JP2013082139A - Method for manufacturing pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a pneumatic tire in which air is prevented from remaining and the peeling of a joint of an inner liner to a carcass ply is also effectively reduced.SOLUTION: The method for manufacturing the pneumatic tire comprises: an assembling step of sticking the inner liner 2 to an unvulcanized rubber sheet 3 so that an end in a width direction of the former and that of the latter are shifted from each other in terms of position in the width direction by 50-500 mm to manufacture a laminate; a cutting step of cutting the laminate 1 to manufacture cut sheets each having a fixed length corresponding to the width of a drum; and a bonding step of bonding the cut sheet so that the end of the inner liner 2 is shifted in terms of position from that of the unvulcanized rubber sheet 3 by a fixed distance. The inner liner 2 comprises a composition containing 60-99 mass% SIBS and 0.1-50 mass% of an organized clay mineral which is based on 100 parts by mass of a thermoplastic elastomer mixture containing 1-40 parts by mass of a polyamide-based polymer having ≤70 Shore D hardness, and is a laminate having a first layer of 0.05-0.6 mm thickness and a second layer of 0.01-0.3 mm thickness.

Description

  The present invention relates to a method for manufacturing a pneumatic tire, and more particularly to a method for forming an inner liner, and includes a step of manufacturing a green tire by manufacturing a laminate of an unvulcanized rubber sheet such as a carcass ply and an inner liner. The present invention relates to a tire manufacturing method.

  In recent years, tires have been made lighter due to the strong social demand for low fuel consumption of vehicles, and among the tire components, they are placed inside the tires to reduce air leakage from the inside of the pneumatic tire to the outside. Even in air barrier layers (inner liners) that are required to be reduced in weight, there is a demand for weight reduction.

  Currently, the rubber composition for an air barrier layer improves the air permeation resistance of a tire by using a rubber compound mainly composed of butyl rubber including, for example, 70 to 100% by mass of butyl rubber and 30 to 0% by mass of natural rubber. Things have been done. In addition to butylene, the rubber compound mainly composed of butyl rubber contains about 1% by mass of isoprene, which, when combined with sulfur, vulcanization accelerator, and zinc white, enables co-crosslinking between adjacent rubber layers. I have to. 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, there is a demand for a polymer that is more excellent in air permeation resistance than butyl rubber and that can reduce the thickness of the air barrier layer.

  In forming a green tire of a pneumatic tire, as shown in FIG. 7, when the inner liner P is formed on the drum 5A, the inner liner film P2 is placed on the unvulcanized inner liner rubber P1 on the conveyor in the longitudinal direction. Both end edges in the direction are aligned and pasted in advance to form a laminated body. The inner liner film P2 of the laminated body is used as the inner surface side, and is wound around the entire circumference of the band. In general, the joint PJ is formed by overlapping at one point, and thereafter, using the stitching roller, the joint PJ of the laminate is pressed to perform air bleeding.

  In such a technique, when the inner liner film P2 and the unvulcanized inner liner rubber P1 are wound on the drum, both end edges in the longitudinal direction thereof are aligned and adhered in advance. In the overlapping joining on the drum, the thickness of the joining portion PJ formed on the circumference on the drum 5A is inevitably increased. For this reason, even if a stitching roller is applied to the joint PJ, air may remain between the joints PJ. When the residual air expands due to vulcanization molding of the raw tire, the joint PJ of the laminate P is peeled off. There was a fear.

  In addition, in this technique, the end portion of the laminated body P forms a joint portion at one place on the circumference of the drum 5A. Therefore, when peeling occurs at the joint portion of the molded inner tire liner, the adjacent carcass May cause damage to the ply.

  In the prior art, it has been proposed to use a thermoplastic elastomer for the inner liner in order to reduce the weight of the pneumatic tire. However, a material that is thinner than a butyl rubber inner liner and has high air permeation resistance is inferior to a butyl rubber inner liner in terms of vulcanization adhesion to insulation rubber and carcass ply rubber adjacent to the inner liner. It will be.

  In particular, if the adhesive strength at the joint portion of the inner liner is weak, the joint portion may be peeled off during running, and the tire internal pressure may be reduced, leading to tire bursts. Moreover, since the said joining part becomes a structure where another member is exposed to an inner surface, it becomes a path | route of an air leak and it becomes easy to produce a tire internal pressure fall.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2009-208444), an inner liner film and an unvulcanized rubber sheet are attached with both ends in the extending direction being shifted from each other, and this adhesive body is wound on a drum. A technique for forming an unvulcanized tire is disclosed.

  However, in order to shift both ends in the extending direction from each other, it is necessary to cut the members one by one and cut them one by one and attach them separately to each other, which may reduce productivity. In addition, depending on the bonding method, the accuracy may deteriorate, and air may accumulate between the films, resulting in damage during tire vulcanization.

  In Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-291256), ethylene-vinyl alcohol copolymer is in a range of 15 to 30 parts by mass with respect to 100 parts by mass of a rubber component made of natural rubber and / or synthetic rubber. A pneumatic tire provided with the contained rubber composition for an inner liner is disclosed. However, this technique is not preferable from the viewpoint of reducing the weight of the tire because the inner liner is as thick as 1 mm.

  Patent Document 3 (Japanese Patent Laid-Open No. 9-165469) discloses a nylon film used as an inner liner. Here, it is disclosed that after a nylon film is RFL-treated, a pneumatic tire is manufactured by adhering to a tire inner surface or a carcass layer with a rubber paste made of a rubber composition.

  However, this technique has a problem that the process becomes complicated. Furthermore, in the vulcanization process, vulcanization molding is generally performed by pressing against the inner surface of the mold from the inside of the unvulcanized tire housed in the mold, but since the inner liner is a nylon film, nylon is heated when the bladder is heated during vulcanization. There is a problem that the film sticks and adheres to the bladder and breaks.

JP 2009-208444 A JP 2007-291256 A JP-A-9-165469

  The present invention relates to a method for forming a tire by winding a laminated body of an inner liner and an unvulcanized rubber sheet such as a carcass ply on a molding drum, and achieving uniformity in thickness at a joint portion on the circumference of the drum. The purpose is to prevent the air from remaining and effectively reduce the peeling of the joint between the inner liner and the carcass ply. It is another object of the present invention to provide a pneumatic tire having a small crack growth rate, rolling resistance, and a low static air pressure reduction rate.

The present invention relates to a method for producing a pneumatic tire having an inner liner on the inside of the tire.
(A) an assembling step for producing a laminate by laminating the widthwise end of the inner liner and the widthwise end of the unvulcanized rubber sheet by shifting each other by 50 mm to 500 mm in the width direction;
(B) cutting the laminate to a predetermined length corresponding to the drum width to produce a cutting sheet;
(C) The cut sheet is wound around the entire circumference of the drum such that the cut surface is in the circumferential direction of the drum and the inner liner is on the inner surface side, and the end of the inner liner and the end of the unvulcanized rubber sheet Having a joining step of joining the position of the part by shifting a certain distance,
The inner liner is a polymer composition containing 100 parts by mass of a polymer mixture containing 60 to 99% by mass of a styrene-isobutylene-styrene block copolymer and 1 to 40% by mass of a styrene-maleic anhydride copolymer,
Lamination of a first layer having a thickness of 0.05 mm to 0.6 mm and a second layer having a thickness of 0.01 mm to 0.3 mm, which is disposed on the unvulcanized rubber sheet side and is made of a thermoplastic elastomer. It is related with the manufacturing method of the pneumatic tire which is a body.

  In the present invention, in the assembly process, the width of the inner liner and the width of the unvulcanized rubber sheet are different, and the laminated body is manufactured by shifting in the width direction so that both ends in the width direction do not overlap each other. be able to.

  The styrene-isobutylene-styrene triblock copolymer preferably has a styrene component content of 10 to 30% by mass. The styrene-maleic anhydride copolymer has a styrene component / maleic anhydride component molar ratio of 50/50 to 90/10, a weight average molecular weight of 4,000 to 20,000, and maleic anhydride. It is preferable to include a styrene-maleic anhydride copolymer base resin having an acid value of 50 to 600 as the acid component.

  The styrene-maleic anhydride copolymer is a styrene-maleic anhydride copolymer having a monoester group and a monocarboxylic acid group obtained by esterifying the styrene-maleic anhydride copolymer base resin. It is preferable that the ester resin is included.

  Further, the styrene-maleic anhydride copolymer preferably includes an aqueous solution of an ammonium salt of a styrene-maleic anhydride copolymer in which the styrene-maleic anhydride copolymer base resin is dissolved in an ammonium salt.

  In the present invention, an inner liner composed of a composite layer of a first layer containing a mixture of SIBS and a styrene-maleic anhydride copolymer and a second layer of a thermoplastic elastomer is shifted from the unvulcanized rubber sheet in the width direction. The laminate is wound around the drum so that the inner liner is on the inner surface, and the ends of the inner liner and the unvulcanized rubber sheet are mutually connected in the circumferential direction of the drum. By joining at a separated position, the step in thickness at the joint of the inner liner and the joint of the unvulcanized rubber sheet can be relaxed. In stitching, the air at the joints can be reliably removed, and peeling of the joints due to residual air can be reduced.

  Furthermore, since the thickness in the tire circumferential direction becomes uniform and the tire becomes close to a perfect circle, radial force variation (RFV) can be reduced and the uniformity of the tire is improved.

  In addition, the molded inner liner and the uncured rubber sheet such as the carcass ply are formed with a joint portion separated from each other in the circumferential direction. Therefore, even if peeling occurs at the joint portion of the carcass ply. Since the peeled portion is reinforced by the inner liner, damage and breakage of the product tire are alleviated.

  In particular, in the present invention, the inner liner is disposed on the inner side of the tire, the first layer having a thickness of 0.05 mm to 0.6 mm, and the unvulcanized rubber sheet is disposed, and the thickness is 0.01 mm. Since it is the composite layer of the second layer that is ˜0.3 mm, the adhesive force between the adjacent carcass ply rubber is reinforced. And the reinforcement effect by an inner liner when the junction part of a carcass ply peels becomes high, and the reinforcement effect by a carcass ply when a junction part of an inner liner peels becomes high.

It is the schematic which shows an assembly process. It is a perspective view which shows the outline of an assembly process. It is the schematic which shows a cutting process. (A) is sectional drawing of a laminated body, (b) is the schematic which shows the state which winds a laminated body around a drum. It is the schematic which shows a cutting process. (A) is sectional drawing of a laminated body, (b) is the schematic which shows the state which winds a laminated body around a drum. It is the schematic of the shaping | molding method of the conventional inner liner. It is a schematic sectional drawing of a pneumatic tire. It is a schematic sectional drawing of a polymer laminated body.

<Embodiment 1>
The present invention is a method for manufacturing a pneumatic tire provided with an inner liner on the inner side of the tire, and the manufacturing method is performed in the following green tire molding process.
(A) An assembling step in which a laminated body is manufactured by laminating the widthwise end of the inner liner and the widthwise end of the unvulcanized rubber sheet in the widthwise direction within a range of 50 mm to 500 mm.
(B) The cutting process which manufactures a cutting sheet | seat by cut | disconnecting the said laminated body to the fixed length corresponding to a drum width.
(C) The cut sheet is wound around the entire circumference of the drum such that the cut surface is in the drum circumferential direction and the inner liner is on the inner surface side, and the end of the inner liner and the end of the unvulcanized rubber sheet A joining process in which the position of the material is joined by shifting a certain distance.

Here, the manufacturing method of the pneumatic tire of this invention is demonstrated with reference to figures.
<Assembly process>
FIG. 1 is a lateral schematic view showing the assembly process, and FIG. 2 is a perspective schematic view showing the assembly process. In FIGS. 1 and 2, the film-like inner liner 2 is covered with a release paper, and is sent from the storage roll R1 through the first drive roller R2 in the direction of the arrow, and is separated from the release paper by the release rollers R3 and R4. To be separated. And the inner liner 2 is sent to a pair of calendar roll R7.

  On the other hand, the unvulcanized rubber sheet 3 is sent to the pair of calendar rolls R7 via the second drive roller R6. Here, the inner liner 2 and the unvulcanized rubber sheet 3 are bonded together to produce the laminate 1. The laminated body 1 is wound around the winding roll R8 and temporarily stored, or is continuously sent to the subsequent cutting process. Here, the inner liner 2 and the unvulcanized rubber sheet 3 having substantially the same width are used, and the positions of both ends thereof are shifted from each other, and a shift distance L is formed. .

  Here, the shifting distance L is adjusted in the range of 50 mm to 500 mm, preferably in the range of 100 mm to 300 mm. This is because when the shift distance L is smaller than 50 mm, the interval between the joint portion of the unvulcanized rubber sheet and the joint portion of the inner liner is narrowed, and adhesion failure at the joint portion is likely to occur. On the other hand, if the shifting distance L exceeds 500 mm, it is difficult to form a tire on the drum.

  The inner liner is made of a styrene-isobutylene-styrene block copolymer, is disposed on the first layer having a thickness of 0.05 mm to 0.6 mm, and the unvulcanized rubber sheet side, and is made of a thermoplastic elastomer. It is composed of a second composite layer having a thickness of 0.01 mm to 0.3 mm. The width of the inner liner is adjusted depending on the tire size.

  In the present invention, since the inner liner and the unvulcanized rubber sheet are pressure-bonded by using a roll, there is no air accumulation, and the inner liner and the unvulcanized rubber sheet can be securely adhered to each other, and are efficient and have good productivity.

<Cutting process>
FIG. 3 is a schematic perspective view showing the cutting process. The laminated body 1 is sent from a winding roll R8 to a cutting machine by a belt conveyor, or continuously sent from an assembly process. The laminate 1 is cut at a predetermined length in the longitudinal direction according to the size of the tire to produce a cut sheet 4. For cutting the laminate, a conventional technique such as knife cutting can be employed. The cutting direction of the cutting sheet 4 corresponds to the circumferential direction of the drum, and the cutting length in the longitudinal direction corresponds to the width direction of the drum 5. The length of the inner liner is appropriately adjusted depending on the tire size.

<Joint process>
Based on FIG. 4, the joining process which joins the above-mentioned cutting sheet 4 which consists of a laminated body is demonstrated. Here, FIG. 4A is a cross-sectional view of the cutting sheet 4, and FIG. 4B is a schematic view showing a method of winding the cutting sheet 4 on the drum 5. The laminate is wound so that the inner liner 2 is adjacent to the surface of the drum 5. Here, the positions where the end portions 2a, 2b of the inner liner are joined together to form a joined portion, and the positions where the end portions 3a, 3b of the unvulcanized rubber sheet are joined together to form the joined portion are Will be offset.

<Tire molding and vulcanization process>
As described above, in the joining step, a laminated body of an inner liner and an unvulcanized carcass ply is manufactured and formed into a drum shape and a cylindrical shape. After the joining process, both ends of the laminate located at both ends of the drum are rolled back around the bead cores, and the center part of the laminate made of the inner liner and the unvulcanized carcass ply is bulged and deformed while narrowing the interval between the bead cores. Let

  Along with this operation, a belt member, tread rubber or the like is attached to the central portion of the laminate, and another rubber member such as a sidewall or bead apex is also attached to form a raw tire. The green tire thus formed is put into a mold and vulcanized by a conventional method to obtain a product tire.

<Inner liner>
In the present invention, the inner liner is a polymer composition including 100 parts by mass of a polymer mixture including 60 to 99% by mass of a styrene-isobutylene-styrene block copolymer and 1 to 40% by mass of a styrene-maleic anhydride copolymer. There is a first layer having a thickness of 0.05 mm to 0.6 mm and a second layer having a thickness of 0.01 mm to 0.3 mm, which is disposed on the unvulcanized rubber sheet side and is made of a thermoplastic elastomer. It is comprised by the laminated body of.

<First layer>
The inner liner is a polymer composition including 100 parts by mass of a polymer mixture containing 60 to 99% by mass of a styrene-isobutylene-styrene block copolymer and 1 to 40% by mass of a styrene-maleic anhydride copolymer.

(SIBS)
The first layer is made of a thermoplastic elastomer composition mainly composed of a styrene-isobutylene-styrene block copolymer (SIBS). Due to the isobutylene block of SIBS, the polymer film made of SIBS has excellent air permeation resistance. Therefore, when a polymer made of SIBS is used for the inner liner, a pneumatic tire having excellent 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 a polymer film made of 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 polymer film made of SIBS to the inner liner, air permeation resistance can be secured. Therefore, it is not necessary to use a halogenated rubber having a high specific gravity such as a halogenated butyl rubber which has been used for imparting conventional air permeation resistance, and the amount used can be reduced even when used. This can reduce the weight of the tire and improve fuel efficiency.

  The molecular weight of SIBS is not particularly limited, but the weight average molecular weight by GPC measurement is preferably 50,000 to 400,000 from the viewpoints 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. From the viewpoint of improving air permeation resistance and durability, SIBS has a styrene component content in SIBS of 10 to 30% by mass, preferably 14 to 23% by mass.

  The SIBS is a copolymer in which the degree of polymerization of each block is about 10,000 to 150,000 for isobutylene from the viewpoint of rubber elasticity and handling (becomes liquid when the degree of polymerization is less than 10,000), and styrene. Then, it is preferable that it is about 5,000-30,000.

  SIBS can be obtained by a living cationic polymerization method of a general vinyl compound. For example, JP-A-62-48704 and JP-A-64-62308 disclose that living cationic polymerization of isobutylene and other vinyl compounds is possible. By using isobutylene and other compounds as vinyl compounds, It is disclosed that a polyisobutylene-based block copolymer can be produced.

(Styrene-maleic anhydride copolymer)
In this specification, the styrene-maleic anhydride copolymer (SMA) is a styrene-maleic anhydride copolymer base resin (hereinafter also referred to as “SMA base resin”), a styrene-maleic anhydride copolymer base. Ester resin of styrene-maleic anhydride copolymer having monoester group and monocarboxylic acid group obtained by esterification of resin (hereinafter also referred to as SMA ester resin) and styrene-maleic anhydride copolymer base It describes as a concept containing the aqueous solution of ammonium salt of styrene-maleic anhydride copolymer (henceforth "SMA resin ammonium salt aqueous solution") which resin melt | dissolved in ammonium salt.

  Styrene-maleic anhydride copolymer (SMA) is used as a polymer surfactant and a high-functional cross-linking agent in dispersion and emulsification, and has excellent vulcanization adhesion to rubber. Moreover, since the wettability is given to rubber, the adhesive effect is also excellent.

  In the polymer component of the polymer composition for the inner liner, the SMA content is 0.5 to 40% by mass. When the SMA content is 0.5% by mass or more, an inner liner having excellent adhesiveness with the second layer can be obtained. Moreover, when the SMA content is 40% by mass or less, an inner liner having excellent air permeation resistance and durability can be obtained. As for content of SMA in a polymer component, 2-30 mass% is more preferable.

(Styrene-maleic anhydride copolymer-based resin)
In one embodiment of the present invention, the SMA preferably contains an SMA base resin from the viewpoints of unvulcanized tackiness and post-vulcanized adhesion.

  The SMA base resin preferably has a styrene component / maleic anhydride component molar ratio of 50/50 to 90/10 from the viewpoints of a high softening point and high thermal stability. The SMA base resin preferably has a weight average molecular weight of 4,000 to 20,000 from the viewpoint of adhesion after vulcanization and fluidity. Furthermore, the weight average molecular weight is more preferably 5,000 to 15,000.

  In the SMA base resin, the maleic anhydride component in the styrene-maleic anhydride copolymer preferably has an acid value of 50 to 600 from the viewpoint of unvulcanized adhesiveness. Furthermore, the acid value of the maleic anhydride component is more preferably 95 to 500.

(Ester resin of styrene-maleic anhydride copolymer)
In one embodiment of the present invention, the styrene-maleic anhydride copolymer is obtained by esterifying a styrene-c maleic anhydride copolymer base resin and having a monoester group and a monocarboxylic acid group. It preferably contains an ester resin of maleic anhydride copolymer (hereinafter also referred to as SMA ester resin).

  The SMA ester resin has the property of being excellent in vulcanization adhesion. Therefore, the polymer composition for inner liners excellent in vulcanization adhesiveness with the rubber layer can be obtained by blending SMA ester resin with SIBS. The SMA ester resin preferably has a styrene component / maleic anhydride component molar ratio of 50/50 to 90/10 from the viewpoint of vulcanization adhesion.

  The SMA ester resin preferably has a weight average molecular weight of 5,000 to 12,000 from the viewpoint of adhesion after vulcanization and fluidity. Furthermore, the weight average molecular weight is more preferably 6,000 to 11,000. In the SMA ester resin, the maleic anhydride component preferably has an acid value of 50 to 400 from the viewpoint of adhesion to unvulcanized rubber. Furthermore, the acid value of the maleic anhydride component is more preferably 95 to 290.

  The SMA ester resin can be produced, for example, by introducing a base resin and alcohol into a reaction vessel and heating and stirring in an inert gas atmosphere.

(Styrene-maleic anhydride copolymer ammonium salt aqueous solution)
In one embodiment of the present invention, the styrene-maleic anhydride copolymer is a styrene-maleic anhydride copolymer aqueous ammonium salt solution (hereinafter also referred to as an SMA ammonium salt aqueous solution) in which an SMA base resin is dissolved in an ammonium salt. It is preferable to contain.

  The SMA ammonium salt aqueous solution has a property of excellent wettability. Therefore, the polymer composition for inner liners excellent in adhesiveness can be obtained by mix | blending SMA ammonium salt aqueous solution with SIBS.

  The SMA ammonium salt aqueous solution preferably has a solid content of 10.0 to 45.0% from the viewpoint of adhesion to unvulcanized rubber and molding processability. The aqueous SMA ammonium salt solution preferably has a pH of 8.0 to 9.5 from the viewpoint of tackiness. An aqueous SMA ammonium salt solution causes exothermic reaction when water is added to a reaction vessel, base resin is added with vigorous stirring, and ammonium hydroxide is gradually added. Then, it can manufacture by heating to predetermined temperature and continuing stirring until melt | dissolution is completed.

(Polymer composition additive)
In the polymer composition, other reinforcing agents, vulcanizing agents, vulcanization accelerators, various oils, anti-aging agents, softeners, plasticizers, coupling agents, etc. are added to tire or general polymer compositions. Various compounding agents and additives can be blended.

(Thickness of the first layer)
The thickness of the first layer made of SIBS is 0.05 to 0.6 mm. If the thickness of the first layer is less than 0.05 mm, the first layer may be broken by the press pressure during vulcanization of a green tire in which the polymer laminate is applied to the inner liner, and an air leak phenomenon may occur in the tire. is there. 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.

  The first layer can be obtained by forming SIBS into a film by an ordinary method of forming a thermoplastic resin or thermoplastic elastomer into a film, such as extrusion molding or calendar molding.

<Second layer>
In the present invention, the second layer is composed of a thermoplastic elastomer, in particular, a styrenic thermoplastic elastomer composition. Here, the styrene thermoplastic elastomer refers to a copolymer containing a styrene block as a hard segment. For example, styrene-isoprene-styrene block copolymer (hereinafter also referred to as “SIS”), styrene-isobutylene block copolymer (hereinafter also referred to as “SIB”), styrene-butadiene-styrene block copolymer ( Hereinafter, also referred to as “SBS”), styrene-isobutylene-styrene block copolymer (hereinafter also referred to as “SIBS”), styrene-ethylene-butene-styrene block copolymer (hereinafter also referred to as “SEBS”). ), Styrene-ethylene / propylene-styrene block copolymer (hereinafter also referred to as “SEPS”), styrene-ethylene / ethylene / propylene / styrene block copolymer (hereinafter also referred to as “SEEPS”), styrene-. Butadiene / butylene-styrene block copolymer (hereinafter referred to as “SBB”) Also referred to as ".) There is.

  The styrenic thermoplastic elastomer may have an epoxy group in its molecular structure. For example, Epofriend A1020 manufactured by Daicel Chemical Industries, Ltd. (weight average molecular weight is 100,000, epoxy equivalent is 500). An epoxy-modified styrene-butadiene-styrene copolymer (epoxidized SBS) can be used.

  Of the styrenic thermoplastic elastomers used in the second layer, SIS and SIB are particularly suitable. Since the isoprene block of SIS is a soft segment, a polymer film made of SIS is easily vulcanized and bonded to a rubber component. Therefore, when a polymer film made of SIS is used for the inner liner, the inner liner is excellent in adhesiveness with, for example, the rubber layer of the carcass ply, so that a pneumatic tire excellent in durability can be obtained.

  The molecular weight of the SIS is not particularly limited, but from the viewpoint of rubber elasticity and moldability, the weight average molecular weight by GPC measurement is preferably 100,000 to 290,000. 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 the styrene component in the SIS is preferably 10 to 30% by mass from the viewpoints of tackiness, adhesiveness, and rubber elasticity.

  In the present invention, the polymerization degree of each block in SIS is preferably about 500 to 5,000 for isoprene and about 50 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

  The SIS can be obtained by a general vinyl compound polymerization method, for example, a living cationic polymerization method. The SIS layer can be obtained by forming the SIS into a film by a usual method of forming a thermoplastic resin or a thermoplastic elastomer into a film such as extrusion molding or calendar molding.

  Since the isobutylene block of the styrene-isobutylene block copolymer (SIB) is a soft segment, the polymer film made of SIB is easily vulcanized and bonded to the rubber component. Therefore, when a polymer film made of SIB is used as an inner liner, the inner liner is excellent in adhesiveness with an adjacent rubber forming a carcass or an insulation, for example, so that a pneumatic tire excellent in durability is obtained. be able to.

  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 measurement 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 the styrene component in the SIB is preferably 10 to 35% by mass from the viewpoints of tackiness, adhesiveness, and rubber elasticity.

  In the present invention, the polymerization degree of each block in SIB is preferably about 300 to 3,000 for isobutylene and about 10 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

  The SIB can be obtained by a living polymerization method of a general vinyl compound. For example, methylcyclohexane, n-butyl chloride, and cumyl chloride are added to a stirrer, cooled to -70 ° C, and reacted for 2 hours. Thereafter, a large amount of methanol is added to stop the reaction, and vacuum drying at 60 ° C. can produce SIB.

  The SIB layer can be formed by a usual method of forming SIB into a film of a styrenic thermoplastic elastomer such as extrusion molding or calendar molding. The thickness of the second layer is preferably 0.01 mm to 0.3 mm. If the thickness of the second layer is less than 0.01 mm, the second layer may be broken by the press pressure during vulcanization of the raw tire in which the polymer laminate is applied to the inner liner, 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 further preferably 0.05 to 0.2 mm.

<Polymer laminate>
In the present invention, a polymer laminate composed of a composite layer of a first layer and a second layer is used as the inner liner. Here, the first layer and the second layer are thermoplastic elastomer compositions and are in a softened state in a mold at a vulcanization temperature, for example, 150 ° C. to 180 ° C. The softened state means an intermediate state between solid and liquid with improved molecular mobility. Further, when the thermoplastic elastomer composition is in a softened state, the reactivity is improved as compared with the solid state, and therefore, the thermoplastic elastomer composition adheres and adheres to an adjacent member. Therefore, in order to prevent the shape change of the thermoplastic elastomer, the adhesion with the adjacent member, and the fusion, a cooling step is required when manufacturing the tire. A cooling process cools the inside of a bladder part rapidly for 10 to 300 seconds after tire vulcanization to 50-120 ° C. As the cooling medium, at least one selected from air, water vapor, water and oil is used. By adopting such a cooling step, it is possible to form a thin inner liner having an inner liner in the range of 0.05 to 0.6 mm.

<Embodiment 2>
In Embodiment 2, the width W2 of the inner liner 2 is formed wider than the width W1 of the unvulcanized rubber sheet 3.

<Cutting process>
FIG. 5 is a schematic view showing a cutting process. The laminated body 1 is sent from the winding roll R8 to the cutting machine by a belt conveyor, or continuously sent from the assembly process. The laminate 1 is cut to a predetermined length in the longitudinal direction according to the size of the tire to produce a cut sheet 4. Note that conventional techniques such as knife cutting can be employed for cutting the laminate. The cutting direction of the cutting sheet 4 corresponds to the circumferential direction of the drum, while the cutting length in the longitudinal direction corresponds to the width direction of the drum 5.

<Joint process>
6A is a cross-sectional view of the laminate, and FIG. 6B is a schematic view showing a state in which the laminate is wound around a drum. Here, the inner liner 2 is wound on the drum 5 so as to be in contact with each other, and both ends 2a and 2b are overlapped to form a joint portion. An unvulcanized rubber piece 6 is used to join the both ends 3a, 3b of the unvulcanized rubber sheet 3 such as insulation onto it. In this case, two joint portions are formed, but are offset from the joint portion position with the inner liner.

<Tire structure>
A pneumatic tire provided with an inner liner inside the tire according to the present invention will be described with reference to FIG. FIG. 8 is a schematic cross-sectional view of the right half of the pneumatic tire. The pneumatic tire 11 includes a tread portion 12 and sidewall portions 13 and bead portions 14 so as to form a toroid shape from both ends of the tread portion. Further, a bead core 15 is embedded in the bead portion 14. Further, a carcass ply 16 provided from one bead portion 14 to the other bead portion and wrapped around the bead core 15 at both ends, and at least two on the outer side of the crown portion of the carcass ply 16. A belt layer 17 made of a ply is arranged.

  The belt layer 17 usually intersects two plies made of steel cords or cords such as aramid fibers with respect to the tire circumferential direction so that the cords are usually at an angle of 5 to 30 °. Are arranged as follows. In addition, a topping rubber layer can be provided on both outer sides of the belt layer to reduce peeling at both ends of the belt layer. In the carcass ply, organic fiber cords such as polyester, nylon, and aramid are arranged at approximately 90 ° in the tire circumferential direction. In the region surrounded by the carcass ply and the folded portion, the bead core 15 extends from the upper end to the sidewall direction. An extending bead apex 18 is arranged. An inner liner 19 extending from one bead portion 14 to the other bead portion 14 is disposed on the inner side in the tire radial direction of the carcass ply 16.

  Next, FIG. 9 shows the arrangement state of the inner liner with the carcass ply in the vulcanized tire. In FIG. 9, the polymer laminate PL is composed of a first layer PL1 and a second layer PL2. When the polymer laminate PL is applied to an inner liner of a pneumatic tire, if the second layer PL2 is installed facing the outer side in the tire radial direction so as to be in contact with the carcass ply C, the second layer PL2 is used in the tire vulcanization process. And carcass C can be increased in adhesive strength. The obtained pneumatic tire has excellent air permeation resistance and bending crack growth resistance because the inner liner and the rubber layer of the carcass ply C are well bonded.

<Pneumatic tire manufacturing method>
The manufacturing method of the pneumatic tire of this invention can use the conventional manufacturing method. An inner liner is manufactured using the polymer laminate PL. The inner tire is applied to the raw tire of the pneumatic tire 11 and vulcanized and molded together with other members. When the polymer laminate PL is arranged on the green tire, the second layer PL2 of the polymer laminate PL is arranged outward in the tire radial direction so as to be in contact with the carcass ply C. When arranged in this manner, the adhesive strength between the second layer PL2 and the carcass 6 can be increased in the tire vulcanization step. The obtained pneumatic tire has excellent air permeation resistance and bending crack growth resistance because the inner liner and the rubber layer of the carcass ply C are well bonded.

<Manufacture of inner liner>
According to the formulation shown in Tables 1 and 2, various compounding agents were put into a twin screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 220 ° C.) to be pelletized. The sheet was extruded using an extruder (screw diameter: φ80 mm, L / D: 50, die gap width: 40 mm, cylinder temperature: 220 ° C.) at a screw rotation speed of 80 RPM and an extrusion speed of about 9 m / min.

(Note 1) IIR: “Exon Chlorobutyl 1068” manufactured by ExxonMobil Corporation.
(Note 2) SIBS: “Sibstar SIBSTAR 102T” manufactured by Kaneka Corporation (Shore A hardness 25, styrene content: 25 mass%).
(Note 3) SMA base resin: “SMA1000” manufactured by Sartomer (styrene component / maleic anhydride component: 50/50, weight average molecular weight: 5,500, acid value of maleic anhydride: 490).
(Note 4) SMA ester resin: “SMA1440” manufactured by Sartomer (styrene component / maleic anhydride component: 80/20, weight average molecular weight: 7,000, acid value of maleic anhydride: 200).
(Note 5) SMA ammonium salt aqueous solution: “SMA1000H” (pH 9.0) manufactured by Sartomer.
(Note 6) Carbon: “Seast V” (N660, N ₂ SA: 27 m ² / g) manufactured by Tokai Carbon Co., Ltd.
(Note 7) Stearic acid: “Lunac stearate S30” manufactured by Kao Corporation.
(Note 8) Zinc oxide: “Zinc Hana 1” manufactured by Mitsui Kinzoku Mining Co., Ltd.
(Note 9) Anti-aging agent: “NOCRACK 6C” (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 10) Vulcanization accelerator: “Noxeller DM” (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 11) Sulfur: “Powdered sulfur” manufactured by Tsurumi Chemical Co., Ltd.
(Note 12) SIS: D1161JP manufactured by Kraton Polymer Co., Ltd. (styrene component content 15 mass%, weight average molecular weight: 150,000).
(Note 13) SIB.

  To a 2 L reaction vessel equipped with a stirrer, 589 mL of methylcyclohexane (dried with molecular sieves), 613 ml of n-butyl chloride (dried with molecular sieves), and 0.550 g of cumyl chloride were added. After cooling the reaction vessel to −70 ° C., 0.35 mL of α-picoline (2-methylpyridine) and 179 mL of isobutylene were added. Further, 9.4 mL of titanium tetrachloride was added to initiate polymerization, and the reaction was allowed to proceed for 2.0 hours while stirring the solution at -70 ° C. Next, 59 mL of styrene was added to the reaction vessel, and the reaction was continued for another 60 minutes, and then a large amount of methanol was added to stop the reaction. After removing the solvent and the like from the reaction solution, the polymer was dissolved in toluene and washed twice with water. The toluene solution was added to a methanol mixture to precipitate a polymer, and the obtained polymer was dried at 60 ° C. for 24 hours to obtain a styrene-isobutylene diblock copolymer.

Styrene component content: 15% by mass
Weight average molecular weight: 70,000
<Unvulcanized rubber sheet>
In the present invention, a carcass ply is used for the unvulcanized rubber sheet, and the composition of the topping rubber is as follows.

<Composition A of topping rubber>
Natural rubber (Note 1) 100 parts by weight Carbon black (Note 2) 50 parts by weight Zinc flower (Note 3) 3 parts by weight Anti-aging agent (Note 4) 0.2 parts by weight Sulfur (Note 5) 1 part by weight Agent (Note 6) 1 part by mass Vulcanization aid (Note 7) 1 part by mass (Note 1) TSR20
(Note 2) “Seast V” manufactured by Tokai Carbon Co., Ltd. (N660, N ₂ SA: 27 m ² / g)
(Note 3) Zinc oxide (ZnO): “Zinc Hana 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
(Note 4) “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 5) “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
(Note 6) “Noxeller DM” manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 7) Stearic acid: “Karnaku Lunac S30” manufactured by Kao Corporation
<Manufacture of pneumatic tires>
The pneumatic tire according to the present invention was manufactured based on the above-described assembly process, cutting process, and joining process. For details, as shown in Table 1, pneumatic tires of comparative examples and examples were manufactured. Vulcanization was press molded at 170 ° C. for 20 minutes, cooled at 100 ° C. for 3 minutes without being taken out from the vulcanization mold, taken out from the vulcanized tire, and 195 / 65R15 size having the basic structure shown in FIG. Manufactured.

  In each of the examples, the inner liner is 1300 mm based on FIG. 5, and the shift distance (amount) L is changed to 50 mm, 500 mm, and 250 mm by changing the dimensions of the carcass ply.

  Examples 1 to 3 are examples in which 0.5 parts by mass of SMA base resin is blended with SIBS in the first layer, and Examples 4 to 6 are examples in which 20 parts by mass of SMA base resin are blended with SIBS in the first layer. is there. Examples 7 to 9 are examples in which 0.5 parts by mass of SMA base resin and SMA ester resin are mixed with SIBS in the first layer, and Examples 10 to 12 are SMA base resin and SMA in SIBS in the first layer. This is an example in which 0.5 parts by mass of each ammonium aqueous solution is blended.

  Comparative Example 1 is an example in which IIR is used for the first layer, and Comparative Examples 2 to 4 are examples in which 0.5% by mass of SMA base resin is mixed with IIR in the first layer. Comparative Example 5 is an example in which only SIBS is used in the first layer, and Comparative Examples 6 and 7 are examples in which 50% by mass of SMA is mixed with SIBS in the first layer.

  All of the examples of the present invention are excellent in air-in performance, flex crack growth property, rolling resistance and static air drop rate, and in uniform performance.

<Performance test>
The pneumatic tire manufactured as described above was evaluated for performance by the following method.

<Air-in performance>
The inside of the tire after vulcanization was inspected by appearance and the evaluation was as follows.

A: When the number of air-ins having a diameter of 5 mm or less per tire is 0 and the number of air-ins exceeding the diameter of 5 mm is 0 B: The appearance is 5 mm or less per tire. When the number of air-ins is 1 to 3 and the number of air-ins exceeding 5 mm in diameter is 0 C: From the appearance, the number of air-ins with a diameter of 5 mm or less per tire is 4 or more and the diameter is 5 mm When the number of air-ins exceeding 1 is one or more <Bend crack growth test>
The flex crack growth test was evaluated based on whether the inner liner was cracked or peeled off. The prototype tire is assembled to a JIS standard rim 15 × 6 JJ, the tire internal pressure is set to 150 KPa, which is lower than usual, the load is 600 kg, the speed is 100 km / h, the traveling distance is 20,000 km, the inside of the tire is observed, cracks, The number of peels was measured. Based on Comparative Example 1, the crack growth property of each Example and Comparative Example was expressed as an index based on the following formula. The larger the number, the smaller the flex crack growth.

Flex crack growth index = (number of cracks in comparative example 1) / (number of cracks in each example) × 100
<Rolling resistance index>
Using a rolling resistance tester manufactured by Kobe Steel Co., Ltd., the prototype tire was assembled to a JIS standard rim 15 × 6JJ, and the temperature was set to room temperature (30 ° C.) under conditions of a load of 3.4 kN, an air pressure of 230 kPa, and a speed of 80 km / h. And rolling resistance was measured. And based on the following formula, the comparative example 1 was made into the reference | standard 100, and rolling resistance change rate (%) of the Example was displayed by the index | exponent. It shows that rolling resistance is reduced, so that rolling resistance change rate is large.

Rolling resistance index = (Rolling resistance of Comparative Example 1) / (Rolling resistance of Example) × 100
<Static air pressure reduction rate>
The prototype tire is assembled to a JIS standard rim 15 × 6 JJ, filled with an initial air pressure of 300 kPa, and left at room temperature for 90 days to calculate the rate of decrease in air pressure. A smaller numerical value is preferable because the air pressure is less likely to decrease.

<Uniformity index>
The radial force variation (RFV) was measured using a tire uniformity tester in accordance with JASOC 607: 2000 “Method for testing uniformity of automobile tires”. Relative values with Comparative Example 1 as 100 were displayed as an index. The larger the index, the better the uniformity. The measurement conditions were 8.0 × 17 for the rim, 60 rpm for the tire rotation speed, 200 kPa for the air pressure, and 4000 kN for the longitudinal load.

<Comprehensive judgment>
Judgment A means that all of the following conditions are satisfied.

(B) Bending crack growth index is 100 or more (c) Rolling resistance change rate is 100 or more (d) Static air pressure decrease rate (% / month) is 2.6 or less The case where any one of the following conditions is satisfied. In the case of multiple determinations, the lower evaluation was adopted.

(A) Air-in evaluation is B or C evaluation (b) Flexural crack growth index is less than 100 (c) Rolling resistance change rate is lower than 100 (d) Static air pressure decrease rate (% / month) is 2.7 or more

  The pneumatic tire manufacturing method of the present invention can be applied to a manufacturing method of pneumatic tires for trucks, buses, heavy machinery, etc. in addition to pneumatic tires for passenger cars.

  DESCRIPTION OF SYMBOLS 1 Laminated body, 2 Inner liner, 3 Unvulcanized rubber sheet, 4 Cutting sheet, 5 Drum, L Shift distance (amount), 11 Pneumatic tire, 12 Tread part, 13 Side wall part, 14 Bead part, 15 Bead core, 16 carcass plies, 17 belt layers, 18 bead apex, 19 inner liner, PL polymer laminate, PL1 first layer, PL2 second layer.

Reference Examples 1, 2 and 3 are examples in which 0.5 parts by mass of SMA base resin is blended with SIBS of the first layer, Reference Examples 3, 4 and Example 6 are SMA base resins with SIBS of the first layer. Is 20 parts by mass. Reference Examples 5 and 6 and Example 9 are examples in which 0.5 parts by mass of SMA base resin and SMA ester resin are mixed with SIBS of the first layer, Reference Examples 7 and 8, and Example 12 are the first layer. This is an example in which 0.5 parts by mass of SMA base resin and SMA ammonium aqueous solution are mixed with SIBS.

Claims (6)

In the manufacturing method of a pneumatic tire provided with an inner liner on the inside of the tire,
(A) an assembling step for producing a laminate by laminating the widthwise end of the inner liner and the widthwise end of the unvulcanized rubber sheet by shifting each other by 50 mm to 500 mm in the width direction;
(B) cutting the laminate to a predetermined length corresponding to the drum width to produce a cutting sheet;
(C) The cut sheet is wound around the entire circumference of the drum such that the cut surface is in the circumferential direction of the drum and the inner liner is on the inner surface side, and the end of the inner liner and the end of the unvulcanized rubber sheet Having a joining step of joining the position of the part by shifting a certain distance,
The inner liner is a polymer composition containing 100 parts by mass of a polymer mixture containing 60 to 99% by mass of a styrene-isobutylene-styrene block copolymer and 1 to 40% by mass of a styrene-maleic anhydride copolymer,
Lamination of a first layer having a thickness of 0.05 mm to 0.6 mm and a second layer having a thickness of 0.01 mm to 0.3 mm, which is disposed on the unvulcanized rubber sheet side and is made of a thermoplastic elastomer. The manufacturing method of the said pneumatic tire which is a body.   The width of the inner liner and the width of the unvulcanized rubber sheet are different in the assembling step, and the laminate is manufactured by shifting in the width direction so that both ends in the width direction do not overlap each other. A method of manufacturing a pneumatic tire.   The method for producing a pneumatic tire according to claim 1 or 2, wherein the styrene-isobutylene-styrene triblock copolymer has a styrene component content of 10 to 30% by mass.   The styrene-maleic anhydride copolymer has a styrene component / maleic anhydride component molar ratio of 50/50 to 90/10, a weight average molecular weight of 4,000 to 20,000, and maleic anhydride. The manufacturing method of the pneumatic tire in any one of Claims 1-3 containing the styrene-maleic anhydride copolymer base resin whose acid value of a component is 50-600.   The styrene-maleic anhydride copolymer is a styrene-maleic anhydride copolymer having a monoester group and a monocarboxylic acid group obtained by esterifying the styrene-maleic anhydride copolymer base resin. The manufacturing method of the pneumatic tire in any one of Claims 1-4 containing ester resin.   The styrene-maleic anhydride copolymer includes an aqueous styrene-maleic anhydride copolymer ammonium salt solution in which the styrene-maleic anhydride copolymer base resin is dissolved in an ammonium salt. A method for producing a pneumatic tire according to claim 1.

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