JP6561654B2 - Oxygen transport cord and pneumatic tire using the same - Google Patents

Description

  The present invention relates to an oxygen transport cord and a pneumatic tire using the same. More specifically, the present invention relates to an oxygen transport cord having a function of preferentially taking in oxygen and transporting it, and reducing the internal pressure using the oxygen transport cord. The present invention relates to a pneumatic tire that can suppress oxidative deterioration of a belt layer while minimizing the belt layer.

  For example, a heavy duty pneumatic tire used for trucks and buses has a carcass layer including a plurality of carcass cords between a pair of bead portions, and a belt layer on the outer periphery side of the carcass layer in the tread portion. It has an arranged structure. In the pneumatic tire having such a structure, the high-pressure air filled in the tire passes through the inner liner layer to reach the carcass layer, and further passes through the carcass layer to reach the belt layer. Oxygen oxidizes and degrades the belt layer coat rubber.

  When the oxidative deterioration of the belt layer occurs in this way, not only the durability of the pneumatic tire is lowered, but also the casing life as a retread tire is shortened, and there is a problem that the number of retreadable times is reduced.

  On the other hand, it has been proposed that an oxygen absorbent is blended in the inner liner layer and that the oxygen absorbent suppresses the arrival of oxygen to the belt layer and prevents oxidative deterioration of the belt layer (for example, patents). Reference 1). However, in this case, since the absorption effect by the oxygen absorbent is limited, the oxidative deterioration of the belt layer cannot be prevented over a long period.

  In addition, it has been proposed to prevent oxidative degradation of the belt layer by wrapping the belt layer with a thin film of a resin material (see, for example, Patent Document 2). However, in this case, since the adhesion between the thin film and the rubber layer in a state where the tread portion is heated is not necessarily guaranteed, a structure in which the belt layer is wrapped with a thin film of a resin material has not been put into practical use. .

  Furthermore, it has been proposed to prevent oxidative deterioration of the belt layer by discharging air that has passed through the inner liner layer to the outside of the tire using a carcass cord (see, for example, Patent Document 3). However, in this case, oxygen and nitrogen are also discharged to the outside of the tire, which helps to reduce the internal pressure of the pneumatic tire.

JP 2011-20672 A JP 2009-279773 A JP 2007-191090 A

  An object of the present invention is to suppress an oxidative deterioration of a belt layer while minimizing a decrease in internal pressure by using an oxygen transport cord having a function of preferentially taking in and transporting oxygen, and using the oxygen transport cord. The object is to provide a pneumatic tire made possible.

  In order to achieve the above object, an oxygen transport cord of the present invention is characterized in that a surface of a cord body formed by twisting an organic fiber multifilament yarn is coated with a polyimide layer.

  The pneumatic tire of the present invention for achieving the above object is characterized in that an oxygen transport cord in which a polyimide layer is coated on the surface of a cord body formed by twisting an organic fiber multifilament yarn is embedded in the tire. It is what.

  Furthermore, in the pneumatic tire of the present invention for achieving the above object, a carcass layer including a plurality of carcass cords is mounted between a pair of bead portions, and a belt layer is provided on the outer peripheral side of the carcass layer in the tread portion. In the disposed pneumatic tire, at least one oxygen transport cord extending from the vicinity of the belt layer and the carcass layer toward the outer surface of the tire on the outer side in the tire width direction is embedded in a shoulder region of the tread portion, The transport cord has a structure in which a polyimide layer is coated on the surface of a cord body formed by twisting an organic fiber multifilament yarn.

  The oxygen transport cord of the present invention has a structure in which a polyimide layer is coated on the surface of a cord body formed by twisting an organic fiber multifilament yarn, but the polyimide layer transmits oxygen more than nitrogen in the air. It has an easy nature. For this reason, when the oxygen transport cord is embedded in rubber, it has a function of preferentially taking oxygen in the rubber into the cord and transporting it along the longitudinal direction.

  The pneumatic tire in which the oxygen transport cord is embedded in the tire can selectively discharge oxygen to the outside of the tire using the oxygen transport cord as an exhaust path, so that the belt can be used while minimizing a decrease in internal pressure. Oxidative deterioration of the layer can be suppressed.

  More specifically, in a pneumatic tire in which a carcass layer including a plurality of carcass cords is mounted between a pair of bead portions and a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion, the shoulder region of the tread portion It is preferable to embed at least one oxygen transport cord extending from the vicinity of the belt layer and the carcass layer toward the outer surface of the tire on the outer side in the tire width direction. According to such a configuration, oxygen contained in the air that has entered the internal space of the carcass cord can be effectively discharged to the outside of the tire through the exhaust path including the oxygen transport cord. In particular, the shoulder region of the tread portion generates heat due to cyclic deformation during running of the tire, and since the heat generation temperature is higher than other parts, air easily diffuses in the rubber. It is optimal as a discharge route.

  Therefore, when the air filled in the tire passes through the inner liner layer and reaches the carcass layer, oxygen contained in the air is selectively discharged to the outside of the tire through an exhaust path made of an oxygen transport cord. It is possible to suppress oxidative deterioration of the belt layer while minimizing the decrease in internal pressure. As a result, it is possible to increase the number of retreadables by extending the casing life as a retreaded tire.

  In the present invention, it is preferable that the polyimide layer penetrates to 3 to 13 filament layers on the surface side of the cord body. Thereby, the function of selectively transporting oxygen can be sufficiently exhibited.

  Further, it is preferable to coat an adhesive layer made of resorcin, formalin, and latex on the polyimide layer. As a result, sufficient adhesion of the oxygen transport cord to the rubber can be ensured.

  Furthermore, it is preferable that at least one end of the cord body in the longitudinal direction is closed with a polyimide layer. Thereby, the outflow of nitrogen in the air can be more reliably prevented, and the function of selectively transporting oxygen can be sufficiently exhibited.

It is a cross-sectional view showing an oxygen transport cord according to an embodiment of the present invention. It is sectional drawing which expands and shows the X section of FIG. It is explanatory drawing which shows the inflow / outflow of oxygen in the oxygen transport cord of FIG. It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is a side view which shows the pneumatic tire of FIG. It is sectional drawing which expands and shows the principal part of the pneumatic tire of FIG. It is sectional drawing which shows the principal part of the pneumatic tire which consists of other embodiment of this invention. It is a side view which shows the pneumatic tire of FIG. It is a transverse cross section showing an example of the steel cord used for the carcass layer of the pneumatic tire of the present invention. It is a transverse cross section showing other examples of the steel cord used for the carcass layer of the pneumatic tire of the present invention. It is a cross-sectional view showing still another example of the steel cord used for the carcass layer of the pneumatic tire of the present invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 3 show an oxygen transport cord according to an embodiment of the present invention. As shown in FIGS. 1 and 2, the oxygen transport cord 20 has a structure in which a polyimide layer 22 is coated on the surface of a cord body 21 formed by twisting an organic fiber multifilament yarn.

  As the organic fiber multifilament yarn constituting the cord body 21, it is preferable to use nylon 66 fiber or rayon fiber having good adhesiveness. The total fineness of the cord main body 21 is set in a range of 800 dtex to 4000 dtex, for example, and the fineness of each filament is set in a range of 1.5 dtex to 10 dtex, for example, but is not limited to these ranges.

  In the oxygen transport cord 20 described above, the polyimide layer 22 has a property of allowing oxygen to permeate more easily than nitrogen in the air. Therefore, when the oxygen transport cord 20 is embedded in rubber, the oxygen transport cord 20 has a function of preferentially taking oxygen in the rubber into the oxygen transport cord 20 and transporting it along the longitudinal direction.

When such an oxygen transport cord 20 is embedded in the rubber of a pneumatic tire, as shown in FIG. 3, in the region Ain close to the tire cavity and having a high oxygen concentration, oxygen in the air ( O ₂ ) is taken in, the oxygen moves along the longitudinal direction of the oxygen transport cord 20 through the filaments, and oxygen (O ₂ ) from the oxygen transport cord 20 in the region Aout near the tire outer surface and where the oxygen concentration is low. Is released. Therefore, oxygen can be selectively discharged outside the tire using the oxygen transport cord 20 as an exhaust path.

  In the oxygen transport cord 20, the polyimide layer 22 may penetrate to 3 to 13 filament layers on the surface side of the cord body 21. Thereby, the function of selectively transporting oxygen can be sufficiently exhibited. Here, when the penetration of the polyimide layer 22 into the cord body 21 is less than three layers, not only oxygen in the air but also nitrogen penetrates the polyimide layer 22, so that the action of selectively transporting oxygen is lowered. To do. Further, when the penetration of the polyimide layer 22 into the cord body 21 is more than 13, the function as an exhaust passage is deteriorated because air containing oxygen and nitrogen is difficult to permeate the polyimide layer 22. The number of penetration layers of the polyimide layer 22 into the cord main body 21 is determined by measuring the thickness of the polyimide layer 22 at eight locations on the circumference of the oxygen transport cord 20 and obtaining the average thickness. It is specified by the ratio of the thickness to the filament diameter.

  As shown in FIGS. 1 and 2, in the oxygen transport cord 20, an adhesive layer 23 made of resorcin / formalin / latex (RFL) is coated on the polyimide 22 layer. Thereby, the adhesiveness with respect to the rubber | gum of the oxygen transport cord 20 can fully be ensured. Such coating of the adhesive layer 23 is a normal adhesion process performed on the tire cord, but the adhesive layer 23 does not inhibit oxygen permeation by the polyimide layer 22.

  Further, in the oxygen transport cord 20, at least one end in the longitudinal direction of the cord body 21 is preferably closed with the polyimide layer 22. In this case, since air does not pass from one end of the oxygen transport cord 20 to the other end, the outflow of nitrogen in the air can be more reliably prevented, and the function of selectively transporting oxygen can be sufficiently achieved. Can be demonstrated.

  4 and 5 show a heavy duty pneumatic tire according to an embodiment of the present invention. Note that FIG. 4 shows only a portion on one side of the tire center line CL, but this pneumatic tire has a structure corresponding to the other side of the tire center line CL.

  As shown in FIGS. 4 and 5, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions that are disposed on both sides of the tread portion 1. 2 and 2 and a pair of bead portions 3 and 3 disposed on the inner side in the tire radial direction of the sidewall portions 2.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of carcass cords extending in the tire radial direction, and is wound around the bead core 5 disposed in each bead portion 3 from the tire inner side to the outer side. A cord reinforcing layer 6 extending along the carcass layer 4 is embedded in each bead portion 3 so as to wrap the bead core 5. A bead filler 7 made of a rubber composition is disposed on the outer peripheral side of each bead core 5. Further, an inner liner layer 8 is disposed along the carcass layer 4 on the inner surface of the tire.

  On the other hand, a plurality of belt layers 9A, 9B, 9C, and 9D are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 9A to 9D include a plurality of belt cords inclined with respect to the tire circumferential direction, and are arranged so that the belt cords cross each other between the layers. In the belt layers 9A to 9D, the inclination angle of the belt cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 60 °. Steel cords are preferably used as the belt cords of the belt layers 9A to 9D.

  In the pneumatic tire, a plurality of oxygen transport cords 20 extending from the vicinity of the widest belt layer 9B and the carcass layer 4 toward the tire outer surface on the outer side in the tire width direction are embedded in the shoulder region of the tread portion 1. Has been. As shown in FIG. 5, the plurality of oxygen transport cords 20 are arranged at equal intervals along the tire circumferential direction.

  As shown in FIG. 6, in the oxygen transport cord 20, the shortest distance Db from the belt layer 9B to the oxygen transport cord 20 is 8 mm or less, the shortest distance Dc from the carcass layer 4 to the oxygen transport cord 20 is 2 mm or less, and The shortest distance Ds from the tire outer surface to the oxygen transport cord 20 is arranged to be 2 mm or less. By disposing the oxygen transport cord 20 at a position that satisfies such distances Db, Dc, and Ds, oxygen contained in the air that has reached the carcass layer 4 can be effectively discharged outside the tire. If the shortest distance Db from the belt layer 9B to the oxygen transport cord 20 is too large, the air diffusion effect due to heat generation is reduced, and the shortest distance Dc from the carcass layer 4 to the oxygen transport cord 20 or the tire outer surface to the outside of the tire. If the distance Ds from the surface is too large, the effect of exhausting oxygen from the carcass layer 4 is reduced.

  In the pneumatic tire described above, oxygen contained in the air that has entered the internal space of the carcass cord constituting the carcass layer 4 can be effectively discharged to the outside of the tire through the exhaust path including the oxygen transport cord 20. In particular, the shoulder region of the tread portion 1 generates heat due to periodic deformation during running of the tire, and since the heat generation temperature is higher than other portions, air easily diffuses in the rubber. It is the most suitable as a discharge route.

  Therefore, in the pneumatic tire described above, when the air filled in the tire passes through the inner liner layer 8 and reaches the carcass layer 4, oxygen contained in the air passes through an exhaust path including the oxygen transport cord 20. Since it can be selectively discharged to the outside of the tire, the permeation of oxygen into the belt layers 9A to 9D can be reduced, and the oxidative deterioration of the belt layers 9A to 9D can be suppressed. As a result, for example, in a heavy-duty pneumatic tire used for trucks and buses, it is possible to increase the number of retreadables by extending the casing life as a retreaded tire. And since the oxygen contained in air is selectively discharged | emitted, the internal pressure fall of a pneumatic tire can be suppressed to the minimum.

  7 and 8 show a pneumatic tire according to another embodiment of the present invention. In FIG. 7, a gas permeation promoting layer 24 made of a styrene-butadiene rubber (SBR) compound is provided between the carcass layer 4 and the oxygen transport cord 20, and the gas permeation promoting layer 24 is the carcass layer 4. And the oxygen transport cord 20 are arranged so as to be in contact with each other. Since the SBR compound is more easily permeable to air (especially oxygen) than the natural rubber in the heat generation state, the gas permeation promoting layer 24 made of such a compound is interposed between the carcass layer 4 and the oxygen transport cord 20. Thus, the air that reaches the carcass layer 4 can be effectively discharged to the outside of the tire, and the oxidative deterioration of the belt layers 9A to 9D can be effectively suppressed.

  The SBR compound means a compound in which 50% by weight or more of the polymer component is SBR, and other rubbers may be blended in the compound as a polymer component as long as this blending amount is satisfied. Of course, in addition to the polymer component, a compounding agent such as a filler, a crosslinking agent, a softening agent, an anti-aging agent, and a processing aid can be appropriately added to the compound.

  As shown in FIG. 8, the gas permeation promoting layer 24 is arranged so as to continuously extend along the tire circumferential direction. In such an arrangement, air is taken into the gas permeation promoting layer 24 from the carcass cord of the carcass layer 4 throughout the tire circumferential direction, and oxygen contained in the air is guided to the oxygen transport cord 20 that is intermittently arranged. be able to. The gas permeation promoting layer 24 preferably extends continuously along the tire circumferential direction, but may extend intermittently along the tire circumferential direction.

  In the pneumatic tire according to each of the embodiments described above, as a carcass cord constituting the carcass layer 4, a steel cord 30 having a structure in which nine or more strands 31 having a strand diameter of 0.22 mm or less are twisted together. It is preferable to use (see FIGS. 9 to 11). In particular, the steel cord 30 preferably has a multi-layer twisted structure, and preferably has an internal space (a portion into which rubber does not permeate) continuous in the longitudinal direction in a state after tire vulcanization. The steel cord 30 may have a close-packed structure. Such a steel cord 30 allows movement of air in the internal space. If the wire diameter is larger than 0.22 mm, the flexibility of the carcass cord deteriorates. If the number of strands 31 to be twisted is less than 9, the rubber easily penetrates into the cord during vulcanization, so that the internal space is reduced. It becomes difficult to form. More preferably, the strand diameter is 0.17 mm to 0.22 mm, and the number of strands 31 to be twisted is 9 to 30. 9 shows a 3 + 7 structure, FIG. 10 shows a 3 + 9 structure, and FIG. 11 shows a 1 + 18 structure. In addition, for example, a 3 + 6 structure and a 3 + 9 + 15 structure should be adopted. Is possible.

  When a steel cord 30 having a structure in which nine or more strands 31 having a strand diameter of 0.22 mm or less are twisted as the carcass cord constituting the carcass layer 4 is used, the high-pressure air filled in the tire is When the air passes through the inner liner layer 8 and reaches the carcass layer 4, the air that has entered the internal space of the carcass cord can move along the longitudinal direction of the carcass cord. On the other hand, since at least one oxygen transport cord 20 extending from the vicinity of the belt layer 9B and the carcass layer 4 toward the tire outer surface on the outer side in the tire width direction is provided in the shoulder region of the tread portion 1, the carcass cord The air that has entered the interior space is effectively discharged to the outside of the tire via the oxygen transport cord 20. However, the carcass cord constituting the carcass layer 4 is not limited to the above specific example.

  In each of the embodiments described above, the shoulder region of the tread portion 1 is provided with at least one oxygen transport cord 20 extending from the vicinity of the belt layer 9B and the carcass layer 4 toward the outer surface of the tire on the outer side in the tire width direction. Although demonstrated, in this invention, the embedment position of the oxygen transport cord 20 in the pneumatic tire is not particularly limited. Since this oxygen transport cord 20 has the ability to selectively transport oxygen in the air, it can be used alone or in cooperation with other members such as a carcass layer to discharge oxygen at any position of the pneumatic tire. Can be formed.

  Moreover, although the case where the pneumatic tire for heavy loads was demonstrated in embodiment mentioned above, this invention is applicable also to the pneumatic tire of various uses including the object for passenger cars.

  A cord layer formed by twisting an organic fiber multifilament yarn (nylon 66) is coated with a polyimide layer, and an adhesive layer made of resorcin / formalin / latex is coated on the polyimide layer. Oxygen transport codes A to C having different permeation layer numbers as shown in Table 1 were prepared. Further, an oxygen transport cord D (reference) was prepared in which the surface of a cord body formed by twisting an organic fiber multifilament yarn (nylon 66) was coated with an adhesive layer made of resorcin, formalin, and latex.

  For the oxygen transport codes A to D, the oxygen transmission amount and the nitrogen transmission amount were examined by the following method. That is, after a plurality of cords arranged in a bowl shape were covered with rubber and vulcanized, a test piece having a width of 75 mm and a length of 200 mm was prepared so that both ends of the cord were exposed. While supplying compressed air to the surface layer of this test piece, low-pressure argon gas is fed into the cord from one end of the cord, and the mixed gas discharged from the other end of the cord is analyzed by gas chromatography. The oxygen permeation amount and the nitrogen permeation amount were determined. The results are shown in Table 1. The oxygen permeation amount and the nitrogen permeation amount are indicated by indices with an oxygen transport code D of 100. A larger index value means a larger transmission amount.

  In Table 1, as can be seen from the comparison with the oxygen transport cord D, the oxygen transport cords A to C in which the surface of the cord body formed by twisting the organic fiber multifilament yarn is coated with a polyimide layer transmit oxygen more than nitrogen. It is easy to do.

  Next, in a pneumatic tire having a tire size of 215 / 45R17, a carcass layer including a plurality of carcass cords is mounted between a pair of bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion. The tires of Comparative Example 1 and Examples 1 to 4 were prepared in which a plurality of oxygen transport cords extending from the vicinity of the belt layer and the carcass layer toward the outer surface of the tire on the outer side in the tire width direction were embedded in the shoulder region. Any one of the oxygen transport codes A to D described above was used as the oxygen transport code. The shortest distance Db from the belt layer to the oxygen transport cord is 8 mm, while the shortest distance Dc from the carcass layer to the oxygen transport cord and the shortest distance Ds from the tire outer surface to the oxygen transport cord are as shown in Table 2. Set.

  For comparison, tires of conventional examples having the same structure as those of Examples 1 to 4 were prepared except that the oxygen transport cord was not embedded in the shoulder region of the tread portion.

  The tires of these conventional examples, comparative example 1 and examples 1 to 4 were evaluated for air leakage and belt portion oxidative degradation by the following evaluation methods, and the results are shown in Table 2.

Air leakage:
The test tire was assembled on a rim having a rim size of 17 × 7.5 J, the air pressure was adjusted to 250 kPa, the air pressure after 180 days was measured, and the amount of reduced pressure was determined. The evaluation results are shown as an index value where the reciprocal of the amount of reduced pressure is obtained and the conventional example is 100. A larger index value means less air leakage.

Oxidative deterioration of belt part:
The test tire was assembled on a rim having a rim size of 17 × 7.5 J, the air pressure was adjusted to 350 kPa, and stored in an oven at 70 ° C. for 14 days, and then the peel force between the belt layer and the carcass layer was measured. The evaluation results are shown as index values with the conventional example being 100. A larger index value means less oxidative degradation of the belt portion.

  As can be seen from Table 2, the tires of Examples 1 to 4 were able to suppress the oxidative deterioration of the belt portion while minimizing the decrease in internal pressure in comparison with the conventional example. On the other hand, although the tire of Comparative Example 1 can suppress the oxidative deterioration of the belt portion, the decrease in the internal pressure of the pneumatic tire was remarkable.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 8 Inner liner layer 9A, 9B, 9C, 9D Belt layer 20 Oxygen transport cord 21 Code body 22 Polyimide layer 23 Adhesive layer

Claims (9)

  An oxygen transport cord, wherein a cord body formed by twisting an organic fiber multifilament yarn is coated with a polyimide layer.   The oxygen transport cord according to claim 1, wherein the polyimide layer penetrates to 3 to 13 filament layers on the surface side of the cord body.   The oxygen transport cord according to claim 1 or 2, wherein an adhesive layer made of resorcin, formalin, and latex is coated on the polyimide layer.   The oxygen transport cord according to any one of claims 1 to 3, wherein at least one end of the cord body in the longitudinal direction is closed with a polyimide layer.   A pneumatic tire characterized in that an oxygen transport cord in which a polyimide layer is coated on the surface of a cord body formed by twisting an organic fiber multifilament yarn is embedded in the tire.   In a pneumatic tire in which a carcass layer including a plurality of carcass cords is mounted between a pair of bead portions, and a belt layer is disposed on an outer peripheral side of the carcass layer in the tread portion, the belt layer is formed in a shoulder region of the tread portion. And at least one oxygen transport cord extending from the vicinity of the carcass layer toward the outer surface of the tire outside in the tire width direction, and the oxygen transport cord twists the organic fiber multifilament yarn. A pneumatic tire having a structure in which a polyimide layer is coated on a surface.   The pneumatic tire according to claim 5 or 6, wherein the polyimide layer penetrates to 3 to 13 filament layers on the surface side of the cord body.   The pneumatic tire according to claim 5, wherein an adhesive layer made of resorcin / formalin / latex is coated on the polyimide layer.   The pneumatic tire according to claim 5, wherein at least one end portion in the longitudinal direction of the cord main body is closed with the polyimide layer.

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