JP5890615B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire using a thermoplastic resin film as an inner liner.

As an inner liner of a pneumatic tire, a rubber layer mainly composed of a butyl rubber having a low gas permeability (high gas barrier property) has been generally used, but with a recent demand for weight reduction of a tire, It has been proposed to use a thermoplastic resin film having a lower gas permeability.
For example, Patent Document 1 discloses a non-ventilated layer made of an ethylene-vinyl alcohol copolymer film (hereinafter sometimes referred to as EVOH) or a polyvinylidene chloride film having extremely low gas permeability and an adhesive made of polyethylene, polypropylene, or the like. An inner liner formed by laminating layers is described.

However, the inner liner made of this thermoplastic resin film lacks flexibility and sometimes fails to follow the expansion and contraction of the material during running of the tire, resulting in cracks. In order to solve this problem, various proposals have been made.
For example, in Patent Document 2, a thermoplastic resin film made of modified EVOH obtained by reacting an epoxy compound with EVOH is used as an inner liner, thereby lowering the elastic modulus of EVOH and causing breakage at the time of bending and generation of cracks. It has been proposed to prevent this. In Patent Document 3, the surface of the inner liner made of a thermoplastic resin film is subjected to surface oxidation treatment to improve the peel resistance and the rupture resistance during bending, thereby suppressing the occurrence of cracks. Has been proposed.

JP-A-6-040207 JP 2004-176048 A JP 2009-255601 A

In Patent Documents 2 to 3, the crack resistance of the thermoplastic resin film is improved from the viewpoint of modifying the thermoplastic resin film itself, but for further improvement of the crack resistance, from a different viewpoint. There is also a need for improved technology. In particular, since cracks are more likely to occur in a low temperature environment, there is a need for further technical improvements for improving crack resistance at low temperatures.
The present invention has been made under such circumstances, and provides a pneumatic tire using a thermoplastic resin film as an inner liner and having excellent crack resistance in a low temperature environment of the inner liner. For the purpose.

As a result of intensive studies to achieve the above object, the present inventors have intervened an adhesive layer containing a modified diene polymer having a glass transition temperature of −30 ° C. or lower between the inner liner and the carcass. And found that the purpose can be achieved.
The present invention has been completed based on such findings.

That is, the present invention
A pneumatic tire having an inner liner having a thermoplastic resin film, a carcass, and an adhesive layer between the inner liner and the carcass, wherein the adhesive layer comprises a modified diene polymer having a glass transition temperature of −30 ° C. or lower. Including pneumatic tires,
Is to provide.

  According to the present invention, it is possible to provide a pneumatic tire using a thermoplastic resin film as an inner liner and having excellent crack resistance at low temperatures.

It is a fragmentary sectional view showing an example of the pneumatic tire of the present invention. It is a partial expanded sectional view of the II section of FIG. It is a partial expanded sectional view which shows another example of the pneumatic tire of this invention.

[Pneumatic tire]
<Pneumatic tire structure>
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional view along the tread width direction and the tire radial direction showing an example of the pneumatic tire 10 of the present invention, and FIG. 2 is a partial enlarged cross-sectional view of FIG.

  The pneumatic tire 10 includes a bead core 1, a carcass 2 wound around the bead core 1, an inner liner 3 having a thermoplastic resin film disposed inside the carcass 2 in the tire radial direction, and the carcass 2. An adhesive layer 7 (not shown in FIG. 1) that is interposed between the inner liner 3 and the inner liner 3, and two belt layers 4 disposed on the outer side in the tire radial direction of the crown portion of the carcass 2. And a tread portion 5 and sidewall portions 6 disposed outside the belt portion in the tire radial direction.

In the pneumatic tire 10, the adhesive layer 7 includes a modified diene polymer having a glass transition temperature of −30 ° C. or lower.
As a result, the carcass 2 and the inner liner 3 are favorably bonded by the adhesive layer 7, and an increase in the elastic modulus of the adhesive layer 7 in a low-temperature environment is suppressed, and the low-temperature cracking property of the pneumatic tire is improved.
Next, the carcass 2, the thermoplastic resin film (inner liner 3), and the adhesive layer 7 will be described in detail in this order.

<Carcass 2>
The carcass 2 is composed of one or more carcass plies. The carcass ply has a structure in which fibers such as polyester are wrapped in a coating rubber.
The material for the coating rubber is not particularly limited, and for example, a diene rubber is used. Specific examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), cis-1,4-polybutadiene rubber (BR), and syndiotactic-1,2-polybutadiene rubber (1,2BR). ), Styrene-butadiene copolymer rubber (SBR), and the like. These diene rubbers may be used alone or in combination of two or more.

  For coating rubber, in addition to the above rubber components, compounding agents commonly used in the rubber industry, such as reinforcing fillers, softeners, anti-aging agents, vulcanizing agents, vulcanization accelerators for rubber, scorch inhibiting agents , Zinc white, stearic acid and the like can be appropriately blended according to the purpose. As these compounding agents, commercially available products can be suitably used.

<Inner liner 3>
The inner liner 3 has a thermoplastic resin film.

  The inner liner 3 may be composed of a single layer of a thermoplastic resin film (A layer), or may be composed of two or more multilayers of a thermoplastic resin film (A layer). This thermoplastic resin film You may consist of two or more layers of (A layer) and another layer. The other layer is preferably a layer (B layer) made of a resin composition containing a highly ductile elastomer. Thereby, even when the ductility of the thermoplastic resin film (A layer) is low, the overall ductility of the inner liner 3 can be increased.

  Hereinafter, a layer structure (multilayer structure) in the case where the inner liner 3 is composed of a multilayer, a thermoplastic resin film (A layer), a layer composed of a resin composition containing an elastomer (B layer), and the relationship between the A layer and the B layer The manufacturing method of the multilayer structure will be described in this order.

≪Layer structure (multilayer structure) ≫
The multilayer structure preferably includes a total of two or more layers of a thermoplastic resin film (A layer) and a layer (B layer) made of a resin composition containing an elastomer. As a result, it has a low gas permeable A layer and a highly ductile B layer, and the inner liner 3 as a whole is low gas permeable and has excellent crack resistance in a low temperature environment. It becomes.

  From this viewpoint and the manufacturing viewpoint, the total number of layers A and B is preferably 3 or more, more preferably 7 or more, still more preferably 17 or more, particularly preferably 25 or more, 48 More than one layer is particularly preferable, and 65 layers or more are very preferable. The multilayer structure may be a multilayer structure, and the total number of layers A and B may be 128 or more, 256 or more, 512 or more, or 1,024 or more. The upper limit of the total number of layers is appropriately selected depending on the use of the multilayer structure.

The multilayer structure can also have a C layer other than the A layer and the B layer. In addition, as the stacking order of the A layer and the B layer, for example,
(1) A, B, A, B... A, B (that is, (AB) _n )
(2) A, B, A, B... A (that is, (AB) _n A)
(3) B, A, B, A... B (that is, (BA) _n B)
(4) A, A, B, B... B, B (that is, (AABB) _n )
A stacking order such as can be adopted. Moreover, when it has other C layers, for example,
(5) A, B, C... A, B, C (that is, (ABC) _n )
A stacking order such as can be adopted. In the above (1) to (5), n is an integer of 1 or more.

  In particular, as the stacking order of the A layer and the B layer, it is preferable that the A layer and the B layer are alternately stacked as in the above (1), (2), or (3). The layered body in which the A layer and the B layer are alternately stacked in this way may be irradiated with active energy rays, thereby improving the bonding property between the stacked layers and exhibiting high adhesiveness. it can. As a result, the interlayer adhesion of the multilayer structure, as well as the low gas permeability and the bending resistance, can be significantly improved. Moreover, since A layer is pinched | interposed into B layer from both surfaces by laminating | stacking A layer and B layer alternately, the ductility of A layer is improved more.

  In this multilayer structure, the average thickness of each layer of the A layer and the B layer is preferably 0.001 to 10 μm, and more preferably 0.001 to 40 μm. By setting the average thickness of one layer of the A layer and the B layer in the above range, the number can be increased even when the entire thickness of the multilayer structure is the same. Property, bending resistance, and the like can be further improved.

  In the multilayer structure, since the B layer made of the resin composition containing the elastomer is laminated together with the A layer having the thickness in the above range, the ductility of the gas barrier resin itself is low even when the ductility of the gas barrier resin is low. The ductility of A layer which consists of a low resin composition can be improved more. This is presumably because the resin layer having low ductility is transferred to a highly ductile state by thinly laminating the layer A made of the resin composition having low ductility on the layer B having excellent ductility. The present inventor pays attention to the above fact, and the A layer is generally made of a material having low ductility. Thus, by making the thickness of each layer very thin, low gas permeability and bending resistance required for the inner liner are obtained. And a high degree of compatibility. Therefore, even when the multilayer structure is used after being deformed such as bending, characteristics such as low gas permeability can be maintained.

  The lower limit of the average thickness of the A layer is 0.001 μm, preferably 0.005 μm, and more preferably 0.01 μm. On the other hand, the upper limit of the average thickness of the single layer A is 10 μm, preferably 7 μm, more preferably 5 μm, further preferably 3 μm, further preferably 1 μm, further preferably 0.5 μm, 0.2 μm and further 0 .1 μm is particularly preferable, and 0.05 μm is most preferable.

  If the average thickness of one layer A is smaller than the above lower limit, it becomes difficult to mold with a uniform thickness, and the low gas permeability and bending resistance of the multilayer structure may be reduced. Conversely, if the average thickness of the single layer A exceeds the upper limit, the durability and crack resistance of the multilayer structure may be reduced when the thickness of the entire multilayer structure is the same. Moreover, when the average thickness of one A layer exceeds the said upper limit, there exists a possibility that the ductility improvement of A layer mentioned above may not fully express. In addition, the average thickness of one layer of A layer means the value which remove | divided the sum total of the thickness of all the A layers contained in the said multilayered structure by the number of layers of A layer.

  The lower limit of the average thickness of the B layer is 0.001 μm, but 0.005 μm is preferable and 0.01 μm is more preferable for the same reason as the A layer. On the other hand, the upper limit of the average thickness of the B layer is 40 μm, preferably 30 μm, and more preferably 20 μm or less. If the average thickness of one layer B exceeds the above upper limit, the durability and crack resistance of the multilayer structure may be reduced when the thickness of the entire multilayer structure is the same. In addition, the average thickness of one layer of B layer means the value which remove | divided the sum total of the thickness of all the B layers contained in the said multilayered structure by the number of layers of B layer.

  Regarding the average thickness of the B layer, the ratio of the average thickness of the B layer to the average thickness of the A layer (B layer / A layer) is preferably 1/3 or more, more preferably 1/2 or more. It is more preferable. Further, the ratio is preferably 1 or more, that is, the average thickness of one layer B is more than or equal to the average thickness of one layer A, more preferably 2 or more. By making the ratio of the thicknesses of the A layer and the B layer in this way, the bending fatigue characteristics until the multilayer structure reaches the entire layer breakage is improved.

  The thickness of the multilayer structure is preferably 0.1 μm or more and 1,000 μm or less, more preferably 0.5 μm or more and 750 μm or less, and further preferably 1 μm or more and 500 μm or less. By making the thickness of the multilayer structure in the above range, while maintaining the average thickness of one layer of the A layer and B layer in the above range, while maintaining the applicability to an inner liner of a pneumatic tire, etc. Gas barrier properties, flex resistance, crack resistance, durability, stretchability, and the like can be further improved. Here, the thickness of the multilayer structure is obtained by measuring the thickness of the cross section at an arbitrarily selected point of the multilayer structure.

≪Thermoplastic resin film (A layer) ≫

In the thermoplastic resin film (A layer), a flexible resin (A2) having a dynamic storage elastic modulus E ′ at −20 ° C. lower than that of the thermoplastic resin (A1) is dispersed in a matrix made of the thermoplastic resin (A1). The resin composition (A3) may contain at least a layer.
Here, the “dynamic storage elastic modulus E ′ at −20 ° C.” is a condition of initial strain 10%, dynamic strain 0.1%, frequency 15 Hz, −20 ° C. using a spectrometer manufactured by Ueshima Seisakusho. It is the dynamic storage elastic modulus E ′ measured in (1).
As the thermoplastic resin (A1), the dynamic storage elastic modulus E ′ at −20 ° C. preferably exceeds 1 × 10 ⁸ Pa. Specifically, the polyamide resin, the polyvinylidene chloride resin, the polyester resin , Thermoplastic urethane elastomers, ethylene-vinyl alcohol copolymer resins, and the like. Among these, ethylene-vinyl alcohol copolymer resins are preferable. Such an ethylene-vinyl alcohol copolymer-based resin has a low air permeability and a very good low gas permeability. In addition, these mature plastic resins (A1) may be used individually by 1 type, and may be used in combination of 2 or more type.

On the other hand, the flexible resin (A2) requires that the dynamic storage elastic modulus E ′ at −20 ° C. is lower than that of the thermoplastic resin (A1), and is preferably 1 × 10 ⁸ Pa or less. When the pressure is not more than 10 ⁸ Pa, the elastic modulus of the thermoplastic resin film (A layer) can be lowered, and as a result, the crack resistance and the bending resistance in a low temperature environment can be improved.
Moreover, it is preferable that the said flexible resin (A2) has a functional group which reacts with a hydroxyl group. When the flexible resin (A2) has a functional group that reacts with a hydroxyl group, the flexible resin (A2) is uniformly dispersed in the thermoplastic resin (A1). 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 (A2) having a functional group that reacts with a hydroxyl group include maleic anhydride-modified hydrogenated styrene-ethylene-butadiene-styrene block copolymer, maleic anhydride-modified ultra-low density polyethylene, and the like. It is done.
Furthermore, the flexible resin (A2) preferably has an average particle size of 2 μm or less. If the average particle size of the flexible resin (A2) exceeds 2 μm, the bending resistance of the thermoplastic resin film (A layer) may not be sufficiently improved, the gas barrier property is lowered, and the internal pressure of the tire is maintained. May cause sexual deterioration. In addition, the average particle diameter of the flexible resin (A2) in the thermoplastic resin film (A layer) is observed, for example, by freezing the sample, cutting the sample with a microtome, and observing with a transmission electron microscope (TEM).

  The content of the flexible resin (A2) in the thermoplastic resin film (A layer) is preferably in the range of 10 to 30% by mass. When the content of the flexible resin (A2) is less than 10% by mass, the effect of improving the bending resistance is small, whereas when it exceeds 30% by mass, the gas permeability may be increased.

  The ethylene-vinyl alcohol copolymer-based resin is preferably a modified ethylene-vinyl alcohol copolymer obtained by, for example, reacting an ethylene compound with an ethylene-vinyl alcohol copolymer. Such a modified ethylene-vinyl alcohol copolymer has a low elastic modulus as compared with a normal ethylene-vinyl alcohol copolymer, so it has high fracture resistance at the time of layer bending and excellent crack resistance in a low temperature environment. Yes.

  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%, the gas barrier properties may not be sufficiently secured. 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%, gas barrier properties and thermal stability during molding may be insufficient. Further, the ethylene-vinyl alcohol copolymer preferably has a melt flow rate (MFR) of 0.1 to 30 g / 10 min at 190 ° C. under a load of 2160 g, and 0.3 to 25 g / 10 min. 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, trifluoromeckensulfonic acid, sulfuric acid, and boron trifluoride. Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, and lithium hydroxide. Sodium methoxide and the like. 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 crosslink with the ethylene-vinyl alcohol copolymer to generate gels, blisters, and the like, thereby reducing the crystallinity of the inner liner. Of the monovalent epoxy compounds, glycidol and epoxypropane are particularly preferred from the viewpoints of ease of production of the modified ethylene-vinyl alcohol copolymer, gas barrier properties, 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 gas barrier properties, flex resistance and fatigue resistance. It is preferable that it is 0.3 to 25 g / 10 min, more preferably 0.5 to 20 g / 10 min.

  The thermoplastic resin film (A layer) is prepared by melt-molding, preferably T-die method, inflation method, after preparing a resin composition (A3) by kneading a mature plastic resin (A1) and a flexible resin (A2). The film can be formed into a film, a sheet or the like at a melting temperature of preferably 150 to 270 ° C. by extrusion molding. In addition, the thermoplastic resin film (A layer) may be a single layer or a multilayered layer as long as it includes a layer made of the resin composition (A3). Here, as a method of multilayering, a co-extrusion method and the like can be mentioned.

  In the laminated body of the present invention, it is preferable to further include one or more layers made of a thermoplastic urethane-based elastomer from the viewpoint of water resistance and adhesion to rubber. Here, the said thermoplastic urethane type elastomer is obtained by reaction of a polyol, an isocyanate compound, and a short chain diol. A polyol and a short chain diol form a linear polyurethane by an addition reaction with an isocyanate compound. The polyol becomes a flexible part in the thermoplastic urethane-based elastomer, and the isocyanate compound and the short-chain diol become a hard part. Note that the properties of thermoplastic urethane elastomers can be changed over a wide range by changing the type, blending amount, polymerization conditions, and the like of raw materials. Suitable examples of the thermoplastic urethane elastomer include polyether urethane.

Further, the thermoplastic resin film (A layer), 20 ° C., preferably oxygen permeation coefficient is not more than ^{3.0 × 10- 12 cm 3 / cm} 2 · sec · cmHg at 65% RH, 1.0 × more preferably 10- ¹² cm ³ / cm is ² · sec · cmHg or less, and more preferably ^{5.0 × 10 -13 cm 3 / cm} 2 · sec · cmHg or less. 20 ° C., in using the oxygen permeability at 65% RH exceeds ^{3.0 × 10- 12 cm 3 / cm} 2 · sec · cmHg, the thermoplastic resin film (A layer) as an inner liner, the tire In order to enhance the internal pressure retention characteristics, the thermoplastic resin film (A layer) must be thickened, and the weight of the tire cannot be sufficiently reduced.

  Furthermore, the thermoplastic resin film (A layer) is preferably cross-linked. When the thermoplastic resin film (A layer) is not cross-linked, the laminate (inner liner) is significantly deformed and becomes non-uniform in the tire vulcanization process, and the gas barrier property and bending resistance of the thermoplastic resin film (A layer) And fatigue resistance may deteriorate. 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 thermoplastic resin film (A layer) is processed into a molded body such as a film or sheet. Here, the dose of the electron beam is preferably in the range of 10 to 60 Mrad, and more preferably in the range of 20 to 50 Mrad. When the electron beam dose is less than 10 Mrad, the crosslinking is difficult to proceed. On the other hand, when the dose exceeds 60 Mrad, the molded body is likely to deteriorate. In addition, the thermoplastic resin film (A layer) may be subjected to a surface treatment by an oxidation method, a concavo-convex method or the like in order to improve the adhesiveness with the adhesive layer. Examples of the oxidation method include corona discharge treatment, plasma discharge treatment, chromic acid treatment (wet), flame treatment, maturation wind treatment, ozone, ultraviolet irradiation treatment, and the like. Etc. Among these, corona discharge treatment is preferable.

≪Layer made of resin composition containing elastomer (B layer) ≫
The inner liner made of the multilayer structure preferably contains one or more layers (B layer) made of a resin composition further containing an elastomer from the viewpoint of water resistance and adhesion to rubber. As this elastomer, it is preferable to use a thermoplastic elastomer for melt molding.

Examples of the thermoplastic elastomer include polystyrene thermoplastic elastomers, polyolefin thermoplastic elastomers, polydiene thermoplastic elastomers, polyvinyl chloride thermoplastic elastomers, chlorinated polyethylene thermoplastic elastomers, polyurethane thermoplastic elastomers (hereinafter referred to as thermoplastic elastomers). , Sometimes referred to as “TPU”), at least one selected from the group consisting of polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and fluororesin-based thermoplastic elastomers. Among these, from the viewpoint of ease of molding, from the group consisting of polystyrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polydiene-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers and polyamide-based thermoplastic elastomers. At least one selected from the above is preferably used, and a polyurethane-based thermoplastic elastomer is more preferably used.
Here, the polyurethane-based thermoplastic elastomer is obtained by a reaction of a polyol, an isocyanate compound, and a short-chain diol. A polyol and a short chain diol form a linear polyurethane by an addition reaction with an isocyanate compound. The polyol becomes a flexible part in the thermoplastic urethane-based elastomer, and the isocyanate compound and the short-chain diol become a hard part. Note that the properties of thermoplastic urethane elastomers can be changed over a wide range by changing the type, blending amount, polymerization conditions, and the like of raw materials. Suitable examples of the thermoplastic urethane elastomer include polyether urethane.

≪Relationship between A layer and B layer≫
In the multilayer structure, the peel resistance between the A layer and the B layer was measured at 23 ° C. and 50% RH atmosphere at a tensile rate of 50 mm / min after heating at 180 ° C. for 15 minutes and in accordance with JIS-K6854. Is preferably 25 N / 25 mm or more, more preferably 27 N / 25 mm or more, still more preferably 30 N / 25 mm or more, and particularly preferably 50 N / 25 mm or more. Thus, the A layer and the B layer have very good interlayer adhesion.

  Regarding the interlayer relationship of the multilayer structure, it is considered that the cross-linking reaction between molecules occurs at the interface between the A layer and the B layer by irradiation of active energy rays, and it is considered that they are firmly bonded, and high interlayer adhesion is exhibited. Is done.

<Method for producing multilayer structure>
The method for producing the multilayer structure is not particularly limited as long as the A layer and the B layer are laminated and bonded satisfactorily. For example, known methods such as co-extrusion, bonding, coating, bonding, and adhesion are known. This method can be adopted. Specifically, the method for producing the multilayer structure includes (1) using a resin composition for forming an A layer and a resin composition for forming a B layer, and having the A layer and the B layer by a multilayer coextrusion method. A method for producing a multilayer structure, and (2) using a resin composition for forming an A layer and a resin composition for forming a B layer, by laminating and stretching a plurality of laminates via an adhesive. Examples thereof include a method for producing a multilayer structure having an A layer and a B layer. Among these, from the viewpoint of high productivity and excellent interlayer adhesion, there is a method of molding by a multilayer coextrusion method using the resin composition for forming the A layer and the resin composition for forming the B layer of (1). preferable.

  In the multilayer coextrusion method, the resin composition for forming the A layer and the resin composition for forming the B layer are heated and melted, supplied from different extruders or pumps to the extrusion dies through the respective flow paths, and extruded. The multilayer structure is formed by laminating and bonding after being extruded into multiple layers from the die. As this extrusion die, for example, a multi-manifold die, a field block, a static mixer, or the like can be used.

  In the multilayer structure, the multilayer laminate obtained in this manner is irradiated with active energy rays as described above to promote the crosslinking reaction and further improve the interlayer adhesion between the A layer and the B layer. It is preferable to make it. Since the multilayer structure is thus irradiated with the active energy rays, the adhesion between the layers is enhanced, and as a result, the gas barrier property and the bending resistance can be improved.

  The active energy rays are those having energy quanta among electromagnetic waves or charged particle beams, specifically, ultraviolet rays, γ rays, electron beams and the like. Among these active energy rays, an electron beam is preferable from the viewpoint of improving the interlayer adhesion. By using an electron beam as the active energy ray, the interlayer cross-linking reaction is further promoted, and the interlayer adhesion of the multilayer structure can be further improved.

  When irradiating an electron beam, various electron beam accelerators such as a cockroft Walton type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, and a high frequency type are used as an electron beam source. It is preferable to irradiate within an irradiation dose range of 5 to 600 kGy with a normal acceleration voltage of 100 to 500 kV.

  Moreover, when using an ultraviolet-ray as an active energy ray, it is good to irradiate what contains the ultraviolet-ray with a wavelength of 190-380 nm. The ultraviolet light source is not particularly limited, and for example, a high pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, a carbon arc lamp, or the like is used.

  As described above, this multilayer structure has excellent interlayer adhesion, and has high gas barrier properties, stretchability, thermoformability, and durability.

  This multilayer structure is not limited to the above embodiment. For example, other layers may be included in addition to the A layer and the B layer. Although the kind of resin composition which comprises this other layer is not specifically limited, A thing with high adhesiveness between A layer and / or B layer is preferable. The other layer has a molecular chain having a functional group that reacts with a hydroxyl group possessed by, for example, EVOH in the A layer, or a carbamate group or an isocyanate group in the molecular chain of, for example, TPU in the B layer. Those that are particularly preferred.

<Adhesive layer>

The adhesive layer needs to contain a modified diene polymer having a glass transition temperature (Tg) of −30 ° C. or lower. If the glass transition temperature (Tg) is higher than −30 ° C., the brittle temperature of the adhesive layer cannot be lowered sufficiently, and cracks are likely to occur in the pneumatic tire in a low temperature environment. From this viewpoint, the glass transition temperature (Tg) of the modified diene polymer is preferably −40 ° C. or lower, more preferably −50 ° C. or lower, still more preferably −60 ° C., and particularly preferably − It is 70 degrees C or less.
The glass transition temperature (Tg) is a value measured by the following method. That is, using a differential scanning calorimeter (DSC) “RDC220” manufactured by Seiko Co., Ltd., the temperature is measured at 15 ° C./min after cooling to −150 ° C. Before and after the jump of the DSC curve, a tangent to the base line is drawn, and the temperature at the midpoint between the two tangents is read and defined as Tg.

The material of this adhesive layer is not particularly limited as long as it contains a modified diene polymer having a glass transition temperature of −30 ° C. or lower, but includes a diene polymer modified with a polar functional group (modified diene polymer). It is preferable. By this polar functional group, the adhesive force with the layer containing the thermosetting resin film is improved.
The polar functional group includes epoxy group, amino group, imino group, nitrile group, ammonium group, isocyanate group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, oxy Examples thereof include a carbonyl group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, a nitrogen-containing heterocyclic group, an oxygen-containing heterocyclic group, an alkoxysilyl group, and a tin-containing group, and an epoxy group is particularly preferable.
Moreover, as a material of this contact bonding layer, it is preferable that the softening agent mentioned later is included. By adjusting the content of the softening agent in the adhesive layer, the elastic modulus of the adhesive layer 7 can be adjusted.

≪Modified diene polymer≫
Examples of the modified diene polymer include modified natural rubber and / or modified synthetic rubber. Examples of the modified synthetic rubber include modified polybutadiene rubber (BR), modified polyisoprene rubber (IR), modified styrene-butadiene rubber (SBR), modified styrene-isopre rubber (SIR), modified styrene-butadiene-styrene copolymer (SBS), and the like. Can be mentioned. These modified natural rubber and modified synthetic rubber are excellent in durability in a low temperature environment.

  The adhesive layer preferably contains two or more modified diene polymers having different modification rates. Thereby, the adhesiveness with a carcass can be improved with a modified diene polymer having a low degree of modification, and the adhesiveness with a thermoplastic resin film can be improved with a modified diene polymer with a high modification rate.

  The content of the modified diene polymer in the rubber component of the adhesive layer is preferably 20 to 100% by mass. Within this range, the brittle temperature of the adhesive layer can be sufficiently reduced, and the crack resistance of the pneumatic tire in a low temperature environment is improved. In this respect, the content is more preferably 50 to 100% by mass, and still more preferably 70 to 100% by mass.

(Epoxidized butadiene rubber (EBR))
As the modified diene polymer, epoxidized butadiene rubber (hereinafter sometimes abbreviated as “EBR”) is more preferably used. The glass transition temperature (about −100 ° C.) of unmodified butadiene rubber (BR) is significantly lower than the glass transition temperature (about −50 ° C.) of natural rubber (NR). For this reason, by epoxidizing BR to EBR, even if the glass transition temperature (Tg) rises, Tg can still be maintained at a value sufficiently lower than −30 ° C.
The epoxidized butadiene rubber (EBR) is not particularly limited, and may be a commercially available epoxidized butadiene rubber or an epoxidized butadiene rubber (BR). The method for epoxidizing butadiene rubber is not particularly limited, and examples thereof include a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, and a peracid method. Examples of the peracid method include a method of reacting butadiene rubber with an organic peracid such as peracetic acid or performic acid. This reaction epoxidizes the double bonds present in the butadiene rubber molecule, and this structure is revealed from proton nuclear magnetic resonance spectra (NMR) and infrared absorption spectra (IR). In addition, the content of epoxy groups is measured from IR and elemental analysis. It should be noted that epoxidized butadiene rubbers having various epoxidation rates can be prepared by adjusting the amount of organic peracid and the reaction time.
This epoxidized butadiene rubber has less gas permeability than butadiene rubber, and gas permeability tends to be greatly reduced.

The epoxidation rate of EBR is preferably 5 mol% or more, more preferably 10 mol% or more, and further preferably 20 mol% or more. The adhesiveness with respect to a thermoplastic resin film is securable that an epoxidation rate is 5 mol% or more. The epoxidation rate is preferably 90 mol% or less, more preferably 75 mol% or less, and still more preferably 60 mol% or less. When the epoxidation rate is 90 mol% or less, the elastic modulus at −20 ° C. increases and the low temperature cracking property decreases.
Here, the epoxidation rate A mol% means that A% of double bonds in the butadiene rubber is epoxidized. The epoxidation rate means the mol% of the olefin unsaturation position originally present in the rubber converted to oxirane, and is sometimes referred to as “oxirane enzyme concentration”. For example, it can be measured by titrating with an acetic acid solution of hydrogen bromide using an automatic titrator (trade name: GT-200, manufactured by Mitsubishi Chemical Analytech), and so on.

  The EBR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B having a high cis content such as BR150B, VCR412, VCR617 manufactured by Ube Industries, etc. BR containing a syndiotactic polybutadiene crystal can be used.

  The epoxidized butadiene rubber (EBR) preferably contains at least two types of EBR having different epoxidation rates. This improves the adhesion between the resin film layer and the rubber-like elastic layer with the EBR having a low degree of epoxidation and the adhesion with the rubber-like elastic layer with the high epoxidation rate. Can be made.

  As the EBR having different epoxidation rates, a combination of at least two of (a) EBR having an epoxidation rate of 5 to 30 mol% and (b) EBR having an epoxidation rate of 40 to 90 mol% is preferable. It is preferable that content of the said EBR combination is 80-100 mass%. If the content of the EBR combination in the adhesive layer is in the range of 80 to 100% by mass, the compatibility of the components in the adhesive layer is improved, and the adhesive force and the durability of the adhesive layer are improved. From such a viewpoint, the content of the EBR combination is more preferably 90 to 100% by mass, and most preferably 100% by mass.

Further, by using EBR having an epoxidation rate of 5 to 30 mol% as an EBR having a low epoxidation rate, the property of butadiene rubber is maintained, and the dynamic storage elastic modulus E ′ of the adhesive layer 7 at −20 ° C. is increased. Can be suppressed, and the occurrence of cracks in a low temperature environment can be prevented. By using EBR having an epoxidation rate of 40 to 90 mol% as a butadiene rubber having a high epoxidation rate, it makes use of the properties of EBR and acts with a functional group in the thermoplastic resin film, thereby providing a gas barrier property of the resulting laminate. Can be improved.
In the present invention, the content ratio of the low epoxidation rate EBR and the high epoxidation rate EBR is 20:80 to 80:20 in terms of mass ratio from the viewpoint of the balance of the respective effects described above. It is preferable that it is the range of these.

  The EBR content in the rubber component of the adhesive layer is preferably 20 to 100% by mass. Within this range, the brittle temperature of the adhesive layer can be sufficiently reduced, and the crack resistance of the pneumatic tire in a low temperature environment is improved. In this respect, the content is more preferably 50 to 100% by mass, and still more preferably 70 to 100% by mass.

(Epoxidized natural rubber (ENR))
As the modified diene polymer, an epoxidized natural rubber (hereinafter sometimes abbreviated as “ENR”) may be used as long as it is Tg−30 ° C. or lower.
As the epoxidized natural rubber (ENR), commercially available epoxidized natural rubber may be used, or natural rubber may be epoxidized. The method for epoxidizing natural rubber is not particularly limited, and can be carried out using a method such as a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, or a peracid method. Examples of the peracid method include a method of reacting natural rubber with an organic peracid such as peracetic acid or performic acid. This reaction epoxidizes the double bond present in the natural rubber molecule, and this structure is revealed from proton nuclear magnetic resonance spectrum (NMR) and infrared absorption spectrum (IR). In addition, the content of epoxy groups is measured from IR and elemental analysis.
This epoxidized natural rubber has less gas permeability than natural rubber, and the gas permeability tends to be greatly reduced.

The epoxidized natural rubber (ENR) preferably contains at least two types of ENRs having different epoxidation rates. As a result, in the bonding of the resin film layer and the rubber-like elastic layer, the adhesion with the rubber-like elastic layer is improved with an ENR having a low degree of epoxidation, and the adhesion with the resin film layer is improved with an ENR having a high epoxidation rate. Can be made.
Here, the epoxidation rate A mol% means that A% of double bonds in natural rubber is epoxidized. The epoxidation rate means the mol% of the olefin unsaturation position originally present in the rubber converted to oxirane, and is sometimes referred to as “oxirane enzyme concentration”. For example, it can be measured by titrating with an acetic acid solution of hydrogen bromide using an automatic titrator (trade name: GT-200, manufactured by Mitsubishi Chemical Analytech), and so on.

  As ENRs having different epoxidation rates, (a) at least two combinations of ENRs having an epoxidation rate of 5 to 30 mol% and (b) ENRs having an epoxidation rate of 40 to 90 mol% are preferable. The content of the ENR combination is preferably 80 to 100% by mass. If the content of the ENR combination in the adhesive layer is in the range of 80 to 100% by mass, the compatibility of the components in the adhesive layer is improved, and the adhesive strength and the durability of the adhesive layer are improved. From such a viewpoint, the content of the ENR combination is more preferably 90 to 100% by mass, and most preferably 100% by mass.

Further, by using ENR having an epoxidation rate of 5 to 30 mol% as an ENR having a low epoxidation rate, the properties of natural rubber are maintained, and the dynamic storage elastic modulus E ′ of the adhesive layer 7 at −20 ° C. is increased. Can be suppressed, and the occurrence of cracks in a low temperature environment can be prevented. By using ENR having an epoxidation rate of 40 to 90 mol% as a natural rubber having a high epoxidation rate, it makes use of the properties of ENR to act on the functional groups in the thermoplastic resin film, and gas barrier properties of the resulting laminate Can be improved.
In the present invention, the content ratio of the low epoxidation rate ENR and the high epoxidation rate ENR is 20:80 to 80:20 in terms of mass ratio from the viewpoint of the balance of the respective effects described above. It is preferable that it is the range of these.
(High diene elastomer)
As the modified diene polymer, in addition to the ENR, the high diene elastomer can be contained in a proportion of preferably 20% by mass or less, more preferably 10% by mass or less, but most preferably not.
Examples of the high diene elastomer include natural rubber, synthetic isoprene rubber (IR), cis 1,4-polybutadiene rubber (BR), syndiotactic-1,2-polybutadiene rubber (1, BR), and styrene-butadiene rubber ( SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR) and the like.
These high diene elastomers may be used singly or in combination of two or more, among which natural rubber, synthetic isoprene rubber (IR) and cis 1,4-polybutadiene rubber (BR) is preferred.

≪Softening agent≫
As the softener, any of mineral oil softeners, vegetable oil softeners, and synthetic softeners can be used. Mineral oil softeners include petroleum softeners and coal tar softeners. Examples of petroleum softeners include process oil, extender oil, asphalt, paraffins, liquid paraffin, petroleum jelly, and petroleum resin. Examples of the coal tar softener include coal tar and coumarone indene resin.
As vegetable oil softeners, fatty oil softeners such as soybean oil, palm oil, pine oil, castor oil, linseed oil, rapeseed oil, coconut oil, tall oil, waxes such as factis, beeswax, carnauba wax, lanolin, Examples include fatty acids such as linoleic acid, palmitic acid, stearic acid, and lauric acid.
Synthetic softeners include synthetic resin softeners, liquid rubbers or oligomers, low molecular plasticizers, high molecular plasticizers, and reactive plasticizers.
Examples of the synthetic resin softener include phenol aldehyde resin, styrene resin, and atactic polypropylene. Examples of the liquid rubber or oligomer include polybutene, liquid butadiene rubber, liquid isoprene rubber, and liquid acrylonitrile butadiene rubber. Examples of the low molecular plasticizer include dibutyl phthalate, dioctyl phthalate, tricresyl phosphate, and the like.

  The content of the softening agent is preferably 1 to 30 parts by mass, more preferably 5 to 25 parts by mass, and still more preferably 10 to 20 parts by mass with respect to 100 parts by mass of all rubber components constituting the adhesive layer. Part. When the amount is 1 part by mass or more, the modification degree of the modified diene polymer can be sufficiently increased. It is prevented that a contact bonding layer is too soft as it is 30 mass parts or less. As the softening agent, one selected from the softening agents described above can be used, or a plurality of softening agents can be used in combination.

≪Vulcanizing agent, vulcanization accelerator≫
The adhesive layer can contain a vulcanizing agent, or a vulcanizing agent and a vulcanization accelerator in order to impart vulcanizability.
As said vulcanizing agent, sulfur etc. are mentioned, The usage-amount is 0.1-10 mass parts as a sulfur content with respect to 100 mass parts of all the rubber components, More preferably, it is 1.0-5 mass parts. It is.
The vulcanization accelerator that can be used in the present invention is not particularly limited. For example, M (2-mercaptobenzothiazole), DM (dibenzothiazolyl disulfide), CZ (N-cyclohexyl-2-benzothia). Zolylsulfenamide) and other guanidine vulcanization accelerators such as DPG (diphenylguanidine) can be used, and the amount used is 0.1 to 5 with respect to 100 parts by mass of the rubber component. A mass part is preferable, More preferably, it is 0.2-3 mass part.

≪Optional ingredient≫
In addition to the above components, the adhesive layer can contain a filler, a tackifier resin, stearic acid, zinc white, an anti-aging agent, and the like as necessary.
(Filler)
As the filler, an inorganic filler and / or carbon black is used. The inorganic filler is not particularly limited, and preferred examples include silica, aluminum hydroxide, aluminum oxide, magnesium oxide, montmorillonite, mica, smectite, organic montmorillonite, organic mica, and organic smectite by a wet method. . These may be used individually by 1 type, and may be used in combination of 2 or more types.
On the other hand, as carbon black, any of those conventionally used as reinforcing fillers for rubber can be appropriately selected and used, for example, FEF, SRF, HAF, ISAF, SAF, GPF, etc. Is mentioned.
The content of the filler is preferably 5 parts by mass or more of the inorganic filler together with carbon black from the viewpoint of tackiness and peeling resistance per 100 parts by mass of the modified diene polymer.

(Tackifying resin)
Examples of tackifying resins having a function of imparting tackiness to the adhesive layer include phenolic resins, terpene resins, modified terpene resins, hydrogenated terpene resins, rosin resins, C5, C9 petroleum resins, xylene resins, Coumarone-indene resin, dicyclopentadiene resin, styrene resin and the like can be mentioned. Among these, phenol resin, terpene resin, modified terpene resin, hydrogenated terpene resin and rosin resin are preferable.
Examples of the phenolic resin include a resin obtained by condensing pt-butylphenol and acetylene in the presence of a catalyst, and a condensate of alkylphenol and formaldehyde. Further, as terpene resins, modified terpene resins, and hydrogenated terpene resins, for example, terpene resins such as β-pinene resin and α-pinene resin, hydrogenated terpene resins obtained by hydrogenation of these, terpenes and the like Examples thereof include modified terpene resins obtained by reacting phenol with a Friedel-Craft type catalyst or condensing with formaldehyde. Examples of rosin resins include natural resin rosin and rosin derivatives modified by hydrogenation, disproportionation, dimerization, esterification, limeization, and the like.
These resins may be used alone or in combination of two or more. Among these resins, phenolic resins are particularly preferable.
This tackifying resin is preferably used in an amount of 5 parts by mass or more, more preferably 5 to 40 parts by mass, and still more preferably 5 to 30 parts by mass with respect to 100 parts by mass of the modified diene polymer.
In particular, when a phenolic resin is used as the tackifier resin and magnesium oxide is used as the inorganic filler, the obtained adhesive layer is preferable because it exhibits excellent tackiness.

The adhesive layer can be prepared by mixing the components described above using, for example, a Banbury mixer or a roll.
The adhesive layer of the present invention thus obtained is used for joining the thermoplastic resin film and the carcass.

≪Adhesive layer thickness≫
The thickness of the adhesive layer is preferably 5 to 200 μm. When it is 5 μm or more, the thermoplastic resin film and the carcass can be firmly bonded, and the function of improving crack resistance in a low-temperature environment is satisfactorily exhibited. When it is 200 μm or less, weight reduction of the pneumatic tire is achieved.

[Pneumatic tire manufacturing method]
There is no restriction | limiting in particular in the manufacturing method of the said pneumatic tire 10. FIG. For example, the inner liner having the thermoplastic film, the adhesive layer, and the carcass are wound around the peripheral surface of the tire molding drum in this order from the inside, and the belt layer 4 and the tread portion 5 are further formed thereon. After the rubber member, the rubber member constituting the sidewall portion 6 and the like are wound, the drum is pulled out to obtain a green tire. Next, the pneumatic tire 10 is obtained by heating and vulcanizing the green tire at a temperature of usually 120 ° C. or higher, preferably 125 to 200 ° C., more preferably 130 to 180 ° C.
As described above, as a method of winding the inner liner, the adhesive layer, and the carcass on the circumferential surface of the tire molding drum in this order from the inside, a method using a coating solution of the adhesive layer composition shown below And any of the methods using a sheet of an adhesive layer is preferably employed.

<Method of Using Coating Solution for Adhesive Layer Composition>
In this method, an adhesive coating solution obtained by dissolving the composition of the adhesive layer in a good solvent is used to form the outer surface of the inner liner 3 (the surface that becomes the outer side when wrapped around a molding drum) and the inner surface of the carcass 2 ( It is applied to at least one of the surfaces that become the inner side when wound around the forming drum. Next, the inner liner 3 and the carcass 2 are wound in this order on the peripheral surface of the molding drum, and further, a belt member 4, a rubber member constituting the tread portion 5, a rubber member constituting the sidewall portion 6 and the like are wound thereon. After stacking, the drum can be removed to make a green tire.
As the good solvent, an organic solvent having a Hilderand solubility parameter δ value in the range of 14 to 20 MPa ^1/2 which is a good solvent for the rubber component is preferably used. Examples of such an organic solvent include toluene, xylene, n-hexane, cyclohexane, chloroform, methyl ethyl ketone, and the like. These may be used individually by 1 type, and 2 or more types may be mixed and used for them.
The solid content concentration of the coating solution thus prepared is appropriately selected in consideration of coating properties and handling properties, but is usually in the range of 5 to 50% by mass, preferably 10 to 30% by mass. It is.

<Method using an adhesive layer sheet>
In this method, the inner liner, the adhesive layer sheet, and the carcass may be wound in this order on the peripheral surface of the tire forming drum. In addition, after the adhesive layer sheet is previously attached to at least one of the inner liner and the carcass, the inner liner and the carcass may be wound around the peripheral surface of the forming drum in this order.

[Other examples of pneumatic tire structures]
FIG. 3 is a partially enlarged sectional view showing another example of the pneumatic tire of the present invention. This pneumatic tire 10A is the same as the pneumatic tire 10 in FIGS. 1 and 2 except that the rubber layer 8 is disposed between the carcass 2 and the adhesive layer 7, and the same reference numerals denote the same parts. Show.

≪Rubber layer≫
Here, the rubber layer preferably uses a diene rubber as a rubber component. Specific examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), cis-1,4-polybutadiene rubber (BR), and syndiotactic-1,2-polybutadiene rubber (1, 2BR). Styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and the like. These diene rubbers may be used alone or in combination of two or more.

  For the rubber layer, in addition to the rubber component, compounding agents commonly used in the rubber industry, such as reinforcing fillers, softeners, anti-aging agents, vulcanizing agents, vulcanization accelerators for rubber, and scorch prevention An agent, zinc white, stearic acid and the like can be appropriately blended depending on the purpose. As these compounding agents, commercially available products can be suitably used.

  The thickness of the rubber layer is preferably 200 to 1000 μm, more preferably 200 to 600 μm, and even more preferably 200 to 400 μm. When the rubber layer thickness is 200 μm or more, the reinforcing effect Is sufficiently exerted, and when the thermoplastic resin film layer is ruptured / cracked, it becomes difficult for the crack to extend, and thus adverse effects such as a large rupture and crack can be suppressed. If it is 1000 μm or less, the weight of the tire can be reduced.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
The measurement method and evaluation method for each characteristic will be described first.

[Measurement method and evaluation method of each characteristic]
(1) Tg
Using a differential scanning calorimeter (DSC) “RDC220” manufactured by Seiko Co., Ltd., the temperature was measured at 15 ° C./min after cooling to −150 ° C. Before and after the jump of the DSC curve, a tangent to the base line was drawn, and the temperature at the midpoint between the two tangents was read and taken as Tg.

(2) Dynamic storage elastic modulus E ′ at −20 ° C.
For each sample (dimensions: dimensions: width 5 mm, length 40 mm), using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd., under conditions of initial strain 10%, dynamic strain 0.1%, frequency 15 Hz, -20 ° C, The dynamic storage modulus E ′ was measured.

(3) EBR epoxidation rate EBR was dissolved in deuterated chloroform and analyzed by nuclear magnetic resonance (NMR (JNM-ECA series manufactured by JEOL Ltd.)) spectroscopic analysis. The epoxidation rate was calculated from the ratio of the integral value h (ppm) of the family part using the following calculation formula.
(Epoxidation rate E%) = 3 × h (2.69) / (3 × h (2.69) + 3 × h (5.14) + h (0.87)) × 100

(4) Presence / absence of cracks after the drum running test The tire was run at 1,000 km by pressing it on a drum with a load of 6 kN on a drum with an air pressure of 140 kPa and a speed of 80 km / h in an atmosphere of −20 ° C. did. The appearance of the inner liner of the tire after running the drum was visually observed to evaluate the presence or absence of cracks.

(5) Gas barrier property of the tire after the drum running test The tire side surface is cut into a size of 10 cm × 10 cm, conditioned at 20 ° C.-65% RH for 5 days, and a sample of the section of the conditioned tire side surface is obtained. Using 2 sheets, using “MOCON OX-TRAN 2/20 type” manufactured by Modern Control Co., under the conditions of 20 ° C.-65% RH, the oxygen transmission rate is adjusted according to the method described in JIS-K7126 (isobaric method). The average value was measured (unit: mL / m ² · day · atm), and the average value of the oxygen transmission rate of the sample of the multilayer structure of Comparative Example 1 was displayed as an index to evaluate the gas barrier property. The lower the index value, the better the gas barrier property.

(6) Characteristics of ethylene-vinyl alcohol copolymer (EVOH) The ethylene content and saponification degree of EVOH were measured by ¹ H-NMR measurement using deuterated dimethyl sulfoxide as a solvent [“JNM-GX-” manufactured by JEOL Ltd. The value calculated from the spectrum obtained in [Use 500 type] was used.
Further, the melt flow rate (MFR) of EVOH was measured by filling a sample 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.], melting at 190 ° C., and weighing 2160 g. The load was evenly applied using a plunger with a diameter of 9.48 mm, and the amount was calculated from the amount of resin (g / 10 minutes) extruded per unit time from an orifice with a diameter of 2.1 mm provided at the center of the cylinder. However, when the melting point of EVOH is around 190 ° C or exceeds 190 ° C, it is measured at a plurality of temperatures above the melting point under a load of 2160g, and the inverse of absolute temperature is plotted on the horizontal axis and the logarithm of MFR is plotted on the vertical axis in a semilogarithmic graph The value calculated by plotting and extrapolating to 190 ° C. was taken as the melt flow rate (MFR).

[Production Example 1] Production of inner liner (5-layer film) EVOH [Kuraray Co., Ltd. “E105”] and thermoplastic polyurethane (TPU) [Kuraray Co., Ltd. “Kuramylon 3190”] were used. A film layer (TPU layer / EVOH layer / TPU layer / EVOH layer / TPU layer) having a five-layer structure was produced using the seed five-layer coextrusion apparatus under the following coextrusion molding conditions. The thickness of each layer is 2 μm / 20 μm / 2 μm / 20 μm / 10 μm, respectively.

Extrusion temperature of each resin: C1 / C2 / C3 / die = 170/170/170/220/220/220 ° C.
Extruder specifications for each resin:
TPU: 25mmφ Extruder “P25-18AC” [Osaka Seiki Machine Co., Ltd.]
EVOH: 20 mmφ Extruder Lab Machine ME Type “CO-EXT” [Toyo Seiki Co., Ltd.]
T-die specification: 500mm width, 2 types, 5 layers [Plastic Engineering Laboratory Co., Ltd.]
Cooling roll temperature: 50 ° C
Take-off speed: 4 m / min The gas barrier property of this inner liner was measured by the above measuring method. The results are shown in Table 1.

[Production Example 2] Production of inner liner (21-layer film) EVOH ["E105" manufactured by Kuraray Co., Ltd.] and thermoplastic polyurethane (TPU) ["Kuramylon 3190" manufactured by Kuraray Co., Ltd.] Using a seed 21-layer multilayer coextrusion apparatus, a 21-layer film layer (TPU layer / EVOH layer... EVOH layer / TPU layer. TPU layer: 11 layers, EVOH layer: 10 layers) was produced under the following coextrusion molding conditions. did. The thickness of each layer is 2 μm for the TPU layer and 1 μm for the modified EVOH layer.

A multilayer film of 21 layers was extruded at a feed block temperature of 210 ° C. and a die of 208 ° C. for a multilayer.
Extruder specifications for each resin:
Thermoplastic polyurethane: 25mmφ extruder “P25-18AC” [manufactured by Osaka Seiki Co., Ltd.]
EVOH: 20 mmφ Extruder Lab Machine ME Type “CO-EXT” [Toyo Seiki Co., Ltd.]
T-die specification: 500mm width 2 types 21 layers [Plastic Engineering Laboratory Co., Ltd.]
Cooling roll temperature: 50 ° C
Take-off speed: 4 m / min For this inner liner, the gas barrier product was measured by the measurement method described above. The results are shown in Table 1.

[Production Example 3] Production of Epoxidized Butadiene Rubber (EBR (1)) 100 g of BR-150B (Hisys BR manufactured by Ube Industries Co., Ltd.) is finely cut so that one grain is about 0.5 g. The solution was added to 1200 ml of toluene in a 5 L container and dissolved with stirring for 24 hours. Next, 2 ml of formic acid was added and the temperature was raised to 50 ° C. on a water bath. While stirring the solution, 5 g of hydrogen peroxide solution having a concentration of 30% by mass was dropped over 30 minutes. After completion of dropping, stirring was continued while maintaining 50 ° C., and after 3 hours, 0.3 g of BHT (dibutylhydroxytoluene) was added. After cooling to room temperature, the reaction solution was added to 5 L of methanol to precipitate the rubber component. The precipitate was spread on a wide vat and air-dried for 24 hours, followed by vacuum drying to obtain 99 g of EBR (1). As a result of calculating the epoxidation rate of this EBR (1) by the said method, it was 2.1 mol%.

[Production Example 4] Production of Epoxidized Butadiene Rubber (EBR (2)) 100 g of BR-150B (Hisys BR manufactured by Ube Industries Co., Ltd.) is finely cut so that one grain is about 0.5 g. The solution was added to 1200 ml of toluene in a 5 L container and dissolved with stirring for 24 hours. Next, 6 ml of formic acid was added and the temperature was raised to 50 ° C. on a water bath. While stirring the solution, 25 g of a hydrogen peroxide solution having a concentration of 30% by mass was added dropwise over 30 minutes. After completion of dropping, stirring was continued while maintaining 50 ° C., and after 3 hours, 0.3 g of BHT was added. After cooling to room temperature, the reaction solution was added to 5 L of methanol to precipitate the rubber component. The precipitate was spread on a wide vat and air-dried for 24 hours, followed by vacuum drying to obtain 99 g of EBR (2). As a result of calculating the epoxidation rate of this EBR (2) by the said method, it was 9.9 mol%.

[Production Example 5] Production of Epoxidized Butadiene Rubber (EBR (3)) 100 g of BR-150B (Hisys BR manufactured by Ube Industries Co., Ltd.) is finely cut so that one grain is about 0.5 g. The solution was added to 1200 ml of toluene in a 5 L container and dissolved with stirring for 24 hours. Next, 12 ml of formic acid was added and the temperature was raised to 50 ° C. on a water bath. While stirring the solution, 50 g of 30% by mass hydrogen peroxide was added dropwise over 30 minutes. After completion of dropping, stirring was continued while maintaining 50 ° C., and after 3 hours, 0.3 g of BHT was added. After cooling to room temperature, the reaction solution was added to 5 L of methanol to precipitate the rubber component. The precipitate was spread on a wide vat and air-dried for 24 hours, followed by vacuum drying to obtain 99 g of EBR (3). As a result of calculating the epoxidation rate of this EBR (3) by the above method, it was 20.7 mol%.

[Examples 1-4 and Comparative Examples 1-2]
(1) Preparation of coating solution for adhesive layer After kneading each component of the types and amounts shown in Table 1 according to a conventional method, 1000 parts by mass of toluene (δ value: 18.2 MPa ^1/2 ) as an organic solvent In addition, an adhesive layer coating solution was prepared by dissolving or dispersing.
Incidentally, the dynamic storage modulus E ₂ 'at -20 ° C. for the adhesive layer using the adhesive layer coating solution was measured by the following procedure. That is, a part of this adhesive coating solution was applied on a release sheet (material: release-processed PET film, manufactured by Fujimori Chemical Industry Co., Ltd., trade name: NSD) and dried at 80 ° C. for 2 minutes. And vulcanized by heating at 160 ° C. for 20 minutes to obtain a sample having a thickness of 30 μm. For this sample, by the above measuring method, to measure the Tg and dynamic storage elastic modulus E ₂ 'at -20 ° C.. The results are shown in Table 1.

(2) Preparation of tire The inner liner (5-layer film) was wound on a tire molding drum. The adhesive layer coating solution was applied to the surface of the carcass, and the coated surface was wound around the inner liner so that the coated surface faced the inner liner. Further, a belt layer, a tread rubber member, and a sidewall rubber member were sequentially wound, and then the drum was pulled out to obtain a green tire.
This green tire was heated and vulcanized to produce a pneumatic tire (195 / 65R15) as shown in FIGS.
About the obtained tire, the presence or absence of the crack after a drum running test and the gas barrier property of the tire after a drum running test were measured with the said measuring method. The results are shown in Table 1.

[Example 5]
The operation was carried out in the same manner as in Example 1 except that the inner liner (21 layer film) was used instead of the inner liner (5 layer film), and that the one in Table 1 was used as the coating liquid for the adhesive layer. went. The results are shown in Table 1.

Various chemicals in Table 1 are as follows.
NR: TSR20
BR: BR150B manufactured by Ube Industries, Ltd. (number average molecular weight (Mn) = 19000, weight average molecular weight (Mw) = 440000, molecular weight distribution (Mw / Mn) = 2.3, cis content = 98% by mass, glass transition Temperature = -105 ° C)
EBR (1) to (3): produced in the above production example ENR50: epoxidized natural rubber (trade name: ENR50, manufactured by RRIM) (epoxidation degree (epoxidation rate): 50 mol%)
ENR60: Epoxidized natural rubber (trade name: ENR-60, manufactured by MUANG MAI GUTHURIE) (Degree of epoxidation (epoxidation rate): 60 mol%)
Carbon black: Show Black N220 (N2SA: 125 m2 / g) manufactured by Cabot Japan
Anti-aging agent: NOCRACK 6C (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Stearic acid: Stearic acid oil manufactured by NOF Corporation: Process oil PW-380 manufactured by Idemitsu Kosan Co., Ltd.
Zinc oxide: Zinc Hana No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. (1): Noxeller CZ (N-t manufactured by Ouchi Shinsei Chemical Co., Ltd.) -Butyl-2-benzothiazolylsulfenamide)

[result]
The tires of Examples 1 to 5 manufactured using the adhesive layer having a Tg of −30 ° C. or less were free from cracks and excellent in gas barrier properties after the drum running test.
In contrast, the tires of Comparative Examples 1 and 2 manufactured using an adhesive layer having a Tg higher than −30 ° C. were cracked and inferior in gas barrier properties after the drum running test.
[Explanation of symbols]

1 Beat core 2 Carcass 3 Inner liner 4 Belt part 5 Tread part 6 Side wall part 7 Adhesive layer 8 Rubber layer

Claims (5)

A pneumatic tire having an inner liner having a thermoplastic resin film, a carcass, and an adhesive layer between the inner liner and the carcass,
The adhesive layer contains a modified diene polymer having a glass transition temperature of −30 ° C. or lower,
The glass transition temperature of -30 ° C. or less of the modified diene polymer is comprised of two or more epoxidized polybutadiene rubbers having different modification ratio,
The inner liner has a laminated structure of a thermoplastic resin film and a layer made of a resin composition containing an elastomer,
The pneumatic tire which the layer which consists of a resin composition containing the said elastomer adhere | attaches with the said contact bonding layer among the said inner liners.   The pneumatic tire according to claim 1, wherein the epoxidized polybutadiene rubber has a modification rate of 5 to 90 mol%.   The pneumatic tire according to claim 1 or 2, wherein a content of the epoxidized polybutadiene rubber in a rubber component of the adhesive layer is 20 to 100% by mass. The pneumatic tire according to any one of claims 1 to 3 , wherein the inner liner is a multilayer film having three or more layers. The pneumatic tire according to claim 4 , wherein the inner liner is a multilayer film having seven or more layers.

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