JP5039332B2 - Inner liner for pneumatic tire and pneumatic tire provided with the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an inner liner for a pneumatic tire and a pneumatic tire including the same, and more particularly to an inner liner for a pneumatic tire that is excellent in air permeation resistance and has dynamic fatigue durability suitable for use in cold regions. It is about.

  Conventionally, a rubber composition mainly composed of butyl rubber, halogenated butyl rubber or the like is used for an inner liner disposed as an air barrier layer on the tire inner surface in order to maintain the internal pressure of the tire. However, these rubber compositions using butyl rubber as the main raw material have low air barrier properties, so when such a rubber composition is used for the inner liner, the thickness of the inner liner has to be about 1 mm. For this reason, the weight of the inner liner in the tire is about 5%, which is an obstacle to reducing the weight of the tire and improving the fuel efficiency of the automobile.

  As a means for solving this problem, there is generally used a method of reducing the weight of the tire by using a thermoplastic resin excellent in gas barrier properties for the inner liner of the tire and suppressing the thickness of the inner liner. For example, JP-A-2002-52904 (Patent Document 1) discloses an ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 70 mol% and a saponification degree of 85% or more, and a hydrophobic plasticizer. A technique of using a resin composition comprising 1 to 40% by weight for an inner liner is disclosed. Japanese Patent Application Laid-Open No. 2004-176048 (Patent Document 2) reacts 1 to 50 parts by weight of an epoxy compound with 100 parts by weight of an ethylene-vinyl alcohol copolymer having an ethylene content of 25 to 50 mol%. A technique of using the resulting modified ethylene-vinyl alcohol copolymer for an inner liner is disclosed.

JP 2002-52904 A JP 2004-176048 A

  However, the present inventors have examined the inner liner of the above disclosure. For example, in a low temperature region such as −20 ° C., dynamic fatigue durability cannot be sufficiently obtained even if any inner liner is used. It was found that the internal pressure retention of the tire could not be maintained. Therefore, there is room for improvement in the dynamic fatigue durability of the inner liner used in cold regions.

  Therefore, an object of the present invention is to provide an inner liner for a pneumatic tire that solves the above-described problems of the prior art, has excellent air permeability, and has dynamic fatigue durability suitable for use in cold regions. It is in. Another object of the present invention is to provide a pneumatic tire provided with such an inner liner and having a significantly improved internal pressure retention property at the time of a new article and after running.

  As a result of intensive studies to achieve the above object, the present inventors have found that in a resin laminate used for an inner liner for a pneumatic tire, at least one layer constituting the resin laminate is a certain value or less under specific conditions. Thus, the present inventors have found that the dynamic fatigue durability in a low temperature region can be sufficiently obtained while maintaining the air permeation resistance, and thus the present invention has been completed.

That is, the inner liner for a pneumatic tire of the present invention is an inner liner for a pneumatic tire including a resin laminate composed of two or more layers,
At least one layer constituting the resin laminate is stretched to 18% at a temperature of −30 ° C. and a speed of 500 mm / min, left to stand for 15 seconds after the applied load is removed, and then 18 to the initial length. %, And after leaving it to stand for 10 more times, the residual strain caused by the inability to return to the original shape is 17.5% or less.

In a preferred example of the inner liner for a pneumatic tire of the present invention, at least one layer constituting the resin laminate is stretched to 18% at a temperature of −30 ° C. and a speed of 500 mm / min, and after removing the applied load, 15 seconds. The residual strain caused by the failure to return to the original shape after repeating the operation of extending and leaving for 18% with respect to the initial length for another 10 times is 15% or less. Here, it is preferable that at least one layer constituting the resin laminate has an oxygen permeability coefficient of 9.2 × 10 ⁻¹¹ cm ³ · cm / cm ² · s · cmHg or less at 20 ° C. and 65% RH.

  In another preferred embodiment of the inner liner for a pneumatic tire of the present invention, at least one layer constituting the resin laminate is a gas barrier layer containing an unmodified or modified ethylene-vinyl alcohol copolymer. The gas barrier layer comprises a resin composition in which a flexible resin having a Young's modulus of 500 MPa or less is dispersed in a matrix of a modified ethylene-vinyl alcohol copolymer obtained by reacting an ethylene-vinyl alcohol copolymer. Is preferred. Here, the ethylene content of the ethylene-vinyl alcohol copolymer is more preferably 25 to 50 mol%. In addition, it is more preferable that the modified ethylene-vinyl alcohol copolymer is obtained by reacting 1 to 50 parts by mass of an epoxy compound with respect to 100 parts by mass of the ethylene-vinyl alcohol copolymer. On the other hand, it is more preferable that the flexible resin dispersed in the modified ethylene-vinyl alcohol copolymer matrix has a functional group that reacts with a hydroxyl group, and the average particle size of the flexible resin is 2 μm or less. The content of the flexible resin in the resin composition is more preferably in the range of 10 to 30% by mass. In the above resin composition, the modified ethylene-vinyl alcohol copolymer is present as a matrix, where the matrix means a continuous phase.

  In the inner liner for a pneumatic tire of the present invention, when at least one layer constituting the resin laminate is the gas barrier layer, layers other than the gas barrier layer of the resin laminate are thermoplastic polyurethane (TPU) and nylon-based co-polymer. Polymer, unmodified or modified polyethylene (PE), unmodified or modified polypropylene (PP), polyethylene terephthalate (PET), syndiotactic 1,2-polybutadiene, styrene- (ethylene / butylene) -styrene block copolymer ( It is preferable to include at least one selected from the group consisting of SEBS) and styrene- (ethylene / propylene) -styrene block copolymer (SEPS).

  In another preferred embodiment of the inner liner for a pneumatic tire of the present invention, the resin laminate is crosslinked.

  The pneumatic tire of the present invention is characterized by using the above inner liner for a pneumatic tire.

  According to the present invention, in the inner liner for a pneumatic tire including a resin laminate including two or more layers, at least one layer constituting the resin laminate has a residual strain of a certain value or less under a specific condition. It is possible to provide an inner liner for a pneumatic tire having excellent air permeation resistance and capable of improving dynamic fatigue durability in a low temperature region. Further, it is possible to provide a pneumatic tire provided with such an inner liner and capable of significantly improving the internal pressure retention property at the time of a new article in a cold region and after running.

The present invention is described in detail below. The inner liner for a pneumatic tire of the present invention includes a resin laminate composed of two or more layers, and at least one layer constituting the resin laminate extends to 18% at a temperature of −30 ° C. and a speed of 500 mm / min. After removing the applied load, it was left for 15 seconds, and after the operation of extending and leaving it at 18% with respect to the initial length was further repeated 10 times, the residual strain caused by being unable to return to the original shape was observed. It is characterized by being 17.5% or less. Here, in the inner liner for a pneumatic tire of the present invention, by applying a resin laminate including at least one layer satisfying the above physical properties, dynamic fatigue durability in a low temperature region is improved, and at a low temperature The generation of cracks and cracks is suppressed, and as a result, the internal pressure retention of the tire can be greatly improved.

The resin laminate used for the inner liner for a pneumatic tire of the present invention forms a multilayer structure composed of two or more layers, wherein at least one layer forming the multilayer structure is 18 at a temperature of −30 ° C. and a speed of 500 mm / min. After removing the applied load, leaving it for 15 seconds, and then repeating the 18% extension and leaving operation for the initial length 10 more times, the original shape cannot be restored. It is necessary that the residual strain generated in 1 is 17.5% or less, preferably 15% or less, and more preferably 12.5% or less. If the residual strain exceeds 17.5%, the dynamic fatigue durability is lowered, so that cracks and cracks occur in the inner liner, which further deteriorates the internal pressure retention of the tire in cold regions. May bring.

Further, it is preferable that at least one layer constituting the resin laminate has an oxygen permeability coefficient of 9.2 × 10 ⁻¹¹ cm ³ · cm / cm ² · s · cmHg or less at 20 ° C. and 65% RH, More preferably, it is 0.0 × 10 ⁻¹¹ cm ³ · cm / cm ² · s · cmHg or less. When the oxygen permeability coefficient at 20 ° C. and 65% RH exceeds 9.2 × 10 ⁻¹¹ cm ³ · cm / cm ² · s · cm Hg, the inner pressure retention property of the tire is increased when used for the inner liner. The liner must be thick, and the weight of the tire cannot be reduced sufficiently. Furthermore, at least one layer constituting the resin laminate, 20 ° C., while satisfying the oxygen permeability coefficient is the specific range in the 65% RH, it is particularly preferred that the residual strain is 15% or less. Here, when at least one layer constituting the resin laminate satisfies the physical properties, the inner liner of the present invention can achieve both dynamic fatigue durability and air permeation resistance in a low temperature region.

  The resin laminate used for the inner liner for a pneumatic tire of the present invention is preferably made of a thermoplastic resin. Specifically, as the thermoplastic resin, an unmodified or modified ethylene-vinyl alcohol copolymer is specifically used. (EVOH), thermoplastic polyurethane (TPU), nylon copolymer, unmodified or modified polyethylene (PE), unmodified or modified polypropylene (PP), polyethylene terephthalate (PET), syndiotactic 1,2-polybutadiene, Preferable examples include styrene- (ethylene / butylene) -styrene block copolymer (SEBS) and styrene- (ethylene / propylene) -styrene block copolymer (SEPS). These thermoplastic resins may be used individually by 1 type, and may be used in combination of 2 or more type. The layers other than the gas barrier layer include thermoplastic polyurethane (TPU), nylon copolymer, unmodified or modified polyethylene (PE), unmodified or modified polypropylene (PP), polyethylene terephthalate (PET), syndiotactic. 1,2-polybutadiene, styrene- (ethylene / butylene) -styrene block copolymer (SEBS), styrene- (ethylene / propylene) -styrene block copolymer (SEPS), etc. are preferable, thermoplastic polyurethane (TPU), Use of a thermoplastic elastomer such as syndiotactic 1,2-polybutadiene, styrene- (ethylene / butylene) -styrene block copolymer (SEBS), styrene- (ethylene / propylene) -styrene block copolymer (SEPS), etc. Is more preferable.

  It is preferable that at least one layer constituting the resin laminate includes an unmodified or modified ethylene-vinyl alcohol copolymer from the viewpoint of enhancing the air permeation resistance. Since the unmodified or modified ethylene-vinyl alcohol copolymer has excellent air permeation resistance, the layer containing the unmodified or modified ethylene-vinyl alcohol copolymer can act as a gas barrier layer.

  Examples of the gas barrier layer containing the unmodified or modified ethylene-vinyl alcohol copolymer include a Young's modulus in a matrix of a modified ethylene-vinyl alcohol copolymer obtained by reacting an ethylene-vinyl alcohol copolymer. It is preferable to use a resin composition in which a flexible resin that is smaller than the ethylene-vinyl alcohol copolymer and preferably 500 MPa or less is dispersed. By using such a resin composition as a gas barrier layer, the air permeation resistance is maintained at a high level, the fracture resistance during bending is increased, and cracks are less likely to occur.

  The ethylene-vinyl alcohol copolymer preferably has an ethylene content of 25 to 50 mol%, more preferably 30 to 48 mol%, and still more preferably 35 to 45 mol%. If the ethylene content is less than 25 mol%, the bending resistance, fatigue resistance and melt moldability may be deteriorated. On the other hand, if it exceeds 50 mol%, sufficient air permeation resistance may not be ensured. The ethylene-vinyl alcohol copolymer preferably has a saponification degree of 90% or more, more preferably 95% or more, and even more preferably 99% or more. If the degree of saponification is less than 90%, the air permeation resistance and the thermal stability during molding may be insufficient. Furthermore, the ethylene-vinyl alcohol copolymer preferably has a melt flow rate (MFR) of 190 to 30 ° C. under a load of 2160 g, 0.1 to 30 g / 10 minutes, and 0.3 to 25 g / 10 minutes. More preferably.

  In the present invention, a method for producing the modified ethylene-vinyl alcohol copolymer is not particularly limited, but a production method in which the ethylene-vinyl alcohol copolymer and an epoxy compound are reacted in a solution is preferably exemplified. More specifically, a modified ethylene-vinyl alcohol copolymer is produced by adding an epoxy compound to a solution of an ethylene-vinyl alcohol copolymer in the presence of an acid catalyst or an alkali catalyst, preferably in the presence of an acid catalyst, and reacting. can do. Examples of the reaction solvent include aprotic polar solvents such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. Examples of the acid catalyst include p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, and boron trifluoride. Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, lithium hydroxide, Examples include sodium methoxide. The catalyst amount is preferably in the range of 0.0001 to 10 parts by mass with respect to 100 parts by mass of the ethylene-vinyl alcohol copolymer.

  As the epoxy compound to be reacted with the ethylene-vinyl alcohol copolymer, a monovalent epoxy compound is preferable. A divalent or higher-valent epoxy compound may undergo a crosslinking reaction with the ethylene-vinyl alcohol copolymer to generate gels, blisters, and the like, thereby reducing the quality of the inner liner. Note that glycidol and epoxypropane are particularly preferable among the monovalent epoxy compounds from the viewpoints of ease of production of the modified ethylene-vinyl alcohol copolymer, air permeation resistance, flex resistance, and fatigue resistance. Moreover, it is preferable that the said epoxy compound is made to react 1-50 mass parts with respect to 100 mass parts of ethylene-vinyl alcohol copolymers, It is still more preferable to react 2-40 mass parts, 5-35 mass parts It is more preferable to react.

  The modified ethylene-vinyl alcohol copolymer has a melt flow rate (MFR) of 190 ° C. and 0.130 g / 10 min under a load of 2160 g from the viewpoint of obtaining air permeation resistance, flex resistance and fatigue resistance. Preferably, it is 0.3 to 25 g / 10 min, more preferably 0.5 to 20 g / min.

  On the other hand, the flexible resin preferably has a Young's modulus of 500 MPa or less, and if the Young's modulus is 500 MPa or less, the elastic modulus of the gas barrier layer can be lowered, and as a result, the bending resistance can be improved. . Moreover, it is more preferable that the flexible resin has a functional group that reacts with a hydroxyl group, and the average particle diameter of the flexible resin is 2 μm or less. Since the flexible resin has a functional group that reacts with a hydroxyl group, the flexible resin is uniformly dispersed in the modified ethylene-vinyl alcohol copolymer, while the average particle diameter of the flexible resin exceeds 2 μm. In such a case, the flex resistance of the gas barrier layer may not be sufficiently improved, and the air permeation resistance may be lowered, and the internal pressure retention of the tire may be deteriorated. Here, examples of the functional group that reacts with a hydroxyl group include a maleic anhydride residue, a hydroxyl group, a carboxyl group, and an amino group. Specific examples of the flexible resin having a functional group that reacts with a hydroxyl group include maleic anhydride-modified styrene- (ethylene / butylene) -styrene block copolymer, maleic anhydride-modified ultra-low density polyethylene, and the like. In addition, the average particle diameter of the flexible resin in the resin composition is observed, for example, by freezing a sample, cutting the sample with a microtome, and observing with a transmission electron microscope (TEM). In addition, you may use a rubber component as a dispersed phase instead of this flexible resin.

  Furthermore, it is preferable that the content rate of the flexible resin in the said resin composition is the range of 10-30 mass%. When the content of the flexible resin is less than 10% by mass, the effect of improving the flex resistance is small. On the other hand, when the content exceeds 30% by mass, the air permeation resistance may be lowered.

  When at least one layer constituting the resin laminate is the gas barrier layer, a layer other than the gas barrier layer of the resin laminate is a protective layer from the viewpoint of suppressing the occurrence of cracks and cracks and improving the internal pressure retention of the tire. As thermoplastic polyurethane (TPU), nylon copolymer, unmodified or modified polyethylene (PE), unmodified or modified polypropylene (PP), polyethylene terephthalate (PET), syndiotactic 1,2-polybutadiene, styrene- It preferably contains (ethylene / butylene) -styrene block copolymer (SEBS) and styrene- (ethylene / propylene) -styrene block copolymer (SEPS).

  The resin laminate used for the inner liner for a pneumatic tire of the present invention is preferably supplied in the form of a film at the time of producing the inner liner, and the film is, for example, multilayered including the gas barrier layer and the protective layer. Preferably there is. Here, as a method of multilayering, for example, a method of co-extrusion of a resin composition containing a modified ethylene-vinyl alcohol copolymer and another thermoplastic elastomer, and the like, as other thermoplastic elastomer, A thermoplastic polyurethane etc. are mentioned.

  Moreover, it is preferable that the said resin laminated body is bridge | crosslinked. By cross-linking the resin laminate, it is possible to prevent the inner liner from being remarkably deformed and becoming non-uniform in the tire vulcanization process, and to improve the air permeation resistance of the inner liner. In addition, the residual strain in the low temperature region can be adjusted, and the dynamic fatigue durability in the low temperature region can be improved. Here, as a crosslinking method, a method of irradiating energy rays is preferable. Examples of the energy rays include ionizing radiation such as ultraviolet rays, electron beams, X-rays, α rays, γ rays, and among these, electron beams are used. Particularly preferred. The electron beam irradiation is preferably performed after the resin laminate is processed into a molded body such as a film or sheet. Here, the electron beam dose is preferably in the range of 5 to 500 kGy. If the electron beam dose is less than 5 kGy, crosslinking is difficult to proceed. On the other hand, if it exceeds 500 kGy, the upper limit of the residual strain in the present invention may be exceeded, and the molded product will easily deteriorate.

  As the inner liner of the pneumatic tire of the present invention, only a resin laminate may be used, but a layer made of a rubber composition may be bonded to the resin laminate via an adhesive layer. Here, the layer made of the rubber composition preferably contains butyl rubber and / or halogenated butyl rubber as a rubber component. In addition to the rubber component, a compounding agent usually used in the rubber industry, such as a reinforcing filler, is used. , Softeners, anti-aging agents, vulcanizing agents, vulcanization accelerators for rubber, scorch preventing agents, zinc white, stearic acid and the like can be appropriately blended depending on the purpose. On the other hand, examples of the adhesive used for the adhesive layer include a chlorinated rubber / isocyanate adhesive.

  The pneumatic tire of the present invention is characterized by using the above-described inner liner for a pneumatic tire. Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional view of an example of the pneumatic tire of the present invention. The tire shown in FIG. 1 has a pair of bead portions 1, a pair of sidewall portions 2, and a tread portion 3 connected to both sidewall portions 2, and extends in a toroid shape between the pair of bead portions 1. In addition, a carcass 4 composed of one or more carcass plies that reinforce each of these parts 1, 2, 3 is provided, and an inner liner 5 is disposed on the inner surface of the tire inside the carcass 4.

  In the illustrated example of the tire, the carcass 4 has a main body portion extending in a toroidal shape between a pair of bead cores 6 embedded in the bead portion 1, and around each bead core 6 from the inner side to the outer side in the tire width direction. In the pneumatic tire of the present invention, the number of plies and the structure of the carcass 4 are not limited to this.

  Further, in the illustrated tire, a belt 7 composed of two belt layers is disposed on the outer side in the tire radial direction of the crown portion of the carcass 4, and the illustrated belt 7 includes two belt layers. However, in the pneumatic tire of the present invention, the number of belt layers constituting the belt 7 is not limited to this. Here, the belt layer is usually composed of a rubberized layer of a cord extending obliquely with respect to the tire equatorial plane. In the two belt layers, the cords constituting the belt layer intersect with each other with the equator plane interposed therebetween. The belt 7 is thus laminated. Further, the illustrated tire includes a belt reinforcing layer 8 disposed so as to cover the entire belt 7 outside the belt 7 in the tire radial direction. The pneumatic tire of the present invention includes the belt reinforcing layer 8. It may not be necessary, and a belt reinforcing layer having another structure can be provided. Here, the belt reinforcing layer 8 is usually composed of a rubberized layer of cords arranged substantially parallel to the tire circumferential direction.

  The structure of the inner liner 5 in the illustrated tire will be described in detail with reference to FIG. FIG. 2 is a partial cross-sectional view of an example of the inner liner for a pneumatic tire of the present invention. The inner liner in the illustrated example is formed by bonding a resin laminate 9 and a layer 10 made of a rubber composition via an adhesive layer 11. Here, the layer 10 made of a rubber composition is joined to the tire inner surface inside the carcass 4 in the pneumatic tire. In addition, the inner liner of this invention will not be restrict | limited especially if it has the said resin laminated body 9, It does not need to have another component.

  In the illustrated inner liner, the resin laminate 9 is composed of, for example, a gas barrier layer 12 containing a modified ethylene-vinyl alcohol copolymer, and two layers of thermoplastic polyurethane disposed adjacent to the layer 12. A protective layer 13 is provided. Here, the resin laminate 9 is not particularly limited, and the components and the number of each layer are not limited thereto.

  The pneumatic tire of the present invention can be manufactured by a conventional method by applying the resin laminate described above to the inner liner 5 and, if necessary, a layer and an adhesive layer made of a rubber composition. In the pneumatic tire of the present invention, as the gas filled in the tire, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Synthesis example of modified ethylene-vinyl alcohol copolymer)
In a pressurized reaction vessel, ethylene-vinyl alcohol copolymer (EVOH) having an ethylene content of 44 mol% and a saponification degree of 99.9% (190 ° C., MFR under 2160 g load: 5.5 g / 10 min) 2 mass And 8 parts by mass of N-methyl-2-pyrrolidone were heated and stirred at 120 ° C. for 2 hours to completely dissolve the ethylene-vinyl alcohol copolymer. After adding 0.4 parts by mass of epoxypropane as an epoxy compound, the mixture was heated at 160 ° C. for 4 hours. After the heating, it was precipitated in 100 parts by mass of distilled water, and N-methyl-2-pyrrolidone and unreacted epoxypropane were sufficiently washed with a large amount of distilled water to obtain a modified ethylene-vinyl alcohol copolymer. Furthermore, the obtained modified ethylene-vinyl alcohol copolymer was fined to a particle size of about 2 mm with a pulverizer, and then sufficiently washed with a large amount of distilled water again. The washed particles were vacuum-dried at room temperature for 8 hours, and then melted at 200 ° C. using a twin-screw extruder to be pelletized.

The ethylene content and saponification degree of the ethylene-vinyl alcohol copolymer were measured by ¹ H-NMR using deuterated dimethyl sulfoxide as a solvent [using “JNM-GX-500 type” manufactured by JEOL Ltd.] This is a value calculated from the spectrum obtained in (1). Also, the melt flow rate (MFR) of the ethylene-vinyl alcohol copolymer was such that a sample was filled into a cylinder having an inner diameter of 9.55 mm and a length of 162 mm of a melt indexer L244 [manufactured by Takara Kogyo Co., Ltd.] After melting, an even load was applied using a plunger having a weight of 2160 g and a diameter of 9.48 mm, and the amount of resin extruded per unit time (g / g) from a 2.1 mm diameter orifice provided in the center of the cylinder. 10 minutes). However, when the melting point of the ethylene-vinyl alcohol copolymer is around 190 ° C. or exceeds 190 ° C., it is measured at a plurality of temperatures above the melting point under a load of 2160 g. Was plotted on the vertical axis, and the value calculated by extrapolating to 190 ° C. was taken as the melt flow rate (MFR).

(Synthesis example of flexible resin)
A maleic anhydride-modified styrene- (ethylene / butylene) -styrene block copolymer was synthesized by a known method and pelletized. The obtained maleic anhydride-modified styrene- (ethylene / butylene) -styrene block copolymer had a Young's modulus of 3 MPa, a styrene content of 20%, and a maleic anhydride amount of 0.3 meq / g. The Young's modulus of the maleic anhydride-modified styrene- (ethylene / butylene) -styrene block copolymer was measured by the following method.

(1) Measurement of Young's Modulus Using the obtained pellets, a twin film extruder manufactured by Toyo Seiki Co., Ltd. was used to produce a single-layer film having a thickness of 20 μm under the following extrusion conditions. Next, using this film, a strip-shaped test piece having a width of 15 mm was prepared and allowed to stand in a temperature-controlled room at 23 ° C. and 50% RH for one week, and then autograph [AG-A500 manufactured by Shimadzu Corporation]. Type] was used to measure an SS curve (stress-strain curve) at 23 ° C. and 50% RH under conditions of a chuck interval of 50 mm and a tensile speed of 50 mm / min, and the Young's modulus from the initial slope of the SS curve. Asked.

Screw: 20 mmφ, full flight cylinder, die temperature setting: C1 / C2 / C3 / die = 200/200/200/200 (° C.)

(Preparation of film 1)
Using the modified ethylene-vinyl alcohol copolymer pellets obtained in the synthesis example and thermoplastic polyurethane (TPU) [Kuraray Co., Ltd. Kuramylon 3190], using a two-kind three-layer coextrusion apparatus, A three-layer film 1 (thermoplastic polyurethane layer / modified EVOH layer / thermoplastic polyurethane layer, thickness: 20 μm / 20 μm / 20 μm) was produced under co-extrusion molding conditions.

Extrusion temperature of each resin: C1 / C2 / C3 / die = 170/170/200/200 ° C.
Extruder specifications for each resin:
Thermoplastic polyurethane: 25mmφ extruder P25-18AC [Osaka Seiki Machine Co., Ltd.]
Modified EVOH: 20 mmφ extruder lab machine ME type CO-EXT [manufactured by Toyo Seiki Co., Ltd.]
T-die specification: 500mm width, 2 types, 3 layers [Plastic Engineering Laboratory Co., Ltd.]
Cooling roll temperature: 50 ° C
Pickup speed: 4m / min

(Production of films 2 to 6)
The modified ethylene-vinyl alcohol copolymer obtained in the synthesis example and a flexible resin were kneaded with a twin screw extruder to prepare a resin composition. Next, the obtained resin composition and thermoplastic polyurethane (TPU) [Kuraray Co., Ltd. Kuramylon 3190] were used, and in the same manner as the production of film 1, three-layer films 2 to 2 having different TPU layer thicknesses were used. 6 (thermoplastic polyurethane layer / resin composition layer / thermoplastic polyurethane layer) was produced. Here, the content rate of the flexible resin in the resin composition is 20% by mass. The average particle size of the flexible resin in the resin composition was 0.7 μm on average when the sample of the obtained resin composition was frozen and then cut into sections with a microtome and measured with a transmission electron microscope. It was.

(Preparation of a layer comprising a rubber composition)
Brominated butyl rubber [Exxon Mobil Chemical, EXXON Bromobutyl 222] 100 parts by mass, carbon black N550 [Asahi Carbon Co., Ltd., Asahi # 60] 50 parts by mass, stearic acid [Shin Nippon Rika Co., Ltd. , Stearic acid 50S] 2 parts by mass, di-2-benzothiazolyl disulfide [Ouchi Shinsei Chemical Industry Co., Ltd., Noxeller DM] 1 part by mass, zinc white [Hux Itec Co., Ltd., zinc oxide 2 types powder Product] 3 parts by mass and sulfur [manufactured by Tsurumi Chemical Co., Ltd.] 0.5 parts by mass were prepared to prepare a rubber composition, and from the unvulcanized rubber composition having a thickness of 1000 μm using the rubber composition A layer was produced.

  The oxygen permeability coefficient of the layer consisting of the films 1 to 6 and the rubber composition obtained as described above and the residual strain of the films 1 to 6 were measured and evaluated by the following methods. The results are shown in Tables 1-2.

(2) Measurement of Oxygen Permeation Coefficient The layers made of the films 1 to 6 and the rubber composition were conditioned at 20 ° C. and 65% RH for 5 days. Using the two humidity-adjusted films obtained, using MOCON OX-TRAN 2/20 type manufactured by Modern Control Co., in accordance with JIS K7126 (isobaric method) under the conditions of 20 ° C. and 65% RH, The oxygen permeability coefficient was measured and the average value was obtained. Moreover, the oxygen permeation coefficient of each layer forming the film was determined in the same manner. Furthermore, the oxygen permeability coefficient of the layer made of the rubber composition was set to 1, and the oxygen permeability coefficient of the film was indicated as an index. It shows that it is excellent in air permeation resistance, so that an index value is large.

(3) Residual strain test Using an electron beam irradiation apparatus “Curetron EBC200-100 for production” manufactured by Nissin High Voltage Co., Ltd., with an acceleration voltage of 200 kV and an electron dose of film 1 under the conditions shown in Tables 1-2 6 was subjected to a crosslinking treatment by electron beam irradiation. The obtained cross-linked film was punched into a 10 mm × 130 mm strip with a marked line, and the film was stretched to 18% at a temperature of −30 ° C. and a speed of 500 mm / min using an autograph manufactured by Shimadzu Corporation. The load was removed and left for 15 seconds. Next, 18% of the initial film length and the operation of allowing to stand were repeated 10 times, and the residual strain (%) generated because the film could not return to its original shape was determined. Further, the residual strain of each layer alone forming the film was determined in the same manner.

(Examples 1-6, Comparative Example 2)
Using an electron beam irradiation apparatus “Production Curetron EBC200-100” manufactured by Nissin High Voltage Co., Ltd., the films 1 to 6 were irradiated with an electron beam under the conditions shown in Tables 1 and 2 with an acceleration voltage of 200 kV. Then, the crosslinking treatment was performed. Metallic R30M manufactured by Toyo Chemical Laboratories was applied as an adhesive layer on one side of the obtained crosslinked film and adhered to the inner surface of a layer (thickness: 1000 μm) made of the rubber composition to prepare an inner liner. Using the obtained inner liner, a pneumatic tire for a passenger car having a size of 195 / 65R15 having the structure shown in FIG. 1 was produced according to a conventional method. Tables 1 and 2 show the types of films used.

(Comparative Example 1)
A pneumatic tire for a passenger car was produced in the same manner as in Example 1 except that only the layer made of the rubber composition was used as the inner liner.

The tire obtained as described above was pressed at a load of 4.5 kN on a drum having a temperature of −20 ° C., an air pressure of 175 kPa and a rotation speed corresponding to a speed of 80 km / h, and traveled 10,000 km. Using a non-running tire and a tire after running, the internal pressure retention was evaluated as follows. The internal pressure retention was evaluated by mounting the test tire on a 6JJ × 15 rim, filling the internal pressure with 240 kPa, measuring the internal pressure after 3 months, and indexing with the following formula.
Internal pressure retention = (240−b) / (240−a) (index)
In the formula, a represents the internal pressure (kPa) after 3 months of the test tire, and b represents the internal pressure (kPa) after 3 months of the non-running tire described in Comparative Example 1.

  The appearance of the inner liner of the tire after running the drum was visually observed. The case where no failure was found by visual observation was judged good, and the case where cracks or cracks occurred, or peeling or lifting was seen as bad. These results are shown in Tables 1-2.

* 1 Indicates the thickness of the rubber composition layer.

  As is clear from Tables 1 and 2, it can be seen that the tires of the examples have significantly improved internal pressure retention before and after traveling compared to the tires of Comparative Example 1. Further, although the tire of Comparative Example 2 has excellent air permeation resistance, the residual strain after 18% repetitive stretching at −30 ° C. is high, so that the internal pressure is maintained after running in a low temperature region as compared with the tire of the Example. It can be seen that the properties are extremely low.

It is a fragmentary sectional view of an example of the pneumatic tire of the present invention. It is a fragmentary sectional view of an example of the inner liner for pneumatic tires of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Carcass 5 Inner liner 6 Bead core 7 Belt 8 Belt reinforcement layer 9 Resin laminated body 10 Layer which consists of rubber compositions 11 Adhesive layer 12 Gas barrier layer 13 Protective layer

Claims (12)

An inner liner for a pneumatic tire including a resin laminate composed of two or more layers,
At least one layer constituting the resin laminate is stretched to 18% at a temperature of −30 ° C. and a speed of 500 mm / min, left to stand for 15 seconds after the applied load is removed, and then 18 to the initial length. The inner liner for a pneumatic tire is characterized by having a residual strain of not more than 17.5% after being unable to return to its original shape after repeating the operation of% stretching and leaving for 10 more times . At least one layer constituting the resin laminate is stretched to 18% at a temperature of −30 ° C. and a speed of 500 mm / min, left to stand for 15 seconds after the applied load is removed, and then 18 to the initial length. 2. The inner liner for a pneumatic tire according to claim 1, wherein after the operation of% stretching and leaving is further repeated 10 times, the residual strain caused by the inability to return to the original shape is 15% or less. . At least one layer constituting the resin laminate has an oxygen transmission coefficient of 9.2 × 10 ⁻¹¹ cm ³ · cm / cm ² · s · cmHg or less at 20 ° C. and 65% RH. 2. An inner liner for a pneumatic tire according to 2.   The inner liner for a pneumatic tire according to claim 1, wherein at least one layer constituting the resin laminate is a gas barrier layer containing an unmodified or modified ethylene-vinyl alcohol copolymer.   The gas barrier layer is made of a resin composition in which a flexible resin having a Young's modulus of 500 MPa or less is dispersed in a matrix of a modified ethylene-vinyl alcohol copolymer obtained by reacting an ethylene-vinyl alcohol copolymer. The inner liner for a pneumatic tire according to claim 4.   The inner liner for a pneumatic tire according to claim 5, wherein the ethylene content of the ethylene-vinyl alcohol copolymer is 25 to 50 mol%.   The air according to claim 5, wherein the modified ethylene-vinyl alcohol copolymer is obtained by reacting 1 to 50 parts by mass of an epoxy compound with respect to 100 parts by mass of the ethylene-vinyl alcohol copolymer. Inner liner for entering tires.   6. The inner liner for a pneumatic tire according to claim 5, wherein the flexible resin has a functional group that reacts with a hydroxyl group, and the average particle size of the flexible resin is 2 μm or less.   The inner liner for a pneumatic tire according to claim 5, wherein the content of the flexible resin in the resin composition is in the range of 10 to 30% by mass.   Layers other than the gas barrier layer of the resin laminate are thermoplastic polyurethane, nylon copolymer, unmodified or modified polyethylene, unmodified or modified polypropylene, polyethylene terephthalate, syndiotactic 1,2-polybutadiene, styrene- (ethylene The inner liner for a pneumatic tire according to claim 4, comprising at least one selected from the group consisting of a / butylene) -styrene block copolymer and a styrene- (ethylene / propylene) -styrene block copolymer. .   The inner liner for a pneumatic tire according to claim 1, wherein the resin laminate is crosslinked.   The pneumatic tire provided with the inner liner for pneumatic tires in any one of Claims 1-11.

Images