JP2011161986A - Inner liner for pneumatic tire and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inner liner for a pneumatic tire, with a lightweight, which is excellent in a gas barrier property, and shows an excellent flexibility even in an extreme low temperature condition, and to provide the pneumatic tire applied with the inner liner. <P>SOLUTION: The inner liner for the tire includes at least a layer made of a resin composition (D) with a viscoelastic body (C) dispersed in a resin containing a modified ethylene-vinyl alcohol copolymer (B) obtained by reacting an ethylene-vinyl alcohol copolymer (A). The viscoelastic body (C) is blended with 1-30% of softener with a glass transition temperature equal to or less than -90°C. The pneumatic tire includes the inner liner on the tire inner surface inside a carcass. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an inner liner for a pneumatic tire excellent in gas barrier properties and a pneumatic tire, and more particularly to an inner liner for a pneumatic tire that has improved durability by exhibiting excellent bending resistance even at extremely low temperatures. It relates to pneumatic tires.

  Since tires for vehicles such as airplanes, trucks, buses, and passenger cars are used in various environments, it is necessary to withstand use at extremely low temperatures. For example, in the case of aircraft tires, the aircraft may fly in the atmosphere of −65 ° C., and in the case of tires for vehicles such as trucks, buses, and passenger cars, it may be used at −50 ° C.

  Conventionally, a rubber composition mainly composed of so-called butyl rubber such as butyl rubber or halogenated butyl rubber has been used for the inner liner disposed on the inner surface of the tire in order to maintain the internal pressure of the tire.

  However, these rubber compositions containing butyl rubber as the main raw material have low gas barrier properties, and the thickness of the inner liner occupying the tire must be about 1 mm in order to sufficiently maintain the internal pressure of the tire. May increase to about 5%, which may impair fuel consumption.

  There are many resins that have better gas barrier properties than butyl rubber, but if the air permeation amount is about one-tenth that of a butyl inner liner, the thickness exceeds 100 μm in order to improve the internal pressure retention. In such a case, the effect of reducing the weight of the tire is small, and there is a possibility that the inner liner may be broken or cracked due to deformation during bending of the tire.

  Therefore, as a method for improving the bending resistance of the inner liner, for example, Patent Document 1 describes a method of using an elastomer containing a halide of isobutylene paramethylstyrene copolymer for a nylon resin having a melting point of 170 to 230 ° C. ing. However, this method may impair the excellent gas barrier properties of the nylon resin.

  On the other hand, an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) is known to have an air permeation amount of 1/100 or less of a butyl rubber composition, and is 100 μm or less. Even with the thickness, the internal pressure of the tire can be sufficiently maintained. By applying this EVOH to the inner liner of the tire, the weight of the tire can be reduced. Therefore, it can be said that it is effective to use EVOH for the inner liner. For example, Patent Document 2 describes a pneumatic tire including an inner liner made of EVOH.

  However, EVOH usually has a much higher elastic modulus than the other rubbers described above, and sometimes breaks or cracks due to deformation during bending. Therefore, when the inner liner made of EVOH is used, the internal pressure retention before using the tire is greatly improved, but the internal pressure retention is lower than that before using the tire after being subjected to bending deformation during rolling of the tire. There was something to do.

  As means for solving this problem, Patent Document 3 discloses a composite film composed of 60 to 99% by weight of EVOH having an ethylene content of 20 to 70 mol%, a saponification degree of 85% or more, and 1 to 40% by weight of a hydrophobic plasticizer. The method used for the inner liner is described.

  Furthermore, Patent Document 4 describes a technique in which a modified EVOH obtained by reacting 1 to 50 parts by weight of an epoxy compound with 100 parts by weight of EVOH having an ethylene content of 25 to 50 mol% is used as an inner liner. The inner liner has higher bending resistance while maintaining the gas barrier property as compared with a tire inner liner made of conventional EVOH.

JP-A-11-199713 JP-A-6-40207 JP 2002-52904 A JP 2004-176048 A

  The inner liner of a tire according to the prior art described above is suitable for application to a tire because it is excellent in gas barrier properties and bending resistance and is lightweight when used under normal temperature conditions.

  However, as described above, for example, vehicle tires such as airplanes, trucks, buses, and passenger cars are sometimes used at extremely low temperatures below -50 ° C. There is still room for improvement, such as cracking due to insufficient flexibility at low temperatures, and inability to exhibit excellent barrier properties.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an inner liner for a tire that is light and excellent in gas barrier properties and exhibits excellent bending resistance even when used under extremely low temperature conditions such as winter. It is to provide. Further, the present invention proposes a pneumatic tire provided with such an inner liner for tire.

  The inventor has been diligently studying how to solve the above-described problems in the inner liner of the tire, and dispersed a viscoelastic body containing a softening agent having a glass transition temperature of −90 ° C. or less in the resin composition. It has been found that by including a layer composed of a resin composition in the inner liner of a tire, the bending resistance under cryogenic conditions can be improved, and the present invention has been completed. That is, the gist configuration of the present invention that satisfies the above-described problems is as follows.

(1) A resin composition (D) in which a viscoelastic body (C) is dispersed in a resin containing a modified ethylene-vinyl alcohol copolymer (B) obtained by reacting an ethylene-vinyl alcohol copolymer (A). And a viscoelastic body (C) containing 1-30% by mass of a softening agent having a glass transition temperature of -90 ° C. or lower. Tire inner liner.
Here, the blending ratio of the softening agent is a ratio with respect to 100% by mass of the viscoelastic body.

(2) The innerliner for tire according to (1), wherein at least a part of the viscoelastic body (C) has a functional group having a high affinity for a hydroxyl group.

(3) The viscoelastic body (C) is at least one compound selected from the group consisting of maleic acid, maleic anhydride, isocyanate, isothiocyanate, alkoxysilane, epoxy, amine and a compound containing a boron-containing group. The tire inner liner according to (1) above, which is modified or at least a part of the viscoelastic body (C) has a boron-containing group. Here, the “boron-containing group” refers to a functional group containing boron.

(4) The modified ethylene-vinyl alcohol copolymer (B) obtained by reacting 1 to 50 parts by mass of the epoxy compound (E) with 100 parts by mass of the ethylene-vinyl alcohol copolymer (A). The inner liner for tires according to any one of the above (1) to (3).

(5) The innerliner for tire according to any one of (1) to (4), wherein the saponification degree of the ethylene-vinyl alcohol copolymer (A) is 90% or more.

(6) The inner liner for tire according to (4), wherein the molecular weight of the epoxy compound (E) is 500 or less.

(7) The innerliner for tire according to (6), wherein the epoxy compound (E) is glycidol or epoxypropane.

(8) The tire inner liner according to any one of (1) to (7), wherein the ethylene content of the ethylene-vinyl alcohol copolymer (A) is 25 to 50 mol%.

(9) The tire inner liner according to any one of the above (1) to (8), wherein the resin composition (D) has a temperature at break elongation of 12% of −55 ° C. or lower.
Here, the temperature (° C.) at 12% elongation at break of the resin composition (D) is a strip having a width of 15 mm using the resin composition formed as a single-layer film having a thickness of 20 μm by a twin-screw extruder. The temperature measured when the elongation at break is 12% is tested using, for example, an autograph under the conditions of a chuck interval of 50 mm and a tensile speed of 1000 mm / min.

(10) The inner liner for tires according to any one of (1) to (9), wherein the content of the viscoelastic body (C) in the resin composition (D) is in the range of 10 to 70% by mass. .

(11) The innerliner for tire according to any one of (1) to (10), wherein the viscoelastic body (C) has an average particle size of 5 μm or less.

(12) The innerliner for tire according to any one of (1) to (11), wherein the layer made of the resin composition (D) is crosslinked.

(13) A pneumatic tire comprising the tire inner liner according to any one of the above (1) to (12) on a tire inner surface inside a carcass.

(14) The pneumatic tire according to (13), which is for an aircraft, a truck, or a bus.

  The inner liner for tires according to the present invention is lightweight and excellent in gas barrier properties, and exhibits excellent bending resistance even at extremely low temperatures, and therefore has excellent durability. Therefore, by applying the inner liner according to the present invention to tires such as airplanes, trucks, buses, passenger cars, etc., it is possible to reduce the weight of the tires, and when traveling under cryogenic conditions, It is possible to provide a tire that is less susceptible to inner cracks.

It is the schematic which shows an example of the embodiment of the suitable screw structure of the extruder used in this invention.

Hereinafter, the present invention will be described in more detail.
The inner liner for tire of the present invention is a modified ethylene-vinyl alcohol copolymer (B) obtained by reacting an ethylene-vinyl alcohol copolymer (A) (hereinafter sometimes abbreviated as EVOH (A)). (Hereinafter, may be abbreviated as modified EVOH (B)) In a resin containing 1 to 30% of a softening agent having a glass transition temperature of −90 ° C. or less, a viscoelastic body (C) is dispersed. In addition, it is characterized by including at least a layer made of the resin composition (D). Here, the said inner liner may be comprised only by the resin composition (D), and may be included in a part.

  For example, modified EVOH (B) obtained by reacting the epoxy compound (E) with the EVOH (A) has a lower elastic modulus than that of ordinary EVOH. Further, by dispersing a viscoelastic body (C) containing 1 to 30% of a softener having a glass transition temperature of −90 ° C. or less in the resin containing the modified EVOH (B), a resin composition having a lower elastic modulus. A thing (D) can be obtained. Therefore, the inner liner including the layer made of the resin composition (D) has a greatly reduced elastic modulus and is excellent in bending resistance, and thus hardly breaks or cracks.

  Further, by modifying the EVOH (A) and changing the hydroxyl group expressing the crystallinity into a chemical structure as shown in the following formula (I), for example, the crystallinity of the EVOH (A) is lowered. Can be flexible.

（式中、Ｒ^１、Ｒ^２およびＲ^３は、Ｃ、ＨまたはＯのいずれかを含む。）

(In the formula, R ¹ , R ² and R ³ include any of C, H or O.)

  The viscoelastic body (C) preferably contains either a diene rubber or a non-diene rubber. When the viscoelastic body (C) contains either a diene rubber or a non-diene rubber, the resin composition (D) can behave elastically in a wide temperature range, so that fatigue resistance can be improved. .

  The main chain skeleton of the viscoelastic body (C) includes butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), hydrogenated SBR, natural rubber (NR), butyl rubber (IIR), chlorosulfone. Polyethylene rubber (CSM), ethylene propylene rubber (EPM, EPDM), ethylene-butene rubber, ethylene-octene rubber, chloroprene rubber (CR), acrylic rubber (ACM), silicone rubber, styrene-ethylene-butylene-styrene copolymer ( SEBS), styrene-isoprene-styrene copolymer (SIS), modified natural rubber partially having functional groups, nitrile rubber (NBR), and viscoelastic bodies containing halogen groups such as brominated butyl rubber (Br-) IIR), chlorinated butyl rubber (Cl-IIR) and the following formula (II) Such as brominated isobutylene -p- methylstyrene being the like.

  In the innerliner for tire of the present invention, it is preferable that at least a part of the viscoelastic body (C) has a functional group having a high affinity for a hydroxyl group. When at least a part of the viscoelastic body (C) has a functional group having a high affinity for a hydroxyl group, variation in the dispersion diameter of the viscoelastic body (C) in the modified EVOH (B) is reduced, The average particle size can be reduced.

  Here, functional groups having high affinity for hydroxyl groups include boron-containing groups, maleic acid residues, maleic anhydride residues, hydroxyl groups, carboxyl groups, isocyanate groups, isothiocyanate groups, epoxy groups, amino groups, alkoxysilyls. Groups and the like.

  Further, the viscoelastic body (C) is modified with at least one compound selected from the group consisting of maleic acid, maleic anhydride, isocyanate, isothiocyanate, alkoxysilane, epoxy, amine and a compound containing a boron-containing group. Or at least a part of the viscoelastic body (C) preferably has a boron-containing group.

  The functional group is not limited to those that can react directly with the modified EVOH (B) molecule, but includes examples in which the functional group can react with the modified EVOH (B) molecule by pre-reaction with another drug.

  The functional group may be imparted in advance by treatment during polymerization of the polymer of the viscoelastic body (C) or post polymerization, or the modified EVOH (B) and the resin composition (D) are kneaded. At this time, or immediately before kneading, the modified EVOH (B) may be introduced by reaction with other low molecular weight compounds.

  Examples of the boron-containing group include a boronic acid group or a functional group such as a boron-containing group that can be converted to a boronic acid group in the presence of water. Among the boron-containing groups, the boronic acid group is represented by the following formula (III).

  The boron-containing group that can be converted to a boronic acid group in the presence of water refers to a boron-containing group that can be converted to a boronic acid group represented by the above formula (III) by hydrolysis in the presence of water. . More specifically, water alone, a mixture of water and an organic solvent (toluene, xylene, acetone, etc.), a mixture of a 5% aqueous boric acid solution and the organic solvent, and the like at room temperature to 150 ° C. It means a functional group that can be converted to a boronic acid group when hydrolyzed for 10 to 120 minutes.

  Representative examples of such functional groups include boronic acid ester groups represented by the following formula (IV), boronic acid anhydride groups represented by the following formula (V), boronic acid groups represented by the following formula (VI), and the like. Is mentioned.

  In the formula, X and Y are a hydrogen atom, an aliphatic hydrocarbon group (such as a linear or branched alkyl group or alkenyl group having 1 to 20 carbon atoms), an alicyclic hydrocarbon group (a cycloalkyl group or a cyclohexane). Alkenyl group, etc.) and aromatic hydrocarbon groups (phenyl group, biphenyl group, etc.), and X and Y may be the same or different.

However, the case where both X and Y are hydrogen atoms is excluded. X and Y may be bonded. R ¹ , R ² and R ³ represent the same hydrogen atom, aliphatic hydrocarbon group, alicyclic hydrocarbon group and aromatic hydrocarbon group as those of X and Y, and R ¹ , R ² and R ³ are It may be the same or different. M represents an alkali metal. Further, the above X, Y, R ¹ , R ² and R ³ may have other groups such as a hydroxyl group, a carboxyl group, a halogen atom and the like.

  Specific examples of the boronic acid ester group represented by the above formula (IV) include boronic acid dimethyl ester group, boronic acid diethyl ester group, boronic acid dibutyl ester group, boronic acid dicyclohexyl ester group, boronic acid ethylene glycol ester group, boron Propylene glycol ester group, boronic acid 1,3-propanediol ester group, boronic acid 1,3-butanediol ester group, boronic acid neopentyl glycol ester group, boronic acid catechol ester group, boronic acid glycerin ester group, boronic acid Examples thereof include a trimethylolethane ester group, a boronic acid trimethylolpropane ester group, and a boronic acid diethanolamine ester group.

  Examples of the boronic acid group represented by the above formula (VI) include an alkali metal base of boronic acid. Specific examples include sodium boronate base and potassium boronate base.

  Among such boron-containing groups, a boronic acid cyclic ester group is preferable from the viewpoint of thermal stability. Examples of the boronic acid cyclic ester group include a boronic acid cyclic ester group containing a 5-membered ring or a 6-membered ring. Specific examples include a boronic acid ethylene glycol ester group, a boronic acid propylene glycol ester group, a boronic acid 1,3-propanediol ester group, a boronic acid 1,3-butanediol ester group, and a boronic acid glycerin ester group. .

  In the innerliner for tire of the present invention, the polymer material constituting the viscoelastic body (C) has a random molecular structure, and a block or segment having a melting point (Tm) or glass transition temperature (Tg) of 50 ° C. or higher. It is preferable that the amount is small or not included. For example, if the viscoelastic body (C) contains a block or segment of styrene, the styrene layer is in a glass state near room temperature and behaves very hard, which may reduce the flexibility of the resin composition (D). is there. For example, if it is random even if it contains styrene, the flexibility of the resin composition (D) can be ensured. Here, Tg was measured by differential scanning calorimetry (DSC).

  On the other hand, the polymer material constituting the viscoelastic body (C) may contain a small amount of a block component for maintaining the pellet shape. For example, when the polymer material constituting the viscoelastic body (C) is a styrene-ethylene-butylene-styrene copolymer, the polystyrene content of the copolymer is preferably 19% or less, and 16% or less. Is more preferable.

  Moreover, in this invention, although the manufacturing method of the said modified EVOH (B) is not specifically limited, 1-50 mass parts of said epoxy compounds (E) are made to react with respect to 100 mass parts of said EVOH (A). Is preferred.

  More specifically, the modified EVOH is produced by adding the epoxy compound (E) to the EVOH solution in the presence of an acid catalyst or an alkali catalyst, preferably in the presence of an acid catalyst, and reacting them.

  Examples of the reaction solvent include aprotic polar solvents such as dimethyl sulfoxide, dimethylformaldehyde, dimethylacetamide, and N-methylpyrrolidone. Examples of the acid catalyst include p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, and boron trifluoride. Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, lithium hydroxide, Examples include sodium methoxide. The catalyst amount is preferably in the range of 0.0001 to 10 parts by mass with respect to 100 parts by mass of EVOH.

  The modified EVOH (B) can also be produced by reacting the EVOH (A) and the epoxy compound (E) in an extruder. Although there is no restriction | limiting in particular as an extruder to be used, EVOH (A) and an epoxy compound are used at the temperature of about 200 to 300 degreeC using a single screw extruder, a twin screw extruder, or a multi-screw extruder more than two screws. It is preferable to react (E).

  As said epoxy compound (E), a monovalent | monohydric epoxy compound is preferable. The epoxy compound having a valence of 2 or more may undergo a crosslinking reaction with EVOH to generate gels, blisters, and the like, thereby reducing the quality of the inner liner.

  The epoxy compound (E) preferably has a molecular weight of 500 or less from the viewpoint of ease of production of modified EVOH, gas barrier properties, flex resistance and fatigue resistance. Among such compounds, glycidol, Epoxypropane and epoxybutane are preferred, and epoxypropane is particularly preferred.

  Moreover, it is preferable that the said epoxy compound (E) reacts 1-50 mass parts with respect to 100 mass parts of EVOH (A), It is still more preferable to react 2-40 mass parts, 5-35 mass parts It is more preferable to react.

  The EVOH (A) preferably has a melt flow rate (MFR) of 0.1 to 30 g / 10 min at 190 ° C. under a load of 2160 g from the viewpoint of obtaining gas barrier properties, flex resistance and fatigue resistance. More preferably, it is 0.3-25 g / 10min, and it is still more preferable that it is 0.5-20 g / 10min.

  The EVOH (A) preferably has a saponification degree of 90% or more. By setting the degree of saponification to 90% or more, it is possible to sufficiently ensure gas barrier properties and thermal stability during molding. The saponification degree of the EVOH (A) is more preferably 95% or more, and further preferably 99% or more.

  The EVOH (A) preferably has an ethylene content of 25 to 50 mol%. By setting the ethylene content to 25 mol% or more, bending resistance, fatigue resistance and melt moldability are good, and by setting it to 50 mol% or less, gas barrier properties can be sufficiently secured. It is. In addition, the ethylene content of the EVOH (A) is more preferably 30 to 48 mol%, and further preferably 35 to 45 mol%.

  The resin composition (D) preferably has a temperature at break elongation of 12% of −55 ° C. or lower. If the temperature at the time of elongation at break of 12% is −55 ° C. or less, durability when used under extremely low temperature conditions can be improved.

  Moreover, it is preferable that the content rate of the viscoelastic body (C) in the said resin composition (D) is the range of 10-70 mass%. When the content of the viscoelastic body (C) is 10% by mass or more, the bending resistance can be more effectively improved, and when 70% by mass or less, the gas barrier property is lowered. It is possible to prevent.

  Furthermore, the average particle diameter of the viscoelastic body (C) is preferably 5 μm or less. By setting the average particle size of the viscoelastic body (C) to 5 μm or less, it is possible to more effectively improve the bending resistance of the layer made of the resin composition (D). The average particle diameter of the viscoelastic body (C) can be measured, for example, by freezing a sample, cutting the sample with a microtome, and observing it with a transmission electron microscope (TEM).

  The resin composition (D) can be adjusted by kneading the modified EVOH (B) and the viscoelastic body (C). The resin composition (D) is preferably in the form of a film when the inner liner is produced, and the layer made of the resin composition (D) is melt-molded, preferably extruded by a T-die method, an inflation method, or the like. By molding, it is preferably molded into a film or sheet at a melting temperature of 120 to 270 ° C. and used as an inner liner.

  The layer made of the resin composition (D) is preferably crosslinked. The layer composed of the resin composition (D) is cross-linked, thereby suppressing the deformation of the inner liner in the tire vulcanization process and the deterioration of the gas barrier property, flex resistance, fatigue resistance, etc. of the inner liner. It is possible.

  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, and γ rays. Particularly preferred. The resin and viscoelastic body are preferably electron beam cross-linked. The electron beam irradiation is preferably performed after the resin composition (D) is processed into a molded body such as a film or a sheet.

  The dose of the electron beam is preferably in the range of 2.5 to 60 Mrad, and more preferably in the range of 5 to 50 Mrad. If the electron beam dose is 2.5 Mrad or more, the cross-linking proceeds sufficiently quickly, and if it is 60 Mrad or less, the molded article is not deteriorated.

≪About softener≫
The softening agent used for the viscoelastic body (C) of the present invention has a glass transition temperature (Tg) of −90 ° C. or lower. When the glass transition temperature (Tg) of the softening agent exceeds −90 ° C., crack resistance under extremely low temperature conditions cannot be ensured. Here, the glass transition temperature (Tg) of the softening agent is a value measured with a differential scanning calorimeter (DSC) in accordance with ASTM D3418-82 (Peapproved 1988).

  The softener is not particularly limited as long as Tg is −90 ° C. or lower, and can be appropriately selected from rubber softeners. For example, phosphoric acid such as tris (2-methylhexyl) phosphate It is also possible to use sebacic acid esters such as esters and di-n-butyl sebacate. These softeners may be used alone or in combination of two or more.

  The blending amount of the softening agent in the resin composition (D) of the present invention is 1 to 30% by mass in the viscoelastic body (C) component, and preferably in the range of 2 to 25% by mass. If the blending amount of the softening agent is less than 1% by mass, crack resistance under extremely low temperature conditions cannot be ensured. On the other hand, if it exceeds 30% by mass, the gas barrier property of the rubber composition is greatly reduced. Further, if the blending amount of the softening agent is 2% by mass or more, the effect of improving crack resistance under extremely low temperature conditions is large, while if it is 25% by mass or less, the gas barrier property of the rubber composition is sufficiently increased. Can be secured.

The tire inner liner according to the present invention has been described in detail above.
The pneumatic tire of the present invention is characterized by comprising the inner liner for a tire of the present invention described above on the inner surface of the tire inside the carcass. The pneumatic tire of the present invention comprising the tire inner liner according to the present invention is lightweight, has a gas barrier property and excellent air retention, and does not impair durability even when used at extremely low temperatures such as in winter.

  The pneumatic tire of the present invention is effective when used for aircraft, trucks, or buses. This is because, conventionally, it has been particularly difficult to maintain durability at extremely low temperatures in the above-described heavy vehicle.

Below, based on an Example, this invention is demonstrated in detail.
The inner liners for tires (Examples 1 to 4 and Comparative Examples 1 to 4) of the formulation described in Table 1 are manufactured by the manufacturing method described later, and the air retention and crackability under cryogenic conditions are as follows. Evaluation was made by the evaluation method described later. Table 1 shows the results.

  Here, the production methods of “Synthesis Example 1” and “Synthesis Example 2” described in Table 1 are as follows.

<< Synthesis Example 1 >>
(Modified EVOH)
In a pressurized reaction vessel, 2 parts by mass of EVOH having an ethylene content of 44 mol% and a saponification degree of 99.9% (190 ° C., MFR under 2160 g load: 5.5 g / 10 min) and N-methyl-2-pyrrolidone 8 parts by mass were charged and stirred at 120 ° C. to completely dissolve EVOH. To this was added 0.4 part by mass of epoxypropane as an epoxy compound (E), and then heated at 160 ° C. for 4 hours.

  After the heating, it was precipitated in 100 parts by mass of distilled water, and N-methyl-2-pyrrolidone and unreacted epoxypropane were sufficiently washed with a large amount of distilled water to obtain modified EVOH.

  Further, the obtained modified EVOH was fined to a particle size of about 2 mm with a pulverizer, and then sufficiently washed with a large amount of distilled water again. The washed particles were vacuum-dried at room temperature for 8 hours, and then melted at 200 ° C. using a twin-screw extruder to be pelletized.

<< Synthesis Example 2 >>
(Modified EVOH)
A TEM-35BS extruder (37 mmφ, L / D = 52.5) manufactured by Toshiba Machine Co., Ltd. was used, and a screw configuration and a vent and a pressure inlet were installed as shown in FIG. The barrel C1 was water-cooled, the barrels C2 to C3 were set to 200 ° C., the barrels C4 to C15 were set to 240 ° C., and the operation was performed at a screw rotation speed of 400 rpm. EVOH is fed from the C1 resin feed port at a rate of 15 kg / hr, melted, water and oxygen are removed from the vent 1, and glycidol is fed from the C9 hydraulic inlet at a rate of 2.5 kg / hr. (Pressure during feeding: 6 MPa) to obtain glycidol-modified EVOH.

  Further, the specifications and synthesis examples of the viscoelastic body (C) described in Table 1 are as shown below.

≪Synthesis example of isocyanate-modified SBR≫
A reactor having an internal volume of 5 L purged with nitrogen was charged with 2000 g of cyclohexane, 450 g of 1,3-butadiene, 50 g of styrene, and 25 g of tetrahydrofuran. A polymerization reaction was performed.

  After the polymerization conversion rate reached 100%, 2 equivalents of diphenylmethane diisocyanate were added to n-butyllithium to react. Furthermore, 0.7 g of di-tert-butyl-p-cresol as an anti-aging agent was added to 100 g of rubber, and desolubilization and drying were performed by a conventional method.

≪Modified EP≫
As modified polyethylene (EP), Tuffmer MP0620 manufactured by Mitsui Chemicals, Inc. was used.

≪Synthesis example of maleic anhydride modified SBR≫
Into a dried and nitrogen-substituted 800 ml pressure-resistant glass container, 300 g of cyclohexane, 41.25 g of 1,3-butadiene, 8.75 g of styrene, and 0.38 mmol of ditetrahydrofurylpropane are injected, and n-butyllithium is added thereto. After adding 0.43 mmol of (BuLi), polymerization was carried out at 50 ° C. for 1.5 hours.
To this polymerization system, 0.43 mmol of 3-triethoxysilylpropyl succinic anhydride was further added as a terminal modifier, and then a modification reaction was performed for another 30 minutes.
Thereafter, 0.5 ml of 2,5-di-t-butyl-p-cresol (BHT) isopropanol 5% by weight solution is added to the polymerization system to stop the reaction, and further dried according to a conventional method. Maleic anhydride-modified SBR was obtained.

≪Epoxy modified NR≫
As an epoxy-modified natural rubber (E-NR), EPOXYPRENE25 manufactured by Muang Mai Guthrie Public Company Limited was used.

≪Maleic anhydride modified SEBS≫
As maleic anhydride-modified styrene-ethylene-butylene-styrene copolymer (SEBS), Tuftec M1943 manufactured by Asahi Kasei was used.

<< Brominated isobutylene-p-methylstyrene >>
Exxpro89-4 manufactured by ExxonMobil Chemical was used as brominated isobutylene-p-methylstyrene.

  Furthermore, the specifications of “softener A” and “softener B” described in Table 1 and the method for measuring the glass transition temperature (Tg) of each softener are as follows.

≪Softener A≫
Idemitsu Kosan Co., Ltd. Diana Process Oil NS-28, Tg = −80 ° C. was used.

≪Softener B≫
Daihachi Chemical Factory Co., Ltd. TOP, tris (2-ethylhexyl) phosphate, Tg = −120 ° C. was used.

<< Measurement Method of Glass Transition Temperature (Tg) of Softener >>
The Tg of the softener used was measured with a differential scanning calorimeter (DSC) according to ASTM D3418-82 (Peapproved 1988).

≪Method for producing tire inner liner≫
The modified EVOH obtained in Synthesis Examples 1 and 2 and the viscoelastic body (C) shown in the table are kneaded with a twin-screw extruder to obtain a resin composition (D) having a formulation shown in Tables 1 and 2. It was. Next, the resin composition (D) was irradiated with an electron beam under the conditions of an acceleration voltage of 200 kV and an irradiation energy of 30 Mrad using an Nisshin High Voltage Co., Ltd. electron beam irradiation apparatus “Curetron EBC200-100 for production”. The tire was then subjected to a crosslinking treatment to produce a tire inner liner.

  The inner liner of Comparative Example 1 was composed of 30 parts by mass of natural rubber and 70 parts by mass of brominated butyl rubber [manufactured by JSR, Bromobutyl 2244], GPF carbon black [manufactured by Asahi Carbon Co., Ltd., # 55]. 60 parts by mass, SUNPAR 2280 [manufactured by Nippon Sun Oil Co., Ltd.] 7 parts by mass, stearic acid [manufactured by Asahi Denka Kogyo Co., Ltd.], 1 part by mass, NOCCELER DM [manufactured by Ouchi Shinsei Chemical Co., Ltd.] 1.3 parts by mass Parts, zinc oxide [manufactured by Hakusui Chemical Co., Ltd.] 3 parts by mass and sulfur [manufactured by Karuizawa Seisensho] 0.5 parts by mass were prepared.

≪Evaluation of temperature (° C.) at 12% elongation at break of resin composition (D) ≫
Using a twin screw extruder manufactured by Toyo Seiki Co., Ltd., a film was formed under the following extrusion conditions to produce a single layer film having a thickness of 20 μm. Next, using this film, a strip-shaped test piece having a width of 15 mm was prepared and left in a temperature-controlled room at -36 ° C. and 50% RH for one week, and then autograph [AG] manufactured by Shimadzu Corporation -A500 type | mold], it tested by the conditions of chuck | zipper space | interval 50mm, and the tension | pulling speed of 1000 mm / min, and measured the temperature whose breaking elongation is 12%.

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

≪About evaluation of gas barrier property (index) ≫
The gas permeability coefficient of each rubber composition was measured according to method A (differential pressure method) of JIS K 7126 “Plastic film and sheet gas permeability test method”, and the gas permeability coefficient of the rubber composition of Comparative Example 1 was set to 100. The index was displayed. A larger index value indicates a smaller gas permeability coefficient and better air retention.

≪Evaluation of crack resistance (index) under cryogenic conditions≫
The embrittlement temperature of each rubber composition was measured by the low temperature impact embrittlement test method described in JIS K 6301, and the embrittlement temperature of the rubber composition of Comparative Example 1 was indicated as 100, which was displayed as an index. A larger index value indicates better crack resistance under cryogenic conditions.

  Looking at Comparative Example 2, when 30% or more of a softening agent having a glass transition temperature Tg (° C.) of −90 ° C. or less is blended, the crack resistance under extremely low temperature conditions is improved, but the gas barrier property is lowered. I understand. Moreover, when the comparative examples 3 and 4 are seen, when the glass transition temperature Tg (° C.) of the softening agent to be blended is −90 ° C. or more and when the softening agent is not blended, the gas barrier property and the cryogenic temperature are obtained. It can be seen that both performances of crack resistance under the conditions are lowered.

  Moreover, from the results shown in Table 1, it was found that the tire inner liner satisfying the requirements of the present invention is superior to Comparative Examples 1 to 4 in terms of gas barrier properties and crack resistance under cryogenic conditions. .

Claims (14)

  It consists of a resin composition (D) in which a viscoelastic body (C) is dispersed in a resin containing a modified ethylene-vinyl alcohol copolymer (B) obtained by reacting an ethylene-vinyl alcohol copolymer (A). A tire inner liner including at least a layer, wherein 1 to 30% by mass of a softening agent having a glass transition temperature of −90 ° C. or less is blended in the viscoelastic body (C). Inner liner.   The tire inner liner according to claim 1, wherein at least a part of the viscoelastic body (C) has a functional group having a high affinity for a hydroxyl group.   The viscoelastic body (C) is modified with at least one compound selected from the group consisting of maleic acid, maleic anhydride, isocyanate, isothiocyanate, alkoxysilane, epoxy, amine and a compound containing a boron-containing group. The inner liner for tire according to claim 1, wherein at least a part of the viscoelastic body (C) has a boron-containing group.   The modified ethylene-vinyl alcohol copolymer (B) is obtained by reacting 1 to 50 parts by mass of the epoxy compound (E) with 100 parts by mass of the ethylene-vinyl alcohol copolymer (A). The inner liner for tires in any one of Claims 1-3.   The tire inner liner according to any one of claims 1 to 4, wherein the saponification degree of the ethylene-vinyl alcohol copolymer (A) is 90% or more.   The inner liner for tires according to claim 4 whose molecular weight of said epoxy compound (E) is 500 or less.   The tire inner liner according to claim 6, wherein the epoxy compound (E) is glycidol or epoxypropane.   The inner liner for tires in any one of Claims 1-7 whose ethylene content of the said ethylene-vinyl alcohol copolymer (A) is 25-50 mol%.   The inner liner for tires according to any one of claims 1 to 8, wherein a temperature at 12% elongation at break of the resin composition (D) is -55 ° C or lower.   The tire inner liner according to any one of claims 1 to 9, wherein a content of the viscoelastic body (C) in the resin composition (D) is in a range of 10 to 70 mass%.   The tire inner liner according to any one of claims 1 to 10, wherein the viscoelastic body (C) has an average particle size of 5 µm or less.   The innerliner for tire according to any one of claims 1 to 11, wherein a layer made of the resin composition (D) is crosslinked.   A pneumatic tire comprising the tire inner liner according to any one of claims 1 to 12 on an inner surface of a tire inside a carcass.   The pneumatic tire according to claim 13, which is for an aircraft, a truck, or a bus.

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