JP4334300B2 - tire - Google Patents

Description

  The present invention relates to a tire such as a large vehicle or an off-the-road vehicle in which a belt layer or the like is disposed on a radially outer side of a crown portion of a carcass layer, and a belt ply caused by heat generation during long-time traveling or load traveling. This is related to a tire with improved running durability, etc., by eliminating the adhesion failure between the coating rubber and the steel cord in the above with a cushion rubber as an adjacent member.

  Conventionally, in heavy-duty tires such as trailer vehicle tires used for long-distance transportation, further life extension of the tire is required. As shown in the partial half sectional view of FIG. 2, a belt layer of a heavy duty tire represented by such a vehicle tire generally has a carcass layer 12 installed between a pair of left and right bead portions 11 and a tread portion 13. In this structure, a belt layer 14 composed of a plurality of steel cords (corresponding to each other) 15 is provided on the outer peripheral side of the carcass layer 12. The steel cord 15 is rubber-coated to improve the adhesion with the surrounding rubber and extend the life of the tire.

By the way, as a rubber for coating a metal reinforcing member such as a reinforcing steel cord of a tire, 50 parts by weight or more of a reinforcing filler, 5 to 15 parts by weight of zinc oxide, 100 parts by weight of a diene rubber such as natural rubber, 0.1 to 10 parts by weight of organic acid cobalt salt, and other general rubber chemicals are blended as required. Further, it has been proposed to use a rubber composition in which a specific organic sulfur compound and sulfur are blended in a certain weight ratio or more as a belt coating material (for example, Patent Document 1). It is already known to use a polysulfide polymer which is a sulfur compound in the coating rubber composition. For example, at least one rubber component that has a double bond and can be cross-linked to become an elastomer, a polysulfide polymer that is repeated when the average number of sulfur bonds in the repeating unit is more than 2 and 6 or less, carbon A crosslinkable rubber composition composed of black, silicate filler, titanium dioxide, calcium carbonate, and the like has been proposed (for example, Patent Document 2). Thus, in belt ply layers or carcass layers coated with metal such as cords, the vulcanized rubber's destructive properties, heat aging resistance and fatigue proof failure without reducing the adhesion between the rubber and the metal Trying to improve.
JP 2002-80643 A Japanese Patent Laid-Open No. 11-139939

  By the way, in recent years, the severity required for tires has risen and the tire temperature has risen, so there is a tendency for the failure of the adhesion between the steel cord and rubber due to heat during running and heavy loads to shorten the failure life. is there. The adhesiveness of such rubber and steel cord due to heat decreases when the adhesive layer made of copper sulfide is affected by heat generated during running. That is, it is considered that the sulfur in the adhesive layer disappears.

  In order not to reduce the amount of sulfur in the coating rubber layer, (1) a large amount of insoluble sulfur can be blended in advance on the coating rubber side of the steel cord. However, the fracture resistance of such coating rubber is reduced. (2) A steel cord coating rubber is molded from a rubber composition containing a polysulfide compound (polysulfide compound). However, since coating rubber requires fracture durability, generally carbon black has an iodine adsorption amount of 80 to 120 mg / g, a filling amount of 45 to 60 parts by mass, and a total sulfur amount of 4 to 6 parts by mass. Therefore, the exothermic temperature of the coating rubber is increased during running, and although the effect is higher than that of the rubber composition of the above (1), the elimination of sulfur is still large. About the rubber composition of said (1) and (2), adhesion durability cannot be improved, maintaining the fracture resistance in a tire. Furthermore, (3) a large amount of insoluble sulfur is added to the rubber composition of the cushion rubber, which is an adjacent member of the coating rubber, and sulfur is transferred from the cushion rubber to the coating rubber to replenish the coating layer with sulfur components to reduce sulfur. To suppress. However, since the insoluble sulfur alone has a high reactivity, the transition from the cushion rubber to the coating rubber has already occurred during the vulcanization, and the decrease in the amount of sulfur in the coating rubber is suppressed and the initial adhesiveness is improved. Although effective, the amount of sulfur at the time of running is reduced and the suppression effect is not fully seen. Further, due to the high reactivity, the elastic modulus characteristic and heat generation characteristic of the cushion rubber itself are lowered. For this reason, the methods (1) to (3) described above cannot improve the failure life and the like by increasing the adhesion durability of the coating rubber without reducing the fracture resistance of the tire.

  Accordingly, the present invention provides a tire, particularly a large-scale heavy load, which has improved durability and failure life by increasing the adhesion durability of the coating rubber covering the steel cord and the like while maintaining the elastic modulus and heat generation characteristics of the cushion rubber and the like. The object is to provide a heavy duty tire and an off-the-road tire.

  The inventors have solved the running durability of tires, particularly large heavy-duty tires and off-the-road tires, by eliminating poor adhesion of coating rubber used for coating metal such as steel cords in the carcass layer and belt layer of the tire. In order to greatly improve the property and failure life, and to improve the adhesion in such a reinforcing material ply layer, a rubber composition in which a predetermined polysulfide is blended with a cushion rubber adjacent to the carcass layer and the belt layer In addition, if such a coating rubber is placed at a predetermined position on the tire trend following surface and the facility area of the carcass layer, the adhesion durability of the coating rubber is further improved and the tire running durability and the failure life are improved. The present invention has been found to achieve the present invention.

That is, the tire according to the present invention is characterized by the following configuration and structure, thereby achieving the above-described object.
(1) In a tire in which at least one of a carcass layer and a belt layer is formed of a reinforcing material ply layer covered with a coating rubber, and a cushion rubber adjacent to the belt layer and the carcass layer is disposed, When the radial length of the follower surface with the hump part as the end from the part is divided into four equal parts, the perpendicular to the carcass layer is dropped from the follower surface of the first equivalent length from at least the center part. The cushion rubber made of a rubber composition in which a polysulfide compound is blended with a rubber component between a region adjacent to the carcass layer from a position where the tire passes through a padless corner portion to a position of a folded end portion of the carcass. distribution and,
The cushion rubber composition contains carbon black having an iodine adsorption amount of 30 to 60 mg / g in a range of 40 to 55 parts by mass with respect to 100 parts by mass of the rubber component, and the sulfur component of the polysulfide compound is a composition. A tire comprising 20 to 60% by mass of the total amount of sulfur in the tire.

  (2) The cushion rubber is adjacent to the carcass layer from a position where a perpendicular is drawn to the carcass layer from a follow surface having a length equal to 3 parts from the central portion to a position of a folded end portion of the carcass. The tire according to claim 1, wherein the tire is disposed between the regions.

  (3) The cushion rubber is located at a position perpendicular to the carcass layer from the follower surface having a length equal to three minutes from the center, and from the padless corner to the carcass layer. The tire according to (2), wherein the tire is disposed between regions adjacent to the carcass layer.

(4) The polysulfide compound of formula 1 and characterized by having a repeating structure of sulfur (S) and the organic group (Org) represented by _{[- - (S m -Org)} n] The tire according to any one of (1) to ( 3 ) above.
(However, n in Formula 1 is in the range of 1 to 100, and m may be different among n, but the average value in n is in the range of 2 to 6.)

( 5 ) The above cushion rubber has a 100% modulus (M100) in the range of 2.0 to 4.0 MPa and a resilience coefficient (resilience) of 70% or more. 4 ) The tire according to any one of the above.

( 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 ) An off-the-road tire, wherein the tire according to any one of (1) to ( 5 ) is used for off-the-road.

  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 half sectional view of a tire according to the present invention. FIG. 2 is a partial half sectional view of a general tire.

  As shown in FIG. 1, a tire 1 as a preferred embodiment includes a reinforcing material ply layer in which at least one of a carcass layer and a belt layer is covered with a coating rubber, and is adjacent to the belt layer and the carcass layer. Cushion rubber is arranged. That is, the tire 1 has a carcass layer 3 installed between a pair of left and right bead portions 2, and a belt comprising three steel cords (corresponding to each other) 6, 6, 6 on the outer peripheral side of the carcass layer 3 a in the tread 4 portion. The layer 5 is provided. The steel cord 6 has a rubber coating. A cushion rubber 7 is disposed adjacent to the carcass layer 3.

  The tread 4 of the tire 1 is formed from the center portion O to the hump portion H shown in FIG. 1 as a tire follow surface 8, and the follow surface 8 partitions the length of the tire in the radial direction at equal intervals. Can do. And if the dividing points h1, h2 and h3 of the follow surface 8 of each section are taken, the position where a perpendicular is drawn from the follow surface of the first equal length h1 from the center O to the carcass layer 3a Between the region adjacent to the carcass layer 3a up to the position of the end portion 9 of the carcass folded at the bead portion 2 (A to C in the figure), a cushion made of a rubber composition in which a polysulfide compound is blended with a rubber component The rubber 7a is arranged. When the cushion rubber 7a is arranged with the position specified in this way, sulfur is supplied to the coating rubber particularly required in the belt layer 4, and the running durability and failure life of the tire are efficiently improved.

  More preferably, the carcass layer from the position where a perpendicular line is drawn with respect to the carcass layer 3a from the follow surface having a length h3 equal to three from the center portion O to the position of the end portion 9 of the carcass folded at the bead portion 2 The cushion rubber 7a is disposed between the regions adjacent to 3a (B and C in the figure), and more preferably perpendicular to the carcass layer 3a from the follow surface having a length h3 equal to the length 3 from the center O. The cushion rubber 7a is disposed between regions adjacent to the carcass layer 3a (B in the figure) from the position where it is lowered to the position where the perpendicular to the carcass layer 3a is lowered from the padless corner 10.

  When the cushion rubber is provided only between the areas A adjacent to the carcass layer 3a, it exhibits a certain degree of adhesion durability, but has a demerit in that the fracture resistance of the tire itself is deteriorated due to a crack generated from the adjacent belt layer. Come. For this reason, it is desirable to arrange the cushion rubber 7a between the regions B and C while avoiding the region A adjacent to the carcass layer 3a. Further, when the cushion rubber is provided only in the region C adjacent to the carcass layer 3a, the adhesion durability as expected cannot be improved. Therefore, it is particularly desirable to dispose the cushion rubber 7a between the regions B adjacent to the carcass layer 3a.

  The rubber composition of the cushion rubber is formed by blending a rubber component with a polysulfide compound as described above. In the present invention, the rubber component is not particularly limited, but when used for a tire or the like, it is a polymer component of isoprene, for example, a rubber component composed of at least one selected from generally available natural rubber and synthetic isoprene rubber. preferable.

  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 particular, natural rubber and polyisopropylene are preferably used as main components, and these rubbers are preferably used in the rubber component in the range of 90 to 100% by mass from the viewpoint of low heat buildup and fatigue fracture resistance.

The polysulfide compound blended in the rubber composition has a repeating structure of sulfur (S) represented by [— (S _m —Org) _n —] of formula 1 and an organic group (Org). It is preferable. Here, n in Formula 1 is in the range of 1 to 100, and m may be different among n, but the average value in n is in the range of 2 to 6.

  The polysulfide compound has a raw material Mooney viscosity (measured according to JIS K6300 using an L-shaped rotor at a temperature of 100 ° C., a preheating time of 1 minute, and a rotor rotation time of 4 minutes) of 100 or less, preferably 85 or less. Further, it is a polysulfide polymer having a number average molecular weight of 200 to 15000, preferably 1000 to 12000.

The organic group _{(Org), - (CH 2} CH 2 O) q - (CH 2) r -, - (CH 2) r - or is represented by the following formula 1. However, q and r are integers including 0. _{Specifically, HS-CH 2 CH 2 OC} 2 H 4 -OC 2 H 4 - (S 2 -CH 2 CH 2 O) n -C 2 H 4 -SH, and _{- (S x - (CH 2} ) _{r) n} -S _y -, and the like. x and y are different integers included in the category of m.

  Since the above polysulfide compound usually has a large molecular weight and low reactivity compared to sulfur and insoluble sulfur, the transition from cushion rubber to coating rubber is very small in a short period during vulcanization, and it takes a long time due to running. It moves over to coating rubber and can suppress the reduction | decrease of the amount of sulfur over a long term.

  Moreover, in the rubber composition of the cushion rubber, it is desirable to blend ordinary sulfur or insoluble sulfur together with the polysulfide compound from the viewpoint of adding immediate effect. Therefore, the total sulfur component of the sulfur component in the polysulfide compound and the normal sulfur component is 2.4 to 4.0 parts by mass, particularly 2.4 to 3.3 parts per 100 parts by mass of the rubber composition. It is preferable to make it contain in 2 mass parts. When the total sulfur component is less than 2.4 parts by mass, a sufficient amount of sulfur does not migrate from the cushion rubber into the coating rubber, so that the adhesion durability is not improved. On the other hand, if the total sulfur component exceeds 4.0 parts by mass, the elastic modulus and heat generation characteristics at the time of overvulcanization are greatly reduced, and the normal fracture durability of the tire is reduced.

  In the rubber composition, the ratio of the sulfur component contained in the polysulfide compound to the total sulfur component (the sulfur component in the polysulfide compound / percentage of the total sulfur component) is in the range of 20 to 60%, particularly in the range of 20 to 40%. It is preferable to become. If the ratio of the sulfur component is less than 20%, sufficient improvement in adhesion durability cannot be obtained, and if the ratio of the sulfur component exceeds 60%, vulcanization is caused by its low reactivity. A stable cross-linked form cannot be formed at the end, and the elastic modulus and heat generation characteristics of the cushion rubber itself are insufficient, so that the fracture durability of the tire is lowered.

  In the cushion rubber, carbon black usually used in the rubber industry can be blended. Among them, the carbon black is in the range of 40 to 55 parts by mass of carbon black having an iodine adsorption amount in the range of 30 to 60 mg / g, particularly preferably in the range of 30 to 50 mg / g, with respect to 100 parts by mass of the rubber component. Particularly preferably, it is contained in the range of 45 to 51 parts by mass. If the iodine adsorption amount of the carbon black is less than 30 mg / g, the elasticity of the rubber becomes insufficient because the reinforcing property of the carbon black itself is low. On the other hand, when the iodine adsorption amount exceeds 60 mg / g, the exothermic property of the rubber increases. On the other hand, when the blending amount of carbon black is less than 40 parts by mass, the kneading temperature at the time of kneading the rubber becomes insufficient and the elastic modulus of the rubber is insufficient. On the other hand, if the amount of carbon black exceeds 55 parts by mass, its own heat generation becomes high. 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 cushion rubber includes, in addition to the above-mentioned compounds, other compounds, for example, reinforcing fillers such as silica, inorganic fillers such as talc, calcium carbonate and sodium carbonate, and vulcanization accelerators. Anti-aging agents, acid value zinc, stearic acid, ozone deterioration preventing agents, processing aids such as process oil, plasticizers, softeners, and vulcanization shorteners such as cobalt organic acid salts can be added. 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 cushion rubber composition is obtained by kneading using a closed kneader such as a Banbury mixer or a kneader such as an open roll, and is formed by appropriately arranging the above-mentioned regions in the belt layer and the carcass layer of the tire. After processing, it is vulcanized and molded into a tire as cushion rubber 7a.

  In this case, the cushion rubber 7a has a 100% modulus (tensile stress at elongation; measured stress according to JIS K6301-1995; hereinafter referred to as M100) in the range of 2.0 to 4.0 MPa, particularly 2.0. It is preferable to be in the range of -3.0 MPa. When the value of M100 is less than 2.0 MPa, the cushion rubber internal strain increases and heat generation increases. When M100 exceeds 4.0 MPa, the strain in the ply rubber of the belt layer increases and heat generation increases.

  Moreover, it is preferable that the impact resilience coefficient (resilience) of the cushion rubber 7a is 70% or more. If it is less than 70%, the heat generation of the cushion rubber itself is increased.

  In a tire configured to include such a cushion rubber, the elastic modulus and heat generation characteristics of the cushion rubber and the like are maintained, and the adhesion durability of the coating rubber covering the steel cord of the belt layer is increased to drive the tire. Durability and failure life are improved. For this reason, it is desirable to use for a tire for large heavy loads and a tire for off-the-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 27, Comparative Examples 1 and 2
Natural rubber (NR), carbon black [CN (N660) -iodine adsorption amount 36 mg / g, CN (N550) -iodine adsorption amount 43 mg / g, and CN (N330) -iodine adsorption amount 82 mg / g], anti-aging agent (Product name: SANTOFLEX 6PPD, manufactured by FLEXSIS), vulcanization accelerator (DZ: N, N′-dicyclohexyl-2-benzothiazolylsulfenamide: product name “Noxeller DZG” manufactured by Ouchi Shinsei Kagaku), stearic acid , Zinc oxide, insoluble sulfur, polysulfide compound (sulfur component (containing 35% by mass), trade name “Thiocol LP” manufactured by Toray Industries, Inc.) And kneaded to obtain an unvulcanized rubber composition. This rubber composition is formed into a tread belt layer and a cartridge as shown in FIG. Use as a cushion gum in a predetermined area (A through C) of the scum layer, it performs vulcanization, to produce a tire (1800R25). In all of the examples and comparative examples, the natural rubber is 100 parts by mass, the antioxidant is 1 part by mass, the stearic acid is 2 parts by mass, the acid value zinc is 5 parts by mass, and the vulcanization accelerator is 0.8 parts by mass. It is blended in the ratio of parts.

The following test evaluation was performed on the obtained tire, and the results are shown in Table 2.
<Evaluation of 100% modulus (M100) and resilience (RES)>
The cushion rubber portion of the tire was taken out, and M100 (MPa) and RES (%) were measured according to JIS K6301.
<Evaluation of tire running durability>
The tire is measured at a predetermined speed (20 km / hr) at a step load (load: 100% TRA standard, 10 ton internal pressure 800 KPa, load 20% up every 72 hours) until the crown of the tire bursts. .
<Evaluation of adhesion durability in tires>
The traveling durability measurement is stopped in the middle of 320 hours, and the observation and evaluation of the ply rubber covering state of the belt layer in the vicinity of the region B shown in FIG. 1 are performed. Evaluation is evaluated at a stage of 10 points by visual judgment, and the higher the score, the better.

  As shown in the results of Table 2, in Examples 1 to 27, the 100% modulus (M100) and resilience (RES) of the cushion rubber maintain characteristics of a predetermined elastic modulus as in Comparative Examples 1 and 2. . However, in the examples in which the polysulfide compound was blended, results that were generally superior in running durability and adhesion durability were obtained as compared with the comparative examples. Moreover, as seen in Example 18 and Example 22, using a cushion rubber containing a polysulfide compound in the B and C regions of FIG. 1 in the tire, in particular, in the B region, compared to using only the A region. Thus, the effect of improving running durability and adhesion durability is sufficiently seen. Furthermore, when the sulfur component in the polysulfide compound is in the range of 20 to 60% of the total sulfur component, it can be seen that the effect of improving running durability and adhesion durability is surely seen.

  The tire according to the present invention contains a specific polysulfide compound in a cushion rubber disposed adjacent to the belt layer and the carcass layer. In the tire having such a configuration, the running durability is improved, and the covering property of the belt layer on the cord such as the coating rubber is maintained for a long period of time, and the adhesion durability is improved. It can be used for large heavy duty tires and off-the-road tires.

FIG. 1 is a partial half sectional view of a large heavy duty tire according to the present invention. FIG. 2 is a general partial half sectional view of a large heavy duty tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Bead part 3 Carcass layer 4 Tread part 5 Belt layer 6 Steel cord 8 Following surface

Claims (7)

In the tire in which at least one of the carcass layer and the belt layer is made of a reinforcing material ply layer covered with a coating rubber, and the cushion rubber adjacent to the belt layer and the carcass layer is arranged, a hump is formed from the center of the tire tread. From the position where the perpendicular to the carcass layer is lowered from the first surface of the first part of the surface following the length of the first part from the center when the radial length of the surface of the surface following the part is divided into four equal parts. The cushion rubber made of a rubber composition in which a polysulfide compound is blended with a rubber component is disposed between the region adjacent to the carcass layer from the bead through the padless corner of the tire to the position of the folded end of the carcass. and,
The cushion rubber composition contains carbon black having an iodine adsorption amount of 30 to 60 mg / g in a range of 40 to 55 parts by mass with respect to 100 parts by mass of the rubber component, and the sulfur component of the polysulfide compound is a composition. A tire comprising 20 to 60% by mass of the total amount of sulfur in the tire.   The cushion rubber is disposed between regions adjacent to the carcass layer from a position perpendicular to the carcass layer from a follow-up surface having a length equal to three parts from the central portion to a position of a folded end of the carcass. The tire according to claim 1.   The cushion rubber is from the position where the perpendicular to the carcass layer is dropped from the follow surface having a length equal to 3 minutes from the center to the position where the perpendicular is dropped from the padless corner to the carcass layer. The tire according to claim 2, wherein the tire is disposed between regions adjacent to the carcass layer. The polysulfide compound has a repeating structure of sulfur (S) represented by [-(S _m -Org) _n- ] in formula 1 and an organic group (Org). tire according to any one of 1-3.
(However, n in Formula 1 is in the range of 1 to 100, and m may be different among n, but the average value in n is in the range of 2 to 6.) The cushion rubber is in the range of 100% modulus (M100) is 2.0～4.0MPa, to any one of claims 1-4, characterized in that the rebound resilience coefficient (resilience) is 70% or more The described tire. 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. An off-the-road tire, wherein the tire according to any one of claims 1 to 5 is used for off-the-road.

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