JP4468073B2 - Emergency pneumatic tires - Google Patents

Description

  The present invention relates to an emergency pneumatic tire, and relates to an emergency pneumatic tire having a high working internal pressure and called a T type in standards such as JATMA, ETRTO, and TRA.

 Emergency pneumatic tires are characterized by high filling air pressure and low internal pressure compared to ordinary pneumatic tires, and it is difficult to check the air pressure because they are stored in a trunk for a long period of time. Therefore, the demand for maintaining the air pressure is higher than that of a general tire.

 Conventionally, butyl rubber, halogenated butyl rubber, or the like has been used as the main raw material for the inner liner as a gas barrier layer in order to maintain the internal pressure of the tire. However, in the rubber composition containing these, the gas barrier property is low, so that the thickness of the inner liner is 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 consumption of the automobile.

 On the other hand, an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as “EVOH”) is known to have excellent gas barrier properties. EVOH has an air permeation amount that is 1/100 or less of that of a butyl-based inner liner rubber composition. Therefore, even when the thickness is 50 μm or less, internal pressure retention can be greatly improved, and the weight of the tire can be reduced. (For example, refer to Patent Document 1).

An emergency pneumatic tire is also disclosed in which a thin film is laminated on the inner surface of an emergency pneumatic tire (see, for example, Patent Document 2).
JP-A-6-40207 JP-A-4-212602

 However, in recent years, as compared with a tire inner liner made of conventional EVOH, an inner liner having a higher degree of bending resistance while maintaining a gas barrier property has been demanded. It is desired.

  In view of the above problems, an object of the present invention is to provide a light-weight emergency pneumatic tire that greatly improves gas barrier properties and improves air pressure retention.

 A feature of the present invention is an emergency pneumatic tire that is used in place of a standard tire mounted on an automobile, has an extremely narrow tire width compared to the standard tire, has substantially the same tire outer diameter, and has a high use internal pressure. A modified ethylene-vinyl alcohol obtained by reacting 1 to 50 parts by weight of an epoxy compound (B) with 100 parts by weight of an ethylene-vinyl alcohol copolymer (A) having an ethylene content of 25 to 50 mol% It is an emergency pneumatic tire provided with the inner liner containing the layer which consists of a copolymer (C).

 According to the emergency pneumatic tire according to the features of the present invention, the gas barrier property can be greatly improved, and the weight can be reduced while the air pressure retention property is improved.

 The saponification degree of the ethylene-vinyl alcohol copolymer (A) is preferably 90% or more. If the saponification degree is less than 90%, the gas barrier property and the thermal stability at the time of molding the inner liner for a pneumatic tire may be insufficient.

 The epoxy compound (B) is preferably glycidol or epoxypropane. In the case of an epoxy compound having a valence of 2 or more, a crosslinking reaction with the ethylene-vinyl alcohol copolymer (A) occurs, and the quality of the inner liner for a pneumatic tire may be deteriorated due to the generation of gels, bumps and the like. From the viewpoint of ease of production of the modified ethylene-vinyl alcohol copolymer (C), gas barrier properties, flex resistance, and fatigue resistance, glycidol and epoxy propane, which are monovalent epoxy compounds, are preferable.

Further, the oxygen permeation amount at 20 ° C. and 65 RH% of the layer made of the modified ethylene-vinyl alcohol copolymer (C) is 3.0 × 10 ⁻¹² cm ³ · cm ² · sec · cmHg or less. Is preferred. From the viewpoint of gas barrier properties, this amount of oxygen permeation is preferable.

 The modified ethylene-vinyl alcohol copolymer (C) is preferably crosslinked. When the modified ethylene-vinyl alcohol copolymer (C) is not cross-linked, the layer made of the modified ethylene-vinyl alcohol copolymer (C) is significantly deformed in the vulcanization process for producing the pneumatic tire, A uniform amount cannot be maintained, and the gas barrier property, flex resistance, and fatigue resistance of the inner liner may be deteriorated.

 Further, the thickness of the layer made of the modified ethylene-vinyl alcohol copolymer (C) is preferably 50 μm or less. When it exceeds 50 μm, the merit of weight reduction becomes smaller than the inner liner using butyl rubber, halogenated butyl rubber or the like currently used.

 The inner liner preferably further includes an auxiliary layer made of an elastomer adjacent to the layer made of the modified ethylene-vinyl alcohol copolymer (C). Even if a layer made of the modified ethylene-vinyl alcohol copolymer (C) is provided, pinholes, cracks and the like may be formed. In such a case, between the film layer and the ply layer located outside the film layer, By arranging the auxiliary layer, the growth of cracks can be suppressed. Even if cracks occur, the layer made of the modified ethylene-vinyl alcohol copolymer (C) is firmly adhered to the surface of the auxiliary layer, so the surface is almost covered with a film, Air leakage can be suppressed.

 In addition, the layer made of the modified ethylene-vinyl alcohol copolymer (C) and the auxiliary layer are preferably bonded via at least one adhesive layer. Since the ethylene-vinyl alcohol copolymer has an —OH group, it is relatively easy to ensure adhesion with the rubber. For example, if a chlorinated rubber / isocyanate adhesive is used for the adhesive layer, adhesion to the rubber composition used in the tire can be ensured.

The oxygen permeation amount of the auxiliary layer at 20 ° C. and 65 RH% is preferably 3.0 × 10 ⁻⁹ cm ³ · cm ² · sec · cmHg or less. From the viewpoint of gas barrier properties, this amount of oxygen permeation is preferable.

 Further, butyl rubber or halogenated butyl rubber may be used for the auxiliary layer. By using such an elastomer having low air permeability, air leakage from the crack portion can be suppressed.

 A diene elastomer may be used for the auxiliary layer. From the viewpoint of gas barrier properties, by using such an elastomer, it is possible to keep the internal pressure retention of the pneumatic tire after running high even when a minute crack occurs.

 A thermoplastic urethane elastomer may be used for the auxiliary layer. By using such an elastomer, it is possible to realize a thin film and to suppress generation of cracks and extension.

 Further, when a plurality of auxiliary layers are laminated, it is preferable that the plurality of auxiliary layers are bonded together via at least one adhesive layer. Thus, the auxiliary layer which consists of a different kind of elastomer is producible by bonding a some auxiliary | assistant layer together.

  Moreover, it is preferable that the sum total of the thickness of an auxiliary | assistant layer is 50-1500 micrometers. When the thickness of the auxiliary layer is less than 50 μm, the bending resistance and fatigue resistance of the inner liner are reduced, and bending and deformation at the time of rolling of the tire are likely to cause breakage and cracking, and the crack is likely to extend. In addition, the internal pressure retention after use of the tire may be greatly reduced as compared to before use.

  According to the present invention, it is possible to provide an emergency pneumatic tire that is significantly lighter while significantly improving gas barrier properties and improving air pressure retention.

 Next, the present invention will be described in detail.

(Emergency pneumatic tire)
First, an embodiment of an emergency pneumatic tire according to the present invention will be described with reference to the drawings.

 Emergency pneumatic tires are pneumatic tires that are used in place of standard tires for automobiles, are extremely narrow in width compared to standard tires, have substantially the same tire outer diameter, and have high internal pressure. is there. It is called T type in standards such as JATMA, ETRTO, and TRA.

As shown in FIG. 1, an emergency pneumatic tire 100 according to this embodiment includes a pair of bead cores 12 and a bias structure emergency tire including a carcass 14 straddling the pair of bead cores 12 in a toroidal shape. It is.
A layer 41 made of a modified ethylene-vinyl alcohol copolymer (C) and an auxiliary layer 42 are sequentially arranged on the inner peripheral surface side of the carcass 14, and the tread rubber 22 constituting the tread portion 20 is disposed on the outer peripheral surface side. The side rubber 28 which comprises the side part 26 over the bead part 24 is arrange | positioned at the both sides | surfaces.
The carcass 14 includes a single carcass ply 30. The carcass ply 30 has the bead core 12 folded back from the inside of the tire to the outside, and the folded portion 30A is disposed along the main body 30B and extends outward in the tire radial direction. It is arranged in a range exceeding 20A and not exceeding the other tread end portion 20A.
The carcass ply 30 has a known structure in which a large number of ply cords arranged in parallel to each other are rubber-coated.
In addition, the carcass 14 is overlapped at both ends in the width direction in the tread portion 20. This overlap amount (OL in FIG. 1) is in the range of 40 to 90% of the tread width (TW in FIG. 1).

Further, the belt layer 6 is disposed between the carcass 14 and the tread rubber 22. The layer 41 made of the modified ethylene-vinyl alcohol copolymer (C) is made of ethylene having an ethylene content of 25 to 50 mol%. -It consists of a modified ethylene-vinyl alcohol copolymer (C) obtained by making 1-50 weight part of epoxy compounds (B) react with 100 weight part of vinyl alcohol copolymer (A).

 According to the emergency pneumatic tire 100 according to the present embodiment, by providing the inner liner layer made of the modified ethylene-vinyl alcohol copolymer (C), the gas barrier property is greatly improved, and the air pressure retention property is enhanced. The weight can be reduced.

 The auxiliary layer 42 is made of an elastomer. Regarding the thickness of the auxiliary layer 42, in the region from the end of the belt layer 6 to the beat portion 24, the thickness of the portion corresponding to the radial width of at least 30 mm is less than the portion corresponding to the lower portion of the belt layer 6 by 0. It is preferable that the thickness is 2 mm or more.

 In the pneumatic tire, breakage, cracks, and generation of cracks are mainly side portions 26 that are largely deformed by bending. Therefore, by increasing the thickness of the auxiliary layer 42 only on the side portion 26, it is possible to achieve both internal pressure retention after traveling and reduction in tire weight.

(Inner liner for pneumatic tires for emergency use)
Next, the layer made of the above-described modified ethylene-vinyl alcohol copolymer (C) and the auxiliary layer (D) will be described in detail.

 The inner liner for a pneumatic tire of the present invention includes a layer made of a modified ethylene-vinyl alcohol copolymer (C) obtained by reacting an epoxy compound (B) with an ethylene-vinyl alcohol copolymer (A). By the modification using the epoxy compound (B) in the present invention, the elastic modulus of the ethylene-vinyl alcohol copolymer can be greatly reduced, and the breakability at the time of bending and the degree of cracking can be improved.

 As ethylene-vinyl alcohol copolymer (A) used for this invention, ethylene content needs to be 25-50 mol%. From the viewpoint of obtaining good bending resistance and fatigue resistance, the lower limit of the ethylene content is more preferably 30 mol% or more, and even more preferably 35 mol% or more. From the viewpoint of gas barrier properties, the upper limit of the ethylene content is more preferably 48 mol% or less, and even more preferably 45 mol% or less. When the ethylene content is less than 25 mol%, flex resistance and fatigue resistance may be deteriorated, and melt moldability may be deteriorated. Moreover, when it exceeds 50 mol%, there exists a possibility that gas barrier property may be insufficient.

 Furthermore, the saponification degree of the ethylene-vinyl alcohol copolymer (A) used in the present embodiment is preferably 90% or more. The saponification degree is more preferably 95% or more, still more preferably 98% or more, and optimally 99% or more. If the saponification degree is less than 90%, the gas barrier property and the thermal stability at the time of molding the inner liner for a pneumatic tire may be insufficient.

 The preferred melt flow rate (MFR) (under 190 ° C. and 2160 g load) of the ethylene-vinyl alcohol copolymer (A) used in the present invention is 0.1 to 30 g / 10 min, more preferably 0. 3 to 25 g / 10 min. However, when the melting point of the ethylene-vinyl alcohol copolymer (A) 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, and the horizontal axis indicates the reciprocal absolute temperature in a semi-logarithmic graph. The logarithm of MFR is plotted on the vertical axis and expressed as a value extrapolated to 190 ° C.

 The tire inner liner of the present invention is a modified ethylene-vinyl alcohol copolymer obtained by reacting 1 to 50 parts by weight of an epoxy compound (B) with 100 parts by weight of an ethylene-vinyl alcohol copolymer (A). (C). More preferably, the mixing ratio of (A) and (B) is 2 to 40 parts by weight of (B) with respect to 100 parts by weight of (A), and more preferably with respect to 100 parts by weight of (A). (B) 5 to 35 parts by weight.

 The method for producing the modified ethylene-vinyl alcohol copolymer (C) by reacting the ethylene-vinyl alcohol copolymer (A) with the epoxy compound (B) is not particularly limited, but the ethylene-vinyl alcohol copolymer ( A suitable method is a production method in which A) and the epoxy compound (B) are reacted in a solution.

 In the production method by solution reaction, a modified ethylene-vinyl alcohol copolymer (C) is produced by reacting an epoxy compound (B) with a solution of the ethylene-vinyl alcohol copolymer (A) in the presence of an acid catalyst or an alkali catalyst. Is obtained. The reaction solvent is preferably a polar aprotic solvent that is a good solvent for the ethylene-vinyl alcohol copolymer (A) such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. Examples of reaction catalysts include acid catalysts such as p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid and boron trifluoride, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium methoxide, etc. An alkali catalyst is mentioned. Of these, it is preferable to use an acid catalyst. As a catalyst amount, about 0.0001-10 weight part is suitable with respect to 100 weight part of ethylene-vinyl alcohol copolymers (A). The modified ethylene-vinyl alcohol copolymer (C) can also be produced by dissolving the ethylene-vinyl alcohol copolymer (A) and the epoxy compound (B) in a reaction solvent and performing a heat treatment. .

 The epoxy compound (B) used in the present invention is not particularly limited, but is preferably a monovalent epoxy compound. In the case of an epoxy compound having a valence of 2 or more, a crosslinking reaction with the ethylene-vinyl alcohol copolymer (A) occurs, and the quality of the inner liner for a pneumatic tire may be deteriorated due to the generation of gels, bumps and the like. From the viewpoint of ease of production of the modified ethylene-vinyl alcohol copolymer (C), gas barrier properties, flex resistance, and fatigue resistance, preferred monovalent epoxy compounds include glycidol and epoxypropane.

 The melt flow rate (MFR) (190 ° C., under a load of 2160 g) of the modified ethylene-vinyl alcohol copolymer (C) used in the present invention is not particularly limited, but has good gas barrier properties, flex resistance and fatigue resistance. From the viewpoint of obtaining the above, it is preferably 0.1 to 30 g / 10 minutes, more preferably 0.3 to 25 g / 10 minutes, and further preferably 0.5 to 20 g / 10 minutes. However, when the melting point of the ethylene-vinyl alcohol copolymer (A) 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, and the horizontal axis indicates the reciprocal absolute temperature in a semi-logarithmic graph. The logarithm of MFR is plotted on the vertical axis and expressed as a value extrapolated to 190 ° C.

The layer made of the modified ethylene-vinyl alcohol copolymer (C) in the inner liner for a pneumatic tire of the present invention has an oxygen transmission rate of 3.0 × 10 ⁻¹² cm ³ · cm / cm ^{2 at} 20 ° C. and 65 RH%. It is preferably not more than sec · cmHg, more preferably not more than 1.0 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg, and 5.0 × 10 ⁻¹³ cm ³ · cm / cm More preferably, it is ² · sec · cmHg or less. From the viewpoint of gas barrier properties, this amount of oxygen permeation is preferable.

 The modified ethylene-vinyl alcohol copolymer (C) used in the present invention is formed into a film, sheet or the like by melt molding in order to be used as an inner liner for a pneumatic tire. Examples of melt molding methods for films, sheets and the like include extrusion molding methods. The method of extrusion molding is not particularly limited, and examples thereof include a T-die method and an inflation method. The melting temperature varies depending on the melting point of the copolymer, but is preferably about 150 to 270 ° C.

 In the inner liner for a pneumatic tire of the present invention, the layer of the modified ethylene-vinyl alcohol copolymer (C) made of the modified ethylene-vinyl alcohol copolymer (C) is preferably crosslinked. When the modified ethylene-vinyl alcohol copolymer (C) is not cross-linked, the layer made of the modified ethylene-vinyl alcohol copolymer (C) is significantly deformed in the vulcanization process for producing the pneumatic tire, A uniform amount cannot be maintained, and the gas barrier property, flex resistance, and fatigue resistance of the inner liner may be deteriorated.

 The method for forming a crosslinked structure in the modified ethylene-vinyl alcohol copolymer (C) is not particularly limited, but a preferable method is a method of irradiating energy rays. Examples of the energy rays include ionizing radiation such as ultraviolet rays, electron beams, X-rays, α rays, and γ rays, and electron beams are preferable.

 With respect to the electron beam irradiation method, a method of introducing a molded body into an electron beam irradiation apparatus after film or sheet processing by extrusion molding and irradiating the electron beam can be mentioned. Although it does not specifically limit regarding the dose of an electron beam, Preferably it is the range of 10-50 Mrad. When the electron dose to irradiate is lower than 10 Mrad, it becomes difficult to crosslink. On the other hand, when it exceeds 60 Mrad, the deterioration of the molded body easily proceeds. More preferably, the electron dose range is 20-50 Mrad.

 The inner liner for a pneumatic tire according to the present invention is a multilayer structure including at least one layer made of a modified ethylene-vinyl alcohol copolymer (C), in addition to being used as a single-layer molded product for a pneumatic tire. Can be used for pneumatic tires.

 The inner liner for tire of the present invention preferably includes an auxiliary layer (D) made of an elastomer adjacent to the layer made of the modified ethylene-vinyl alcohol copolymer (C). By providing the auxiliary layer (D), the gas barrier property can be further improved and the air pressure retention property can be enhanced.

 In the inner liner for a pneumatic tire of the present invention, the layer made of the modified ethylene-vinyl alcohol copolymer (C) may be bonded to the auxiliary layer (D) through at least one adhesive layer. it can.

 Since the ethylene-vinyl alcohol copolymer has an —OH group, it is relatively easy to ensure adhesion with the rubber. For example, if a chlorinated rubber / isocyanate adhesive is used for the adhesive layer, adhesion to the rubber composition used in the tire can be ensured.

 As the layer structure of the multilayer structure, the layer made of the modified ethylene-vinyl alcohol copolymer (C) of the present invention is represented by C, the auxiliary layer (D) made of elastomer is represented by D1, D2, and the adhesive layer is represented by Ad. C / D1, D1 / C / D1, C / Ad / D1, D1 / Ad / C / Ad / D1, D1 / C / D1 / D2, D1 / C / D1 / Ad / D2, etc. It is not limited to this. D1 and D2 denote auxiliary layers made of different elastomers. Each layer may be a single layer or may be a multilayer according to circumstances. Further, the modified ethylene-vinyl alcohol copolymer (C), the elastomer and the adhesive layer used may be of one type, or may be many types depending on the case.

 The method for producing the multilayer structure shown above is not particularly limited. For example, a method of melt-extruding an elastomer and an adhesive layer into a molded product (film, sheet, etc.) made of a modified ethylene-vinyl alcohol copolymer (C), and conversely, a modified ethylene-vinyl alcohol copolymer ( C) and a method of melt-extruding the adhesive layer, a method of co-extrusion of the modified ethylene-vinyl alcohol copolymer (C) and the auxiliary layer (D) (and an adhesive layer as required), a modified ethylene-vinyl alcohol From the modified ethylene-vinyl alcohol copolymer (C), a method of laminating the product obtained from the copolymer (C) with an elastomer film or sheet using an adhesive layer, and further on a drum during tire molding Examples include a method of bonding the obtained molded product and the auxiliary layer (D) (and an adhesive layer as necessary).

 In the inner liner for a pneumatic tire of the present invention, the layer made of the modified ethylene-vinyl alcohol copolymer (C) preferably has a thickness of 50 μm or less. When it exceeds 50 μm, the merit of weight reduction becomes smaller than the inner liner using butyl rubber, halogenated butyl rubber or the like currently used. Furthermore, the bending resistance and fatigue resistance of the layer made of the modified ethylene-vinyl alcohol copolymer (C) are lowered, and the bending deformation at the time of rolling of the tire tends to cause breakage and cracking, and the crack is easy to extend. Therefore, the internal pressure retention of the tired foster mother may be lower than before use. On the other hand, it is preferable that it is 0.1 micrometer or more from a viewpoint of the gas barrier property of the inner liner for pneumatic tires. In light of gas barrier properties, flex resistance, and fatigue resistance, the thickness of the layer made of the modified ethylene-vinyl alcohol copolymer (C) is more preferably 1 to 40 μm, and even more preferably 5 to 30 μm.

 As described above, in the layer made of the modified ethylene-vinyl alcohol copolymer (C), the use at 50 μm or less improves the bending resistance and fatigue resistance, and breaks and cracks due to bending deformation during rolling of the tire. Is less likely to occur. Even if it breaks, the adhesiveness between the layer made of the modified ethylene-vinyl alcohol copolymer (C) and the auxiliary layer (D) made of an elastomer is good, so that it is difficult to peel off and cracks are difficult to extend. For this reason, it is hard to produce a big fracture | rupture and a crack. In addition, even if it occurs, the auxiliary layer (D) compensates for the gas barrier property of the fracture and crack portion generated in the modified ethylene-vinyl alcohol copolymer (C), so that the internal pressure can be maintained even after use of the tire. Become.

 That is, even a layer made of a modified ethylene-vinyl alcohol copolymer (C) having a thickness of 50 μm or less may cause pinholes and cracks. By arranging the auxiliary layer (D) made of an elastomer between the ply layers to be cracked, the growth of cracks can be suppressed. Even if cracks occur, the layer made of the modified ethylene-vinyl alcohol copolymer (C) is firmly adhered to the surface of the auxiliary layer (D), so the surface is almost covered with a film. By using an elastomer (butyl rubber, halogenated butyl rubber) having low air permeability for the layer (D), leakage of air from the crack portion can be suppressed.

The auxiliary layer (D) made of the elastomer of the inner liner for a pneumatic tire of the present invention has an oxygen transmission rate of 3.0 × 10 ⁻⁹ cm ³ · cm / cm ² · sec · cmHg or less at 20 ° C. and 65 RH%. It is preferable from the viewpoint of gas barrier properties of the inner liner. More preferably, it is 1.0 × 10 ⁻⁹ cm ³ · cm / cm ² · sec · cmHg or less.

 Preferred examples of the elastomer laminated as the auxiliary layer (D) of the inner liner for a pneumatic tire of the present invention include butyl rubber and diene elastomer. Preferred examples of the diene elastomer include natural rubber and butadiene rubber. From the viewpoint of gas barrier properties, butyl rubber is preferably used as the elastomer, and halogenated butyl rubber is more preferably used. Further, from the viewpoint of suppressing the extension of cracks after the occurrence of cracks in the auxiliary layer (D) made of an elastomer, it is preferable to use a composition made of butyl rubber and a diene elastomer as the elastomer. By using such a composition as an elastomer, it is possible to keep the internal pressure of the pneumatic tire after running high even when a minute crack occurs in the auxiliary layer (D) made of the elastomer.

 A thermoplastic urethane elastomer is also preferable as the elastomer laminated as the auxiliary layer (D) of the inner liner for the pneumatic tire of the present invention. From the viewpoint of thinning the auxiliary layer (D), generation of cracks, and suppression of extension, it is preferable to use a thermoplastic urethane-based elastomer.

 As an elastomer laminated as an auxiliary layer (D) of the inner liner for a pneumatic tire of the present invention, an auxiliary layer (D) made of a thermoplastic urethane elastomer and an auxiliary layer made of a composition made of butyl rubber and a diene elastomer ( More preferably, D) is multilayered.

 When a plurality of auxiliary layers (D) are laminated, it is preferable that the plurality of auxiliary layers (D) are bonded together via at least one adhesive layer. Thus, the auxiliary layer (D) which consists of a different kind of elastomer can be produced by bonding between several auxiliary layers (D).

 In the inner liner for a pneumatic tire of the present invention, the total thickness of the auxiliary layer (D) made of an elastomer is preferably 50 to 1500 μm. When the thickness of the auxiliary layer (D) made of an elastomer is less than 50 μm, the inner liner's bending resistance and fatigue resistance are lowered, and it is easy to break or crack due to bending deformation during rolling of the tire. Since it becomes easy to extend, there exists a possibility that the internal-pressure holding | maintenance property after tire use may fall large compared with before use. Furthermore, it is difficult to manufacture the tire to make the total thickness of the auxiliary layers (D) below the belt less than 50 μm.

 On the other hand, when the total thickness of the auxiliary layer (D) made of elastomer exceeds 1500 μm, the merit of weight reduction is reduced with respect to the currently used pneumatic tires. From the viewpoints of gas barrier properties, bend resistance, fatigue resistance, and weight reduction of the pneumatic tire of the inner liner, the total thickness of the auxiliary layer (D) made of elastomer is more preferably 100 to 1000 μm, 300 More preferably, it is -800 micrometers.

 In the pneumatic inner liner of the present invention, the 300% modulus of the auxiliary layer (D) made of elastomer is preferably 10 MPa or less in order to suppress the generation and growth of cracks. When the 300% modulus exceeds 10 MPa, the bending resistance and fatigue resistance of the inner liner are lowered. The 300% modulus of the auxiliary layer (D) made of an elastomer is more preferably 8 MPa or less, and further preferably 7 MPa or less.

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

<Measurement of characteristic value of ethylene-vinyl alcohol copolymer (A)>
(1) Ethylene content and saponification degree of ethylene-vinyl alcohol copolymer (A):
It calculated from the spectrum obtained by the H-NMR (nuclear magnetic resonance) measurement which used deuterated dimethyl sulfoxide as a solvent (JEOL Co., Ltd. "JNM-GX-500 type" was used).

(2) Melt flow rate of ethylene-vinyl alcohol copolymer (A):
The ethylene-vinyl alcohol copolymer (A) as a sample was filled in a cylinder with an inner diameter of 9.55 mm and a length of 162 mm of a melt indexer L244 (manufactured by Takara Kogyo Co., Ltd.), and melted at 190 ° C. A 2160 g, 9.48 mm diameter blanker was used to load evenly. The amount of resin extruded per unit time (g / 10 minutes) from an orifice with a diameter of 2.1 mm provided in the center of the cylinder was measured, and this was used as the melt flow rate. However, when the melting point of the ethylene-vinyl alcohol copolymer (A) 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, and the horizontal axis indicates the reciprocal absolute temperature in a semi-logarithmic graph. The logarithm of MFR is plotted on the vertical axis and expressed as a value extrapolated to 190 ° C.

<Synthesis of modified ethylene-vinyl alcohol copolymer (C)>
Synthesis example 1
2 wt% ethylene-vinyl alcohol copolymer (A) (MFR: 5.5 g / 10 min (190 ° C., 2160 g load)) having an ethylene content of 44 mol% and a saponification degree of 99.9% in a pressurized reaction vessel And 8 parts by weight of N-methyl-2-pyrrolidone were charged and stirred at 120 ° C. for 2 hours to completely dissolve the ethylene-vinyl alcohol copolymer (A). To this was added 0.4 part by weight of glycidol as an epoxy compound (B), and then heated at 160 ° C. for 4 hours. After the heating, it was precipitated in 100 parts by weight of distilled water, and N-methyl-2-pyrrolidone and unreacted glycidol were sufficiently washed with a large amount of distilled water to obtain a modified ethylene-vinyl alcohol copolymer (C). . Further, the obtained modified ethylene-vinyl alcohol copolymer (C) was finely reduced 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 and pelletized.

Synthesis example 2
2 wt% ethylene-vinyl alcohol copolymer (A) (MFR: 5.5 g / 10 min (190 ° C., 2160 g load)) having an ethylene content of 44 mol% and a saponification degree of 99.9% in a pressurized reaction vessel And 8 parts by weight of N-methyl-2-pyrrolidone were charged and stirred at 120 ° C. for 2 hours to completely dissolve the ethylene-vinyl alcohol copolymer (A). To this was added 0.3 part by weight of glycidol as an epoxy compound (B), followed by heating at 160 ° C. for 4 hours. After the heating, it was precipitated in 100 parts by weight of distilled water, and N-methyl-2-pyrrolidone and unreacted glycidol were sufficiently washed with a large amount of distilled water to obtain a modified ethylene-vinyl alcohol copolymer (C). . Further, the obtained modified ethylene-vinyl alcohol copolymer (C) was finely reduced 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 and pelletized.

Synthesis example 3
2 wt% ethylene-vinyl alcohol copolymer (A) (MFR: 5.5 g / 10 min (190 ° C., 2160 g load)) having an ethylene content of 44 mol% and a saponification degree of 99.9% in a pressurized reaction vessel And 8 parts by weight of N-methyl-2-pyrrolidone were charged and stirred at 120 ° C. for 2 hours to completely dissolve the ethylene-vinyl alcohol copolymer (A). To this was added 0.4 parts by weight of epoxypropane as an epoxy compound (B), and then heated at 160 ° C. for 4 hours. After the heating, it was precipitated in 100 parts by weight of distilled water, and N-methyl-2-pyrrolidone and unreacted glycidol were sufficiently washed with a large amount of distilled water to obtain a modified ethylene-vinyl alcohol copolymer (C). . Further, the obtained modified ethylene-vinyl alcohol copolymer (C) was finely reduced to a particle size of about 2 mm with a pulverizer, and then sufficiently washed again with a large amount of distilled water. The washed particles were vacuum-dried for 8 hours at room temperature, melted at 200 ° C. using a twin screw extruder, and pelletized.

<Preparation of layer made of modified ethylene-vinyl alcohol copolymer (C)>
Film 1
Using pellets of the modified ethylene-vinyl alcohol copolymer (C) obtained in Synthesis Example 1, a 40 mmφ extruder (PLABOR GT-40-A manufactured by Plastics Engineering Laboratory) and a film forming machine composed of a T die are used. Then, a film was formed under the following extrusion conditions to obtain a single layer film having a thickness of 20 μm.

Type: Single screw extruder (non-vent type)
L / D: 24
Diameter: 40mmφ
Screw: Single-row full flight type, surface copper nitride Screw rotation speed: 40rpm
Die: 550 mm wide coat hanger die Lip gap: 0.3 mm
Cylinder and die temperature settings:
C1 / C2 / C3 / Adapter / Die
= 180/200/210/210/210 (° C)
Film 2
A single-layer film having a thickness of 20 μm was obtained in the same manner as the film 1 except that the pellets of the modified ethylene-vinyl alcohol copolymer (C) obtained in Synthesis Example 2 were used.

Film 3
A single-layer film having a thickness of 20 μm was obtained in the same manner as the film 1 except that the pellets of the modified ethylene-vinyl alcohol copolymer (C) obtained in Synthesis Example 3 were used.

Film 4
As a gas barrier material, an ethylene-vinyl alcohol copolymer (A) having an unmodified ethylene content of 44 mol%, a saponification degree of 99.9%, and an MFR of 5.5 g / 10 min (at 190 ° C. under a load of 2160 g) is modified. A single-layer film having a thickness of 20 μm was obtained in the same manner as the film 1 except that it was used instead of the ethylene-vinyl alcohol copolymer (C).

Film 5
Using the modified ethylene-vinyl alcohol copolymer (C) obtained in Synthesis Example 3 and a thermoplastic polyurethane (Kuraray Co., Ltd., Kuramiron 3190) as an elastomer, using a two-kind three-layer coextrusion device, A three-layer film (thermoplastic polyurethane layer / modified ethylene-vinyl alcohol copolymer (C) layer / thermoplastic polyurethane layer) was produced. The thickness of each layer was 20 μm for both the modified ethylene-vinyl alcohol copolymer (C) layer and the thermoplastic polyurethane layer.

 The coextrusion molding conditions are as follows.

Layer structure:
Thermoplastic polyurethane layer / modified EVOH (C) layer / thermoplastic polyurethane layer (thickness 20/20/20: unit is μm)
Extrusion temperature of each resin:
C1 / C2 / C3 / die = 170/170/220/220 ° C.
Extrusion specifications for each resin:
Thermoplastic polyurethane:
25mmφ extruder P25-18AC (manufactured by Osaka Seiki Co., Ltd.)
Modified EVOH (C):
20mmφ Extruder Lab Machine ME Type CO-EXT (Toyo Seiki Co., Ltd.)
T-die specification:
500mm width for 2 types and 3 layers (Plastic Engineering Laboratory Co., Ltd.)
Cooling roll temperature: 50 ° C
Take-off speed: 4 m / min <Evaluation of layer made of modified ethylene-vinyl alcohol copolymer (C)>
According to the method shown below, the produced films 1 to 5 were evaluated for oxygen permeation amount and bending resistance.

Measurement of oxygen permeation through film:
The produced film was conditioned at 20 ° C.-65% RH for 5 days. According to the method described in JIS K7126 (isobaric method) using MOCON OX-TRAN 2/20 model manufactured by Modern Control Co., Ltd. under the condition of 20 ° C.-65% RH, using the above-mentioned two humidity-controlled samples. Then, the amount of oxygen permeation was measured and the average value was obtained.

Evaluation of bending resistance:
50 sheets of the above-prepared films cut to 21 cm × 30 cm were prepared. Each film was conditioned at 20 ° C.-65% RH for 5 days, and then Rigaku Kogyo Co., Ltd. according to ASTM F 392-74. Using a gelboflex tester manufactured, the number of flexing times is 50, 75, 100, 125, 150, 175, 200, 225, 250, 300, 400, 500, 600, After bending 700 times, 800 times, 1000 times and 1500 times, the number of pinholes was measured. In each bending number, the measurement was performed 5 times, and the average value was defined as the number of pin holes. Taking the number of bends (P) on the horizontal axis and the number of pinholes (N) on the vertical axis, plotting the above measurement results, finding the number of bends (Np1) when the number of pinholes is one by extrapolation, Two digits were used. However, for a film in which no pinholes were observed after 1500 bendings, the number of bendings was increased every 500 times thereafter, and the number of bendings in which pinholes were observed was defined as Np1.

The oxygen permeation amount of the film 1 was 3.0 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg, and showed excellent gas barrier properties. Moreover, when the bending resistance of the film 1 was evaluated according to the above-mentioned method, Np1 was 500 times, indicating extremely excellent bending resistance.

The oxygen permeation amount of the film 2 was 1.0 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg, and showed excellent gas barrier properties. Moreover, when the bending resistance of the film 2 was evaluated according to the above-described method, Np1 was 100 times, indicating extremely excellent bending resistance.

The oxygen permeation amount of the film 3 was 4.0 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg, and showed excellent gas barrier properties. Further, when the bending resistance of the film 3 was evaluated according to the above method, Np1 was 500 times, indicating extremely excellent bending resistance.

The oxygen permeation amount of the film 4 was 4.6 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg, and showed excellent gas barrier properties. Moreover, when the bending resistance of the film 4 was evaluated according to the above method, Np1 was 47 times.

The oxygen permeation amount of the film 5 was 3.5 × 10 ⁻¹² cm ³ · cm / cm ² · sec · cmHg, and showed excellent gas barrier properties. Further, when the bending resistance of the film 5 was evaluated according to the above-mentioned method, Np1 was 5000 times, indicating extremely excellent bending resistance.

<Formulation of rubber composition and production of rubber inner liner and auxiliary layer (D)>
A rubber composition was prepared according to the following blending amount, vulcanized at 145 ° C. for 40 minutes, and then 300% modulus was measured by a method according to JIS K6301. Further, the oxygen transmission amount was measured by the same method as the measurement of the oxygen transmission amount of the film.

Rubber composition 1 (compounding unit: parts by weight)
Natural rubber 30
Br-IIR (Bromobuly1 2244 manufactured by JSR Corporation) 70
GPF Carbon Black (Asahi Carbon Co., Ltd. # 55) 60
SUNPAR2280 (Nihon Sun Oil Co., Ltd.) 7
Stearic acid (Asahi Denka Kogyo Co., Ltd.) 1
NOCCELER DM (Ouchi Shinsei Chemical Co., Ltd.) 1.3
Zinc oxide (manufactured by Hakusui Chemical Co., Ltd.) 3
Sulfur (manufactured by Karuizawa Refinery) 0.5
300% modulus: 6.5 MPa
Oxygen transmission amount: 6.0 × 10 ⁻¹⁰ cm ³ · cm / cm ² · sec · cmHg
Rubber composition 2 (compounding unit: parts by weight)
Br-IIR (Bromobuly1 2244 manufactured by JSR Corporation) 100
GPF Carbon Black (Asahi Carbon Co., Ltd. # 55) 60
SUNPAR2280 (Nihon Sun Oil Co., Ltd.) 7
Stearic acid (Asahi Denka Kogyo Co., Ltd.) 1
NOCCELER DM (Ouchi Shinsei Chemical Co., Ltd.) 1.3
Zinc oxide (manufactured by Hakusui Chemical Co., Ltd.) 3
Sulfur (manufactured by Karuizawa Refinery) 0.5
300% modulus: 6.0 MPa
Oxygen permeation amount: 3.0 × 10 ⁻¹⁰ cm ³ · cm / cm ² · sec · cmHg
<Production and Evaluation of Evaluation Tire>
Example 1
Using an electron beam irradiation device “Curetron EBC200-100 for production” manufactured by Nissin High Voltage Co., Ltd., film 1 was irradiated with an electron beam under the conditions of an acceleration voltage of 200 kV and an irradiation energy of 30 Mrad, and subjected to a crosslinking treatment. And a layer made of a modified ethylene-vinyl alcohol copolymer (C). One side of the obtained crosslinked film was coated with Metalloc R30M manufactured by Toyo Scientific Research Lab as an adhesive layer, and bonded to an auxiliary layer (D) having a thickness of 1000 μm using rubber composition 1, whereby modified ethylene-vinyl An inner liner composed of the alcohol copolymer (C) and the auxiliary layer (D) was produced. Using the obtained inner liner, an emergency pneumatic tire for passenger cars (T125 / 70D16) was produced by a conventional method.

 The tire manufactured as described above was pressed at a load of 6 kN on a drum having a pneumatic pressure of 140 kPa and a rotational speed corresponding to a speed of 80 km / h, and traveled 10,000 km. The internal pressure retention was evaluated by mounting the test tire on a 16 × 4T rim, filling the internal pressure with 420 kPa, and measuring the internal pressure after 3 months, and indexing it with the following formula.

Internal pressure retention property = ((a / c) / (b / 420)) × 100 (1)
In the formula, a, b and c are as follows.

a: Internal pressure after 3 months of test tire b: Internal pressure after 3 months described in Comparative Example 1 c: Initial air pressure of test tire (420 for emergency tire, 240 for PSR)
The conditions and results are shown in Table 1. The result was expressed as an index with the result of Comparative Example 1 being 100. Larger values indicate better internal pressure retention.

Example 2
An inner liner and a pneumatic tire were produced in the same manner as in Example 1 except that the film 2 was used instead of the film 1, and the internal pressure retention was evaluated. The conditions and results are shown in Table 1.

Example 3
An inner liner and a pneumatic tire were produced in the same manner as in Example 1 except that the film 3 was used in place of the film 1, and the internal pressure retention was evaluated. The conditions and results are shown in Table 1.

Comparative Example 1
A passenger car that does not have a modified ethylene-vinyl alcohol copolymer (C) and an auxiliary layer (D) in the same manner as described above, using an inner liner using the rubber composition 2 used as a normal rubber inner liner. An emergency pneumatic tire (T125 / 70D16) was prepared. The conditions and results are shown in Table 1.

Comparative Example 2
An inner liner was prepared by bonding a layer using polyethylene (oxygen permeation amount: 1.6 × 10 ⁻¹¹ cm ³ · cm / cm ² · sec · cmHg) and the auxiliary layer (D). Using the obtained inner liner, an emergency pneumatic tire for passenger cars (T125 / 70D16) was produced by a conventional method. The conditions and results are shown in Table 1.

Comparative Example 3
In general, the inner liner using the rubber composition 2 used as an ordinary rubber inner liner is used, and the modified ethylene-vinyl alcohol copolymer (C) and the auxiliary layer (D) are not used in the same manner as described above. A pneumatic tire for passenger cars (195 / 65R15) was produced. The internal pressure retention was evaluated by mounting the test tire on a 6JJ × 15 rim, filling the internal pressure with 240 kPa, and measuring the internal pressure after 3 months, and indexing with the formula (1). The conditions and results are shown in Table 1.

Comparative Example 4
The inner liner was produced by bonding the layer using the film 1 and the auxiliary layer (D). Using the obtained inner liner, a general passenger car pneumatic tire (195 / 65R15) was produced by a conventional method. The internal pressure retention was evaluated by mounting the test tire on a 6JJ × 15 rim, filling the internal pressure with 240 kPa, and measuring the internal pressure after 3 months, and indexing with the formula (1). The conditions and results are shown in Table 1.

(result)
From Table 1, the emergency pneumatic tire using the inner liner including the layer made of the modified ethylene-vinyl alcohol copolymer (C) of Examples 1 to 3 is much more internal pressure than Comparative Examples 1 to 4. It was found that retention was improved.

 In particular, as compared with ordinary passenger car tires, emergency pneumatic tires require an inner liner having higher bending resistance while maintaining gas barrier properties. However, according to the emergency pneumatic tire according to the present invention, gas barriers are required. It is possible to greatly improve the air pressure and improve the air pressure retention.

It is sectional drawing along the tire rotating shaft of the emergency pneumatic tire which concerns on this embodiment.

Explanation of symbols

6 Belt layer 12 Bead core 14 Carcass 20 Tread portion 20A Tread end portion 22 Tread rubber 24 Beat portion 26 Side portion 28 Side rubber 30 Carcass ply 30A Turned portion 30B Main body 41 Layer 42 made of modified ethylene-vinyl alcohol copolymer (C) Auxiliary Layer 100 Emergency pneumatic tire

Claims (12)

An emergency pneumatic tire that is used in place of a standard tire for automobiles, has a tire width that is extremely narrow compared to the standard tire, the tire outer diameter is substantially the same, and the use internal pressure is high,
Epoxy compound (B) 1 selected from glycidol or epoxy propane with respect to 100 parts by weight of ethylene-vinyl alcohol copolymer (A) having an ethylene content of 25 to 50 mol% and a saponification degree of 90% or more. Modified ethylene-vinyl alcohol copolymer (C) obtained by reacting ˜50 parts by weight ,
An auxiliary layer adjacent to the layer made of an elastomer and made of the modified ethylene-vinyl alcohol copolymer (C);
Emergency pneumatic tire, characterized in that it comprises an inner liner comprising a. The oxygen permeation amount at 20 ° C. and 65 RH% of the layer made of the modified ethylene-vinyl alcohol copolymer (C) is 3.0 × 10 ⁻¹² cm ³ · cm ² · sec · cmHg or less. The emergency pneumatic tire according to claim 1 , wherein the pneumatic tire is an emergency. The emergency pneumatic tire according to claim 1 or 2 , wherein the modified ethylene-vinyl alcohol copolymer (C) is crosslinked. The emergency pneumatic tire according to any one of claims 1 to 3 , wherein the layer made of the modified ethylene-vinyl alcohol copolymer (C) has a thickness of 50 µm or less. The modified ethylene - the vinyl alcohol copolymer (C) consisting of a layer and the auxiliary layer, emergency air according to claim 1, characterized in that it is bonded through at least one layer of adhesive layer Tires. ^2. The emergency air according to claim 1 , wherein an oxygen permeation amount of the auxiliary layer at 20 ° C. and 65 RH% is 3.0 × 10 ⁻⁹ cm ³ · cm ² · sec · cmHg or less. Tires. The emergency pneumatic tire according to claim 1 , wherein butyl rubber or halogenated butyl rubber is used for the auxiliary layer. The emergency pneumatic tire according to claim 1 , wherein a diene elastomer is used for the auxiliary layer. The emergency pneumatic tire according to claim 1 , wherein a thermoplastic urethane-based elastomer is used for the auxiliary layer. 2. The emergency pneumatic tire according to claim 1 , wherein when a plurality of the auxiliary layers are laminated, the plurality of auxiliary layers are bonded together through at least one adhesive layer. 2. The emergency pneumatic tire according to claim 1 , wherein a total thickness of the auxiliary layers is 50 to 1500 μm. The emergency pneumatic tire according to claim 1, wherein the ethylene-vinyl alcohol copolymer (A) has an ethylene content of 44 mol% and a saponification degree of 99.9%.

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