N, N-diphenylmethane bismaleimide. Are disposed as pad rubber and cushion rubber adjacent to the carcass. In the tire having such a configuration, the rupture elongation and fracture resistance after aging of the tire or after running the load are further improved, so that the industrial applicability as a tire is increased, and a large heavy load is applied. It can be used for heavy duty tires and off-road tires.

FIG. 1 is a half-sectional schematic view of a general heavy vehicle tire.

Explanation of symbols

1 Tire 2 Tread 3 Side wall 4 Bead 5 Carcass 6 Belt A Pad installation area B Cushion rubber installation area

Claims (7)

  Pad rubber that is adjacent to the outside of the folded carcass portion where the bead is wound up and is not more than half of the tire height and part or all of the region above the bead, and the belt adjacent to the outside of the carcass portion At least one rubber composition with a cushion rubber disposed below and part or all of a region extending from half or more of the tire height to the tire center is 1,6-hexamethylene-sodium dithiosulfate A tire comprising both a hydrate and a bismaleimide compound.   2. The tire according to claim 1, wherein the rubber composition of both the pad rubber and the cushion rubber contains both 1,6-hexamethylene-sodium dithiosulfate hydrate and a bismaleimide compound.   The tire according to claim 1 or 2, wherein the bismaleimide compound is N, N-diphenylmethane bismaleimide.   The rubber composition contains 0.5 to 3.0 parts by mass of 1,6-hexamethylene-sodium dithiosulfate hydrate with respect to 100 parts by mass of the rubber component, and 0 to bismaleimide compound. The tire according to any one of claims 1 to 3, wherein the tire is contained in a range of 0.5 to 5.0 parts by mass. The rubber composition contains carbon black having a nitrogen adsorption specific surface area in the range of 70 to 120 m ² / g in a range of 25 to 50 parts by mass with respect to 100 parts by mass of the rubber component. The tire according to claim 4.   A radial tire for a large vehicle, wherein the tire according to any one of claims 1 to 5 is used for a large vehicle.   A radial tire for off-the-road use, wherein the tire according to any one of claims 1 to 5 is used for off-the-road.

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