JP2012006499A - Pneumatic tire and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire and a method of manufacturing the same, for improving durability, by restraining the occurrence of a crack in a joining part of an inner liner layer, without hindering molding workability of the inner liner layer.SOLUTION: This pneumatic tire includes a composite sheet of laminating a film layer F and a rubber layer constituted of a thermoplastic resin or a thermoplastic elastomer composition, and is provided by arranging the inner liner layer formed by joining mutual end parts Sa and Sb of the composite sheet S by a splice, on a tire inner wall surface. The end part Sa on the tire inner surface side in a joining part of the composite sheet is folded back to the tire outer surface side, and this folding-back end part Sa is joined by the splice so as to cover with the end surface Sb on the tire outer surface side in the joining part.

Description

  The present invention relates to a pneumatic tire and a method for manufacturing the same, and more specifically, without inhibiting the molding workability of the inner liner layer and suppressing the occurrence of cracks at the joint portion of the inner liner layer, thereby improving durability. The present invention relates to a pneumatic tire and a manufacturing method thereof.

  In general, an inner liner layer made of a low air permeability rubber such as butyl rubber has been disposed on the inner wall surface of a pneumatic tire in order to keep the tire air pressure constant. However, in addition to the large hysteresis loss of butyl rubber, tires using this as an inner liner layer have a problem of increased rolling resistance due to their increased weight.

  As a countermeasure, it has been attempted to use a film layer made of a low-air-permeable thermoplastic resin or a thermoplastic elastomer composition instead of butyl rubber as the inner liner layer (see, for example, Patent Documents 1 and 2). ). However, when a film layer made of a thermoplastic resin or a thermoplastic elastomer composition is used as it is for the inner liner layer, there is a problem that the film layer easily deteriorates due to heat received from the bladder during vulcanization. Rubber has been coated to prevent the film layer from contacting the bladder directly.

  That is, when forming the inner liner layer, as shown in FIG. 7A, the ends of the laminate of the film layer F and the rubber layer G are spliced together and wound on a forming drum. I did it. However, the pneumatic tire provided with the inner liner layer formed in this way has cracks on the tire inner surface side of the splice joint as shown by the arrow in FIG. It was confirmed that it was likely to occur.

  The present inventor has pursued this cause. As shown in FIG. 7C, the rubber near the end of the rubber layer Ga on the tire inner surface side in the splice joint flows due to heat received from the bladder during vulcanization. Then, the end Fx of the film layer F on the inner surface side of the tire moves to the inner surface side of the tire, the rubber thickness x of this portion becomes thin, or the end Fx is exposed on the inner wall surface of the tire in some cases, and the tire running As the layers are stacked, peeling occurs between the terminal Fx of the film layer F and the rubber layer Ga due to the difference in rigidity between the film layer F and the rubber layer Ga, and cracks are generated due to the growth of the peeling. I figured out what to do.

  Based on this knowledge, the present inventor, in order to prevent the terminal Fx of the film layer F on the tire inner surface side from moving to the tire inner surface side due to heat during vulcanization, the rubber on the inner surface side of the tire at the splice joint portion. An attempt was made to attach a rubber tape so as to straddle the layer Ga and the rubber layer Gb on the outer surface side of the tire. However, since this method significantly reduces the workability for forming the inner liner layer, it has been found that the method is poor in practicality. As a next attempt, the terminal Fx of the film layer F on the tire inner surface side is connected to the splice joint portion. The present invention was completed after repeated experiments, paying attention to being positioned inside the.

JP-A-8-217923 WO2008 / 53747

  It is an object of the present invention to suppress the occurrence of cracks in the joint portion of the inner liner layer without impairing the molding workability of the inner liner layer, and to improve the durability, and a method for manufacturing the same Is to provide.

  In order to achieve the above object, the pneumatic tire of the present invention comprises a composite sheet obtained by laminating a film layer made of a thermoplastic elastomer composition or a thermoplastic elastomer composition obtained by blending an elastomer with a thermoplastic resin and a rubber layer. A pneumatic tire in which an inner liner layer formed by splicing the end portions of a sheet to each other is disposed on a tire inner wall surface, and the end portion on the tire inner surface side of the joint portion of the composite sheet is folded back toward the tire outer surface side. In addition, the folded end portion is spliced so as to be covered with the end portion on the tire outer surface side in the joint portion of the composite sheet.

  In addition, the method for producing a pneumatic tire of the present invention for achieving the above object includes splicing the ends of a film layer made of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer with a thermoplastic resin. In the method for manufacturing a pneumatic tire for forming an inner liner layer, after forming a composite sheet by pasting rubber layers on the upper and lower surfaces of the film layer in advance, the ends of the composite sheet are spliced together. The end portion on the tire inner surface side in the joint portion of the composite sheet is folded back to the tire outer surface side, and the folded end portion is joined so as to be covered with the end portion on the tire outer surface side in the joint portion.

  According to the present invention, the inner liner layer is constituted by a composite sheet obtained by laminating a film layer made of a thermoplastic resin or a thermoplastic elastomer composition and a rubber layer, and when the ends of the composite sheet are spliced to each other, Since the end of the tire inner surface side in the joint portion of the sheet is folded back to the tire outer surface side, and the folded end portion is spliced so as to cover the end portion of the tire outer surface side in the joint portion of the composite sheet. Since the rubber thickness between the tire inner wall surface and the film layer end is secured by positioning the end of the film layer at the end of the side on the tire outer wall surface side, without applying a new reinforcing member, The movement of the end of the film layer due to heat during vulcanization can be suppressed, without reducing the workability of the inner liner layer , It is possible to efficiently suppress the occurrence of cracks in the joint.

  And by setting the folding width of the end portion on the inner surface side of the tire to be 3 mm or more, it is possible to suppress the inclusion of air into the splice joint without impairing the molding workability, and to generate a blister failure. This can be prevented and an increase in tire weight can be suppressed by setting the folded width to 30 mm or less.

  In addition, by repeating the folding operation of the end portion on the tire inner surface side toward the tire outer surface side a plurality of times while being reversed and forming the folded end portion to be within 4 layers, the bonding strength of the composite sheet at the bonding portion It is possible to further prevent cracks from occurring.

It is a meridian half section view showing a structure of a pneumatic tire according to an embodiment of the present invention. It is sectional drawing which shows the structure of the inner liner layer in the pneumatic tire of FIG. It is sectional drawing for demonstrating the joining process in the junction part of the inner liner layer in the pneumatic tire of FIG. It is explanatory drawing which shows the arrangement | positioning form of the film layer in the junction part of the inner liner layer in the pneumatic tire of FIG. It is sectional drawing which shows the folding | turning form of the edge part of the composite sheet located in the tire inner surface side in the junction part of the inner liner layer by other embodiment of this invention. FIG. 4 is a cross-sectional view corresponding to FIG. 3 according to another embodiment of the present invention. (A)-(c) is sectional drawing which respectively shows the structure in the junction part of the conventional inner liner layer, (a) is the structure of the junction part on a forming drum, (b) is the junction part of the tire after driving | running | working. (C) has shown the structure in the junction part of the tire immediately after vulcanization.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a meridian half sectional view showing the structure of a pneumatic tire according to an embodiment of the present invention. In FIG. 1, a pneumatic tire 1 according to the present invention has a carcass layer 3 mounted between a pair of left and right bead portions 2, 2, and an inner liner layer 4 is disposed on the tire inner surface side of the carcass layer 3.

  As shown in FIG. 2, the inner liner layer 4 is composed of a composite sheet S in which a film layer F made of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer with a thermoplastic resin and a rubber layer G are laminated, The end portions of the composite sheet S are spliced to form the inner liner layer 4.

  And, in the present invention, when splicing the ends of the composite sheet S, as shown in FIG. 3, the end portion Sa on the tire inner surface side in the joint portion of the composite sheet S is folded back toward the tire outer surface side, The folded end portion Sx is spliced so as to be covered with the end portion Sb on the tire outer surface side in the joint portion of the composite sheet S. In addition, in FIG. 3, the state immediately before joining the edge parts of the composite sheet S is shown. Therefore, at the joint portion in the inner liner layer 4 after molding, the film layers F and F at the end portion Sa on the tire inner surface side and the end portion Sb on the tire outer surface side have an arrangement relationship as shown in FIG. .

  Thus, the end portion Sa on the tire inner surface side in the joint portion of the composite sheet S is folded back to the tire outer surface side, and the folded end portion Sx is spliced so that the end portion Sb on the tire outer surface side covers the film layer. By positioning the terminal Fx of the F on the tire outer surface side, a rubber thickness between the tire inner wall surface and the terminal Fx of the film layer F is ensured. Therefore, without applying a new reinforcing member, The movement of the terminal Fx of the film layer F to the tire inner wall side can be suppressed, and the occurrence of cracks at the joint can be efficiently suppressed without impairing workability during molding.

  In the present invention, a material having low air permeability is used for the thermoplastic resin or the thermoplastic elastomer composition constituting the film layer F, and a material having good adhesion to the film layer F is used for the rubber layer G. The In particular, it is preferable to use a material having low thermal conductivity for the rubber layer G located on the tire inner surface side of the composite sheet S.

  For the thermoplastic resin constituting the film layer F, polyamide resins, polyester resins, polynitrile resins, polymethacrylate resins, polyvinyl resins and the like are preferably used. For elastomers blended with thermoplastic resins, diene resins are used. Rubber, hydrogenated products thereof, olefinic rubber and the like are preferably used.

  Here, the weight ratio of the thermoplastic resin to the elastomer is not particularly limited, but preferably the weight ratio is set to 10/90 to 80/20, preferably 20/80 to 70/30. Then, it is preferable to adjust so that the elastomer component is uniformly dispersed as a discontinuous phase in the matrix of the thermoplastic resin.

  The rubber material constituting the rubber layer G includes diene rubbers such as natural rubber, isoprene rubber, epoxidized natural rubber, styrene butadiene rubber, hydrogenated styrene butadiene rubber, ethylene propylene rubber, and maleic acid modified ethylene propylene rubber. Olefin rubbers such as are preferably used.

  And in order to improve the adhesiveness with the adjacent rubber layer G, the said film layer F is good to laminate | stack with an adhesive layer intervening. As the polymer constituting the adhesive layer, acrylate copolymers such as ultrahigh molecular weight polyethylene having a molecular weight of 1 million or more, preferably 3 million or more, ethylene ethyl acrylate copolymer, ethylene methyl acrylate resin, ethylene acrylic acid copolymer, etc. And their maleic anhydride adduct, polypropylene and its maleic acid modification, ethylene propylene copolymer and its maleic acid modification, polybutadiene resin and its maleic anhydride modification, styrene-butadiene-styrene copolymer, styrene -Ethylene-butadiene-styrene copolymer, fluorine-based thermoplastic resin, polyester-based thermoplastic resin and the like are preferably used.

  In the present invention, the thickness of the film layer F is not particularly limited, but is usually set to about 0.002 to 0.3 mm. Also, the thickness of the rubber layer G is not particularly limited, but may be set to 0.1 to 1.8 mm, preferably 0.2 to 1.0 mm. Here, when the thickness of the rubber layer G is less than 0.1 mm, it is difficult to laminate the film layer F, and at the same time, the deterioration of the film layer F is suppressed by heat from the bladder during vulcanization. It becomes difficult, and if it exceeds 1.8 mm, it causes a weight increase of the tire.

  In the present invention, the folded width W (see FIG. 3) of the end portion Sa on the tire inner surface side in the joint portion of the composite sheet S may be set to 3 mm or more and 30 mm or less, preferably 5 to 15 mm. Here, if the turn-back width W is less than 3 mm, it becomes easy to embed air in the joint during molding, and this air causes a blister failure in the tire after vulcanization. Causes to increase.

  In the embodiment shown in FIG. 3 and FIG. 4 described above, the end portion Sa on the tire inner surface side in the joint portion of the composite sheet S is folded once toward the tire outer surface side, and the folded end portion Sx is formed in two layers. In the pneumatic tire 1 of the present invention, as shown in FIG. 5, the folding operation is repeated while being reversed a plurality of times (twice in the drawing), and the folded end Sx is It can be formed to be within 4 layers (3 layers in the figure). Thereby, since the rubber thickness between the tire inner wall surface and the terminal Fx of the film layer F is sufficiently secured, the joining strength of the composite sheet S at the joining portion is further strengthened, and the occurrence of cracks is surely prevented. be able to.

  Here, if the folded end portion Sx in the end portion Sa on the tire inner surface side described above has five or more layers, it becomes difficult to release the air embraced at the time of molding, causing a blister failure, and at the same time, The thickness of the inner liner layer 4 becomes too large, which causes the uniformity to deteriorate. As shown in FIG. 5, when the folded end Sx has three or more layers (three layers in the figure), the folded width W at the folded end Sx is made different for each layer within the above range. can do.

  FIG. 6 is a cross-sectional view corresponding to FIG. 3 according to another embodiment of the present invention. In this embodiment, the rubber layer Ga on the inner surface side of the folded end portion Sx in the end portion Sa on the tire inner surface side is removed and turned back. The total rubber thickness at the end Sx is reduced. Thereby, generation | occurrence | production of a blister failure can be suppressed efficiently, and a favorable uniformity can be ensured.

  In order to manufacture the pneumatic tire 1 of the present invention, first, as shown in FIG. 2, the upper and lower surfaces of the film layer F formed of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer with a thermoplastic resin are formed. A composite sheet S on which the rubber layer G is bonded is formed in advance.

  Next, the end portions of the composite sheet S are spliced together and wound on a forming drum to form the inner liner layer 4. Thereafter, an unvulcanized tire is molded while sequentially bonding various members constituting the tire to the outer peripheral surface side of the molded inner liner layer 4, and the molded unvulcanized tire is vulcanized.

  And in the manufacturing method of this invention, when joining the edge parts of the composite sheet S, the edge part Sa of the tire inner surface side in the junction part of the composite sheet S is turned back to the tire outer surface side so that it may illustrate in FIG. At the same time, the folded end portion Sx is spliced so as to be covered with the end portion Sb on the tire outer surface side in the joint portion.

  Thereby, since the terminal Fx of the film layer F which comprises the composite sheet S will be located in the tire outer surface side, the movement to the tire inner wall side of the terminal Fx of the film layer F at the time of vulcanization is restricted, and joining It is possible to suppress the occurrence of cracks in the part. In addition, according to this method, since it is not necessary to apply a new reinforcing member to the joint portion in order to restrict the movement of the terminal Fx of the film layer F, the molding workability of the inner liner layer 4 is not hindered. .

  As described above, according to the present invention, the inner liner layer is composed of a composite sheet obtained by laminating a film layer made of a thermoplastic resin or a thermoplastic elastomer composition and a rubber layer, and the ends of the composite sheet are spliced together. At the time, the end portion on the tire inner surface side in the joint portion is folded back to the tire outer surface side, and the folded end portion is spliced so as to be covered with the end portion on the tire outer surface side in the joint portion, thereby inhibiting the workability of the inner liner layer. Therefore, it is possible to improve the durability by suppressing the occurrence of cracks at the joint, and can be widely applied to high-performance vehicles that place importance on fuel efficiency in recent years.

  As shown in Table 1, the tire size is 195 / 65R15, the tire structure is FIG. 1, and the joining structure at the joining portion of the composite sheet S constituting the inner liner layer 4 and the folded form of the end portion Sa on the tire inner surface side are different as shown in Table 1. Thus, tires of the present invention (Examples 1 to 3) and comparative tires (Comparative Examples 1 to 3) were produced.

  In the tire of Comparative Example 3, the joining structure of the composite sheet S was set as butt joining, and a rubber tape (0.7 mm) straddling the end portions was bonded to the tire inner surface side of the joining portion. In each tire, the composite sheet S was configured as follows.

[Film layer F]
Thickness: 0.1mm
Material: Nylon 66 blended with brominated butyl rubber (weight ratio 45/55)
[Rubber layer G]
Thickness: 0.5mm
Material: Natural rubber

  For these six types of tires, the following test methods were used to form the inner liner layer, the occurrence of blister failure at the joint of the tire inner liner layer after vulcanization, and the inner liner layer of the tire after running. The occurrence of cracks at the joint was examined, and the results are also shown in Table 1. In addition, about the generation | occurrence | production condition of a crack, it performed by two steps after 20,000 km travel and after 40,000 km travel.

[Molding workability]
Four tires were prepared, the time required to form the inner liner layer was measured, and the average work time was used as the evaluation of molding workability. The evaluation results were classified into three stages of ○ (good), Δ (slightly reduced), and × (extremely reduced) according to the average time required for molding, and the results are also shown in Table 1.

[Blister failure occurrence status]
The joint portion of the inner liner layer in the vulcanized tire was observed, and the results are also shown in Table 1.

[Crack occurrence status]
Each of the vulcanized tires is filled with air pressure 210 kPa and mounted on the front and rear wheels of a domestic passenger car (Corolla) to carry a weight equivalent to 200 kg. The occurrence of cracks at the joint of the inner liner layer of the tire after running was observed, and the results are also shown in Table 1. In this test, the travel distance was varied in two stages.

  From Table 1, in the tires of the present invention (Examples 1 to 3), the occurrence of cracks at the joint portion of the inner liner layer is suppressed as compared with Comparative Example 1 in which the end portion Sa on the tire inner surface side is not folded back. I understand that.

  In Comparative Example 2 in which the turning width W of the end portion Sa on the tire inner surface side was set to 2 mm, a slight blister failure was observed at the joint portion of the inner liner layer in the vulcanized tire, and 40 A small number of cracks occurred in the tire after running for 1,000 km. Moreover, after making the junction part of a composite sheet butt-joining, it confirmed that the comparative example 3 which bonded the rubber tape on the tire inner surface side of the junction part has deteriorated shaping | molding workability | operativity and is not suitable for practical use. .

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Carcass layer 4 Inner liner layer F Film layer Fx Terminal G Rubber layer S Composite sheet Sa, Sb End part of composite sheet Sx Folded end part

Claims (4)

An inner liner layer formed of a composite sheet obtained by laminating a film layer made of a thermoplastic elastomer composition obtained by blending a thermoplastic resin or an elastomer and a thermoplastic resin and a rubber layer, and splicing the ends of the composite sheet to each other. Is a pneumatic tire arranged on the inner wall surface of the tire,
The end portion on the tire inner surface side in the joint portion of the composite sheet is folded back toward the tire outer surface side, and the folded end portion is spliced so as to be covered with the end portion on the tire outer surface side in the joint portion of the composite sheet. A featured pneumatic tire.   The pneumatic tire according to claim 1, wherein the width of the folded end portion of the composite sheet is 3 mm or more and 30 mm or less.   The pneumatic tire according to claim 1 or 2, wherein the folded end portion of the composite sheet is formed within 4 layers. In the method for producing a pneumatic tire, the inner liner layer is formed by splicing the ends of a film layer made of a thermoplastic elastomer composition in which an elastomer is blended with a thermoplastic resin or a thermoplastic resin,
After forming a composite sheet by pasting rubber layers on the upper and lower surfaces of the film layer in advance, when splicing the ends of the composite sheet to each other, the end portion on the tire inner surface side at the joint portion of the composite sheet Is folded back to the tire outer surface side, and the folded end portion is joined so as to be covered by the end portion of the joined portion on the tire outer surface side.

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