JP2012254575A - Method for producing pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a pneumatic tire, which discharges gas between a bladder and an inner surface of the tire without damaging an inner liner, and exhibits excellent performance in air-in, flex-crack-resistance adjustment, rolling resistance, and drivability, in a tire vulcanization process.SOLUTION: In the method for producing the pneumatic tire, a tire vulcanization bladder with a plurality of vent lines is used. The pneumatic tire includes the inner liner on the inner surface. The inner liner includes a first layer containing a styrene-isobutylene-styrene triblock copolymer. The vent lines include: a first vent line at a part corresponding to a part from a tire bead toe to a tire buttress; and a second vent line at a part corresponding to a part from the tire buttress to a tire crown.

Description

  The present invention relates to a pneumatic tire manufactured using a tire vulcanizing bladder.

  In recent years, tires have been reduced in weight due to a strong social demand for lower fuel consumption of vehicles. In the inner liner with a function to improve air permeation resistance by reducing the amount of air leakage (air permeation amount) from the inside of the pneumatic tire to the outside among the tire members inside the tire radial direction However, weight reduction has come to be done.

  At present, as a rubber composition for an inner liner, the use of a butyl rubber containing 70 to 100% by mass of butyl rubber and 30 to 0% by mass of natural rubber improves the air permeation resistance of the tire. . In addition to butylene, the butyl rubber contains about 1% by mass of isoprene, which, together with sulfur, vulcanization accelerator, and zinc white, enables co-crosslinking with adjacent rubber. When the butyl rubber is used for the inner liner, a thickness of about 0.6 to 1.0 mm for passenger car tires and about 1.0 to 2.0 mm for truck / bus tires is required in normal blending.

  Therefore, in order to reduce the weight of the tire, there has been proposed a polymer that has better air permeability than butyl rubber and can reduce the thickness of the inner liner layer. As such polymer candidates, thermoplastic resin compositions have been studied.

  By the way, in the conventional vulcanization process of a pneumatic tire, the metal mold | die in which the bladder which consists of an expandable elastic body was accommodated is used. In the vulcanization step, first, a release agent is applied to the inner surface of the preformed unvulcanized tire. Next, an unvulcanized tire is inserted into the heated mold, and then gas is filled into the bladder. When the bladder is filled with gas, the bladder expands while sliding on the inner surface of the unvulcanized tire. Next, the mold is tightened and the bladder internal pressure is increased. The unvulcanized tire is pressurized by a heated mold and a bladder expanded by high-pressure gas filling, and is heated by heat conduction from the mold and the bladder. The rubber causes a vulcanization reaction by pressurization and heating, and a vulcanized tire is obtained.

  The bladder pressurizes the unvulcanized tire from the inside during expansion, and discharges the gas existing between the unvulcanized tire and the bladder. If the gas is trapped between the tire inner surface and the bladder without being discharged, the gas remains on the tire inner surface and air-in occurs. Further, residual gas causes poor vulcanization and tire failure. Therefore, in order to facilitate the discharge of gas when the bladder is expanded, a large number of concave grooves are provided from the portion corresponding to the tire crown portion on the surface of the bladder toward the portion corresponding to the tire bead portion. This groove is called a bladder vent line.

  Here, in the case where an unvulcanized tire using a thermoplastic resin composition is preformed to reduce the thickness of the inner liner layer and the tire is manufactured by the above conventional vulcanization process, after the vulcanization is completed, from the tire When shrinking and storing the bladder, there is a problem that the groove of the bladder vent line and the inner surface of the tire are rubbed and the thermoplastic resin composition constituting the inner liner layer is damaged. In particular, when the inner liner layer is made of a thermoplastic resin composition having a melting point lower than the vulcanization temperature and the thickness is less than 1 mm, the thermoplastic resin composition is softened at the end of vulcanization, so The damage of the liner layer is increased. For example, not only the inner pressure holding ability of the tire is reduced due to scratches on the inner liner layer, but there is also a risk that a crack may occur in the inner liner layer, leading to a serious accident in which the tire bursts during traveling.

  In Japanese Patent Laid-Open No. 2008-12751 (Patent Document 1), in order to efficiently discharge the gas between the bladder and the tire inner surface, the groove width, height, groove area of the bladder vent line, and the contour of the corner of the bladder are described. The ratio of the approximate radius R1 to the bladder outer diameter RA (R1 / RA), a cross vent line, and the like are disclosed.

  However, if a bladder having the bladder vent line is used for manufacturing an unvulcanized tire having an inner liner layer made of a thin thermoplastic resin composition, the inner liner layer may be damaged when the bladder contracts. .

JP 2008-12751 A

  The present invention uses a tire vulcanization bladder that discharges gas between the bladder and the inner surface of the tire without damaging the inner liner layer in the vulcanization process of the tire. The object is to produce a pneumatic tire with reduced rolling resistance.

The method for producing a pneumatic tire according to the present invention uses a tire vulcanizing bladder having a plurality of vent lines, and the pneumatic tire has an inner liner on the inner surface, and the inner liner is made of styrene-isobutylene. -A first layer including a styrene triblock copolymer, wherein the vent line includes a first vent line corresponding to the tire buttress portion from the tire bead toe portion, and a portion corresponding to the tire crown portion from the tire buttress portion. A groove section of the first vent line and the second vent line has a width of 0.5 mm or more and 3.0 mm or less on the mold side surface of the tire vulcanization bladder. The depth of the bladder from the mold side surface is 0.1 mm or more and 2.0 mm or less, and the first vent line and the second bed Groove cross-sectional area of the Trine is a 0.025 mm ² or more 6.0 mm ² or less, the first vent line, the angle α is 60 ° or more relative to a tangent of the portion corresponding to the tire bead toe portion 90 ° or less, and a second vent The line is characterized in that an angle β with respect to a tangent of a portion corresponding to the tire bead toe portion is not less than 40 ° and not more than 90 °, and the magnitude of the angle α and the angle β satisfies a relationship of α ≧ β.

  It is preferable that the shape of the groove | channel cross section of a 1st vent line and a 2nd vent line is a substantially rectangular shape, a substantially semicircle, or a substantially triangular shape.

  The inner liner preferably further includes a second layer made of an epoxidized styrene-butadiene-styrene triblock copolymer. The styrene-isobutylene-styrene triblock copolymer preferably has a weight average molecular weight of 50,000 to 400,000. The thickness of the first layer is preferably 0.05 mm or more and 0.6 mm or less, and the thickness of the second layer is preferably 0.01 mm or more and 0.3 mm or less.

  The styrene-isobutylene-styrene triblock copolymer preferably has a styrene unit content of 10% by mass to 30% by mass. The epoxidized styrene-butadiene-styrene triblock copolymer preferably has a weight average molecular weight of 10,000 to 400,000.

  The epoxidized styrene-butadiene-styrene triblock copolymer preferably has a styrene unit content of 10 to 30% by mass and an epoxy equivalent of 50 to 1,000.

  Said 1st layer contains 5 mass% or more and 40 mass% or less of styrene-isobutylene-styrene triblock copolymers, and contains at least 1 sort (s) of rubber components selected from the group which consists of natural rubber, isoprene rubber, and butyl rubber. It is preferable to contain 60 mass% or more and 95 mass% or less.

  The first layer preferably contains 0.1 parts by mass or more and 5 parts by mass or less of sulfur with respect to 100 parts by mass of the polymer component including the styrene-isobutylene-styrene triblock copolymer and the rubber component.

  According to the present invention, in the tire vulcanization process, by using a tire vulcanization bladder that discharges gas between the bladder and the tire inner surface without damaging the inner liner, air-in, flex cracking property It is possible to provide a method for manufacturing a pneumatic tire that exhibits excellent performance in adjustment, rolling resistance, and steering stability.

It is typical sectional drawing of the right half of the pneumatic tire in one embodiment of the present invention. It is a figure which shows the bladder for tire vulcanization | cure in one embodiment of this invention. It is typical sectional drawing of the vent line in one embodiment of this invention. It is a figure which shows the vent line in one embodiment of this invention. It is typical sectional drawing of the vent line in one embodiment of this invention. It is a figure which shows the vent line in one embodiment of this invention. It is typical sectional drawing of the polymer sheet in one embodiment of this invention. It is typical sectional drawing of the polymer laminated body in one embodiment of this invention.

<Pneumatic tire>
The structure of the pneumatic tire manufactured by the manufacturing method of this invention is demonstrated using FIG. The pneumatic tire 101 of the present invention is used for passenger cars, trucks / buses, heavy machinery and the like. The pneumatic tire 101 includes a crown portion 102, a tire buttress portion 110 that is continuous with a side edge of the crown portion 102, a sidewall portion 103, and a bead portion 104. Further, a bead core 105 is embedded in the bead portion 104. Further, a carcass 106 provided from one bead portion 104 to the other bead portion and folded back at both ends to lock the bead core 105, and a belt layer 107 made of two plies is disposed outside the crown portion of the carcass 106. Has been. An inner liner 109 extending from one bead portion 104 to the other bead portion is disposed on the inner side in the tire radial direction of the carcass 106. The belt layer 107 has two plies made of steel cord or aramid fiber cord arranged so that the plies intersect each other so that the cord is usually at an angle of 5 to 30 ° with respect to the tire circumferential direction. Is done. In the carcass, organic fiber cords such as polyester, nylon, and aramid are arranged at an angle of about 90 ° in the tire circumferential direction. In the region surrounded by the carcass and the folded portion, the bead core 105 extends from the upper end to the sidewall direction. An extending bead apex 108 is disposed. Insulation may be arranged between the inner liner 109 and the carcass 106.

  The inner liner 109 includes a portion 109 a corresponding to the tire buttress portion 110 from the bead toe portion 104 a and a portion 109 b corresponding to the crown portion 102 from the tire buttress portion 110. During tire vulcanization, a portion 109a corresponding to the tire buttress portion 110 from the bead toe portion 104a of the inner liner 109 is in contact with a first vent line of a vulcanizing bladder, which will be described later, and from the tire buttress portion 110 of the inner liner to the tire crown portion 102. The portion 109b corresponding to is in contact with a second vent line of a vulcanizing bladder described later.

A pneumatic tire manufactured using a bleed bladder having a plurality of vent lines has an inner liner 109 having a plurality of vent lines. In the inner liner 109, a first vent line is formed from the bead toe portion 104 a to the tire buttress portion 110, and a second vent line is formed from the tire buttress portion 110 to the tire crown portion 102. The shape of the 1st vent line and the 2nd vent line is the convex part formed in the surface of the side which contacts the budding bladder of an inner liner. Since this convex part is formed corresponding to the groove | channel of said addition bladder, the width | variety of a convex part is 0.5 mm or more and 3.0 mm or less, and the height of a convex part is 0.1 mm or more. 2.0 mm or less. Sectional area of the convex portion of the first vent line and second vent line is at 0.025 mm ² or more 6.0 mm ² or less, the first vent line, an angle α with respect to the tangent of the portion corresponding to the tire bead toe portion 60 The angle β with respect to the tangent of the portion corresponding to the tire bead toe portion is 40 ° or more and 90 ° or less, and the angle α and the angle β are α ≧ β. It is characterized by satisfying the relationship.

  The inner liner has at least a first layer containing a styrene-isobutylene-styrene triblock copolymer, and the thickness of the first layer is 0.05 mm or more and 0.6 mm or less. The inner liner 109 may have a second layer made of a thermoplastic elastomer in addition to the first layer. When the second layer is included, the thickness of the second layer is preferably 0.01 mm or more and 0.3 mm or less.

  In this way, using an inner liner composed of a first layer containing SIBS, or an inner liner composed of a first layer and a second layer containing a thermoplastic elastomer, a tire vulcanization bladder having a plurality of vent lines is used. By manufacturing a pneumatic tire, in the vulcanization process of the tire, without damaging the inner liner, while discharging the gas between the bladder and the tire inner surface, air-in, flex cracking adjustment, rolling resistance, In addition, it is possible to manufacture a pneumatic tire exhibiting excellent performance in handling stability. Below, the bladder for tire vulcanization used for manufacture of the pneumatic tire of the present invention is explained.

<Tire vulcanization bladder>
The vent line of the bladder for tire vulcanization used in the method for producing a pneumatic tire of the present invention will be described with reference to FIGS. In FIG. 2, flange portions 2a and 2b are provided at both ends of the tire vulcanizing bladder 1, and a plurality of vent lines 4 are provided from one flange portion 2a to the other flange portion 2b.

  The vent line 4 includes a first vent line 4a corresponding to the tire buttress portion from the tire bead toe portion, and a second vent line 4b corresponding to the tire crown portion from the tire buttress portion. A dotted line B indicates a boundary between the first vent line 4a and the second vent line 4b.

  In FIG. 3, the first bent line 4a has an angle α with respect to the tangent T of the portion A corresponding to the tire bead toe portion of the bladder of 60 ° or more and 90 ° or less, and preferably 80 ° or more and 90 ° or less. When the angle α is less than 60 °, the direction in which the bladder contracts and the direction of the vent line are greatly different, and there is a risk of scratches resulting from rubbing between the bladder and the inner liner. Note that since the angle α is 90 ° at the maximum with respect to the tangent line T, a value exceeding 90 ° is indicated as 180 ° − (value exceeding 90 °). Therefore, even when the angle α is greater than 90 ° and 120 ° or less, the condition that the angle α is 60 ° or more and 90 ° or less is satisfied.

  The magnitude of the angle α is preferably changed according to the material properties of the thermoplastic elastomer forming the inner liner of the tire. For example, when the thermoplastic elastomer has a low melting point and the softening phenomenon of the thermoplastic elastomer is large at the end of the vulcanization process at the time of manufacturing the tire, it is preferable that the angle α is large. On the other hand, when the thermoplastic elastomer has a high melting point and few scratches are generated due to rubbing between the bladder and the inner liner, the size of the angle α can be reduced.

  The second vent line 4b has an angle β (shown as an angle with respect to a line T ′ parallel to the tangent line T in FIG. 3) of the portion A corresponding to the tire bead toe portion of the bladder of 40 ° or more and 90 ° or less. It is preferably 45 ° or more and 90 ° or less. When the angle β is less than 40 °, the direction in which the bladder contracts and the direction of the vent line are greatly different, and there is a risk of scratches resulting from rubbing between the bladder and the inner liner. Note that since the angle β is 90 ° at the maximum with respect to the tangent line T, a value exceeding 90 ° is indicated as 180 ° − (value exceeding 90 °). Therefore, even when the angle β is greater than 90 ° and 140 ° or less, the condition that the angle β is 40 ° or more and 90 ° or less is satisfied.

  The size of the angle β is preferably smaller than 90 ° in order to prevent disturbance of the carcass cord arrangement in the tire buttress portion.

  The angles α and β satisfy the relationship α ≧ β. If the relationship between the angle α and the angle β is α <β, the gas between the tire inner surface and the bladder may not be sufficiently discharged during the tire vulcanization process. Examples of vent lines that satisfy the conditions of the angle α and the angle β are shown in FIGS.

FIG. 4A shows a vent line when the angle α is 90 ° and the angle β is 90 °.
FIG. 4B shows a vent line when the angle α is 90 ° and the angle β is 60 °.

FIG. 4C shows a vent line when the angle α is 90 ° and the angle β is 40 °.
FIG. 4D shows a vent line when the angle α is 60 ° and the angle β is 60 °.

FIG. 4E shows a vent line when the angle α is 60 ° and the angle β is 40 °.
The shape of the groove | channel cross section of the 1st vent line 4a and the 2nd vent line 4b is demonstrated using FIG. The double arrow line W in FIG. 5 is the width of the groove section of the vent line, and the double arrow line H is the depth of the groove section of the vent line. The hatched portion S is the groove cross-sectional area of the vent line, and the double arrow D is the distance between two adjacent vent lines.

  In the present specification, the width of the groove cross section of the first vent line and the second vent line means a width on the same plane as the surface of the groove on the mold side of the bladder. Therefore, for example, the groove sections of the first vent line and the second vent line are substantially semicircular or triangular, and the width of the groove sections of the first vent line and the second vent line is large depending on the distance from the bladder surface. Even when the lengths are different, the widths of the groove cross sections of the first vent line and the second vent line mean the width on the same plane as the surface of the bladder on the mold side.

  The width of the groove cross section of the first vent line and the second vent line is 0.5 mm to 3.0 mm, preferably 0.5 mm to 2.0 mm. When the width of the groove cross section of the first vent line and the second vent line is less than 0.5 mm, the strength of the line having the convex shape corresponding to the concave portion of the bladder vent line formed in the inner liner is weak, There is a risk of scratches resulting from the rubbing of the inner liner. On the other hand, if the width of the groove cross section of the first vent line and the second vent line exceeds 3.0 mm, the volume of the convex portion corresponding to the concave portion of the bladder vent line formed in the inner liner increases, and the tire is reduced in weight. There is a fear that you can not.

  Here, the depth of the groove cross section of the first vent line and the second vent line means the distance of the portion having the largest vertical distance from the bladder surface with respect to the same plane as the die side surface of the bladder. To do. Therefore, for example, when the groove sections of the first vent line and the second vent line are substantially semicircular or substantially triangular, and the depth from the bladder surface is not constant, the first vent line and the second vent line The depth of the groove cross-section means the distance of the portion having the largest distance from the bladder surface. Specifically, when the groove sections of the first vent line and the second vent line are substantially semicircular, the depths of the groove sections of the first vent line and the second vent line are as shown in FIG. It is indicated by a double arrow H in (e). When the shape of the groove cross section of the first vent line and the second vent line is substantially triangular, the depth of the groove cross section of the first vent line and the second vent line is the both in FIG. 5 (c) or (f). Indicated by arrow H.

  The depth of the groove cross section of the first vent line and the second vent line is 0.1 mm or more and 2.0 mm or less, and preferably 0.5 mm or more and 1.5 mm or less. If the depth of the groove cross section of the first vent line and the second vent line is less than 0.1 mm, the gas between the tire inner surface and the bladder may not be sufficiently discharged during the vulcanization process of the tire. On the other hand, if the depth of the groove cross section of the first vent line and the second vent line exceeds 2.0 mm, the volume of the convex portion corresponding to the concave portion of the bladder vent line formed in the inner liner increases, and the tire becomes light. There is a risk that it cannot be converted.

The groove cross-sectional areas of the first vent line and the second vent line are the line forming the groove and the ends of the line forming the groove on the same surface as the mold side of the bladder in the groove cross section. It means the area of the part surrounded by the line connecting. For example, referring to FIG. 5A, the groove sectional area S of the first vent line and the second vent line is the same as the line l ₁ forming the groove and the surface of the bladder in the groove cross section. This is the area of the portion surrounded by the line l ₂ connecting the ends of the lines forming the groove.

Groove cross-sectional area of the first vent line and second vent line is at 0.025 mm ² or more 6.0 mm ² or less, preferably 0.05 mm ² or more 5.0 mm ² or less. If the groove cross-sectional areas of the first vent line and the second vent line are less than 0.025 mm ² , the gas between the tire inner surface and the bladder may not be sufficiently discharged during the vulcanization process of the tire. On the other hand, if the groove cross-sectional area of the first vent line and the second vent line exceeds 6.0 mm ² , the volume of the convex portion corresponding to the concave portion of the bladder vent line formed in the inner liner increases, and the weight of the tire is reduced. There is a fear that it cannot be done.

  The distance between two adjacent vent lines is not particularly limited as long as the gas between the tire inner surface and the bladder is sufficiently discharged during the vulcanization process of the tire. The distance between two adjacent vent lines is preferably, for example, 2.0 mm or more and 6.0 mm or less, and more preferably 2.5 mm or more and 5.0 mm or less. If the distance between two adjacent vent lines is less than 2.0 mm, the volume of the convex portion corresponding to the concave portion of the bladder vent line formed on the inner liner may increase, and the tire may not be reduced in weight. There is. On the other hand, if the distance between two adjacent vent lines exceeds 6.0 mm, the gas between the tire inner surface and the bladder may not be sufficiently discharged during the tire vulcanization process.

  The groove shapes of the first vent line and the second vent line are, for example, a substantially rectangular shape shown in FIG. 5A, a substantially semicircular shape shown in FIG. 5B, or a substantially rectangular shape shown in FIG. A triangular shape is preferred. Furthermore, the shape of the cross section of the groove of the first vent line and the second vent line is, for example, as shown in FIGS. It can also be.

  A vent line in which the first vent line and the second vent line produced above are different from each other in the form of the second vent line will be described with reference to FIG.

The second vent line shown in FIGS. 6A and 6B is an angle with respect to the tangent T of the portion corresponding to the tire bead toe portion of the bladder (a line parallel to the tangent T in FIGS. 6A and 6B). is shown as an angle with respect to T ') comprises a vent line 4b ₁ is the angle beta _1, and a vent line 4b ₂ is an angle beta _2. By forming two second vent lines having different angles with respect to the tangent line T, the gas discharge effect can be enhanced.

When the angle β ₁ and the angle β ₂ are β ₁ ≦ β ₂ , the angle of the angle β ₁ with respect to the tangent line T corresponding to the tire bead toe portion of the bladder is 40 ° or more and 90 ° or less, preferably Is 45 ° or more and 90 ° or less. On the other hand, the angle of the angle β ₂ with respect to the tangent line T, when measured from the same direction as the angle β ₁ , is greater than 90 ° and equal to or less than 140 °, preferably greater than 90 ° and equal to or less than 135 °.

The angle α with respect to the tangent T of the portion corresponding to the tire bead toe portion of the bladder of the first vent line, and the sizes of the angles β ₁ and β ₂ satisfy the relationship of α ≧ β ₁ and α ≧ β ₂ . If the angles α, β ₁ , and β ₂ do not satisfy the above relationship, the gas between the tire inner surface and the bladder may not be sufficiently discharged during the tire vulcanization process.

6A and 6B show examples of vent lines that satisfy the conditions of the angle α, the angle β _1, and the angle β ₂ described above. FIG. 6A is a vent line when the angle α is 90 °, the angle β ₁ is 40 °, and the angle β ₂ is 140 °. FIG. 6B is a vent line when the angle α is 60 °, the angle β ₁ is 40 °, and the angle β ₂ is 140 °.

<Inner liner>
The inner liner used in the pneumatic tire of the present invention may be a single-layer polymer sheet as shown in FIG. 7 or a multilayer polymer laminate as shown in FIG. Regardless of whether the inner liner is a single-layer polymer sheet or a multilayer polymer laminate, a first vent line is formed from the bead toe portion 104a to the tire buttress portion 110, and the tire buttress portion 110 to the tire crown portion. Up to 102, a second vent line is formed.

<Inner liner made of a single polymer sheet>
FIG. 7 is a schematic cross-sectional view of a polymer sheet 10a used for the inner liner. As shown in FIG. 7, the polymer sheet 10a is composed of a first layer 11a made of a first thermoplastic resin composition containing a styrene-isobutylene-styrene triblock copolymer.

(First layer)
The 1st thermoplastic resin composition which comprises a 1st layer can be formed only from SIBS. The first thermoplastic resin composition contains SIBS in an amount of 5% by weight to 40% by weight and contains at least one rubber component selected from the group consisting of natural rubber, isoprene rubber and butyl rubber in an amount of 60% by weight to 95%. It is preferable to contain it by mass% or less. It may contain 0.1 part by mass or more and 5 parts by mass or less of sulfur with respect to 100 parts by mass of the polymer component including the SIBS and the rubber component. If the SIBS content is less than 5% by mass, the air barrier property of the polymer sheet may be lowered. On the other hand, when the content of SIBS exceeds 40% by mass, the vulcanization adhesive strength with the adjacent member may be insufficient. The content of SIBS is more preferably 10% by mass or more and 30% by mass or less in the polymer component from the viewpoint of ensuring air barrier properties.

(First thermoplastic resin composition)
The first thermoplastic resin composition may be formed only from SIBS, and may contain a rubber component and sulfur in addition to SIBS. When a rubber component and sulfur are added to SIBS and heated and mixed, the rubber component and sulfur are vulcanized during the heating and mixing to form a sea-island structure in which SIBS is a matrix (sea) and the rubber component is an island.

  The first thermoplastic resin composition having a sea-island structure has an air barrier property derived from a matrix phase made of SIBS. Furthermore, the rubber component forming the island phase has an unvulcanized adhesive property with the adjacent member containing the rubber component, and also vulcanizes with the rubber component of the adjacent member during the heating and mixing. Also has adhesiveness. Therefore, when the first layer made of the first thermoplastic resin composition is used as an inner liner, the inner liner has excellent air barrier properties, and at the same time has unvulcanized adhesiveness and vulcanized adhesiveness with adjacent members. Can have.

  The thickness of the first layer is preferably 0.05 mm or greater and 0.6 mm or less. In the tire obtained when the thickness of the first layer is less than 0.05 mm, the inner liner is broken by the press pressure during vulcanization of the raw tire in which the polymer sheet composed only of the first layer is applied to the inner liner. Air leak phenomenon may occur. On the other hand, if the thickness of the first layer exceeds 0.6 mm, the tire weight may increase and the fuel efficiency performance may deteriorate. The thickness of the first layer is preferably 0.05 mm or more and 0.4 mm or less.

  The first layer 11a can be obtained by a normal method of forming a sheet of a thermoplastic resin and a thermoplastic elastomer. For example, the first layer 11a can be obtained by extrusion molding of SIBS or calendar molding.

  Referring to FIG. 1, when the polymer sheet 10a is applied to the inner liner 109 of the pneumatic tire 101, the SIBS layer 11a and the carcass 106 can be vulcanized and bonded in the vulcanization process of the tire. Accordingly, since the obtained pneumatic tire 101 has a good adhesion between the inner liner 109 and the rubber layer of the carcass 106, air-in can be prevented and excellent air permeation resistance can be obtained.

(Styrene-isobutylene-styrene triblock copolymer: SIBS)
Due to the isobutylene block of SIBS, the thermoplastic resin composition containing SIBS has excellent air permeation resistance. Therefore, when the 1st layer which consists of this thermoplastic elastomer composition is used for an inner liner, a pneumatic tire excellent in air permeation resistance can be obtained.

  Furthermore, SIBS has excellent durability because its molecular structure other than aromatic is completely saturated, thereby preventing deterioration and hardening. Therefore, when a polymer sheet containing SIBS is used for the inner liner, a pneumatic tire having excellent durability can be obtained.

  When a pneumatic tire is manufactured by applying a first layer made of a thermoplastic resin composition containing SIBS to an inner liner, in order to ensure air permeation resistance by containing SIBS, for example, halogenated butyl rubber, The amount of use can be reduced even when the high specific gravity halogenated rubber that has been used for imparting air permeation resistance is not used or used. As a result, the weight of the tire can be reduced, and the effect of improving fuel consumption can be obtained.

  The molecular weight of SIBS is not particularly limited, but the weight average molecular weight by GPC method is preferably 50,000 or more and 400,000 or less from the viewpoint of fluidity, molding process, rubber elasticity and the like. If the weight average molecular weight is less than 50,000, the tensile strength and the tensile elongation may be lowered, and if it exceeds 400,000, the extrusion processability may be deteriorated.

  SIBS generally contains 10% to 40% by mass of styrene units. The content of styrene units in SIBS is preferably 10% by mass or more and 30% by mass or less from the viewpoint of better air permeation resistance and durability.

  SIBS preferably has a molar ratio of isobutylene units to styrene units (isobutylene units / styrene units) of 40/60 to 95/5 from the viewpoint of rubber elasticity of the copolymer. In SIBS, the degree of polymerization of each block is preferably about 10,000 to 150,000 for an isobutylene block and about 5,000 to 30,000 for a styrene block from the viewpoint of rubber elasticity and handling. If the degree of polymerization of each block is less than 10,000, it is not preferable because it becomes liquid.

  SIBS can be obtained by a general polymerization method of vinyl compounds. For example, it can be obtained by a living cationic polymerization method.

  JP-A-62-48704 and JP-A-64-62308 disclose that living cationic polymerization of isobutylene and other vinyl compounds is possible, and polyisobutylene is obtained by using isobutylene and other compounds as vinyl compounds. It is disclosed that block copolymers of the system can be produced. In addition to this, methods for producing vinyl compound polymers by the living cation polymerization method are disclosed in, for example, US Pat. No. 4,946,899, US Pat. No. 5,219,948, JP-A-3-174403, and the like. Are listed.

  Since SIBS does not have double bonds other than aromatics in the molecule, it is more stable to ultraviolet rays and has weather resistance than a polymer having double bonds in the molecule such as polybutadiene. It is good.

  The content of SIBS is preferably 5% by mass or more and 40% by mass or less in the polymer component of the first thermoplastic elastomer composition. If the SIBS content is less than 5% by mass, the air barrier property of the polymer sheet may be lowered. On the other hand, when the content of SIBS exceeds 40% by mass, the vulcanization adhesive strength with the adjacent member may be insufficient. The content of SIBS is more preferably 10% by mass or more and 30% by mass or less in the polymer component from the viewpoint of ensuring air barrier properties.

(Rubber component)
Said 1st layer may contain the rubber component. The rubber component can impart unvulcanized adhesiveness to an adjacent member containing the rubber component to the thermoplastic elastomer. Further, by vulcanizing with sulfur, the thermoplastic elastomer can be provided with vulcanization adhesion to adjacent members such as carcass and insulation.

  The rubber component contains at least one selected from the group consisting of natural rubber, isoprene rubber and butyl rubber, and among them, natural rubber is preferable from the viewpoint of breaking strength and adhesiveness.

  The content of the rubber component is preferably 60% by mass or more and 95% by mass or less in the polymer component of the first thermoplastic elastomer composition. When the content of the rubber component is less than 60% by mass, the viscosity of the thermoplastic elastomer composition is increased and the extrudability is deteriorated, so that the polymer sheet cannot be thinned when producing the polymer sheet for the inner liner. There is a fear. On the other hand, if the content of the rubber component exceeds 95% by mass, the air barrier property of the polymer sheet may be lowered. The content of the rubber component is more preferably 70% by mass or more and 90% by mass or less in the polymer component from the viewpoint of unvulcanized tackiness and vulcanized adhesiveness.

(sulfur)
The 1st thermoplastic elastomer composition which comprises said 1st layer can contain sulfur. Sulfur may be used as long as it is generally used at the time of vulcanization in the rubber industry, but insoluble sulfur is preferably used. Here, the insoluble sulfur, the natural sulfur S ₈ heated, quenched, refers to sulfur that high molecular weight so as to be Sx (x = 10 million in to 30 50,000). By using insoluble sulfur, blooming that normally occurs when sulfur is used as a rubber vulcanizing agent can be prevented.

  The content of sulfur is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. When the sulfur content is less than 0.1 parts by mass, the vulcanization effect of the rubber component cannot be obtained. On the other hand, when the sulfur content exceeds 5 parts by mass, the hardness of the thermoplastic elastomer composition increases, and when the polymer sheet is used as the inner liner, the durability performance of the pneumatic tire may be reduced. The sulfur content is further preferably 0.3 parts by mass or more and 3.0 parts by mass or less.

(Additive)
The first thermoplastic elastomer composition contained in the first layer may contain additives such as stearic acid, zinc oxide, an antioxidant, and a vulcanization accelerator.

  Stearic acid functions as a vulcanization aid for the rubber component. The content of stearic acid is preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. If the content of stearic acid is less than 1 part by mass, the effect as a vulcanization aid cannot be obtained. On the other hand, when the content of stearic acid exceeds 5 parts by mass, the viscosity of the thermoplastic elastomer composition is lowered, and the fracture strength may be lowered. The content of stearic acid is further preferably 1 part by mass or more and 4 parts by mass or less.

  Zinc oxide functions as a vulcanization aid for the rubber component. The content of zinc oxide is preferably 0.1 parts by mass or more and 8 parts by mass or less with respect to 100 parts by mass of the polymer component. When the content of zinc oxide is less than 0.1 part by mass, the effect as a vulcanization aid cannot be obtained. On the other hand, when the content of zinc oxide exceeds 8 parts by mass, the hardness of the thermoplastic elastomer composition increases, and when the polymer sheet is used for the inner liner, the durability performance of the pneumatic tire may be reduced. The content of zinc oxide is further preferably 0.5 parts by mass or more and 6 parts by mass or less.

  The anti-aging agent has a function of preventing a series of deteriorations such as oxidative deterioration, heat deterioration, ozone deterioration, fatigue deterioration and the like called aging. Anti-aging agents are classified into primary anti-aging agents composed of amines and phenols and secondary anti-aging agents composed of sulfur compounds and phosphites. The primary anti-aging agent has the function of stopping hydrogenation to various polymer radicals to stop the chain reaction of auto-oxidation, and the secondary anti-aging agent shows a stabilizing action by changing hydroxy peroxide to a stable alcohol. is there.

  Examples of the anti-aging agent include amines, phenols, imidazoles, phosphorus and thioureas.

  Examples of amines include phenyl-α-naphthylamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, p, p ′. -Dioctyldiphenylamine, p, p'-dicumyldiphenylamine, N, N'-di-2-naphthyl-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl- Examples include p-phenylenediamine, N-phenyl-N′-1,3-dimethylbutyl-p-phenylenediamine, and N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine.

  Examples of phenols include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-methylphenol, styrenated methylphenol, 2,2′-methylenebis (4-ethyl). -6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone and the like.

  Examples of imidazoles include 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, nickel dibutyldithiocarbamate, and the like.

  In addition, phosphorus such as tris (nonylated phenyl) phosphite, thiourea such as 1,3-bis (dimethylaminopropyl) -2-thiourea and tributylthiourea, wax for preventing ozone degradation may be used.

  The above antioxidants may be used alone or in combination of two or more. Of these, N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine is preferably used.

  The content of the antioxidant is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. When the content of the anti-aging agent is less than 0.1 parts by mass, the anti-aging effect cannot be obtained. On the other hand, when the content of the anti-aging agent exceeds 5 parts by mass, a blooming phenomenon occurs in the thermoplastic elastomer composition. The content of the antioxidant is further preferably 0.3 parts by mass or more and 4 parts by mass or less.

  As the vulcanization accelerator, thiurams, thiazoles, thioureas, dithiocarbamates, guanidines and sulfenamides can be used.

  Examples of thiurams include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, dipentamethylenethiuram tetrasulfide, and the like.

  Examples of thiazoles include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, N-cyclohexylbenzothiazole, N-cyclohexyl-2-benzothiazolesulfenamide, N-oxydiethylene-2-benzothiazolesulfenamide, N- Examples thereof include tert-butyl-2-benzothiazole sulfenamide, N, N-dicyclohexyl-2-benzothiazole sulfenamide, and N-tert-butyl-2-benzothiazolyl sulfenamide.

  Examples of thioureas include N, N′-diethylthiourea, ethylenethiourea, and trimethylthiourea.

  Dithiocarbamate salts include: zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, copper dimethyldithiocarbamate, dimethyldithiothiol Examples thereof include iron (III) carbamate, selenium diethyldithiocarbamate, and tellurium diethyldithiocarbamate.

  Examples of the guanidines include di-o-tolylguanidine, 1,3-diphenylguanidine, 1-o-tolylbiguanide, dicatechol borate di-o-tolylguanidine salt, and the like.

  Examples of the sulfenamides include N-cyclohexyl-2-benzothiazylsulfenamide.

  The above vulcanization accelerators may be used alone or in combination of two or more. Of these, dibenzothiazyl sulfide is preferably used.

  The content of the vulcanization accelerator is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. When the content of the vulcanization accelerator is less than 0.1 parts by mass, the vulcanization acceleration effect cannot be obtained. On the other hand, when the content of the vulcanization accelerator exceeds 5 parts by mass, the hardness of the thermoplastic elastomer composition increases, and when the polymer sheet is used for the inner liner, the durability performance of the pneumatic tire may be reduced. is there. Furthermore, the raw material cost of the thermoplastic elastomer composition increases. The content of the vulcanization accelerator is further preferably 0.3 parts by mass or more and 4 parts by mass or less.

(Method for producing polymer sheet for inner liner)
The polymer sheet for the inner liner can be produced, for example, by the following method. When the first thermoplastic elastomer composition contains SIBS, a rubber component, and sulfur, each compounding agent is put into a twin screw extruder and kneaded under conditions of about 150 to 280 ° C. and 50 to 300 rpm, and SIBS, rubber The pellet of the 1st thermoplastic elastomer composition in which a component, sulfur, and various additives as needed is dynamically crosslinked is obtained. The obtained pellets are put into a T-die extruder to obtain a polymer sheet having a desired thickness.

  In the twin screw extruder, SIBS becomes a matrix phase and the rubber component becomes an island phase and is dispersed. Further, in the twin-screw extruder, the rubber component and the additive component react, and the rubber component that is an island phase undergoes a crosslinking reaction. This is called dynamic crosslinking because the rubber component is dynamically crosslinked in a twin screw extruder. Even if the rubber component is cross-linked in a twin-screw extruder, the matrix phase of the system is composed of a thermoplastic elastomer component, so that the shear viscosity of the entire system is low and extrusion is possible.

  The pellets of the dynamically crosslinked first thermoplastic elastomer composition obtained by the twin screw extruder have the rubber component crosslinked but the matrix phase thermoplastic elastomer component retains the plasticity, and the entire system It plays a role in creating plasticity. For this reason, since plasticity is exhibited even in T-die extrusion, it can be formed into a sheet shape.

  Furthermore, since the rubber component of the pellet of the first thermoplastic elastomer composition that has been dynamically cross-linked is cross-linked, when a pneumatic tire is produced by applying a polymer sheet produced using the pellet to the inner liner Even if the pneumatic tire is heated, it is possible to prevent the thermoplastic elastomer composition of the inner liner from entering between the cords of the carcass layer.

<Inner liner made of polymer laminate>
FIG. 8 is a schematic cross-sectional view showing an example of a polymer laminate used for the inner liner of the present invention.

  The polymer laminate 10b of the present embodiment includes a first layer 11b made of a first thermoplastic elastomer composition containing a styrene-isobutylene-styrene triblock copolymer, and a second layer 12b made of a second thermoplastic elastomer composition. Have The thickness of the 1st layer 11b is 0.05 mm or more and 0.6 mm or less similarly to the above.

  Referring to FIG. 1, when the polymer laminate 10b is applied to the inner liner 109 of the pneumatic tire 101, the surface where the first layer 11b exists is directed to the innermost side in the tire radial direction, and the second layer 12b exists. If the surface is installed in the tire radial direction so as to be in contact with the carcass 106, the second layer 12b and the carcass 106 can be vulcanized and bonded in the tire vulcanization process. Therefore, since the obtained pneumatic tire 101 has a good adhesion between the inner liner 109 and the rubber layer of the carcass 106, it can prevent air-in and has excellent air permeation resistance and durability. Can do.

(First layer)
For the first layer, a thermoplastic elastomer composition similar to the first thermoplastic elastomer composition used in the preparation of the polymer sheet can be used.

  The thickness of the first layer is preferably 0.05 mm or greater and 0.6 mm or less. When the thickness of the first layer is less than 0.05 mm, the inner liner is broken by the press pressure during vulcanization of the raw tire to which the inner liner provided with the first layer is applied, and an air leak phenomenon occurs in the obtained tire. May occur. On the other hand, if the thickness of the first layer exceeds 0.6 mm, the tire weight may increase and the fuel efficiency performance may deteriorate. The thickness of the first layer is preferably 0.05 mm or more and 0.4 mm or less.

(Second layer)
The second layer included in the polymer laminate is a styrene-isoprene-styrene triblock copolymer, a styrene-isobutylene diblock copolymer, a styrene-butadiene-styrene triblock copolymer, a styrene-isoprene-butadiene-styrene triblock copolymer. Block copolymer, styrene-ethylene / butene-styrene triblock copolymer, styrene-ethylene / propylene / styrene triblock copolymer, styrene / ethylene / ethylene / propylene / styrene triblock copolymer, styrene / butadiene / It may include at least one thermoplastic elastomer selected from the group consisting of butylene-styrene triblock copolymers. These thermoplastic elastomers may be epoxy-modified thermoplastic elastomers having an epoxy group. Especially, it is preferable that a 2nd layer consists of an elastomer composition containing the styrene-butadiene-styrene block copolymer (epoxidized SBS) which has an epoxy group.

  The second layer is preferably a polymer sheet made of epoxidized SBS. Epoxidized SBS is a thermoplastic elastomer in which a hard segment is a polystyrene block and a soft segment is a butadiene block, and an unsaturated double bond portion contained in the butadiene block is epoxidized.

  Since the epoxidized SBS has a styrene block, the epoxidized SBS is excellent in melt adhesion with SIBS having a styrene block. Therefore, when the first layer and the second layer containing SIBS are arranged adjacent to each other and vulcanized, a polymer laminate in which the first layer and the second layer are well bonded can be obtained.

  Epoxidized SBS has a soft segment composed of a butadiene block, and thus is easily vulcanized and bonded to a rubber component. Therefore, when the epoxidized SBS layer is disposed and vulcanized adjacent to a rubber layer forming, for example, carcass or insulation, the epoxidized SBS layer and the rubber layer can be favorably bonded. Therefore, when a polymer laminate including an epoxidized SBS layer is used for the inner liner, adhesion between the polymer laminate and the adjacent rubber layer can be improved.

  The molecular weight of the epoxidized SBS is not particularly limited, but from the viewpoint of rubber elasticity and moldability, the weight average molecular weight by GPC method is preferably 10,000 or more and 400,000 or less. If the weight average molecular weight is less than 10,000, the size may be too soft and the dimensions may not be stable, and if it exceeds 400,000, it may be too hard to extrude thinly, which is not preferable.

  The content of styrene units in the epoxidized SBS is preferably 10% by mass or more and 30% by mass or less from the viewpoints of tackiness, adhesiveness, and rubber elasticity.

  The epoxidized SBS preferably has a molar ratio of butadiene units to styrene units (butadiene units / styrene units) of 90/10 to 70/30. In the epoxidized SBS, the degree of polymerization of each block is preferably about 500 to 5,000 for a butadiene block and about 50 to 1,500 for a styrene block from the viewpoint of rubber elasticity and handling. The epoxy equivalent of the epoxidized SBS is preferably from 50 to 1,000 from the viewpoint of adhesiveness.

  The second layer can be obtained by a usual method of forming a thermoplastic elastomer into a sheet such as extrusion molding or calendar molding.

(Additive)
The second thermoplastic elastomer composition constituting the second layer can contain sulfur as well as the additive used for the first thermoplastic elastomer composition, and also includes stearic acid, zinc oxide, anti-aging agent, vulcanization Additives such as accelerators can be included.

  The sulfur content is 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. If the sulfur content is less than 0.1 parts by mass, the crosslinking reaction may not occur. On the other hand, if the sulfur content exceeds 5 parts by mass, the crosslinking density of the thermoplastic elastomer composition may increase and the viscosity may increase. The sulfur content is further preferably 0.3 parts by mass or more and 3 parts by mass or less.

  The content of stearic acid is preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. If the stearic acid content is less than 1 part by mass, vulcanization may not occur. On the other hand, when the content of stearic acid exceeds 5 parts by mass, the breaking strength of the thermoplastic elastomer composition may be lowered. The content of stearic acid is further preferably 1 part by mass or more and 4 parts by mass or less.

  The content of zinc oxide is preferably 0.1 parts by mass or more and 8 parts by mass or less with respect to 100 parts by mass of the polymer component. If the zinc oxide content is less than 0.1 parts by mass, there is a risk that vulcanization will not occur. On the other hand, when the content of zinc oxide exceeds 8 parts by mass, the hardness of the thermoplastic elastomer composition is increased and the durability may be lowered. The content of zinc oxide is further preferably 0.5 parts by mass or more and 6 parts by mass or less.

  The content of the antioxidant is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. If the content of the anti-aging agent is less than 0.1 parts by mass, the anti-aging effect may not be obtained. On the other hand, if the content of the anti-aging agent exceeds 5 parts by mass, the blooming phenomenon may occur. The content of the antioxidant is further preferably 0.3 parts by mass or more and 4 parts by mass or less.

  The content of the vulcanization accelerator is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer component. If the content of the vulcanization accelerator is less than 0.1 parts by mass, the vulcanization acceleration effect may not be obtained. On the other hand, when the content of the vulcanization accelerator exceeds 5 parts by mass, the hardness of the thermoplastic elastomer composition becomes high and the durability may be lowered. Furthermore, the raw material cost of the thermoplastic elastomer composition increases. The content of the vulcanization accelerator is further preferably 0.3 parts by mass or more and 4 parts by mass or less.

  The thickness of the second layer is preferably 0.01 mm or more and 0.3 mm or less. If the thickness of the second layer is less than 0.01 mm, the second layer may be broken by the press pressure when the raw tire to which the inner liner including the second layer is applied is vulcanized, and the vulcanization adhesive force may be reduced. There is. On the other hand, if the thickness of the second layer exceeds 0.3 mm, the tire weight may increase and the fuel efficiency performance may deteriorate. The thickness of the second layer is preferably 0.05 mm or more and 0.2 mm or less.

  The polymer laminate 10b may further include a third layer in addition to the first layer and the second layer. In this case, the third layer can be formed between the first layer and the second layer, or may be formed on the side of the first layer opposite to the side in contact with the second layer, You may form in the opposite side to the side which contact | connects two 1st layers. Examples of the third layer include a layer made of urethane rubber or silicone rubber.

(Method for producing polymer laminate)
The polymer laminate of this embodiment can be produced, for example, by the following method. First, a 1st layer is produced by the method similar to the manufacturing method of said polymer sheet. Then, the second thermoplastic elastomer composition is formed into a sheet by extrusion molding, calendar molding, or the like to produce the second layer. The first layer and the second layer are bonded together to produce a polymer laminate. Alternatively, a polymer laminate may be produced by laminate extrusion such as laminate extrusion or coextrusion of each pellet of the first thermoplastic elastomer composition and the second thermoplastic elastomer composition.

  When the second layer contains a rubber component and sulfur, each compounding agent is put into a twin screw extruder and kneaded under conditions of about 150 to 280 ° C. and 50 to 300 rpm, and SIBS, rubber component, sulfur and necessary Accordingly, pellets of a thermoplastic elastomer in which various additives are dynamically cross-linked are obtained. The obtained pellets are put into a T-die extruder to obtain a polymer sheet having a desired thickness.

  In the twin screw extruder, SIBS becomes a matrix phase and the rubber component becomes an island phase and is dispersed. Further, in the twin-screw extruder, the rubber component and the additive component react, and the rubber component that is an island phase undergoes a crosslinking reaction. This is called dynamic crosslinking because the rubber component is dynamically crosslinked in a twin screw extruder. Even if the rubber component is cross-linked in a twin-screw extruder, the matrix phase of the system is composed of a thermoplastic elastomer component, so that the shear viscosity of the entire system is low and extrusion is possible.

  In the pellets of dynamically crosslinked thermoplastic elastomer obtained by a twin screw extruder, the rubber component is crosslinked, but the thermoplastic elastomer component in the matrix phase retains the plasticity, and produces the plasticity of the entire system. Playing a role. For this reason, since plasticity is exhibited even in T-die extrusion, it can be formed into a sheet shape.

  Further, since the rubber component of the dynamically crosslinked thermoplastic elastomer pellets is crosslinked, a pneumatic tire is used when manufacturing a pneumatic tire by applying a polymer sheet prepared using the pellet to the inner liner. Even when heated, it is possible to prevent the thermoplastic elastomer of the inner liner from entering between the cords of the carcass layer.

<Pneumatic tire manufacturing method>
The manufacturing method of the pneumatic tire of the present invention is manufactured by the following method. A raw tire is produced by applying the polymer sheet or polymer laminate produced above to the inner liner part. When the polymer laminate is used, the second layer is arranged outward in the tire radial direction so as to be in contact with the carcass and the insulation. When arranged in this manner, in the tire vulcanization step, the second layer and an adjacent member such as carcass or insulation can be vulcanized and bonded. Therefore, in the obtained pneumatic tire, since the inner liner is well bonded to the adjacent member, it can have excellent air permeation resistance and durability.

  Next, the raw tire is mounted on a mold, and heated using a tire vulcanizing bladder of the present invention at 150 to 180 ° C. for 3 to 50 minutes while being pressurized to obtain a vulcanized tire. Next, it is preferable to cool the obtained vulcanized tire at 50 to 120 ° C. for 10 to 300 seconds.

  The pneumatic tire uses the polymer sheet or polymer laminate as an inner liner. Since the SIBS, epoxidized SBS, and the like constituting the polymer sheet or polymer laminate are thermoplastic elastomers, when heated to, for example, 150 to 180 ° C. in the step of obtaining a vulcanized tire, Become. Since the thermoplastic elastomer in the softened state is more reactive than the solid state, it is fused to the adjacent member. That is, the inner liner in contact with the outer surface of the expanded bladder is softened by heating and fused to the bladder. If an attempt is made to remove the vulcanized tire from the mold while the inner liner and the outer surface of the bladder are fused, the inner liner peels off from the adjacent insulation or carcass, resulting in an air-in phenomenon. In addition, the tire shape itself may be deformed.

  Therefore, the thermoplastic elastomer used for the inner liner can be solidified by immediately cooling the obtained vulcanized tire at 120 ° C. or lower for 10 seconds or longer. When the thermoplastic elastomer is solidified, the fusion between the inner liner and the bladder is eliminated, and the releasability when the vulcanized tire is taken out from the mold is improved.

  The cooling temperature is preferably 50 to 120 ° C. When the cooling temperature is lower than 50 ° C., it is necessary to prepare a special cooling medium, which may deteriorate productivity. When the cooling temperature exceeds 120 ° C., the thermoplastic elastomer is not sufficiently cooled, and the inner liner remains fused to the bladder when the mold is opened, which may cause an air-in phenomenon. The cooling temperature is more preferably 70 to 100 ° C.

  The cooling time is preferably 10 to 300 seconds. If the cooling time is shorter than 10 seconds, the thermoplastic elastomer is not sufficiently cooled, and the inner liner remains fused to the bladder when the mold is opened, which may cause an air-in phenomenon. When the cooling time exceeds 300 seconds, the productivity is deteriorated. The cooling time is more preferably 30 to 180 seconds.

  The step of cooling the vulcanized tire is preferably performed by cooling the inside of the bladder. Since the inside of the bladder is hollow, the cooling medium adjusted to the above cooling temperature can be introduced into the bladder after the vulcanization process is completed.

  When moving to the cooling step at the end of pressurization / heating, it is preferable to move to the cooling step without lowering the bladder internal pressure. This is because if the pressure inside the bladder is lowered after the pressurization and heating, the thermoplastic elastomer is in a softened state, and there is a risk that the gauge changes, deforms, or voids occur due to the pressure drop. The process of cooling the vulcanized tire can be performed by cooling the inside of the bladder and installing a cooling structure in the mold.

  As the cooling medium, it is preferable to use one or more selected from the group consisting of air, water vapor, water, and oil. Among these, it is preferable to use water that is excellent in cooling efficiency.

<Production of polymer sheet and polymer laminate>
Each compounding agent was put into a twin screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 200 ° C.) according to the formulation shown in Table 1, and kneaded at 200 rpm to form pellets (Production Example 1). -Production Example 3). The obtained pellets were put into a co-extruder (cylinder temperature: 200 ° C.) to produce polymer sheets or polymer laminates having the structures shown in Tables 3 to 5.

(Note 1) IIR: “Exon Chlorobutyl 1066” manufactured by ExxonMobil Co., Ltd.
(Note 2) NR: Natural rubber TSR20.
(Note 3) SIBS: “Sibstar SIBSTAR 102T” manufactured by Kaneka Corporation (styrene-isobutylene-styrene triblock copolymer, weight average molecular weight 100,000, styrene unit content 25 mass%, Shore A hardness 25) .
(Note 4) Epoxidized SBS: “Epo Blend A1020” manufactured by Daicel Chemical Industries, Ltd.
(Note 5) Stearic acid: “Lunac stearate S30” manufactured by Kao Corporation.
(Note 6) Zinc oxide: “Zinc Hana 1” manufactured by Mitsui Kinzoku Mining Co., Ltd.
(Note 7) Anti-aging agent: “NOCRACK 6C” (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 8) Vulcanization accelerator: “Noxeller DM” (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 9) Sulfur: “Powdered sulfur” manufactured by Tsurumi Chemical Co., Ltd.

<Manufacture of pneumatic tires>
The obtained polymer sheet or polymer laminate was applied to the inner liner portion of the tire to prepare a green tire. In addition, the polymer laminated body was arrange | positioned so that a 1st layer might be arrange | positioned inside the radial direction of a green tire, and a 2nd layer might contact | connect the carcass layer of a green tire. The raw tire was press-molded at 170 ° C. for 20 minutes using a tire vulcanizing bladder having a bladder vent line having the shape shown in Tables 3 to 5 in a mold, and a 195 / 65R15 size vulcanized tire was obtained. Manufactured. After the vulcanized tire was cooled at 100 ° C. for 3 minutes, the vulcanized tire was taken out of the mold to obtain a pneumatic tire.

The following evaluation was performed using the obtained pneumatic tire.
((A) Inner liner layer damage)
The inner liner layer inside the vulcanized tire was visually inspected for damage. Judgment criteria are as follows. The magnitude of damage is not considered.
A: The number of damage of the inner liner per tire is zero in appearance.
B: The number of damage of the inner liner per tire is one or more in appearance.

((B) Air-in presence / absence)
The inside of the tire after the vulcanization and cooling process was inspected and evaluated according to the following criteria.
A: From the appearance, the number of air-ins having a diameter of 5 mm or less per tire is 0, and the number of air-ins having a diameter exceeding 5 mm is 0.
B: From the appearance, the number of air-ins having a diameter of 5 mm or less per tire is 1 to 3 and the number of air-ins having a diameter exceeding 5 mm is 0.
C: In terms of appearance, the number of air-ins having a diameter of 5 mm or less per tire is 4 or more, or the number of air-ins having a diameter of 5 mm or more is 1 or more.

((C) Flexural crack growth)
In the tire durability running test, it was evaluated whether the inner liner was cracked or peeled off. The manufactured 195 / 65R15 size pneumatic tire is assembled to a JIS standard rim 15 × 6JJ, the tire internal pressure is 150 KPa which is lower than usual, the load is 600 kg, the speed is 100 km / hour, and the traveling distance is 20,000 km. The inside of the tire was observed and the number of crack peeling was measured. The obtained numerical values were indexed by the following formulas for the flex crack growth properties of each example and each comparative example, with Example 28 as a reference (100). The larger the value, the better the flex crack growth resistance.
(Bending crack growth index) = (Number of crack peeling in Example 28) / (Number of crack peeling in each example and each comparative example) × 100.

((D) Rolling resistance)
Using a rolling resistance tester manufactured by Kobe Steel Co., Ltd., the manufactured 195 / 65R15 size pneumatic tire was assembled into a JIS standard rim 15 × 6JJ, under conditions of a load of 3.4 kN, an air pressure of 230 kPa, and a speed of 80 km / hour. Then, the rolling resistance was measured by running at room temperature (38 ° C.). The numerical values obtained were based on Example 28 as a reference (100), and the rolling resistance of each Example and each Comparative Example was indicated by an index according to the following formula. In addition, it shows that rolling resistance is reduced and it is so preferable that a numerical value is large.
(Rolling resistance index) = (Rolling resistance of Example 28) / (Rolling resistance of each example and each comparative example) × 100.

The results are shown in Tables 3-5.
(Comprehensive judgment)
Table 2 shows the criteria for comprehensive judgment.

(Contrast with Examples 1-27 and Example 28)
The pneumatic tires of Examples 1 to 27 include an inner liner made of a polymer laminate including the first layer and the second layer, but the pneumatic tire of Example 28 is made of a polymer sheet made only of the first layer. Including an inner liner. For this reason, the pneumatic tires of Examples 1 to 27 show superior performance in air-in, flex cracking adjustment, rolling resistance, and steering stability as compared with those of Example 28.

(Contrast with Examples 1-28 and Comparative Examples 1-7)
Examples 1 to 28 are tires manufactured using the tire vulcanizing bladder according to the present invention. The tire had no damage to the inner liner layer, and generation of air-in could be satisfactorily suppressed. Furthermore, it was excellent in bending crack growth resistance and reduced rolling resistance.

  Comparative Examples 1 to 7 are tires manufactured using a tire vulcanizing bladder whose vent line shape is outside the scope of the present invention. In the tire, the inner liner layer was damaged.

  From the above results, the pneumatic tires manufactured in Examples 1 to 28 show superior performance in air-in, flex cracking adjustment, rolling resistance, and steering stability as compared with those in Comparative Examples 1 to 7. It became clear.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 tire vulcanizing bladder, 2a, 2b flange, 4, 4b _1, 4b ₂ vent line, 4a first vent line, 4b second vent lines, 10a polymer sheets, 10b polymeric laminate, 11a, 11b first layer , 12b Second layer, 101 Pneumatic tire, 102 Tire crown portion, 103 Side wall portion, 104 Bead portion, 104a Bead toe portion, 105 Bead core, 106 Carcass, 107 Belt layer, 108 Bead apex, 109 Inner liner, 110 Tire buttress Department.

An angle alpha relative to the tangent T of the portion corresponding to the tire bead toe portion of the bladder of the first vent line, the magnitude of the angle beta ₁ and the angle beta ₂ is, alpha ≧ beta ₁ cutlet α ≧ (180- β ₂₎ Relationship Meet. If the angles α, β ₁ , and β ₂ do not satisfy the above relationship, the gas between the tire inner surface and the bladder may not be sufficiently discharged during the tire vulcanization process.

Claims (10)

A method of manufacturing a pneumatic tire using a tire vulcanizing bladder having a plurality of vent lines,
The pneumatic tire includes an inner liner on an inner surface,
The inner liner includes a first layer including a styrene-isobutylene-styrene triblock copolymer,
The vent line includes a first vent line corresponding to the tire buttress portion from the tire bead toe portion, and a second vent line corresponding to the tire crown portion from the tire buttress portion,
The shape of the groove cross section of the first vent line and the second vent line is such that the width on the mold side surface of the tire vulcanization bladder is 0.5 mm or more and 3.0 mm or less and the mold side of the tire vulcanization bladder is The depth from the surface is 0.1 mm or more and 2.0 mm or less,
Groove cross-sectional area of the first vent line and second vent line is at 0.025 mm ² or more 6.0 mm ² or less,
The first vent line has an angle α with respect to a tangent of a portion corresponding to the tire bead toe portion of 60 ° or more and 90 ° or less, and the second vent line is with respect to a tangent of a portion corresponding to the tire bead toe portion. The angle β is 40 ° or more and 90 ° or less,
The method of manufacturing a pneumatic tire, wherein the angle α and the angle β satisfy a relationship of α ≧ β.   The method for manufacturing a pneumatic tire according to claim 1, wherein a shape of a groove cross section of each of the first vent line and the second vent line is a substantially rectangular shape, a substantially semicircular shape, or a substantially triangular shape.   The method for producing a pneumatic tire according to claim 1, wherein the inner liner further includes a second layer made of an epoxidized styrene-butadiene-styrene triblock copolymer. The thickness of the first layer is 0.05 mm or more and 0.6 mm or less,
The method for manufacturing a pneumatic tire according to claim 3, wherein the thickness of the second layer is 0.01 mm or more and 0.3 mm or less.   The method for producing a pneumatic tire according to any one of claims 1 to 3, wherein the styrene-isobutylene-styrene triblock copolymer has a weight average molecular weight of 50,000 to 400,000.   The method for producing a pneumatic tire according to any one of claims 1 to 4, wherein the styrene-isobutylene-styrene triblock copolymer has a styrene unit content of 10 mass% or more and 30 mass% or less.   The method for producing a pneumatic tire according to any one of claims 3 to 6, wherein the epoxidized styrene-butadiene-styrene triblock copolymer has a weight average molecular weight of 10,000 or more and 400,000 or less.   The epoxidized styrene-butadiene-styrene triblock copolymer has a styrene unit content of 10% by mass or more and 30% by mass or less, and an epoxy equivalent of 50 or more and 1,000 or less. A method for producing a pneumatic tire according to claim 1.   The first layer contains at least one rubber component selected from the group consisting of natural rubber, isoprene rubber, and butyl rubber, containing 5% by weight to 40% by weight of a styrene-isobutylene-styrene triblock copolymer. The manufacturing method of the pneumatic tire in any one of Claims 1-8 containing 10 mass% or more and 95 mass% or less.   The said 1st layer contains 0.1 mass part or more and 5 mass parts or less sulfur with respect to 100 mass parts of polymer components which consist of a styrene-isobutylene-styrene triblock copolymer and a rubber component. The manufacturing method of the pneumatic tire in any one.

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