JP2010264878A - Pneumatic tire and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To add a high level of elongation characteristic and flexibility to a steel cord while raising the rate of use of resources other than petroleum, whereas restraining the occurrence of irregular molding and lowering of uniformity. <P>SOLUTION: A belt-like ply 10, in which a band cord arrangement is covered with topping rubber G, is provided outside a belt layer 7 in the tire radius direction while a band layer 9 is provided having at least one piece of band ply 9A spirally wound in the tire circumferential direction. A band cord 11 is composed of steel cords 20 in which a plurality (N number) of secondary strands 13 are twisted together by upper twists while the secondary strands 13 are formed by further twisting together by intermediary twisting a plurality (M number) of first strands 12 such that a plurality (L number) of steel strands f with a strand diameter d of 0.08 to 0.20 mm are twisted together by first twists. The steel cord 20, in its load-elongation curve, have a low elasticity area Y1 from the origin to inflection point P and a high elasticity area Y2 that extends beyond the inflection point P, while the elongation of the inflection point P falls within a range of 1.2 to 6.1%, with the elongation of 2 to 7% at the time of 90 N loading. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that is suitable as a four-wheel tire and can maintain the durability of a band layer while increasing the resource ratio outside of petroleum, and a method for producing the same.

  For example, a pneumatic tire for a passenger car is provided with a band layer on the outer side of the belt layer in order to enhance high-speed durability and steering stability. As the band layer, for example, a band layer using a jointless band ply formed by spirally winding a band-like ply in which a plurality of nylon cords arranged in parallel and covered with a topping rubber is known.

  In recent years, in consideration of global environmental problems, a tire with a high resource ratio outside oil (hereinafter, sometimes referred to as “eco-tire”) has been attracting attention (see, for example, Patent Document 1).

JP 2004-352995 A

  And in order to increase the non-oil resource rate, instead of nylon cords, which are petroleum resources, organic fiber cords, which are resources other than petroleum, such as plant-derived rayon cords such as wood pulp, are adopted as the band cords for the above-mentioned eco tires. Has been proposed. However, rayon cords have a significant decrease in strength due to humidity and a large change in elongation characteristics. Therefore, strict humidity and temperature management is required in the manufacturing process, resulting in an increase in cost. In addition, it is difficult to completely control the humidity and temperature, and it has to be affected to some extent by the decrease in the adhesive strength between the cord and rubber, the decrease in strength, and the increase in elongation. It is difficult to demonstrate.

  In view of such a situation, it has been proposed to adopt a steel cord. However, the tire stretch during the vulcanization process (hereinafter referred to as vulcanization stretch) is 3 to 4% in the case of a four-wheeled vehicle tire, which is larger than that of a two-wheeled vehicle tire. Therefore, when a conventional steel cord is used as the band cord, there is a problem in that it cannot sufficiently follow the vulcanized stretch, resulting in poor molding and a decrease in uniformity. In addition, since it lacks flexibility compared to organic fiber cords, it also adversely affects riding comfort.

  Therefore, the present invention is based on the use of a steel cord having an L × M × N structure made of steel wire having a wire diameter of 0.08 to 0.20 mm as a band cord, and has a high elongation that can sufficiently follow a vulcanized stretch. The purpose of the present invention is to provide a pneumatic tire capable of securing characteristics and flexibility, suppressing the deterioration of molding defects and uniformity while maintaining the resource ratio outside oil, and maintaining the ride comfort, and the manufacturing method thereof. Yes.

The invention according to claim 1 of the present invention includes a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, a belt layer disposed outside the carcass in the tire radial direction and inside the tread portion, A pneumatic tire having a band layer disposed outside the belt layer in the tire radial direction,
The band layer includes at least one band ply in which a band ply in which one or a plurality of band cords are arranged in parallel and covered with a topping rubber is spirally wound in a tire circumferential direction. ,
The band cord is
It consists of a steel cord in which a plurality of (N) secondary strands are twisted together by an upper twist, and the secondary strand is a plurality (L) of steel with a wire diameter d of 0.08 to 0.20 mm. A plurality of primary strands (M pieces) obtained by twisting strands with a primary twist are further twisted together with an intermediate twist,
The steel cord has a low elastic region from the origin to the inflection point and a high elastic region beyond the inflection point in the state of the steel cord alone before being covered with the topping rubber. In addition, the inflection point is in the range of 1.2 to 6.1% elongation, and the elongation at 90 N load is 2 to 7%.

According to a fourth aspect of the present invention, there is provided a carcass extending from a tread portion through a sidewall portion to a bead core of the bead portion, a belt layer disposed radially outside the carcass and inside the tread portion, and a tire of the belt layer A method of manufacturing a pneumatic tire having a band layer disposed radially outward,
Comprising a raw tire forming step for forming a raw tire, and a vulcanization step for heating and pressurizing the raw tire in a vulcanization mold to vulcanize and mold,
The raw tire forming step includes a winding step of spirally winding a belt-like ply in which a band cord array in which one or a plurality of band cords are arranged in parallel is covered with a topping rubber in a tire circumferential direction,
Moreover, the band cord is made of a steel cord in which a plurality (N) of secondary strands are twisted together by top twisting, and the secondary strand has a plurality of wires having a wire diameter d of 0.08 to 0.20 mm. It is formed by twisting together a plurality of primary strands (M) that are twisted together with (L) steel strands with a lower twist, and further twisted with an intermediate twist,
The steel cord has a low elastic region from the origin to the inflection point and a high elastic region beyond the inflection point in the state of the steel cord alone before being covered with the topping rubber. In addition, the inflection point is in the range of 1.2 to 6.1% elongation, and the elongation at 90 N load is 2 to 7%.

  In the inventions of claims 2 and 5, the number of the steel cords L, M, and N is in the range of 2 to 4, respectively.

  Further, in the invention of claims 3 and 6, the steel cord has a twist pitch of P1 and a twist pitch of the intermediate twist before the spiral winding in the tire circumferential direction and in the state of the steel cord alone, and the twist pitch of the intermediate twist is P2. When the twist pitch of the upper twist is P3, P1 <P2 <P3.

  The pneumatic tire of the present invention employs a steel cord made of non-oil resources as a band cord. Since this steel cord has an L × M × N twisted structure made of steel strands with a wire diameter of 0.08 to 0.20 mm, it ensures high elongation characteristics that can sufficiently follow the vulcanized stretch and flexibility. It becomes possible. Therefore, it is possible to increase the non-oil resource ratio in the tire, suppress molding defects and uniformity, and maintain riding comfort.

It is a tire meridian sectional view containing a tire axis of a pneumatic tire of this embodiment. It is a perspective view of the belt-like ply of this embodiment. It is sectional drawing which shows the structure of a band cord. It is a graph which shows the "load-elongation curve" of a band cord. It is a graph which shows the "load-elongation curve" of the band cord used for Table 1.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a pneumatic tire 1 according to the present embodiment includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and the carcass 6 outside in the tire radial direction and inside the tread portion 2. And a band layer 9 disposed on the outer side in the tire radial direction of the belt layer 7. In this example, the case where the said pneumatic tire 1 is a radial tire for passenger cars is illustrated.

  The carcass 6 includes one or more (in this example, one) carcass plies 6A having a radial structure in which organic fiber carcass cords are arranged at an angle of, for example, 80 to 90 ° with respect to the tire equator C. The carcass ply 6A includes a toroid-shaped main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and connected to the main body portion 6a and around the bead core 5 from the inner side in the tire axial direction to the outer side. And a folded portion 6b folded back. In order to increase the bending rigidity of the bead portion 4, a bead apex 8 made of hard rubber is provided between the main body portion 6 a and the turned-up portion 6 b.

  The belt layer 7 is formed of at least two belt cords in which a belt cord is inclined with respect to the tire equator C at a small angle of, for example, 10 to 40 °, and in this example, inner and outer belt plies 7A and 7B. . The belt plies 7 </ b> A and 7 </ b> B enhance the belt rigidity and firmly reinforce the tread portion 2 by overlapping the belt cords in the direction of crossing each other. A conventional steel cord is employed for the belt cord.

  Next, the band layer 9 is formed of at least one band ply 9A, in this example, one band ply 9A in which the band cord 11 is spirally wound in the tire circumferential direction.

  Specifically, the band ply 9A performs a winding process of spirally winding the narrow belt-like ply 10 shown schematically in FIG. 2 in the tire circumferential direction in a green tire forming process for forming a green tire. Formed by. The belt-like ply 10 is formed by covering one band cord 11 with a topping rubber G, or covering a band cord array in which a plurality of (for example, 4 to 8) band cords 11 are arranged in parallel with the topping rubber G. It is formed by. In the winding step, it is possible to wind the belts while overlapping the side edges of the belt-like ply 10 with each other, butting the side edges with each other, or separating the side edges. In this example, the band ply 9A is exemplified as a so-called full band ply that covers the entire width of the belt layer 7. For example, the band ply 9A is formed as an edge band ply that covers only both ends of the belt layer 7. Alternatively, the band layer 9 may be formed by combining these edge band ply and full band ply.

  And by performing the vulcanization process which vulcanizes and molds by heating and pressurizing in the vulcanization mold to the raw tire formed by the raw tire formation process including such a winding process, FIG. The already vulcanized pneumatic tire 1 shown is formed. Various conventional methods can be suitably employed as the vulcanizing step, green tire forming step, and winding step, and therefore detailed description thereof is omitted in this specification.

  The band cord 11 is characterized by using a steel cord 20 having an L × M × N structure as shown in FIG. Specifically, the secondary strand 13 is formed by twisting M strands of primary strands 12 in which a plurality (L) of steel strands f are twisted together by an intermediate twist, and further by forming an intermediate strand. The steel cord 20 is formed by twisting N pieces of the secondary strands 13 by top twisting.

  At this time, as the steel wire f, an extremely fine wire diameter d of 0.08 to 0.20 mm is employed. Each of the numbers L, M, and N is preferably in the range of 2 to 4, and more preferably L = 3, M = 3, and N = 3 in order to stabilize the twisted structure. If the numbers L, M, and N are less than 2, respectively, it becomes difficult to obtain a high elongation characteristic of the cord described later, and conversely if it exceeds 4, the flexibility is impaired and an unnecessary weight increase is caused.

  The steel cord 20 formed through the primary and secondary strands in this way has a high initial elongation because the degree of twist is higher than that of a conventional steel cord. Therefore, the “load-elongation curve” in the state of the steel cord alone before being covered with the topping rubber G, as shown in FIG. 4, is a low elastic region Y1 from the origin 0 to the inflection point P, and the inflection point. An elongation characteristic having a high elastic region Y2 exceeding P can be imparted to the cord.

  In addition, the position of the inflection point P can be shifted to a higher elongation side, and the elastic modulus in the low elastic region Y1 can be kept very low. Moreover, since such characteristics can be achieved by twisting, the elongation characteristics can be stabilized as compared with conventional steel cords that depend on the steel wire forming, and further, the elements resulting from the forming can be stabilized. It is also possible to stabilize the shape of the cord itself, for example, by suppressing line fluctuations. In addition, in order to obtain the elongation characteristics in which the inflection point P has shifted to the high elongation side, the twist pitch of the lower twist of the steel cord 20 is P1, the twist pitch of the intermediate twist is P2, and the twist pitch of the upper twist is When P3, it is preferable that P1 <P2 <P3.

  The steel cord 20 is composed of 6 or more (for example, 27) ultra-fine steel wires f, so that it can exhibit high flexibility (flexibility) and is the same as an organic fiber band cord. The excellent ride comfort can be ensured. Moreover, since it has the high elastic region Y2, during driving | running | working, the high restraint force to the tread part 2 can be exhibited, and high-speed durability and steering stability can be improved. In addition, since the rubber penetrates into the inside of the cord, the cord can be prevented from being damaged due to fretting, so that excellent cord durability can be exhibited.

  If the wire diameter d is less than 0.08 mm, the cutting load is reduced and it is difficult to obtain the required cord strength. Conversely, if it exceeds 0.20 mm, the position of the inflection point P is shifted to the high elongation side. It becomes difficult to obtain desired elongation characteristics.

And as the elongation characteristic of the cord required for the pneumatic tire 1 of the present embodiment, as shown in FIG. 4, in the “load-elongation curve” in the state of the steel cord alone, the inflection point P is It is important that the elongation e _P at the position is in the range of 1.2 to 6.1% and the elongation e ₉₀ at 90 N load is in the range of 2 to 7%.

Here, the elongation e _P at the location of the inflection point P is too low, so that the elongation of the band cord 11 produced during vulcanization occurs at high elastic region Y2. As a result, the extension of the band cord 11 cannot follow the vulcanized stretch, and the tire cannot be sufficiently pressed against the inner surface of the mold, resulting in a molding defect or a decrease in uniformity due to a reduction in molding accuracy. Arise. Or a cord break occurs. Further, since a tensile load of about 90 N is applied to the band cord 11 due to the vulcanized stretch, if the elongation e _{90 at} that time is too low, similarly, molding failure or uniformity is reduced. Conversely, elongation e _P at the position of the inflection point P is too high, or the elongation e ₉₀ is too high, insufficient binding force to the tread portion 2 by the band cord 11, high-speed durability is insufficient .

The lower limit of the elongation e ₉₀ is preferably 2.0% or more, more preferably 2.5 or more, and the upper limit is preferably 5.0% or less, more preferably 4.5% or less. Also, as the elongation _{e P,} the upper limit is 6.0% or less, more preferably 5.9% or less, and the lower limit is 1.3% or more, more preferably 1.4% or more.

  Here, the inflection point P is defined as follows. Each of the low elastic region Y1 and the high elastic region Y2 includes linear regions Y1a and Y2a in which the “load-elongation curve” extends substantially linearly, and an extension line of the linear region Y1a and an extension of the linear region Y2a. When the intersection point with the line is Pp, a point where a vertical line passing through the intersection point Pp intersects the “load-elongation curve” is defined as the inflection point P.

  In the band ply 9A, the number of cords driven per ply width of 5 cm is preferably in the range of 5 to 25.

  The topping rubber G is composed of a rubber component and an additive added to the rubber component. However, the topping rubber G is excellent in adhesiveness as the rubber component in order to enhance adhesion with the steel cord 20 and prevent damage such as cord peeling. Natural rubber and / or isoprene rubber (IR) are preferably used. Further, in the additive, it is desirable that sulfur as a vulcanizing agent is highly blended with 3 to 7 parts by mass, preferably 4.5 to 7 parts by mass with respect to 100 parts by mass of the rubber component. At this time, in order to prevent the high-mixed sulfur from being liberated as excess sulfur, the zinc white as a vulcanization aid is also highly blended with 5 to 15 parts by mass, preferably 8 to 15 parts by mass. Is desirable. Also, for the same purpose, organic acid cobalt salts such as cobalt naphthenate, cobalt stearate, cobalt oleate, cobalt laurate, cobalt tridecylate, cobalt palmitate and cobalt alanate are used to crosslink the cord and rubber. 0.5 to 3.0 parts by mass, preferably 1.0 to 3.0 parts by mass is preferable.

  Further, from the viewpoint of improving the non-petroleum resource ratio of the belt-like ply 10, the topping rubber G preferably comprises 95% or more of the total mass of the topping rubber G by non-petroleum resources.

  Specifically, natural rubber, which is a resource material other than petroleum, is used for the rubber component. The natural rubber includes so-called modified natural rubber whose molecular structure is improved. Among the additives, as a reinforcing agent, instead of conventional carbon black, inorganic fillers made of non-petroleum resource materials such as silica, sericite, calcium carbonate, clay, alumina, talc, magnesium carbonate, magnesium hydroxide, Aluminum hydroxide, magnesium oxide or titanium oxide can be preferably used. In particular, silica excellent in rubber reinforcement is desirable. However, a small amount of carbon black can be included as a reinforcing material.

When silica is used as the reinforcing agent, the BET specific surface area of the silica is preferably 150 to 250 m ² / g. When the BET specific surface area is less than 150 m ² / g, there is a tendency that a sufficient rubber reinforcing effect cannot be obtained. Conversely, when the BET specific surface area exceeds 250 m ² / g, dispersibility tends to decrease and aggregation tends to occur. Tends to decrease.

  Moreover, when replacing carbon black with the said inorganic filler, it is preferable to use a silane coupling agent together. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylpropyl) tetrasulfide, and 3-mercaptopropyltrisulfide. Examples thereof include ethoxysilane and 2-mercaptoethyltrimethoxysilane, and these may be used alone or in any combination. In particular, it is preferable to use bis (3-triethoxysilylpropyl) tetrasulfide or 3-mercaptopropyltriethoxysilane from the viewpoint of the reinforcing effect and processability of the silane coupling agent. It is particularly preferred to use (3-triethoxysilylpropyl) tetrasulfide.

  Among the additives, softeners include, for example, castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut water, rosin, pine oil, pineapple oil, tall oil, corn oil, and rice bran oil It is desirable to use vegetable oils such as bean flower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, coconut oil, jojoba oil, macadamia nut oil, safflower oil and / or tung oil. From the viewpoints of supply amount, price and softening effect, rapeseed oil, palm oil or palm oil is particularly desirable.

  In addition, as the softening agent, vegetable oils and fats with a low degree of unsaturation, especially semi-drying oils having an iodine value (grams of iodine that can be added to 100 g of fats and oils) of 100 to 130, Desirable are dry oil or solid fat. When the iodine value of fats and oils exceeds 130, the tan δ increases, leading to an increase in rolling resistance due to a decrease in hardness, and thus steering stability tends to decrease. When the iodine value is less than 100, the effect of softening the rubber is small, and it tends to be precipitated from the vulcanized rubber composition, and the physical property change tends to be large during heat aging.

  As mentioned above, although the especially preferable form 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.

A radial tire for a passenger car having the tire structure shown in FIG. 1 and using the band cord having the specifications shown in Table 1 was prototyped, and the high-speed durability of each sample tire was tested. The results are shown in Table 1. The common specifications are as follows.
Tire size: 195 / 65R15
Rim size: 15 × 6J
Internal pressure: 280 kPa
Strip ply:
Width: 11.0mm
Thickness: 1.49mm
Number of band cords driven: 6

Further, the composition of the topping rubber of the belt-like ply is as shown in Table 2, and details of each compounding material are as follows.
<Raw materials made from non-oil resources>
Rubber component ・ Natural rubber Reinforcing agent ・ Silica (Ultrazil VN3 manufactured by Degussa Huls Co., Ltd.)
Vulcanizing agent ・ Sulfur (powder sulfur manufactured by Tsurumi Chemical Co., Ltd.)
Vulcanization aid ・ Zinc flower (Zinc oxide, manufactured by Mitsui Mining & Smelting Co., Ltd.)
・ Stearic acid (stearic acid lees made by NOF Corporation)
Softener ・ Vegetable oil (refined palm oil J (S) manufactured by Nissin Oil Co., Ltd.)
Others ・ Cobalt of organic acid (cobalt stearate)
・ Coupling agent (Si-69 manufactured by Degussa Huls Co., Ltd.)
<Raw materials made of petroleum resources>
Rubber component ・ Isoprene rubber ・ Synthetic rubber SBR
Reinforcing agent ・ Carbon black (N326)
・ Carbon black (N219)
Softener ・ Process oil (Diana Process PS32 manufactured by Idemitsu Kosan Co., Ltd.)
Anti-aging agent ・ FR (Antigen FR manufactured by Sumitomo Chemical Co., Ltd.)
Vulcanization accelerator ・ DZ (Noxeller DZ manufactured by Ouchi Shinsei Chemical Co., Ltd.)
The test method is as follows.

<High speed durability>
In accordance with the load / speed performance test defined by ECE30 using a drum tester, the test was performed by the step speed method. In the test, the running speed was sequentially increased, and the speed (km / h) and time (minute) when the tire broke down were measured. In the evaluation, a tire that ran for 20 minutes or more at a speed of 200 (km / h) was accepted and the others were rejected. Tables 1 and 2 show the test results. FIG. 5 shows “load-elongation curves” of the band cords used in Comparative Examples 1 to 5 and Examples 1 to 4 in Table 1.

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 9A Band ply 10 Band-like ply 11 Band cord 12 Primary strand 13 Secondary strand 30 Steel cord C Tire equator f Steel strand G Topping rubber P Inflection point Y1 Low elasticity range Y2 High elasticity range

Claims (6)

A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, a belt layer disposed outside the carcass in the tire radial direction and inside the tread portion, and a band disposed outside the belt layer in the tire radial direction A pneumatic tire having a layer,
The band layer includes at least one band ply in which a band ply in which one or a plurality of band cords are arranged in parallel and covered with a topping rubber is spirally wound in a tire circumferential direction. ,
The band cord is
It consists of a steel cord in which a plurality of (N) secondary strands are twisted together by an upper twist, and the secondary strand is a plurality (L) of steel with a wire diameter d of 0.08 to 0.20 mm. A plurality of primary strands (M pieces) obtained by twisting strands with a primary twist are further twisted together with an intermediate twist,
The steel cord has a low elastic region from the origin to the inflection point and a high elastic region beyond the inflection point in the state of the steel cord alone before being covered with the topping rubber. And the inflection point is in the range of 1.2 to 6.1% elongation, and the elongation at 90 N load is 2 to 7%.   2. The pneumatic tire according to claim 1, wherein the number of the steel cords L, M, and N is in a range of 2 to 4, respectively.   In the state of the steel cord alone, the steel cord is P1 <P2 <P3, where P1 is the lower twist pitch, P2 is the intermediate twist pitch, and P3 is the upper twist pitch. The pneumatic tire according to claim 1 or 2, characterized by the above. A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, a belt layer disposed outside the carcass in the tire radial direction and inside the tread portion, and a band disposed outside the belt layer in the tire radial direction A method of manufacturing a pneumatic tire having a layer,
Comprising a raw tire forming step for forming a raw tire, and a vulcanization step for heating and pressurizing the raw tire in a vulcanization mold to vulcanize and mold,
The raw tire forming step includes a winding step of spirally winding a belt-like ply in which a band cord array in which one or a plurality of band cords are arranged in parallel is covered with a topping rubber in a tire circumferential direction,
Moreover, the band cord is made of a steel cord in which a plurality (N) of secondary strands are twisted together by top twisting, and the secondary strand has a plurality of wires having a wire diameter d of 0.08 to 0.20 mm. It is formed by twisting together a plurality of primary strands (M) that are twisted together with (L) steel strands with a lower twist, and further twisted with an intermediate twist,
The steel cord has a low elastic region from the origin to the inflection point and a high elastic region beyond the inflection point in the state of the steel cord alone before being covered with the topping rubber. And the said inflection point exists in the range of 1.2 to 6.1% of elongation, and also the elongation at the time of 90N load was made into 2 to 7%, The manufacturing method of the pneumatic tire characterized by the above-mentioned.   The method of manufacturing a pneumatic tire according to claim 4, wherein the number of the steel cords L, M, and N is in the range of 2 to 4, respectively.   In the state of the steel cord alone, the steel cord is P1 <P2 <P3, where P1 is the lower twist pitch, P2 is the intermediate twist pitch, and P3 is the upper twist pitch. The method for producing a pneumatic tire according to claim 4 or 5, characterized in that:

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