JP2007008186A - 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 which is excellent in oxygen barrier property and anti-bending property, and to provide the pneumatic tire of which the durability is increased by suppressing the deterioration of a tire internal frame rubber by oxygen permeating from occurring by using the inner liner, and in addition, can suppress the increase of the weight. <P>SOLUTION: This inner liner for the pneumatic tire has a layer having at least one layer which contains a denatured ethylene-vinyl alcohol copolymer (C), and an auxiliary layer (D) containing an elastomer and a sheet-like mineral. In this case, the denatured ethylene-vinyl alcohol copolymer (C) is formed by making 1 to 50 pts.mass of an epoxy compound (B) react to 100 pts.mass of an ethylene-vinyl alcohol copolymer (A) having 25 to 50 mol% of an ethylene unit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inner liner for a pneumatic tire and a pneumatic tire using the inner liner. More specifically, the present invention relates to an inner liner for a pneumatic tire excellent in oxygen permeation resistance and bending resistance, and improves durability by suppressing deterioration due to oxygen permeation from the outside of the tire in use, and also increases weight. The present invention relates to a suppressed pneumatic tire.

It is known that deterioration of tire skeleton rubber, so-called case rubber, is caused by many parts due to oxidation or thermal oxidation due to oxygen permeation from the outside and inside of the tire during use. In order to suppress it, an attempt has been made to use an air barrier layer as an inner liner layer.
Butyl rubber, halogenated butyl rubber, etc. are used as the main raw material for the inner liner as the air barrier layer. However, in the rubber composition containing these, since the air barrier property is low, the thickness of the inner liner is required to be about 1 to 2 mm. In addition to excellent oxygen permeability, it has high flexibility, and with the recent social demands for energy saving, no member has been found that can be made thinner to reduce the weight of automobile tires. This is because.
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 of 1/100 or less of the inner liner rubber composition containing butyl rubber, so that the internal pressure retention can be greatly improved even with a thickness of 50 μm or less. It is possible to reduce the weight. Therefore, in order to improve the air permeability of a pneumatic tire, attempts have been made to use EVOH as a tire inner liner (see, for example, Patent Document 1).

However, this EVOH has a significantly higher elastic modulus than that of rubber usually used in tires, and therefore, breakage or cracks may occur due to deformation during bending. For this reason, for example, when an inner liner made of EVOH is used, the internal pressure retention before use of the tire is greatly improved, but the internal pressure retention of the tire after use subjected to bending deformation during rolling of the tire is higher than that before use. The problem was that it could decrease.
In order to solve this problem, for example, it comprises 60 to 99% by weight of an ethylene-vinyl alcohol copolymer 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. Although an inner liner for an inner surface of a tire using a resin composition has been disclosed (see, for example, Patent Document 2), the bending resistance is not always satisfactory.
Therefore, the present applicant has repeatedly studied a material having higher bending resistance while maintaining gas barrier properties, and previously, 100 parts by mass of an ethylene-vinyl alcohol copolymer having 25 to 50 mol% of ethylene units. On the other hand, it has been found that a modified ethylene-vinyl alcohol copolymer obtained by reacting 1 to 50 parts by mass of an epoxy compound is excellent as an inner liner material (see, for example, Patent Document 3).

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

  Under such circumstances, the present invention is an inner liner for a pneumatic tire excellent in oxygen permeation resistance and bending resistance, and by using the inner liner, deterioration of the tire internal skeleton rubber due to oxygen permeation is suppressed and durability is improved. An object of the present invention is to provide a pneumatic tire capable of improving the weight and suppressing an increase in weight.

As a result of intensive studies to develop a pneumatic tire having the above-mentioned preferable properties, the present inventors, as an inner liner layer, an auxiliary layer containing a specific elastomer and a specific plate mineral and particularly a specific modified ethylene. -It has been found that the object can be effectively achieved by using a multilayer structure having at least a layer containing a vinyl alcohol copolymer.
That is, the present invention
(1) A modified ethylene-vinyl alcohol copolymer obtained by reacting 1 to 50 parts by mass of an epoxy compound (B) with 100 parts by mass of an ethylene-vinyl alcohol copolymer (A) having 25 to 50 mol% of ethylene units. An inner liner for a pneumatic tire, comprising: a layer having at least one layer containing a polymer (C); and an auxiliary layer (D) containing an elastomer and a plate-like mineral;
(2) The pneumatic according to claim 1, further comprising an auxiliary layer (D) containing an elastomer and a plate-like mineral adjacent to a layer having at least one layer containing the modified ethylene-vinyl alcohol copolymer (C). Tire inner liner,
(3) The inner liner for a pneumatic tire according to (1) or (2), wherein the epoxy compound (B) is glycidol or epoxypropane,
(4) The inner for pneumatic tires of (1) to (3) above, wherein the saponification degree of the ethylene-vinyl alcohol copolymer (A) having 25 to 50 mol% of ethylene units used for modification is 90 mol% or more. liner,
(5) The above-mentioned (1) to (4), wherein the layer containing the component (C) is a layer having an oxygen permeation amount of 3 × 10 ⁻¹⁵ cm ³ · cm ² / sec ² · Pa · s or less at 20 ° C. and 65 RH%. Inner liner for pneumatic tires,
(6) The inner liner for a pneumatic tire according to (1) to (5) above, wherein the layer containing the component (C) is a layer formed by crosslinking.
(7) The inner liner for a pneumatic tire according to the above (1) to (6), wherein the layer containing the component (C) is a layer having a thickness of 100 μm or less,

(8) The pneumatic tire according to any one of (1) to (7) above, wherein the layer containing the component (C) is bonded to the auxiliary layer (D) through at least one adhesive layer. For inner liner,
(9) The air of (1) to (8) above, wherein the auxiliary layer (D) is a layer having an oxygen permeation rate of 3 × 10 ⁻¹² cm ³ · cm ² · sec · Pa or less at 20 ° C. and 65 RH%. Inner liner for entering tires.
(10) The inner liner for a pneumatic tire according to the above (1) to (9), wherein the auxiliary layer (D) is a layer containing butyl rubber and / or halogenated butyl rubber,
(11) The inner liner for a pneumatic tire according to the above (1) to (10), wherein the auxiliary layer (D) is a layer containing a diene elastomer.
(12) The inner liner for a pneumatic tire according to (1) to (11), wherein a layer (E) containing a thermoplastic urethane-based elastomer is used between the layer containing the component (C) and the auxiliary layer (D).
(13) The inner liner for a pneumatic tire according to the above (1) to (12), wherein the total thickness of the auxiliary layer (D) is 50 to 1500 μm,

(14) The inner liner for a pneumatic tire according to the above (1) to (13), wherein the aspect ratio of the plate-like mineral of the auxiliary layer (D) is 3 or more and less than 30;
(15) The inner liner for a pneumatic tire according to the above (1) to (14), wherein the plate-like mineral of the auxiliary layer (D) is a composite of hydrous silica and alumina,
(16) The inner liner for a pneumatic tire according to the above (1) to (15), wherein the auxiliary layer (D) comprises carbon black,
(17) The inner liner for a pneumatic tire according to (16), wherein the auxiliary layer (D) includes 10 to 300 parts by mass of a plate-like mineral and 10 to 60 parts by mass of carbon black with respect to 100 parts by mass of the elastomer.
(18) For the pneumatic tire of (16) or (17) above, the iodine adsorption amount of carbon black used in the auxiliary layer (D) is 40 mg / g or less and the dibutyl phthalate oil absorption amount is 100 ml / 100 g or less. Inner liner.
(19) A pneumatic tire characterized by using the inner liner for a pneumatic tire according to the above (1) to (18), and (20) a direction in which the surface of the plate mineral intersects the thickness direction of the inner liner. The pneumatic tire of (19), which is oriented to
Is to provide.

  According to the present invention, by using an inner liner that is excellent in oxygen permeation resistance and bending resistance, deterioration of the tire internal member in use is suppressed by oxygen permeation and durability is improved, and an increase in weight is suppressed. A pneumatic tire can be provided.

Next, the member which comprises the inner liner for pneumatic tires of this invention is demonstrated.
The inner liner for a pneumatic tire of the present invention is obtained by reacting 1 to 50 parts by mass of an epoxy compound (B) with 100 parts by mass of an ethylene-vinyl alcohol copolymer (A) having 25 to 50 mol% of ethylene units. It is necessary to have a layer having at least one layer composed of the obtained modified ethylene-vinyl alcohol copolymer (C) and an auxiliary layer (D) containing an elastomer and a plate-like mineral. By the modification using the epoxy compound (B) in the present invention, the elastic modulus of the unmodified ethylene-vinyl alcohol copolymer (A) can be greatly reduced, and combined with the auxiliary layer (D), oxygen permeation resistance It is possible to improve not only the properties but also the breakability at the time of bending and the degree of occurrence of low temperature cracks.

In the ethylene-vinyl alcohol copolymer (A) used for the modification treatment, the ethylene unit content needs to be 25 to 50 mol%. From the viewpoint of obtaining good flex resistance and fatigue resistance, the ethylene unit content is more preferably 30 mol% or more, and even more preferably 35 mol% or more. From the viewpoint of gas barrier properties, the ethylene unit 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%, gas barrier property may be insufficient.
Further, the saponification degree of the ethylene-vinyl alcohol copolymer is preferably 90 mol% or more, more preferably 95 mol% or more, further preferably 98 mol% or more, and optimally 99 mol%. That's it. If the degree of saponification is less than 90 mol%, the gas barrier properties and the thermal stability during production of the laminate may be insufficient.

The preferred melt flow rate (MFR) (under 190 ° C. and 21.18 N load) of the ethylene-vinyl alcohol copolymer (A) used in the modification treatment 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 is around 190 ° C. or exceeds 190 ° C., it is measured under a load of 21.18 N at a plurality of temperatures equal to or higher than the melting point. The logarithm of MFR is plotted on the vertical axis and expressed as a value extrapolated to 190 ° C.
The modification treatment requires 1 to 50 parts by mass, preferably 2 to 40 parts by mass, more preferably 5 to 5 parts by mass of the epoxy compound (B) with respect to 100 parts by mass of the unmodified ethylene-vinyl alcohol copolymer. It can carry out by making 35 mass parts react. In this case, it is advantageous to carry out the reaction in a solution using a suitable solvent.

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

The epoxy compound (B) used for the modification treatment is not particularly limited, but is preferably a monovalent epoxy compound. When the epoxy compound is divalent or higher, a cross-linking reaction with the ethylene-vinyl alcohol copolymer may occur, and the quality of the laminate may be deteriorated due to the generation of gels and blisters. 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) (under 190 ° C. and 21.18 N load) 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 resistance to resistance. From the viewpoint of obtaining fatigue, 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. preferable. However, when the melting point of the modified EVOH is around 190 ° C or exceeds 190 ° C, it is measured at multiple temperatures above the melting point under a load of 21.18N, and the inverse of absolute temperature is plotted on the horizontal axis and the logarithm of MFR is plotted on the vertical axis. Plotted on the axis, expressed as extrapolated to 190 ° C

The oxygen permeation amount at 20 ° C. and 65 RH% of the film layer made of the modified ethylene-vinyl alcohol copolymer (C) used for the member constituting the inner liner for the pneumatic tire is 3 × 10 ⁻¹⁵ cm ^3. - preferably cm / cm at ² · sec · Pa or less, 7 × 10 ^-16 cm more preferably ^{3 · cm / cm 2 · sec} · Pa or ^{less, 3 × 10 -16 cm 3 ·} cm / More preferably, it is not more than cm ² · sec · Pa.
In order to use it as a member constituting the inner liner for a pneumatic tire, the modified ethylene-vinyl alcohol copolymer (C) is usually formed into a film, a sheet or the like by melt molding. Examples of the melt molding method include a T-die method and an inflation method. The melting temperature at this time varies depending on the melting point of the copolymer, but is preferably about 150 to 170 ° C.

In the member constituting the inner liner for a pneumatic tire, the layer made of the modified ethylene-vinyl alcohol copolymer (C) is preferably cross-linked. When the copolymer layer is not cross-linked, the modified ethylene-vinyl alcohol copolymer layer is significantly deformed in the vulcanization process for producing a pneumatic tire, so that the uniform layer cannot be maintained, and air blocking is performed. The gas barrier properties, flex resistance, fatigue resistance, etc. of the layer may be deteriorated.
Although there is no restriction | limiting in particular about the method of bridge | crosslinking a modified ethylene-vinyl alcohol copolymer (C) layer, The method of irradiating an energy beam to this copolymer layer is mentioned as a preferable method.
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 film or sheet formed from the copolymer into an electron beam irradiation apparatus and irradiating the electron beam can be mentioned. Although it does not specifically limit regarding the dose of an electron beam, Preferably it exists in the range of 10-60 Mrad. When the electron dose to irradiate is lower than 10 Mrad, it becomes difficult to crosslink. On the other hand, when the electron dose to be irradiated exceeds 60 Mrad, the deterioration of the film and the sheet easily proceeds. More preferably, the electron dose range is 20 to 50 Mrad.

The member constituting the inner liner for a pneumatic tire needs to have a multilayer structure of the modified ethylene-vinyl alcohol copolymer (C) layer and an auxiliary layer (D) containing an elastomer and a plate-like mineral. .
The modified ethylene-vinyl alcohol copolymer (C) layer and the auxiliary layer (D) containing an elastomer and a plate-like mineral are preferably adjacent to each other.
The elastomer component constituting the auxiliary layer (D) is preferably a layer containing butyl rubber and / or halogenated rubber in order to obtain desired air permeation resistance and flex resistance. For example, in addition to the butyl rubber, there may be mentioned halogenated butyl rubber such as brominated butyl rubber, brominated isobutylene / paramethylstyrene copolymer, chlorinated butyl rubber, etc., particularly from the viewpoint of obtaining a sufficient vulcanization rate. It is preferable to use a butyl rubber.
In addition, from the viewpoint of suppressing the occurrence of cracks in the auxiliary layer (D) and the extension of the cracks after the occurrence of cracks, a composition containing butyl rubber and / or halogenated butyl rubber and a diene rubber as an elastomer component is used. It is preferable to use it.
The diene rubber is not particularly limited and may be appropriately selected from known ones according to the purpose. Examples thereof include natural rubber, epoxidized natural rubber, styrene-butadiene copolymer, and styrene-isoprene copolymer. Examples thereof include coalescence, polyisoprene, and polybutadiene. These may be used individually by 1 type and may use 2 or more types together. Among these diene rubbers, natural rubber and / or polybutadiene rubber are preferable because they are excellent in low-temperature characteristics such as crack resistance at low temperatures.
The blending ratio of the diene rubber to the butyl rubber and / or the halogenated butyl rubber is not particularly limited, but may be appropriately determined depending on the tire size, the tire use conditions, etc. to which the inner liner of the present invention is applied.
For example, when the inner liner is applied to tires for heavy-duty vehicles that can be used under cryogenic conditions such as aircraft, trucks, buses, etc., in order to suppress the occurrence of low-temperature cracks, the blending ratio of the diene rubber is set to It is preferable to increase.

Moreover, it is necessary to contain a plate-like mineral as an essential component which comprises an auxiliary layer (D). The plate-like mineral is not particularly limited as long as the shape is plate-like and flat, and can be appropriately selected according to the purpose. The plate-like mineral includes layered minerals and the like. Specific examples of the plate mineral include mica, clay, silica, alumina, and composites thereof. Among these, at least one selected from kaolin clay or a composite of hydrous silica and alumina is preferable. These may be used individually by 1 type, may use 2 or more types together, and can use a commercial item suitably.
Furthermore, the aspect ratio of the plate mineral is preferably 3 or more and less than 30 and more preferably 8-20. The aspect ratio means the ratio of the major axis to the thickness of the plate mineral. When the aspect ratio is within the above numerical range, the auxiliary layer (D) is excellent in air permeation resistance and flex resistance, can be made thin gauge, excellent in workability, and unvulcanized sheets are cut and perforated. This is advantageous in that it does not occur.
Moreover, since the average particle diameter of a plate-like mineral will cause a fall of bending resistance when it is too large, it is preferable to set it as 10 micrometers or less, and the range of about 0.2-5 micrometers is especially more preferable.

10-300 mass parts is preferable with respect to 100 mass parts of said elastomer components, and, as for content of the plate-shaped mineral in auxiliary layer (D), 20-80 mass parts is more preferable. When the content of the plate mineral is in the numerical range, the auxiliary layer (D) has excellent air permeation resistance and flex resistance, sufficient internal pressure retention, can be made thinner, and can be processed. It is advantageous in that it is excellent and does not cause unvulcanized sheet breakage or perforation. Moreover, the bending resistance of the auxiliary layer (D) can be further improved by adjusting the amount of the plate mineral to the more preferable range.
In addition, when diene rubber is blended as an elastomer component as described above, it may be determined as appropriate depending on the blending amount of diene rubber with respect to butyl rubber and / or halogenated butyl rubber, but the auxiliary layer (D) is resistant to air permeation. In order to ensure the property, it is preferable to contain 80 parts by mass or more of a plate-like mineral with respect to 100 parts by mass of the elastomer component.

Further, carbon black is blended in the auxiliary layer (D) as a reinforcing filler. Examples of preferable carbon black include N660, N772, N762, and N754. Carbon black preferably has the following colloidal characteristics. That is, the iodine adsorption amount (IA) is preferably 40 mg / g or less, and more preferably about 35 to 20 mg / g. The dibutyl phthalate oil absorption (DBP) is preferably 100 ml / 100 g or less, more preferably about 70 to 30 ml / 100 g. Here, IA of the colloidal characteristic is a value measured according to ASTM D1510-95, and DBP is a value measured according to ASTM D2414-97.
10-60 mass parts is preferable with respect to 100 mass parts of elastomer components, and, as for the compounding quantity of the said carbon black, 30-50 mass parts is more preferable. When the blending amount of the carbon black satisfies the above range, sufficient unvulcanized strength of the rubber can be obtained, and excellent bending resistance and low temperature can be obtained without causing production problems such as sheet breakage and rubber adhesion. be able to.
As the elastomer component of the auxiliary layer (D), components usually used in the rubber composition for an inner liner, if necessary, such as a vulcanizing agent, a vulcanization accelerator, a vulcanization retarder, an anti-aging agent, an oxidation agent, and the like. Inhibitors, softeners, lubricants, vulcanization aids, tackifiers and the like can be appropriately blended.
For example, the above components can be produced by kneading by a conventional method with a Banbury mixer.
In order to make the kneaded composition into a sheet-like auxiliary layer (D), for example, a calender roll can be used.

Moreover, in this invention, the thing formed by bonding a modified | denatured ethylene-vinyl alcohol copolymer (C) layer and an auxiliary | assistant layer (D) through the adhesive layer of at least 1 layer or more can be mentioned. .
Since the ethylene-vinyl alcohol copolymer has an —OH group, it is relatively easy to ensure adhesion with 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, c is a modified ethylene-vinyl alcohol copolymer layer, D1 and D2 are rubbery elastic layers (D1 and D2 are different layers, respectively), and cd is an adhesive layer. For example, c / D1, D1 / c / D1, c / cd / D1, D1 / cd / c / cd / D1, D1 / c / D1 / D2, D1 / c / D1 / cd / D2, etc. It can be mentioned, but is not limited to these.

Moreover, each layer may be a single layer or may be a multilayer depending on the case. Further, when there are a plurality of modified ethylene-vinyl alcohol copolymer (C) layers, auxiliary layers (D), and adhesive layers, the plurality of modified ethylene-vinyl alcohol copolymer (C) layers may be the same. The plurality of auxiliary layers (D) may be the same or different, and the plurality of adhesive layers may be the same or different.
The method for producing the multilayer structure is not particularly limited. For example, the auxiliary layer (D) and the adhesive layer are melt-extruded into a molded product (film, sheet, etc.) made of the modified ethylene-vinyl alcohol copolymer (C). Method, conversely, a method in which the modified ethylene-vinyl alcohol copolymer (C) and the adhesive layer are melt extruded onto the base material of the auxiliary layer (D), the modified ethylene-vinyl alcohol copolymer (C) and the auxiliary layer (D ) (And an adhesive layer as necessary), a molded product obtained from the modified ethylene-vinyl alcohol copolymer (C), and the auxiliary layer (D) film and sheet. A method of laminating using a layer, and further, a film obtained from a modified ethylene-vinyl alcohol copolymer (C) and a film of an auxiliary layer (D), a sheet (and The method and the like to bond the adhesive layer) in accordance with the requirements.

In the member constituting the inner liner for a pneumatic tire, the thickness of the modified ethylene-vinyl alcohol copolymer layer is preferably 100 μm or less. When it exceeds 100 μm, the merit of weight reduction is less than that of the inner liner using butyl rubber, halogenated butyl rubber or the like currently used. In light of gas barrier properties, flex resistance, and fatigue resistance, the thickness of the modified ethylene-vinyl alcohol copolymer layer is more preferably 2 to 80 μm, and even more preferably 10 to 60 μm.
In addition, about preferable thickness, it can determine suitably according to the tire size applied.
In the modified ethylene-vinyl alcohol copolymer layer in the multilayer structure described above, use at a thickness of 100 μm or less improves 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 layer using the modified ethylene-vinyl alcohol copolymer (C) as a raw material has good adhesion to the auxiliary layer (D), so it is difficult to peel off and cracks are difficult to extend. Large breaks and cracks do not occur. In addition, even when breaks or cracks occur, the rubber-like elastic layer supplements the gas barrier properties of the breaks and cracks generated in the modified ethylene-vinyl alcohol copolymer (C) layer, thereby suppressing oxygen permeation. Can do.

The auxiliary layer (D) in the member constituting the inner liner for a pneumatic tire has an oxygen permeation amount of 3 × 10 ⁻¹² cm ³ · cm ² · sec · Pa or less at 20 ° C. and 65 RH%. From the viewpoint of gas barrier properties, it is preferable. More preferably, it is 7 × 10 ⁻¹³ cm ³ · cm / cm ² · sec · Pa or less.

Furthermore, in the present invention, the thinning of the auxiliary layer (D) and the generation and extension of cracks between the layer containing the modified ethylene-vinyl alcohol copolymer (C) and the auxiliary layer (D) as desired. From the viewpoint of suppression, it is preferable to provide a layer (E) containing a thermoplastic urethane elastomer. The thickness of the (E) layer is preferably 5 to 100 μm.
In the inner liner for a pneumatic tire of the present invention, a layer containing a modified ethylene-vinyl alcohol copolymer (C) as a main component, a multilayered auxiliary layer (D), and a layer containing a thermoplastic urethane-based elastomer (E) It is more preferable to laminate.
The thermoplastic urethane-based elastomer (hereinafter sometimes abbreviated as TPU) is an elastomer having a urethane group (—NH—COO—) in the molecule, and includes (1) a polyol (long chain diol), (2 It is produced by a three-component intermolecular reaction of a) diisocyanate and (3) a short-chain diol. The polyol and the short chain diol undergo an addition reaction with diisocyanate to produce a linear polyurethane. Among these, the polyol becomes a flexible portion (soft segment) of the elastomer, and the diisocyanate and the short-chain diol become a hard portion (hard segment). The properties of TPU depend on the properties of raw materials, polymerization conditions, and blending ratio, and among these, the type of polyol greatly affects the properties of TPU. Many of the basic properties are determined by the type of long chain diol, but the hardness is adjusted by the proportion of hard segments.
The types are (i) caprolactone type (polylactone ester polyol obtained by ring-opening caprolactone), (b) adipic acid type (= adipate type) <adipic acid ester polyol of adipic acid and glycol>, (ha ) PTMG (polytetramethylene glycol) type (= ether type) <polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran>.

  The total thickness of the auxiliary layers (D) in the member constituting the inner liner is preferably in the range of 50 to 1500 μm. If the total thickness 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 cracks, and the cracks are easily extended. On the other hand, when the total thickness exceeds 1500 μm, the merit of weight reduction with respect to the currently used pneumatic tire is reduced. From the viewpoint of gas barrier properties, flex resistance, fatigue resistance of the air barrier layer and weight reduction of the pneumatic tire, the total thickness of the rubber-like elastic layer is more preferably 100 to 1000 μm, and further preferably 300 to 800 μm. . In addition, about preferable thickness of an auxiliary | assistant layer (D), it can determine suitably within the said range according to the tire size applied.

Here, the plate-like mineral action contained in the auxiliary layer (D) will be described in detail with reference to FIG.
FIG. 1 is a drawing schematically illustrating a partial cross section of an inner liner of a tire to which an inner liner of the present invention is applied. 1 is an inner liner, 2 is an auxiliary layer (D), 3 is a plate mineral, and 4 is a layer containing a modified ethylene-vinyl alcohol copolymer (C).
The arrow indicates the flow of air from the inside of the tire to the carcass layer (air leakage). The air inside the tire first passes through the layer 4 containing the component (C), but the layer 4 containing the component (C) is resistant to the air. It has excellent air permeability and has an air permeation amount of 1/100 or less of an inner liner using ordinary butyl rubber, and the air permeation resistance is greatly improved by the layer 4 containing the component (C). Next, the air passes through the auxiliary layer (D) 2. The plate-like mineral particles 3 dispersed in the auxiliary layer (D) 2 have a direction in which the surface intersects the thickness direction of the auxiliary layer (D) 2 (that is, a direction parallel or nearly parallel to the surface of the auxiliary layer D2). Oriented. The state where the detour is forced by the presence of the plate-like mineral particles 3 and the distance to pass through the auxiliary layer (D) 2 is increased. Thus, in the inner liner of the present invention, as a result of the plate-like mineral particles 3 blended in the elastomer component of the auxiliary layer (D) 2 constituting the inner liner being oriented in a certain direction, further from the inside of the tire. By preventing the passage of air and making the inner liner 1 a multilayer structure of the layer 4 containing the component (C) and the auxiliary layer (D) 2, it is considered that a very low air permeability that has not been achieved in the past is achieved. However, using a plate-like mineral with a large aspect ratio, such as clay that has been used for rubber for inner liners in the past, makes it difficult to uniformly disperse when kneading the rubber, resulting in agglomeration in the vulcanized rubber, resulting in agglomeration. Clay becomes a fracture nucleus, which causes a decrease in the bending resistance and low-temperature properties of the auxiliary layer (D) 2 and impairs the durability of the entire tire.
In the present invention, a plate-like mineral 3 having a specific aspect ratio of 3 to less than 30 is selected and adjusted to a certain blending amount together with carbon black as a reinforcing filler to be used in bending resistance and low temperature. It is possible to significantly reduce the air permeability without impairing the performance, and to provide a pneumatic tire that suppresses deterioration due to oxygen permeation of the tire inner member to improve durability and suppress weight increase. it can.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, the characteristic value of the ethylene-vinyl alcohol copolymer used for modification | denaturation was measured in accordance with the method shown below.
(1) Ethylene unit content and degree of saponification Obtained by ¹ H-NMR (nuclear magnetic resonance) measurement (using “JNM-GX-500 type” manufactured by JEOL Ltd.) using deuterated dimethyl sulfoxide as a solvent. Calculated from the spectrum.
(2) Melt flow rate After the ethylene-vinyl alcohol copolymer used as a sample is filled in a cylinder having an inner diameter of 9.65 mm and a length of 162 mm of a melt indexer L244 (manufactured by Takara Kogyo Co., Ltd.), and melted at 190 ° C. The load was evenly applied using a plunger with a load of 21.18 N and a diameter of 9.48 mm.
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 is around 190 ° C. or exceeds 190 ° C., it is measured under a load of 21.18 N at a plurality of temperatures equal to or higher than the melting point. The logarithm of MFR is plotted on the vertical axis and expressed as a value extrapolated to 190 ° C.

Production Example 1 Production of Modified Ethylene-Vinyl Alcohol Copolymer I An ethylene-vinyl alcohol copolymer (MFR: 5.5 g / m) having an ethylene unit content of 44 mol% and a saponification degree of 99.9 mol% was placed in a pressurized reaction vessel. Charge 10 parts (at 190 ° C. under 21.18 N load) and 8 parts by weight of N-methyl-2-pyrrolidone, and heat and stir at 120 ° C. for 2 hours to complete the ethylene-vinyl alcohol copolymer. After adding 0.4 parts by mass of glycidol as an epoxy compound, the mixture was heated at 160 ° C. for 4 hours.
After the heating, it was precipitated in 100 parts by mass of distilled water, and N-methyl-2-pyrrolidone and unreacted glycidol were sufficiently washed with a large amount of distilled water to obtain a modified ethylene-vinyl alcohol copolymer. Further, the resulting modified ethylene-vinyl alcohol copolymer was fined to a particle size of about 2 mm with a pulverizer, and then sufficiently washed with a large amount of distilled water again. The washed particles were vacuum-dried at room temperature for 8 hours, and then melted at 200 ° C. using a twin-screw extruder and pelletized.

Production Example 2 Production of Modified Ethylene-Vinyl Alcohol Copolymer II An ethylene-vinyl alcohol copolymer (MFR: 5.5 g / m) having an ethylene unit content of 44 mol% and a saponification degree of 99.9 mol% was placed in a pressurized reaction vessel. Charge 10 parts (at 190 ° C. under 21.18 N load) and 8 parts by weight of N-methyl-2-pyrrolidone, and heat and stir at 120 ° C. for 2 hours to complete the ethylene-vinyl alcohol copolymer. After adding 0.3 part by mass of glycidol as an epoxy compound, the mixture was heated at 160 ° C. for 4 hours.
After the heating, it was precipitated in 100 parts by mass of distilled water, and N-methyl-2-pyrrolidone and unreacted glycidol were sufficiently washed with a large amount of distilled water to obtain a modified ethylene-vinyl alcohol copolymer. Further, the resulting modified ethylene-vinyl alcohol copolymer was fined to a particle size of about 2 mm with a pulverizer, and then sufficiently washed with a large amount of distilled water again. The washed particles were vacuum-dried at room temperature for 8 hours, and then melted at 200 ° C. using a twin-screw extruder and pelletized.

Production Example 3 Production of Modified Ethylene-Vinyl Alcohol Copolymer III An ethylene-vinyl alcohol copolymer (MFR: 5.5 g / m) having an ethylene unit content of 44 mol% and a saponification degree of 99.9 mol% was placed in a pressurized reaction vessel. Charge 10 parts (at 190 ° C. under 21.18 N load) and 8 parts by weight of N-methyl-2-pyrrolidone, and heat and stir at 120 ° C. for 2 hours to complete the ethylene-vinyl alcohol copolymer. After adding 0.4 parts by mass of epoxypropane as an epoxy compound, the mixture was heated at 160 ° C. for 4 hours.
After the heating, it was precipitated in 100 parts by mass of distilled water, and N-methyl-2-pyrrolidone and unreacted epoxypropane were sufficiently washed with a large amount of distilled water to obtain a modified ethylene-vinyl alcohol copolymer. Further, the resulting modified ethylene-vinyl alcohol copolymer was fined to a particle size of about 2 mm with a pulverizer, and then sufficiently washed with a large amount of distilled water again. The washed particles were vacuum-dried at room temperature for 8 hours, and then melted at 200 ° C. using a twin-screw extruder and pelletized.

Production Example 4 Production of Film 1 Using pellets of the modified ethylene-vinyl alcohol copolymer I obtained in Production Example 1, a 40 mmφ extruder (PLABOR GT-40-A manufactured by Plastics Engineering Laboratory) and a T-die are used. Using a film forming machine, a film was formed under the following extrusion conditions to obtain a single-layer film 1 having a thickness of 20 μm.
Type: Single screw extruder (non-vent type); L / D: 24; Diameter: 40 mmφ; Screw: Single-flight full flight type, surface copper nitride; Screw rotation speed: 40 rpm; Die: 550 mm wide coat hanger die; Lip gap: 0.3 mm; cylinder, die temperature setting: C1 / C2 / C3 / adapter / die = 180/200/210/210/210 (° C.)

Production Examples 5 and 6 Production of Film 2 and Film 3 Except that the pellets of modified ethylene-vinyl alcohol copolymers II and III obtained in Production Example 2 and Production Example 3 were used, the same as Production Example 4, Single-layer films 2 and 3 each having a thickness of 20 μm were prepared.
Production Example 7 Production of Film 4 for Gas Barrier Material Ethylene having an unmodified ethylene content of 44 mol%, a saponification degree of 99.9 mol%, and MFR = 5.5 g / 10 min (under 190 ° C. and 21.18 N load) A monolayer film 4 having a thickness of 20 μm for a gas barrier material was obtained in the same manner as in Production Example 4 except that a vinyl alcohol copolymer was used instead of the modified ethylene-vinyl alcohol copolymer I.

Production Example 8 Production of three-layer film 5 Using the modified ethylene-vinyl alcohol copolymer III (modified EVOH III) obtained in Production Example 3 and thermoplastic polyurethane (Kuraray Co., Ltd. Kuramylon 3190) as an elastomer, 2 A three-layer film 5 (thermoplastic polyurethane layer / modified EVOH III layer / thermoplastic polyurethane layer) was produced under the following co-extrusion molding conditions using a seed three-layer coextrusion apparatus. The thickness of each layer is 20 μm for both the modified EVOH III layer and the thermoplastic polyurethane layer.
<Co-extrusion molding conditions>
Layer structure: thermoplastic polyurethane / modified EVOH III / thermoplastic polyurethane (thickness 20/20/20: unit is μm); extrusion temperature of each resin: C1 / C2 / C3 / die = 170/170/220/220 ° C .; Resin extruder specifications: 25 mmφ extruder for thermoplastic polyurethane P25-18AC (Osaka Seiki Machine Co., Ltd.), 20 mmφ extruder for modified EVOHIII Lab machine ME type CO-EXT (Toyo Seiki Co., Ltd.); T die specification: 500 mm width for 2 types and 3 layers (Plastics Engineering Laboratory Co., Ltd.); cooling roll temperature: 50 ° C .; take-off speed: 4 m / min

Test example 1
About the film 1-the film 5 produced in manufacture example 4-manufacture example 8, according to the following method, oxygen permeation amount and bending resistance were evaluated.
(1) Measurement of oxygen permeation amount Each produced film was conditioned at 20 ° C.-65% RH for 5 days.
The method described in JIS K7126 (isobaric method) using the MOCON OX-TRAN 2/20 model manufactured by Modern Control Co., Ltd. under the conditions of 20 ° C. and 65% RH using the two samples of each humidity-controlled film. The oxygen permeation amount was measured and the average value was obtained.
(2) Evaluation of Bending Resistance For each film, 50 sheets cut to 21 cm × 30 cm were prepared, and each film was conditioned at 20 ° C.-65% RH for 5 days, and then ASTM F 392-74. According to the same standards, a gelbo flex tester manufactured by Rigaku Kogyo Co., Ltd. was used, and the number of flexing was 50, 75, 100, 125, 150, 175, 200, 225, 250, 300, 400. After being bent 500 times, 600 times, 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 pinholes. 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, and obtaining 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 pinhole was observed after 1500 times of bending, the number of times of bending was increased every 500 times, and the number of times of bending where a pinhole was seen was defined as Np1.

The oxygen permeation amount of the film 1 was 2.6 × 10 ⁻¹⁶ cm ³ · cm / cm ² · sec · Pa, and an excellent gas barrier property was exhibited.
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 0.75 × 10 ⁻¹⁶ cm ³ · cm ² / cm ² · sec · Pa, and showed excellent gas barrier properties.
Further, 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 transmission rate of the film 3 is ^{3.0 × 10 -16 cm 3 · cm} / cm 2 · sec · Pa, exhibited excellent gas barrier properties.
Further, when the bending resistance of the film 3 was evaluated according to the above-mentioned method, Np1 was 500 times, indicating extremely excellent bending resistance.
The oxygen permeation amount of the film 4 was 3.5 × 10 ⁻¹⁷ cm ³ · cm ² · sec · Pa, and the gas barrier property was excellent.
Further, 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 2.6 × 10 ⁻¹⁶ cm ³ · cm / cm ² · sec · Pa, and an excellent gas barrier property was exhibited.
Further, when the bending resistance of the film 5 was evaluated according to the above method, Np1 was 5000 times, indicating extremely excellent bending resistance.

Production Example 9, Production of Auxiliary Layer (D) The composition shown in Table 1 contains an elastomer and a plate mineral by kneading with a Banbury mixer by a conventional method and forming the unvulcanized rubber into a sheet with a roll. An auxiliary layer (D) was produced. The unvulcanized sheet was vulcanized at 150 ° C. for 30 minutes in order to measure the oxygen transmission rate. Table 1 shows the oxygen permeation value.

[note]
* 1. Brominated butyl: Product name Bromobutyl 2244 manufactured by JSR
* 2. Carbon black: GPF Asahi Carbon Co., Ltd. Product name # 55
* 3. Plate mineral: Clay M. Product name POLYFIL DL (aspect ratio 10) manufactured by Huber
* 4. Process oil: Nippon Sun Oil Co., Ltd. Trade name SUNPAR2280
* 5. Zinc flower: Hakusui Chemical Co., Ltd. * 6. Vulcanization accelerator: Product name NOCCELER DM
* 7. Stearic acid: Asahi Denka Kogyo * 8. Sulfur: Made by Karuizawa Refinery

Examples 1-6
Using the types of films shown in Table 2, using an electron beam irradiation device “Curetron EBC200 / 100 for production” manufactured by Nissin High Voltage Co., Ltd. for each film, under conditions of an acceleration voltage of 200 kV and an irradiation energy of 30 Mrad It was irradiated with electrons and subjected to crosslinking treatment. To one side of the obtained crosslinked film, “Metaloc R30M” manufactured by Toyo Chemical Laboratory was applied as an adhesive layer, and the produced sheet-like unvulcanized auxiliary layer was laminated in the form shown in Table 2, and then 150 A composite sample was prepared by vulcanization at 30 ° C. for 30 minutes, and the amount of oxygen permeation and bending resistance were measured.
The amount of oxygen permeation was measured based on the above-described measurement method, and is expressed as an index in Table 2 with Comparative Example 1 being 100. The smaller the value of the index, the better the resistance to oxygen permeation (the more difficult it is for oxygen to permeate). The results are shown in Table 2.
Regarding the bending resistance, a rubber test piece was prepared in accordance with a bending test method of JIS K6301-1995, and a bending test was performed. The time until a 10 mm crack was generated on the test piece was measured, and Comparative Example 1 was taken as 100, and the time until the crack of each test piece was generated by 10 mm was expressed as an index. The larger the index, the better the flex resistance. The results are shown in Table 2.

Comparative Examples 1-3
Examples 1 to 6 except that the films were not laminated in Examples 1 to 6
It carried out like. The results are shown in Table 2.

Comparative Example 4
It implemented like Example 1-6 except having used the film 4 in Examples 1-6. The results are shown in Table 2.

Test example 2
Pneumatic tires for passenger cars (195 / 65R15) were produced by a conventional method using the inner liners of Examples 1 to 6 and Comparative Examples 1 to 4. FIG. 2 shows a schematic cross-sectional view of the manufactured tire. In the figure, 4 represents a layer containing a modified ethylene-vinyl alcohol copolymer (C), and 2 represents an auxiliary layer (D) containing an elastomer and a plate-like mineral.
About the tire produced above, it was pressed with a load of 6 kN onto a drum having a rotational speed corresponding to a speed of 80 km / h at an air pressure of 140 kPa, and traveled 10,000 km. Using a non-running tire and a tire running under the above conditions, the internal pressure retention was evaluated under the following conditions. 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 indexed by the following formula.
Internal pressure retention = ((240−b) / (240−a)) × 100
In the formula, a and b represent a: the internal pressure after 3 months of the test tire b: the internal pressure after 3 months of the non-running tire (pneumatic tire using a normal rubber inner liner) described in Comparative Example 1 below. .
The appearance of the inner liner of the tire after running the drum was visually observed to evaluate the presence or absence of cracks. The evaluation results are shown in Table 2.

  According to the present invention, by using an inner liner that is excellent in oxygen permeation resistance and bending resistance, deterioration of the tire internal member in use is suppressed by oxygen permeation and durability is improved, and an increase in weight is suppressed. A pneumatic tire can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a drawing schematically illustrating a partial cross section of an inner liner of a tire to which an inner liner of the present invention is applied. 1 is a cross-sectional view of a tire showing an example of an embodiment of the present invention.

Explanation of symbols

1. Inner liner2. Auxiliary layer (D)
3. Plate mineral 4 Layer containing modified ethylene-vinyl alcohol copolymer (C)

Claims (20)

  A modified ethylene-vinyl alcohol copolymer obtained by reacting 1 to 50 parts by mass of an epoxy compound (B) with 100 parts by mass of an ethylene-vinyl alcohol copolymer (A) having 25 to 50 mol% of ethylene units ( An inner liner for a pneumatic tire comprising a layer having at least one layer containing C) and an auxiliary layer (D) containing an elastomer and a plate-like mineral.   2. The inner for a pneumatic tire according to claim 1, further comprising an auxiliary layer (D) containing an elastomer and a plate-like mineral adjacent to a layer having at least one layer containing the modified ethylene-vinyl alcohol copolymer (C). liner.   The inner liner for a pneumatic tire according to claim 1 or 2, wherein the epoxy compound (B) is glycidol or epoxypropane.   The inner liner for a pneumatic tire according to any one of claims 1 to 3, wherein the ethylene-vinyl alcohol copolymer (A) having 25 to 50 mol% of ethylene units used for modification has a saponification degree of 90 mol% or more. . The layer containing the component (C) is a layer having an oxygen permeation amount of 3 x 10 ^-15 cm ³ · cm ² · sec · Pa or less at 20 ° C and 65 RH%. Inner liner for pneumatic tires.   The inner liner for a pneumatic tire according to any one of claims 1 to 5, wherein the layer containing the component (C) is a layer formed by crosslinking.   The inner liner for a pneumatic tire according to claim 1, wherein the layer containing the component (C) is a layer having a thickness of 100 μm or less.   The inner liner for a pneumatic tire according to claim 1, comprising a layer containing the component (C) bonded to the auxiliary layer (D) via at least one adhesive layer. The air according to any one of claims 1 to 8, wherein the auxiliary layer (D) is a layer having an oxygen permeation amount of 3 x 10 ^-12 cm ³ · cm ² · sec · Pa or less at 20 ° C and 65 RH%. Inner liner for entering tires.   The inner liner for a pneumatic tire according to any one of claims 1 to 9, wherein the auxiliary layer (D) is a layer containing butyl rubber and / or halogenated butyl rubber.   The inner liner for a pneumatic tire according to any one of claims 1 to 10, wherein the auxiliary layer (D) is a layer containing a diene elastomer.   The inner liner for a pneumatic tire according to any one of claims 1 to 11, wherein a layer (E) containing a thermoplastic urethane-based elastomer is used between the layer containing the component (C) and the auxiliary layer (D).   The inner liner for a pneumatic tire according to any one of claims 1 to 12, wherein the total thickness of the auxiliary layer (D) is 50 to 1500 µm.   The inner liner for a pneumatic tire according to any one of claims 1 to 13, wherein the aspect ratio of the plate-like mineral of the auxiliary layer (D) is 3 or more and less than 30.   The inner liner for a pneumatic tire according to any one of claims 1 to 14, wherein the plate-like mineral of the auxiliary layer (D) is a composite of hydrous silica and alumina.   The inner liner for a pneumatic tire according to any one of claims 1 to 15, wherein the auxiliary layer (D) comprises carbon black.   The inner liner for a pneumatic tire according to claim 16, wherein the auxiliary layer (D) comprises 10 to 300 parts by mass of a plate-like mineral and 10 to 60 parts by mass of carbon black with respect to 100 parts by mass of the elastomer.   The inner liner for a pneumatic tire according to claim 16 or 17, wherein the carbon black used in the auxiliary layer (D) has an iodine adsorption of 40 mg / g or less and a dibutyl phthalate oil absorption of 100 ml / 100 g or less.   A pneumatic tire using the inner liner for a pneumatic tire according to any one of claims 1 to 18.   The pneumatic tire according to claim 19, wherein the surface of the plate-like mineral is oriented in a direction intersecting with the thickness direction of the inner liner.

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