JP2012131031A - Pneumatic tire and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a pneumatic tire which has unvulcanized viscosity and vulcanized adhesiveness sufficiently between an inner liner and an adjacent member adjacent thereto and can remove air from the space therebetween.SOLUTION: In the production method of a pneumatic tire, upon molding an unvulcanized tire, the adjacent member adjacent to the inner liner 9 has a ventilation passage for removing the air, on the side adjacent to the inner liner 9 and the adjacent member is an insulation layer made of rubber selected from among natural rubber, isoprene rubber, butadiene rubber styrene-butadiene rubber or butyl rubber or a carcass layer 6 obtained by topping an unvulcanized rubber sheet on a cord. The inner liner 9 has a single-layer or multilayer structure having at least one first layer. The first layer comprises SIBS (styrene-isobutylene-styrene triblock copolymer) or a thermoplastic elastomer composition containing the SIBS.

Description

  The present invention relates to a method for manufacturing a pneumatic tire, and more particularly to a method for manufacturing a pneumatic tire in which air is hardly mixed between an inner liner and an adjacent member.

  In recent years, tires have been reduced in weight due to a strong social demand for lower fuel consumption of vehicles. In an inner liner that is arranged inside a tire member in the radial direction of a tire and has a function of improving air permeation resistance by reducing the amount of air leakage (air permeation amount) from the inside to the outside of a pneumatic tire. However, weight reduction has come to be performed.

  Currently, the rubber composition for an inner liner uses a butyl rubber containing 70 to 100% by mass of butyl rubber and 30 to 0% by mass of natural rubber to improve the air permeability 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. The butyl rubber usually requires a thickness of about 0.6 to 1.0 mm for passenger car tires and about 1.0 to 2.0 mm for truck and bus tires.

  Therefore, as an attempt to reduce the weight of the tire, it has been proposed to use a polymer that is superior in air permeation resistance and can be made thinner than the butyl rubber as a material constituting the inner liner. For example, in the prior art, in order to reduce the weight of the inner liner layer, it has been proposed to use a thermoplastic elastomer instead of a butyl rubber.

  However, the thermoplastic elastomer, which is thinner than butyl rubber and has high air permeation resistance, is inferior to butyl rubber in vulcanization adhesion to insulation rubber and carcass rubber adjacent to the inner liner. ing. For this reason, air mixes between the inner liner and the insulation rubber or carcass rubber, and many small bubbles appear (air-in phenomenon).

  This air-in phenomenon gives the user an impression that the appearance is poor because of the appearance of small spots on the inside of the tire, and the inner liner and the insulation or carcass peel off from the air while driving, causing the inner There is also a problem that the tire pressure is reduced due to cracks in the liner, and in the worst case, the tire bursts.

JP 2009-274359 A

  As an attempt to escape the air mixed between the inner liner and the insulation rubber or the carcass rubber as described above, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2009-274359), the air is applied to the insulation rubber or the carcass rubber. A route to escape is provided.

  However, the adhesive force between the inner liner and the insulation rubber or carcass rubber is not sufficient, and there is a problem that air is embraced between the inner liner and the insulation rubber or carcass rubber after vulcanization.

  The present invention has been made in view of the current situation as described above, and the object of the present invention is to sufficiently have unvulcanized adhesiveness and vulcanized adhesiveness between an inner liner and an adjacent member adjacent thereto. And it is providing the manufacturing method of the pneumatic tire which can escape the air in the meantime.

  In the method for producing a pneumatic tire according to the present invention, when molding an unvulcanized tire, the adjacent member adjacent to the inner liner has a ventilation path for releasing air on the side adjacent to the inner liner, The adjacent member is an insulation layer made of any kind of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, or butyl rubber, or a carcass layer topped with an unvulcanized rubber sheet on the cord. The liner is a single layer structure or a multilayer structure including at least a first layer, and the first layer includes a styrene-isobutylene-styrene triblock copolymer or the styrene-isobutylene-styrene triblock copolymer. It consists of any one of thermoplastic elastomers.

  The ventilation path preferably faces at least the end of the inner liner. It is preferable that the arrangement density of the ventilation path facing the end portion of the inner liner is higher than the arrangement density of the ventilation path other than the ventilation path facing the end portion of the inner liner. Preferably, the inner liner extends between the left and right beat portions, and the adjacent member is disposed adjacent to at least the end portion of the inner liner in the beat portion.

The ventilation path is preferably formed by a narrow groove provided adjacent to the inner liner of the adjacent member. The fine grooves preferably have a total volume per unit area of 2.0 to 30.0 mm ³ / cm ² . The depth of the narrow groove is preferably 1.0 mm or less.

The ventilation path is preferably made of a breathable yarn provided adjacent to the inner liner of the adjacent member. The breathable yarn preferably has a total volume per unit area of 0.5 to 30.0 mm ³ / cm ² . The breathable yarn preferably has an arrangement number of 10 to 100 / m per unit length. The ventilation path preferably extends to the edge of the adjacent member.

The ventilation path is preferably composed of a plurality of through holes provided adjacent to the inner liner of the adjacent member, and the fine holes have a total area per unit area of 0.002 to 5.0 mm ² / More preferably, it is cm ² . The diameter of the narrow hole is preferably 1.5 mm or less.

  The first layer is a styrene-isobutylene-styrene triblock copolymer and preferably contains 10 to 30% by mass of styrene.

  The inner liner has a multilayer structure further including a second layer, and the second layer is an SIS layer made of a styrene-isoprene-styrene block copolymer or an SIB layer made of a styrene-isobutylene block copolymer. It is preferable to contain a thermoplastic elastomer containing one or two or more of styrene-isoprene-styrene block copolymer or styrene-isobutylene block copolymer.

  The styrene-isoprene-styrene block copolymer contained in the SIS layer preferably has a styrene / isoprene polymerization ratio of 10/90 to 30/70.

  The styrene-isobutylene block copolymer contained in the SIB layer preferably has a weight average molecular weight of 40,000 to 120,000, and a styrene / ethylene polymerization ratio of 10/90 to 35/65.

  The present invention also relates to a pneumatic tire manufactured by the method for manufacturing a pneumatic tire described above.

  By having the above-described configuration, the present invention has sufficient unvulcanized adhesiveness and vulcanized adhesiveness between the inner liner and the adjacent member adjacent to the inner liner, and can release air therebetween. Provided is a method for manufacturing a filled tire.

It is typical sectional drawing which shows the right half of the pneumatic tire manufactured by the manufacturing method of this invention. It is a schematic diagram when an example of the adjacent member used for the pneumatic tire of this invention is seen from the upper surface. It is a schematic diagram when an example of the adjacent member used for the pneumatic tire of this invention is seen from the upper surface. It is a schematic diagram when an example of the adjacent member used for the pneumatic tire of this invention is seen from the upper surface. It is a schematic diagram when an example of the adjacent member used for the pneumatic tire of this invention is seen from the upper surface. It is a schematic diagram when an example when a breathable thread | yarn is provided in the adjacent member used for the pneumatic tire of this invention is seen from the upper surface. It is a schematic diagram when an example when a narrow groove and a breathable thread | yarn are provided in the adjacent member used for the pneumatic tire of this invention is seen from the upper surface. It is a schematic diagram when an example when the thin hole which penetrates to the adjacent member used for the pneumatic tire of this invention is provided is seen from the upper surface. It is a schematic diagram when an example is seen from the upper surface when a narrow groove and a narrow hole which penetrates are provided in the adjacent member used for the pneumatic tire of the present invention. It is a typical sectional view showing the inner liner of the single layer structure used for the pneumatic tire of the present invention. It is typical sectional drawing which shows the inner liner of the multilayer structure used for the pneumatic tire of this invention. It is typical sectional drawing which shows the inner liner of the multilayer structure used for the pneumatic tire of this invention.

<Pneumatic tire>
The structure of the pneumatic tire manufactured by the manufacturing method of this invention is demonstrated using FIG. FIG. 1 is a schematic cross-sectional view showing the right half of a pneumatic tire manufactured by the manufacturing method of the present invention. The pneumatic tire 1 can be used for passenger cars, trucks / buses, heavy machinery and the like. The pneumatic tire 1 has a tread portion 2, a sidewall portion 3, and a bead portion 4. Further, a bead core 5 is embedded in the bead portion 4. Also, a carcass layer 6 provided from one bead portion 4 to the other bead portion 4 to fold back both ends to lock the bead core 5, and a belt layer 7 made of two plies on the outer side of the crown portion of the carcass layer 6. And are arranged.

  An inner liner 9 extending from one bead portion 4 to the other bead portion 4 is arranged on the inner side in the tire radial direction of the carcass layer 6. The belt layer 7 has two plies made of steel cord or aramid fiber cord arranged so that the plies cross each other so that the cord is usually at an angle of 5 to 30 ° with respect to the tire circumferential direction. Is done. The carcass layer has organic fiber cords such as polyester, nylon, and aramid arranged at an angle of approximately 90 ° in the tire circumferential direction. A bead apex 8 extending in the wall direction is arranged. An insulation layer may be disposed between the inner liner 9 and the carcass layer 6.

<Adjacent member>
In the pneumatic tire 1 according to the present invention, an adjacent member is provided adjacent to the inner liner 9. Such an adjacent member is an insulation layer made of any kind of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, or butyl rubber, or a carcass layer 6 in which a cord is topped with an unvulcanized rubber sheet.

  And in this invention, it has the ventilation path for releasing air in the side adjacent to the inner liner 9 of an adjacent member, It is characterized by the above-mentioned. By providing a ventilation path in the adjacent member adjacent to the inner liner 9 in this way, when molding an unvulcanized tire, between the inner liner 9 and the carcass layer 6 or between the inner liner 9 and the insulation layer. The air mixed in between can be released, so that the pneumatic tire 1 with less air accumulation can be produced even in an unvulcanized tire or a vulcanized tire.

  The ventilation path provided in the adjacent member is preferably provided as a whole as shown in FIG. 2, but may be provided at both ends instead of being provided at the center as shown in FIG. . That is, it is preferable that the ventilation path provided in the adjacent member faces at least the end of the inner liner. By providing the ventilation path at such a position, the effect of releasing the air can be enhanced. Here, the “end portion of the inner liner” means a tip portion where the inner liner is interrupted, for example, a portion located substantially inside the beat core 5 in FIG.

  The ventilation path 14 provided in the adjacent member is not limited to one that forms a certain angle with respect to the end of the adjacent member as shown in FIG. 3, but the end of the adjacent member as shown in FIG. It may extend vertically.

  Further, as shown in FIG. 5, it is preferable to form a shorter ventilation path 14A between the ventilation paths 14 of FIG. 4 in a region facing the end of the inner liner. In this way, the arrangement density of the ventilation paths 14 facing the end of the inner liner 9 can be made higher than the arrangement density of the ventilation paths other than the ventilation path 14 facing the end of the inner liner 9, Therefore, the air remaining on the end side of the inner liner 9 can be easily released to the outside of the interlayer.

  Since air is easily taken in at the end of the inner liner 9 extending to the bead portion 4, air is likely to be mixed between the inner liner 9 and the carcass layer or the insulation layer in this portion. Therefore, it is preferable that the inner liner 9 extends between the left and right beat portions 4, and adjacent members are disposed adjacent to the beat portions 4.

<Ventilation path>
In the present invention, the ventilation path is provided adjacent to the inner liner 9 of the adjacent member, and is provided for releasing air mixed between the adjacent member and the inner liner 9. The ventilation path is provided in the adjacent member in one or more forms selected from the group consisting of a narrow groove, a breathable thread, and a through hole. Hereinafter, the ventilation path of each form is demonstrated.

(Narrow groove)
When the ventilation path is formed by narrow grooves, the total volume per unit area of the narrow grooves is preferably 2.0 to 30.0 mm ³ / cm ² , more preferably 5.0 to 25.0 mm. ³ / cm ² . If it is less than 2.0 mm ³ / cm ² , there is a possibility that the air between adjacent members cannot be effectively released. If it exceeds 30.0 mm ³ / cm ² , it will cause air accumulation. . Such a narrow groove preferably has a depth of 0.3 mm to 1.0 mm. If it exceeds 1.0 mm, it is not preferable because it causes air accumulation on the contrary, and if it is less than 0.3 mm, air cannot be efficiently released.

(Breathable thread)
FIG. 6 is a schematic view of an example when a breathable yarn is provided on an adjacent member used in the pneumatic tire of the present invention as viewed from above. As shown in FIG. 6, when the ventilation path is formed by the breathable thread 16, the total volume per unit area of the breathable thread is 0.5 to 30.0 mm ³ / cm ² . It is preferably 1.0 to 25.0 mm ³ / cm ² . If it is less than 0.5 mm ³ / cm ² , the air mixed between adjacent members cannot be effectively released, and if it exceeds 30.0 mm ³ / cm ² , Since the unevenness at the interface increases, the adhesiveness of these two members decreases, causing air accumulation.

  The breathable yarn 16 has an arrangement number per unit length of preferably 10 to 100 / m, more preferably 20 to 80 / m. When the arrangement number per unit length of the breathable yarn is less than 10 / m, the air mixed with the adjacent member cannot be effectively released, and when it exceeds 100 / m, Since unevenness at the interface between the inner liner and the adjacent member increases, the adhesiveness between these two members decreases, causing air accumulation. Such a ventilation path is preferably provided so as to extend to the edge of the adjacent member. In addition, as shown in FIG. 7, a narrow groove and a breathable thread may be combined and provided on the adjacent member.

(Through hole to penetrate)
FIG. 8 is a schematic view when an example is seen from the upper surface when a fine hole penetrating an adjacent member used in the pneumatic tire of the present invention is provided. As shown in FIG. 8, the ventilation path may be configured by providing a plurality of fine holes 17 so as to penetrate the adjacent member. When the ventilation path is formed by a through-hole, the through-hole has a total area per unit area of preferably 0.002 to 5.0 mm ² / cm ² , more preferably it is a 0.01~4.0mm ² / cm ^2. If the total area per unit area of the fine holes is less than 0.002 mm ² / cm ² , air between adjacent members may not be effectively released. On the other hand, if it exceeds 5.0 mm ² / cm ² , it is not preferable because it causes air accumulation.

  It is preferable to provide the narrow hole in the entire adjacent member. However, as in the case of the narrow groove, even if it is provided only at the end of the inner liner without being provided only in the center, air can be effectively released. it can. Similarly to the narrow grooves, the arrangement density of the narrow holes in the region facing the end of the inner liner may be increased, or the pores may be provided only at the end of the inner liner extending to the beat portion. .

  The diameter of the fine hole is preferably 1.5 mm or less. If the diameter of the narrow hole exceeds 1.5 mm, it is not preferable because it causes air accumulation. In addition, the lower limit value of the diameter of the narrow hole is not particularly limited as long as it satisfies the above-mentioned total area per unit area. In addition, as shown in FIG. 9, a narrow groove and a narrow hole that penetrates may be combined and provided in the adjacent member.

<Inner liner>
In the present invention, the inner liner 9 preferably has a single layer structure including at least a first layer or a multilayer structure including a first layer and a second layer. The first layer is made of a styrene-isobutylene-styrene triblock copolymer (hereinafter also referred to as “SIBS”) or a thermoplastic elastomer containing the SIBS. In the following, first, an inner liner having a single layer structure including only the first layer shown in FIG. 10 will be described.

(First layer)
As shown in FIG. 10, the SIBS isobutylene block contained in the first layer 20 has excellent air permeation resistance. Therefore, when the first layer containing SIBS is used for the inner liner, a pneumatic tire excellent in air permeation resistance can be obtained.

  Further, SIBS has excellent durability because its molecular structure other than aromatic is completely saturated, thereby preventing deterioration and hardening. Therefore, when the first layer containing SIBS shown in FIG. 10 is used for the inner liner, a pneumatic tire having excellent durability can be obtained.

  When a pneumatic tire is manufactured by applying the first layer containing SIBS to the inner liner, the conventional air permeation resistance, such as halogenated butyl rubber, is provided to ensure air permeation resistance by incorporating SIBS. Therefore, it is possible to reduce the amount of use even if the high specific gravity halogenated rubber that has been used for this purpose is not used. As a result, the weight of the tire can be reduced, and the effect of improving fuel consumption can be obtained.

  The first layer contains SIBS in an amount of 10% by mass to 30% by mass, and further contains at least one rubber component selected from the group consisting of natural rubber, isoprene rubber and butyl rubber in an amount of 70% by mass to 90% by mass. Is preferred. Moreover, it is preferable that 0.1 mass part or more and 5 mass parts or less of sulfur are included with respect to 100 mass parts of these polymer components. Thus, when the rubber component and sulfur are added to SIBS and heated and mixed, the rubber component and sulfur undergo a vulcanization reaction during heating and mixing, and a sea island structure in which the SIBS is a matrix (sea) and the rubber component is an island. Form.

  If the SIBS content is less than 10% by mass, the air barrier property of the inner liner may be lowered. On the other hand, if the content of SIBS exceeds 30% by mass, the vulcanization adhesive strength with the adjacent member may be insufficient. The SIBS content is preferably 15% by mass or more and 25% by mass or less in the polymer component from the viewpoint of ensuring air barrier properties.

  The first layer having the sea-island structure as described above has an air barrier property derived from a matrix phase made of SIBS. Furthermore, the rubber component that forms the island phase has an unvulcanized adhesive property with an adjacent member containing the rubber component and also undergoes a vulcanization reaction with the rubber component of the adjacent member during heating and mixing. Also has sulfur adhesion. Therefore, it is preferable that SIBS contains a rubber component or sulfur. Thereby, the inner liner which consists of a 1st layer can have the unvulcanized adhesiveness and vulcanization adhesiveness with an adjacent member while being excellent in air barrier property. Hereinafter, SIBS, rubber component, and sulfur contained in the first layer may be collectively referred to as “polymer component”.

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

  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% by mass or more and 40% by mass or less 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 about 10,000 to 150,000 for the isobutylene block and 5,000 to 5,000 for the styrene block from the viewpoint of rubber elasticity and handling (becomes liquid when the degree of polymerization is less than 10,000). It is preferably about 30,000.

  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, methods for producing vinyl compound polymers by the living cationic polymerization method are disclosed in, for example, U.S. Pat. No. 4,946,899, U.S. Pat. No. 5,219,948, and JP-A-3-174403. 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.

(Rubber component)
It is preferable that the 1st layer which comprises an inner liner contains a rubber component. The rubber component can give unvulcanized adhesiveness with an adjacent member containing the rubber component in the first layer. Furthermore, the vulcanization reaction with sulfur can provide the polymer composition 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 in particular, from the viewpoint of breaking strength and adhesiveness, natural rubber is preferably included.

  The content of the rubber component is preferably 60% by mass or more and 95% by mass or less in the polymer component contained in the first layer. When the content of the rubber component is less than 60% by mass, the viscosity of the polymer component contained in the first layer is increased and the extrusion processability is deteriorated, so that there is a possibility that the inner liner cannot be made thin. On the other hand, if the content of the rubber component exceeds 95% by mass, the air barrier property of the inner liner may be reduced. The content of the rubber component is preferably 70% by mass or more and 90% by mass or less in the polymer component constituting the first layer from the viewpoints of unvulcanized tackiness and vulcanized adhesiveness.

(sulfur)
It is preferable that the 1st layer which comprises an inner liner contains sulfur. As sulfur, sulfur generally used in the rubber industry during vulcanization can be used. Of these, insoluble sulfur is preferably used. Here, the insoluble sulfur refers to sulfur obtained by heating and quenching natural sulfur S ₈ to increase the molecular weight so that S _x (x = 100,000 to 300,000) is obtained. By using insoluble sulfur, blooming that normally occurs when sulfur is used as a rubber vulcanizing agent can be prevented.

  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 contained in the first layer. 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 first layer increases, and when the first layer is used for 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 1st layer used for the inner liner which constitutes the pneumatic tire of the present invention can contain additives, such as stearic acid, zinc oxide, antiaging agent, 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 component constituting the first layer is lowered, and the breaking 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 first layer becomes high, and when the first layer is used for the inner liner, the durability performance of the pneumatic tire 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 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 polymer 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 polymer composition increases, and the durability performance of the pneumatic tire may decrease when the first layer is used for the inner liner. . Furthermore, the raw material cost for producing the first layer increases. The content of the vulcanization accelerator is further preferably 0.3 parts by mass or more and 4 parts by mass or less.

(Inner liner manufacturing method)
An inner liner having a single-layer structure composed of only the first layer can be manufactured, for example, by the following method. First, 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 components, sulfur and various additives are dynamically cross-linked as required. Pellets of the composition constituting the layer are obtained. The obtained pellets are put into a T-die extruder to obtain a first layer having a desired thickness.

  In the twin screw extruder, SIBS, which is a thermoplastic resin composition, 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 the twin-screw extruder, the matrix phase of the system is composed of a thermoplastic resin component, so that the shear viscosity of the entire system is low and extrusion processing is possible.

  In the pellet of the composition constituting the dynamically cross-linked first layer obtained by the twin screw extruder, the rubber component is cross-linked, but the thermoplastic resin component of the matrix phase retains the plasticity, and the system It plays a role in creating overall plasticity. 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 pellet of the dynamically crosslinked polymer composition is crosslinked, a pneumatic tire is produced when a pneumatic tire is manufactured by applying the first layer produced using the pellet to the inner liner. Even if heated, the material constituting the inner liner can be prevented from entering the carcass layer.

  The case where the inner liner is only the first layer has been described, but the inner liner is not limited thereto, and may be a multilayer structure including the first layer and the second layer. The structure of the inner liner in the case of a multilayer structure will be described with reference to FIG.

  As shown in FIG. 11, the inner liner 30 preferably includes a second layer 32 in addition to the first layer 31 described above. The second layer 32 is preferably made of a thermoplastic resin composition containing 0.1 to 5 parts by mass of sulfur with respect to 100 parts by mass of the thermoplastic elastomer. Here, the first layer 31 is as described above.

  The total thickness of the inner liner 30 is preferably 0.05 mm or greater and 0.6 mm or less. If the total thickness of the inner liner is less than 0.05 mm, when the raw tire applied to the inner liner is vulcanized, the inner liner may be broken by press pressure, and an air leak phenomenon may occur in the obtained tire. is there. On the other hand, if the total thickness of the inner liner exceeds 0.6 mm, the tire weight increases and the fuel efficiency performance decreases. The total thickness of the inner liner is preferably 0.05 mm or more and 0.4 mm or less. Furthermore, it is preferable that the thickness of the first layer is 0.1 mm to 0.59 mm, and the thickness of the second layer is 0.01 mm to 0.2 mm.

(Second layer)
The second layer is preferably a thermoplastic resin composition containing a thermoplastic elastomer and sulfur. By adding sulfur to the thermoplastic elastomer, the unvulcanized adhesive strength and vulcanized adhesive strength with the first layer can be improved. Furthermore, the unvulcanized adhesive strength and vulcanized adhesive strength with adjacent members such as a carcass layer and an insulation layer are also improved.

(Thermoplastic elastomer)
The thermoplastic elastomer contained in the second layer includes styrene-isoprene-styrene triblock copolymer, styrene-isobutylene diblock copolymer, styrene-butadiene-styrene triblock copolymer, styrene-isoprene / butadiene-styrene. Triblock copolymer, styrene-ethylene / butene-styrene triblock copolymer, styrene-ethylene / propylene-styrene triblock copolymer, styrene-ethylene / ethylene / propylene-styrene triblock copolymer, styrene-butadiene -At least 1 sort (s) selected from the group which consists of a butylene-styrene triblock copolymer can be used. These thermoplastic elastomers may be epoxy-modified thermoplastic elastomers having an epoxy group. Especially, it is preferable to use a styrene-isoprene-styrene triblock copolymer, a styrene-isobutylene diblock copolymer, or an epoxidized styrene-butadiene-styrene triblock copolymer. Hereinafter, the styrene-isoprene-styrene triblock copolymer, the styrene-isobutylene diblock copolymer, and the epoxidized styrene-butadiene-styrene triblock copolymer will be described.

(Styrene-isoprene-styrene triblock copolymer)
Since the isoprene block of the styrene-isoprene-styrene triblock copolymer (hereinafter also referred to as “SIS”) is a soft segment, the thermoplastic resin composition containing SIS is easily vulcanized and bonded to the rubber component. Therefore, when a thermoplastic resin composition containing SIS is used for the inner liner, the inner liner is excellent in adhesion with, for example, a carcass or an adjacent rubber forming an insulation, so that air-in can be prevented. A pneumatic tire excellent in durability can be obtained.

  The molecular weight of SIS is not particularly limited, but from the viewpoint of rubber elasticity and moldability, the weight average molecular weight by GPC method is preferably 100,000 or more and 290,000 or less. If the weight average molecular weight is less than 100,000, the tensile strength may be lowered, and if it exceeds 290,000, the extrusion processability is deteriorated.

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

  In SIS, the molar ratio of isoprene units to styrene units (isoprene units / styrene units) is preferably 90/10 to 70/30, and more preferably 86/14 to 77/23. In SIS, the degree of polymerization of each block is preferably about 500 to 5,000 for isoprene blocks and about 50 to 1,500 for styrene blocks from the viewpoint of rubber elasticity and handling.

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

  The second layer containing SIS can be obtained by a usual method of forming a sheet of thermoplastic resin or thermoplastic elastomer such as extrusion molding and calender molding after mixing SIS, sulfur and other additives with a Banbury mixer.

(Styrene-isobutylene diblock copolymer)
Since the isobutylene block of the styrene-isobutylene diblock copolymer (hereinafter also referred to as SIB) is a soft segment, the thermoplastic resin composition containing SIB is easily vulcanized and bonded to the rubber component. Therefore, when the thermoplastic resin composition containing SIB is used for the inner liner, the inner liner is excellent in adhesiveness with the adjacent rubber forming the carcass or insulation, for example, so that air-in can be prevented. A pneumatic tire excellent in durability can be obtained.

  It is preferable to use a linear SIB from the viewpoint of rubber elasticity and adhesiveness.

  The molecular weight of SIB is not particularly limited, but from the viewpoint of rubber elasticity and moldability, the weight average molecular weight by GPC method is preferably 40,000 to 120,000. If the weight average molecular weight is less than 40,000, the tensile strength may be lowered, and if it exceeds 120,000, the extrusion processability may be deteriorated.

  The content of styrene units in the SIB is preferably 10% by mass or more and 35% by mass or less from the viewpoints of tackiness, adhesiveness, and rubber elasticity.

  The SIB preferably has a molar ratio of isobutylene units to styrene units (isobutylene units / styrene units) of 90/10 to 65/35. In SIB, the degree of polymerization of each block is preferably about 300 to 3,000 for an isobutylene block and about 10 to 1,500 for a styrene block from the viewpoint of rubber elasticity and handling.

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

  In International Publication No. 2005/033035, methylcyclohexane, n-butyl chloride and cumyl chloride are added to a stirrer, cooled to -70 ° C., reacted for 2 hours, and then a large amount of methanol is added to stop the reaction. , A manufacturing method of vacuum drying at 60 ° C. to obtain SIB is disclosed.

  The second layer containing SIB can be obtained by an ordinary method of forming a sheet of thermoplastic resin or thermoplastic elastomer such as extrusion molding and calender molding after mixing SIB, sulfur and other additives with a Banbury mixer.

(Epoxidized styrene-butadiene-styrene triblock copolymer)
In the epoxidized styrene-butadiene-styrene triblock copolymer (hereinafter, epoxidized SBS), the hard segment is a polystyrene block and the soft segment is a butadiene block, and an unsaturated double bond portion contained in the butadiene block is epoxidized. It is a thermoplastic elastomer. Since the epoxidized SBS has a soft segment, the thermoplastic resin composition containing the epoxidized SBS is easily vulcanized and bonded to the rubber component. Therefore, when a thermoplastic resin composition containing epoxidized SBS is used for the inner liner, the inner liner is excellent in adhesiveness with an adjacent rubber forming a carcass or an insulation, for example, so that air-in is prevented. Thus, a pneumatic tire excellent in durability can be obtained.

  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 reinforcing effect may decrease, and if it exceeds 400,000, the viscosity of the thermoplastic resin composition may increase, such being undesirable.

  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 second layer containing the epoxidized SBS can be obtained by a usual method of forming a sheet of thermoplastic resin or thermoplastic elastomer such as extrusion molding or calender molding after mixing SIB, sulfur and other additives with a Banbury mixer. it can.

(sulfur)
Sulfur can be the same as that used for the first layer. 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 thermoplastic elastomer. 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 resin 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 thermoplastic elastomer. 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 resin 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 thermoplastic elastomer. 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 resin composition becomes high 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 thermoplastic elastomer. 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 thermoplastic elastomer. 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, if the content of the vulcanization accelerator exceeds 5 parts by mass, the hardness of the thermoplastic resin composition increases, and the durability may decrease. Furthermore, the raw material cost of the thermoplastic resin 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.

(Inner liner manufacturing method)
Such an inner liner having a multilayer structure including the first layer and the second layer can be manufactured, for example, by the following method. A 1st layer is produced as mentioned above, and also a thermoplastic resin composition is made into a sheet by extrusion molding or calendering, and a 2nd layer is produced. The first layer and the second layer are bonded together to obtain an inner liner having a two-layer structure. In addition, each pellet of the polymer composition and the thermoplastic resin composition can be produced by laminate extrusion such as laminate extrusion or coextrusion.

  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, when the raw tire is vulcanized using the inner liner, the first layer may be broken by press pressure, and an air leak phenomenon may occur in the obtained tire. There is. On the other hand, if the thickness of the first layer exceeds 0.6 mm, the tire weight increases and the fuel efficiency performance decreases. Furthermore, it is preferable that the thickness of the second layer is 0.01 mm or more and 0.3 mm or less.

  The inner liner may have a three-layer structure as shown in FIG. The inner liner 40 includes a first layer 41 made of a polymer composition containing a polymer component and sulfur, and a second layer 42 made of a thermoplastic resin composition containing a thermoplastic elastomer and sulfur. The second layer 42 includes a second a layer 42a and a second b layer 42b made of different types of thermoplastic resin compositions.

  The thickness of such an inner liner is preferably 0.05 mm or greater and 0.6 mm or less. When the thickness of the inner liner is less than 0.05 mm, when the raw tire is vulcanized using the inner liner, the inner liner may be broken by press pressure, and an air leak phenomenon may occur in the obtained tire. . On the other hand, if the thickness of the inner liner exceeds 0.6 mm, the tire weight increases and the fuel efficiency performance decreases. Furthermore, the thickness of the first layer is 0.1 mm to 0.59 mm, the thickness of the second a layer is 0.01 mm to 0.2 mm, and the thickness of the second b layer is 0.01 mm to 0.2 mm. It is preferable.

  In FIG. 12, the second layer 42 is composed of two layers of the second a layer 42a and the second b layer 42b. However, the second layer 42 is further composed of a thermoplastic resin composition like the second c layer. Three or more layers composed of objects may be included. The second c layer may be provided between the first layer and the second a layer, may be provided between the first layer and the second b layer, or between the second a layer and the second b layer. May be provided.

  The second a layer 42a and the second b layer 42b constituting the second layer are respectively an SIS layer in which the thermoplastic resin elastomer is a styrene-isoprene-styrene triblock copolymer, and the thermoplastic elastomer is a styrene-isobutylene diblock block. The SIB layer made of a polymer and the thermoplastic elastomer are selected from an epoxidized SBS layer made of an epoxidized styrene-butadiene-styrene triblock copolymer. In particular, it is preferable to use an SIS layer as the second a layer 42a and an epoxidized SBS layer as the second b layer 42b.

<Pneumatic tire manufacturing method>
The pneumatic tire of the present invention can be manufactured, for example, by the following method.

  A green tire is produced using an inner liner having a single layer structure or an inner liner having a multilayer structure. In the case of using an inner liner having a multilayer structure, it is preferable to arrange the second layer toward the outer side 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 with pressure from 150 to 180 ° C. for 3 to 50 minutes 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 inner liner having a single layer structure or a multilayer structure described above. SIBS, SIS, SIB, epoxidized SBS, and the like constituting the inner liner are thermoplastic resins. For this reason, in the process of obtaining a vulcanized tire, for example, when it is heated to 150 to 180 ° C., it becomes softened in the mold. Since the thermoplastic resin 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 resin 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 resin 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 resin 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 resin 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 bladder is hollow, a cooling medium adjusted to the cooling temperature can be introduced into the bladder after the vulcanization process is completed. As the cooling medium, one or more selected from the group consisting of air, water vapor, water, and oil can be used.

  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.

<Examples 1 to 6, Comparative Example 1: Narrow groove>
(Production of carcass layer)
In the pneumatic tires of Examples 1 to 6, narrow grooves having the shape shown in FIG. 4 or 5 were provided in the unvulcanized carcass layer adjacent to the inner liner. On the other hand, in the pneumatic tire of Comparative Example 1, a carcass layer without a narrow groove was used. The narrow groove in FIG. 4 is provided with a narrow groove from the point A of the pneumatic tire in FIG. 1 to the edge of the carcass layer. On the other hand, the narrow groove in FIG. 5 is obtained by adding a shorter narrow groove to the narrow groove in FIG. 4, and this short narrow groove is provided with a narrow groove from the point C in FIG. Is. Table 1 shows the total volume and depth of these narrow grooves.

<Examples 7 to 14: Breathable yarn>
In the pneumatic tires of Examples 7 to 14, except that a breathable yarn was used instead of the narrow groove of Examples 1 to 6 for the unvulcanized carcass layer adjacent to the inner liner. The same carcass layer as in Examples 1 to 6 was produced. Table 2 shows the total volume and the number of arrays of such breathable yarns.

<Examples 15 to 18: narrow hole>
In the pneumatic tires of Examples 15 to 18, the unvulcanized carcass layer adjacent to the inner liner was replaced with the narrow groove of Examples 1 to 6 except that a narrow hole was provided. Carcass layers similar to those in Examples 1 to 6 were produced. Table 3 shows the total area of the fine holes and the diameter of the fine holes.

(Production of inner liner)
First, as materials constituting the first layer, 60 parts by mass of IIR (ExxonMobil Corporation, product name: Exxon chlorobutyl 1066) and 40 parts by mass of styrene-isobutylene-styrene triblock copolymer (SIBS: Kaneka) Product name: Shibster SIBSTAR 102T), 3 parts by mass of stearic acid (manufactured by Kao Corporation, product name: Lunac stearate S30), and 5 parts by mass of zinc oxide (Mitsui Metal Mining Co., Ltd., product) Name: Zinc Hua 1) and 1 part by weight of anti-aging agent (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., product name: NOCRACK 6C) and 1 part by mass of a vulcanization accelerator (di-2-benzothiazolyl disulfide, manufactured by Ouchi Shinsei Chemical Co., Ltd., product name: Noxeller DM) 0.5 parts by mass of sulfur (Tsurumi Chemical Co., Ltd., product name: powdered sulfur) is blended and charged into a twin screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 200 ° C.). And kneaded at 200 rpm to form pellets. The obtained pellets were put into a T-die extruder (screw diameter: φ80 mm, L / D: 50, die grip width: 500 mm, cylinder temperature: 220 ° C., film gauge: 0.3 mm).

  Next, as a material constituting the second layer, 100 parts by mass of a styrene-isoprene-styrene triblock copolymer (SIS, manufactured by Kraton Polymer Co., Ltd., product name: D1161JP, weight average molecular weight 150,000, styrene unit content) 15 parts by mass), 3 parts by mass of stearic acid (manufactured by Kao Corporation, product name: Lunac stearate S30) and 5 parts by mass of zinc oxide (manufactured by Mitsui Mining & Smelting Co., Ltd., product name: Zinc Hua 1) And 1 part by weight of an antioxidant (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., product name: NOCRACK 6C), and 1 part by weight Vulcanization accelerator (di-2-benzothiazolyl disulfide, manufactured by Ouchi Shinsei Chemical Co., Ltd., product name: Noxeller DM) and 0.5 parts by mass of sulfur (Tsurumi Chemical Co., Ltd.) Product name: powder sulfur) and by blending, double-screw extruder (screw diameter: 50 mm diameter, L / D: 30, cylinder temperature: were placed in 200 ° C.).

  And it knead | mixed at 200 rpm and pelletized in the twin-screw extruder. The obtained pellets were put into a co-extruder (cylinder temperature: 200 ° C.), and a multi-layer inner liner composed of a first layer and a second layer was produced with a thickness of 0.3 mm by the co-extrusion method.

(Production of pneumatic tires)
A raw tire was prepared using the inner liner produced above for a pneumatic tire. The inner liner was disposed such that the first layer was disposed on the innermost side in the radial direction of the raw tire and the second layer was in contact with the carcass layer of the raw tire. The green tire was press-molded in a mold at 170 ° C. for 20 minutes to produce a 195 / 65R15 size vulcanized tire. 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.

(Evaluation results)
The test results are shown in Tables 1 to 3.

<Tire performance evaluation>
The air-in performance and the flex crack growth property of the pneumatic tires of each example and each comparative example were evaluated by the following methods.

<(A) Air-in performance>
The inside of the tire after vulcanization was inspected by appearance and evaluated according to the following criteria.
A: When the number of air-ins with a diameter of 5 mm or less per tire is 0 and the number of air-ins with a diameter exceeding 5 mm is 0 per appearance.
B: When the number of air-ins with a diameter of 5 mm or less per tire is 1 to 3 and the number of air-ins with a diameter exceeding 5 mm is zero per appearance.
C: When the number of air-ins with a diameter of 5 mm or less per tire is 4 or more and the number of air-ins with a diameter of more than 5 mm is 1 or more.

<(B) Bending crack growth test>
The pneumatic tires of the Examples and Comparative Examples prepared above were subjected to an endurance running test to evaluate whether the inner liner was cracked or peeled off. Specifically, the pneumatic tire produced above is assembled to a JIS standard rim 15 × 6JJ, the tire internal pressure is set to 150 kPa, and the internal pressure is set lower than usual, and the load is 600 kg, the speed is 100 km / h, and the traveling distance is 20,000 km. The inside of the tire after running was observed, and the number of cracks and peeling that occurred inside the tire was measured. And the crack which generate | occur | produces in the pneumatic tire of the comparative example 1 is made into a reference | standard (100), The crack growth property which generate | occur | produced in the pneumatic tire of each Example with respect to it is displayed with an index | exponent based on the following calculation formula, The result Is shown in the column of “Crack Growth Index” in Tables 1 to 3. It should be noted that the larger the value of the crack growth index, the better the crack growth resistance.

(Crack growth index) = (number of cracks in Comparative Example 1) ÷ (number of cracks in each formulation) × 100.
(Comprehensive judgment)
Table 4 shows the judgment criteria for comprehensive judgment including the above air-in performance and flex crack growth.

  As is clear from the results shown in Table 1, the pneumatic tire having a narrow groove in the carcass layer as in Examples 1 to 6 was excellent in both air-in performance and flex crack growth performance. On the other hand, the pneumatic tire which does not provide a narrow groove in the carcass layer as in Comparative Example 1 was poor in both air-in performance and flex crack growth performance. From this result, it is apparent that the air mixed between the inner liner and the carcass layer can be removed by providing a narrow groove in the carcass layer.

  As is clear from the results shown in Table 2, the pneumatic tire in which a breathable yarn was provided in the carcass layer as in Examples 7 to 14 was excellent in both air-in performance and flex crack growth performance. . On the other hand, the pneumatic tire in which the air permeable yarn is not provided in the carcass layer as in Comparative Example 1 was poor in both the air-in performance and the flex crack growth performance. From this result, it is clear that air mixed between the inner liner and the carcass layer can be removed by providing a breathable yarn in the carcass layer.

  As is clear from the results shown in Table 3, the pneumatic tire having a narrow hole in the carcass layer as in Examples 15 to 18 was excellent in both air-in performance and flex crack growth performance. On the other hand, the pneumatic tire which does not provide a narrow hole in the carcass layer as in Comparative Example 1 has poor air-in performance and flex crack growth performance. From this result, it is clear that air mixed between the inner liner and the carcass layer can be removed by providing a narrow hole in the carcass layer.

  From the above results, by providing a ventilation path on the side of the carcass layer that is in contact with the inner liner, air is less likely to be mixed into the contact surface between the carcass layer and the inner liner. It became clear that durability could be improved.

  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.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 2 tread part, 3 side wall part, 4 bead part, 5 bead core, 6 carcass layer, 7 belt layer, 8 bead apex, 9 inner liner, 14 ventilation route, 16 breathable thread, 17 penetrates Narrow hole, 20, 30, 40 Inner liner, 31, 41 1st layer, 32, 42 2nd layer, 42a 2a layer, 42b 2b layer.

Claims (19)

When molding an unvulcanized tire, an adjacent member adjacent to the inner liner has a ventilation path for releasing air on the side adjacent to the inner liner,
The adjacent member is an insulation layer made of any kind of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, or butyl rubber, or a carcass layer topped with an unvulcanized rubber sheet on the cord,
The inner liner has a single layer structure or a multilayer structure including at least a first layer,
The method for producing a pneumatic tire, wherein the first layer is made of either a styrene-isobutylene-styrene triblock copolymer or a thermoplastic elastomer containing the styrene-isobutylene-styrene triblock copolymer.   The method for manufacturing a pneumatic tire according to claim 1, wherein the ventilation path faces at least an end portion of the inner liner.   3. The pneumatic tire according to claim 2, wherein an arrangement density of the air passages facing the end portion of the inner liner is higher than an arrangement density of the air passages other than the air passage facing the end portion of the inner liner. Production method. The inner liner extends between the left and right beat parts,
The method for manufacturing a pneumatic tire according to any one of claims 1 to 3, wherein the adjacent member is disposed in the beat portion adjacent to at least an end portion of the inner liner.   The method for manufacturing a pneumatic tire according to any one of claims 1 to 4, wherein the ventilation path includes a narrow groove provided adjacent to an inner liner of the adjacent member. The method for producing a pneumatic tire according to claim 5, wherein the fine groove has a total volume per unit area of 2.0 to 30.0 mm ³ / cm ² .   The method for manufacturing a pneumatic tire according to claim 5 or 6, wherein the narrow groove has a depth of 1.0 mm or less.   The method for manufacturing a pneumatic tire according to claim 1, wherein the ventilation path is made of a breathable yarn provided adjacent to an inner liner of the adjacent member. The method for producing a pneumatic tire according to claim 8, wherein the breathable yarn has a total volume per unit area of 0.5 to 30.0 mm ³ / cm ² .   The method for producing a pneumatic tire according to claim 8 or 9, wherein the breathable yarn has an arrangement number of 10 to 100 / m per unit length.   The method for manufacturing a pneumatic tire according to claim 5, wherein the ventilation path extends to an edge of the adjacent member.   The method of manufacturing a pneumatic tire according to any one of claims 1 to 4, wherein the ventilation path includes a plurality of through holes provided adjacent to an inner liner of the adjacent member. The method for producing a pneumatic tire according to claim 12, wherein the fine hole has a total area per unit area of 0.002 to 5.0 mm ² / cm ² .   The method for manufacturing a pneumatic tire according to claim 12 or 13, wherein the narrow hole has a diameter of 1.5 mm or less.   The method for producing a pneumatic tire according to any one of claims 1 to 14, wherein the first layer is a styrene-isobutylene-styrene triblock copolymer and contains 10 to 30% by mass of styrene. The inner liner further includes a second layer including a second layer,
The second layer includes one or more SIS layers composed of a styrene-isoprene-styrene block copolymer or one or more SIB layers composed of a styrene-isobutylene block copolymer, or the styrene-isoprene-styrene block. The manufacturing method of the pneumatic tire in any one of Claims 1-14 containing the thermoplastic elastomer containing any one or both of a copolymer or the said styrene-isobutylene block copolymer.   The method for producing a pneumatic tire according to claim 16, wherein the styrene-isoprene-styrene block copolymer contained in the SIS layer has a styrene / isoprene polymerization ratio of 10/90 to 30/70.   The styrene-isobutylene block copolymer contained in the SIB layer has a weight average molecular weight of 40,000 to 120,000, and a styrene / ethylene polymerization ratio of 10/90 to 35/65. The method for producing a pneumatic tire according to claim 17.   The pneumatic tire manufactured by the manufacturing method of the pneumatic tire in any one of Claims 1-18.

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