JP2007160980A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of suppressing defects such as defects of an open carcass cord and air intrusion by increasing the bonding strength of the starting end with the terminating end of an inner liner rubber, and reducing the blending quantity of a tackifier. <P>SOLUTION: An inner liner rubber 10 has a three-layer structure consisting of an inner layer 10i adjacent to a carcass 6, an outer layer 10c forming an tire cavity surface Hs, and an intermediate layer 10m arranged between the inner layer 10i and the outer layer 10o. The inner layer 10i and the outer layer 10o consist of a natural rubber-based material in which a natural rubber of ≥50 pts.wt. is contained in the rubber component of 100 pts.wt. The intermediate layer 10m consists of a butyl rubber-based material in which a butyl rubber of ≥50 pts.wt. is contained in the rubber component of 100 pts.wt. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which an inner liner rubber is formed by a three-layer structure in which an intermediate layer made of a butyl rubber material is sandwiched between inner and outer layers made of a natural rubber material.

  In a tubeless pneumatic tire, an inner liner rubber forming a tire lumen surface is attached to the inner side of the carcass in order to keep the internal pressure air hermetically. And as this inner liner rubber, conventionally, a butyl rubber layer mainly composed of butyl rubber having excellent air permeation resistance and preventing tire air leaks by forming a tire lumen surface, and a natural rubber as a main component and A two-layer structure composed of a natural rubber layer that secures the adhesion between the butyl rubber layer and the carcass by being interposed between the butyl rubber layer and the carcass (see, for example, Patent Documents 1 and 2).

  On the other hand, when forming the raw tire, as shown in FIG. 4 (A), the inner liner rubber a is wound once in the tire circumferential direction in the unadded raw sheet state, and the winding of the starting end E1 of the winding is performed. The end portion E2 is overlapped and joined to the outside in the radial direction to form an annular shape. A carcass b is similarly formed on the outer side of the inner liner rubber a.

JP 61-60302 A JP 7-186608 A

  However, when the inner liner rubber a has a two-layer structure, the natural rubber layer ai and the butyl rubber layer ao inferior in adhesiveness are overlapped and joined at the joint J between the start end E1 and the end E2. The bonding strength is not sufficiently ensured. Therefore, in the next step, when the raw tire is inflated and shaped from an annular shape to a toroid shape, there is a problem in that a joining separation between the start end E1 and the end end E2 is likely to occur due to the tension T acting in the circumferential direction. . When this disengagement occurs, a so-called open carcass cord defect is caused in which the interval between the carcass cords b1 is unevenly widened. Further, as shown in FIG. 4B, shaping air d enters the inside of the tire from the joining portion J, and after vulcanization molding, the infiltrated air d becomes the inner liner rubber a. And incomplete air entry such as remaining between the carcass b and the side wall rubber.

  In order to suppress the occurrence rate of such defects, conventionally, it has been attempted to increase the bonding strength by adding a large amount of, for example, 10.0 phr of a tackifier to the butyl rubber layer. The reduction effect is inadequate, and there is a disadvantage that an increase in the amount of tackifier causes an increase in cost.

  Therefore, the present invention uses a three-layer structure in which the inner and outer layers of the butyl rubber layer are sandwiched between the inner and outer layers of the natural rubber layer as the inner liner rubber, and the blending amount of the tackifier is reduced. However, it becomes possible to sufficiently increase the bonding strength between the start and end parts of the inner liner rubber, suppress the bonding separation and air intrusion from the bonding part in the shaping process, such as defective open carcass cord and defective air An object of the present invention is to provide a pneumatic tire capable of reducing the occurrence rate of defects.

In order to achieve the object, the invention of claim 1 of the present application is a carcass extending from the tread portion to the bead core of the bead portion through the side wall portion, and located continuously inside the carcass and facing the tire lumen. A pneumatic tire having an inner liner rubber arranged as
The inner liner rubber includes an inner layer adjacent to the carcass, an outer layer forming a tire cavity surface, and an intermediate layer disposed between the inner layer and the outer layer, and the inner layer and the outer layer have a rubber component of 100 weight. It is made of a natural rubber material containing 50 parts by weight or more of natural rubber in the part, and the intermediate layer is made of a butyl rubber material containing 50 parts by weight or more of butyl rubber in 100 parts by weight of the rubber component. It is said.

  In the invention of claim 2, the intermediate layer has a thickness Tm in the range of 0.3 to 2.0 mm, and the inner layer and the outer layer have thicknesses Ti and To of 0.1 to 2 respectively. It is characterized by being in the range of 0 mm.

  As described above, in the present invention, as an inner liner rubber, an intermediate layer made of a butyl rubber-based material in which 50 parts by weight or more of butyl rubber is contained in 100 parts by weight of a rubber component, and 50 parts by weight of natural rubber in 100 parts by weight of a rubber component. A three-layer structure sandwiched by inner and outer layers made of a natural rubber-based material containing at least a part is adopted. Therefore, the inner and outer layers made of a natural rubber-based material having excellent adhesive strength overlap each other at the joint portion between the start end portion and the end portion of the inner liner rubber. Therefore, sufficient bonding strength can be ensured, and the occurrence rate of defects such as defective open carcass cords and defective air entering can be reduced while reducing the cost by reducing the blending amount of the tackifier.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a pneumatic tire according to the present invention.
As shown in FIG. 1, a pneumatic tire 1 according to this 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 is located inside the carcass 6 and tire. And at least an inner liner rubber 10 continuously arranged facing the inner cavity H.

  The carcass 6 is formed of one or more, in this example, one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction. The carcass ply 6A includes a series of ply turn-up portions 6b that are turned back from the inside in the tire axial direction around the bead core 5 at both ends of the ply body portion 6a straddling the bead cores 5 and 5. A bead apex rubber 8 is provided between the ply main body 6a and the ply turn-up portion 6b so as to taper outward from the bead core 5 in the radial direction, and is reinforced from the bead 4 to the sidewall 3. As the carcass cord, organic fiber cords such as nylon, polyester, rayon, aromatic polyamide, and steel cords are used.

  The belt layer 7 is formed of two or more belt plies 7A and 7B in which belt cords are arranged at, for example, about 10 to 35 ° with respect to the tire circumferential direction, and each belt cord is between plies. By crossing each other, the belt rigidity is enhanced, and the substantially entire width of the tread portion 2 is firmly reinforced with a tagging effect. As the belt cord, a steel cord is suitably employed. For example, a high modulus organic fiber cord such as polyethylene naphthalate (PEN), polyethylene terephthalate (PET), and aromatic polyamide can be used as necessary. Further, a band layer 11 in which a band cord is spirally wound at an angle of 5 degrees or less with respect to the circumferential direction is provided on the outer side in the radial direction of the belt layer 7 mainly for the purpose of improving high-speed durability. be able to.

  An inner liner rubber 10 is attached to the inner surface of the ply main body portion 6a of the carcass 6 so as to keep the tire filling internal pressure airtight by covering the tire lumen H.

  2, the inner liner rubber 10 includes an inner layer 10i adjacent to the inner surface of the ply main body portion 6a, an outer layer 10o that forms the tire cavity surface Hs, and a gap between the inner layer 10i and the outer layer 10o. It has a three-layer structure composed of an intermediate layer 10m. The inner layer 10i and the outer layer 10o are made of a natural rubber-based material in which 50 parts by weight or more, preferably 70 parts by weight or more of natural rubber is contained in 100 parts by weight of a rubber component. In this natural rubber-based material, diene rubbers such as butadiene rubber, styrene / butadiene rubber, isoprene rubber, chloroprene rubber, acrylonitrile butadiene rubber can be blended as the remaining rubber other than natural rubber.

  In contrast, the intermediate layer 10m is made of a butyl rubber material in which 50 parts by weight or more, preferably 70 parts by weight or more of butyl rubber is contained in 100 parts by weight of the rubber component. The butyl rubber can include halogenated butyl rubber which is a derivative of butyl rubber. In this butyl rubber material, natural rubber and the diene rubber can be blended as the remaining rubber other than butyl rubber. Various natural rubber additives such as vulcanizing agents, vulcanization accelerators, deterioration inhibitors and reinforcing fillers are added to the natural rubber material and butyl rubber material in order to ensure the necessary rubber properties. Although it can be blended as required, especially in butyl rubber-based materials, it is possible to reduce the blending amount of the tackifier to 5.0 phr or less, and further to 2.5 phr or less by adopting the three-layer structure. Therefore, the material cost can be reduced. As the tackifier, for example, coumarone resin, phenol resin, terpene resin, petroleum hydrocarbon resin, rosin derivative and the like are used.

  By forming the inner liner rubber 10 in a three-layer structure in this way, at the time of forming the raw tire, as shown in FIG. 3, at the joint J between the winding start end E1 and the end end E2 of the inner liner rubber 10 The inner layer 10i at the start end E1 and the outer layer 10o at the end E2 are overlapped with each other. At this time, since the inner layer 10i and the outer layer 10o are both formed of a natural rubber-based material having excellent adhesiveness, the bonding strength is large. Intrusion of air can be prevented, and occurrence of tire failures such as open carcass cord failure and air entry failure can be suppressed.

  Here, the intermediate layer 10m preferably has a thickness Tm in the range of 0.3 to 2.0 mm in order to exhibit necessary air permeation resistance. Insufficient performance tends to cause tire air leakage. On the other hand, if it exceeds 2.0 mm, the quality becomes excessive, and an unnecessary weight increase and cost increase tend to be caused. Therefore, the lower limit of the thickness Tm is more preferably 0.5 mm or more, and the upper limit is more preferably 1.8 mm or less. Further, in the inner layer 10i and the outer layer 10o, it is preferable that the thicknesses Ti and To are both in the range of 0.1 to 2.0 mm. If the thickness is 0.1 mm or less, the bonding strength at the bonding portion J is sufficiently high. It is difficult to increase. On the other hand, if it exceeds 2.0 mm, the quality becomes excessive, and an unnecessary weight increase and cost increase tend to be caused. Accordingly, the lower limit of the thicknesses Ti and To is more preferably 0.3 mm or more, and the upper limit is 1.0 mm or less, more preferably 0.8 mm or less. In particular, to suppress the increase in weight, the sum of the thicknesses Ti and To (Ti + To) should be less than the thickness of the natural rubber layer in the conventional inner liner rubber having a two-layer structure, for example, 1.0 mm or less. preferable.

  The thicknesses Ti and To of the inner layer 10i and the outer layer 10o may be set to be equal to each other. However, when Ti> To, a carcass is formed during vulcanization molding within a limited thickness (Ti + To). It is preferable in order to prevent the cord loose caused by the cord coming into contact with the butyl rubber material.

  Further, it is important that the joining strength is uniformly increased over the entire length of the joining portion J in the tire axial direction. For this reason, in the inner liner rubber 10, the entire length in the tire axial direction is It is necessary to form the thickness Ti and the thickness To substantially constant. The “substantially constant” allows variation due to component accuracy and variation due to rubber flow during vulcanization molding.

  The inner liner rubber 10 having the three-layer structure can be easily formed using, for example, a multilayer extrusion apparatus in which two or three or more extruder bodies are connected to an extrusion head. At this time, since the layers 10i, 10m, and 10o are integrally formed by extrusion, the bonding strength between the layers 10i, 10m, and 10o can be sufficiently ensured.

  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.

  1 and more than 5000 radial tires for passenger cars having the tire structure 215 / 45R17 having the tire structure shown in FIG. 1 are manufactured according to the specifications shown in Table 1. The incidence of was compared. The air permeability of the sample tire was tested and compared.

  Each tire uses the same composition in which 70 parts by weight of butyl rubber (butyl bromide) is contained in 100 parts by weight of the rubber component as the butyl rubber-based material of the inner liner rubber. In addition, a rubber composition having 70 parts by weight of natural rubber) in 100 parts by weight of a rubber component is used. The tires have the same specifications except for Table 1. Moreover, the tackifier shows the compounding quantity (phr) of the tackifier mix | blended with the butyl rubber-type material with the index | index which makes the prior art 1. As the tackifier, Resin R7510P manufactured by CECA was used.

<Air permeability>
The rate of decrease in internal pressure (%) when a sample tire is mounted on a rim (17 × 7JJ) and filled with internal pressure (200 kPa) and left to stand for 30 days is indicated by an index with the conventional tire as 100. . Smaller values are better.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is sectional drawing which expands an inner liner rubber | gum. It is sectional drawing which expands and shows the junction part of the start end part of winding of an inner liner rubber at the time of green tire formation, and a termination | terminus part. (A), (B) is sectional drawing of the junction part which shows the problem in the conventional inner liner rubber.

Explanation of symbols

2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 10 Inner liner rubber 10i Inner layer 10m Intermediate layer 10o Outer layer

Claims (2)

A pneumatic tire comprising a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and an inner liner rubber located inside the carcass and continuously arranged facing the tire lumen. There,
The inner liner rubber includes an inner layer adjacent to the carcass, an outer layer forming a tire cavity surface, and an intermediate layer disposed between the inner layer and the outer layer, and the inner layer and the outer layer have a rubber component of 100 weight. It is made of a natural rubber material containing 50 parts by weight or more of natural rubber in the part, and the intermediate layer is made of a butyl rubber material containing 50 parts by weight or more of butyl rubber in 100 parts by weight of the rubber component. And pneumatic tires.   The intermediate layer has a thickness Tm in the range of 0.3 to 2.0 mm, and the inner layer and the outer layer have thicknesses Ti and To in the range of 0.1 to 2.0 mm, respectively. The pneumatic tire according to claim 1.

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