JP7005960B2 - Band-shaped members and pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire provided with a band-shaped member and a belt cover layer.

Pneumatic tires for passenger cars may be provided with a belt cover layer as a reinforcing member on the outside of the belt layer. The belt cover layer is manufactured, for example, by spirally winding a band-shaped member having a plurality of aligned cords coated with a coated rubber around the outside of the belt layer. Many petroleum resource-derived fibers are used for the cord of the strip-shaped member.
In recent years, from the viewpoint of reducing the environmental load, it has been required to reduce the amount of petroleum resources used. For example, Patent Document 1 describes a strip-shaped member using a fiber made of nylon 11 derived from a non-petroleum resource as a cord.

Japanese Unexamined Patent Publication No. 2012-56330

However, it has been found that when a strip-shaped member having a cord made of nylon 11 fiber is used for the belt cover layer of a pneumatic tire, the uniformity of the tire is deteriorated.

An object of the present invention is to provide a strip-shaped member capable of suppressing deterioration of tire uniformity while reducing the environmental load, and a pneumatic tire provided with such a strip-shaped member.

One aspect of the present invention is a strip-shaped member.
One code or multiple aligned codes,
With a coated rubber covering the cord,
The cord comprises at least one nylon 11 fiber and at least one fiber having a smaller shrinkage stress than the nylon 11 fiber.
The nylon 11 fiber and the fiber having a smaller shrinkage stress than the nylon 11 fiber are each under-twisted and twisted into an up-twist.
The cord has a twist coefficient K calculated from the following formula (1) of 1100 to 1500 .
K = T × D ^1/2 ... (1)
(In the formula, T is the number of twists (times / 10 cm) of the cord, and D is the total fineness (dtex) of the cord.)

The mass ratio of the fiber made of a material derived from a resource other than petroleum resources in the cord is preferably 80% or less.

Another aspect of the present invention is a pneumatic tire.
With the belt layer,
It is characterized by including a belt cover layer which is arranged on the outer peripheral side of the belt layer and in which the band-shaped member is wound in the tire circumferential direction.

According to the present invention, it is possible to obtain a strip-shaped member and a pneumatic tire that can suppress deterioration of tire uniformity due to molding while reducing the environmental load.

It is a tire cross-sectional view which shows an example of the cross-section of the tire of this embodiment. It is sectional drawing which shows an example of the strip-shaped member of this embodiment.

(Overall explanation of tires)
Hereinafter, the pneumatic tire of the present embodiment will be described. FIG. 1 is a tire cross-sectional view showing an example of a cross section of a pneumatic tire (hereinafter referred to as a tire) 10 of the present embodiment.
The tire 10 is, for example, a passenger car tire. Passenger car tires are tires specified in Chapter A of JATMA YEAR BOOK 2012 (Japan Automobile Tire Association standard). In addition, it can be applied to the tires for light trucks specified in Chapter B and the tires for trucks and buses specified in Chapter C.

The tire circumferential direction described below refers to the direction in which the tread surface rotates (both rotation directions) when the tire 10 is rotated around the tire rotation center line, and the tire radial direction refers to the tire rotation center line. The direction of radiation that extends orthogonally to the tire. The tire width direction is a direction parallel to the tire rotation center line.

(Tire structure)
The tire 10 has a carcass ply layer 4, belt layers 7 and 8, a belt cover layer 9, and a bead core 5 as a structure. The tire 10 mainly has a tread portion 1 and a sidewall portion 2 around these structures.

The carcass ply layer 4 is a layer containing a plurality of organic fiber cords coated with rubber, and is wound between a pair of annular bead cores 5 to form a toroidal shape.
Two belt layers 7 and 8 are provided on the outer side of the carcass ply layer 4 in the tire radial direction. The belt layers 7 and 8 are members coated with rubber on steel cords arranged at a predetermined angle, for example, 20 to 30 degrees with respect to the tire circumferential direction. The inclination directions of the steel cords of the two belt layers 7 and 8 are inclined in different directions from the tire circumferential direction to the tire width direction and intersect with each other. The number of belt layers is not limited to two and may be three or four or more.
The belt cover layer 9 is a layer that covers the belt layers 7 and 8 from the outer side (outer peripheral side) of the belt layers 7 and 8 in the tire radial direction, and the belt-shaped member described later is wound around the tire and vulcanized. It becomes. The belt cover layer 9 shown in FIG. 1 is one layer that covers the entire area of the belt layers 7 and 8 in the tire width direction, but the tire 1 is the belt cover layer 9 and the belt cover layer 9 in the tire width direction. It may further have two belt cover layers laminated so as to cover both ends from the outer peripheral side so as to be separated from each other in the tire width direction.

A tread portion 1 made of tread rubber is provided on the outer side of the belt cover layer 9 in the tire radial direction, and sidewall portions 2 made of side rubber are provided on both sides of the tread portion 1 in the tire width direction. A rim cushion rubber is provided at the inner end of the side rubber in the tire radial direction and comes into contact with the rim on which the tire 10 is mounted. A bead filler rubber 6 is provided on the outer side of the bead core 5 in the tire radial direction so as to be sandwiched between the portions of the carcass ply layer 4 which is wound around the bead core 16 and folded back. Inner liner rubber is provided on the inner surface of the tire 10 facing the air-filled tire cavity region surrounded by the tire 10 and the rim.

Although the tire 10 has such a tire structure, the tire structure of the present embodiment is not limited to the tire structure shown in FIG.

(Strip-shaped member)
FIG. 2 is a cross-sectional view showing an example of the strip-shaped member 11 of the present embodiment.
The band-shaped member 11 is a member used for a reinforcing member (for example, a belt cover layer 9) of a tire 10, and has a plurality of cords 13 and a coated rubber 15.

The plurality of cords 13 are aligned in parallel with each other. The number of cords 13 included in the strip-shaped member 11 is a plurality of cords in the example shown in FIG. 2, but may be one, and is, for example, 1 to 15. The number of cords 13 driven is, for example, 6 to 10 cords / cm in the width direction of the strip-shaped member.

The cord 13 has at least one nylon 11 fiber and at least one fiber (hereinafter, also referred to as another fiber) having a contraction stress smaller than that of the nylon 11 fiber.

Nylon 11 fiber can be synthesized from ricinoleic acid, which is the main component of castor oil, by a known method, and can be obtained as a commercially available product such as Castron (registered trademark) manufactured by Unitika Ltd. The number of nylon 11 fibers included in the cord 13 is, for example, one, two, three, or four. Since the code 13 has nylon 11 fibers derived from resources other than petroleum resources (non-petroleum resources), the amount of petroleum resources used as a raw material for the strip-shaped member 11 is reduced, and the environmental load is reduced. It is planned.

The shrinkage stress of the other fibers is smaller than that of nylon 11 fibers, as described above. In the present specification, the shrinkage stress refers to the dry heat shrinkage stress (cN / dtex) defined in JIS L1017: 2002. The dry heat shrinkage stress is preferably measured at 168 ± 5 ° C. According to the study of the present inventor, in a pneumatic tire using a strip-shaped member having a cord made of nylon 11 fiber for the belt cover layer, the heat shrinkage of the nylon 11 fiber during vulcanization molding is large, so that the heat shrinks. It has been clarified that the vulcanized fibers bite into the rubber and the dimensional accuracy of the tire deteriorates, and as a result, the uniformity of the tire deteriorates. In the present embodiment, since the cord 13 of the strip-shaped member 11 has another fiber having a contraction stress smaller than that of the nylon 11 fiber, the case where the strip-shaped member having the cord composed of only the nylon 11 fiber is used is used. In comparison, the amount of heat shrinkage of the cord 13 during vulcanization molding is reduced, and deterioration of tire uniformity can be suppressed. That is, according to the present embodiment, the tire uniformity is achieved by having other fibers having a shrinkage stress smaller than that of the nylon 11 fibers while reducing the environmental load by having the nylon 11 fibers. Deterioration can be suppressed.
The difference in shrinkage stress between the nylon 11 fiber and the other fiber is preferably 100 cN / dtex or more in that the effect of relaxing the heat shrinkage amount of the cord 13 is enhanced.

Examples of other fibers include aramid fiber, nylon 66 fiber, polyethylene terephthalate (PET) fiber, rayon fiber, carbon fiber, polyethylene naphthalate (PEN) fiber and the like. Among them, other preferable fibers are aramid fiber and carbon fiber. The aramid fiber may be either a para-based aramid fiber or a meta-based aramid fiber, but the para-based aramid fiber is preferable because it has a high effect of relaxing the magnitude of the heat shrinkage amount of the cord 13.

The nylon 11 fiber and the other fibers are each twisted downward and twisted upward, and the twist coefficient K of the cord 13 calculated from the following formula (1) is preferably 1100 to 2200.
K = T × D ^1/2 ... (1)
(In the formula, T is the number of top twists of the cord 13 (times / 10 cm), and D is the total fineness (dtex) of the cord 13.)
When the twist coefficient is less than 1100, the number of twists of the cord 13 is small and the springiness is small, so that the cord 13 tends to generate heat as the tire rolls, and the rolling resistance may increase. Further, when the twist coefficient exceeds 2200, the number of twists of the cord 13 is large and the springiness is increased, so that the cord 13 may be stretched too much during vulcanization molding, the dimensional accuracy may be deteriorated, and the uniformity may be deteriorated. Further, if the twist coefficient exceeds 2200, the hardness (elastic modulus or rigidity per cord) of the cord 13 may decrease, and the rolling resistance may increase. The twist coefficient is preferably 1100 to 1500 from the viewpoint of reducing rolling resistance and suppressing deterioration of tire uniformity.
The number of twists of the cord 13 is, for example, 20 to 70 times / cm, and the total fineness of the cord 13 is, for example, 1000 to 5000 dtex.

It is preferable that the other fibers have a shrinkage stress smaller than that of the nylon 11 fiber and a strength higher than that of the nylon 11 fiber. The strength refers to the tensile strength (cN / dtex) at the time of drying (or at constant temperature or humidity control) specified in JIS L1017: 2002. When the strength is higher than that of nylon 11 fiber, a sufficient effect of suppressing deterioration of tire uniformity can be obtained. The strength is preferably 10 cN / dtex or more in that the effect of suppressing deterioration of uniformity is equal to or higher than that of the case where the cord composed of only nylon 66 is provided, or similar. The difference in strength between the nylon 11 fiber and the other fiber is preferably 1.5 cN / dtex or more in that the effect of relaxing the heat shrinkage amount of the cord 13 is enhanced.

The ratio of the mass of fibers made of non-petroleum resource material (hereinafter, also referred to as non-petroleum resource ratio) in Code 13 is preferably 80% or less. The fibers made of non-petroleum resource materials are, for example, nylon 11 fibers, rayon fibers and the like. If the non-petroleum resource ratio exceeds 80%, the amount of heat shrinkage of the cord 13 during vulcanization molding is large, and deterioration of tire uniformity may not be sufficiently suppressed. Further, if the non-petroleum resource ratio exceeds 80%, the strength of the cord 13 decreases, and the target tire performance such as low rolling resistance and high-speed steering stability may not be obtained. On the other hand, the ratio of non-petroleum resources is preferably 55% or more. If the non-petroleum resource ratio is less than 55%, for example, the cord 13 may be too hard to follow the rubber during vulcanization, resulting in deterioration of tire uniformity. Further, if the ratio of non-petroleum resources is less than 55%, low rolling resistance and high-speed steering stability may deteriorate. The non-petroleum resource ratio is preferably 70 to 80% from the viewpoint of enhancing the effect of suppressing deterioration of tire uniformity.

The number of other fibers included in the code 13 is, for example, one or two.
The number of all fibers included in the code 13 is, for example, 2 to 4.

The coated rubber 15 is a rubber that covers the cord 13, and is made of a rubber composition. The rubber composition contains a rubber component and a filler.

Examples of the rubber component include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and two of these rubbers. Diene rubber blended with more than seeds can be mentioned.

Examples of the filler include carbon black and silica. The blending amount of the filler is preferably, for example, 15 to 80 parts by mass, preferably 30 to 80 parts by mass with respect to 100 parts by mass of the diene rubber.

In the rubber composition, in addition to the rubber component and filler, additives such as sulfur, zinc oxide, an antiaging agent, a vulcanization accelerator, a processing aid, a plasticizer, and a vulcanizing agent are appropriately blended in a general amount. Can be included in.

The band-shaped member 11 is prepared by mixing a rubber composition containing each of the above components with a general kneader such as a Banbury mixer, a kneader, or a roll to prepare a coated rubber, and coating the cord 13 with the prepared coated rubber. Can be manufactured by.
The dimensions of the strip-shaped member 11 are, for example, 0.4 to 3 mm in thickness and 5 to 15 mm in width when the diameter of the cord 13 is 0.3 to 1 mm. The diameter of the cord 13 when the cord 13 is made by twisting a plurality of fibers means the diameter of the smallest circle circumscribing the cross-sectional contour shape of the cord 13.
The belt cover layer 9 is formed by vulcanizing an unvulcanized tire in which a band-shaped member 11 is spirally wound around the outer peripheral side of the belt layers 7 and 8 without a gap in the tire width direction.

According to this embodiment, it is possible to suppress deterioration of tire uniformity due to molding while reducing the environmental load.

(Examples, conventional examples, comparative examples)
Various strip-shaped members having different codes as described above were manufactured, unvulcanized tires were manufactured using the manufactured strip-shaped members, and then vulcanized, and the uniformity of the manufactured test tires was investigated. In addition, test tires were attached to passenger cars to investigate low rolling resistance and high-speed steering stability.
The rubber composition of the strip-shaped member is prepared by kneading the components excluding sulfur and the vulcanization accelerator in a 1.8 L closed mixer at 160 ° C. for 5 minutes according to the blending amount described above, and then releasing the sulfur and vulcanization into a masterbatch. It was prepared by adding an accelerator and kneading with an open roll. The obtained rubber composition was pressure-bonded to the cords shown in Tables 1 and 2 to obtain a strip-shaped member. A test tire (tire size: 235 / 60R18) provided with a belt cover layer by spirally winding the obtained strip-shaped member around the entire width of the belt layer of the unvulcanized tire and vulcanizing the entire unvulcanized tire. ) Was produced.

As the shrinkage stress of the cord, the dry heat shrinkage stress (cN / dtex) was measured at 170 ° C.
As the strength of the cord, the tensile strength at drying (cN / dtex) was measured.
The non-petroleum resource ratio of the code was calculated according to the following formula, and when it was 45% or more, it was evaluated that the environmental load reduction could be achieved.
Non-petroleum resource ratio = (total fineness of fibers derived from non-petroleum resources / total fineness of fibers constituting the code) x 100

(Uniformity)
According to the test method specified in JIS D4233, each test tire was mounted on a uniformity measuring device, and radial force variation (RFV) was measured. The evaluation result is shown by an index with the conventional example 2 as 100 using the reciprocal of the measured value. The larger the index value, the better the uniformity. When the index value is 103 or more, it is evaluated that the deterioration of uniformity can be suppressed, and when the index value is 108 or more, it is evaluated that the effect of suppressing the deterioration of uniformity is high, and the index value is 115 or more. The case was evaluated as having a particularly high effect of suppressing the deterioration of uniformity.

(High-speed steering stability)
The test tires assembled on the standard rim were mounted on the vehicle, and the feeling results by five test drivers were scored in the range of speed of 80 to 250 km / hour, and the conventional example 2 was set as 100 and displayed as an index. The larger this index value is, the better the high-speed steering stability is. When the index value was 106 or more, it was evaluated as having excellent high-speed maneuvering stability.

(Low rolling resistance)
Each test tire is assembled to an aluminum wheel with a rim size of 18 x 8J, filled with an air pressure of 230 kPa, and a drum tester with a drum diameter of 1707.6 mm is used in accordance with ISO28580, and 70% of the maximum load capacity specified by JATTA. The rolling resistance at a speed of 80 km / h was measured by applying the load of. The reciprocal of the rolling resistance of Conventional Example 2 was set to 100 and displayed as an exponential notation. The smaller the index, the better the rolling resistance. When the index value was 98 or less, it was evaluated as having excellent low rolling resistance.

The results are shown in Tables 1 and 2.
In Tables 1 and 2, when the cord structure is represented by using "+", the parts before and after the "+" are the fibers of the materials described before and after the "+" in the column of the cord material, respectively. Represents the fineness and number of fibers.
In the column of contraction stress, the contraction stress of the cord is shown, and for Examples 1 to 10, the contraction stress of each fiber of the cord is shown in parentheses in the order of the cord material.
In the column of tensile strength, the tensile strength of each fiber of the cord is shown in the order of the cord material.

The fibers of the cord material shown in Tables 1 and 2 are as follows.
・ N11: Castron manufactured by Unitika Ltd. ・ N66: Nylon 66 fiber manufactured by Asahi Kasei Co., Ltd. ・ PET: PET fiber manufactured by Hyosung Co., Ltd. The dimensions of the strip-shaped member were: thickness: 0.80 mm, width: 10 mm, and the number of hammers of 50 / cm.

From the comparison between Examples 1 to 10 and Conventional Example 2, when the cord of the belt cover layer has a nylon 11 fiber and another fiber having a shrinkage stress smaller than that of the nylon 11 fiber, the environmental load reduction is achieved. However, it can be seen that the deterioration of uniformity can be suppressed. In particular, from the comparison between Examples 4 to 10 and Examples 1 to 3, when the difference in shrinkage stress between the nylon 11 fiber and the other fibers is 100 cN / dtex or more, the deterioration of uniformity is suppressed while achieving the reduction of the environmental load. It can be seen that the effect of nylon can be enhanced.

Further, from the comparison of Examples 4 to 7, when the twist coefficient of the cord of the belt cover layer is 1100 to 2200, the effect of suppressing the deterioration of uniformity is particularly high, and the low rolling resistance is excellent. I understand. In particular, from the comparison between Examples 6 and 4, it can be seen that when the twist coefficient is 1100 to 1500, the effect of suppressing the deterioration of uniformity is extremely high, and the high-speed steering stability is excellent.

Further, from the comparison of Examples 4 and 8 to 10, it can be seen that when the non-petroleum resource ratio is 50 to 80%, the effect of suppressing the deterioration of uniformity is particularly high and the low rolling resistance is excellent.

Although the band-shaped member and the pneumatic tire of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various improvements and changes may be made without departing from the gist of the present invention. Of course.

1 Tread part 2 Side wall part 3 Bead part 4 Carcass ply layer 5 Bead core 6 Bead filler 7, 8 Belt layer 9 Belt cover layer 10 Pneumatic tire 11 Band-shaped member 13 Code 15 Coated rubber

Claims (3)

One code or multiple aligned codes,
With a coated rubber covering the cord,
The cord comprises at least one nylon 11 fiber and at least one fiber having a smaller shrinkage stress than the nylon 11 fiber.
The nylon 11 fiber and the fiber having a smaller shrinkage stress than the nylon 11 fiber are each under-twisted and twisted into an up-twist.
A strip-shaped member having a twist coefficient K of the cord calculated from the following formula (1) of 1100 to 1500 .
K = T × D ^1/2 ... (1)
(In the formula, T is the number of twists (times / 10 cm) of the cord, and D is the total fineness (dtex) of the cord.) The strip-shaped member according to claim 1 , wherein the proportion of the mass of the fiber made of a material derived from a resource other than petroleum resources in the cord is 80% or less. Pneumatic tires
With the belt layer,
A pneumatic tire that is arranged on the outer peripheral side of the belt layer and includes a belt cover layer in which the band-shaped member according to claim 1 or 2 is wound in the tire circumferential direction.

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