JP5469450B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which the durability of a band layer is improved while reducing the amount of petroleum resources used and further reducing rolling resistance.

  For example, as shown in Patent Document 1, a plurality of organic fiber cords (band cords) arranged in parallel with each other are coated with a topping rubber on the outer side in the radial direction of the belt layer in order to improve the high-speed durability performance of the tire. A tire structure in which a band layer formed by spirally winding a long belt-like cord cord ply is used. Conventionally, nylon fiber cords having excellent breaking strength and durability have been widely used as band cords for this band layer.

  In recent years, as shown in Patent Document 2, for example, a tire formed mainly of raw materials derived from non-petroleum resources (hereinafter sometimes referred to as “eco-tire”) has attracted attention in order to improve the global environment. As for the band cords, the use of rayon fiber cords derived from non-petroleum resources using natural materials as raw materials is being considered as an alternative to nylon fiber cords derived from non-petroleum resources.

Japanese Patent Laid-Open No. 08-40013 JP-A-2003-63206

  However, rayon fiber cords have high water absorption, and tend to decrease the adhesion to rubber when the moisture content exceeds 4%, for example. In addition, since the breaking strength is low and brittle, the cord may break during high-speed running or the like.

  In addition, in order to reduce the rolling resistance of the tire for the eco-tire, it has been studied to replace carbon black as a reinforcing agent for topping rubber with silica derived from resources other than petroleum in the band layer. However, when silica-blended rubber is applied to the band layer, there is a problem that the adhesiveness with the band cord is reduced and the durability of the tire is lowered. In particular, when a rayon fiber cord is used for the band cord, a decrease in durability is conspicuous in combination with a decrease in adhesiveness due to water absorption.

  Therefore, the present invention is based on the formation of a band layer using a belt-like rubber ply using a short fiber / silica-blended rubber in which natural short fibers and silica are blended instead of the belt-like cord ply, and the amount of petroleum resources used An object of the present invention is to provide a pneumatic tire in which the durability of the tire is improved while reducing the rolling resistance and further reducing the rolling resistance.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application includes a belt layer disposed on the radially outer side of the toroidal carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion and inside the tread portion. A belt layer disposed on the outer side in the radial direction of the belt layer and covering at least an outer end portion in the tire axial direction of the belt layer;
The band layer is formed by spirally winding a small and long band-shaped rubber ply using a short fiber / silica-blended rubber in which short fibers of natural materials and silica are blended in a rubber component ,
The belt-like rubber ply is formed of an inner layer made of the short fiber / silica blended rubber and a coating layer made of a short fiber non-blend rubber not blended with the short fiber and covering the periphery of the inner layer. Yes.

In the invention of claim 2, the short fibers of the short fiber / silica-containing rubber are formed by immersing in at least a part of the surface thereof in an RFL solution in which a condensate of resorcinol and formaldehyde is dispersed in latex. It is characterized by having an adhesive layer.

In the invention of claim 3, the short fiber / silica compounded rubber is characterized in that 10 to 50 parts by mass of short fibers and 20 to 60 parts by mass of silica are compounded with respect to 100 parts by mass of the rubber component.

  As described above, the present invention forms a band layer by spirally winding a small and long band-shaped rubber ply using a short fiber / silica compound rubber in which short fibers of natural materials and silica are blended. ing. Therefore, the amount of petroleum resources used can be reduced as compared with a conventional band layer using nylon fiber cords as band cords. Moreover, since the fuel efficiency can be improved by reducing the rolling resistance of the tire by blending silica, it can contribute to the reduction of carbon dioxide emissions.

The band layer has a circumferential rigidity enhanced by the short fibers and functions as a highly elastic elastic ring. Therefore, lifting and outer diameter growth starting from the outer end of the belt layer can be suppressed, and high-speed durability can be improved. In addition, when a rayon cord derived from a resource other than petroleum is used for the band cord, the cord breakage damage, and the cord and rubber adhesiveness decrease due to the hygroscopic property of the cord, and further the cord due to silica blending Since deterioration in adhesiveness with rubber can be avoided, high-speed durability and general durability substantially the same as when a nylon fiber cord is used for the band cord can be ensured.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is sectional drawing which exaggerates and shows a band layer with a belt layer. (A), (B) is sectional drawing which exaggerates and shows the other example of a band layer. It is a perspective view which shows an example of the strip | belt-shaped rubber ply used for a band layer. (A) is sectional drawing of the said strip | belt-shaped rubber ply, (B) is sectional drawing which shows the other example of a strip | belt-shaped rubber ply. (A), (B) is explanatory drawing which shows the formation method of a strip | belt-shaped rubber ply.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a cross-sectional view when the pneumatic tire 1 of the present invention is a radial tire for passenger cars, and a toroidal carcass 6 extending from the tread portion 2 to the sidewall portion 3 to the bead core 5 of the bead portion 4. The belt layer 7 disposed at the radially outer side of the carcass 6 and inside the tread portion 2 and the band layer 9 disposed at the radially outer side of the belt layer 7 are provided.

  The carcass 6 is formed of one or more carcass plies 6A, in this example, one carcass ply 6A in which an array of carcass cords arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire circumferential direction is covered with a topping rubber. Is done. The carcass ply 6A includes a series of ply turn-up portions 6b that are turned back from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the toroid-like ply main body portion 6a straddling the bead cores 5 and 5. Further, a bead apex rubber 8 for bead reinforcement extending in a tapered shape from the bead core 5 to the outer side in the tire radial direction is disposed between the ply main body portion 6a and the ply turn-up portion 6b.

  The belt layer 7 includes two or more belt plies 7A, in this example, two belt plies 7A, in which an array of belt cords arranged at an angle of 10 ° to 35 ° with respect to the tire circumferential direction is covered with a topping rubber. 7B. In the belt layer 7, the belt cords cross each other between the plies 7 </ b> A and 7 </ b> B, thereby increasing the belt rigidity and strongly reinforcing the substantially entire width of the tread portion 2.

  In the tire of the present invention, the carcass cord and the belt cord are not particularly restricted, but cords derived from non-oil resources are preferable from the viewpoint of reducing the amount of petroleum resources used. In the carcass cord, natural fibers made from natural materials as raw materials A cord can be suitably used.

  As this natural fiber cord, the cord of the regenerated cellulose fiber which processed the cellulose which is a fiber of a vegetable fiber, and the refined cellulose fiber can be used conveniently. The regenerated cellulose fiber is obtained by once chemically decomposing cellulose using a solvent and then coagulating and regenerating it. Rayon, acetate, cupra and the like are known. The purified cellulose fiber is obtained by physically refining cellulose without chemically decomposing it, and is formed by dissolving and continuously spinning cellulose molecules. As this refined cellulose fiber, for example, lyocell (trademark of Lenzing) or Tencel (trademark of Coatles) is known. And since the carcass cord does not require as high breaking strength as the band cord, in this example, these regenerated cellulose fiber and purified cellulose fiber are used as the carcass cord. Depending on requirements, synthetic fiber cords derived from petroleum resources such as nylon and polyester can be used, but in this case, it is preferable to use recycled fibers such as recycled polyester fibers from the viewpoint of reducing the amount of petroleum resources used. .

  For the belt cord, a conventional metal cord derived from non-petroleum resources, such as a steel cord, can be preferably used.

  Next, the band layer 9 is arranged on the outer side in the radial direction of the belt layer 7 and covers at least the outer end portion 7E in the tire axial direction of the belt layer 7 to restrain the outer end portion 7E. As a result, lifting and outer diameter growth starting from the outer end portion 7E caused by centrifugal force due to high-speed traveling are suppressed, and high-speed durability is improved.

  In this example, as shown in FIG. 2, the band layer 9 is formed of a full band ply 9A that covers substantially the entire width of the belt layer 7 including the outer end portion 7E. However, for example, as shown in FIG. 3 (A), it is formed from a pair of left and right edge band plies 9B, 9B covering only the outer end 7E, or as shown in FIG. A combination of the band ply 9A and the edge band plies 9B and 9B may be used as appropriate.

  As shown in FIGS. 4 and 5, the full band ply 9A and the edge band ply 9B are small ones using a short fiber / silica compound rubber G0 in which short fibers of natural materials and silica are compounded in a rubber component. It is formed by winding a long and long belt-like rubber ply 10 in a spiral shape. The width W and the thickness t of the belt-like rubber ply 10 are not particularly limited, but the width of 5 to 10 mm and the thickness of 0.7 to 3.0 mm are the same as in the case of the belt-like cord ply used for the conventional band layer. Is preferable from the viewpoint that a conventional winding device can be used.

  Further, in this example, the belt-like rubber ply 10 is composed of the inner layer 10A composed of the short fiber / silica blended rubber G0 and the short fiber non-blended rubber G1 not blended with short fibers, and at least the upper surface S1 and the lower surface of the inner layer 10A. And a thin coating layer 10B covering S2. In particular, FIG. 5A shows the inner layer 10A that is covered with a coating layer 10B. As shown in FIG. 5B, the upper surface S1 and the lower surface S2 of the inner layer 10A are covered vertically. What coat | covered with the layer 10B can also be employ | adopted.

  As the rubber component of the short fiber / silica compound rubber G0 and the short fiber non-compound rubber G1, diene rubbers such as natural rubber, styrene butadiene rubber, butadiene rubber and isoprene rubber are used alone or in combination. From the viewpoint of reducing the amount of resources used and adhesion, it is particularly preferable that the rubber component contains natural rubber in an amount of 65% by mass or more, and further 75% by mass or more. Examples of the natural rubber include epoxidized natural rubber obtained by epoxidizing a part of natural rubber by a method such as a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, or a peracid method.

  The short fibers used in the short fiber / silica-containing rubber G0 are natural materials. Examples of the short fibers of the natural material include plant fibers, animal fibers, the regenerated cellulose fibers, and the short fibers of the purified cellulose fibers. The regenerated cellulose fibers and the purified cellulose fibers are preferable from the viewpoint of the reinforcing effect. . If the short fibers are too fine, the reinforcing effect tends to be reduced, and if the short fibers are too coarse, the durability tends to be reduced, such as the belt-like rubber ply 10 is likely to crack. Accordingly, when the short fibers are classified with a sieve, a Tyler mesh having a roughness that passes through 20 mesh and does not pass through 60 mesh can be suitably used. It is preferable that the short fiber has an average diameter D of 1 to 50 μm, an average length L of 100 to 3000 μm, and an aspect ratio L / D of 10 to 500 which is a ratio of the average length L to the average diameter D. Can be adopted.

  Moreover, in order to improve adhesiveness with a rubber component, it is preferable to provide the adhesive layer formed by immersing in the RFL solution in at least one part of the surface in the said short fiber. Such a short fiber can be obtained, for example, by the following method. First, fiber cords or fiber yarns (hereinafter collectively referred to as fiber cords or the like) used as the short fiber material are immersed in the RFL solution. Thereafter, the fiber cord and the like are heated and dried at a temperature of 100 to 160 ° C. (for example, about 120 ° C.), and the dried fiber cord and the like are further heated at a temperature of 215 to 260 ° C. for 1 to 4 minutes. By processing, the binding strength between the fiber cord and the like and the solid content of the RFL solution adhering thereto is increased. Thereafter, the fiber cord or the like is pulverized by a pulverizer, whereby a short fiber having an adhesive layer made of a solid content of the RFL solution on at least a part of the surface can be formed. The RFL solution is a well-known treatment solution for adhesion in which a condensate of resorcinol (R) and formaldehyde (F) is dispersed in rubber latex (L).

The short fiber / silica compound rubber G0 contains silica as a rubber reinforcing agent. The silica is not particularly limited, but a rubber having colloidal characteristics with a nitrogen adsorption specific surface area (BET) in the range of 150 to 250 m ² / g and a dibutyl phthalate (DBP) oil absorption of 180 ml / 100 g or more is used. It is preferable in terms of reinforcing effect on rubber and rubber processability. Such silica can reduce the amount of petroleum resources by reducing the amount of carbon black used, and also contributes to the reduction of carbon dioxide emissions by reducing tire rolling resistance and improving fuel efficiency. Yes.

  The covering layer 10B is used to increase the adhesion efficiency between the belt-like rubber ply 10 and the belt layer 7 when the belt-like rubber ply 10 is wound on the belt layer 7 at the time of tire formation, and to improve the formation efficiency and formation accuracy of the band layer 9. It is formed. Accordingly, the coating layer 10B is made of a short fiber non-blended rubber G1 in which the surface becomes a smooth surface without unevenness and the short fiber is not blended in order to increase the adhesiveness. In this short fiber non-blended rubber G1, carbon black can be used as a reinforcing agent, but it is preferable to use silica. The thickness T of the coating layer 10B is preferably in the range of 0.2 to 1.0 mm. If the thickness T is less than 0.2 mm, the effect of improving the adhesion by the coating layer 10B cannot be expected. Since the ratio of the short fiber / silica compound rubber G0 in the band layer 9 is reduced, the high speed durability is adversely affected.

  For example, as shown in FIG. 6A, the belt-like rubber ply 10 can be easily extruded using, for example, a multi-axis extruder E, a preformer M, and a die plate P. 6B is a cross-sectional view taken along the line AA in FIG. For example, the extruder E extrudes the short fiber / silica compounded rubber G0 from the central first extruding port O1, and extrudes the short fiber non-blended rubber G1 from the annular second extruding port O2. The extruded rubbers G0 and G1 are integrated with each other via a preformer M and a die plate P fixed to the extruder E, and are supplied from a third extrusion port O3 provided in the die plate P at the front end. It is molded into a cross-sectional shape and extruded.

  The manufacturing method of the belt-like rubber ply 10 is not limited to the above specific example. For example, the inner layer 10A is formed by an extruder or a calender roll, and the upper and lower surfaces thereof are coated layers 10B formed by other calender rolls. By sticking, the belt-like rubber ply 10 having the structure shown in FIG. 5B can be formed.

  Here, when the short fiber / silica compounded rubber G0 is extruded using an extruder or rolled using a calender roll, the short fiber is in the length direction of the belt-shaped rubber ply which is the extrusion direction. Orient along. Therefore, by forming the band layer 9 by winding the belt-shaped rubber ply 10 in a spiral shape, the short fibers are oriented in the tire circumferential direction and the circumferential rigidity is increased. Thus, the band layer 9 can function as a highly elastic elastic ring, and lifting and outer diameter growth starting from the outer end 7E of the belt layer 7 can be suppressed.

  Further, the band layer 9 is different from the rayon fiber cord even when a rayon fiber is used as the short fiber, and the adhesiveness between the cord and the rubber due to water absorption is reduced, and the cord and the rubber due to silica. The adhesiveness is not significantly reduced, and breakage due to the brittleness of the rayon fiber cord does not occur. Therefore, it is possible to stably exhibit the lifting and suppression of outer diameter growth, and exhibit not only high-speed durability but also general durability, for example, at the same level as a conventional band layer using nylon fiber cords, for example. It becomes possible.

  In the short fiber / silica compound rubber G0, it is preferable to mix 10 to 50 parts by mass of short fibers and 20 to 60 parts by mass of silica with respect to 100 parts by mass of the rubber component. When the blended amount of the short fibers is less than 10 parts by mass, it is difficult to satisfy the high speed durability because the lifting of the belt layer 7 and the suppression of the growth of the outer diameter are insufficient. On the other hand, when the blending amount of silica is less than 20 parts by mass, the amount of petroleum resources used and the rolling resistance cannot be sufficiently reduced. On the contrary, when the blending amount of the short fibers exceeds 50 parts by mass and the blending amount of silica exceeds 60 parts by mass, the band layer 9 becomes too hard and brittle, and tends to impair general durability. . Therefore, the lower limit of the blend amount of the short fibers is more preferably 15 parts by mass or more, and the upper limit is more preferably 35 parts by mass or less. Further, the lower limit of the amount of silica is more preferably 25 parts by mass or more, and the upper limit is more preferably 55 parts by mass or less. Further, when silica and carbon black are mixed, it is preferable from the viewpoint of high-speed durability that the total amount of each compound is larger than 40 parts by mass.

  Next, the belt-like rubber ply 10 can be formed only by the inner layer 10A of the short fiber / silica compound rubber G0 without providing the covering layer 10B.

  The band layer 9 can be formed by edge band plies 9B and 9B as shown in FIG. In this case, the edge band ply 9B is formed so as to cover a range Y of 10% or more and 20% or less of the tire layer axial width WB of the belt layer 7 from the outer end of the belt layer 7 in the tire axial direction. preferable. If the coating range Y is less than 10%, the effect of improving high-speed durability is not sufficiently achieved. Further, even if it exceeds 20%, no further increase in the effect of improving the high-speed durability is expected, leading to an unnecessary increase in cost.

  However, in addition to the high-speed durability, the edge band ply 9B can be formed to exceed 20% in order to improve steering stability and road noise performance, and further, between the edge band plies 9B and 9B. On a certain tire equator side, a band auxiliary layer 12 (indicated by a one-dot chain line in FIG. 3A) is formed by spirally winding a small and long belt-like cord ply in which an auxiliary cord is covered with a topping rubber. You can also. On the tire equator side, the lifting and outer diameter growth are unlikely to occur, and therefore the natural fiber cord, for example, rayon fiber cord, can be used as the auxiliary cord. Non-fiber compounded rubber can be used. When the band auxiliary layer 12 is formed, the side edge part of the band auxiliary layer 12 and the side edge part of the edge band ply 9B can be overlapped with each other or separated from each other.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  In order to confirm the operational effects of the present invention, a radial tire for a passenger car having a tire size of 195 / 65R15 having the internal structure shown in FIG. 1 was prototyped according to the specifications in Tables 1 and 2, and the high speed durability of each sample tire was And general durability was tested and compared with each other. A sample of a band ply for band layer formation (a band rubber ply and a band cord ply are collectively referred to as a band ply) was prototyped, and the adhesion between the band plies after vulcanization was tested. Each tire has substantially the same specifications except for the band layer specifications shown in Tables 1 and 2.

  In Comparative Examples A1 to A4, a band layer is formed by spirally winding a band-like ply having a band cord. Further, Examples A1 to A10 and Comparative Examples A5 to A9 in Table 1 are formed by forming the belt-like ply only by the inner layer, and Examples B1 to B8 and Tables B1 to B6 of Table 2 are formed by using the belt-like ply as the inner layer. And a coating layer covering the periphery thereof. The thickness T of the coating layer is 1.0 mm. Moreover, the thing of the coarseness which passes 40 mesh as a short fiber and does not pass 50 mesh was used. In addition, the band auxiliary layer is formed by using a band-like cord ply in which an array of rayon fiber cords (1260d / 2) is topped with a short fiber non-blending rubber as in Comparative Example A2.

(1) High speed durability:
In accordance with 6.4 “High-speed performance test A” of JIS D4230, using a drum tester under the conditions of rim (15 × 6), internal pressure (280 kPa), load (4.83 kN), initial speed (170 km / h) Up to 190km / h, step up by 10km / h every 10 minutes,
And at 200 km / h or more, it was stepped up by 10 km / h every 20 minutes, and the speed and time when the tread portion was damaged were measured. The case where the speed when the tread portion was damaged was 210 km / h or more was regarded as acceptable.

(2) General durability:
After running 30,000 km at a speed of 80 km / h under the conditions of rim (15x6), internal pressure (190 kPa), load (6.96 kN) using a drum tester, the periphery of the band layer was disassembled and turned into a band layer It was judged visually whether damage had occurred. Those without damage were considered acceptable.

(3) Adhesiveness:
When the band layer is formed from a band-shaped rubber ply, an unvulcanized rubber sheet having a thickness of 1.0 mm is formed using a rubber mixture for forming the band-shaped rubber ply (short fiber moisture content 6%), and this rubber Two sheets of the sheets were bonded and press vulcanized at 170 ° C. for 15 minutes to produce a sample for an adhesion test. This sample was cut along the orientation direction of the short fiber at a width of 25 cm, and the rubber was pulled between two rubber sheets at a tensile speed of 50 mm / min with a tensile tester in accordance with JIS K6256-1. The adhesive force between the sheets (unit: N / 25 cm) was measured. In addition, all the samples are peeled off so that the rubber is torn off at a position different from the interface between the rubber sheets, and the adhesive force shows a high value.

  When the band layer is formed from a belt-like cord ply, two unvulcanized band cords (moisture ratio of 6%) arranged at regular intervals are made of a rubber blend for forming the belt-like cord ply and have a thickness of 0.7 mm. A rubber sheet with a cord was formed by sandwiching the two rubber sheets, and two of the rubber sheets with the cord were bonded together, and press vulcanized at 170 ° C. for 15 minutes to produce a sample for an adhesion test. This sample is cut along the length direction of the band cord at a width of 25 cm, and pulled between the two corded rubber sheets at a tensile speed of 50 mm / min with a tensile tester in accordance with JISK6256-1. Then, the adhesive force (unit: N / 25 cm) between the corded rubber sheets was measured. All the samples are peeled off so that the rubber is peeled off from the band cord, and the adhesive force shows a low value.

(4) Adhesion during band layer formation:
The adhesion between the belt-like ply and the belt layer when forming the band layer when forming the raw tire,
The adhesion between the belt-like ply and the belt layer when the belt-like ply was wound on the belt layer at the time of forming the green tire was evaluated in three stages: ○, Δ, and ×.
○ --Excellent adhesion.
Δ—Although poor in adhesion, there is no problem in the formation efficiency and formation accuracy of the band layer.
*-It is inferior to adhesiveness and has a bad influence on the formation efficiency and formation accuracy of a band layer.

  As shown in Table 1, in the tires of the examples, the cord and rubber resulting from cord breakage damage and cord hygroscopicity while reducing the amount of petroleum resources used by adjusting the blending amount of short fibers Can prevent the deterioration of the adhesion between the cord and the rubber due to the silica compounding, and ensure the high speed durability and the general durability almost equivalent to the case of using the nylon fiber cord for the band cord. I can confirm that I can do it.

  Also, as shown in Table 2, by providing the belt-like ply with a coating layer made of short fiber non-blended rubber, the adhesiveness between the belt-like ply and the belt layer can be enhanced while exhibiting the above-mentioned effects. It can be confirmed that the formation efficiency and formation accuracy of the film can be secured high.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9 Band layer 10 Band-like rubber ply 10A Inner layer 10B Coating layer G0 Short fiber and silica compound rubber G1 Short fiber non-compound rubber

Claims (3)

A belt layer disposed radially outside and inside the tread portion of the toroidal carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and disposed on the radially outer side of the belt layer and of the belt layer Including at least a band layer covering the outer end portion in the tire axial direction,
The band layer is formed by spirally winding a small and long band-shaped rubber ply using a short fiber / silica-blended rubber in which short fibers of natural materials and silica are blended in a rubber component ,
The belt-like rubber ply is formed of an inner layer made of the short fiber / silica blended rubber and a coating layer made of a short fiber non-blended rubber not blended with short fibers and covering the periphery of the inner layer. Pneumatic tires. The short fiber of the short fiber / silica compound rubber has an adhesive layer formed on at least a part of its surface by dipping in an RFL solution in which a condensate of resorcinol and formaldehyde is dispersed in latex. The pneumatic tire according to claim 1, wherein The air according to claim 1 or 2, wherein the short fiber / silica compounded rubber is compounded with 10 to 50 parts by mass of short fibers and 20 to 60 parts by mass of silica with respect to 100 parts by mass of the rubber component. Enter tire.

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